WorldWideScience

Sample records for martensitic steel f82h

  1. Thermal aging behavior of low activation martensitic steel F82 H

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, K.; Jitsukaw, S. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States)

    2007-07-01

    Full text of publication follows: Low activation ferritic/martensitic (LAF/M) steel is the primary candidate materials for a fusion reactor structural material. Characterization of F82H conducted in the IEA working group on ferritic/martensitic steels has generated many property data on this steel and many irradiation data have been also obtained. Thermal aging behavior is an important property of the structural material to be used in high-temperature environment. And it is also important to distinguish the irradiation accelerated or irradiation induced precipitation effects from irradiation results. Therefore, thermal aging behavior of F82H IEA heat was investigated in this study. Microstructure, precipitation analysis, and mechanical properties of F82H IEA heat steel (8Cr-2WVTa) after thermal aging at 450, 500, 550, 600, and 650 deg. C for 1,000, 10,000, and 30,000 hours were examined. Hardness, tensile, and Charpy impact tests were performed as mechanical property tests before and after aging. 650 deg. C aging started softening after 1000 hours and embrittlement due to Laves phase raised 70 deg. C in ductile-to-brittle transfer temperature (DBTT) and decreased upper-shelf energy (USE) to 70% of as-received material. The aging below 600 deg. C did not show much effect on the tensile properties. Especially, no change in tensile properties was observed below 500 deg. C. 550 and 600 deg. C aging showed changes in Charpy impact properties after 3000 hours, and longer aging time increases the DBTT and decreases the USE. These changes in Charpy properties were corresponding to the growth of Laves phase precipitation. (authors)

  2. Corrosion fatigue studies on F82H mod. martensitic steel in reducing water coolant environments

    Energy Technology Data Exchange (ETDEWEB)

    Maday, M.F.; Masci, A. [ENEA, Casaccia (Italy). Centro Ricerche Energia

    1998-03-01

    Load-controlled low cycle fatigue tests have been carried out on F82H martensitic steel in 240degC oxygen-free water with and without dissolved hydrogen, in order to simulate realistic coolant boundary conditions to be approached in DEMO. It was found that water independently of its hydrogen content, determined the same fatigue life reduction compared to the base-line air results. Water cracks exhibited in their first propagation stages similar fracture morphologies which were completely missing on the air cracks, and were attributed to the action of an environment related component. Lowering frequency gave rise to an increase in F82H fatigue lifetimes without any change in cracking mode in air, and to fatigue life reduction by microvoid coalescence alone in water. The data were discussed in terms of (i) frequency dependent concurrent processes for crack initiation and (ii) frequency-dependent competitive mechanisms for crack propagation induced by cathodic hydrogen from F82H corrosion. (author)

  3. Influence of traps on the deuterium behaviour in the low activation martensitic steels F82H and Batman

    Science.gov (United States)

    Serra, E.; Perujo, A.; Benamati, G.

    1997-06-01

    A time dependent permeation method is used to measure the permeability, diffusivity and solubility of deuterium in the low activation martensitic steels F82H and Batman. The measurements cover the temperature range from 373 to 743 K which includes the onset of deuterium trapping effects on diffusivity and solubility. The results are interpreted using a trapping model. The number of trap sites and their average energies for deuterium in F82H and Batman steels are determined.

  4. Influence of traps on the deuterium behaviour in the low activation martensitic steels F82H and Batman

    Energy Technology Data Exchange (ETDEWEB)

    Serra, E. [Commission of the European Communities, Ispra (Italy). Joint Research Centre; Perujo, A. [Commission of the European Communities, Ispra (Italy). Joint Research Centre; Benamati, G. [Associazione ENEA-EURATOM sulla FUSIONE, CR Brasimone, 40032 Camungnano Bologna (Italy)

    1997-06-01

    A time dependent permeation method is used to measure the permeability, diffusivity and solubility of deuterium in the low activation martensitic steels F82H and Batman. The measurements cover the temperature range from 373 to 743 K which includes the onset of deuterium trapping effects on diffusivity and solubility. The results are interpreted using a trapping model. The number of trap sites and their average energies for deuterium in F82H and Batman steels are determined. (orig.).

  5. Development of an extensive database of mechanical and physical properties for reduced-activation martensitic steel F82H

    Energy Technology Data Exchange (ETDEWEB)

    Jitsukawa, S. E-mail: jitsukawa@ifmif.tokai.jaeri.go.jp; Tamura, M.; Schaaf, B. van der; Klueh, R.L.; Alamo, A.; Petersen, C.; Schirra, M.; Spaetig, P.; Odette, G.R.; Tavassoli, A.A.; Shiba, K.; Kohyama, A.; Kimura, A

    2002-12-01

    Tensile, fracture toughness, creep and fatigue properties and microstructural studies of the reduced-activation martensitic steel F82H (8Cr-2W-0.04Ta-0.1C) before and after irradiation are reported. The design concept used for the development of this alloy is also introduced. A large number of collaborative test results including those generated under the International Energy Agency (IEA) implementing agreements are collected and are used to evaluate the feasibility of using reduced-activation martensitic steels for fusion reactor structural materials, with F82H as one of the reference alloys. All the specimens used in these tests were prepared from plates obtained from 5-ton heats of F82H supplied to all participating laboratories by JAERI. Many of the results have been entered into relational databases with emphasis on traceability of records on how the specimens were prepared from plates and ingots.

  6. Fracture toughness of the IEA heat of F82H ferritic/martensitic stainless steel as a function of loading mode

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huaxin; Gelles, D.S. [Pacific Northwest Labs., Richland, WA (United States); Hirth, J.P. [Washington State Univ., Pullman, WA (United States)] [and others

    1997-04-01

    Mode I and mixed-mode I/III fracture toughness tests were performed for the IEA heat of the reduced activation ferritic/martensitic stainless steel F82H at ambient temperature in order to provide comparison with previous measurements on a small heat given a different heat treatment. The results showed that heat to heat variations and heat treatment had negligible consequences on Mode I fracture toughness, but behavior during mixed-mode testing showed unexpected instabilities.

  7. Creep behavior of reduced activation martensitic steel F82H injected with a large amount of helium

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, N. E-mail: yamamoto.norikazu@nims.go.jp; Murase, Y.; Nagakawa, J.; Shiba, K

    2002-12-01

    Creep response against DEMO reactor level helium was examined on F82H steel, a candidate structural material for advanced fusion systems. Helium was injected into the material at 823 K to a concentration of about 1000 appm utilizing {alpha}-particle irradiation with a cyclotron. Post-injection creep rupture tests were conducted at the same temperature. It has been demonstrated that helium brought about no significant effect on a variety of creep properties (lifetime, rupture elongation and minimum creep rate). In parallel with this, it did not cause any influence on fracture appearance. Both helium implanted and unimplanted samples were failed in a completely transcrystalline and ductile fashion. No symptom of helium induced grain boundary separation was thereby observed even after high concentration helium introduction. These facts hint a fairly good resistance of this material toward high temperature helium embrittlement even for long-time service in fusion reactors.

  8. Irradiation response in weldment and HIP joint of reduced activation ferritic/martensitic steel, F82H

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, Takanori [Japan Atomic Energy Agency (JAEA); Sokolov, Mikhail A [ORNL; Ando, M. [Japan Atomic Energy Agency (JAEA); Tanigawa, H. [Japan Atomic Energy Agency (JAEA); Shiba, K. [Japan Atomic Energy Agency (JAEA); Stoller, Roger E [ORNL; Odette, G.R. [University of California, Santa Barbara

    2013-11-01

    This work investigates irradiation response in the joints of F82H employed for a fusion breeding blanket. The joints, which were prepared using welding and diffusion welding, were irradiated up to 6 dpa in the High Flux Isotope Reactor at the Oak Ridge National Laboratory. Post-irradiation tests revealed hardening in weldment (WM) and base metal (BM) greater than 300 MPa. However, the heat affected zones (HAZ) exhibit about half that of WM and BM. Therefore, neutron irradiation decreased the strength of the HAZ, leaving it in danger of local deformation in this region. Further the hardening in WM made with an electron beam was larger than that in WM made with tungsten inert gas welding. However the mechanical properties of the diffusion-welded joint were very similar to those of BM even after the irradiation.

  9. Irradiation response in weldment and HIP joint of reduced activation ferritic/martensitic steel, F82H

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, T., E-mail: hirose.takanori@jaea.go.jp [Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Sokolov, M.A. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Ando, M.; Tanigawa, H.; Shiba, K. [Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Stoller, R.E. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Odette, G.R. [University of California Santa Barbara, Santa Barbara, CA (United States)

    2013-11-15

    This work investigates irradiation response in the joints of F82H employed for a fusion breeding blanket. The joints, which were prepared using welding and diffusion welding, were irradiated up to 6 dpa in the High Flux Isotope Reactor at the Oak Ridge National Laboratory. Post-irradiation tests revealed hardening in weldment (WM) and base metal (BM) greater than 300 MPa. However, the heat affected zones (HAZ) exhibit about half that of WM and BM. Therefore, neutron irradiation decreased the strength of the HAZ, leaving it in danger of local deformation in this region. Further the hardening in WM made with an electron beam was larger than that in WM made with tungsten inert gas welding. However the mechanical properties of the diffusion-welded joint were very similar to those of BM even after the irradiation.

  10. Microstructural study of irradiated isotopically tailored F82H steel

    Energy Technology Data Exchange (ETDEWEB)

    Wakai, E. E-mail: wakai@realab01.tokai.jaeri.go.jp; Miwa, Y.; Hashimoto, N.; Robertson, J.P.; Klueh, R.L.; Shiba, K.; Abiko, K.; Furuno, S.; Jitsukawa, S

    2002-12-01

    The synergistic effect of displacement damage and hydrogen or helium atoms on microstructures in F82H steel irradiated at 250-400 deg. C to 2.8-51 dpa in HFIR has been examined using isotopes of {sup 54}Fe or {sup 10}B. Hydrogen atoms increased slightly the formation of dislocation loops and changed the Burgers vector for some parts of dislocation loops, and they also affected on the formation of cavity at 250 deg. C to 2.8 dpa. Helium atoms also influenced them at around 300 deg. C, and the effect of helium atoms was enhanced at 400 deg. C. Furthermore, the relations between microstructures and radiation-hardening or ductile to brittle transition temperature (DBTT) shift in F82H steel were discussed. The cause of the shift increase of DBTT is thought to be due to the hardening of dislocation loops and the formation of {alpha}{sup '}-precipitates on dislocation loops.

  11. Microstructural evolution of HFIR-irradiated low activation F82H and F82H-{sup 10}B steels

    Energy Technology Data Exchange (ETDEWEB)

    Wakai, E.; Shiba, K.; Sawai, T. [Japan Atomic Energy Research Inst. (Japan); Hashimoto, N.; Robertson, J.P.; Klueh, R.L. [Oak Ridge National Lab., TN (United States)

    1998-03-01

    Microstructures of reduced-activation F82H (8Cr-2W-0.2V-0.04Ta) and the F82H steels doped with {sup 10}B, irradiated at 250 and 300 C to 3 and 57 dpa in the High Flux Isotope Reactor (HFIR), were examined by TEM. In the F82H irradiated at 250 C to 3 dpa, dislocation loops, small unidentified defect clusters with a high number density, and a few MC precipitates were observed in the matrix. The defect microstructure after 300 C irradiation to 57 dpa is dominated by the loops, and the number density of loops was lower than that of the F82H-{sup 10}B steel. Cavities were observed in the F82H-{sup 10}B steels, but the swelling value is insignificant. Small particles of M{sub 6}C formed on the M{sub 23}C{sub 6} carbides that were present in both steels before the irradiation at 300 C to 57 dpa. A low number density of MC precipitate particles formed in the matrix during irradiation at 300 C to 57 dpa.

  12. Friction stir welding of F82H steel for fusion applications

    Science.gov (United States)

    Noh, Sanghoon; Ando, Masami; Tanigawa, Hiroyasu; Fujii, Hidetoshi; Kimura, Akihiko

    2016-09-01

    In the present study, friction stir welding was employed to join F82H steels and develop a potential joining technique for a reduced activation ferritic/martensitic steel. The microstructures and mechanical properties on the joint region were investigated to evaluate the applicability of friction stir welding. F82H steel sheets were successfully butt-joined with various welding parameters. In welding conditions, 100 rpm and 100 mm/min, the stirred zone represented a comparable hardness distribution with a base metal. Stirred zone induced by 100 rpm reserved uniformly distributed precipitates and very fine ferritic grains, whereas the base metal showed a typical tempered martensite with precipitates on the prior austenite grain boundary and lath boundary. Although the tensile strength was decreased at 550 °C, the stirred zone treated at 100 rpm showed comparable tensile behavior with base metal up to 500 °C. Therefore, friction stir welding is considered a potential welding method to preserve the precipitates of F82H steel.

  13. Fatigue performance and cyclic softening of F82H, a ferritic martensic steel

    Energy Technology Data Exchange (ETDEWEB)

    Stubbins, J.F. [Univ. of Illinois, Urbana, IL (United States); Gelles, D.S. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1996-04-01

    The room temperature fatigue performance of F82H has been examined. The fatigue life was determined in a series of strain-controlled tests where the stress level was monitored as a function of the number of accrued cycles. Fatigue lives in the range of 10{sup 3} to 10{sup 6} cycles to failure were examined. The fatigue performance was found to be controlled primarily by the elastic strain range over most of the range of fatigue lives examined. Only at low fatigue lives did the plastic strain range contribute to the response. However, when the significant plastic strain did contribute, the material showed a tendency to cyclically soften. That is the load carrying capability of the material degrades with accumulated fatigue cycles. The overall fatigue performance of the F82H alloy was found to be similiar to other advanced martensitic steels, but lower than more common low alloy steels which possess lower yield strengths.

  14. Effects of heat treatment and irradiation on mechanical properties in F82H steel doped with boron and nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, N. [Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki-ken 319-1195 (Japan)]. E-mail: okubo.nariaki@jaea.go.jp; Wakai, E. [Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Matsukawa, S. [Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Sawai, T. [Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Kitazawa, S. [Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Jitsukawa, S. [Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki-ken 319-1195 (Japan)

    2007-08-01

    Effects of heat treatment and irradiation on mechanical properties and microstructures have been studied for martensitic steel F82H co-doped with 60 ppm B and 200 ppm N (F82H + B + N) to evaluate fundamental mechanical properties and irradiation response before irradiation at JMTR and HFIR facilities. The specimens were firstly normalized at 1150 {sup o}C and tempered at 700 {sup o}C, secondly normalized at 1000 {sup o}C and tempered at 700, 750 and 780 {sup o}C. The tensile properties were measured for the specimens before irradiation. Single ion irradiations of 10.5 MeV Fe{sup 3+} and dual ion irradiations of 10.5 MeV Fe{sup 3+} with simultaneous 1.05 MeV He{sup +} of 10 appmHe/dpa rate were performed at 160-590 {sup o}C to 20 dpa. Micro-hardness was measured before and after the irradiation. Tensile properties of the F82H + B + N were similar to F82H and also radiation hardening behaved similarly to F82H. The change of hardening increased with increasing temperature, saturated around 350 {sup o}C and decreased at higher temperature.

  15. Microstructural evolutions of friction stir welded F82H steel for fusion applications

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Sang Hoon; Shim, Jae Won; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Tani Gawa, Hiro Yasu [JAEA, Rokasho (Japan); Fujii, Hideto Shi [Osaka Univ., Osaka (Japan); Kim Ura, Aki Hiko [Kyoto Univ., Kyoto (Japan)

    2012-10-15

    A blanket is the most important component functionalized as plasma confining, tritium breeding, heat exchanging, and irradiation shielding from severe thermo neutron loads in a fusion reactor. Its structure consists of first walls, side walls, a back board, and coolant channels mainly made of reduced activation ferritic/martensitic (RAFM) steel, which is the most promising candidate as a structural material for fusion reactors. To fabricate this blanket structure, some welding and joining methods have being carefully applied. However, when fusion welding, such as tungsten inert gas (TIG) welding, electron beam, and laser welding was performed between F82H and itself, the strength of welds significantly deteriorated due to the development of {delta} ferrite and precipitate dissolution. Post welding heat treatment (PWHT) should be followed to restore the initial microstructure. Nevertheless, microstructural discontinuity inevitably occurs between the weld metal, heat affected zone and base metal and this seriously degrades the entire structural stability under pulsed operation at high temperature in test blanket module (TBM). A phase transformation can also be an issue to be solved, which leads to a difficult replacement of the blanket module. Therefore, a reliable and field applicable joining technique should be developed not to accompany with PWHT after the joining process. Friction stir welding (FSW) is one of the solid state processes that does not create a molten zone at the joining area, so the degradation of the featured microstructures may be avoided or minimized. In this study, FSW was employed to join F82H steels to develop a potential joining technique for RAFM steel. The microstructural features on the joint region were investigated to evaluate the applicability of the FSW.

  16. The dose dependence of fracture toughness Of F82H steel

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, M. [Oak Ridge National Laboratory, Materials Science and Technology Div., TN (United States); Tanigawa, H.; Ando, M.; Shiba, K. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Odette, G. [UCSB, Santa-Barbara, Dept. of Mechanical Engineering UCSB, AK (United States); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States)

    2007-07-01

    Full text of publication follows: The ferritic-martensitic steel F82H is a primary candidate low-activation material for fusion applications, and it is being investigated in the joint U.S. Department of Energy-Japan Atomic Energy Agency. As a part of this program, several capsules containing fracture toughness specimens were irradiated in High-Flux Isotope Reactor. These specimens were irradiated to a wide range of doses from 3.5 to 25 dpa. The range of irradiation temperature was from 250 deg. C to 500 deg. C. This paper summarizes the changes in fracture toughness transition temperature and decrease in the ductile fracture toughness as result of various irradiation conditions. It is shown that in the 3.5 to 25 dpa dose range, irradiation temperature plays the key rote in determination of the shift of the transition temperature. Highest embrittlement observed at 250 deg.C and the lowest at 500 deg. C. At a given irradiation temperature, shift of the fracture toughness transition temperature increases slightly with dose within the studied dose range. It appears that main gain in transition temperature shift occurred during initial {approx}5 dpa of irradiation. The present data are compared to the available published trends. (authors)

  17. Underwater explosive welding of tungsten to reduced-activation ferritic steel F82H

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Daichi [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kasada, Ryuta, E-mail: r-kasada@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Konishi, Satoshi [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Morizono, Yasuhiro [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Hokamoto, Kazuyuki [Institute of Pulsed Power Science, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan)

    2014-10-15

    Highlights: • The underwater explosive welding was successfully applied in the joining of tungsten to F82H reduced activation ferritic steel. • Microstructure of the interface showed the formation of a wave-like interface with a thin mixed layer of tungsten and F82H. • Nanoindentation hardness results exhibited a gradual change away from the welded interface without hardened layer. • Small punch tests on the welded specimens resulted in the cracking at a center of tungsten followed by the interfacial cracking. - Abstract: The present study reports the underwater explosive welding of commercially pure tungsten onto the surface of a reduced-activation ferritic steel F82H plate. Cross-sectional observation revealed the formation of a wave-like interface, consisting of a thin mixed layer of W and F82H. The results of nanoindentation hardness testing identified a gradual progressive change in the interface, with no hardened or brittle layer being observed. Small punch tests on the welded specimens resulted in cracking at the center of the tungsten, followed by crack propagation toward both the tungsten surface and the tungsten/steel interface.

  18. Investigations of void formation in neutron irradiated iron and F82H steel

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Singh, Bachu Narain

    2002-01-01

    In the present work pure iron and low activation steel F82H have been neutron irradiated at temperatures in the interval 50 deg.C - 350 deg.C to a dose of 0.23 dpa (displacements per atom). The formation of defects has been investigated by the use ofpositron annihilation spectroscopy (PAS......). In addition iron has been irradiated to different doses in the range 0.01 - 0.4 dpa at 50oC and 100oC and the dose dependence of the electrical conductivity determined. The results demonstrated that theformation of voids takes place during neutron irradiation of pure iron in the whole temperature range....... For irradiation temperatures of 50 deg.C and 100 deg.C also a high density of micro-voids was observed. Voids and micro-voids were also detected in lowactivation F82H steel for a low irradiation temperature (50 deg.C), while for irradiation close to the temperature of annealing stage V (250 deg.C), no voids...

  19. Evaluation of grain boundary embrittlement of phosphorus added F82H steel by SSTT

    Science.gov (United States)

    Kim, Byung Jun; Kasada, Ryuta; Kimura, Akihiko; Tanigawa, Hiroyasu

    2012-02-01

    Non-hardening embrittlement (NHE) can be happened by a large amount of He on grain boundaries over 500-700 appm of bulk He without hardening at fusion reactor condition. Especially, at high irradiation temperatures (>≈420 °C), NHE accompanied by intergranular fracture affects the severe accident and the safety of fusion blanket system. Small specimen tests to evaluate fracture toughness and Charpy impact properties were carried out for F82H steels with different levels of phosphorous addition in order to simulate the effects of NHE on the shift of transition curve. It was found that the ductile to brittle transition temperature (DBTT) and reference temperature ( T0) after phosphorous addition is shifted to higher temperatures and accompanied by intergranular fracture at transition temperatures region. The master curve approach for evaluation of fracture toughness change by the degradation of grain boundary strength was carried out by referring to the ASTM E1921.

  20. Creep strength and microstructure of F82H steels near tempering temperature

    Science.gov (United States)

    Shinozuka, K.; Esaka, H.; Sakasegawa, H.; Tanigawa, H.

    2015-09-01

    Creep rupture tests near the tempering temperature were performed, and the creep behavior at high temperatures and the structures of fracture specimens were investigated. Three kinds of F82H test specimens were used: IEA-heat, mod.3, and BA07. The time-to-rupture of the BA07 specimens was the longest under all the test conditions. This was because the minimum creep rates of BA07 were smallest, and a large quantity of fine precipitates of MX from the ESR treatment were considered to be effective in providing creep resistance. Although mod.3 specimens showed a high creep resistance under high stress, the time-to-rupture of mod.3 and IEA-heat were almost the same at low stress. This was because the fine tempered martensitic structure was weakened by being subjected to a high temperature for a long period. Therefore, it is considered that a large quantity of fine MX precipitates are effective for creep resistance near the tempering temperature.

  1. Creep strength and microstructure of F82H steels near tempering temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shinozuka, K., E-mail: kshinozu@nda.ac.jp [National Defense Academy, Yokosuka, Kanagawa 239-8686 (Japan); Esaka, H. [National Defense Academy, Yokosuka, Kanagawa 239-8686 (Japan); Sakasegawa, H.; Tanigawa, H. [Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212 (Japan)

    2015-09-15

    Creep rupture tests near the tempering temperature were performed, and the creep behavior at high temperatures and the structures of fracture specimens were investigated. Three kinds of F82H test specimens were used: IEA-heat, mod.3, and BA07. The time-to-rupture of the BA07 specimens was the longest under all the test conditions. This was because the minimum creep rates of BA07 were smallest, and a large quantity of fine precipitates of MX from the ESR treatment were considered to be effective in providing creep resistance. Although mod.3 specimens showed a high creep resistance under high stress, the time-to-rupture of mod.3 and IEA-heat were almost the same at low stress. This was because the fine tempered martensitic structure was weakened by being subjected to a high temperature for a long period. Therefore, it is considered that a large quantity of fine MX precipitates are effective for creep resistance near the tempering temperature.

  2. Application of master curve method to the evaluation of fracture toughness of F82H steels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung Jun, E-mail: kim.byungjun@jaea.go.jp [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1106 (Japan); Kasada, Ryuta; Kimura, Akihiko [Institute of Advanced Energy, Kyoto University, Kyoto (Japan); Wakai, Eiichi; Tanigawa, Hiroyasu [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1106 (Japan)

    2013-11-15

    Fracture toughness data was obtained for reduced-activation ferritic (RAF) steels with different sizes of specimens (1 compact tension(CT), 1/2 CT and 1/4 CT) using the master curve (MC) method in the transition temperature region. Considering the size adjustment by ASTM E1921, effects of specimen size on the fracture toughness are not observed and the reference temperature (T{sub 0}) is around 164 K which is similar to those (154 K) of other previous studies. However, the data are not well represented by a MC, showing a rather large number of data below the lower boundary curve. Our proposed new MC was derived within the framework of the ASTM E1921 standard to apply the MC method to F82H steel. This new MC analysis can be applied to RAF steels to estimate T{sub 0} with a better description of the data scatter in the transition temperature region of fracture toughness than that of the conventional MC analysis.

  3. Effect of boron on post irradiation tensile properties of reduced activation ferritic steel (F-82H) irradiated in HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, Kiyoyuki; Suzuki, Masahide; Hishinuma, Akimichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of Materials Science and Engineering; Pawel, J.E. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1994-12-31

    Reduced activation ferritic/martensitic steel, F-82H (Fe-8Cr-2W-V-Ta), was irradiated in the High Flux Isotope Reactor (HFIR) to doses between 11 and 34 dpa at 400 and 500 C. Post irradiation tensile tests were performed at the nominal irradiation temperature in vacuum. Some specimens included {sup 10}B or natural boron (nB) to estimate the helium effect on tensile properties. Tensile properties including the 0.2% offset yield stress, the ultimate tensile strength, the uniform elongation and the total elongation were measured. The tensile properties were not dependent on helium content in specimens irradiated to 34 dpa, however {sup 10}B-doped specimens with the highest levels of helium showed slightly higher yield strength and less ductility than boron-free specimens. Strength appears to go through a peak, and ductility through a trough at about 11 dpa. The irradiation to more than 21 dpa reduced the strength and increased the elongation to the unirradiated levels. Ferritic steels are one of the candidate alloys for nuclear fusion reactors because of their good thermophysical properties, their superior swelling resistance, and the low corrosion rate in contact with potential breeder and coolant materials.

  4. Effect of post-weld heat treatment and neutron irradiation on a dissimilar-metal joint between F82H steel and 316L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Haiying, E-mail: haigirl1983@gmail.com [SOKENDAI - The Graduated University for Advanced Studies, Toki (Japan); Nagasaka, Takuya [SOKENDAI - The Graduated University for Advanced Studies, Toki (Japan); National Institute for Fusion Science, Toki (Japan); Kometani, Nobuyuki [Nagoya University, Nagoya (Japan); Muroga, Takeo [SOKENDAI - The Graduated University for Advanced Studies, Toki (Japan); National Institute for Fusion Science, Toki (Japan); Guan, Wenhai; Nogami, Shuhei; Yabuuchi, Kiyohiro; Iwata, Takuya; Hasegawa, Akira [Tohoku University, Sendai (Japan); Yamazaki, Masanori [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University (Japan); Kano, Sho; Satoh, Yuhki; Abe, Hiroaki [Institute for Materials Research, Tohoku University, Sendai (Japan); Tanigawa, Hiroyasu [Japan Atomic Energy Agency, Rokkasho (Japan)

    2015-10-15

    Highlights: • Significant hardening after neutron irradiation at 300 °C for 0.1 dpa was found in the fine-grain HAZ of F82H for the dissimilar-metal joint between F82H and 316L. • The possible hardening mechanism was explained from the viewpoint of carbon behavior. • However, the significant hardening did not degrade the impact property significantly. - Abstract: A dissimilar-metal joint between F82H steel and 316L stainless steel was fabricated by using electron beam welding (EBW). By microstructural analysis and hardness test, the heat-affected zone (HAZ) of F82H was classified into interlayer area, fine-grain area, and coarse-carbide area. Post-weld heat treatment (PWHT) was applied to control the hardness of HAZ. After PWHT at 680 °C for 1 h, neutron irradiation at 300 °C with a dose of 0.1 dpa was carried out for the joint in Belgian Reactor II (BR-II). Compared to the base metals (BMs) and weld metal (WM), significant irradiation hardening up to 450HV was found in the fine-grain HAZ of F82H. However, the impact property of F82H-HAZ specimens, which was machined with the root of the V-notch at HAZ of F82H, was not deteriorated obviously in spite of the significant irradiation hardening.

  5. Tensile properties of F82H steel after aging at 400–650 °C for 100,000 h

    Energy Technology Data Exchange (ETDEWEB)

    Nagasaka, Takuya, E-mail: nagasaka@nifs.ac.jp [National Institute for Fusion Science, Toki (Japan); Sakasegawa, Hideo; Tanigawa, Hiroyasu; Ando, Masami [Japan Atomic Energy Agency, Rokkasho (Japan); Tanaka, Teruya; Muroga, Takeo; Sagara, Akio [National Institute for Fusion Science, Toki (Japan)

    2015-10-15

    Highlights: • The present study investigated tensile properties of F82H steel after aging at 400–650 °C for 100,000 h. • Although tensile strength was degraded during the aging, the degradation of yield strength and ultimate tensile strength was 50 MPa or less at 550 °C and below in both room temperature and high temperature tests. • Above 550 °C, yield strength and ultimate tensile strength decreased with increasing aging temperature. • On the other hand, no degradation of ductility was detected after the aging. • The mechanisms for the degradation of tensile strength due to the long-term aging are discussed with previous results obtained by extraction residue analyses. - Abstract: The present study investigated tensile properties of F82H steel after aging at 400–650 °C for 100,000 h (100 kh), and discusses the mechanisms for change in tensile properties due to the long-term aging. Tensile strength was degraded during the aging. The degradation of yield strength and ultimate tensile strength was 50 MPa or less at 550 °C and below in both room temperature and high temperature tests. Above 550 °C, yield strength and ultimate tensile strength decreased with increasing aging temperature. On the other hand, no degradation of ductility was detected after the aging. Most of the degradation of the tensile strength could be attributed to loss of solid solution hardening by W due to precipitation of Laves phase (Fe{sub 2}W) at 550 °C. However, other mechanisms, such as coarsening of martensite structure and recovery of dislocations, should be taken into account to explain additional degradation above 550 °C.

  6. Creep behavior of the F82H steel under irradiation with 17 MeV protons at 300 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Nagakawa, Johsei [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga Koen, Kasuga, Fukuoka 816-8580 (Japan)], E-mail: NAGAKAWA.Johsei@nims.go.jp; Uchio, S. [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga Koen, Kasuga, Fukuoka 816-8580 (Japan); Murase, Y.; Yamamoto, N. [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Shiba, K. [Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai-Mura, Ibaraki-Ken 319-1195 (Japan)

    2009-04-30

    Although fusion blankets are exposed to severe irradiation, its rear side would stay at rather a modest condition. In this research, the irradiation-induced deformation of F82H IEA-heat steel at 300 deg. C was examined. A torsion creep apparatus with a strain resolution of {approx}10{sup -7} was used with 17 MeV protons (2 x 10{sup -7} dpa/s). At the lowest stress of 30 MPa, deformation in the direction against applied stress was observed. This 'negative creep' was attributed to the increase in elastic modulus due to irradiation. Such an effect was compensated for each measurement based on the modulus data measured during irradiation. Stress exponent n of irradiation creep rates was 1.5, very close to that of creep strain at 5 dpa of pressurized tubes. The predicted stress relaxation was slower than that for 5% cold-worked Type 316L steel, resulting mainly from the difference in n, smaller and closer to unity in the latter.

  7. Corrosion behavior of F82H exposed to high temperature pressurized water with a rotating apparatus

    Science.gov (United States)

    Kanai, A.; Kasada, R.; Nakajima, M.; Hirose, T.; Tanigawa, H.; Enoeda, M.; Konishi, S.

    2014-12-01

    The present study reports the corrosion behavior of a reduced-activation ferritic martensitic steel F82H exposed to high temperature pressurized water for 28 and 100 h using a rotating disk apparatus at rotation speeds of 500 and 1000 rpm at a temperature of 573 K under a water pressure of 15 MPa with corrosion and/or flow-accelerated corrosion of F82H under the rotating condition.

  8. Saturation behavior of irradiation hardening in F82H irradiated in the HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Shiba, K.; Tanigawa, H.; Ando, M. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Klueh, R.L. [Oak Ridge National Laboratory, TN (United States); Stoller, R. [ORNL - Oak Ridge National Laboratory, Materials Science and Technology Div., Oak Ridge, AK TN (United States)

    2007-07-01

    Full text of publication follows: Post irradiation tensile tests on reduced activation ferritic/martensitic steel, F82H have been conducted over the past two decades using Japan Materials Testing Reactor (JMTR) of JAEA, and Fast Flux Testing Facility (FFTF) of PNNL and High Flux Isotope Reactor (HFIR) of ORNL, USA, under Japan/US collaboration programs. According to these results, F82H does not demonstrate irradiation hardening above 673 K up to 60 dpa. The current study has been concentrated on hardening behavior at temperature around 573 K. A series of low temperature irradiation experiment has been conducted at the HFIR under the international collaborative research between JAEA/US-DOE. In this collaboration, the irradiation condition is precisely controlled by the well matured capsule designing and instrumentation. This paper summarizes recent results of the irradiation experiments focused on F82H and its modified steels compared with the irradiation properties database on F82H. Post irradiation tensile tests have been conducted on the F82H and its modified steels irradiated at 573 K and the dose level was up to 25 dpa. According to these results, irradiation hardening of F82H is saturated by 9 dpa and the as-irradiated 0.2 % proof stress is less than 1 GPa at ambient temperature. The deterioration of total elongation was also saturated by 9 dpa irradiation. The ductility of some modified steels which showed larger total elongation than that of F82H before irradiation become the same level as that of standard F82H steel after irradiation, even though its magnitude of irradiation hardening is smaller than that of F82H. This suggests that the more ductile steel demonstrates the more ductility loss at this temperature, regardless to the hardening level. The difference in ductility loss behavior between various tensile specimens will be discussed as the ductility could depend on the specimen dimension. (authors)

  9. Dependence of precipitate formation on normalizing temperature and its impact on the heat treatment of F82H-BA07 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Fukumoto, K., E-mail: fukumoto@u-fukui.ac.jp [Research Institute for Nuclear Engineering, University of Fukui, Tsuruga 914-0055 (Japan); Sakaguchi, T.; Inoue, K. [Graduate School of Nuclear Power and Energy Safety Engineering, University of Fukui, Fukui 910-8507 (Japan); Itoh, T. [Faculty of Engineering, University of Fukui, Fukui 910-8507 (Japan); Sakasegawa, H.; Tanigawa, H. [JAEA-Aomori, Rokkasho 039-3212 (Japan)

    2013-11-15

    A detailed study of the microstructural evolution during heat treatment of F82H steel at different temperatures has been carried out. By increasing the normalizing temperature from 1193 K to 1333 K, the residual austenitic and packet grain sizes increased. The chromium-enriched precipitate, M{sub 23}C{sub 6}, increased with the normalizing temperature. Tiny vanadium-rich precipitates, of the MX type, were formed on the grain boundaries when the normalizing temperature remained below 1223 K. Above 1223 K, the proportion of vanadium-enriched precipitate decreased significantly. With a two-step normalizing heat treatment, tiny tantalum- and vanadium-rich precipitates remained on the grain boundaries and within grains when the normalizing temperature of the second step remained below 1223 K. It suggested that the second-step heat treatment in a two-step normalizing heat treatment above 1223 K influenced the tantalum- and vanadium-rich MX precipitate formation in F82H steel.

  10. Material properties of the F82H melted in an electric arc furnace

    Energy Technology Data Exchange (ETDEWEB)

    Sakasegawa, Hideo, E-mail: sakasegawa.hideo@jaea.go.jp [Japan Atomic Energy Agency, Rokkasho, Aomori (Japan); Tanigawa, Hiroyasu [Japan Atomic Energy Agency, Rokkasho, Aomori (Japan); Kano, Sho; Abe, Hiroaki [Institute for Materials Research, Tohoku university, Sendai, Miyagi (Japan)

    2015-10-15

    Highlights: • We studied material properties of reduced activation ferritic/martensitic steel. • We melted F82H using a 20 tons electric arc furnace for the first time. • Mass effect likely affected material properties. • MX (M: Metal, C: Carbon and/or Nitrogen) precipitates mainly formed on grain and sub grain boundaries. - Abstract: Fusion DEMO reactor requires over 11,000 tons of reduced activation ferritic/martensitic steel. It is necessary to develop the manufacturing technology for fabricating such large-scale steel with appropriate mechanical properties. In this work, we focused fundamental mechanical properties and microstructures of F82H-BA12 heat which was melted using a 20 tons electric arc furnace followed by electroslag remelting process. Its raw material of iron was blast furnace iron, because the production volume of electrolytic iron which has been used in former heats, is limited. After melting and forging, this F82H-BA12 heat was heat-treated in four different conditions to consider their fluctuations and to optimize them, and tensile and Charpy impact tests were then performed. The result of these mechanical properties were comparable to those of former F82H heats less than 5 tons which were melted applying vacuum induction melting.

  11. Reduced activation martensitic steels as a structural material for ITER test blanket

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, K. E-mail: shiba@realab01.tokai.jaeri.go.jp; Enoeda, M.; Jitsukawa, S

    2004-08-01

    A Japanese ITER test blanket module (TBM) is planed to use reduced-activation martensitic steel F82H. Feasibility of F82H for ITER test blanket module is discussed in this paper. Several kinds of property data, including physical properties, magnetic properties, mechanical properties and neutron-irradiation data on F82H have been obtained, and these data are complied into a database to be used for the designing of the ITER TBM. Currently obtained data suggests F82H will not have serious problems for ITER TBM. Optimization of F82H improves the induced activity, toughness and HIP resistance. Furthermore, modified F82H is resistant to temperature instability during material production.

  12. Embrittlement of irradiated F82H in the absence of irradiation hardening

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee (United States)], E-mail: kluehrl@ornl.gov; Shiba, K. [Japan Atomic Energy Agency, Toki-Mura, Ibaraki (Japan); Sokolov, M.A. [Oak Ridge National Laboratory, Oak Ridge, Tennessee (United States)

    2009-04-30

    Neutron irradiation of 7-12% Cr ferritic/martensitic steels below 425-450 deg. C produces microstructural defects and precipitation that cause an increase in yield stress. This irradiation hardening causes embrittlement, which is observed in a Charpy impact or fracture toughness test as an increase in the ductile-brittle transition temperature. Based on observations that show little change in strength in steels irradiated above 425-450 deg. C, the general conclusion has been that no embrittlement occurs above these temperatures. In a recent study of F82H steel, significant embrittlement was observed after irradiation at 500 deg. C, but no hardening occurred. This embrittlement is apparently due to irradiation-accelerated Laves-phase precipitation. Observations of the embrittlement of F82H in the absence of irradiation hardening have been examined and analyzed with thermal-aging studies and computational thermodynamics calculations to illuminate and understand the embrittlement during irradiation.

  13. Determination of hydrogen diffusion coefficients in F82H by hydrogen depth profiling with a tritium imaging plate technique

    Energy Technology Data Exchange (ETDEWEB)

    Higaki, M.; Otsuka, T.; Hashizume, K. [Interdisciplinary Graduate School of Engineering and Sciences, Kyushu University, Kasuga, Fukuoka (Japan); Tokunaga, K. [Research Institute of Applied Mechanics, Kyushu University, Kasuga, Fukuoka (Japan); Ezato, K.; Suzuki, S.; Enoeda, M.; Akiba, M. [Japan Atomic Energy Agency - JAEA, Naka, Ibaraki (Japan)

    2015-03-15

    Hydrogen diffusion coefficients in a reduced activation ferritic/martensitic steel (F82H) and an oxide dispersion strengthened F82H (ODS-F82H) have been determined from depth profiles of plasma-loaded hydrogen with a tritium imaging plate technique (TIPT) in the temperature range from 298 K to 523 K. Data on hydrogen diffusion coefficients, D, in F82H, are summarized as D [m{sup 2}*s{sup -1}] =1.1*10{sup -7}exp(-16[kJ mol{sup -1}]/RT). The present data indicate almost no trapping effect on hydrogen diffusion due to an excess entry of energetic hydrogen by the plasma loading, which results in saturation of the trapping sites at the surface and even in the bulk. In the case of ODS-F82H, data of hydrogen diffusion coefficients are summarized as D [m{sup 2}*s{sup -1}] =2.2*10{sup -7}exp(-30[kJ mol{sup -1}]/RT) indicating a remarkable trapping effect on hydrogen diffusion caused by tiny oxide particles (Y{sub 2}O{sub 3}) in the bulk of F82H. Such oxide particles introduced in the bulk may play an effective role not only on enhancement of mechanical strength but also on suppression of hydrogen penetration by plasma loading.

  14. Mechanical properties of TIG and EB weld joints of F82H

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, Takanori, E-mail: hirose.takanori@jaea.go.jp; Sakasegawa, Hideo; Nakajima, Motoki; Tanigawa, Hiroyasu

    2015-10-15

    Highlights: • Narrow groove TIG minimized volume of F82H weld. • Mechanical properties of TIG and EB welds of F82H have been characterized. • Post weld heat treatment successfully moderate the toughness of weld metal without softening the base metal. - Abstract: This work investigates mechanical properties of weld joints of a reduced activation ferritic/martensitic steel, F82H and effects of post weld heat treatment on the welds. Vickers hardness, tensile and Charpy impact tests were conducted on F82H weld joints prepared using tungsten-inert-gas and electron beam after various heat treatments. Although narrow groove tungsten-inert-gas welding reduced volume of weld bead, significant embrittlement was observed in a heat affected zone transformed due to heat input. Post weld heat treatment above 993 K successfully moderated the brittle transformed region. The hardness of the brittle region strongly depends on the heat treatment temperature. Meanwhile, strength of base metal was slightly reduced by the treatment at temperature ranging from 993 to 1053 K. Moreover, softening due to double welding was observed only in the weld metal, but negligible in base metal.

  15. Effects of heat treatment process for blanket fabrication on mechanical properties of F82H

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, T. E-mail: hiroset@fusion.naka.jaeri.go.jp; Shiba, K.; Sawai, T.; Jitsukawa, S.; Akiba, M

    2004-08-01

    The objectives of this work are to evaluate the effects of thermal history corresponding to a blanket fabrication process on Reduced Activation Ferritic/Martensitic steel (RAF/Ms) microstructure, and to establish appropriate Hot Isostatic Pressing (HIP) conditions without degradation in the microstructures. One of RAF/Ms F82H and its modified versions were investigated by metallurgical methods after isochronal heat treatments up to 1473 K simulating HIP thermal history. Although conventional F82H showed significant grain growth after conventional solid HIP conditions, F82H with 0.1 wt% tantalum maintained a fine grain structure after the same heat treatment. It is considered that the grain coarsening was caused by dissolution of tantalum-carbide which immobilizes grain boundaries. On the other hands, conventional RAF/Ms with coarse grains were recovered by post HIP normalizing at temperatures below the TaC solvus temperature. This process can refine the grain size of F82H to more than ASTM grain size number 7.

  16. Joining of 14YWT and F82H by friction stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Hoelzer, D.T., E-mail: hoelzerd@ornl.gov; Unocic, K.A.; Sokolov, M.A.; Feng, Z.

    2013-11-15

    Friction stir welding was investigated for joining specimens of the ODS 14YWT ferritic alloy together and to an F82H tempered martensitic steel plate. The FSW run was performed using a polycrystalline boron nitride tool and resulted in good bonding between 14YWT/14YWT and 14YWT/F82H. Joints and interfaces were observed by light microscopy and SEM analysis to be narrow in width. The ultra-small grain size of 14YWT increased by a factor up to 4 while that of F82H decreased by a considerable amount in the weld zones. The TEM analysis showed no significant changes in the size of the oxygen-enriched nanoclusters in the weld zone of 14YWT. However, defects such as a wormhole on the advancing side of the weld zone in 14YWT and small pores associated with joints and interfaces were observed in the FSW sample. The hardness measurements from unaffected zone into weld zones showed ∼20% decrease in hardness for 14YWT (from ∼500 VH to ∼380 VH) and ∼100% increase in hardness of F82H (from ∼220 VH to ∼440 VH)

  17. Preliminary results of the round-robin testing of F82H

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, K.; Yamanouchi, N.; Tohyama, A.

    1996-10-01

    Preliminary results of metallurgical, physical and mechanical properties of low activation ferritic steel F82H (IEA heat) were obtained in the round-robin test in Japan. The properties of IEA heat F82H were almost the same as the original F82H.

  18. Tensile behavior of F82H with and without spectral tailoring

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, K. E-mail: shiba@realab01.tokai.jaeri.go.jp; Klueh, R.L.; Miwa, Y.; Robertson, J.P.; Hishinuma, A

    2000-12-01

    The effects of neutron spectrum on tensile properties of the low-activation martensitic steel F82H (8Cr-2WVTa) was examined using a thermal neutron shield to tailor the neutron spectrum for steels irradiated in the high flux isotope reactor (HFIR). The yield stresses of spectrally tailored specimens irradiated in HFIR to 5 dpa at 300 deg. C and 500 deg. C are on trend lines obtained from unshielded irradiation in HFIR. No significant effect of the neutron spectrum on tensile properties could be detected.

  19. Corrosion rate of parent and weld materials of F82H and JPCA steels under LBE flow with active oxygen control at 450 and 500 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Kenji [Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)], E-mail: kikuchi.kenji21@jaea.go.jp; Kamata, Kinya; Ono, Mikinori; Kitano, Teruaki; Hayashi, Kenichi [Mitsui Engineering and Ship-building Co., Ltd., 5-6-4 Tsukiji, Chuo-ku, Tokyo 104-8439 (Japan); Oigawa, Hiroyuki [Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

    2008-06-30

    Corrosion behavior of parent and weld materials of F82H and JPCA was studied in the circulating LBE loop under impinging flow. These are candidate materials for Japanese Accelerator Driven System (ADS) beam windows. Maximum temperatures were kept to 450 and 500 deg. C with 100 deg. C constant temperature difference. Main flow velocity was 0.4-0.6 m/s in every case. Oxygen concentration was controlled to 2-4 x 10{sup -5} mass% although there was one exception. Testing time durations were 500-3000 h. Round bar type specimens were put in the circular tube of the loop. An electron beam weld in the middle of specimens was also studied. Optical microscopy, electron microscopy, X-ray element analyses and X-ray diffraction were used to investigate corrosion in these materials. Consequently corrosion depth and stability of those oxide layers were characterized based on the analyses. For a long-term behavior a linear law is recommended to predict corrosion in the ADS target design.

  20. Embrittlement of reduced-activation ferritic/martensitic steels irradiated in HFIR at 300 deg. C and 400 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. E-mail: ku2@ornl.gov; Sokolov, M.A.; Shiba, K.; Miwa, Y.; Robertson, J.P

    2000-12-01

    Miniature tensile and Charpy specimens of four ferritic/martensitic steels were irradiated at 300 deg. C and 400 deg. C in the high flux isotope reactor (HFIR) to a maximum dose of {approx}12 dpa. The steels were standard F82H (F82H-Std), a modified F82H (F82H-Mod), ORNL 9Cr-2WVTa, and 9Cr-2WVTa-2Ni, the 9Cr-2WVTa containing 2% Ni to produce helium by (n,{alpha}) reactions with thermal neutrons. More helium was produced in the F82H-Std than the F82H-Mod because of the presence of boron. Irradiation embrittlement in the form of an increase in the ductile-brittle transition temperature ({delta}DBTT) and a decrease in the upper-shelf energy (USE) occurred for all the steels. The two F82H steels had similar {delta}DBTTs after irradiation at 300 deg. C, but after irradiation at 400 deg. C, the {delta}DBTT for F82H-Std was less than for F82H-Mod. Under these irradiation conditions, little effect of the extra helium in the F82H-Std could be discerned. Less embrittlement was observed for 9Cr-2WVTa steel irradiated at 400 deg. C than for the two F82H steels. The 9Cr-2WVTa-2Ni steel with {approx}115 appm He had a larger {delta}DBTT than the 9Cr-2WVTa with {approx}5 appm He, indicating a possible helium effect.

  1. Corrosion and stress corrosion cracking of ferritic/martensitic steel in super critical pressurized water

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, T. [Naka Fusion Research Institute, JAEA, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)]. E-mail: hirose.takanori@jaea.go.jp; Shiba, K. [Naka Fusion Research Institute, JAEA, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan); Enoeda, M. [Naka Fusion Research Institute, JAEA, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan); Akiba, M. [Naka Fusion Research Institute, JAEA, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)

    2007-08-01

    A water-cooled solid breeder (WCSB) blanket cooled by high temperature SCPW (super critical pressurized water) is a practical option of DEMO reactor. Therefore, it is necessary to check the compatibility of the steel with SCPW. In this work, reduced activation ferritic/martensitic steel, F82H has been tested through slow strain rate tests (SSRT) in 23.5 MPa SCPW. And weight change behavior was measured up to 1000 h. F82H did not demonstrated stress corrosion cracking and its weight simply increased with surface oxidation. The weight change of F82H was almost same as commercial 9%-Cr steels. According to a cross-sectional analysis and weight change behavior, corrosion rate of F82H in the 823 K SCPW is estimated to be 0.04 mm/yr.

  2. Embrittlernent of irradiated F82H in the absence of irradiation hardening

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, Ronald L [ORNL; Shiba, Kiyoyuki [ORNL; Sokolov, Mikhail A [ORNL

    2009-01-01

    Neutron irradiation of 7-12% Cr ferritic/martensitic steels below 425-450 C produces microstructural defects and precipitation that cause an increase in yield stress. This irradiation hardening causes embrittlement, which is observed in a Charpy impact or fracture toughness test as an increase in the ductile-brittle transition temperature. Based on observations that show little change in strength in steels irradiated above 425-450 C, the general conclusion has been that no embrittlement occurs above these temperatures. In a recent study of F82H steel, significant embrittlement was observed after irradiation at 500 C. This embrittlement is apparently due to irradiation-accelerated Laves-phase precipitation. Observations of the embrittlement in the absence of hardening has been examined and analyzed with thermal-aging studies and computational thermodynamics calculations to illuminate and understand the effect.

  3. Joining technologies of reduced activation ferritic/martensitic steel for blanket fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, T. [JAERI, Naka Fusion Establishment, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)]. E-mail: hiroset@fusion.naka.jaeri.go.jp; Shiba, K. [JAERI, Naka Fusion Establishment, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan); Ando, M. [JAERI, Naka Fusion Establishment, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan); Enoeda, M. [JAERI, Naka Fusion Establishment, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan); Akiba, M. [JAERI, Naka Fusion Establishment, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)

    2006-02-15

    Reduced activation ferritic/martensitic steel, like F82H has been developed as a structural material for in vessel components because of its superior resistance to irradiation damage. As a blanket fabrication process, hot isostatic pressing (HIP) bonding has the great merit of near-net-shaping processing. The degassing conditions and surface roughness were investigated as parameters of HIP conditions. Although the surface roughness and degassing conditions had slight effects on tensile properties, the lack of degassing caused significant degradation of impact properties. A dissimilar metal joint between sintered tungsten and F82H was fabricated by a spark plasma sintering (SPS) method. The joint had no defects in spite of the large difference in thermal expansion coefficient between tungsten and F82H. It is considered that formation of a compliant layer of the ferritic phase can lead to successful bonding for the tungsten and F82H joint even without an artificial interlayer.

  4. Technical issues of reduced activation ferritic/martensitic steels for fabrication of ITER test blanket modules

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, H. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)], E-mail: tanigawa.hiroyasu@jaea.go.jp; Hirose, T.; Shiba, K. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kasada, R. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Wakai, E. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Serizawa, H.; Kawahito, Y. [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Jitsukawa, S. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kimura, A. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Kohno, Y. [Department of Materials Science and Engineering, Muroran Institute of Technology, Muroran, Hokkaido 050-8585 (Japan); Kohyama, A. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Katayama, S. [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Mori, H.; Nishimoto, K. [Division of Materials and Manufacturing Science, Osaka University, Ibaraki, Osaka 565-0871 (Japan); Klueh, R.L.; Sokolov, M.A.; Stoller, R.E.; Zinkle, S.J. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6132 (United States)

    2008-12-15

    Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems. The RAFM F82H was developed in Japan with emphasis on high-temperature properties and weldability. Extensive irradiation studies have conducted on F82H, and it has the most extensive available database of irradiated and unirradiated properties of all RAFMs. The objective of this paper is to review the R and D status of F82H and to identify the key technical issues for the fabrication of an ITER test blanket module (TBM) suggested from the recent research achievements in Japan. This work clarified that the primary issues with F82H involve welding techniques and the mechanical properties of weld joints. This is the result of the distinctive nature of the joint caused by the phase transformation that occurs in the weld joint during cooling, and its impact on the design of a TBM will be discussed.

  5. Effect of helium production on swelling of F82H irradiated in HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Wakai, E. E-mail: wakai@realab01.tokai.jaeri.go.jp; Hashimoto, N.; Miwa, Y.; Robertson, J.P.; Klueh, R.L.; Shiba, K.; Jistukawa, S

    2000-12-01

    The effects of helium production and heat treatment on the swelling of F82H steel irradiated in the HFIR to 51 dpa have been investigated using {sup 10}B, {sup 58}Ni and {sup 60}Ni-doped specimens. The swelling of tempered F82H-std and F82H doped with {sup 10}B irradiated at 400 deg. C ranged from 0.52% to 1.2%, while the swelling of the non-tempered F82H doped with {sup 58}Ni or {sup 60}Ni was less than 0.02%. At 300 deg. C the swelling in all steels was insignificant. In the F82H + Ni, a high number of density carbides formed in the matrix at these temperatures. The production of helium atoms enhanced the swelling of the F82H steel. However, the non-tempered treatment for the F82H + Ni suppressed remarkably the swelling. The cause of low swelling in the F82H + Ni may be due to the occurrence of the high density of carbides acting as sinks or the decrease of mobility of vacancies interacting with carbon atoms in matrix.

  6. Plastic flow properties and fracture toughness characterization of unirradiated and irradiated tempered martensitic steels

    Science.gov (United States)

    Spätig, P.; Bonadé, R.; Odette, G. R.; Rensman, J. W.; Campitelli, E. N.; Mueller, P.

    2007-08-01

    We investigate the plastic flow properties at low and high temperature of the tempered martensitic steel Eurofer97. We show that below room temperature, where the Peierls friction on the screw dislocation is active, it is necessary to modify the usual Taylor's equation between the flow stress and the square root of the dislocation density and to include explicitly the Peierls friction stress in the equation. Then, we compare the fracture properties of the Eurofer97 with those of the F82H steel. A clear difference of the fracture toughness-temperature behavior was found in the low transition region. The results indicate a sharper transition for Eurofer97 than for the F82H. Finally, the shift of the median toughness-temperature curve of the F82H steel was determined after two neutron irradiations performed in the High Flux Reactor in Petten.

  7. Swelling of F82H irradiated at 673 K up to 51 dpa in HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Miwa, Y. E-mail: miway@popsvr.tokai.jaeri.go.jp; Wakai, E.; Shiba, K.; Hashimoto, N.; Robertson, J.P.; Rowcliffe, A.F.; Hishinuma, A

    2000-12-01

    Reduced-activation ferritic/martensitic steel, F82H (8Cr-2W-0.2V-0.04Ta-0.1C), and variants doped with isotopically tailored boron were irradiated at 673 K up to 51 dpa in the high flux isotope reactor (HFIR). The concentrations of {sup 10}B in these alloys were 4, 62, and 325 appm during HFIR irradiation which resulted in the production of 4, 62 and 325 appm He, respectively. After irradiation, transmission electron microscopy (TEM) was carried out. The number density of cavities increased and the average diameter of cavities decreased with increasing amounts of {sup 10}B. The number density decreased and the average diameter increased with increasing displacement damage. Swelling increased as a function of displacement damage and He concentration.

  8. Development of an extensive database of mechanical properties for Reduced Activation Ferritic/Martensitic Steels

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, H.; Shiba, K.; Ando, M.; Wakai, E.; Jitsukawa, S. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Kasada, R.; Kimura, A.; Kohyama, A. [Kyoto Univ., lnstitute of Advanced Energy (Japan); Kohno, Y. [Muroran Institute of Technology, Muroran, Hokkaido (Japan); Klueh, R.L. [0ak Ridge Noational Laboratory, TN (United States); Sokolov, M.; Stoller, R.; Zinklek, S. [0ak Ridge Noational Laboratory, Materials Science and Technology Div., TN (United States); Yamamoto, T.; Odette, G. [UCSB, Dept. of Chemical Engineering UCSB, Santa-Barbara (United States); Kurtz, R.J. [Pacifie Northwest National Laboratory, Richland WA (United States)

    2007-07-01

    Full text of publication follows: Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems, as they have been developed based on massive industrial experience of ferritic/martensitic steel replacing Mo and Nb of high chromium heat resistant martensitic steels (such as modified 9Cr-1Mo) with W and Ta, respectively. F82H (8Cr-2W-0.2V-0.04Ta-0.1C) and JLF-1 (9Cr-2W-0.2V-0.08Ta-0.1C) are RAFMs, which have been developed and studied in Japan and the various effects of irradiation were reported. F82H is designed with emphasis on high temperature property and weldablility, and was provided and evaluated in various countries as a part of the IEA fusion materials development collaboration. The Japan/US collaboration program also has been conducted with the emphasis on heavy irradiation effects of F82H, JLF-1 and ORNL9Cr2WVTa over the past two decades using Fast Flux Testing Facility (FFTF) of PNNL and High Flux Isotope Reactor (HFIR) of ORNL, and the irradiation condition of the irradiation capsules of those reactors were precisely controlled by the well matured capsule designing and instrumentation. Now, among the existing database for RAFMs the most extensive one is that for F82H. The objective of this paper is to review the database status of RAFMs, mainly on F82H, to identify the key issues for the future development of database. Tensile, fracture toughness, creep and fatigue properties and microstructural studies before and after irradiation are summarized. (authors)

  9. Hydrogen permeation behavior through F82H at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, S.; Katayama, K.; Shimozori, M.; Fukada, S. [Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kyushu (Japan); Ushida, H. [Energy Science and Engineering, Faculty of Engineering, Kyushu University, Kyushu (Japan); Nishikawa, M. [Malaysia-Japan International Institute of Technology, UTM, Kuala Lumpur (Malaysia)

    2015-03-15

    F82H is a primary candidate of structural material and coolant pipe material in a blanket of a fusion reactor. Understanding tritium permeation behavior through F82H is important. In a normal operation of a fusion reactor, the temperature of F82H will be controlled below 550 C. degrees because it is considered that F82H can be used up to 30,000 hours at 550 C. degrees. However, it is necessary to assume the situation where F82H is heated over 550 C. degrees in a severe accident. In this study, hydrogen permeation behavior through F82H was investigated in the temperature range from 500 to 800 C. degrees. In some cases, water vapor was added in a sample gas to investigate an effect of water vapor on hydrogen permeation. The permeability of hydrogen in the temperature range from 500 to 700 C. degrees agreed well with the permeability reported by E. Serra et al. The degradation of the permeability by water vapor was not observed. After the hydrogen permeation reached in a steady state at 700 C. degrees, the F82H sample was heated to 800 C. degrees. The permeability of hydrogen through F82H sample which was once heated up to 800 C. degrees was lower than that of the original one. (authors)

  10. Evaluation of Cu as an interlayer in Be/F82H diffusion bonds for ITER TBM

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, R.M., E-mail: rhunt@ucla.edu [Mechanical and Aerospace Engineering Department, UCLA, 44-128 Engineering IV, 420 Westwood Plaza, Los Angeles, CA 90025-1597 (United States); Goods, S.H., E-mail: shgoods@sandia.gov [Sandia National Laboratories, 7011 East Ave., Livermore, CA 94550 (United States); Ying, A., E-mail: ying@fusion.ucla.edu [Mechanical and Aerospace Engineering Department, UCLA, 44-128 Engineering IV, 420 Westwood Plaza, Los Angeles, CA 90025-1597 (United States); Dorn, C.K., E-mail: christopher_dorn@brushwellman.com [Brush Wellman Inc., 14710 W. Portage River So. Road, Elmore, OH 43416 (United States); Abdou, M., E-mail: abdou@fusion.ucla.edu [Mechanical and Aerospace Engineering Department, UCLA, 44-128 Engineering IV, 420 Westwood Plaza, Los Angeles, CA 90025-1597 (United States)

    2011-10-01

    Copper has been investigated as a potential interlayer material for diffusion bonds between beryllium and Reduced Activation Ferritic/Martensitic (RAFM) steel. Utilizing Hot Isostatic Pressing (HIP), copper was directly bonded to a RAFM steel, F82H, at 650 deg. C, 700 deg. C, 750 deg. C, 800 deg. C and 850 deg. C, under 103 MPa for 2 h. Interdiffusion across the bonded interface was limited to 1 {mu}m or less, even at the highest HIP'ing temperature. Through mechanical testing it was found that samples HIP'ed at 750 deg. C and above remain bonded up to 211 MPa under tensile loading, at which point ductile failure occurred in the bulk copper. As titanium will be used as a barrier layer to prevent the formation of brittle Be/Cu intermetallics, additional annealing studies were performed on copper samples coated with a titanium thin film to study Ti/Cu interdiffusion characteristics. Samples were heated to temperatures between 650 deg. C and 850 deg. C for 2 h in order to mimic the range of likely HIP temperatures. A correlation was drawn between HIP temperature and diffusion depth for use in determining the minimum Ti film thickness necessary to block diffusion in the Be/F82H joint.

  11. Evaluation of Cu as an interlayer in Be/F82H diffusion bonds for ITER TBM

    Science.gov (United States)

    Hunt, R. M.; Goods, S. H.; Ying, A.; Dorn, C. K.; Abdou, M.

    2011-10-01

    Copper has been investigated as a potential interlayer material for diffusion bonds between beryllium and Reduced Activation Ferritic/Martensitic (RAFM) steel. Utilizing Hot Isostatic Pressing (HIP), copper was directly bonded to a RAFM steel, F82H, at 650 °C, 700 °C, 750 °C, 800 °C and 850 °C, under 103 MPa for 2 h. Interdiffusion across the bonded interface was limited to 1 μm or less, even at the highest HIP'ing temperature. Through mechanical testing it was found that samples HIP'ed at 750 °C and above remain bonded up to 211 MPa under tensile loading, at which point ductile failure occurred in the bulk copper. As titanium will be used as a barrier layer to prevent the formation of brittle Be/Cu intermetallics, additional annealing studies were performed on copper samples coated with a titanium thin film to study Ti/Cu interdiffusion characteristics. Samples were heated to temperatures between 650 °C and 850 °C for 2 h in order to mimic the range of likely HIP temperatures. A correlation was drawn between HIP temperature and diffusion depth for use in determining the minimum Ti film thickness necessary to block diffusion in the Be/F82H joint.

  12. Effects of helium implantation on fatigue properties of F82H-IEA heat

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, N.; Murase, Y.; Nagakawa, J. [National Research Institute for Metals, Tsukuba, Ibaraki (Japan)

    2007-07-01

    Full text of publication follows: Ferritic steels including reduced activation ones that have been recognized as attractive structural candidates for DEMO reactors and the beyond are known to be highly resistant to helium embrittlement. However, almost studies that deduced this behavior have been carried out by means of short time experiments such as tensile tests, and a few results are available concerning long term inspections, although the detrimental helium effect appears more severely in the latter. The aim of this work is to obtain further information on the influence of helium on fatigue properties of a representative reduced activation ferritic/martensitic steel F82H (8Cr2WVTa) using helium implantation technique with a cyclotron. The material examined is an IEA heat version of F82H. In order to realize a fine grain size due to thin specimens (0.08 mm thick) for ion irradiation, normalizing was conducted at rather low temperature of 1213 K, followed by tempering at 1023 K. Helium was implanted by {alpha}-particle irradiation at 823 K, a desired highest temperature of this material for first wall application, to the concentration of 100 appm He with an implantation rate of about 1.7 x 10{sup -3} appm He/s. Subsequent fatigue tests were conducted at the same temperature as that of irradiation, not only on implanted specimens but also on reference controls which were not implanted with helium but experienced the same metallurgical histories as those of irradiated ones. After fracture, samples were observed with electron microscopes. In short time periods, it has been notified that helium introduction caused no significant deterioration of both fatigue life and extension at fracture. In addition, all specimens failed in a fully trans-crystalline and ductile manner, irrespective of whether helium was present or not. Indication of grain boundary embrittlement was therefore not discerned. These facts would reflect insusceptible characteristics of this material to

  13. Structural and mechanical properties of welded joints of reduced activation martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Filacchioni, G. E-mail: gianni.filacchioni@casaccia.enea.it; Montanari, R.; Tata, M.E.; Pilloni, L

    2002-12-01

    Gas tungsten arc welding and electron beam welding methods were used to realise welding pools on plates of reduced activation martensitic steels. Structural and mechanical features of these simulated joints have been investigated in as-welded and post-welding heat-treated conditions. The research allowed to assess how each welding technique affects the original mechanical properties of materials and to find suitable post-welding heat treatments. This paper reports results from experimental activities on BATMAN II and F82H mod. steels carried out in the frame of the European Blanket Project - Structural Materials Program.

  14. Effect of mechanical restraint on weldability of reduced activation ferritic/martensitic steel thick plates

    Energy Technology Data Exchange (ETDEWEB)

    Serizawa, Hisashi, E-mail: serizawa@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Nakamura, Shinichiro [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suite, Osaka 565-0871 (Japan); Tanaka, Manabu; Kawahito, Yousuke [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Tanigawa, Hiroyasu [Fusion Research and Development Directorate, Japan Atomic Energy Agency, 2-4 Shirakita, Shirane, Naka, Ibaraki 319-1195 (Japan); Katayama, Seiji [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2011-10-01

    As one of the reduced activation ferritic/martensitic steels, the weldability of thick F82H plate was experimentally examined using new heat sources in order to minimize the total heat input energy in comparison with TIG welding. A full penetration of 32 mm thick plate could be produced as a combination of a 12 mm deep first layer generated by a 10 kW fiber laser beam and upper layers deposited by a plasma MIG hybrid welding with Ar + 2%O shielding gas. Also, the effect of mechanical restraint on the weldability under EB welding of thick F82H plate was studied by using FEM to select an appropriate specimen size for the basic test. The appropriate and minimum size for the basic test of weldability under EB welding of 90 mm thick plate might be 200 mm in length and 400 mm in width where the welding length should be about 180 mm.

  15. A study on martensitic and austenitic steels after exposure in mercury at 573 K up to 5000 h

    Energy Technology Data Exchange (ETDEWEB)

    Zalavutdinov, R.Kh. E-mail: rinad@ipc.rssi.ru; Dai, Y.; Gorodetsky, A.E.; Bauer, G.S.; Alimov, V.Kh.; Zakharov, A.P

    2001-07-01

    The chemical composition, structure and morphology of surface layers formed on stressed martensitic (F82H, MANET-II) and austenitic (316L) steel samples after exposure in static mercury with air or Ar inside the containers for 5000 and 2000 h, respectively, at 573 K have been studied by different surface analysis techniques (electron probe microanalysis (EPMA), scanning electron microscopy (SEM), reflected high energy electron diffraction (RHEED), X-ray diffraction (XRD), and secondary ion mass spectrometry (SIMS)). It has been shown that all three steels are oxidized (oxide thickness greatest on F82H and least for 316L) and covered with red HgO single crystals when air is present in the system. The oxidation of the steels and Hg can be suppressed by using Ar in the containers. Cracks have been found only at the notch roots of the 316L samples. There is no evident Hg corrosion observed.

  16. Influence of helium on impact properties of reduced-activation ferritic/martensitic Cr-steels

    Science.gov (United States)

    Lindau, R.; Möslang, A.; Preininger, D.; Rieth, M.; Röhrig, H. D.

    Instrumented Charpy impact tests of the reduced activation type 8Cr2WVTa steel F82H have been performed after homogeneous implantation of 300 appm helium at 250°C. The results are compared with investigations on mixed spectrum neutron irradiated (HFR Petten) specimens. After neutron irradiation at 250°C to the same low damage dose of 0.2 dpa, the ductile-brittle transition temperature shift (ΔDBTT) amounts to 18°C, whereas a much higher ΔDBTT of 42°C has been measured after helium implantation. These results are compared with other neutron irradiated ferritic/martensitic steels having different boron levels and thus different helium contents. A model is proposed which describes the dynamic brittle fracture of martensitic/ferritic steels by a stress-induced propagation of micro-cracks, taking into account radiation induced hardening as well as helium bubble formation.

  17. Metallography studies and hardness measurements on ferritic/martensitic steels irradiated in STIP

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); China Institute of Atomic Energy, Beijing 102413 (China); Long, B. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Dai, Y. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)], E-mail: yong.dai@psi.ch

    2008-06-30

    In this work metallography investigations and microhardness measurements have been performed on 15 ferritic/martensitic (FM) steels and 6 weld metals irradiated in the SINQ Target Irradiation Program (STIP). The results demonstrate that all the steels have quite similar martensite lath structures. However, the sizes of the prior austenite grain (PAG) of these steels are quite different and vary from 10 to 86 {mu}m. The microstructure in the fusion zones (FZ) of electron-beam welds (EBWs) of 5 steels (T91, EM10, MANET-II, F82H and Optifer-IX) is similar in respect to the martensite lath structure and PAG size. The FZ of the inert-gas-tungsten weld (TIGW) of the T91 steel shows a duplex structure of large ferrite gains and martensite laths. The microhardness measurements indicate that the normalized and tempered FM steels have rather close hardness values. The unusual high hardness values of the EBW and TIGW of the T91 steel were detected, which suggests that these materials are without proper tempering or post-welding heat treatment.

  18. Weldability of reduced activation ferritic/martensitic steel under ultra power density fiber laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Serizawa, H.; Kawahito, Y.; Katayama, S. [Osaka Univ., Joining and Welding research Institute, Ibaraki (Japan); Ogiwara, H.; Tanigawa, H. [Japan Atomic Energy Agency, Ibaraki-ken (Japan)

    2007-07-01

    Full text of publication follows: Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems as it has been developed based on massive industrial experience of ferritic/martensitic steel replacing Mo and Nb of high chromium heat resistant martensitic steels (such as modified 9Cr-1Mo) with W and Ta, respectively. As one of RAFMS, F82H, which has been developed and studied in Japan, is designed with emphasis on high temperature property and weldablility, and was provided and evaluated in various countries as a part of the collaboration of IEA fusion materials development. Although F82H is the well perceived RAFM as ITER Test Blanket Module (TBM) structural material, the weldability was proved though TIG, EB and YAG laser weld tests using only 15 and 25 mm thickness plate. In order to reduce the welding distortion, the residual stress and the area of the heat affected zone, it is necessary to decrease the total heat input under the welding. Recently, as a result of R and D efforts about the sources of laser beam, a high-power fiber laser beam has been developed as one of the desirable heat sources for high-speed and deep-penetration welding. Since the power density of the fiber laser beam is very large, it is possible to increase the welding speed more than 10 m/min. So, in this study, the weldability of 1.5 mm thickness F82H plate and pipe was examined by using a ultra power density fiber laser, in order to reveal the excellent weldability of F82H. As a basic study of the butt welding between 1.5 mm plate and 1.5 mm thickness pipe with 11 mm outer diameter, the focus position, the beam position and the laser power were varied using 25 mm square plate and 25 mm length pipe. Then, by using the fiber laser with 1.1 MW/mm{sup 2} peak power density under the appropriate welding condition obtained from the basic study, a full penetrated weld bead with narrow width was formed in the butt

  19. Destructive and non-destructive evaluation methods of interface on F82H HIPed joints

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Hirotatsu, E-mail: hkishi@mmm.muroran-it.ac.jp [OASIS, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Muramatsu, Yusuke [Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Asakura, Yuki [OASIS, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Endo, Tetsuo [Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Kohyama, Akira [OASIS, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan)

    2016-11-01

    Highlights: • The first wall of F82H steel will be fabricated by the HIP method. • Inspection techniques need to be developed for the HIPed interface. • Both destructive and non-destructive inspection techniques are introduced. - Abstract: The first walls of F82H steel with built-in cooling channels will be assembled thin plates and rectangular pipes by a HIP method. Silicon oxides form on an interface of HIPed joints during HIPing and result in the lowering of toughness of the HIPed joints. A large issue is investigation method of HIPed interface. The flexibility of specimen size for the investigation will be necessary because of the thin wall of cooling channels. A small specimen destructive test technique which is able to distinguish a base metal and an excellent HIPed joint has been desired, and recent researches find out a torsion test method to solve the issue. Non-destructive test technique is another issue for the inspection of the first wall. An ultrasonic inspection method is a candidate but silicon oxides are too small to produce good flaw echo from oxides, some solutions will be necessary. Present research introduces the current status of development of small specimen destructive test technique and the ultrasonic method for the first wall inspection.

  20. Microstructural analysis of ferritic-martensitic steels irradiated at low temperature in HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, N.; Robertson, J.P.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States); Wakai, E. [Japan Atomic Energy Research Inst. (Japan)

    1998-09-01

    Disk specimens of ferritic-martensitic steel, HT9 and F82H, irradiated to damage levels of {approximately}3 dpa at irradiation temperatures of either {approximately}90 C or {approximately}250 C have been investigated by using transmission electron microscopy. Before irradiation, tempered HT9 contained only M{sub 23}C{sub 6} carbide. Irradiation at 90 C and 250 C induced a dislocation loop density of 1 {times} 10{sup 22} m{sup {minus}3} and 8 {times} 10{sup 21} m{sup {minus}3}, respectively. in the HT9 irradiated at 250 C, a radiation-induced phase, tentatively identified as {alpha}{prime}, was observed with a number density of less than 1 {times} 10{sup 20} m{sup {minus}3}. On the other hand, the tempered F82H contained M{sub 23}C{sub 6} and a few MC carbides; irradiation at 250 C to 3 dpa caused minor changes in these precipitates and induced a dislocation loop density of 2 {times} 10{sup 22} m{sup {minus}3}. Difference in the radiation-induced phase and the loop microstructure may be related to differences in the post-yield deformation behavior of the two steels.

  1. On the transition toughness of two RA martensitic steels in the irradiation hardening regime: a mechanism-based evaluation

    Science.gov (United States)

    Odette, G. R.; Rathbun, H. J.; Rensman, J. W.; van den Broek, F. P.

    2002-12-01

    An analysis of the transition fracture toughness and constitutive behavior of F82H and Eurofer97 reduced activation martensitic steels are presented in both unirradiated and irradiated conditions. The unirradiated toughness data for F82H show very steep temperature dependence and the Eurofer97 toughness data measured with 5 mm versus 10 mm thick specimens are systematically higher. Both of these observations indicate a loss of constraint. Constraint loss adjustments are applied using a three-dimensional finite element analysis based toughness scaling model. The adjusted F82H results can be represented by a master curve (MC) and the corresponding 5 and 10 mm adjusted data fall in the same scatter band. The 10 mm irradiated specimens, with generally lower toughness levels, suffer minimal constraint loss. The irradiation induced MC T0 shifts (Δ T0) are analyzed in terms of changes in constitutive properties. The Δ T0 are generally consistent with the observed irradiation hardening. However, the effects of irradiation on post-yield strain hardening behavior must be considered to obtain self-consistent hardening-shift relations.

  2. Ultrahigh Ductility, High-Carbon Martensitic Steel

    Science.gov (United States)

    Qin, Shengwei; Liu, Yu; Hao, Qingguo; Zuo, Xunwei; Rong, Yonghua; Chen, Nailu

    2016-10-01

    Based on the proposed design idea of the anti-transformation-induced plasticity effect, both the additions of the Nb element and pretreatment of the normalization process as a novel quenching-partitioning-tempering (Q-P-T) were designed for Fe-0.63C-1.52Mn-1.49Si-0.62Cr-0.036Nb hot-rolled steel. This high-carbon Q-P-T martensitic steel exhibits a tensile strength of 1890 MPa and elongation of 29 pct accompanied by the excellent product of tensile and elongation of 55 GPa pct. The origin of ultrahigh ductility for high-carbon Q-P-T martensitic steel is revealed from two aspects: one is the softening of martensitic matrix due to both the depletion of carbon in the matensitic matrix during the Q-P-T process by partitioning of carbon from supersaturated martensite to retained austenite and the reduction of the dislocation density in a martensitic matrix by dislocation absorption by retained austenite effect during deformation, which significantly enhances the deformation ability of martensitic matrix; another is the high mechanical stability of considerable carbon-enriched retained austenite, which effectively reduces the formation of brittle twin-type martensite. This work verifies the correctness of the design idea of the anti-TRIP effect and makes the third-generation advanced high-strength steels extend to the field of high-carbon steels from low- and medium-carbon steels.

  3. Long-term properties of reduced activation ferritic/martensitic steels for fusion reactor blanket system

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, Kiyoyuki, E-mail: Shiba.kiyoyuki@jaea.go.jp [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Tanigawa, Hiroyasu; Hirose, Takanori; Sakasegawa, Hideo; Jitsukawa, Shiro [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

    2011-12-15

    Thermal aging properties of reduced activation ferritic/martensitic steel F82H was researched. The aging was performed at temperature ranging from 400 Degree-Sign C to 650 Degree-Sign C up to 100,000 h. Microstructure, precipitates, tensile properties, and Charpy impact properties were carried out on aged materials. Laves phase was found at temperatures between 550 and 650 Degree-Sign C and M{sub 6}C type carbides were found at the temperatures between 500 and 600 Degree-Sign C over 10,000 h. These precipitates caused degradation in toughness, especially at temperatures ranging from 550 Degree-Sign C to 650 Degree-Sign C. Tensile properties do not have serious aging effect, except for 650 Degree-Sign C, which caused large softening even after 10,000 h. Increase of precipitates also causes some degradation in ductility, but it is not critical. Large increase in ductile-to-brittle transition temperature was observed in the 650 Degree-Sign C aging. It was caused by the large Laves phase precipitation at grain boundary. Laves precipitates at grain boundary also degrades the upper-shelf energy of the aged materials. These aging test results indicate F82H can be used up to 30,000 h at 550 Degree-Sign C.

  4. Microstructure and cleavage in lath martensitic steels

    Directory of Open Access Journals (Sweden)

    John W Morris Jr, Chris Kinney, Ken Pytlewski and Y Adachi

    2013-01-01

    Full Text Available In this paper we discuss the microstructure of lath martensitic steels and the mechanisms by which it controls cleavage fracture. The specific experimental example is a 9Ni (9 wt% Ni steel annealed to have a large prior austenite grain size, then examined and tested in the as-quenched condition to produce a relatively coarse lath martensite. The microstructure is shown to approximate the recently identified 'classic' lath martensite structure: prior austenite grains are divided into packets, packets are subdivided into blocks, and blocks contain interleaved laths whose variants are the two Kurjumov–Sachs relations that share the same Bain axis of the transformation. When the steel is fractured in brittle cleavage, the laths in the block share {100} cleavage planes and cleave as a unit. However, cleavage cracks deflect or blunt at the boundaries between blocks with different Bain axes. It follows that, as predicted, the block size governs the effective grain size for cleavage.

  5. Embrittlement of irradiated ferritic/martensitic steels in the absence of irradiation hardening

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge National Laboratory, Materials Science and Technology Division, P.O. 2008 MS6138, Oak Ridge, TN 37831-6138 (United States)], E-mail: kluehrl@ornl.gov; Shiba, K. [Japan Atomic Energy Agency, Toki-Mura, Ibaraki (Japan); Sokolov, M.A. [Oak Ridge National Laboratory, Materials Science and Technology Division, P.O. 2008 MS6138, Oak Ridge, TN 37831-6138 (United States)

    2008-07-15

    Irradiation damage caused by neutron irradiation below 425-450 deg. C of 9-12% Cr ferritic/martensitic steels produces microstructural defects that cause an increase in yield stress. This irradiation hardening causes embrittlement observed in a Charpy impact test as an increase in the ductile-brittle transition temperature. Little or no change in strength is observed in steels irradiated above 425-450 deg. C. Therefore, the general conclusion has been that no embrittlement occurs above these temperatures. In a recent study, significant embrittlement was observed in F82H steel irradiated at 500 deg. C to 5 and 20 dpa without any change in strength. Earlier studies on several conventional steels also showed embrittlement effects above the irradiation-hardening temperature regime. Indications are that this embrittlement is caused by irradiation-accelerated or irradiation-induced precipitation. Observations of embrittlement in the absence of irradiation hardening that were previously reported in the literature have been examined and analyzed with computational thermodynamics calculations to illuminate and understand the effect.

  6. Tribocorrosion wear of austenitic and martensitic steels

    Directory of Open Access Journals (Sweden)

    G. Rozing

    2016-07-01

    Full Text Available This paper explores the impact of tribocorrosion wear caused by an aggressive acidic media. Tests were conducted on samples made of stainless steel AISI 316L, 304L and 440C. Austenitic steels were tested in their nitrided state and martensitic in quenched and tempered and then induction hardened state. Electrochemical corrosion resistance testing and analysis of the microstructure and hardness in the cross section was carried out on samples of selected steels. To test the possibility of applying surface modification of selected materials in conditions of use, tests were conducted on samples/parts in a worm press for final pressing.

  7. Microstructure property analysis of HFIR-irradiated reduced-activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, H. E-mail: tanigawa@popsvr.tokai.jaeri.go.jp; Hashimoto, N.; Sakasegawa, H.; Klueh, R.L.; Sokolov, M.A.; Shiba, K.; Jitsukawa, S.; Kohyama, A

    2004-08-01

    The effects of irradiation on the Charpy impact properties of reduced-activation ferritic/martensitic steels were investigated on a microstructural basis. It was previously reported that the ductile-brittle transition temperature (DBTT) of F82H-IEA and its heat treatment variant increased by about 130 K after irradiation at 573 K up to 5 dpa. Moreover, the shifts in ORNL9Cr-2WVTa and JLF-1 steels were much smaller, and the differences could not be interpreted as an effect of irradiation hardening. The precipitation behavior of the irradiated steels was examined by weight analysis and X-ray diffraction analysis on extraction residues, and SEM/EDS analysis was performed on extraction replica samples and fracture surfaces. These analyses suggested that the difference in the extent of DBTT shift could be explained by (1) smaller irradiation hardening at low test temperatures caused by irradiation-induced lath structure recovery (in JLF-1), and (2) the fracture stress increase caused by the irradiation-induced over-solution of Ta (in ORNL9Cr-2WVTa)

  8. Development of benchmark reduced activation ferritic/martensitic steels for fusion energy applications

    Science.gov (United States)

    Tanigawa, H.; Gaganidze, E.; Hirose, T.; Ando, M.; Zinkle, S. J.; Lindau, R.; Diegele, E.

    2017-09-01

    Reduced-activation ferritic/martensitic (RAFM) steel is the benchmark structural material for in-vessel components of fusion reactor. The current status of RAFM developments and evaluations is reviewed based on two leading RAFM steels, F82H and EUROFER-97. The applicability of various joining technologies for fabrication of fusion first wall and blanket structures, such as weld or diffusion bonding, is overviewed as well. The technical challenges and potential risks of utilizing RAFM steels as the structural material of in-vessel components are discussed, and possible mitigation methodology is introduced. The discussion suggests that deuterium-tritium fusion neutron irradiation effects currently need to be treated as an ambiguity factor which could be incorporated within the safety factor. The safety factor will be defined by the engineering design criteria which are not yet developed with regard to irradiation effects and some high temperature process, and the operating time condition of the in-vessel component will be defined by the condition at which those ambiguities due to neutron irradiation become too large to be acceptable, or by the critical condition at which 14 MeV fusion neutron irradiation effects is expected to become different from fission neutron irradiation effects.

  9. 3D finite element and experimental study of the size requirements for measuring toughness on tempered martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, P. [Fusion Technology-Materials, CRPP-EPFL, Association EURATOM-Confederation Suisse, 5232 Villigen PSI (Switzerland)], E-mail: pablo.mueller@psi.ch; Spaetig, P. [Fusion Technology-Materials, CRPP-EPFL, Association EURATOM-Confederation Suisse, 5232 Villigen PSI (Switzerland)

    2009-06-01

    The fracture properties of the tempered martensitic steel Eurofer97, which is among the main candidates for fusion power plant structural applications, were studied with two sizes of pre-cracked compact specimens (0.35T C(T) and 0.87T C(T)). The fracture toughness behavior was characterized within the temperature range -80 to -40 deg. C. The ductile-to-brittle transition reference temperature, as defined in the ASTM standard E1921, was around T{sub 0} {approx} -75 deg. C. At -60 deg. C, it was found that two sets of toughness data obtained with 0.35T and 0.87T C(T) specimens are not consistent with the size adjustments recommended in the ASTM standard. It was then shown that the underlying reason of this inconsistency is an inappropriate specimen size limit of the ASTM standard for this type of steel. From published fracture toughness data on the tempered martensitic steel F82H steel, similar results were also highlighted. 3D finite elements simulations of the compact specimens were performed to compare the stresses and deformations at the onset of fracture. A local approach model based on the attainment of a critical stress and a critical volume was used to study the constraint loss phenomenon. Within the framework of this model, the strong toughness increase by reducing the specimen size could be satisfactorily explained.

  10. 3D finite element and experimental study of the size requirements for measuring toughness on tempered martensitic steels

    Science.gov (United States)

    Mueller, P.; Spätig, P.

    2009-06-01

    The fracture properties of the tempered martensitic steel Eurofer97, which is among the main candidates for fusion power plant structural applications, were studied with two sizes of pre-cracked compact specimens (0.35T C(T) and 0.87T C(T)). The fracture toughness behavior was characterized within the temperature range -80 to -40 °C. The ductile-to-brittle transition reference temperature, as defined in the ASTM standard E1921, was around T0 ≈ -75 °C. At -60 °C, it was found that two sets of toughness data obtained with 0.35T and 0.87T C(T) specimens are not consistent with the size adjustments recommended in the ASTM standard. It was then shown that the underlying reason of this inconsistency is an inappropriate specimen size limit of the ASTM standard for this type of steel. From published fracture toughness data on the tempered martensitic steel F82H steel, similar results were also highlighted. 3D finite elements simulations of the compact specimens were performed to compare the stresses and deformations at the onset of fracture. A local approach model based on the attainment of a critical stress and a critical volume was used to study the constraint loss phenomenon. Within the framework of this model, the strong toughness increase by reducing the specimen size could be satisfactorily explained.

  11. Embrittlement of irradiated ferritic/martensitic steels in the absence of irradiation hardening

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States); Shiba, K. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Sokolov, M. [Oak Ridge National Laboratory, Materials Science and Technology Div., TN (United States)

    2007-07-01

    Full text of publication follows: Neutron irradiation of 9-12% Cr ferritic/martensitic steels below 425-450 deg. C produces microstructural defects that cause an increase in yield stress and ultimate tensile strength. This irradiation hardening causes embrittlement, which is observed in Charpy impact and toughness tests as an increase in ductile-brittle transition temperature (DBTT). Based on observations that show little change in strength in these steels irradiated above 425-450 deg. C, the general conclusion has been that no embrittlement occurs above this irradiation-hardening temperature regime. In a recent study of F82H steel irradiated at 300, 380, and 500 deg. C, irradiation hardening-an increase in yield stress-was observed in tensile specimens irradiated at the two lower temperatures, but no change was observed for the specimens irradiated at 500 deg. C. As expected, an increase in DBTT occurred for the Charpy specimens irradiated at 300 and 380 deg. C. However, there was an unexpected increase in the DBTT of the specimens irradiated at 500 deg. C. The observed embrittlement was attributed to the irradiation-accelerated precipitation of Laves phase. This conclusion was based on results from a detailed thermal aging study of F82H, in which tensile and Charpy specimens were aged at 500, 550, 600, and 650 deg. C to 30,000 h. These studies indicated that there was a decrease in yield stress at the two highest temperatures and essentially no change at the two lowest temperatures. Despite the strength decrease or no change, the DBTT increased for Charpy specimens irradiated at all four temperatures. Precipitates were extracted from thermally aged specimens, and the amount of precipitate was correlated with the increase in transition temperature. Laves phase was identified in the extracted precipitates by X-ray diffraction. Earlier studies on conventional elevated-temperature steels also showed embrittlement effects above the irradiation-hardening temperature

  12. Post irradiation plastic properties of F82H derived from the instrumented tensile tests

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, T. [Neutron Science Research Center, Japan Atomic Energy, Research Institute, Tokai-Mura, Ibaraki-Ken 319-1195 (Japan)]. E-mail: taguchi@popsvr.tokai.jaeri.go.jp; Jitsukawa, S. [Department of Materials Science, Japan Atomic Energy, Research Institute, Tokai-Mura, Ibaraki-Ken 319-1195 (Japan); Sato, M. [KKS, JFE, Kawasaki-Ku, Kawasaki-Shi, Kanagawa-Ken 210-0855 (Japan); Matsukawa, S. [KKS, JFE, Kawasaki-Ku, Kawasaki-Shi, Kanagawa-Ken 210-0855 (Japan); Wakai, E. [Department of Materials Science, Japan Atomic Energy, Research Institute, Tokai-Mura, Ibaraki-Ken 319-1195 (Japan); Shiba, K. [Department of Materials Science, Japan Atomic Energy, Research Institute, Tokai-Mura, Ibaraki-Ken 319-1195 (Japan)

    2004-12-01

    F82H (Fe-8Cr-2W) and its variant doped with 2%Ni were irradiated up to 20 dpa at 300 deg. C in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Post irradiation tensile testing was performed at room temperature. During testing, the images of the specimens including the necked region were continuously recorded. Tests on cold worked material were also carried out for comparison. From the load-displacement curves and the strain distributions obtains from the images, flow stress levels and strain hardening behavior was evaluated. A preliminary constitutive equation for the plastic deformation of irradiated F82H is presented. The results suggest that the irradiation mainly causes defect-induced hardening while it did not strongly affect strain hardening at the same flow stress level for F82H irradiated at 300 deg. C. The strain hardening of Ni doped specimens was, however, strongly affected by irradiation. Results provide basics to determine allowable stress levels at temperatures below 400 deg. C.

  13. Recent status and improvement of reduced-activation ferritic-martensitic steels for high-temperature service

    Science.gov (United States)

    Tan, L.; Katoh, Y.; Tavassoli, A.-A. F.; Henry, J.; Rieth, M.; Sakasegawa, H.; Tanigawa, H.; Huang, Q.

    2016-10-01

    Reduced-activation ferritic-martensitic (RAFM) steels, candidate structural materials for fusion reactors, have achieved technological maturity after about three decades of research and development. The recent status of a few developmental aspects of current RAFM steels, such as aging resistance, plate thickness effects, fracture toughness, and fatigue, is updated in this paper, together with ongoing efforts to develop next-generation RAFM steels for superior high-temperature performance. In addition to thermomechanical treatments, including nonstandard heat treatment, alloy chemistry refinements and modifications have demonstrated some improvements in high-temperature performance. Castable nanostructured alloys (CNAs) were developed by significantly increasing the amount of nanoscale MX (M = V/Ta/Ti, X = C/N) precipitates and reducing coarse M23C6 (M = Cr). Preliminary results showed promising improvement in creep resistance and Charpy impact toughness. Limited low-dose neutron irradiation results for one of the CNAs and China low activation martensitic are presented and compared with data for F82H and Eurofer97 irradiated up to ∼70 displacements per atom at ∼300-325 °C.

  14. Dependence of mode I and mixed mode I/III fracture toughness on temperature for a ferritic/martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.; Jones, R.H.; Gelles, D.S. [Pacific Northwest Lab., Richland, WA (United States)] [and others

    1995-04-01

    The objective is to investigate the dependence of mode I and mixed mode I/III fracture toughness on temperature in the range of {minus}95{degrees}C to 25{degrees}C for a low activation ferritic/martensitic stainless steel (F82-H). Mode I and mixed Mode I/III fracture toughnesses were investigated in the range of {minus}95 to 25{degree}C for a F82-H steel heat-treated in the following way; 1000{degree}C/20 h/air-cooled (AC), 1100{degree}C/7 min/AC, and 700{degree}C/2 h/AC. The results indicate that crack tip plasticity was increased by mixed mode loading, and suggest that at low temperature, mode I fracture toughness is the critical design parameter, but at temperatures above room temperature, expecially concerning fatigure and creep-fatigue crack growth rate, a mixed mode loading may be more harmful than a mode I loading for this steel because a mixed mode loading results in lower fracture toughness and higher crack tip plasticity (or dislocation activity).

  15. Effects of impurity elements on mechanical properties and microstructures of reduced-activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sawahata, A. [Ibaraki Univ., Graduate School of Science and Engineering, Hitachi (Japan); Tanigawa, H.; Shiba, K. [Japan Atomic Energy Agency, Naga-gun, Ibaraki-ken (Japan); Enomoto, M. [Ibaraki Univ., Dept. of Materials Science, Faculty of Engineering, Hitachi (Japan)

    2007-07-01

    Full text of publication follows: Reduced activation ferritic/martensitic steels (RAFs), such as F82H (Fe-8Cr-2W-0.2V- 0.04Ta-0.1C, in wt%), are one of the leading candidates for structural materials of fusion reactors. Impact property of F82H can be improved by adjusting the amount of tantalum or titanium concentration. On the other hand, it was reported by microstructure analyses of IEA steel that tantalum has a tendency to form oxides and causes a large dispersion of fracture toughness. In this study, the correlation between titanium or tantalum concentration and the impact property were reported focusing on difference in microstructure. Charpy impact test and microstructure analyses were carried out against modified F82H series of which titanium, nitrogen and tantalum composition were controlled. Charpy impact test results showed that the ductile-brittle transition temperature (DBTT) of T05A (0.05Ta- 0.0014N-steels. The size distribution analyses of oxides indicate that the number density of composite oxides in T05B was higher than in T05A. In addition, EDX analyses showed that composite oxides in T05B had a strong peak of titanium, but the peak were not detected in the oxides in T05A. These results suggest that titanium has a significant influence on the formation of oxides, and affects the impact property. The influence of tantalum concentration on the formation of these oxides and mechanical properties will be reported. (authors)

  16. Microstructure evolution of selected ferritic-martensitic steels under dual-beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Wanderka, N.; Camus, E.; Wollenberger, H. [Hahn-Meitner-Inst. Berlin GmbH (Germany)

    1997-11-01

    The authors present experimental results on the microstructure evolution of dual-beam irradiated (300 keV heavy ions plus 15 keV helium ions) ferritic-martensitic steels (Manet, DIN 1.4926, F82H mod). The helium bubble morphology as well as microchemistry of the alloys are investigated by means of transmission electron microscopy and field-ion microscopy with atom probe. The alloys were irradiated to fluences up to 50 dpa and implanted with helium up to a concentration of 1 at.% at the temperatures of 723 K and 773 K. The damage and implantation rates varied from 2.5 {center_dot} 10{sup {minus}3} dpa/s to 2.5 {center_dot} 10{sup {minus}2} dpa/s and from 0.5 appm/s to 5 appm/s, respectively. Size and number density of helium bubbles is found to be rate dependent. Smaller implantation rates produce larger helium bubbles and smaller bubble number densities. Regions of local enrichment of alloy elements, typically 5 nm in size, containing chromium (up to 40 at.%), silicon, and nickel are detected. Number densities of helium bubbles and of regions of chromium enrichments are comparable and lie between 10{sup 23}/m{sup 3} and 10{sup 24}/m{sup 3}. Possible extrapolation of the present ion irradiations to spallation source and fusion reactor conditions is shortly addressed.

  17. Creep resistant high temperature martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

    2017-01-31

    The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, copper, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followed by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.

  18. Creep resistant high temperature martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

    2015-11-13

    The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6 carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followed by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.

  19. Anomalous kinetics of lath martensite formation in stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Pantleon, Karen

    2015-01-01

    The kinetics of lath martensite formation in Fe-17.3 wt-%Cr-7.1 wt-%Ni-1.1 wt-%Al-0.08 wt-%C stainless steel was investigated with magnetometry and microscopy. Lath martensite forms during cooling, heating and isothermally. For the first time, it is shown by magnetometry during extremely slow...

  20. Mechanical properties and microstructure of F-82H welded joints using CO{sub 2} laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Yamanouchi, N.; Shiba, K.

    1996-10-01

    The laser welding of F-82H was successfully conducted. The heat affected zone of the welding, was about 21 mm width. It was quite adequate to make small specimens, such as SS-3 type sheet tensile specimen.

  1. Twin structure of the lath martensite in low carbon steel

    Directory of Open Access Journals (Sweden)

    Pan Zhang

    2016-04-01

    Full Text Available It has been well accepted that the martensites in quenched carbon steels exhibit two typical morphologies which are closely dependent on the carbon content, i.e. lath martensite in low carbon steels and lenticular martensite in high carbon steels. Based on conventional belief, the lath martensites in low carbon steels are with high density dislocations as the substructure, in contrast to twin substructure in lenticular high carbon martensite. In the present work, an intensive transmission electron microscopy investigation was made to characterize the microstructures of the lath martensite in a low carbon steel of 0.2 wt%C. It was found that lots of lath martensites consist of twin as their substructure, rather than high density dislocations. In addition, nanoscale precipitates cohering with ferrite matrix were found at the twin interfaces. The orientation relationships between the precipitates and the ferrite matrix are in good agreement with that of primitive hexagonal ω phase in titanium alloys and other bcc metals or alloys.

  2. Twin structure of the lath martensite in low carbon steel

    Institute of Scientific and Technical Information of China (English)

    Pan Zhang; Yulin Chen; Wenlong Xiao; Dehai Ping; Xinqing Zhao

    2016-01-01

    It has been well accepted that the martensites in quenched carbon steels exhibit two typical morphol-ogies which are closely dependent on the carbon content, i.e. lath martensite in low carbon steels and lenticular martensite in high carbon steels. Based on conventional belief, the lath martensites in low carbon steels are with high density dislocations as the substructure, in contrast to twin substructure in lenticular high carbon martensite. In the present work, an intensive transmission electron microscopy investigation was made to characterize the microstructures of the lath martensite in a low carbon steel of 0.2 wt%C. It was found that lots of lath martensites consist of twin as their substructure, rather than high density dislocations. In addition, nanoscale precipitates cohering with ferrite matrix were found at the twin interfaces. The orientation relationships between the precipitates and the ferrite matrix are in good agreement with that of primitive hexagonalωphase in titanium alloys and other bcc metals or alloys.&2016 Chinese Materials Research Society. Production and hosting by Elsevier B.V. This is an open access.

  3. Cyclic instability of martensite laths in reduced activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Armas, A.F.; Petersen, C. E-mail: claus.petersen@imf.fzk.de; Schmitt, R.; Avalos, M.; Alvarez, I

    2004-08-01

    Low cycle fatigue tests were performed in the temperature range between room temperature and 550 deg. C in low activation quenched and tempered steels. After the first few cycles a pronounced cyclic softening that continues up to failure is observed for all these steels. Although this softening is coincident with similar behaviour observed in commercial martensitic alloys, reduced activation steels present some remarkable different features. Almost all cyclic curves never reach a saturation stress and after few cycles, dependent on the total strain range, they converge in a common softening stage independent of the strain range. The mechanism governing this softening stage is almost independent of temperatures below 450 deg. C. The cyclic softening observed in the reduced activation steels is more pronounced than for MANET II and commercial martensitic steels. This fact is related to the difference in the Martensite Start temperature.

  4. Microstructure and hardness of HIP-bonded regions in F82H blanket structures

    Science.gov (United States)

    Furuya, K.; Wakai, E.; Ando, M.; Sawai, T.; Nakamura, K.; Takeuchi, H.; Iwabuchi, A.

    2002-12-01

    Metallurgical examinations and hardness measurements were performed at hot isostatic pressing (HIP)-bonded regions in blanket structures made from F82H alloy in order to investigate the HIP-bondability and the influence on the microstructure due to the HIP and heat treatments which would correspond to the fabrication of an actual blanket. The metallurgical examination showed that the HIP-bonded interfaces were sufficiently diffusion-bonded without significant defects, i.e. voids and/or exfoliations, although grain coarsening was observed at a part of the HIP interfaces. Hardness was nearly equal in the coarsening region and a region without coarsening, but about a 10 Hv increase was found in a boundary in between the regions with and without coarsening. Microcrystallized grains were observed in a region about ˜6 μm from HIP interfaces, and the hardness increased by about 0.2 GPa in the region.

  5. The Formation of Martensitic Austenite During Nitridation of Martensitic and Duplex Stainless Steels

    Science.gov (United States)

    Zangiabadi, Amirali; Dalton, John C.; Wang, Danqi; Ernst, Frank; Heuer, Arthur H.

    2017-01-01

    Isothermal martensite/ferrite-to-austenite phase transformations have been observed after low-temperature nitridation in the martensite and δ-ferrite phases in 15-5 PH (precipitation hardening), 17-7 PH, and 2205 (duplex) stainless steels. These transformations, in the region with nitrogen concentrations of 8 to 16 at. pct, are consistent with the notion that nitrogen is a strong austenite stabilizer and substitutional diffusion is effectively frozen at the paraequilibrium temperatures of our experiments. Our microstructural and diffraction analyses provide conclusive evidence for the martensitic nature of these phase transformations.

  6. Nanotribological behavior of deep cryogenically treated martensitic stainless steel

    Science.gov (United States)

    Bakoglidis, Konstantinos D; Tuckart, Walter R; Broitman, Esteban

    2017-01-01

    Cryogenic treatments are increasingly used to improve the wear resistance of various steel alloys by means of transformation of retained austenite, deformation of virgin martensite and carbide refinement. In this work the nanotribological behavior and mechanical properties at the nano-scale of cryogenically and conventionally treated AISI 420 martensitic stainless steel were evaluated. Conventionally treated specimens were subjected to quenching and annealing, while the deep cryogenically treated samples were quenched, soaked in liquid nitrogen for 2 h and annealed. The elastic–plastic parameters of the materials were assessed by nanoindentation tests under displacement control, while the friction behavior and wear rate were evaluated by a nanoscratch testing methodology that it is used for the first time in steels. It was found that cryogenic treatments increased both hardness and elastic limit of a low-carbon martensitic stainless steel, while its tribological performance was enhanced marginally. PMID:28904837

  7. Development status und future possibilities for martensitic creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Hald, J. [Technical Univ. Denmark, Lyngby (Denmark). Dept. of Mechanical Engineering

    2010-07-01

    In the last four decades new stronger modified 9%Cr martensitic creep resistant steels have been introduced in power plants, which has enabled increases in maximum achievable steam conditions from the previous 250 bar and 540-560 C up to the values of 300 bar and 600-620 C currently being introduced all over the world. In order to further increase the steam parameters of steel based power plants up to a target value of 650 C/325 bar it is necessary to double the creep strength of the martensitic steels. At the same time the resistance against steam oxidation must be improved by an increase of the chromium content in the steels from 9% to 12%. However, so far all attempts to make stronger 12%Cr steels have led to breakdowns in long-term creep strength. Significant progress has been achieved in the understanding of microstructure stability of the martensitic 9-12%Cr steels: Observed microstructure instabilities in 11-12%Cr steels are explained by Z-phase precipitation, which dissolves fine MN nitrides. Improved understanding of effects of B and N on long-term creep properties has formed the basis of a series of new stronger 9%Cr test alloys with improved creep strength. In parallel 9%Cr test steels with low C content show very promising behavior in long-term tests. However, the 9%Cr steels must be surface coated to protect against steam oxidation at high temperature applications above 620%C. A possibility to use fine Z-phases for strengthening of the martensitic steels has been identified, and this opens a new pathway for development of stable strong 12%Cr steels. There are still good prospects for the realization of a 325 bar / 650 C steam power plant all based on steel. (orig.)

  8. Nitride-strengthened reduced activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Hu Ping [Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenhe District, Shenyang, Liaoning 110016 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Yan Wei, E-mail: weiyan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenhe District, Shenyang, Liaoning 110016 (China); Deng Lifen [Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenhe District, Shenyang, Liaoning 110016 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Sha Wei [School of Planning, Architecture and Civil Engineering, Queen' s University of Belfast, Belfast BT9 5AG (United Kingdom); Shan Yiyin; Yang Ke [Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenhe District, Shenyang, Liaoning 110016 (China)

    2010-12-15

    Two nitride-strengthened reduced activation ferritic/martensitic (RAFM) steels with different Mn contents were investigated. The experimental steels were designed based on the chemical composition of Eurofer 97 steel but the C content was reduced to an extremely low level. Microstructure observation and hardness tests showed that the steel with low Mn content (0.47 wt.%) could not obtain a full martensitic microstructure due to the inevitable {delta}-ferrite independent of cooling rate after soaking. This steel showed similar room temperature strength and higher strength at 600 deg. C, but lower impact toughness, compared with Eurofer 97 steel. Fractography of the Charpy impact specimen revealed that the low room temperature toughness should be related to the Ta-rich inclusions initiating the cleavage fracture. The larger amount of V-rich nitrides and more dissolved Cr in the matrix could be responsible for the strength being similar to Eurofer 97 steel. In the second steel developed from the first steel by increasing the Mn content from 0.47 wt.% to 3.73 wt.%, a microstructure of full martensite could be obtained.

  9. Characteristics of modified martensitic stainless steel surfaces under tribocorrosion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Rozing, Goran [Osijek Univ. (Croatia). Chair of Mechanical Engineering; Marusic, Vlatko [Osijek Univ. (Croatia). Dept. of Engineering Materials; Alar, Vesna [Zagreb Univ. (Croatia). Dept. Materials

    2017-04-01

    Stainless steel samples were tested in the laboratory and under real conditions of tribocorrosion wear. Electrochemical tests were also carried out to verify the corrosion resistance of modified steel surfaces. Metallographic analysis and hardness testing were conducted on stainless steel samples X20Cr13 and X17CrNi16 2. The possibilities of applications of modified surfaces of the selected steels were investigated by testing the samples under real wear conditions. The results have shown that the induction hardened and subsequently nitrided martensitic steels achieved an average wear resistance of up to three orders of magnitude higher as compared to the delivered condition.

  10. Tensile properties of the modified 13Cr martensitic stainless steels

    Science.gov (United States)

    Mabruri, Efendi; Anwar, Moch. Syaiful; Prifiharni, Siska; Romijarso, Toni B.; Adjiantoro, Bintang

    2016-04-01

    This paper reports the influence of Mo and Ni on the tensile properties of the modified 13Cr martensitic stainless steels in tempered condition. Four steels with different content of Mo and Ni were prepared by induction melting followed by hot forging, quenching and tempering. The experimental results showed that the addition of about 1% and 3% Mo has a beneficial effect to increase both the tensile strength and the elongation of the steels. On the contrary, the addition of about 3% Ni into the martensitic stainless steel results in decreasing of both the tensile strength and the elongation. Among the alloys investigated the 13Cr3Mo type steel exhibited largest tensile strength of 1348 MPa and largest elongation of 12%. The observation on the tensile fractured surfaces by using scanning electron microscope supported these findings.

  11. Hardness distribution and tensile properties in an electron beam weldment of F82H irradiated in HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Oka, H., E-mail: hiroshi_oka@eng.hokudai.ac.jp [Hokkaido University, Sapporo, Hokkaido (Japan); Hashimoto, N. [Hokkaido University, Sapporo, Hokkaido (Japan); Muroga, T. [National Institute for Fusion Science, Toki, Gifu (Japan); Kimura, A. [Kyoto University, Uji, Kyoto (Japan); Sokolov, M.A. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Yamamoto, T. [University of California Santa Barbara, Santa Barbara, CA 93106 (United States); Ohnuki, S. [Hokkaido University, Sapporo, Hokkaido (Japan)

    2014-12-15

    F82H-IEA and its EB-weld joint were irradiated at 573 and 773 K up to 9.6 dpa and the irradiation effect on its mechanical properties and microstructure were investigated. A hardness profile across the weld joint before irradiation showed the hardness in transformed region (TR) was high and especially that in the edge of TR was the highest (high hardness region: HHR) compared to base metal (BM). These hardness distribution was correspond to grain size distribution. After irradiation, hardening in HHR was small compared to other region in the sample. In tensile test, the amount of hardening in yield strength and ultimate tensile strength of F82H EB-weld joint was almost similar to that of F82H-IEA but the fracture position of EB-weld joint was at the boundary of TR and BM. Therefore, the TR/BM boundary is the structural weak point in F82H EB-weld joint after irradiation. As the plastic instability was observed, the dislocation channeling deformation can be expected though the dislocation channel was not observed in this study.

  12. Elastic Sag Property of Low Carbon Martensite Spring Steel

    Institute of Scientific and Technical Information of China (English)

    LI Ye-sheng; CHEN Mi-song; WU Zi-ping; ZHU Yin-lu; DUO Tie-yun

    2004-01-01

    This paper studies the elastic sag resistance of new low-carbon martensite spring steel 35Si2CrVB developed recently and points out that the cause of elastic sag is attributed to cyclic softening of spring steel engendered during its serving,also considers that elastic sag property should be evaluated by dynamic mechanical properties of spring material such as dynamic yield strength σ'0.2, ratio of dynamic yield strength σ'0.2 vs. tensile strength σb (σ'0.2/σb) and ratio of dynamic yield strength σ' 0.2vs. static yield strengthσ0.2 (σ'0.2/σ0. 2 )etc. , which are measured by the cyclic stress-strain curve test. Compared with conventional spring steel 60Si2MnA, 35Si2CrVB has good advantages in both dynamic and static properties, which show it possesses higher elastic sag resistance than 60Si2MnA because of its lath-martensite structure tempering in low temperature different from 60Si2MnA steel's plate martensite structure tempering inmedium temperature. So it can be demonstrated that low carbon martensite spring steel is more appropriate for the demands of spring.

  13. Anomalous kinetics of lath martensite formation in stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Pantleon, Karen;

    2015-01-01

    isochronal cooling that transformation rate maxima occur, which are interrupted by virtually transformation free temperature regions. Microscopy confirms martensite formation after athermal nucleation of clusters followed by their time dependent growth. The observations are interpreted in terms of time...... dependent autocatalytic lath martensite formation followed by mechanical stabilisation of austenite during the transformation process.......The kinetics of lath martensite formation in Fe-17.3 wt-%Cr-7.1 wt-%Ni-1.1 wt-%Al-0.08 wt-%C stainless steel was investigated with magnetometry and microscopy. Lath martensite forms during cooling, heating and isothermally. For the first time, it is shown by magnetometry during extremely slow...

  14. Technical issues related to the development of reduced-activation ferritic/martensitic steels as structural materials for a fusion blanket system

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, Hiroyasu, E-mail: tanigawa.hiroyasu@jaea.go.jp [Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212 (Japan); Shiba, Kiyoyuki; Sakasegawa, Hideo; Hirose, Takanori; Jitsukawa, Shiro [Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212 (Japan)

    2011-10-15

    Reduced activation ferritic/martensitic (RAFM) steels are recognized as the primary candidate structural materials for fusion blanket systems. Because of the possibility of creating sound engineering bases, such as a suitable fabrication technology and a materials database, RAFM steels can be used as structural materials for pressure equipment. Further, the development of an irradiation database in addition to design methodologies for fusion-centered applications is critical when evaluating the applicability of RAFM steels as structural materials for fusion-neutron-irradiated pressure equipment. In the International Fusion Energy Research Centre (IFERC) project in the Broader Approach (BA) activities between the EU and Japan, R and D is underway to optimize RAFM steel fabrication and processing technologies, develop a method for estimating fusion-neutron-irradiation effects, and study the deformation behaviors of irradiated structures. The results of these research activities are expected to form the basis for the DEMO power plant design criteria and licensing. The objective of this paper is to review the BA R and D status of RAFM steel development in Japan, especially F82H (Fe-8Cr-2W-V, Ta). The key technical issues relevant to the design and fabrication of the DEMO blanket and the recent achievements in Japan are introduced.

  15. MARTENSITIC CREEP RESISTANT STEEL STRENGTHENED BY Z-PHASE

    DEFF Research Database (Denmark)

    2008-01-01

    % the following components: 9 to 15% Cr, 0.01-0.20% N, C in an amount less than 0.1%, one or more of: 0.01- 0.5%V,0.01-1%Nb, 0.01-2%Ta, and a balance being substantially iron and inevitable impurities. The invention further relates to a method of manufacturing such a steel alloy, a component comprising......The present invention relates to steel alloys having a martensitic or martensitic- ferritic structure and comprising Z-phase (CrXN) particles, where X is one or more of the elements V, Nb, Ta, and where the Z-phase particles have an average size of less than 400 nm. The alloy comprises by wt...... such a steel alloy, and to the use of such a steel alloy for high temperature components....

  16. Creep behavior of reduced activation ferritic/martensitic steels irradiated at 573 and 773 K up to 5 dpa

    Energy Technology Data Exchange (ETDEWEB)

    Ando, M. [Fusion Structural Materials Development Group, Directorates of Fusion Energy Technology, Fusion Research and Development Directorate, Japan Atomic Energy Agency (JAEA) (Japan)]. E-mail: ando.masami@jaea.go.jp; Li, M. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Tanigawa, H. [Fusion Structural Materials Development Group, Directorates of Fusion Energy Technology, Fusion Research and Development Directorate, Japan Atomic Energy Agency (JAEA) (Japan); Grossbeck, M.L. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); University of Tennessee, Knoxville, TN 37996-2300 (United States); Kim, S. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Sawai, T. [Fusion Structural Materials Development Group, Directorates of Fusion Energy Technology, Fusion Research and Development Directorate, Japan Atomic Energy Agency (JAEA) (Japan); Shiba, K. [Fusion Structural Materials Development Group, Directorates of Fusion Energy Technology, Fusion Research and Development Directorate, Japan Atomic Energy Agency (JAEA) (Japan); Kohno, Y. [Muroran Institute of Technology, Muroran, Hokkaido 050-8585 (Japan); Kohyama, A. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2007-08-01

    The irradiation creep behavior of F82H and several variants of JLF-1 steel has been measured at 573 and 773 K up to 5 dpa using helium-pressurized creep tubes irradiated in HFIR. These tubes were pressurized with helium to hoop stress levels of 0-400 MPa at the irradiation temperature. The results for F82H and JLF-1 with a 400 MPa hoop stress showed small creep strains (<0.25%) after irradiation at 573 K. The irradiation creep strain at 573 K in these steels is linearly dependent on the applied stress at stress levels below 250 MPa. However, at higher hoop stress levels, the creep strain becomes nonlinear. At 773 K, the irradiation creep strain of F82H is linearly dependent on the applied stress level below 100 MPa. At higher stress levels, the creep strain increased strongly. The creep compliance coefficients for F82H and JLF-1 are consistent with the values obtained for other steels. These data contribute to the materials database for ITER test blanket design work.

  17. Microstructural Characterization of Low Temperature Gas Nitrided Martensitic Stainless Steel

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2015-01-01

    The present work presents microstructural investigations of the surface zone of low temperature gas nitrided precipitation hardening martensitic stainless steel AISI 630. Grazing incidence X-ray diffraction was applied to investigate the present phases after successive removal of very thin sections...

  18. Martensite Formation in Partially and Fully Austenitic Plain Carbon Steels

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.; Sietsma, J.

    2009-01-01

    The progress of martensite formation in plain carbon steels Fe-0.46C, Fe-0.66C, and Fe-0.80C has been investigated by dilatometry. It is demonstrated that carbon enrichment of the remaining austenite due to intercritical annealing of Fe-0.46C and Fe-0.66C does not only depress the start temperature

  19. Martensite Formation in Partially and Fully Austenitic Plain Carbon Steels

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.; Sietsma, J.

    2009-01-01

    The progress of martensite formation in plain carbon steels Fe-0.46C, Fe-0.66C, and Fe-0.80C has been investigated by dilatometry. It is demonstrated that carbon enrichment of the remaining austenite due to intercritical annealing of Fe-0.46C and Fe-0.66C does not only depress the start temperature

  20. Influences of cyclic loading on martensite transformation of TRIP steels

    Science.gov (United States)

    Dan, W. J.; Hu, Z. G.; Zhang, W. G.

    2013-03-01

    While austenite transformation into martensite induces increasing of the crack initiation life and restraining of the growth of fatigue cracks in cyclic-loading processes, TRIP-assisted steels have a better fatigue life than the AHSS (Advance High Strength Steels). As two key parameters in the cyclic loading process, strain amplitude and cyclic frequency are used in a kinetic transformation model to reasonably evaluate the phase transformation from austenite into martensite with the shear-band intersections theory, in which strain amplitude and cyclic frequency are related to the rate of shear-band intersection formation and the driving force of phase transformation. The results revealed that the martensite volume fraction increased and the rate of phase transformation decrease while the number of cycles increased, and the martensite volume fraction was almost constant after the number of cycles was more than 2000 times. Higher strain amplitude promotes martensite transformation and higher cyclic frequency impedes phase transformation, which are interpreted by temperature increment, the driving force of phase transformation and the rate of shearband intersection formation.

  1. Influence of Martensite Fraction on the Stabilization of Austenite in Austenitic-Martensitic Stainless Steels

    Science.gov (United States)

    Huang, Qiuliang; De Cooman, Bruno C.; Biermann, Horst; Mola, Javad

    2016-05-01

    The influence of martensite fraction ( f α') on the stabilization of austenite was studied by quench interruption below M s temperature of an Fe-13Cr-0.31C (mass pct) stainless steel. The interval between the quench interruption temperature and the secondary martensite start temperature, denoted as θ, was used to quantify the extent of austenite stabilization. In experiments with and without a reheating step subsequent to quench interruption, the variation of θ with f α' showed a transition after transformation of almost half of the austenite. This trend was observed regardless of the solution annealing temperature which influenced the martensite start temperature. The transition in θ was ascribed to a change in the type of martensite nucleation sites from austenite grain and twin boundaries at low f α' to the faults near austenite-martensite (A-M) boundaries at high f α'. At low temperatures, the local carbon enrichment of such boundaries was responsible for the enhanced stabilization at high f α'. At high temperatures, relevant to the quenching and partitioning processing, on the other hand, the pronounced stabilization at high f α' was attributed to the uniform partitioning of the carbon stored at A-M boundaries into the austenite. Reduction in the fault density of austenite served as an auxiliary stabilization mechanism at high temperatures.

  2. Microstructure of laser cladded martensitic stainless steel

    CSIR Research Space (South Africa)

    Van Rooyen, C

    2006-08-01

    Full Text Available for laser cladding Table 2 - Process parameters for coaxial and off axis powder cladding Material Laser power (W) Speed (m/min) Powder feed rate (kg/h) Carrying gas (Flow rate l/min) Stepove r (mm) Dilution (%) Fe211-1 (420) Off axis... mill industries. Conventional arc welding processes usually result in microstructures consisting of martensite and ferrite. Delta ferrite lowers the hot cracking susceptibility but also reduce the strength, thermal fatigue and corrosion properties...

  3. A phenomenological approach to micromagnetics in martensitic steels

    CERN Document Server

    Tomka, G J; Earl, J; Murray, N; Maylin, M G; Squire, P T

    2000-01-01

    A series of applied field measurements have been done on rods of martensitic steel using a BH-permeameter incorporated into a stress-strain apparatus. Zero stress measurements have been cross-checked using a VSM. For the unstressed steel, it is shown that it is necessary to adapt the Jiles-Atherton model to account for a significant departure in the virgin and demagnetisation curves from that predicted in the standard model. The adapted model gives a good description of magnetisation changes for points on the curve and provides an insight into the reversal mechanism in martensitic steel. Measurements under stress indicate that the nature of the reversal mechanism is stress dependent.

  4. A phenomenological approach to micromagnetics in martensitic steels

    Science.gov (United States)

    Tomka, G. J.; Gore, J. G.; Earl, J.; Murray, N.; Maylin, M. G.; Squire, P. T.

    2000-09-01

    A series of applied field measurements have been done on rods of martensitic steel using a BH-permeameter incorporated into a stress-strain apparatus. Zero stress measurements have been cross-checked using a VSM. For the unstressed steel, it is shown that it is necessary to adapt the Jiles-Atherton model to account for a significant departure in the virgin and demagnetisation curves from that predicted in the standard model. The adapted model gives a good description of magnetisation changes for points on the curve and provides an insight into the reversal mechanism in martensitic steel. Measurements under stress indicate that the nature of the reversal mechanism is stress dependent.

  5. New martensitic steels for fossil power plant: Creep resistance

    Science.gov (United States)

    Kaybyshev, R. O.; Skorobogatykh, V. N.; Shchenkova, I. A.

    2010-02-01

    In this paper, we consider the origin of high-temperature strength of heat-resistant steels belonging to martensitic class developed on the basis of the Fe—9%Cr alloy for the boiler pipes and steam pipelines of power plants at steam temperatures of up to 620°C and pressures to 300 atm. In addition, we give a brief information on the physical processes that determine the creep strength and consider the alloying philosophy of traditional heat-resistant steels. The effect of the chemical and phase composition of heat-resistant steels and their structure on creep strength is analyzed in detail. It is shown that the combination of the solid-solution alloying by elements such as W and Mo, as well as the introduction of carbides of the MX type into the matrix with the formation of a dislocation structure of tempered martensite, ensures a significant increase in creep resistance. The steels of the martensitic class withstand creep until an extensive polygonization starts in the dislocation structure of the tempered martensite(“troostomartensite”), which is suppressed by V(C,N) and Nb(C,N) dispersoids. Correspondingly, the service life of these steels is determined by the time during which the dispersed nanocarbonitrides withstand coalescence, while tungsten and molybdenum remain in the solid solution. The precipitation of the Laves phases Fe2(W,Mo) and the coalescence of carbides lead to the development of migration of low-angle boundaries, and the steel loses its ability to resist creep.

  6. Induced martensitic transformation during tensile test in nanostructured bainitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Rivas, L. [Department of Physical Metallurgy, National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo, 8, 28040 Madrid (Spain); University of Kaiserslautern, Materials Testing, Gottlieb - Daimler - Str., 67663 Kaiserslautern (Germany); Garcia-Mateo, C., E-mail: cgm@cenim.csic.es [Department of Physical Metallurgy, National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo, 8, 28040 Madrid (Spain); Kuntz, Matthias [Robert Bosch GmbH, Materials and Processing Dept, P.O. Box 300240, Stuttgart (Germany); Sourmail, Thomas [Asco Industries CREAS (Research Centre) Metallurgy, BP 70045, Hagondange Cedex 57301 (France); Caballero, F.G. [Department of Physical Metallurgy, National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo, 8, 28040 Madrid (Spain)

    2016-04-26

    Retained austenite in nanostructured bainite is able to undergo mechanically induced martensitic transformation. However, the link between transformation and deformation mechanisms involved makes difficult the understanding of the process. In this work, a model has been developed to assess the effect of the external stress itself on the martensite phase transformation. In addition, after a detailed initial microstructural characterization, the martensite fraction evolution during tensile deformation has been obtained by means of X-ray diffraction analyses after interrupted tensile tests in several nanostructured bainitic steels. Experimental results have been compared to the outputs of the model, as a reference. They suggests that stress partitioning between phases upon tensile deformation is promoted by isothermal transformation at lower temperatures.

  7. Structural and magnetic characterization of martensitic Maraging-350 steel

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, G.C.S. [Universidade Estadual de Maringá, Departamento de Física, Av. Colombo, 5790, 87.020-900, PR (Brazil); Sarvezuk, P.W.C. [Universidade Tecnológica Federal do Paraná, Campo Mourão, PR (Brazil); Biondo, V. [Universidade Estadual de Maringá, Departamento de Física, Av. Colombo, 5790, 87.020-900, PR (Brazil); Blanco, M.C. [Universidad Nacional de Córdoba (Argentina); Nunes, M.V.S. [Universidade Estadual de Maringá, Departamento de Física, Av. Colombo, 5790, 87.020-900, PR (Brazil); Andrade, A.M.H. de [Universidade Federal do Rio Grande do Sul, Instituto de Física, RS (Brazil); Paesano, A., E-mail: paesano@wnet.com.br [Universidade Estadual de Maringá, Departamento de Física, Av. Colombo, 5790, 87.020-900, PR (Brazil)

    2015-10-15

    A solubilized Maraging-350 steel used in the nuclear industry, as received from the manufacturer, was finely characterized by X-ray diffraction (Rietveld refinement), Mössbauer spectroscopy and magnetization techniques. For these characterizations, samples were prepared with exceptional care regarding any possible modification of the physical properties of the steel due to mechanical work done on the original piece during specimen preparation. The results showed that the steel is martensitic, although evidence of a crystallographic distortion from the cubic symmetry usually attributed to the martensite was found. It was also revealed that the atomic configurations of the iron nearest neighbors may be assembled in three groups, according to the hyperfine magnetic field at the iron sites. Magnetic minor loops displayed a soft magnetic material with the coercive field, residual induction and loop area obtained as a function of the maximum applied field in the loop obeying peculiar behaviors. The measured properties represent key information for a suitable control for the aging of Maraging-350 and, consequently, for the design of ultracentrifuges used in the isotope enrichment of nuclear fuel. - Highlights: • We report a fine characterization of the martensitic Maraging-350 steel. • A crystallographic distortion from the cubic symmetry usually attributed to the martensite phase was found. • The atomic configurations of the iron nearest neighbors may be assembled in three groups. • Magnetic minor loops displayed a soft magnetic material with extrinsic parameters obeying peculiar behaviors. • The measured properties represent key information for a suitable control for the aging of Maraging-350 steel.

  8. Strain partitioning in dual-phase steels containing tempered martensite

    Energy Technology Data Exchange (ETDEWEB)

    Han, Qihang, E-mail: hanqihang@baosteel.com [Research Institute, Baoshan Iron and Steel Co., Ltd., Shanghai 201900 (China); State Key Laboratory of Development and Application Technology of Automotive Steels (BaoSteel), Shanghai 201900 (China); Institute for Frontier Materials, Deakin University, Geelong, VIC. 3217 (Australia); Asgari, Alireza; Hodgson, Peter D.; Stanford, Nicole [State Key Laboratory of Development and Application Technology of Automotive Steels (BaoSteel), Shanghai 201900 (China)

    2014-08-12

    Tempering has been used as a method to develop a range of dual phase steels with the same martensite morphology and volume fraction, but containing phases with different relative strengths. These steels were used to examine the strain partitioning between the two constituent phases experimentally through mechanical testing and numerically through finite element modelling. It was found that increasing the differential in strength between the two phases not only produces regions of high strain, but also regions of low strain. On average, a larger difference in strength between the phases increased the strain carried by the softer phase. There was no discernible preferential strain localisation to the ferrite/martensite interface, with the regions of strain localisation being determined by the morphology of the microstructure. A direct correlation between the average strain in the ferrite, and the measured ductility has been found.

  9. Macro and microscale mechanical testing and local electrode atom probe measurements of STIP irradiated F82H, Fe-8Cr ODS and Fe-8Cr-2W ODS

    Energy Technology Data Exchange (ETDEWEB)

    Hosemann, P., E-mail: peterh@lanl.gov [Los Alamos National Laboratory (LANL), MST-8 (United States); University of California Berkeley, Department of Nuclear Engineering (United States); Stergar, E. [University of California Berkeley, Department of Nuclear Engineering (United States); Peng, L. [Paul Scherrer Institute (PSI), 5332 Villigen PSI (Switzerland); Institute of Plasma Physics, Chinese Academy of Science (China); Dai, Y. [Paul Scherrer Institute (PSI), 5332 Villigen PSI (Switzerland); Maloy, S.A. [Los Alamos National Laboratory (LANL), MST-8 (United States); Pouchon, M.A. [Paul Scherrer Institute (PSI), 5332 Villigen PSI (Switzerland); Shiba, K.; Hamaguchi, D. [Japan Atomic Energy Agency (JAEA) (Japan); Leitner, H. [MontanuniversitaetLeoben, Department fuerMetallkunde (Austria)

    2011-10-01

    The reduced activation ferritic/martensitic alloy F82H (Fe-8Cr-2W-0.2V-0.04Ta-0.1C) is being considered as a structural material for several different fusion related nuclear applications. The oxide dispersion strengthened (ODS) alloys Fe-8Cr-2W ODS and Fe-8Cr ODS were developed for better high-temperature strength and radiation tolerance. These materials have been exposed to a neutron and proton environment in the Spallation Target Irradiation Program (STIP) (<13 dpa) with an average He/dpa ratio of 60 appm He/dpa at irradiation temperatures 159-347 deg. C. After irradiation, the samples were tensile tested at different temperatures. The post tensile testing fractured parts were collected and nanoindentation, microcompression testing and local electrode atom probe was conducted. The information gained by local electron atom probe in combination with the micro, nano and macroscopic mechanical tests allows one to establish a fundamental understanding of the relationship between the data measured at different scales on irradiated materials.

  10. Macro and microscale mechanical testing and local electrode atom probe measurements of STIP irradiated F82H, Fe-8Cr ODS and Fe-8Cr-2W ODS

    Science.gov (United States)

    Hosemann, P.; Stergar, E.; Peng, L.; Dai, Y.; Maloy, S. A.; Pouchon, M. A.; Shiba, K.; Hamaguchi, D.; Leitner, H.

    2011-10-01

    The reduced activation ferritic/martensitic alloy F82H (Fe-8Cr-2W-0.2V-0.04Ta-0.1C) is being considered as a structural material for several different fusion related nuclear applications. The oxide dispersion strengthened (ODS) alloys Fe-8Cr-2W ODS and Fe-8Cr ODS were developed for better high-temperature strength and radiation tolerance. These materials have been exposed to a neutron and proton environment in the Spallation Target Irradiation Program (STIP) (<13 dpa) with an average He/dpa ratio of 60 appm He/dpa at irradiation temperatures 159-347 °C. After irradiation, the samples were tensile tested at different temperatures. The post tensile testing fractured parts were collected and nanoindentation, microcompression testing and local electrode atom probe was conducted. The information gained by local electron atom probe in combination with the micro, nano and macroscopic mechanical tests allows one to establish a fundamental understanding of the relationship between the data measured at different scales on irradiated materials.

  11. Deformation behavior of duplex austenite and ε-martensite high-Mn steel

    Directory of Open Access Journals (Sweden)

    Ki Hyuk Kwon, Byeong-Chan Suh, Sung-Il Baik, Young-Woon Kim, Jong-Kyo Choi and Nack J Kim

    2013-01-01

    Full Text Available Deformation and work hardening behavior of Fe–17Mn–0.02C steel containing ε-martensite within the austenite matrix have been investigated by means of in situ microstructural observations and x-ray diffraction analysis. During deformation, the steel shows the deformation-induced transformation of austenite → ε-martensite → α'-martensite as well as the direct transformation of austenite → α'-martensite. Based on the calculation of changes in the fraction of each constituent phase, we found that the phase transformation of austenite → ε-martensite is more effective in work hardening than that of ε-martensite → α'-martensite. Moreover, reverse transformation of ε-martensite → austenite has also been observed during deformation. It originates from the formation of stacking faults within the deformed ε-martensite, resulting in the formation of 6H-long periodic ordered structure.

  12. Metallurgical properties study of reduced activation ferritic/martensitic steels for their application in a fusion reactor; Estudio de las propiedades metalurgicas de los aceros martensticos de activacion reducida para su aplicacion en los reactores de fusion

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Paredes, M. P.

    2007-07-01

    In this work, the metallurgical characterization of two reduced activation ferritic/martensitic steel of last generation, called F-82H-mod and Eurofer'97 has been performed. the aim of this study is to contribute to the knowledge and understanding of the degradation mechanisms and ageing that these materials can suffer during operation at high temperatures with or without the application of the load (creep). In order to fulfill these objectives, the investigations have been carried out in both materials on as-received condition and after thermal ageing treatments in the temperature range from 300 degree centigree to 600 degree centigree for periods up to 1000 h. To achieve the objectives cited, microstructural (optical, SEM, phase extraction, X-ray diffraction and TEM) and mechanical (hardness, tensile, Charpy, Fracture toughness and creep) investigations have been performed. (Author) 58 refs.

  13. In-service thermal ageing of martensitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Tampigny, R.; Molinie, E. [EDF/DIN/CEIDRE (France); Foct, F. [EDF/RD (France); Dignocourt, P. [EDF/DPN/UNIE (France)

    2011-07-01

    Martensitic stainless steels are largely used in Nuclear Power Plants (NPPs) mainly as valve stems, bolts or nuts due to their high mechanical properties and their good resistance to corrosion in primary water. At the end of the eighties, research studies have demonstrated a thermal ageing irreversible embrittlement due to the precipitation of a chromium-rich phase for X6 CrNiCu 17-04, X6 CrNiMo 16.04 and X12 Cr 13 martensitic stainless steels and a semi-empirical modeling has been proposed. Numerous metallurgical examinations have been performed in hot laboratories to consolidate the good correlation between in-service experience and the modeling developed by EDF RD. According to the feedback analysis, thermal ageing embrittlement can appear at different in-service temperatures or do not appear in relation with chemical composition of martensitic stainless steels and end of manufacturing heat treatments associated. A new campaign of metallurgical examinations has been proposed to consolidate previous studies and to contribute to maintenance policy for the next ten years after the third decennial outages for 900 MWe NPP. Influence of real in-service temperatures and end of manufacturing heat treatments have been examined to understand reasons why in some cases thermal ageing embrittlement does not occur or occur with a lowest intensity. These new results have contributed to reinforce EDF RD modeling validity and technical specifications defined in RCC-M for new valve stems, bolts or nuts. (authors)

  14. Microstructural Dependence of Work Hardening Behavior in Martensite-Ferrite Microalloyed Steels

    Science.gov (United States)

    Anand, N.; Sankaran, S.; Madhavan, R.; Suwas, Satyam; Venugopal, P.

    2015-01-01

    Martensite-ferrite microstructures were produced in four microalloyed steels A (Fe-0.44C-Cr-V), B (Fe-0.26C-Cr-V), C (Fe-0.34C-Cr-Ti-V), and D (Fe-0.23C-Cr-V) by intercritical annealing. SEM analysis reveals that steels A and C contained higher martensite fraction and finer ferrite when compared to steels B and D which contained coarser ferrite grains and lower martensite fraction. A network of martensite phase surrounding the ferrite grains was found in all the steels. Crystallographic texture was very weak in these steels as indicated by EBSD analysis. The steels contained negligible volume fraction of retained austenite (approx. 3-6%). TEM analysis revealed the presence of twinned and lath martensite in these steels along with ferrite. Precipitates (carbides and nitrides) of Ti and V of various shapes with few nanometers size were found, particularly in the microstructures of steel B. Work hardening behavior of these steels at ambient temperature was evaluated through modified Jaoul-Crussard analysis, and it was characterized by two stages due to presence of martensite and ferrite phases in their microstructure. Steel A displayed large work hardening among other steel compositions. Work hardening behavior of the steels at a warm working temperature of 540 °C was characterized by a single stage due to the decomposition of martensite into ferrite and carbides at this temperature as indicated by SEM images of the steels after warm deformation.

  15. Physical metallurgy of BATMAN II Ti-bearing martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Pilloni, L.; Attura, F.; Calza-Bini, A.; Santis, G. de; Filacchioni, G. [ENEA, Casaccia (Italy). Dipt. Innovazione; Carosi, A.; Amato, S. [Centro Sviluppo Materiali, Rome (Italy)

    1998-10-01

    Seven laboratory experimental casts of 7-9% Cr Ti-bearing martensitic steels were obtained via VIM process. Plates of 25 mm thickness were produced by hot rolling. On each cast CCT diagrams and critical temperatures were determined. Several austenitizing treatments were performed to study the grain size evolution. The effect of microstructure on impact properties were finally investigated. This paper discusses the role of chemical composition on microstructural and physical properties and shows the beneficial effect either of low-temperature austenitizing or double-austenitizing steps on impact properties. (orig.) 14 refs.

  16. Process Optimization for Friction-Stir-Welded Martensitic Steel

    Science.gov (United States)

    Ghosh, M.; Kumar, K.; Mishra, R. S.

    2012-06-01

    Advanced high-strength M190 steel sheets were joined by friction-stir welding under different tool rotational and traversing speeds. The optical microstructure of the joints exhibited complete martensite and partial martensite at the weld nugget depending on the cooling rate during welding. The first heat-affected zone outside of the weld nugget revealed ferrite-pearlite phase aggregate, and the second heat-affected zone showed a tempered martensitic structure. The interplay of process variables in terms of peak temperature and cooling rate was studied to observe their effect on joint efficiency under shear testing. The peak hardness at weld nugget was close to the parent alloy at an intermediate cooling rate of 294 to 313 K/s. The lowest hardness was observed at the first heat-affected zone for all welded joints. Joint efficiency was dependent on relative quantity of ferrite-pearlite at first heat-affected zone. In that respect, the intermediate temperature to the tune of ~1193 K to 1273 K (~920 °C to 1000 °C) at the weld nugget was found to be beneficial for obtaining an adequate quantity of pearlite at the first heat-affected zone to provide joint efficiency of more than 50 pct of that of parent alloy.

  17. Elucidation of mechanism wear carbon steel with structure of martensite

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2013-04-01

    Full Text Available Purpose. The purpose of the paper is an estimation of degree of metal hardness change for the railway wheel with martensite structure during rolling. Methodology. As strength characteristic the Rockwell hardness is used. Wear tests were conducted in the conditions of normal loading with (10% and without sliding on the test equipment SMTs-2. Parameters of the fine crystalline structure (tetragonality degree of the crystalline grid, dislocation density, scale of coherent scattering regions, and disturbance value of the crystalline grid of second kind are determined by the methods of X-ray structural analysis. Findings. During operation of the railway wheels with different strength level, origin of defects on the wheel thread is caused by simultaneous action of both the friction forces and the cyclically changing loadings. Considering that formation of damage centers is largely determined by the state of metal volumes near the wheel thread, one should expect the differences in friction processes development at high contact stress for the wheels with different strength level and structural state. Originality. During the wear tests softening effect of carbon steel with martensite quenching structure is obtained. Softening effect equaled 3.5–7% from the level of quenched metal hardness. The softening effect is accompanied by the reduction of tetragonality degree of the crystalline structure of martensite, reduction of coherent scattering regions, dislocation density increase and crystalline grid disturbance of the second kind. Practical value. The results point out the necessity for further studies to clarify the resulted softening effect mechanism.

  18. A Transmission Electron Microscopy Study of Plate Martensite Formation in High-carbon Low Alloy Steels

    Institute of Scientific and Technical Information of China (English)

    Albin Stormvinter; Peter Hedstr(o)m; Annika Borgenstam

    2013-01-01

    The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope.It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon (C) steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel.In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure,while large martensite units are more inhomogeneous.In addition,the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units,e.g.kink or wedge couplings.Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented.Moreover,whether the schematic view can be applied to plate martensite formation in general,is discussed.

  19. Enhanced mechanical stability of ultrafine grained steel through intercritical annealing cold rolled martensite

    Institute of Scientific and Technical Information of China (English)

    Huifang LAN; Xianghua LIU; Linxiu DU

    2012-01-01

    The ultrafine grained ferritic steels possess high strength but low ductility due to the shortage of work hardening.Fine grained ferrite-martensite dual phase microstructure was obtained in a microalloyed steel and low carbon steels through intercritical annealing of the cold rolled martensite.The dual phase microstructure was uniform and the ferrite grain size was smaller in the microalloyed steel resulted from the pinning effect of microalloyed precipitates.But ferrite grown apparently and the volume fraction of the martensite was much higher without the addition of microalloying elements.By introducing martensite into the fine grained ferrite,the work hardening was effectively improved,leading to better mechanical stability.As a result of the fine ferrite grain size as well as uniform distribution of the martensite,the work hardening was enhanced,showing better strength-ductility balance in the microalloyed dual phase steel.

  20. Effect of hardness of martensite and ferrite on void formation in dual phase steel

    DEFF Research Database (Denmark)

    Azuma, M.; Goutianos, Stergios; Hansen, Niels;

    2012-01-01

    The influence of the hardness of martensite and ferrite phases in dual phase steel on void formation has been investigated by in situ tensile loading in a scanning electron microscope. Microstructural observations have shown that most voids form in martensite by evolving four steps: plastic...... deformation of martensite, crack initiation at the martensite/ferrite interface, crack propagation leading to fracture of martensite particles and void formation by separation of particle fragments. It has been identified that the hardness effect is associated with the following aspects: strain partitioning...... between martensite and ferrite, strain localisation and critical strain required for void formation. Reducing the hardness difference between martensite and ferrite phases by tempering has been shown to be an effective approach to retard the void formation in martensite and thereby is expected to improve...

  1. Martensitic transformation during fatigue testing of an AISI 301LN steel

    OpenAIRE

    Mateo García, Antonio Manuel; Fargas Ribas, Gemma

    2012-01-01

    The plastic deformation accumulated during fatigue testing can induce the transformation of austenite to martensite in metastable austenitic stainless steels. To analyze this issue, a metastable austenitic stainless steel grade AISI 301 LN was studied in two different conditions, i.e. annealed and cold rolled. In the first case, the steel was fully austenitic, whereas cold rolled material had almost 30% of martensite. High cycle fatigue tests at a stress ratio of 0.8 were carried out on flat ...

  2. MARTENSITE TRANSFORMATION MICROSTRUCTURE OF 40Cr STEEL COMPLEXLY INDUCED BY LASER SHOCK

    Institute of Scientific and Technical Information of China (English)

    CHEN Ruifang; HUA Yinqun; CAI Lan

    2007-01-01

    40Cr steel is laser quenched by the NEL-2500A rapidly axial flow CO2 laser. Then the martensite induced by laser quenched is shocked by Nd:YAG laser again. Through comparing and analyzing the appearance and size ofmartensite, the dislocation density in microstructure between the treated zones by laser quenched and by laser quenched plus laser shock, the following results are shown: The second martensite obtained by laser compound treatment is more finer compared with those obtained by laser quenched; In the hardened zones obtained by compound treatment, a lot of slender second twin crystal martensites are induced; A lot of more high density dislocation tangles and cellular dislocations are generated. From the transmission electron microscope (TEM) micrograph after compound treatment, there are not only long lath and short nubbly martensites arranged in cross direction, but also massive nubbly and small short nubbly martensites arranged in longitudinal direction. Some martensites look like the broken blocks of quenched martensites. These new martensites are inserted transversely in the quenched martensites with large tangle. And they make quenched martensites break into pieces. Compared with the quenched martensites, the size of fresh martensites are smaller, about 0.3~0.5 μm.

  3. Deformation induced martensite in AISI 316 stainless steel

    Directory of Open Access Journals (Sweden)

    Solomon, N.

    2010-04-01

    Full Text Available The forming process leads to a considerable differentiation of the strain field within the billet, and finally causes the non-uniform distribution of the total strain, microstrusture and properties of the material over the product cross-section. This paper focus on the influence of stress states on the deformation-induced a’ martensitic transformation in AISI Type 316 austenitic stainless steel. The formation of deformation-induced martensite is related to the austenite (g instability at temperatures close or below room temperature. The structural transformation susceptibility is correlated to the stacking fault energy (SFE, which is a function not only of the chemical composition, but also of the testing temperature. Austenitic stainless steels possess high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Nevertheless, the deformation-induced martensite transformation may enhance the rate of work-hardening and it may or may not be in favour of further material processing. Due to their high corrosion resistance and versatile mechanical properties the austenitic stainless steels are used in pressing of heat exchanger plates. However, this corrosion resistance is influenced by the amount of martensite formed during processing. In order to establish the links between total plastic strain, and martensitic transformation, the experimental tests were followed by numerical simulation.

    El proceso de conformación da a lugar a una considerable diferenciación del campo de tensiones dentro de una barra de extrusión y, finalmente, causa una distribución no uniforme de la tensión total, la microestructura y propiedades del material sobre el corte transversal. En este trabajo se estudia la influencia de los estados de tensión sobre la transformación martensítica inducida por deformación en un acero inoxidable austenítico tipo AISI 316. La formación de martensita inducida por

  4. Microstructure and mechanical property in heat affected zone (HAZ in F82H jointed with SUS316L by fiber laser welding

    Directory of Open Access Journals (Sweden)

    S. Kano

    2016-12-01

    Full Text Available This study investigates the microstructure and mechanical property in heat affected zone (HAZ between F82H and SUS316L jointed by 4 kW fiber laser welding at different parameters such as laser scan rate and beam position. OM/FE-SEM observation, EPMA analysis and nano-indentation hardness test were utilized to characterize the microstructure and evaluate the mechanical property. Results show that the HAZ width is dependent on the welding condition. The precipitation of M23C6 particle in HAZ is found to be closely related to the distance from WM/HAZ interface. Decrease in Cr and C concentration in M23C6 depended on the welding condition; the decrease was relatively milder in the case of shifting the beam position to SUS side. Furthermore, the rapid increment in nano-indentation hardness, i.e. ≈2500 MPa, at HAZ/F82H interface was observed regardless of welding parameters. The temperatures at HAZ/F82H interface were estimated from Cr and C concentration change of M23C6 by EPMA. It was revealed that the temperature of HAZ/F82H interface increased with increasing HAZ width, and that the presence of over-tempered HAZ (THAZ region is confirmed only in the specimens welded right on the F82H/SUS interface (no-shift at the laser scan rate of 3 m/min.

  5. Compatibility tests on steels in molten lead and lead-bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Fazio, C. E-mail: concetta@netbra.brasimone.enea.it; Benamati, G.; Martini, C.; Palombarini, G

    2001-07-01

    The compatibility of steels with liquid lead and liquid lead-bismuth is a critical issue for the development of accelerator-driven system (ADS). In this work the results of a set of preliminary tests carried out in stagnant molten lead at 737 K and in lead-bismuth at 573, 673 and 749 K are summarised. The tests were conducted for 700, 1200, 1500 and 5000 h. Three steels were tested: two martensitic steels (mod. F82H and MANET II) and one austenitic steel (AISI 316L). The martensitic steels underwent oxidation phenomena at the higher testing temperature, due to oxygen dissolved in the melts. At a lower test temperature (573 K) and higher exposure time (5000 h) the oxidation rate of the martensitic steel seems to be lower and the developed oxide layer protective against liquid metal corrosion. The austenitic steel, in turn, exhibited an acceptable resistance to corrosion-oxidation under the test conditions.

  6. KINETICS OF α'-MARTENSITE FORMATION DURING FATIGUE DEFORMATION IN METASTABLE AUSTENITIC STAINLESS STEEL

    OpenAIRE

    Tsuzaki, K.; T. Maki; Tamura, I.

    1982-01-01

    The effect of applied total strain range on the critical condition necessary for the onset of α'-martensitic transformation kinetics during the fatigue deformation was studied in AISI type 304 metastable austenitic stainless steel at room temperature. In the case of fatigue deformation, the α'-martensite formation was observed even in the condition that the saturated stress amplitude of austenite phase is smaller than the critical applied stress for the onset of α'-martensite formation for th...

  7. Laser milling of martensitic stainless steels using spiral trajectories

    Science.gov (United States)

    Romoli, L.; Tantussi, F.; Fuso, F.

    2017-04-01

    A laser beam with sub-picosecond pulse duration was driven in spiral trajectories to perform micro-milling of martensitic stainless steel. The geometry of the machined micro-grooves channels was investigated by a specifically conceived Scanning Probe Microscopy instrument and linked to laser parameters by using an experimental approach combining the beam energy distribution profile and the absorption phenomena in the material. Preliminary analysis shows that, despite the numerous parameters involved in the process, layer removal obtained by spiral trajectories, varying the radial overlap, allows for a controllable depth of cut combined to a flattening effect of surface roughness. Combining the developed machining strategy to a feed motion of the work stage, could represent a method to obtain three-dimensional structures with a resolution of few microns, with an areal roughness Sa below 100 nm.

  8. A master curve analysis of F82H using statistical and constraint loss size adjustments of small specimen data

    Science.gov (United States)

    Odette, G. R.; Yamamoto, T.; Kishimoto, H.; Sokolov, M.; Spätig, P.; Yang, W. J.; Rensman, J.-W.; Lucas, G. E.

    2004-08-01

    We assembled a fracture toughness database for the IEA heat of F82H based on a variety of specimen sizes with a nominal ASTM E1921 master curve (MC) reference temperature T0=-119±3 °C. However, the data are not well represented by a MC. T0 decreases systematically with a decreasing deformation limit Mlim starting at ≈200, which is much higher than the E1921 censoring limit of 30, indicating large constraint loss in small specimens. The small scale yielding T0 at high Mlim is ≈98±5 °C. While, the scatter was somewhat larger than predicted, after model-based adjustments for the effects of constraint loss, the data are in reasonably good agreement with a MC with T0=-98 °C. This supports to use of MC methods to characterize irradiation embrittlement, as long as both constraint loss and statistical size effects are properly accounted for. Finally, we note various issues, including sources of the possible excess scatter, which remain to be fully assessed.

  9. A master curve analysis of F82H using statistical and constraint loss size adjustments of small specimen data

    Energy Technology Data Exchange (ETDEWEB)

    Odette, G.R. E-mail: odette@engineering.ucsb.edu; Yamamoto, T.; Kishimoto, H.; Sokolov, M.; Spaetig, P.; Yang, W.J.; Rensman, J.-W.; Lucas, G.E

    2004-08-01

    We assembled a fracture toughness database for the IEA heat of F82H based on a variety of specimen sizes with a nominal ASTM E1921 master curve (MC) reference temperature T{sub 0}=-119{+-}3 deg. C. However, the data are not well represented by a MC. T{sub 0} decreases systematically with a decreasing deformation limit M{sub lim} starting at {approx}200, which is much higher than the E1921 censoring limit of 30, indicating large constraint loss in small specimens. The small scale yielding T{sub 0} at high M{sub lim} is {approx}98{+-}5 deg. C. While, the scatter was somewhat larger than predicted, after model-based adjustments for the effects of constraint loss, the data are in reasonably good agreement with a MC with T{sub 0}=-98 deg. C. This supports to use of MC methods to characterize irradiation embrittlement, as long as both constraint loss and statistical size effects are properly accounted for. Finally, we note various issues, including sources of the possible excess scatter, which remain to be fully assessed.

  10. Thermally activated growth of lath martensite in Fe–Cr–Ni–Al stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Pantleon, Karen

    2015-01-01

    The austenite to martensite transformation in a semi-austenitic stainless steel containing 17 wt-%Cr, 7 wt-%Ni and 1 wt-%Al was investigated with vibrating sample magnetometry and electron backscatter diffraction. Magnetometry demonstrated that, within experimental accuracy, martensite formation...

  11. Martensitic transformation and stress partitioning in a high-carbon steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Grumsen, Flemming Bjerg; Pantleon, Karen;

    2012-01-01

    Martensitic transformation in a high-carbon steel was investigated with (synchrotron) X-ray diffraction at sub-zero Celsius temperature. In situ angular X-ray diffraction was applied to: (i) quantitatively determine the fractions of retained austenite and martensite; and (ii) measure the evolution...

  12. Nanosized MX Precipitates in Ultra-Low-Carbon Ferritic/Martensitic Heat-Resistant Steels

    Science.gov (United States)

    Yin, Feng-Shi; Jung, Woo-Sang

    2009-02-01

    Nanosized MX precipitates in ultra-low-carbon ferritic/martensitic heat-resistant 9Cr-W-Mo-VNbTiN steels were characterized by transmission electron microscope (TEM) using carbon film replicas. The steels were prepared by vacuum induction melting followed by hot forging and rolling into plates. The plates were normalized at 1100 °C for 1 hour, cooled in air, and tempered at 700 °C for 1 hour. The results show that bimodal nanosized MX precipitates distribute densely and homogeneously in the matrix within martensitic lath after normalizing-and-tempering heat treatment. The larger nanosized MX precipitates with the size of 30 to 50 nm are rich in Nb, while the smaller ones with the size of about 10 nm contain less Nb but more V. Small addition of Ti causes an increase in the number of the larger nanosized MX precipitates. The total number density of the nanosized MX precipitates in the ultra-low-carbon ferritic/martensitic steels is measured to be over 300/ μm2, much higher than that in conventional ferritic/martensitic steels. Short-term creep test results show that the ultra-low-carbon ferritic/martensitic steels with high dense nanosized MX precipitates have much higher creep rupture strength than conventional ASME-P92 steel. The strength degradation of the ultra-low-carbon ferritic/martensitic heat-resistant steels during creep is also discussed in this article.

  13. Prospects for Martensitic 12 % Cr Steels for Advanced Steam Power Plants

    DEFF Research Database (Denmark)

    Hald, John

    2016-01-01

    Creep strength improvements of martensitic 9 % Cr steels have been obtained by controlled additions of V, Nb, N and B to the steels, which resulted in precipitation hardening by fine stable nitrides based on V and Nb as well as in stabilization of Cr carbides against coarsening. The best steels P...

  14. Martensitic/ferritic steels as container materials for liquid mercury target of ESS

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Y. [Paul Scherrer Institut, Villigen (Switzerland)

    1996-06-01

    In the previous report, the suitability of steels as the ESS liquid mercury target container material was discussed on the basis of the existing database on conventional austenitic and martensitic/ferritic steels, especially on their representatives, solution annealed 316 stainless steel (SA 316) and Sandvik HT-9 martensitic steel (HT-9). Compared to solution annealed austenitic stainless steels, martensitic/ferritic steels have superior properties in terms of strength, thermal conductivity, thermal expansion, mercury corrosion resistance, void swelling and irradiation creep resistance. The main limitation for conventional martensitic/ferritic steels (CMFS) is embrittlement after low temperature ({le}380{degrees}C) irradiation. The ductile-brittle transition temperature (DBTT) can increase as much as 250 to 300{degrees}C and the upper-shelf energy (USE), at the same time, reduce more than 50%. This makes the application temperature range of CMFS is likely between 300{degrees}C to 500{degrees}C. For the present target design concept, the temperature at the container will be likely controlled in a temperature range between 180{degrees}C to 330{degrees}C. Hence, CMFS seem to be difficult to apply. However, solution annealed austenitic stainless steels are also difficult to apply as the maximum stress level at the container will be higher than the design stress. The solution to the problem is very likely to use advanced low-activation martensitic/ferritic steels (LAMS) developed by the fusion materials community though the present database on the materials is still very limited.

  15. Superstrength of nanograined steel with nanoscale intermetallic precipitates transformed from shock-compressed martensitic steel

    Science.gov (United States)

    Yu, Hailiang; Yan, Ming; Lu, Cheng; Tieu, Anh Kiet; Li, Huijun; Zhu, Qiang; Godbole, Ajit; Li, Jintao; Su, Lihong; Kong, Charlie

    2016-11-01

    An increasing number of industrial applications need superstrength steels. It is known that refined grains and nanoscale precipitates can increase strength. The hardest martensitic steel reported to date is C0.8 steel, whose nanohardness can reach 11.9 GPa through incremental interstitial solid solution strengthening. Here we report a nanograined (NG) steel dispersed with nanoscale precipitates which has an extraordinarily high hardness of 19.1 GPa. The NG steel (shock-compressed Armox 500T steel) was obtained under these conditions: high strain rate of 1.2 μs-1, high temperature rise rate of 600 Kμs-1 and high pressure of 17 GPa. The mean grain size achieved was 39 nm and reinforcing precipitates were indexed in the NG steel. The strength of the NG steel is expected to be ~3950 MPa. The discovery of the NG steel offers a general pathway for designing new advanced steel materials with exceptional hardness and excellent strength.

  16. Kinetics of anomalous multi-step formation of lath martensite in steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Pantleon, Karen; Reich, Michael

    2014-01-01

    A steel containing 16wt.% Cr, 5wt.% Ni and 3wt.% Cu was transformed into martensite by applying isochronal, i.e. constant rate, cooling followed by isothermal holding. The formation of martensite was monitored with dilatometry. A series of retardations and accelerations of the transformation...... was of lath type, and to investigate the microstructure of the material. No influence of the cooling rate on the scale of the microstructure was observed. The series of retardations and accelerations of the transformation is interpreted in terms of the combined effect of the strain and interfacial energy...... introduced in the system during martensite formation, which stabilizes austenite, and autocatalytic nucleation of martensite....

  17. Effects of Strain Rate and Plastic Work on Martensitic Transformation Kinetics of Austenitic Stainless Steel 304

    Institute of Scientific and Technical Information of China (English)

    Fang PENG; Xiang-huai DONG; Kai LIU; Huan-yang XIE

    2015-01-01

    The martensitic transformation behavior and mechanical properties of austenitic stainless steel 304 were studied by both experiments and numerical simulation. Room temperature tensile tests were carried out at various strain rates to investigate the effect on volume fraction of martensite, temperature increase and flow stress. The results show that with increasing strain rate, the local temperature increases, which suppresses the transformation of martensite. To take into account the dependence on strain level, strain rate sensitivity and thermal effects, a kinetic model of martensitic transformation was proposed and constitutive modeling on stress-strain response was conducted. The validity of the proposed model has been proved by comparisons between simulation results and experimental ones.

  18. Application of martensitic, modified martensitic and duplex stainless steel bar stock for completion equipment

    Energy Technology Data Exchange (ETDEWEB)

    Bhavsar, R.B. [CAMCO Products and Services, Houston, TX (United States); Montani, R. [Foroni, S.p.A., Colombo (Italy)

    1998-12-31

    Martensitic and duplex stainless steel tubing are commonly used for oil and gas applications containing CO{sub 2}. Completion equipment manufacturing requires use of solid round bar or heavy wall hollows. Material properties for this stock are not identical in all cases. Material properties as well as corrosion characteristics are discussed for 13Cr, 13Cr-5Ni-2Mo and 25Cr alloys. Corrosion testing of modified or Enhanced 13Cr solid bar stock, UNS S41425 and other compositions in H{sub 2}S-Cl{sup {minus}} and pH is reported in coupled and uncoupled condition. Corrosion testing of various super duplex bar stock at various H{sub 2}S-chlorides and temperature in CO{sub 2} environment is reported. Impact value requirements, welding issues and special consideration required for these alloys for completion equipment is discussed. Modified 13Cr and Super Duplex Oil Country Tubular Goods (OCTG) are readily available, however, availability of completion equipment raw material compatible with these OCTG is limited.

  19. Results of investigations regarding the physical and mechanical properties of the martensitic 9% Cr steel EUROFER '97; Ergebnisse von Charakterisierungsuntersuchungen zu physikalischen und mechanischen Eigenschaften des martensitischen 9% Cr-Stahles EUROFER '97

    Energy Technology Data Exchange (ETDEWEB)

    Schirra, M.; Falkenstein, A.; Graf, P.; Heger, S.; Kempe, H.; Lindau, R.; Zimmermann, H.

    2002-04-01

    Following the history of the development activities from conventional martensitic 12% Cr steel, MANET and OPTIFER up to low-activated EUROFER (RAFM steel), the results obtained from experiments on rods of 100 mm diameter and plates of 14 mm shall be presented for a basic characterization. The physical and mechanical properties shall be compared with those of OPTIFER-1W and the F82H-mod 2% W steel. To determine the conversion behavior, a continuous cct diagram was plotted. Hardening experiments in the temperature range of 850 - 1120 C illustrated the range of maximum hardness as well as grain size development. The notch impact behavior was described for various heat treatments and sample types at test temperatures ranging from +60 to -100 C. Tensile strengths were determined for various heat treatments at temperatures ranging from room temperature to 700 C. Aging due to a long-term heat treatment was investigated by means of stabilization annealing experiments. Creep rupture strength and creeping were investigated in the temperature range of 450 - 650 C. So far, a duration of up to about 15 000 h has been covered by the experiments. (orig.)

  20. Study on microstructures and work hardening behavior of ferrite-martensite dual-phase steels with high-content martensite

    Directory of Open Access Journals (Sweden)

    Xiurong Zuo

    2012-12-01

    Full Text Available A kind of medium-carbon low-alloy dual-phase steels with high-content martensite produced by intercritical annealing at 785-830 ºC for 10-50 minutes were studied in aspect of microstructures and work hardening behavior using SEM and tensile testing machine. The experimental results showed that the work hardening of the studied steels obeyed the two-stage work hardening mechanism, whose work hardening exponent of the first stage was higher than that of the second stage. The work hardening exponent increased with increasing the intercritical annealing temperature and time. For series A steel intercritically annealed at 785 ºC with starting microstructure of ferrite plus pearlite, austenite nucleated at the pearlite colonies, so the holding time of only 50 minutes can increase the work hardening exponent obviously. For series B steel with starting microstructure of martensite, austenite nucleated at lath interfaces, lath colony boundaries of primary martensite and carbides, accelerating the formation of austenite, so holding time for 30 minutes made the work hardening exponent increase obviously. High work hardening rate during initial plastic deformation (<0.5% strain was observed.

  1. Proceedings of the IEA Working Group meeting on ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.

    1996-12-31

    An IEA working group on ferritic/martensitic steels for fusion applications, consisting of researchers from Japan, European Union, USA, and Switzerland, met at the headquarters of the Joint European Torus, Culham, UK. At the meeting, preliminary data generated on the large heats of steels purchased for the IEA program and on other heats of steels were presented and discussed. Second purpose of the meeting was to continue planning and coordinating the collaborative test program in progress on reduced-activation ferritic/martensitic steels. The majority of this report consists of viewographs for the presentations.

  2. Mechanical properties of steels with a microstructure of bainite/martensite and austenite islands

    Science.gov (United States)

    Syammach, Sami M.

    Advanced high strength steels (AHSS) are continually being developed in order to reduce weight and improve safety for automotive applications. There is need for economic steels with improved strength and ductility combinations. These demands have led to research and development of third generation AHSS. Third generation AHSS include steel grades with a bainitic and tempered martensitic matrix with retained austenite islands. These steels may provide improved mechanical properties compared to first generation AHSS and should be more economical than second generation AHSS. There is a need to investigate these newer types of steels to determine their strength and formability properties. Understanding these bainitic and tempered martensitic steels is important because they likely can be produced using currently available production systems. If viable, these steels could be a positive step in the evolution of AHSS. The present work investigates the effect of the microstructure on the mechanical properties of steels with a microstructure of bainite, martensite, and retained austenite, so called TRIP aided bainitic ferrite (TBF) steels. The first step in this project was creating the desired microstructure. To create a microstructure of bainite, martensite, and austenite an interrupted austempering heat treatment was used. Varying the heat treatment times and temperatures produced microstructures of varying amounts of bainite, martensite, and austenite. Mechanical properties such as strength, ductility, strain hardening, and hole-expansion ratios were then evaluated for each heat treatment. Correlations between mechanical properties and microstructure were then evaluated. It was found that samples after each of the heat treatments exhibited strengths between 1050 MPa and 1350 MPa with total elongations varying from 8 pct to 16 pct. By increasing the bainite and austenite volume fraction the strength of the steel was found to decrease, but the ductility increased. Larger

  3. Evaluation of the transformation mechanisms and mechanical properties of ferrite: martensite microalloyed steels

    Directory of Open Access Journals (Sweden)

    Ovri Henry

    2008-03-01

    Full Text Available The influence of starting point microstructures on the transformation mechanisms and mechanical properties of a micro alloyed steel after annealing in the alpha + gamma region have been investigated. Three different microstructures: austenite, pearlite in a ferrite matrix and martensite were used as starting point microstructures for the production of dual (alpha + phase structures in the test steel. Photomicrographs obtained from metallographic examination of the heat treated samples were used as criteria for the assessment of results obtained from impact toughness and hardness testing. The results obtained showed that the transformation mechanisms and hence the morphology of ferrite - martensite microalloyed steels are strongly influenced by their initial microstructural details. Ferrite - martensite structures produced via the intercritical quench (IQ treatment, with martensite as the starting point microstructure, have the best combination of hardness and impact energy.

  4. Martensitic stainless steel seamless linepipe with superior weldability and CO{sub 2} corrosion resistance

    Energy Technology Data Exchange (ETDEWEB)

    Miyata, Y.; Kimura, M.; Koseki, T.; Toyooka, T.; Murase, F. [Kawasaki Steel Corp., Handa, Aichi (Japan)

    1997-08-01

    Two types of new martensitic stainless steel with good weldability and superior corrosion resistance have been developed for line pipe application. Both steels are suitable for welding without preheating owing to lowering C and N contents, and they show good low temperature toughness in welds without PWHT. One is applied to sweet environments. It gives better resistance to CO{sub 2} corrosion than the 13Cr martensitic stainless steel for OCTG. Lowering C and addition of Ni contribute to reduction of general corrosion rate in the CO{sub 2} environment. The addition of Cu improves the pitting resistance. The other is applied to light sour environments. It gives good SSC resistance in welds owing to the improvement of the pitting resistance due to Mo addition. The seamless pipes of these martensitic stainless steels are applicable as substitutes for a part of duplex stainless steel flow lines.

  5. A study on fatigue crack growth in dual phase martensitic steel in air environment

    Indian Academy of Sciences (India)

    K V Sudhakar; E S Dwarakadasa

    2000-06-01

    Dual phase (DP) steel was intercritically annealed at different temperatures from fully martensitic state to achieve martensite plus ferrite, microstructures with martensite contents in the range of 32 to 76%. Fatigue crack growth (FCG) and fracture toughness tests were carried out as per ASTM standards E 647 and E 399, respectively to evaluate the potential of DP steels. The crack growth rates (/) at different stress intensity ranges ( ) were determined to obtain the threshold value of stress intensity range ( th). Crack path morphology was studied to determine the influence of microstructure on crack growth characteristics. After the examination of crack tortuosity, the compact tension (CT) specimens were pulled in static mode to determine fracture toughness values. FCG rates decreased and threshold values increased with increase in vol.% martensite in the DP steel. This is attributed to the lower carbon content in the martensite formed at higher intercritical annealing (ICA) temperatures, causing retardation of crack growth rate by crack tip blunting and/or deflection. Roughness induced crack closure was also found to contribute to the improved crack growth resistance at higher levels of martensite content. Scanning electron fractography of DP steel in the near threshold region revealed transgranular cleavage fracture with secondary cracking. Results indicate the possibility that the DP steels may be treated to obtain an excellent combination of strength and fatigue properties.

  6. Materials design data for reduced activation martensitic steel type EUROFER

    Science.gov (United States)

    Tavassoli, A.-A. F.; Alamo, A.; Bedel, L.; Forest, L.; Gentzbittel, J.-M.; Rensman, J.-W.; Diegele, E.; Lindau, R.; Schirra, M.; Schmitt, R.; Schneider, H. C.; Petersen, C.; Lancha, A.-M.; Fernandez, P.; Filacchioni, G.; Maday, M. F.; Mergia, K.; Boukos, N.; Baluc; Spätig, P.; Alves, E.; Lucon, E.

    2004-08-01

    Materials design limits derived so far from the data generated in Europe for the reduced activation ferritic/martensitic (RAFM) steel type Eurofer are presented. These data address the short-term needs of the ITER Test Blanket Modules and a DEMOnstration fusion reactor. Products tested include plates, bars, tubes, TIG and EB welds, as well as powder consolidated blocks and solid-solid HIP joints. Effects of thermal ageing and low dose neutron irradiation are also included. Results are sorted and screened according to design code requirements before being introduced in reference databases. From the physical properties databases, variations of magnetic properties, modulus of elasticity, density, thermal conductivity, thermal diffusivity, specific heat, mean and instantaneous linear coefficients of thermal expansion versus temperature are derived. From the tensile and creep properties databases design allowable stresses are derived. From the instrumented Charpy impact and fracture toughness databases, ductile to brittle transition temperature, toughness and behavior of materials in different fracture modes are evaluated. From the fatigue database, total strain range versus number of cycles to failure curves are plotted and used to derive fatigue design curves. Cyclic curves are also derived and compared with monotonic hardening curves. Finally, irradiated and aged materials data are compared to ensure that the safety margins incorporated in unirradiated design limits are not exceeded.

  7. Recrystallization and formation of austenite in deformed lath martensitic structure of low carbon steels

    Science.gov (United States)

    Tokizane, M.; Matsumura, N.; Tsuzaki, K.; Maki, T.; Tamura, I.

    1982-08-01

    The effect of prior deformation on the processes of tempering and austenitizing of lath martensite was studied by using low carbon steels. The recrystallization of as-quenched lath martensite was not observed on tempering while the deformed lath martensite easily recrystallized. The behavior of austenite formation in deformed specimens was different from that in as-quenched specimens because of the recrystallization of deformed lath martensite. The austenitizing behavior (and thus the austenite grain size) in deformed specimens was controlled by the competition of austenite formation with the recrystallization of lath martensite. In the case of as-quenched (non-deformed) lath martensite, the austenite particles were formed preferentially at prior austenite grain boundaries and then formed within the austenite grains mainly along the packet, block, and lath boundaries. On the other hand, in the case of lightly deformed (30 to 50 pct) lath martensite, the recrystallization of the matrix rapidly progressed prior to the formation of austenite, and the austenite particles were formed mainly at the boundaries of fairly fine recrystallized ferrite grains. When the lath martensite was heavily deformed (75 to 84 pct), the austenite formation proceeded almost simultaneously with the recrystallization of lath martensite. In such a situation, very fine austenite grain structure was obtained most effectively.

  8. Corrosion performance of martensitic stainless steel seamless pipe for linepipe application

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Mitsuo; Miyata, Yukio; Toyooka, Takaaki; Murase, Fumio [Kawasaki Steel Corp., Handa, Aichi (Japan)

    1999-11-01

    The corrosion performance of two types of weldable martensitic stainless steel seamless pipe for pipeline application is investigated. 11Cr steel pipe developed for sweet environment gives better resistance to CO{sub 2} corrosion than the 13Cr martensitic stainless steel for OCTG. 12Cr steel pipe developed for light sour environment shows good SSC resistance in a mild sour environment and superior CO{sub 2} corrosion resistance at high temperature and high CO{sub 2} partial pressure condition. The suitable condition for the 11Cr steel pipe and the 12Cr steel pipe in sweet environment, and the critical pH and H{sub 2}S partial pressure for the 12Cr steel pipe welded joint in sour environment are clarified. Both welded joints have superior resistance to hydrogen embrittlement under the cathodic protection condition in sea water.

  9. Martensitic Transformation during Fatigue Testing of an AISI 301LN Stainless Steel

    Science.gov (United States)

    Mateo, A.; Fargas, G.; Zapata, A.

    2012-02-01

    The plastic deformation accumulated during fatigue testing can induce the transformation of austenite to martensite in metastable austenitic stainless steels. To analyze this issue, a metastable austenitic stainless steel grade AISI 301 LN was studied in two different conditions, i.e. annealed and cold rolled. In the first case, the steel was fully austenitic, whereas cold rolled material had almost 30% of martensite. High cycle fatigue tests at a stress ratio of 0.8 were carried out on flat specimens from both steel conditions. Several characterization techniques, including optical microscopy, X-ray diffraction (XRD) and electron back scattered diffraction (EBSD), were used to detect and quantify the martensite induced by the cyclic deformation.

  10. Crystallographic similarity between the lath martensite and lower bainite in medium-carbon alloy steels

    Institute of Scientific and Technical Information of China (English)

    LIU Jiangwen; LUO Chengping; WU Dongxiao

    2005-01-01

    Progress in the crystallography of lath martensitic and lower bainitic transformations is briefly reviewed, followed by a presentation of the experimentally measured crystallographic characteristics of both lath martensite and lower bainite formed in mediumcarbon steels containing Si, Mn and Mo. It is found that the bainite plates relate to each other by a relative rotation of 54.7°or 60°about the normal to their common close-packed planes {110} b, which ensures a pseudo- {112}b twin relationship between two adjacent plates,and that all bainite variants formed in a single packet keep a unique G-T orientation relationship with the austenite matrix. These two types of OR of lower bainite are similar to that of the lath martensite, respectively. Furthermore, the measured habit planes of both the lower bainite and lath martensite are all {335} f type, which can verify the crystallographic similarity between the lath martensite and lower bainite.

  11. A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

    Science.gov (United States)

    Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan

    2015-06-01

    In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

  12. Texture analysis of deformation induced martensite in an AISI 301L stainless steel: microtexture and macrotexture aspects

    OpenAIRE

    Hamilton Ferreira Gomes de Abreu; Marcelo José Gomes da Silva; Luís Flávio Gaspar Herculano; Harry Bhadeshia

    2009-01-01

    Experiments have been conducted to study the strain induced transformation from austenite to martensite in a metastable AISI 301LN austenitic stainless steel, deformed by uniaxial tension applied along rolling direction. Samples deformed 10 and 20% have shown the presence of α´ martensite phase. Measured pole figures of martensite phase were compared to calculated ones, assuming no variant selection and selection of variants where interaction between stress and the plate of martensite ad...

  13. Effect of annealing on martensitic transformations in "steel - TiNi alloy" explosion welded bimetallic composite

    Science.gov (United States)

    Belyaev, S. P.; Rubanik, V. V.; Resnina, N. N.; Rubanik, V. V.; Rubanik, O. E.

    2011-01-01

    The effect of explosion welding on the kinetics of martensitic transformations in a "steel - TiNi alloy" bimetallic composite and the effect of the temperature and duration of annealing on recovery of the characteristics of the martensitic transformations are studied. It is shown that annealing in the range of 450 - 600°C accompanied by retrogression of structure causes full recovery of the transformation kinetics in the alloy.

  14. Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Heinz Werner Höppel

    2012-02-01

    Full Text Available The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition.

  15. Depth profiling of hydrogen in ferritic/martensitic steels by means of a tritium imaging plate technique

    Energy Technology Data Exchange (ETDEWEB)

    Otsuka, Teppei, E-mail: t-otsuka@nucl.kyushu-u.ac.jp [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581 (Japan); Tanabe, Tetsuo [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581 (Japan)

    2013-12-15

    Highlights: ► We applied a tritium imaging plate technique to depth profiling of hydrogen in bulk. ► Changes of hydrogen depth profiles in the steel by thermal annealing were examined. ► We proposed a release model of plasma-loaded hydrogen in the steel. ► Hydrogen is trapped at trapping sites newly developed by plasma loading. ► Hydrogen is also trapped at surface oxides and hardly desorbed by thermal annealing. -- Abstract: In order to understand how hydrogen loaded by plasma in F82H is removed by annealing at elevated temperatures in vacuum, depth profiles of plasma-loaded hydrogen were examined by means of a tritium imaging plate technique. Owing to large hydrogen diffusion coefficients in F82H, the plasma-loaded hydrogen easily penetrates into a deeper region becoming solute hydrogen and desorbs by thermal annealing in vacuum. However the plasma-loading creates new hydrogen trapping sites having larger trapping energy than that for the intrinsic sites beyond the projected range of the loaded hydrogen. Some surface oxides also trap an appreciable amount of hydrogen which is more difficult to remove by the thermal annealing.

  16. Cavitation Erosion Characteristics of Nitrocarburized and HPDL-Treated Martensitic Stainless Steels

    Science.gov (United States)

    Pant, B. K.; Arya, Vivek; Mann, B. S.

    2012-06-01

    This article deals with plasma ion-nitrocarburising and high power diode laser (HPDL) surface treatment of 13Cr4Ni and X10CrNiMoV1222 martensitic stainless steels to enhance their cavitation erosion resistance. These steels are commonly used in hydro turbines and boiler feed pumps. These treated steels have been evaluated for cavitation erosion resistance and it has been observed that the plasma ion-nitrocarburising process has significantly enhanced the cavitation erosion resistance as compared to untreated steel whereas HPDL-treated steels have shown marginal improvement. This is due to formation of high hardness nitrides during nitrocarburising and formation of moderate hardness martensitic phase due to rapid heating and cooling rates involved in HPDL treatment. The cavitation erosion and micro-hardness data of plasma ion-nitrocarburized as well as HPDL-treated steel samples and their comparison with hard deposits such as stellite and HVOF coating form the main part of the article.

  17. Heat Treatment and Properties of Nitrogen Alloyed, Martensitic,Corrosion-resistant Steels

    Institute of Scientific and Technical Information of China (English)

    Reinhold Schneider; Klaus Sammt; Roland Rabitsch; Michael Haspel

    2004-01-01

    This paper gives a short introduction to the typical process route and material properties of these steels in comparison to standard martensitic corrosion-resistant steels. The typical response of these steels to various heat treatment parameters is shown and explained using the three grades M333, N360 and M340 (all made by Bohler Edelstahl GmbH) as examples, and the physical metallurgy of these steels and its consequences for practical heat treatment is explained. The correlation between tempering parameters and their effect on the toughness and corrosion properties is explained in particular detail, showing that these new steels not only offer far better property combinations under the usual heat treatment parameters than standard martensitic corrosion-resistant steels, but that they also open the door to extending heat treatment combinations and properties.

  18. Effect of partial solution treatment on martensitic transformation of 12%Cr steels; 12% Cr ko no martensite hentai ni oyobosu bubun yotaika shori no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiyama, T.; Takai, S. [Kyushu University, Fukuoka (Japan)

    1996-12-01

    When high chromium martensitic steels are subjected to partial solution treatment in (austenite+M23C6, carbide) two -phase region, not only the coarsening of austenite grains is effectively suppressed by insoluble-carbide particles, but also martensitic structure, which has formed during cooling, is refined through the treatment. In this study, the mechanism of refining of martensitic structure was discussed in Fe-12%Cr-C ternary alloys by investigating the relation between Ms temperature and solution treatment conditions, and the effect of insoluble-carbide particles on the substructures such as martensite-lath or -block. The Ms temperature of steels with full solution treatment simply depends on the content of C and Cr, but that of steels with partial solution treatment is dependent on the effective chemical composition of matrix, which is evaluated by taking the amount of C and Cr in insoluble-carbide away from their total content. Refining of martensite-block structure within grains is not caused directly by insoluble-carbide particles, but done indirectly through the refining of austenite grain size. While, on the martensite-lath structure, insoluble-carbide particles supply nucleation sites for laths, and work also as obstacles for growing laths. As a result, martensite-laths in steels with partial solution treatment are divided finely by insoluble carbide particles, and the arrangement of laths is tend to be confused. 14 refs., 10 figs., 1 tab.

  19. Deformation induced martensite in an AISI 301LN stainless steel: characterization and influence on pitting corrosion resistance

    OpenAIRE

    Hamilton Ferreira Gomes de Abreu; Sheyla Santana de Carvalho; Pedro de Lima Neto; Ricardo Pires dos Santos; Válder Nogueira Freire; Paulo Maria de Oliveira Silva; Sérgio Souto Maior Tavares

    2007-01-01

    In austenitic stainless steels, plastic deformation can induce martensite formation. The induced martensite is related to the austenite (gamma) instability at temperatures close or below room temperature. The metastability of austenite stainless steels increases with the decreasing of stacking fault energy (SFE). In this work, the deformation induced martensite was analyzed by X ray diffraction, electron back scatter diffraction (EBSD), magnetic methods and atomic force microscope (AFM) in sa...

  20. Effects of Austenite Stabilization on the Onset of Martensite Transformation in T91 Steel

    Institute of Scientific and Technical Information of China (English)

    Baoqun NING; Yongchang LIU; Qingzhi SHI; Zhiming GAO; Liushuan YANG

    2008-01-01

    The influences of thermal stabilization of austenitic on the onset temperature for a martensite transformation in T91 ferritic heat-resistant steel were studied by high-resolution differential dilatometer. The phase trans-formation kinetic information was obtained by adopting lever rule from the recorded dilatometric curves. The results show that an inverse stabilization, featured by the damage of "the atmosphere of carbon atoms" and the increase of the starting temperature for martensite transformation takes place when the T91 ferritic steel is isothermally treated above the Ms point, and it becomes strong with increasing the holding time. While the continued temperature for martensite transformation decreases gradually when isothermally holding at a temperature below Ms point. The observed inverse stabilization behavior could be attributed to the relatively high temperature of Ms point in the explored T91 ferritic heat-resistant steel.

  1. Microstructural stability of 9-12%Cr ferrite/martensite heat-resistant steels

    Institute of Scientific and Technical Information of China (English)

    Wei YAN; Wei WANG; Yi-Yin SHAN; Ke YANG

    2013-01-01

    The microstructural evolutions of advanced 9-12%Cr ferrite/martensite heat-resistant steels used for power generation plants are reviewed in this article. Despite of the small differences in chemical compositions, the steels share the same microstructure of the as-tempered martensite. It is the thermal stability of the initial microstructure that matters the creep behavior of these heat-resistant steels. The microstructural evolutions involved in 9-12%Cr ferrite heat-resistant steels are elabo- rated, including (1) martensitic lath widening, (2) disappearance of prior austenite grain boundary, (3) emergence of subgrains, (4) coarsening of precipitates, and (5) formation of new precipitates, such as Laves-phase and Z-phase. The former three microstructural evolutions could be retarded by properly disposing the latter two. Namely improving the stability of precipitates and optimizing their size distribution can effectively exert the beneficial influence of precipitates on microstructures. In this sense, the microstructural stability of the tempered martensite is in fact the stability of precipitates during the creep. Many attempts have been carried out to improve the microstructural stability of 9-12%Cr steels and several promising heat-resistant steels have been developed.

  2. On the Prediction of α-Martensite Temperatures in Medium Manganese Steels

    Science.gov (United States)

    Field, Daniel M.; Baker, Daniel S.; Van Aken, David C.

    2017-02-01

    A new composition-based method for calculating the α-martensite start temperature in medium manganese steel is presented and uses a regular solution model to accurately calculate the chemical driving force for α-martensite formation, Δ G_{Chem}^{γ to α } . In addition, a compositional relationship for the strain energy contribution during martensitic transformation was developed using measured Young's moduli (E) reported in literature and measured values for steels produced during this investigation. An empirical relationship was developed to calculate Young's modulus using alloy composition and was used where dilatometry literature did not report Young's moduli. A comparison of the Δ G_{Chem}^{γ to α } normalized by dividing by the product of Young's modulus, unconstrained lattice misfit squared (δ 2), and molar volume (Ω) with respect to the measured α-martensite start temperatures, M_{S}^{α } , produced a single linear relationship for 42 alloys exhibiting either lath or plate martensite. A temperature-dependent strain energy term was then formulated as Δ G_{str}^{γ to α } ( {{J}/{mol}} ) = EΩ δ2 (14.8 - 0.013T) , which opposed the chemical driving force for α-martensite formation. M_{S}^{α } was determined at a temperature where Δ G_{Chem}^{γ to α } + Δ G_{str}^{γ to α } = 0 . The proposed M_{S}^{α } model shows an extended temperature range of prediction from 170 K to 820 K (-103 °C to 547 °C). The model is then shown to corroborate alloy chemistries that exhibit two-stage athermal martensitic transformations and two-stage TRIP behavior in three previously reported medium manganese steels. In addition, the model can be used to predict the retained γ-austenite in twelve alloys, containing ɛ-martensite, using the difference between the calculated M_{S}^{ɛ} and M_{S}^{α }.

  3. Composite Behavior of Lath Martensite Steels Induced by Plastic Strain, a New Paradigm for the Elastic-Plastic Response of Martensitic Steels

    Science.gov (United States)

    Ungár, Tamás; Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Ribárik, Gábor; Shi, Zengmin

    2017-01-01

    Based on high-resolution neutron diffraction experiments, we will show that in lath martensite steels, the initially homogeneous dislocation structure, i.e., homogeneous on the length scale of grain size, is disrupted by plastic deformation, which, in turn, produces a composite on the length scale of martensite lath packets. The diffraction patterns of plastically strained martensitic steel reveal characteristically asymmetric peak profiles in the same way as has been observed in materials with heterogeneous dislocation structures. The quasi homogeneous lath structure, formed by quenching, is disrupted by plastic deformation producing a composite structure. Lath packets oriented favorably or unfavorably for dislocation glide become soft or hard. Two lath packet types develop by work softening or work hardening in which the dislocation densities become smaller or larger compared to the initial average dislocation density. The decomposition into soft and hard lath packets is accompanied by load redistribution and the formation of long-range internal stresses between the two lath packet types. The composite behavior of plastically deformed lath martensite opens a new way to understand the elastic-plastic response in this class of materials.

  4. Depth distribution analysis of Martensitic transformations in Xe implanted austenitic stainless steel

    DEFF Research Database (Denmark)

    Johnson, E.; Gerritsen, E.; Chechenin, N.G.

    1989-01-01

    In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase...... transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission...

  5. Microstructure and high-temperature strength of high Cr ODS tempered martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Ohtsuka, S., E-mail: ohtsuka.satoshi@jaea.go.jp; Kaito, T.; Tanno, T.; Yano, Y.; Koyama, S.; Tanaka, K.

    2013-11-15

    11-12Cr oxide dispersion strengthened (ODS) tempered martensitic steels underwent manufacturing tests and their ferritic–martensitic duplex structures were quantitatively evaluated by three methods: high-temperature X-ray diffraction (XRD), electron probe microanalyzer (EPMA), and metallography. It was demonstrated that excessive formation of residual-α ferrite, due to increasing Cr content, could be suppressed by appropriately controlling the concentration of the ferrite-forming and austenite-forming elements on the basis of the parameter “chemical driving force of α to γ reverse transformation. 11Cr-ODS steel containing a small portion of residual-α ferrite was successfully manufactured. In the as-received condition, this 11Cr-ODS steel was shown to have satisfactory creep strength and ductility, both as high as those of the 9Cr-ODS steel, while its 0.2% proof strength at 973 K was lower than in the 9Cr-ODS steel.

  6. Elevated-Temperature Ferritic and Martensitic Steels and Their Application to Future Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, RL

    2005-01-31

    In the 1970s, high-chromium (9-12% Cr) ferritic/martensitic steels became candidates for elevated-temperature applications in the core of fast reactors. Steels developed for conventional power plants, such as Sandvik HT9, a nominally Fe-12Cr-1Mo-0.5W-0.5Ni-0.25V-0.2C steel (composition in wt %), were considered in the United States, Europe, and Japan. Now, a new generation of fission reactors is in the planning stage, and ferritic, bainitic, and martensitic steels are again candidates for in-core and out-of-core applications. Since the 1970s, advances have been made in developing steels with 2-12% Cr for conventional power plants that are significant improvements over steels originally considered. This paper will review the development of the new steels to illustrate the advantages they offer for the new reactor concepts. Elevated-temperature mechanical properties will be emphasized. Effects of alloying additions on long-time thermal exposure with and without stress (creep) will be examined. Information on neutron radiation effects will be discussed as it applies to ferritic and martensitic steels.

  7. Microstructure and Hardness of High Temperature Gas Nitrided AISI 420 Martensitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Ibrahim Nor Nurulhuda Md.

    2014-07-01

    Full Text Available This study examined the microstructure and hardness of as-received and nitrided AISI 420 martensitic stainless steels. High temperature gas nitriding was employed to treat the steels at 1200°C for one hour and four hours using nitrogen gas, followed by furnace cooled. Chromium nitride and iron nitride were formed and concentrated at the outmost surface area of the steels since this region contained the highest concentration of nitrogen. The grain size enlarged at the interior region of the nitrided steels due to nitriding at temperature above the recrystallization temperature of the steel and followed by slow cooling. The nitrided steels produced higher surface hardness compared to as-received steel due to the presence of nitrogen and the precipitation of nitrides. Harder steel was produced when nitriding at four hours compared to one hour since more nitrogen permeated into the steel.

  8. Estimation of the kinetics of martensitic transformation in austenitic stainless steels by conventional and novel approaches

    Energy Technology Data Exchange (ETDEWEB)

    Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-01-29

    A comparative study was carried out on the kinetics of the martensitic transformation in a 304L stainless steel during cold rolling by conventional and novel approaches. The phase analysis based on X-ray diffraction patterns and metallography and also magnetic measurements based on ferritescope readings were utilized to elucidate the kinetics of the martensitic transformation. A straightforward magnetic measurement approach for evaluating the amount of strain-induced martensite in metastable austenitic stainless steels has been introduced in this study. This technique collects the data throughout the bulk of the material to give a realistic estimate of the amount of ferromagnetic martensite. This is an advantage over the surface collecting methods such as ferritescope readings, which overestimates the amount of martensite due to its inhomogeneous distribution through the thickness based on the frictional effects between the rolls and the specimen surface. The proposed approach can be applied in various designs for static/continuous magnetic measurement of bulk materials that is advantageous compared with the conventional vibrating sample magnetometer technique which is useful for static measurement of bulk materials with specific shapes. Moreover, in analogy to ferritescope, the output data of the developed device is directly related to the amount of martensite.

  9. Influences of Thermal Martensites and Grain Orientations on Strain-induced Martensites in High Manganese TRIP/TWIP Steels

    Institute of Scientific and Technical Information of China (English)

    Fayun Lu; Ping Yang; Li Meng; Fenge Cui; Hua Ding

    2011-01-01

    Strain-induced martensites in high manganese TRIP/TWIP steels were investigated in the presence of thermal martensites and under the influence of austenitic grain orientation by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Before deformation, the morphology of α′-M depended mainly on the number of variants and growing period. Regardless of martensite morphologies and deformation, the Kurdjumov-Sachs (K-S) orientation relationships always maintained. The 6 α′-M variants formed from a plate of ε-M were of 3 pairs of twins with a common axis <110>α′ parallel to the normal of {111}γ habit plane to minimize transformation strain. When α′-M could be formed only by deformation, it nucleated at the intersection of ε-M variants and grew mainly in thick ε-M plates. Thick ε plates promoted significantly the α′-M and weakened the influence of grain orientations. During tension, the transformation in <100>-oriented grains was observed to be slower than that in <111>-oriented grains. Deformation twins promoted ε-M formation slightly and had no apparent effect on α′-M. Deformation increased the number of ε-M variants, but reduced that of α′-M variants.

  10. Advanced manufacturing technologies of large martensitic stainless steel castings with ultra low carbon and high cleanliness

    Directory of Open Access Journals (Sweden)

    Lou Yanchun

    2010-11-01

    Full Text Available The key manufacturing technologies associated with composition, microstructure, mechanical properties, casting quality and key process control for large martensitic stainless steel castings are involved in this paper. The achievements fully satisfied the technical requirements of the large 700 MW stainless steel hydraulic turbine runner for the Three Gorges Hydropower Station, and become the major technical support for the design and manufacture of the largest 700 MW hydraulic turbine generator unit in the world developed through our own efforts. The characteristics of a new high yield to tensile strength (Rp0.2/Rm ratio and high obdurability martensitic stainless steel with ultra low carbon and high cleanliness are also described. Over the next ten years, the large martensitic stainless steel castings and advanced manufacturing technologies will see a huge demand in clean energy industry such as nuclear power, hydraulic power at home and abroad. Therefore, the new high yield o tensile strength (Rp0.2/Rm ratio and high obdurability martensitic stainless steel materials, the fast and flexible manufacturing technologies of large size castings, and new environment friendly sustainable process will face new challenges and opportunities.

  11. Nanoindentation study of ferrite–martensite dual phase steels developed by a new thermomechanical processing

    Energy Technology Data Exchange (ETDEWEB)

    Mazaheri, Yousef, E-mail: y.mazaheri@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Faculty of Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Kermanpur, Ahmad; Najafizadeh, Abbas [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2015-07-15

    Dual phase (DP) steels consisting different volume fractions of ferrite and martensite and different ferrite grain size were produced by a new route utilizing cold-rolling and subsequent intercritical annealing of ferrite/martensite duplex starting structure at 770 °C for different times. Scanning electron microscopy has been supplemented by nanoindentation and tensile test to follow microstructural changes and their correlations to the variation in phase's hardness and mechanical properties. The results showed that longer holding times resulted in coarser and softer ferrite grains in DP microstructures. Martensite nanohardness variation with holding time is related to change in its carbon content. Mechanical properties such as strength, elongation and toughness are well correlated with the martensite/ferrite hardness ratio.

  12. Microstructure Evolution in 9Cr Martensitic Steel During Long-Term Creep at 650℃

    Institute of Scientific and Technical Information of China (English)

    HU Zheng-fei; WANG Qi-jiang; ZHANG Bin

    2012-01-01

    Standardarized creep and rupture strength tests were conducted for commercial T91 martensitic heat-resistant steel at 650℃and corresponding microstructure was characterized by BSED, TEM and EDS. The martensitic microstructure degenerated seriously during creep exposure, including martensitic substructure recovering, carbides coarsening, dissolving and precipitating. EDS analysis shows that the M23C6 carbides in different morphologies have dissimilar compositions. The rod/sheet like M23 C6 particles within the matrix contain more additions, which might precipitate in situ while fine MX particles were re-solving. The high content of silicon in these rod/sheet like M2aC6 carbides is probably related to self diffusion coefficient increasing for the exposed condition at 650 ~C close to Curie temperature To. For those reasons, martensite substructure becomes unstable, and microstructure evolution is accelerated and leads to creep strength deteriorating severely.

  13. Atomic scale investigation of non-equilibrium segregation of boron in a quenched Mo-free martensitic steel.

    Science.gov (United States)

    Li, Y J; Ponge, D; Choi, P; Raabe, D

    2015-12-01

    B-added low carbon steels exhibit excellent hardenability. The reason has been frequently attributed to B segregation at prior austenite grain boundaries, which prevents the austenite to ferrite transformation and favors the formation of martensite. The segregation behavior of B at prior austenite grain boundaries is strongly influenced by processing conditions such as austenitization temperatures and cooling rates and by alloying elements such as Mo, Cr, and Nb. Here an local electrode atom probe was employed to investigate the segregation behavior of B and other alloying elements (C, Mn, Si, and Cr) in a Cr-added Mo-free martensitic steel. Similar to our previous results on a Mo-added steel, we found that in both steels B is segregated at prior austenite grain boundaries with similar excess values, whereas B is neither detected in the martensitic matrix nor at martensite-martensite boundaries at the given cooling rate of 30K/s. These results are in agreement with the literature reporting that Cr has the same effect on hardenability of steels as Mo in the case of high cooling rates. The absence of B at martensite-martensite boundaries suggests that B segregates to prior austenite grain boundaries via a non-equilibrium mechanism. Segregation of C at all boundaries such as prior austenite grain boundaries and martensite-martensite boundaries may occur by an equilibrium mechanism.

  14. Constitutive modelling of stainless steels for cryogenic applications. Strain induced martensitic transformation

    CERN Document Server

    Garion, C

    2001-01-01

    The 300-series stainless steels are metastable austenitic alloys: martensitic transformation occurs at low temperatures and/or when plastic strain fields develop in the structures. The transformation influences the mechanical properties of the material. The present note aims at proposing a set of constitutive equations describing the plastic strain induced martensitic transformation in the stainless steels at cryogenic temperatures. The constitutive modelling shall create a bridge between the material sciences and the structural analysis. For the structures developing and accumulating plastic deformations at sub-zero temperatures, it is of primary importance to be able to predict the intensity of martensitic transformation and its effect on the material properties. In particular, the constitutive model has been applied to predict the behaviour of the components of the LHC interconnections, the so-called bellows expansion joints (the LHC mechanical compensation system).

  15. Fatigue Hardening Behavior of 1.5 GPa Grade Transformation-Induced Plasticity-Aided Martensitic Steel

    Science.gov (United States)

    Sugimoto, Koh-Ichi; Hojo, Tomohiko

    2016-11-01

    Low cycle fatigue hardening/softening behavior of a 0.2 pct C-1.5 pct Si-1.5 pct Mn-1.0 pct Cr-0.2 pct Mo-0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel consisting of a wide lath martensite structure matrix and a narrow lath martensite-metastable retained austenite mixture was investigated. The steel exhibited notable fatigue hardening in the same way as TRIP-aided bainitic ferrite steel, although conventional martensitic steel such as SCM420 steel with the same tensile strength exhibited fatigue softening. The considerable fatigue hardening of this steel is believed to be associated mainly with the compressive internal stress that results from a difference in flow stress between the matrix and the martensite-austenite-like phase, with a small contribution from the strain-induced transformation and dislocation hardenings.

  16. Summary of the IEA workshop/working group meeting on ferritic/martensitic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    An International Energy Agency (IEA) Working Group on Ferritic/Martensitic Steels for Fusion Applications, consisting of researchers from Japan, the European Union, the United States, and Switzerland, met at the headquarters of the Joint European Torus (JET), Culham, United Kingdom, 24-25 October 1996. At the meeting preliminary data generated on the large heats of steel purchased for the IEA program and on other heats of steels were presented and discussed. The second purpose of the meeting was to continue planning and coordinating the collaborative test program in progress on reduced-activation ferritic/martensitic steels. The next meeting will be held in conjunction with the International Conference on Fusion Reactor Materials (ICFRM-8) in Sendai, Japan, 23-31 October 1997.

  17. Tensile and impact behaviour of BATMAN II steels, Ti-bearing reduced activation martensitic alloys

    Science.gov (United States)

    Filacchioni, G.; Casagrande, E.; De Angelis, U.; De Santis, G.; Ferrara, D.; Pilloni, L.

    Two series of Reduced Activation Ferrous alloys (RAF) have been produced and studied by Casaccia's Laboratories. These martensitic alloys are named BATMAN steels. They are among the few presently developed RAF materials to exploit Ti as a carbide forming and grain size stabilizing element instead of Ta. In this work their mechanical properties are illustrated.

  18. A study on Z-phase nucleation in martensitic chromium steels

    DEFF Research Database (Denmark)

    Golpayegani, Ardeshir; Andrén, Hans-Olof; Danielsen, Hilmar Kjartansson;

    2008-01-01

    9–12% chromium martensitic steels are liable to the precipitation of Z-phase, Cr(V,Nb)N, after long time exposure at 550–650 ◦C. This complex nitride consumes vanadium nitrides and causes the creep strength of the material to fall drastically after several thousand hours of exposure. In this work...

  19. About Reverted Austenite in Carburized Layers of Low-Carbon Martensitic Steels

    Science.gov (United States)

    Ivanov, A. S.; Bogdanova, M. V.; Vylezhnev, V. P.

    2015-05-01

    Processes of surface hardening in low-carbon martensitic steel 24Kh2G2NMFTB under carburizing and subsequent quenching from the intercritical temperature range are studied. Special features of formation of reverted austenite with high strength and stability are considered.

  20. Modeling of the Austenite-Martensite Transformation in Stainless and TRIP Steels

    NARCIS (Netherlands)

    Geijselaers, H.J.M.; Hilkhuijsen, P.; Bor, T.C.; Perdahcioglu, E.S.; Boogaard, van den A.H.; Zhang, S.-H.; Liu, X.-H.; Gheng, M.; Li, J.

    2013-01-01

    The transformation of austenite to martensite is a dominant factor in the description of the constitutive behavior during forming of TRIP assisted steels. To predict this transformation different models are currently available. In this paper the transformation is regarded as a stress induced process

  1. Improved impact toughness of 13Cr martensitic stainless steel hardened by laser

    Science.gov (United States)

    Tsay, L. W.; Chang, Y. M.; Torng, S.; Wu, H. C.

    2002-08-01

    The impact toughness of AISI 403 martensitic stainless steel plate and laser-hardened specimens tempered at various temperatures were examined. Phosphorus was the primary residual impurity responsible for tempered embrittlement of this alloy. The experimental result also indicated that AISI 403 stainless steel was very sensitive to reverse-temper embrittlement. The improved impact toughness of the laser-hardened specimen was attributed to the refined microstructure in the laser-hardened zone.

  2. Hybrid/Tandem Laser-Arc Welding of Thick Low Carbon Martensitic Stainless Steel Plates =

    Science.gov (United States)

    Mirakhorli, Fatemeh

    High efficiency and long-term life of hydraulic turbines and their assemblies are of utmost importance for the hydropower industry. Usually, hydroelectric turbine components are made of thick-walled low carbon martensitic stainless steels. The assembly of large hydroelectric turbine components has been a great challenge. The use of conventional welding processes involves typical large groove design and multi-pass welding to fill the groove which exposes the weld to a high heat input creating relatively large fusion zone and heat affected zone. The newly-developed hybrid/tandem laser-arc welding technique is believed to offer a highly competitive solution to improve the overall hydro-turbine performance by combining the high energy density and fast welding speed of the laser welding technology with the good gap bridging and feeding ability of the gas metal arc welding process to increase the productivity and reduce the consumable material. The main objective of this research work is to understand different challenges appearing during hybrid laser-arc welding (HLAW) of thick gauge assemblies of low carbon 13%Cr- 4%Ni martensitic stainless steel and find a practical solution by adapting and optimizing this relatively new welding process in order to reduce the number of welding passes necessary to fill the groove gap. The joint integrity was evaluated in terms of microstructure, defects and mechanical properties in both as-welded and post-welded conditions. A special focus was given to the hybrid and tandem laser-arc welding technique for the root pass. Based on the thickness of the low carbon martensitic stainless steel plates, this work is mainly focused on the following two tasks: • Single pass hybrid laser-arc welding of 10-mm thick low carbon martensitic stainless steel. • Multi-pass hybrid/tandem laser-arc welding of 25-mm thick martensitic stainless steel.

  3. Low-temperature martensitic transformation and deep cryogenic treatment of a tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Tyshchenko, A.I. [G.V. Kurdyumov Institute for Metal Physics, 03142 Kiev (Ukraine); Theisen, W.; Oppenkowski, A.; Siebert, S. [Ruhr University Bochum, Chair of Materials Technology, 44780 Bochum (Germany); Razumov, O.N.; Skoblik, A.P.; Sirosh, V.A.; Petrov, Yu.N. [G.V. Kurdyumov Institute for Metal Physics, 03142 Kiev (Ukraine); Gavriljuk, V.G., E-mail: gavr@imp.kiev.ua [G.V. Kurdyumov Institute for Metal Physics, 03142 Kiev (Ukraine)

    2010-10-15

    Research highlights: {yields} Low-temperature martensitic transformation is important for beneficial effect of DCT. {yields} Plastic deformation occurs in the course of low-temperature martensitic transformation. {yields} Carbon clouds around dislocations are formed due to the capture of immobile carbon atoms by gliding dislocations. {yields} Carbide phase is partially dissolved during DCT. - Abstract: The tool steel X220CrVMo 13-4 (DIN 1.2380) containing (mass%) 2.2C, 13Cr, 4V, 1Mo and the binary alloy Fe-2.03 mass% C were studied using transmission electron microscopy, Moessbauer spectroscopy, X-ray diffraction and internal friction with the aim of shedding light on processes occurring during deep cryogenic treatment. It is shown that the carbon atoms are essentially immobile at temperatures below -50 deg. C, whereas carbon clustering in the virgin martensite occurs during heating above this temperature. An increase in the density of dislocations, the capture of immobile carbon atoms by moving dislocations, the strain-induced partial dissolution of the carbide phase, and the abnormally low tetragonality of the virgin martensite are found and interpreted in terms of plastic deformation that occurs during martensitic transformation at low temperatures where the virgin martensite is sufficiently ductile.

  4. Martensite transformation induced by deformation and its phase electrochemical behavior for stainless steels AISI 304 and 316L

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The martensite transformation induced by tensile elongation and its effect on the behavior of phase electrochemistry of AISI 304 and 316L in 3.5% NaCl solution were studied. The results show that the content of ((-martensite in stainless steel 304 increases with the true strain. As ((-martensite content increased, free corrosion potential and pitting potential of stainless steel 304 in 3.5% NaCl solution appeared the change trend of a minimum. It was also found that pitting nucleated preferentially at the phase interfaces between martensite and austenite. There existed apparent difference between electrochemical properties of austenite and of martensite for stainless steel 304 and 316L in 3.5% NaCl solution.

  5. Polarized SANS study of microstructural evolution in a martensitic steel for fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Coppola, R. [ENEA-Casaccia, FIS, CP 2400, 00100 Roma (Italy); Glaettli, H. [CEA-SACLAY, SPEC and Laboratoire Leon Brillouin (CEA-CNRS), 91191 Gif-sur-Yvette (France); Valli, M. [ENEA-Bologna, FIS, V. Don Fiammelli 2, 40128 Bologna (Italy)

    2002-07-01

    The results of a polarized SANS study of a martensitic steel (MANET) developed for fusion-reactor technology are presented. The measurements were carried out to investigate Cr-redistribution phenomena in the martensitic matrix, which can play a crucial role in ductile-to-brittle transition changes under irradiation. The nuclear-magnetic interference term and the ratio of nuclear plus magnetic to nuclear SANS cross sections show that such inhomogeneities, which are present immediately after quenching and give rise to Fe-rich precipitates, dissolve even for short tempering times. (orig.)

  6. Plastic deformation modelling of tempered martensite steel block structure by a nonlocal crystal plasticity model

    Directory of Open Access Journals (Sweden)

    Martin Boeff

    2014-01-01

    Full Text Available The plastic deformations of tempered martensite steel representative volume elements with different martensite block structures have been investigated by using a nonlocal crystal plasticity model which considers isotropic and kinematic hardening produced by plastic strain gradients. It was found that pronounced strain gradients occur in the grain boundary region even under homogeneous loading. The isotropic hardening of strain gradients strongly influences the global stress–strain diagram while the kinematic hardening of strain gradients influences the local deformation behaviour. It is found that the additional strain gradient hardening is not only dependent on the block width but also on the misorientations or the deformation incompatibilities in adjacent blocks.

  7. Plasma assisted nitriding for micro-texturing onto martensitic stainless steels*

    Directory of Open Access Journals (Sweden)

    Katoh Takahisa

    2015-01-01

    Full Text Available Micro-texturing method has grown up to be one of the most promising procedures to form micro-lines, micro-dots and micro-grooves onto the mold-die materials and to duplicate these micro-patterns onto metallic or polymer sheets via stamping or injection molding. This related application requires for large-area, fine micro-texturing onto the martensitic stainless steel mold-die materials. A new method other than laser-machining, micro-milling or micro-EDM is awaited for further advancement of this micro-texturing. In the present paper, a new micro-texturing method is developed on the basis of the plasma assisted nitriding to transform the two-dimensionally designed micro-patterns to the three dimensional micro-textures in the martensitic stainless steels. First, original patterns are printed onto the surface of stainless steel molds by using the dispenser or the ink-jet printer. Then, the masked mold is subjected to high density plasma nitriding; the un-masked surfaces are nitrided to have higher hardness, 1400 Hv than the matrix hardness, 200 Hv of stainless steels. This nitrided mold is further treated by sand-blasting to selectively remove the soft, masked surfaces. Finally, the micro-patterned martensitic stainless steel mold is fabricated as a tool to duplicate these micro-patterns onto the plastic materials by the injection molding.

  8. Influence of Prior Fatigue Cycling on Creep Behavior of Reduced Activation Ferritic-Martensitic Steel

    Science.gov (United States)

    Sarkar, Aritra; Vijayanand, V. D.; Parameswaran, P.; Shankar, Vani; Sandhya, R.; Laha, K.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

    2014-06-01

    Creep tests were carried out at 823 K (550 °C) and 210 MPa on Reduced Activation Ferritic-Martensitic (RAFM) steel which was subjected to different extents of prior fatigue exposure at 823 K at a strain amplitude of ±0.6 pct to assess the effect of prior fatigue exposure on creep behavior. Extensive cyclic softening that characterized the fatigue damage was found to be immensely deleterious for creep strength of the tempered martensitic steel. Creep rupture life was reduced to 60 pct of that of the virgin steel when the steel was exposed to as low as 1 pct of fatigue life. However, creep life saturated after fatigue exposure of 40 pct. Increase in minimum creep rate and decrease in creep rupture ductility with a saturating trend were observed with prior fatigue exposures. To substantiate these findings, detailed transmission electron microscopy studies were carried out on the steel. With fatigue exposures, extensive recovery of martensitic-lath structure was distinctly observed which supported the cyclic softening behavior that was introduced due to prior fatigue. Consequently, prior fatigue exposures were considered responsible for decrease in creep ductility and associated reduction in the creep rupture strength.

  9. Antibacterial Property of Martensitic Stainless Steel Generated by Cu Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    XU Bo-fan; NI Hong-wei; DAN Zhi-gang; XIONG Juan; XIONG Ping-yuan

    2004-01-01

    Copper ions were implanted into a AISI420 martensitic stainless steel (SS) by metal vapor vacuum arc (MEVVA) with a dose range 0.2 ×1017 ~5.0×1017 cm-2 at the energy of 100keV. The Cu-implanted stainless steel was treated by a special antibacterial treatment subsequently. The phase compositions in the implanted layer were studied by glancing X-ray diffraction (GXRD) and changes of bacterial appearance on the surface of Cu un-implanted SS and Cu-implanted SS with antibacterial treatment SS were observed by bio-TEM (transmission electron microscopy) separately. The results showed that a suitable amount of Cu-rich phase was dispersed in the implanted layer of Cu-implanted SS that was treated by special antibacterial treatment. So the Cu-implanted martensitic stainless steel with antibacterial treatment reveals excellent antibacterial property against both E. coli and S. aureus.

  10. Antibacterial Property of Martensitic Stainless Steel Generated by Cu Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    XUBo-fan; NIHong-wei; DANZhi-gang; XIONGJuan; XIONGPing-yuan

    2004-01-01

    Copper ions were implanted into a AISI420 martensitic stainless steel (SS) by metal vapor vacuum arc (MEVVA) with a dose range 0.2×1017-5.0×1017cm-2 at the energy of 100keV. The Cu-implanted stainless steel was treated by a special antibacterial treatment subsequently. The phase compositions in the implanted layer were studied by glancing X-ray diffraction (GXRD) and changes of bacterial appearance on the surface of Cu un-implanted SS and Cu-implanted SS with antibacterial treatment SS were observed by bio-TEM (transmission electron microscopy) separately. The results showed that a suitable amount of Cu-rich phase was dispersed in the implanted layer of Cu-implanted SS that was treated by special antibacterial treatment. So the Cu-implanted martensitic stainless steel with antibacterial treatment reveals excellent antibacterial property against both E. coli and S. aureus.

  11. Martensitic transformation and physical properties of `steel-TiNi' bimetal composite, produced by explosion welding

    Science.gov (United States)

    Belyaev, S.; Rubanik, V.; Resnina, N.; Rubanik, V.; Rubanik, O.; Borisov, V.

    2010-04-01

    The aim of this work is an investigation of structure and martensitic transformation in bimetal composite 'TiNi-stainless steel' produced by explosion welding. The results have shown that the mixture of chemical elements is observed in very narrow intervals of 6 µm close to the joint - 2 µm from the TiNi side and 4 µm from the steel one. Micro-hardness distribution in the vicinity of the joint is non-monotonic in the interval of 60 µm. Connection of stainless steel and TiNi plates by explosion welding leads to a dramatic change of martensitic transformation kinetics. Temperatures and the temperature interval of phase transformation increase strongly and heat transformation decreases. Annealing at 500°C for 2 h of bimetal composite decreases the interval of micro-hardness variation and partially recovers kinetics of phase transitions.

  12. Development of Low and Middle Carbon Martensite Spring Steel with High Strength and Toughness for Automobile

    Institute of Scientific and Technical Information of China (English)

    Li Ye-sheng; Wu Zi-ping; Zhu Yin-lu; Chen Hui-huang

    2004-01-01

    The conventional middle and high carbon spring steels have some drawbacks in properties, production and application. In order to meet the demands of rapid development of automobile, a new low and middle carbon spring steel35Si2CrMnVB, C0.34, Sil.66, Mn0.80, Cr0.67, V0.13, B0.001, P0.011, S0.014 wt.%, has been developed. Comparison between the new spring steel 35Si2CrMnVB and the conventional spring steel 60Si2MnA, C0.61, Sil.75, Mn0.76, P0.021,S0.018 wt.%, shows that the new spring steel has not only high strength, good ductility, good comprehensive mechanical properties, but also low decarbonization tendency, sufficient hardenability and high elastic sag resistance, etc.. The microstructure change in quenched steel caused by the decreasing of carbon contents is detected through metallographic observation, the new low and middle carbon spring steel 35Si2CrMnVB after quenching is composed of almost lath martensite with high dislocation density and only a little martensite with twin structure. It is testified that to develop low carbon spring steel with more excellent properties for automobile is feasible.

  13. Mechanical Properties and Microstructure of Dissimilar Friction Stir Welds of 11Cr-Ferritic/Martensitic Steel to 316 Stainless Steel

    Science.gov (United States)

    Sato, Yutaka S.; Kokawa, Hiroyuki; Fujii, Hiromichi T.; Yano, Yasuhide; Sekio, Yoshihiro

    2015-12-01

    Dissimilar joints between ferritic and austenitic steels are of interest for selected applications in next generation fast reactors. In this study, dissimilar friction-stir welding of an 11 pct Cr ferritic/martensitic steel to a 316 austenitic stainless steel was attempted and the mechanical properties and microstructure of the resulting welds were examined. Friction-stir welding produces a stir zone without macroscopic weld-defects, but the two dissimilar steels are not intermixed. The two dissimilar steels are interleaved along a sharp zigzagging interface in the stir zone. During small-sized tensile testing of the stir zone, this sharp interface did not act as a fracture site. Furthermore, the microstructure of the stir zone was refined in both the ferritic/martensitic steel and the 316 stainless steel resulting in improved mechanical properties over the adjacent base material regions. This study demonstrates that friction-stir welding can produce welds between dissimilar steels that contain no macroscopic weld-defects and display suitable mechanical properties.

  14. Position-dependent shear-induced austenite– martensite transformation in double-notched TRIP and dual-phase steel samples

    NARCIS (Netherlands)

    Blondé, R.J.P.; Jimenez-Melero, E.; Anusuya Ponnusami, S.; Zhao, L.; Schell, N.; Brück, E.H.; Van der Zwaag, S.; Van Dijk, N.H.

    2014-01-01

    While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation

  15. Position-dependent shear-induced austenite– martensite transformation in double-notched TRIP and dual-phase steel samples

    NARCIS (Netherlands)

    Blondé, R.J.P.; Jimenez-Melero, E.; Anusuya Ponnusami, S.; Zhao, L.; Schell, N.; Brück, E.H.; Van der Zwaag, S.; Van Dijk, N.H.

    2014-01-01

    While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation

  16. Electronic Structures and Alloying Behaviors of Ferrite Phases in High Co-Ni Secondary Hardened Martensitic Steels

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The electronic structure of ferrite (tempered martensite phase) in high Co-Ni secondary hardened martensitic steel has been investigated. The local density of states (LDOS) of alloying elements in the steel displays the relationship between solid solubility and the shape of the LDOS. The bond order integral (BOI) between atoms in the steel shows that the directional bonding of the p orbital of Si or C leads to the brittleness of the steel. At last, ∑BOI between atoms demonstrate that C, Co, Mn, Cr, Mo, Si strengthen the alloyed steel through solid-solution effects.

  17. Recent progress of R and D activities on reduced activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Q., E-mail: qunying.huang@fds.org.cn [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, P.O. Box 1135, Hefei, Anhui 230031 (China); Baluc, N. [CRPP-EPFL, ODGA C110 5232 Villigen PSI (Switzerland); Dai, Y. [LNM, PSI, 5232 Villigen PSI (Switzerland); Jitsukawa, S. [JAEA, 2-4 Shirakata, Tokai-Mura, Ibaraki-Ken 319-1195 (Japan); Kimura, A. [IAE, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Konys, J. [KIT, P.O. Box 3640, 76021 Karlsruhe (Germany); Kurtz, R.J. [PNNL, Richland, WA 99352 (United States); Lindau, R. [KIT, P.O. Box 3640, 76021 Karlsruhe (Germany); Muroga, T. [NIFS, Oroshi, Toki, Gifu 509-5292 (Japan); Odette, G.R. [UCSB, Santa Barbara, CA (United States); Raj, B. [IGCAR, Kalpakkam 603 102 (India); Stoller, R.E.; Tan, L. [ORNL, P.O. Box 2008, Oak Ridge, TN 37831 (United States); Tanigawa, H. [JAEA, Naka, Ibaraki 311-0193 (Japan); Tavassoli, A.-A.F. [DMN/Dir, DEN, CEA Saclay, 91191 Gif-sur-Yvette cedex (France); Yamamoto, T. [UCSB, Santa Barbara, CA (United States); Wan, F. [DMPC, USTB, Beijing 100083 (China); Wu, Y. [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, P.O. Box 1135, Hefei, Anhui 230031 (China)

    2013-11-15

    Several types of reduced activation ferritic/martensitic (RAFM) steel have been developed over the past 30 years in China, Europe, India, Japan, Russia and the USA for application in ITER test blanket modules (TBMs) and future fusion DEMO and power reactors. The progress has been particularly important during the past few years with evaluation of mechanical properties of these steels before and after irradiation and in contact with different cooling media. This paper presents recent RAFM steel results obtained in ITER partner countries in relation to different TBM and DEMO options.

  18. M5C2 carbide precipitates in a high-Cr martensitic steel

    Science.gov (United States)

    Shen, Yinzhong; Ji, Bo; Zhou, Xiaoling

    2014-05-01

    The precipitate phases in an advanced 11% Cr martensitic steel, expected to be used at 650 °C, have been investigated to understand the effect of precipitates on the creep-rupture strength of the steel. M23C6 and MX precipitates were dominant phases in this steel. Needle-like precipitates with a typical length of 180 nm and width of 20 nm; and metallic-element compositions of 53-74Fe, 16-26Cr, 3-18Ta, 2-8W, and 2-4Co (at%); were observed mainly within the martensite laths of the normalized-and-tempered steel. The needle-like precipitates have been identified as monoclinic carbide M5C2, which is not known to have been reported previously in high chromium steels, or in heat-resistant steels those have been normalized-and-tempered. This indicates that the formation of M5C2 carbides can occur in heat-resistant steels produced under appropriate tempering conditions, and that this does not require long-term isothermal aging or creep testing, in all cases.

  19. Formation of carburized layer structure with reverted austenite on low-carbon martensitic steel 12Kh2G2NMFT

    Science.gov (United States)

    Ivanov, A. S.; Bogdanova, M. V.

    2013-03-01

    The structure of surface layer in low-carbon martensitic steel 12Kh2G2NMFT obtained by carburizing followed by high-temperature tempering and quenching from the intercritical temperature range is investigated.

  20. Evaluation of selected martensitic stainless steels for use in downhole tubular expansion - Results of a laboratory study

    Energy Technology Data Exchange (ETDEWEB)

    Mack, Robert [Shell International E and P, b.v. Kessler Park 1, Postbus 60, 2280 AB Rijswijk (Netherlands)

    2004-07-01

    A laboratory program was performed to evaluate the potential of selected martensitic stainless steels for downhole cladding applications. The evaluation of the effects of tubular expansion on mechanical properties, defects, and resistance to environmentally assisted cracking demonstrated that some steels were acceptable for the intended application. The results were used to qualify and select the stainless steel for the intended sweet cladding applications. (authors)

  1. Chemical compatibility study of lithium titanate with Indian reduced activation ferritic martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Sonak, Sagar, E-mail: sagarsonak@gmail.com [Fusion Reactor Materials Section, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Jain, Uttam [Fusion Reactor Materials Section, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Haldar, Rumu [Material Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kumar, Sanjay [Fusion Reactor Materials Section, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2015-11-15

    Highlights: • Chemical compatibility between Li{sub 2}TiO{sub 3} and Indian RAFM steel has been studied at ITER operating temperature. • The lithium titanate chemically reacted with ferritic martensitic steel to form a brittle and non-adherent oxide layer. • The layer grew in a parabolic manner as a function of heating time. • Diffusion of oxygen (from Li{sub 2}TiO{sub 3}) appears to be controlling the oxide layer. - Abstract: Chemical compatibility between lithium titanate and Indian reduced activation ferritic-martensitic steel (In-RAFMS) was studied for the first time under ITER operating temperature. Lithium titanate required for the study was synthesized in-house. Coupons of In-RAFMS were packed inside lithium titanate powder and heated at 550 °C up to 900 h under inert argon atmosphere. The lithium titanate chemically reacted with ferritic martensitic steel to form a brittle and non-adherent oxide layer. The layer grew in a parabolic manner as a function of heating time. Microstructural and phase evolution of this oxide layer was studied using XRD, SEM and EPMA. Iron and chromium enriched zones were found within the oxide layer. Diffusion of oxygen (from Li{sub 2}TiO{sub 3}) appears to be controlling the oxide layer.

  2. Effects of Plastic Deformation and Stresses on Dilatation during the Martensitic Transformation in a B-bearing Steel

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    To provide data for improved modelling of the behaviour of steelcomponents in a simultaneous forming and quenching process, the effects of plastic deformation and stresses on dilatation during the martensitic transformation in a B-bearing steel were investigated. It was found that plastic deformation of austenite at high temperatures enhances ferrite formation significantly,and consequently, the dilatation decreases markedly even at a cooling rate of 280℃/s. The created ferritic-martensitic microstructure possesses clearly lower hardness and strength than the martensitic structure. Elastic stresses cause the preferred orientation in martensite to be formed so that diametric dilatation can increase by nearly 200% under axial compression.

  3. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    Science.gov (United States)

    Chernov, I. I.; Kalashnikov, A. N.; Kalin, B. A.; Binyukova, S. Yu

    2003-12-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe-C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion irradiation up to a fluence of 5 × 10 20 m -2 at the temperature of 920 K. It was shown that helium-ion irradiation at high temperature resulted in formation of bubbles with a greater size and a smaller density in Fe and ferritic-martensitic steels than those in nickel and austenitic steels. Large gaseous bubbles in ferritic component are uniformly distributed in grains body in Fe-C alloys as well as in ferritic-martensitic steels. The bubbles with a higher density and a smaller size than those in ferritic component are formed in martensitic grains of steels and Fe-C alloys with a high carbon content ( NC>0.01 wt%), which leads to a small level of swelling of martensite in comparison with that of ferrite. In addition, the bubbles in martensitic grains have a tendency to ordered distribution.

  4. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Chernov, I.I. E-mail: chernov@phm.mephi.ru; Kalashnikov, A.N.; Kalin, B.A.; Binyukova, S.Yu

    2003-12-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe-C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion irradiation up to a fluence of 5 x 10{sup 20} m{sup -2} at the temperature of 920 K. It was shown that helium-ion irradiation at high temperature resulted in formation of bubbles with a greater size and a smaller density in Fe and ferritic-martensitic steels than those in nickel and austenitic steels. Large gaseous bubbles in ferritic component are uniformly distributed in grains body in Fe-C alloys as well as in ferritic-martensitic steels. The bubbles with a higher density and a smaller size than those in ferritic component are formed in martensitic grains of steels and Fe-C alloys with a high carbon content (N{sub C}>0.01 wt%), which leads to a small level of swelling of martensite in comparison with that of ferrite. In addition, the bubbles in martensitic grains have a tendency to ordered distribution.

  5. Mechanical properties and microstructure of advanced ferritic-martensitic steels used under high dose neutron irradiation

    Science.gov (United States)

    Shamardin, V. K.; Golovanov, V. N.; Bulanova, T. M.; Povstianko, A. V.; Fedoseev, A. E.; Goncharenko, Yu. D.; Ostrovsky, Z. E.

    Some results of the study of mechanical properties and structure of ferritic-martensitic chromium steels with 13% and 9% chromium, irradiated in the BOR-60 reactor up to different damage doses are presented in this report. Results concerning the behaviour of commercial steels, containing to molybdenum, vanadium and niobium, and developed for the use in fusion reactors, are compared to low-activation steels in which W and Ta replaced Mo and Nb. It is shown that after irradiation to the dose of ˜10 dpa at 400°C 0.1C-9Cr-1W, V, Ta steels are prone to lower embrittlement as deduced from fracture surface observations of tensile specimens. Peculiarities of fine structure and fracture mode, composition and precipitation reactions in steels during irradiation are discussed.

  6. Elevated temperature properties of ferritic/martensitic steels for application to future nuclear reators

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ji Hyun; Kim, Sung Ho; Ryu, Woo Seog; Chang, Jong Hwa

    2005-12-15

    The future nuclear systems such as nuclear hydrogen production reactors and fusion reactor require low activation and radiation embrittlement resistance in addition to excellent high temperature properties because their operating temperature are even higher than those of the light water reactors. The R and D of ferritic-martensitic steels in nuclear leading centuries like USA, Japan and EU has been continued for decades of years nuclear and they commercialized several steels. Korea consider modified 9Cr-1Mo steel as a candidate materials for reactor pressure vessel of very high temperature reactor. This state-of-the art report aimed to provide informations about the applicabilities of high Cr steels and low Cr steels through the analyses of their microstructures, mechanical properties and radiation characteristics. The metallurgical understanding of background of alloy evolutions might be helpful for the establishment of research orientation.

  7. A physically based model for the isothermal martensitic transformation in a maraging steel

    Science.gov (United States)

    Kruijver, S. O.; Blaauw, H. S.; Beyer, J.; Post, J.

    2003-10-01

    Isothermal transformation from austenite to martensite in steel products during or after the production process often show residual stresses which can create unacceptable dimensional changes in the final product. Tn order to gain more insight in the effects infiuencing the isothermai transformation, the overall kinetics in a low Carbon-Nickel maraging steel is investigated. The influence of the austenitizing température, time and quenching rate on the transformation is measured magnetically and yields information about the transformation rate and final amount of transformation. A physically based model describing the nucleation and growth of martensite is used to explain the observed effects. The results show a very good fit of the experimental values and the model description of the transformation, within the limitations of the inhomogeneities (carbides and intermetallics, size and distribution in the material and stress state) and experimental conditions.

  8. Mechanical strength of martensitic 10%-Cr-steel after low-dose irradiation in HFR

    Energy Technology Data Exchange (ETDEWEB)

    Materna-Morris, E. [Inst. fuer Materialforschung 1, Kernforschungszentrum Karlsruhe GmbH (Germany); Romer, O. [Hauptabteilung fuer Versuchstechnik/Heisse Zellen, Kernforschungszentrum Karlsruhe GmbH (Germany)

    1995-12-31

    Within the framework of the SIENA irradiation program (Steel Irradiation in an Enhanced Neutron Arrangement), the materials MANET I (DIN 1.4914) and AISI 316 L favored for the NET (Next European Torus) fusion reactor were investigated. The martensitic 9-12% chromium steels are considered as alternative materials for components of fusion reactors, because of their low He embrittlement and the good swelling behavior. Irradiations of the martensitic tensile specimens were performed in the reactor at 300 C, 400 C and 475 C, respectively with irradiation doses of 5, 10 and 15 dpa attained. Following the post-irradiation tensile tests, considerable hardening of the material was observed at low irradiation and test temperatures. In the microstructure, dislocation loops and He bubbles were found to occur as irradiation induced material changes. The dislocation loops contribute significantly to material embrittlement. (orig.).

  9. The Z-Phase in 9Cr Ferritic/martensitic Heat Resistant Steel

    Science.gov (United States)

    Yin, Fengshi; Chen, Fuxia; Jiang, Xuebo; Xue, Bing; Zhou, Li; Jung, Woosang

    The precipitation behavior of Z-phase was investigated during long-term aging at 650°C in an ultra low carbon 9Cr ferritic/martensitic heat resistant steel. The steel was prepared by vacuum induction melting followed by hot forging and rolling into a plate. The plate was normalized at 1100°C for 1h, cooled in air and tempered at 700°C for 1h. Bimodal nano-sized MX precipitates distribute densely and homogeneously in the matrix within martensitic lath after normalizing-and-tempering heat treatment. After aging at 650°C for 1200h, the Z-phase was found to nucleate on the larger nano-sized MX. The Z-phase and MX have the following orientation relationship: Z-phase//MX and (1bar 10){Z-phase}//(200){MX} .

  10. Deformation behavior of reduced activation ferritic steel during tensile test

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, Kiyoyuki [Department of Material Science and Engineering, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibakaki 319-1195 (Japan)]. E-mail: shiba@realab01.tokai.jaeri.go.jp; Hirose, Takanori [Department of Fusion Engineering Research, Japan Atomic Energy Research Institute, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)

    2006-02-15

    Deformation behavior of reduced activation martensitic steel F82H during tensile tests were studied. True stress-true strain diagrams were calculated with minimum diameter determined from the specimen profile obtained by laser micro-gauge scanning the diameter along the longitudinal direction during tensile test. Cylindrical specimens of F82H were used for the measurement and test temperatures were room temperature (RT), 300, 400, 500 and 600 deg. C. Tensile tests were carried out with 1 x 10{sup -4} s{sup -1} of strain rate. Other strain rates (1 x 10{sup -3} and 1 x 10{sup -5} s{sup -1}) were applied for the tests at RT. Although uniform elongation of F82H is relatively small at elevated temperature, true stress increases to fracture after necking starts. True stress decreases temporarily after yielding at 600 deg. C, but it increases again to fracture like the specimens tested at lower temperatures. Influence of strain rate to true stress-true strain relationship at room temperature was small, but unstable deformation occurred in narrower area at higher strain rate.

  11. Study of electroless Ni-W-P alloy coating on martensitic stainless steel

    Science.gov (United States)

    Nikitasari, Arini; Mabruri, Efendi

    2016-04-01

    Electroless nickel phospor (Ni-P) is widely used in many industries due to their corrosion and wear resistance, coating uniformity, and ability to coat non-conductive surfaces. The unique properties of tungsten such as high hardness, higher melting point, lower coefficient of linear thermal expansion, and high tensile strength have created a lot of interest in developing ternary Ni-W-P alloys. This article presents the study of electroless Ni-W-P alloys coating using acid or alkaline bath on martensitic stainless steel. Nickel sulfate and sodium tungstate were used as nickel and tungsten sources, respectively, and sodium hypophosphite was used as a reducing agent. Acid or alkaline bath refer to bath pH condition was adjusted by adding sulfuric acid. Martensitic stainless steel was immersed in Ni-W-P bath for 15, 30, and 60 minutes. The substrate of martensitic stainless steel was subjected to pre-treatment (polishing and cleaning) and activation prior to electroless plating. The plating characteristics were investigated for concentration ratio of nickel and hypophosphite (1:3), sodium tungstate concentration 0,1 M, immersion time (15 min, 30 min, 60 min), and bath condition (acid, alkaline). The electroless Ni-W-P plating was heat treated at 400°C for 1 hour. Deposits were characterized using scanning electron microscope (SEM) and corrosion measurement system (CMS).

  12. Stress-induced martensitic transformation in metastable austenitic stainless steels: Effect on fatigue crack growth rate

    Science.gov (United States)

    Khan, Z.; Ahmed, M.

    1996-04-01

    This paper addresses the influence of cyclic stress-induced martensitic transformation on fatigue crack growth rates in metastable austenitic stainless steels. At low applied stress and mean stress values in AISI type 301 stainless steel, fatigue crack growth rate is substantially retarded due to a cyclic stress-induced γ-α' and γ-ɛ martensitic transformation occurring at the crack-tip plastic zone. It is suggested that the transformation products produce a compressive residual stress at the tip of the fatigue crack, which essentially lowers the effective stress intensity and hence retards the fatigue crack growth rate. At high applied stress or mean stress values, fatigue crack growth rates in AISI type 301 steels become almost equal to those of stable AISI type 302 alloy. As the amount of transformed products increases (with an increase in applied or mean stress), the strain-hardening effect brought about by the transformed martensite phase appears to accelerate fatigue crack growth, offsetting the contribution from the compressive residual stress produced by the positive volume change of γ → α' or ɛ transformation.

  13. Anomalous steam oxidation behavior of a creep resistant martensitic 9 wt. % Cr steel

    Energy Technology Data Exchange (ETDEWEB)

    Agüero, Alina, E-mail: agueroba@inta.es [Instituto Nacional de Técnica Aeroespacial, Ctra. de Ajalvir Km 4, 28850 Torrejón de Ardoz (Spain); González, Vanessa [Instituto Nacional de Técnica Aeroespacial, Ctra. de Ajalvir Km 4, 28850 Torrejón de Ardoz (Spain); Mayr, Peter [Chair of Welding Engineering, Chemnitz University of Technology, Reichenhainer Str. 70, 09126 Chemnitz (Germany); Spiradek-Hahn, Krystina [Alloy Development Group, Montanuniversität Leoben, 8700 Leoben (Austria)

    2013-08-15

    The efficiency of thermal power plants is currently limited by the long-term creep strength and the steam oxidation resistance of the commercially available ferritic/martensitic steel grades. Higher operating pressures and temperatures are essential to increase efficiency but impose important requirements on the materials, from both the mechanical and chemical stability perspective. It has been shown that in general, a Cr wt. % higher than 9 is required for acceptable oxidation rates at 650 °C, but on the other hand such high Cr content is detrimental to the creep strength. Surprisingly, preliminary studies of an experimental 9 wt. % Cr martensitic steel, exhibited very low oxidation rates under flowing steam at 650 °C for exposure times exceeding 20,000 h. A metallographic investigation at different time intervals has been carried out. Moreover, scanning transmission electron microscopy (STEM) analysis of a ground sample exposed to steam for 10,000 h at 650 °C revealed the formation of a complex tri-layered protective oxide comprising a top and bottom Fe and Cr rich spinel layer with a magnetite intermediate layer on top of a very fine grained zone. - Highlights: • High steam oxidation resistant 9 wt. % Cr martensitic steel at 650 °C. • Multilayer thin protective Cr–Fe oxide. • Nano-grain sub-oxide metal zone.

  14. Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

    Science.gov (United States)

    Lu, Z.; Faulkner, R. G.; Morgan, T. S.

    2008-12-01

    High Cr ferritic/martensitic steels are leading candidates for structural components of future fusion reactors and new generation fission reactors due to their excellent swelling resistance and thermal properties. A commercial grade 12%CrMoVNb ferritic/martensitic stainless steel in the form of parent plate and off-normal weld materials was fast neutron irradiated up to 33 dpa (1.1 × 10 -6 dpa/s) at 400 °C and 28 dpa (1.7 × 10 -6 dpa/s) at 465 °C, respectively. TEM investigation shows that the fully martensitic weld metal transformed to a duplex austenite/ferrite structure due to high fluence neutron irradiation, the austenite was heavily voided (˜15 vol.%) and the ferrite was relatively void-free; whilst no austenite phases were detected in plate steel. Thermodynamic and phase equilibria software MTDATA has been employed for the first time to investigate neutron irradiation-induced phase transformations. The neutron irradiation effect is introduced by adding additional Gibbs free energy into the system. This additional energy is produced by high energy neutron irradiation and can be estimated from the increased dislocation loop density caused by irradiation. Modelling results show that neutron irradiation reduces the ferrite/austenite transformation temperature, especially for high Ni weld metal. The calculated results exhibit good agreement with experimental observation.

  15. Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z. [IPTME, Loughborough University, Loughborough LE11 3U (United Kingdom)], E-mail: zheng.lu@lboro.ac.uk; Faulkner, R.G.; Morgan, T.S. [IPTME, Loughborough University, Loughborough LE11 3U (United Kingdom)

    2008-12-01

    High Cr ferritic/martensitic steels are leading candidates for structural components of future fusion reactors and new generation fission reactors due to their excellent swelling resistance and thermal properties. A commercial grade 12%CrMoVNb ferritic/martensitic stainless steel in the form of parent plate and off-normal weld materials was fast neutron irradiated up to 33 dpa (1.1 x 10{sup -6} dpa/s) at 400 deg. C and 28 dpa (1.7 x 10{sup -6} dpa/s) at 465 deg. C, respectively. TEM investigation shows that the fully martensitic weld metal transformed to a duplex austenite/ferrite structure due to high fluence neutron irradiation, the austenite was heavily voided ({approx}15 vol.%) and the ferrite was relatively void-free; whilst no austenite phases were detected in plate steel. Thermodynamic and phase equilibria software MTDATA has been employed for the first time to investigate neutron irradiation-induced phase transformations. The neutron irradiation effect is introduced by adding additional Gibbs free energy into the system. This additional energy is produced by high energy neutron irradiation and can be estimated from the increased dislocation loop density caused by irradiation. Modelling results show that neutron irradiation reduces the ferrite/austenite transformation temperature, especially for high Ni weld metal. The calculated results exhibit good agreement with experimental observation.

  16. Report of IEA workshop on reduced activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-03-01

    IEA Workshop on Reduced Activation Ferritic/Martensitic Steels under implementing agreement for program of research and development on fusion materials was held at Tokyo Yayoi Kaikan and JAERI headquarter on November 2-3, 2000. The objective of this workshop was a review of the fusion material development programs, the progress of the collaboration and the irradiation effects studies on RAF/M steels in the collaborating parties (Europe, Russia the United States, and Japan). Moreover, the development of plans for future collaboration was discussed. The present report contains viewgraphs presented at the workshop. (author)

  17. INFLUENCE OF CARBON CONTENT OF MARTENSITE STEELS ON HARDNESS RE-DISTRIBUTION NEAR WORN SURFACE

    Institute of Scientific and Technical Information of China (English)

    Y.P. Ma

    2002-01-01

    After three-body abrasion, the hardness re-distribution near the worn surface has aclose relationship with the carbon content of martensite steel. It is considered thatthere is a competition between the work-hardening and the temper softening, whichresults from deformation and friction heat of material. When the carbon content ofmartensite steel is below about 0.6%, the subsurface hardness distribution of materialis a softened layer sandwiched between two hardened layers, but above 0.6%C, nosoftened region appears on the hardness re-distribution curve.

  18. Role of Nb in low interstitial 13Cr super martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ma, X.P.; Wang, L.J. [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110004 (China); Liu, C.M., E-mail: cmliu@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110004 (China); Subramanian, S.V. [Department of Materials Science and Engineering, McMaster University, Hamilton, L8S-4L7 (Canada)

    2011-08-25

    Highlights: {yields} Nb retards the kinetics of reversed austenite formation. {yields} Nb suppresses the occurrence of Cr rich precipitates. {yields} Nano-scale precipitates contribute to the significant increase in strength. - Abstract: The effect of adding 0.1 wt% Nb to low interstitial (N 0.01 wt%, C 0.01 wt%) 13Cr super martensitic stainless steel (SMSS) on solid phase transformation and microstructures achieved by normalizing and tempering was investigated using dilatometer, electron backscattered diffraction (EBSD), transmission electron microscope (TEM), X-ray diffraction (XRD), and its consequence on mechanical properties was examined to clarify the role of Nb in low interstitial martensitic stainless steel. Nb was found to retard kinetics of reversed austenite formation during tempering and to suppress the occurrence of Cr rich precipitates. The measurement of mechanical properties shows that while the strength properties were significantly increased by nano-scale precipitates enriched in Nb in the steel with 0.10 wt% Nb, the ductility and toughness properties were restored by optimum volume fraction of retained austenite. Excellent strength and adequate toughness properties were obtained by tempering the steel with 0.10 wt% Nb and low interstitial (N 0.01 wt%, C 0.01 wt%) steel at 600 deg. C.

  19. Ultrahigh Charpy impact toughness (~450J) achieved in high strength ferrite/martensite laminated steels.

    Science.gov (United States)

    Cao, Wenquan; Zhang, Mingda; Huang, Chongxiang; Xiao, Shuyang; Dong, Han; Weng, Yuqing

    2017-02-02

    Strength and toughness are a couple of paradox as similar as strength-ductility trade-off in homogenous materials, body-centered-cubic steels in particular. Here we report a simple way to get ultrahigh toughness without sacrificing strength. By simple alloying design and hot rolling the 5Mn3Al steels in ferrite/austenite dual phase temperature region, we obtain a series of ferrite/martensite laminated steels that show up-to 400-450J Charpy V-notch impact energy combined with a tensile strength as high as 1.0-1.2 GPa at room temperature, which is nearly 3-5 times higher than that of conventional low alloy steels at similar strength level. This remarkably enhanced toughness is mainly attributed to the delamination between ferrite and martensite lamellae. The current finding gives us a promising way to produce high strength steel with ultrahigh impact toughness by simple alloying design and hot rolling in industry.

  20. Ultrahigh Charpy impact toughness (~450J) achieved in high strength ferrite/martensite laminated steels

    Science.gov (United States)

    Cao, Wenquan; Zhang, Mingda; Huang, Chongxiang; Xiao, Shuyang; Dong, Han; Weng, Yuqing

    2017-01-01

    Strength and toughness are a couple of paradox as similar as strength-ductility trade-off in homogenous materials, body-centered-cubic steels in particular. Here we report a simple way to get ultrahigh toughness without sacrificing strength. By simple alloying design and hot rolling the 5Mn3Al steels in ferrite/austenite dual phase temperature region, we obtain a series of ferrite/martensite laminated steels that show up-to 400–450J Charpy V-notch impact energy combined with a tensile strength as high as 1.0–1.2 GPa at room temperature, which is nearly 3–5 times higher than that of conventional low alloy steels at similar strength level. This remarkably enhanced toughness is mainly attributed to the delamination between ferrite and martensite lamellae. The current finding gives us a promising way to produce high strength steel with ultrahigh impact toughness by simple alloying design and hot rolling in industry. PMID:28150692

  1. Temperature effect on the corrosion mechanism of austenitic and martensitic steels in lead-bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Benamati, G.; Fazio, C. E-mail: concetta@brasimone.enea.it; Piankova, H.; Rusanov, A

    2002-02-01

    Compatibility tests on the austenitic AISI 316L and the martensitic MANET II steels in stagnant PbBi were performed at 573, 673 and 823 K with exposures up to 5000 h. The change of the corrosion mechanism with increasing temperature has been evaluated. The results showed that at 573 and 673 K a thin oxide layer growth on the surface of both steels. By increasing the temperature to 823 K both types of steels were attacked by the liquid metal and dissolution of the steel alloying elements has been observed. The herein-reported experimental activities were performed in collaboration with the IPPE of Obninsk, where preliminary dynamic tests were performed in the experimental facility CU-2. The Russian ferritic-martensitic steel EP823 has been exposed to flowing PbBi at 623, 723 and 823 K for 700 h. After 700 h of testing, the surface of the EP823 samples showed for the three temperatures a compact oxide layer.

  2. Impact toughness of tungsten films deposited on martensite stainless steel

    Institute of Scientific and Technical Information of China (English)

    HUANG Ning-kang; YANG Bin; WANG De-zhi

    2005-01-01

    Tungsten films were deposited on stainless steel Charpy specimens by magnetron sputtering followed by electron beam heat treatment. Charpy impact tests and scanning electron microscopy were used to investigate the ductile-brittle transition behavior of the specimens. With decreasing test temperature the fracture mode was transformed from ductile to brittle for both kinds of specimens with and without W films. The data of the crack initiation energy, crack propagation energy, impact absorbing energy, fracture time and deflection as well as the fracture morphologies at test temperature of -70 ℃ show that W films can improve the impact toughness of stainless steel.

  3. Grain Refinement of Low Carbon Martensitic Steel by Heat Treatment

    Directory of Open Access Journals (Sweden)

    N. V. Kolebina

    2015-01-01

    Full Text Available The low-carbon steels have good corrosion and technological properties. Hot deformation is the main operation in manufacturing the parts from these steels. So one of the important properties of the material is a property of plasticity. The grain size significantly influences on the ductility properties of steel. The grain size of steel depends on the chemical composition of the crystallization process, heat treatment, and steel machining. There are plenty methods to have grain refinement. However, taking into account the large size of the blanks for the hydro turbine parts, the thermal cycling is an advanced method of the grain refinement adaptable to streamlined production. This work experimentally studies the heat treatment influence on the microstructure of the low-carbon 01X13N04 alloy steel and proposes the optimal regime of the heat treatment to provide a significantly reduced grain size. L.M. Kleiner, N.P. Melnikov and I.N. Bogachyova’s works focused both on the microstructure of these steels and on the influence of its parameters on the mechanical properties. The paper focuses mainly on defining an optimal regime of the heat treatment for grain refinement. The phase composition of steel and temperature of phase transformation were defined by the theoretical analysis. The dilatometric experiment was done to determine the precise temperature of the phase transformations. The analysis and comparison of the experimental data with theoretical data and earlier studies have shown that the initial sample has residual stress and chemical heterogeneity. The influence of the heat treatment on the grain size was studied in detail. It is found that at temperatures above 950 ° C there is a high grain growth. It is determined that the optimal number of cycles is two. The postincreasing number of cycles does not cause further reducing grain size because of the accumulative recrystallization process. Based on the results obtained, the thermal cycling

  4. Relation of martensite-retained austenite and its effect on microstructure and mechanical properties of the quenched and partitioned steels

    Institute of Scientific and Technical Information of China (English)

    WANG CunYu; CHANG Ying; LI XiaoDong; ZHAO KunMin; DONG Han

    2016-01-01

    A two-step quenching and partitioning (Q&P) treatment was applied to low-carbon alloy steels.The relation of initial martensite-retained austenite-fresh martensite and its effect on microstructure and mechanical properties were investigated by experiments.The results reveal that the volume fraction of retained austenite can reach the peak value of 17%,and the corresponding volume fractions of initial martensite and fresh martensite are 40% and 43%,respectively,when the tested steel is treated by initial quenching at 330℃,partitioning at 500℃ for 60s and final quenching to room temperature.Moreover,the micromorphologies of austenite and martensite become finer with the increasing of initial martensite fraction.The elongation is the highest when the volume fractions of initial martensite and retained austenite are 70% and 11%,respectively,meanwhile,the yield strength increases and tensile strength decreases gradually with the increase of initial martensite fraction,which proves that the mechanical properties including elongation,yield strength and tensile strength are based on the comprehensive effect of the retained austenite fraction,the finer microstructure and austenite stability.

  5. Static recrystallization behavior of a martensitic heat-resistant stainless steel 403Nb

    Institute of Scientific and Technical Information of China (English)

    Zhouyu ZENG; Liqing CHEN; Fuxian ZHU; Xianghua LIU

    2011-01-01

    A static recrystallization behavior between the rolling passes of a martensitic heatresistant stainless steel 403Nb has been studied by OM,TEM and double-hit thermomechanical simulator to explore the effects of deformation temperature,strain rate,strain and the prior austenite grain size.The results show that increases of deformation temperature and strain rate and strain can promote the static recrystallization of 403Nb steel.Static recrystallization also proceeds faster when the prior austenite grain size is smaller.Microstructural observation indicates that the volume fraction of static recrystallization increases with prolonged interval of the rolling passes.Straininduced precipitation can lead to an appearance of a platform in the kinetic curve of static recrystallization.Different from the conventional micro-alloying steel,the strain-induced precipitates in 403Nb steel during hot rolling are carbides containing Nb and Cr.

  6. Development of Advanced 9Cr Ferritic-Martensitic Steels and Austenitic Stainless Steels for Sodium-Cooled Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Sham, Sam [ORNL; Tan, Lizhen [ORNL; Yamamoto, Yukinori [ORNL

    2013-01-01

    Ferritic-martensitic (FM) steel Grade 92, with or without thermomechanical treatment (TMT), and austenitic stainless steels HT-UPS (high-temperature ultrafine precipitate strengthening) and NF709 were selected as potential candidate structural materials in the U.S. Sodium-cooled Fast Reactor (SFR) program. The objective is to develop advanced steels with improved properties as compared with reference materials such as Grade 91 and Type 316H steels that are currently in nuclear design codes. Composition modification and/or processing optimization (e.g., TMT and cold-work) were performed to improve properties such as resistance to thermal aging, creep, creep-fatigue, fracture, and sodium corrosion. Testings to characterize these properties for the advanced steels were conducted by the Idaho National Laboratory, the Argonne National Laboratory and the Oak Ridge National Laboratory under the U.S. SFR program. This paper focuses on the resistance to thermal aging and creep of the advanced steels. The advanced steels exhibited up to two orders of magnitude increase in creep life compared to the reference materials. Preliminary results on the weldment performance of the advanced steels are also presented. The superior performance of the advanced steels would improve reactor design flexibility, safety margins and economics.

  7. A Study on Sodium Effects on the Mechanical Properties of Ferritic-Martensitic Steels

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sang Hun; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Kim, Jun Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    A sodium-cooled fast reactor (SFR) that uses fast neutrons as a fission process is considered one of the most probable candidates in next generation reactors. As an SFR core experiences high temperatures (650 .deg. C) and neutron doses (200 dpa), ferritic-martensitic steel, especially HT9 steel containing 12% Cr, is being considered due to its superior dimensional stability against high-energy neutron irradiation. After irradiation to 35 dpa at 420 .deg. C, at the Fast Flux Test Facility (FFTF), swelling of the reduced-activation 9Cr-2WV and 9Cr-2WVTa steels and the conventional 9Cr-1Mo-VNb and 12Cr-1Mo-VW steels was estimated by transmission electron microscopy (TEM) to be 0.2%, 0.33%, 0.85%, and 0.007%, respectively. The irradiation creep coefficient for neutron-irradiated steels is 2 Χ 10{sup -7} Mpa{sup -1} dpa{sup -1} for HT9 at 440-500 .deg. C with 14 dpa (EBR-II), and 1.5 Χ 10{sup -7} Mpa{sup -1} dpa{sup -1} is a good estimate for such ferritic/martensitic steels. In this study, ASTM A192 Gr. 92 steels were exposed to liquid sodium at 650 .deg. C for 1583 h and 3095 h and evaluation of the microstructure as well as the mechanical properties using ring hoop tensile tests and ring hoop creep tests were conducted. The objective of this study is to evaluate the microstructure and mechanical properties of ferritic-martensitic steel (ASTM A192 Gr. 92) that has been exposed to a high-temperature sodium environment. In order to investigate the effect of the aging process on the precipitates and the mechanical properties of Gr. 92 steel, specimens were exposed to 650 .deg. C liquid sodium and aged in a 650 .deg. C argon environment for a given time. V-rich MX-type carbonitride and M{sub 23}C{sub 6} were found in the as-received specimen. In the specimens which were exposed to sodium, mainly Cr{sub 23}C{sub 6} was observed while the Laves phase was mainly observed in the specimen that was aged in an argon environment. The maximum load of Gr. 92 steel that was

  8. Prediction of diffusion assisted hydrogen embrittlement failure in high strength martensitic steels

    Science.gov (United States)

    Wu, Q.; Zikry, M. A.

    2015-12-01

    A stress assisted hydrogen diffusion transport model, a dislocation-density-based multiple-slip crystalline plasticity formulation, and an overlapping fracture method were used to investigate hydrogen diffusion and embrittlement in lath martensitic steels with distributions of M23C6 carbide precipitates. The formulation accounts for variant morphologies based on orientation relationships (ORs) that are uniquely inherent to lath martensitic microstructures. The interrelated effects of martensitic block and packet boundaries and carbide precipitates on hydrogen diffusion, hydrogen assisted crack nucleation and growth, are analyzed to characterize the competition between cleavage fracture and hydrogen diffusion assisted fracture along preferential microstructural fracture planes. Stresses along the three cleavage planes and the six hydrogen embrittlement fracture planes are monitored, such that crack nucleation and growth can nucleate along energetically favorable planes. High pressure gradients result in the accumulation of hydrogen, which embrittles martensite, and results in crack nucleation and growth along {110} planes. Cleavage fracture occurs along {100} planes when there is no significant hydrogen diffusion. The predictions indicate that hydrogen diffusion can suppress the emission and accumulation of dislocation density, and lead to fracture with low plastic strains.

  9. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    Science.gov (United States)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2016-05-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dissolution during the second, higher temperature, stage. A better homogenization of the material causes an increase in the transformation temperatures for the martensite-to-austenite transformation and a lower retained austenite fraction with less variability after tempering. Furthermore, the martensite-to-austenite transformation was found to be incomplete at the target temperature of 1223 K (950 °C), which is influenced by the previous austenitization treatment and the heating rate. The activation energy for martensite-to-austenite transformation was determined by a modified Kissinger equation to be approximately 400 and 500 kJ/mol for the first and the second stages of transformation, respectively. Both values are much higher than the activation energy found during isothermal treatment in a previous study and are believed to be effective activation energies comprising the activation energies of both mechanisms involved, i.e., nucleation and growth.

  10. Martensite and bainite in nanocrystalline steels: understanding, design and applications

    Directory of Open Access Journals (Sweden)

    Caballero Francisca G.

    2015-01-01

    Full Text Available There are major difficulties in creating novel nanocrystalline structures that have a combination of properties appropriate for large scale applications. An important requirement is to be able to manufacture nanocrystalline components which are large in all dimensions on their macroscale whilst retaining their nanostructure. In addition, the material concerned must be cheap to produce if it is not to be limited to niche applications. Severe plastic deformation has not succeeded in this respect since grain growth cannot effectively be suppressed during consolidation processes. Therefore, processing bulk nanocrystalline materials for structural applications still poses a big challenge, particularly in achieving an industrially viable process. Here we describe various processing strategies and alloy developments currently being explored in the modern steel industry that have the potential to create extremely strong and affordable nanocrystalline engineering steels.

  11. Analysis of the strain induced martensitic transformation in austenitic steel subjected to dynamic perforation

    Directory of Open Access Journals (Sweden)

    Zaera R.

    2012-08-01

    Full Text Available An experimental and numerical analysis on the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is reported. Two target thicknesses are considered, 0.5 and 1.0 mm, and impact velocities range from 35 to 200 m/s. The perforation mechanisms are identified and the effect of the projectile nose-shape on the ability of the target for energy absorption is evaluated. Martensite has been detected in all the impacted samples and the role played by the projectile nose-shape on the transformation is highlighted. A 3D model implemented in ABAQUS/Explicit allowed to simulate the perforation tests. The material is defined through a constitutive description developed by the authors to describe the strain induced martensitic transformation taking place in metastable austenitic steels at high strain rates. The numerical results are compared with the experimental evidence and satisfactory matching is obtained. The numerical model succeeds in describing the perforation mechanisms associated to each projectile-target configuration analysed.

  12. Influence of PWHT on Toughness of High Chromium and Nickel Containing Martensitic Stainless Steel Weld Metals

    Science.gov (United States)

    Divya, M.; Das, Chitta Ranjan; Mahadevan, S.; Albert, S. K.; Pandian, R.; Kar, Sujoy Kumar; Bhaduri, A. K.; Jayakumar, T.

    2015-06-01

    Commonly used 12.5Cr-5Ni consumable specified for welding of martensitic stainless steels is compared with newly designed 14.5Cr-5Ni consumable in terms of their suitability for repair welding of 410 and 414 stainless steels by gas tungsten arc welding process. Changes in microstructure and austenite evolution were investigated using optical, scanning electron microscopy, X-ray diffraction techniques and Thermo-Calc studies. Microstructure of as-welded 12.5Cr-5Ni weld metal revealed only lath martensite, whereas as-welded 14.5Cr-5Ni weld metal revealed delta-ferrite, retained austenite, and lath martensite. Toughness value of as-welded 12.5Cr-5Ni weld metal is found to be significantly higher (216 J) than that of the 14.5Cr-5Ni weld metal (15 J). The welds were subjected to different PWHTs: one at 923 K (650 °C) for 1, 2, 4 hours (single-stage PWHT) and another one at 923 K (650 °C)/4 h followed by 873 K (600 °C)/2 h or 873 K (600 °C)/4 h (two-stage heat treatment). Hardness and impact toughness of the weld metals were measured for these weld metals and correlated with the microstructure. The study demonstrates the importance of avoiding formation of delta-ferrite in the weld metal.

  13. Neodymium-rich precipitate phases in a high-chromium ferritic/martensitic steel

    Science.gov (United States)

    Shen, Yinzhong; Zhou, Xiaoling; Shang, Zhongxia

    2016-05-01

    Neodymium being considered as nitride forming element has been used in a design of advanced ferritic/martensitic (FM) steels for fossil fired power plants at service temperatures of 630 °C to 650 °C to effectively improve the creep strength of the steels. To fully understand the characteristics of neodymium precipitates in high-Cr FM steels, precipitate phases in an 11Cr FM steel with 0.03 wt% addition of Nd have been investigated by transmission electron microscopy. Three neodymium phases with a face-centered cubic crystal structure and different composition were observed in the steel. They consisted of neodymium carbonitride with an average lattice parameter of 1.0836 nm, Nd-rich carbonitride mainly containing Mn, and Nd-rich MN nitride mainly containing Mn and Co. Other three Nd-rich and Nd-containing phases, which appear to be Nd-Co-Cr/Nd-rich intermetallic compounds and Cr-Fe-rich nitride containing Nd, were also detected in the steel. Nd-relevant precipitates were found to be minor phases compared with M23C6 and Nb/V/Ta-rich MX phases in the steel. The content of Nd in other precipitate phases was very low. Most of added Nd is considered to be present as solid solution in the matrix of the steel.

  14. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    NARCIS (Netherlands)

    Chernov, [No Value; Kalashnikov, AN; Kahn, BA; Binyukova, SY

    2003-01-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion it. radiation up to a fluence of 5 x 10(20) m(-2) at the temperature of 920 K. It

  15. Oxidation/Corrosion Behaviour of ODS Ferritic/Martensitic Steels in Pb Melt at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    O. I. Yaskiv

    2014-01-01

    Full Text Available Lead-based melts (Pb, Pb-Bi are considered as candidate coolants and spallation neutron targets due to their excellent thermophysical and nuclear properties. However, the corrosion of structural materials remains a major issue. Oxide dispersion strengthened (ODS ferritic/martensitic steels are considered for high temperature application for both fission and fusion reactor concepts. The oxidation/corrosion kinetics in a static oxygen-saturated Pb melt at temperature of 550°C as well as the morphology and composition of scales formed on ferritic/martensitic Fe-9Cr-1.5W and ferritic Fe-14Cr-1.5W ODS steels have been investigated. Both materials showed homogeneous multiple, dense scales that consisted of typical combination of Fe3O4 as outer sublayer and (Fe,Cr3O4 as inner sublayer. A nonuniform growth of inner oxide sublayers into the metal matrix as well as a good adhesion to the metal substrate is observed. With the prolongation of exposure from 240 to 1000 h, observed scales grow from 35 µm to 45 µm for ODS Fe-9Cr steel and from 40 µm to 60 µm for ODS Fe-14Cr steel with the thinning rates of 0,22 and 0,31 mm/year correspondingly. The mechanism of scales formation is discussed.

  16. Analysis of deformation induced martensite in AISI 316L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Jagarinec, Darko; Kirbis, Peter; Predan, Jozef; Vuherer, Tomaz; Gubeljak, Nenad [Maribor Univ. (Slovenia). Faculty of Mechanical Engineering

    2016-08-01

    Metastable austenite stainless steel AISI 316L is sensitive to cold deformation, where transformation from austenite to martensite occurred. The bending deformation as the formation process leads to tensile and compression throughout the thickness of the billet. Tensile testing of the specimen causes differences in the true stress-strain along the contraction neck prior to fracture as well. The aim of the paper is to find correlation between microhardness as brief inspection parameters and extension of martensitic transformation. The total equivalent plastic strain extend diagram obtained by numerical simulation of bending was compared with tensile true stress-strain diagram. Results show very good correlation between hardness, true strain and martesite content. Therefore, one can conclude that by hardness measurement, it is possible to measure the level of equivalent plastic strain until ultimate tensile stress as a linear correlation between hardness, true strain and martesite content.

  17. Microstructure effect on nanohardness distribution for medium-carbon martensitic steel

    Institute of Scientific and Technical Information of China (English)

    LI; Jinxu; OHMURA; Takahito; TSUZAKI; Kaneaki

    2006-01-01

    Nanoindentation measurement was performed to evaluate the local hardness distribution for quenched and tempered martensitic steel with ferrite-cementite constituent. The ratio of standard deviation to the average nanohardness was 15.4% when nanoindentation tests were carried out at the peak load of 1000 μN, while that of the Vickers hardness was only 1.5% at 9.8 N. Electron backscatter diffraction analysis and SEM observation all showed that the large scattering of nanohardness did not depend on the crystallographic orientation of each grain but from the inhomogeneous microstructure in the sub-micron scale such as cementite distribution. Compared with the results on tungsten single crystals with different surface orientations as well as another martensite processed by modified-ausforming with the same chemical composition but more homogeneous cementite distribution, the nanohardness showed smaller scattering, supporting the conclusion.

  18. Formation of Nanocrystalline Structure in 301 Stainless Steel Produced by Martensite Treatment

    Science.gov (United States)

    Eskandari, M.; Kermanpur, A.; Najafizadeh, A.

    2009-09-01

    The present work aims to obtain the optimum parameters of a thermomechanical treatment for developing a nanocrystalline structure in as-cast AISI 301 austenitic stainless steel. In the first step, the effect of homogenization times of 3 to 13 hours at 1200 °C on the grain size of hot-rolled specimens was studied. The results showed the minimum grain size obtained with homogenization at 1200 °C for 9 hours after hot rolling at the temperature range of 1000 °C to 1200 °C, strain of 0.8, and strain rate of 1.2 s-1. In the second stage, the effects of strain, initial grain size, rolling temperature, and strain path were examined on martensite formation in a thermomechanical process consisting of cold rolling and subsequent annealing. Cold rolling was carried out at -196 °C, -10 °C, and 0 °C with a strain rate of 0.5 s-1 and reductions of 10 to 95 pct, while annealing treatment was conducted at 600 °C to 850 °C for 1 to 50 minutes. The results showed that decreasing the rolling temperature and increasing the strain and initial grain size plus the use of cross rolling resulted in increased volume fraction of the strain-induced martensite during cold rolling and in reduced martensite saturating strain from 0.7 to 0.2, the overall result being enhanced grain refinement of the steel sheets produced. The nanocrystalline austenitic structure with a grain size of about 60 to 80 nm was produced by annealing at 850 °C for 1 minute from the strain-induced martensitic structure formed during cold rolling. It was found that the effect of grain size prior to cold rolling was more pronounced on grain refinement than thickness reduction.

  19. Neutron irradiation effects on the ductile-brittle transition of ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J. [Oak Ridge National Lab., TN (United States)

    1997-08-01

    Ferritic/martensitic steels such as the conventional 9Cr-1MoVNb (Fe-9Cr-1Mo-0.25V-0.06Nb-0.1C) and 12Cr-1MoVW (Fe-12Cr-1Mo-0.25V-0.5W-0.5Ni-0.2C) steels have been considered potential structural materials for future fusion power plants. The major obstacle to their use is embrittlement caused by neutron irradiation. Observations on this irradiation embrittlement is reviewed. Below 425-450{degrees}C, neutron irradiation hardens the steels. Hardening reduces ductility, but the major effect is an increase in the ductile-brittle transition temperature (DBTT) and a decrease in the upper-shelf energy, as measured by a Charpy impact test. After irradiation, DBTT values can increase to well above room temperature, thus increasing the chances of brittle rather than ductile fracture.

  20. Damage behavior in helium-irradiated reduced-activation martensitic steels at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Chen, Jihong; Li, Tiecheng; Zheng, Zhongcheng [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yao, Z. [Department of Mechanical and Materials Engineering, Queen’s University, Kingston K7L 3N6, ON (Canada); Suo, Jinping [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-12-15

    Dislocation loops induced by helium irradiation at elevated temperatures in reduced-activation martensitic steels were investigated using transmission electron microscopy. Steels were irradiated with 100 keV helium ions to 0.8 dpa between 300 K and 723 K. At irradiation temperatures T{sub irr} ⩽ 573 K, small defects with both Burger vectors b = 1/2〈1 1 1〉 and b = 〈1 0 0〉 were observed, while at T{sub irr} ⩾ 623 K, the microstructure was dominated by large convoluted interstitial dislocation loops with b = 〈1 0 0〉. Only small cavities were found in the steels irradiated at 723 K.

  1. Development of Reduced Activation Ferritic-Martensitic Steels and fabrication technologies for Indian test blanket module

    Energy Technology Data Exchange (ETDEWEB)

    Raj, Baldev [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Jayakumar, T., E-mail: tjk@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

    2011-10-01

    For the development of Reduced Activation Ferritic-Martensitic Steel (RAFMS), for the Indian Test Blanket Module for ITER, a 3-phase programme has been adopted. The first phase consists of melting and detailed characterization of a laboratory scale heat conforming to Eurofer 97 composition, to demonstrate the capability of the Indian industry for producing fusion grade steel. In the second phase which is currently in progress, the chemical composition will be optimized with respect to tungsten and tantalum for better combination of mechanical properties. Characterization of the optimized commercial scale India-specific RAFM steel will be carried out in the third phase. The first phase of the programme has been successfully completed and the tensile, impact and creep properties are comparable with Eurofer 97. Laser and electron beam welding parameters have been optimized and welding consumables were developed for Narrow Gap - Gas Tungsten Arc welding and for laser-hybrid welding.

  2. Dynamic fracture toughness and Charpy impact properties of an AISI 403 martensitic stainless steel

    Science.gov (United States)

    Sreenivasan, P. R.; Ray, S. K.; Mannan, S. L.; Rodriguez, P.

    1996-04-01

    Dynamic fracture toughness and Charpy impact properties of a normalised and tempered AISI 403 martensitic stainless steel obtained from instrumented impact tests are presented. Procedures for estimating dynamic fracture toughness ( KId) from the load-time traces obtained in instrumented tests of unprecracked Charpy V-notch (CVN) specimens are considered. The estimated KId values show reasonable agreement with those obtained from instrumented drop-weight and precracked Charpy tests. Also, except in the upper transition and uppershelf regions, the ASME KIR curve is generally conservative (i.e. gives lower KId values) when compared to the above KId estimates. The conservatism of the ASME KIR at the upper transition and uppershelf temperatures needs verification/validation. The lowest KId values estimated at the lower shelf temperatures for the above steel, namely, 33-42 MPa√m are in good agreement with the reported values of 35-50 MPa√m for the same steel in the literature.

  3. Influence of Z-phase on long-term creep stability of martensitic 9-12% Cr steels

    Energy Technology Data Exchange (ETDEWEB)

    Danielsen, Hilmar K. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Mechanical Engineering; Hald, John [DONG Energy A/S (Denmark); Vattenfall (Denmark)

    2010-07-01

    The long-term creep strength of the new generation of martensitic creep resistant 9-12%Cr steels since the well-known steel Grade 91 relies strongly on particle strengthening by fine Mn nitrides based on V and Nb. During long-term high-temperature exposures the Mn nitrides may be replaced by the thermodynamically more stable Z-phases (Cr(V,Nb)N) causing a breakdown in creep strength. Cr contents above 10.5% strongly accelerate Z-phase precipitation, which explains the lack of success for all attempts to develop martensitic creep resistant steels with high Cr content for oxidation protection. However 9%Cr steels do not seem to be affected by the Z-phase. Careful control of the Z-phase precipitation process has led to the design of experimental 12%Cr martensitic steels strengthened by fine Z-phase nitrides based on Nb or Ta. Such steels may again enable the combination of high strength and oxidation resistance in the same alloy. This opens a new pathway for further alloy development of the heat resistant martensitic steels. (orig.)

  4. Impact resistance and fractography of low-alloy martensitic steels

    Directory of Open Access Journals (Sweden)

    S. Frydman

    2008-03-01

    Full Text Available In this paper dynamic properties of HTK SOOH, HTK 900H. Hardox 400 and Hardox 500 steeZs in delivcrcd stalc (aftcr hardening andtempering are considered. Charpy V - notch (CVN test rcsults in connection with fractography in the ductilc - to - brittle transitionternpcrature region were analyzed. The impact transition curve obtained from CVN tcst not always predicts properly a behavior ofmaterials in conditions of dynamic loading, so the analyze of character of fracture helps to evalitate the rcal bchavior of ma~crials. Tcstcdsamples were cut out longitudinally and transversely in relation to cold work direction. The results of CVN test far investigated steels, inthe range of temperatures from 40t o 20 "C are presented. Regarding ductilc - to - bri~tlel ransition temperature, there is a significantdiffcrcnce taking into account vatues of Charpy V cncrgy absorbcd and a character of fracture.

  5. Influence of Mo addition on the tempered properties of 13Cr martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Byong Ho; Ahn, Yong Sik [Pukyong National Univ., Busan (Korea, Republic of)

    1998-11-01

    In order to investigate the effect of Mo addition on the mechanical properties of 13Cr-0.2C martensitic stainless steel, tensile test and Charpy V-notch test were performed after tempering at the temperature range of 200{approx}700 .deg. C following austenitizing at 1100 .deg. C. The yield strength and hardness of the steel were increased with the increase of Mo content at all tempering conditions, because Mo causes retardation of precipitation and coarsening of carbides and solid solution strengthening of matrix. Except 500 .deg. C of tempering temperature, the Charpy impact energy was significantly increased with Mo content and showed the highest value at 1.5 wt% addition. The increase of impact energy of the steel containing Mo is thought to be caused by {delta}-ferrite formed in the tempered martensitic matrix. At 500 .deg. C tempering, Charpy impact energy was decreased drastically due to temper embrittlement and it was not possible to prevent it even though Mo was added up to 1.5 wt%.

  6. Diffusion bonding beryllium to Reduced Activation Ferritic Martensitic steel: Development of processes and techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, R.M., E-mail: hunt52@llnl.gov [Mechanical and Aerospace Engineering Department, UCLA, 44-128 Engineering IV, 420 Westwood Plaza, Los Angeles, CA 90025-1597 (United States); Goods, S.H., E-mail: shgoods@sandia.gov [Sandia National Laboratories (United States); Ying, A., E-mail: ying@fusion.ucla.edu [Mechanical and Aerospace Engineering Department, UCLA, 44-128 Engineering IV, 420 Westwood Plaza, Los Angeles, CA 90025-1597 (United States); Dorn, C.K., E-mail: christopher.dorn@materion.com [Materion Brush Beryllium and Composites (United States); Abdou, M., E-mail: abdou@fusion.ucla.edu [Mechanical and Aerospace Engineering Department, UCLA, 44-128 Engineering IV, 420 Westwood Plaza, Los Angeles, CA 90025-1597 (United States)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer We diffusion bonded Be to Reduced Activation Ferritic Martensitic steel. Black-Right-Pointing-Pointer Thin copper and titanium interlayers improved the bond's shear strength to 168 MPa. Black-Right-Pointing-Pointer A slow cooling scheme and intermediate hold step greatly increased bond strength. Black-Right-Pointing-Pointer Failure occurred in Be-Ti and Cu-Ti intermetallic compounds. - Abstract: Beryllium was successfully bonded to a Reduced Activation Ferritic Martensitic (RAFM) steel with a maximum strength of 150 MPa in tension and 168 MPa in shear. These strengths were achieved using Hot Isostatic Pressing (HIP), at temperatures between 700 Degree-Sign C and 750 Degree-Sign C for 2 h and under a pressure of 103 MPa. To obtain these strengths, 10 {mu}m of titanium and 20 {mu}m of copper were deposited on the beryllium substrate prior to HIP bonding. The copper film acted a bonding aid to the RAFM steel, while the titanium acted as a diffusion barrier between the copper and the beryllium, suppressing the formation of brittle intermetallics that are known to compromise mechanical performance. Slow cooling from the peak HIP temperature along with an imposed hold time at 450 Degree-Sign C further enhanced the final mechanical strength of the bond.

  7. Development of new martensitic stainless steels for OCTG: The challenges for the steelmaker and the tubemaker

    Energy Technology Data Exchange (ETDEWEB)

    Jackman, P.S. [British Steel plc, Northants (United Kingdom). Tube Sales and Services Ltd.; Everson, H. [UES Steels, Sheffield (United States)

    1995-10-01

    Martensitic stainless steels have been widely used in the oil industry for Oil Country Tubular Goods (OCTG) over more than 25 years but have recently seen their field of use expanded by the development of ``Super`` 13%Cr alloys. This paper describes the design process and development of Super 13%Cr alloys in the United Kingdom to meet the oil and gas industry`s requirements while recognizing the manufacturing constraints on the steelmaker and tubemaker. The mechanical properties and corrosion resistance are described.

  8. Precipitation behavior in a nitride-strengthened martensitic heat resistant steel during hot deformation

    Directory of Open Access Journals (Sweden)

    Wenfeng Zhang

    2015-09-01

    Full Text Available The stress relaxation curves for three different hot deformation processes in the temperature range of 750–1000 °C were studied to develop an understanding of the precipitation behavior in a nitride-strengthened martensitic heat resistant steel (Zhang et al., Mater. Sci. Eng. A, 2015 [1]. This data article provides supporting data and detailed information on how to accurately analysis the stress relaxation data. The statistical analysis of the stress peak curves, including the number of peaks, the intensity of the peaks and the integral value of the pumps, was carried out. Meanwhile, the XRD energy spectrum data was also calculated in terms of lattice distortion.

  9. Compression behavior of a ferritic-martensitic Cr-Mo steel

    DEFF Research Database (Denmark)

    Zhang, Zhenbo; Mishin, Oleg; Pantleon, Wolfgang

    2012-01-01

    The compression behavior of a ferritic-martensitic Cr-Mo steel is characterized for strain rates ranging from 10-4 s-1 to 10-1 s-1 and engineering strains up to 40%. Adiabatic heating causes a reduction in flow stress during continuous compression at a strain rate of 10-1 s-1. No reduction...... in the flow stress is observed if interrupted compression tests are performed with loading and holding steps. Two work-hardening stages with work-hardening rates decreasing linearly with the flow stress are identified and interpreted in terms of the KocksMecking model. The microstructural evolution...

  10. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    OpenAIRE

    2016-01-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dis...

  11. Radiation hardening and deformation behavior of irradiated ferritic-martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, J.P.; Klueh, R.L.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States); Shiba, K. [Japan Atomic Energy Research Inst. (Japan)

    1998-03-01

    Tensile data from several 8--12% Cr alloys irradiated in the High Flux Isotope Reactor (HFIR) to doses up to 34 dpa at temperatures ranging from 90 to 600 C are discussed in this paper. One of the critical questions surrounding the use of ferritic-martensitic steels in a fusion environment concerns the loss of uniform elongation after irradiation at low temperatures. Irradiation and testing at temperatures below 200--300 C results in uniform elongations less than 1% and stress-strain curves in which plastic instability immediately follows yielding, implying dislocation channeling and flow localization. Reductions in area and total elongations, however, remain high.

  12. {225}γ habit planes in martensitic steels: from the PTMC to a continuous model

    Science.gov (United States)

    Baur, Annick P.; Cayron, Cyril; Logé, Roland E.

    2017-01-01

    Fine twinned microstructures with {225}γ habit planes are commonly observed in martensitic steels. The present study shows that an equibalanced combination of twin-related variants associated to the Kurdjumov-Sachs orientation relationship is equivalent to the Bowles and Mackenzie’s version of the PTMC for this specific {225}γ case. The distortion associated to the Kurdjumov-Sachs orientation relationship results from a continuous modeling of the FCC-BCC transformation. Thus, for the first time, an atomic path can be associated to the PTMC. PMID:28106127

  13. Formation quality optimization of laser hot wire cladding for repairing martensite precipitation hardening stainless steel

    Science.gov (United States)

    Wen, Peng; Feng, Zhenhua; Zheng, Shiqing

    2015-01-01

    Laser cladding is an advantaged repairing technology due to its low heat input and high flexibility. With preheating wire by resistance heat, laser hot wire cladding shows better process stability and higher deposition efficiency compared to laser cold wire/powder cladding. Multi-pass layer were cladded on the surface of martensite precipitation hardening stainless steel FV520B by fiber laser with ER410NiMo wire. Wire feed rate and preheat current were optimized to obtain stable wire transfer, which guaranteed good formation quality of single pass cladding. Response surface methodology (RSM) was used to optimize processing parameters and predict formation quality of multi-pass cladding. Laser power P, scanning speed Vs, wire feed rate Vf and overlap ratio η were selected as the input variables, while flatness ratio, dilution and incomplete fusion value as the responses. Optimal clad layer with flat surface, low dilution and no incomplete fusion was obtained by appropriately reducing Vf, and increasing P, Vs and η. No defect like pore or crack was found. The tensile strength and impact toughness of the clad layer is respectively 96% and 86% of those of the substrate. The clad layer showed nonuniform microstructure and was divided into quenched areas with coarse lath martensite and tempered areas with tempered martensite due to different thermal cycles in adjacent areas. The tempered areas showed similar hardness to the substrate.

  14. Burst Martensitic Transformations in a Steel and in a Pu-Ga Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Blobaum, K; Krenn, C; Wall, M; Schwartz, A

    2005-06-14

    Upon cooling a Pu-2.0 at% Ga alloy from the ambient temperature, the metastable delta phase partially transforms martensitically to the alpha-prime phase. Because this transformation involves a 25% volume contraction, plastic accommodation by the delta matrix must occur. When the material is isochronally heated or isothermally annealed above ambient temperatures, the reversion of alpha-prime to delta is likely to occur by the alpha-prime/delta interface moving to consume the alpha-prime particles. This reversion exhibits a burst martensitic mode and is observed as sharp spikes in differential scanning calorimetry data and as steps in resistometry data. These large bursts appear to be the result of an interplay between the autocatalytically driven transformation of individual alpha-prime particles and self-quenching caused by small changes in temperature and/or stress accompanying each burst. The behavior of this Pu-Ga alloy is compared to that of a steel referred to as a ''burst martensite'' in the literature, which also exhibits bursts during both thermal cycling and isothermal holds.

  15. Effect of tempering temperature and Mo content on the corrosion behavior of 13Cr martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Jong Woo; Ahn, Yong Sik; Park, Hwa Soon [Pukyong National Univ., Busan (Korea, Republic of)

    1999-07-01

    Martensitic stainless steel has high strength and hardness in comparison with other stainless steels. But the toughness and corrosion resistance is lower. So lots of researches have been done in order to improve these properties. In the previous study the alloying element of Mo resulted in increasing the toughness at tempered condition of the steel. It has been investigated in this work how the Mo addition and tempering condition influence on the various types of corrosion behavior of 13% Cr martensitic stainless steel. Corrosion resistance was hardly changed by the tempering up to temperature of 500 .deg. C, but decreased at 600 .deg. C due to the formation of Cr carbide on the prior austenite boundary. However, the corrosion resistance increased again at 700 .deg. C, because Cr carbides were resolved and redistributed. Both general corrosion resistance and intergranular corrosion resistance of tempered steel are significantly improved with Mo content.

  16. Hot-Deformation Behavior and Hot-Processing Maps of AISI 410 Martensitic Stainless Steel

    Science.gov (United States)

    Qi, Rong-Sheng; Jin, Miao; Guo, Bao-Feng; Liu, Xin-Gang; Chen, Lei

    2016-10-01

    The compressive deformation behaviors of 410 martensitic stainless steel were investigated on a Gleeble-1500 thermomechanical simulator, and the experimental stress-strain data were obtained. The measured flow stress was corrected for friction and temperature. A constitutive equation that accounts for the influence of strain was established, and the hot-processing maps at different strain were plotted. The microstructure evolution of the hot-deformation process was studied on the basis of microstructural observations at high temperatures. Phase-transformation experiments on 410 steel were conducted at high temperatures to elucidate the effects of temperature on the delta-ferrite content. The initial forging temperature and optimum process parameters were obtained on the basis of the processing map and the changes in the delta-ferrite content at high temperatures.

  17. Mechanical and corrosion resistant properties of martensitic stainless steel plasma nitrocarburized with rare earths addition

    Institute of Scientific and Technical Information of China (English)

    LIU Ruiliang; QIAO Yingjie; YAN Mufu; FU Yudong

    2012-01-01

    In order to improve surface hardness and corrosion resistant property of 17-4PH martensitic stainless steel,the steel was plasma nitrocarburized at 560 ℃ for 2-24 h in a gas mixture of nitrogen,hydrogen and ethanol with rare earths (RE) addition.The experimental results showed that the modified layer was characterized by a compound layer containing two distinct zones (i.e.out ‘dark zone’ and inner ‘white zone’).The inner ‘white zone’ was almost a precipitation free zone and had high hardness as well as good corrosion resistance.Anodic polarization test results showed that the specimens plasma nitrocarburized with RE addition had good corrosion resistance resulted mainly from their higher corrosion potentials,lower corrosion current densities and larger passive regions as compared with those of the untreated one.

  18. Polarised SANS study of microstructural evolution under neutron irradiation in a martensitic steel for fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Coppola, R.; Dewhurst, C.D.; Lindau, R.; May, R.P.; Moeslang, A.; Valli, M

    2004-03-01

    This work presents the results of polarised small-angle neutron scattering (SANS) measurements of modified martensitic steel DIN1.4914, originally developed for application in future fusion reactors (MANET steel). SANS measurements were made using the D22 instrument at the ILL Grenoble using an ad hoc polarised beam set-up. The investigated MANET samples were neutron irradiated and subsequently post-irradiation tempered to reproduce as much as possible the expected service conditions. The results, based on the analysis of the nuclear-magnetic interference, are discussed taking into account both the occurrence of Cr redistribution phenomena with correlated changes in the composition of the precipitate phases, and the growth of non-magnetic defects (He-bubbles or microvoids)

  19. Modelling the creep behaviour of tempered martensitic steel based on a hybrid approach

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Surya Deo, E-mail: surya.yadav@tugraz.at [Institute of Materials Science and Welding, Graz University of Technology, Kopernikusgasse 24, A-8010 Graz (Austria); Sonderegger, Bernhard, E-mail: bernhard.sonderegger@tugraz.at [Institute of Materials Science and Welding, Graz University of Technology, Kopernikusgasse 24, A-8010 Graz (Austria); Stracey, Muhammad, E-mail: strmuh001@myuct.ac.za [Centre for Materials Engineering, Department of Mechanical Engineering, University of Cape Town, Cape Town (South Africa); Poletti, Cecilia, E-mail: cecilia.poletti@tugraz.at [Institute of Materials Science and Welding, Graz University of Technology, Kopernikusgasse 24, A-8010 Graz (Austria)

    2016-04-26

    In this work, we present a novel hybrid approach to describe and model the creep behaviour of tempered martensitic steels. The hybrid approach couples a physically based model with a continuum damage mechanics (CDM) model. The creep strain is modelled describing the motions of three categories of dislocations: mobile, dipole and boundary. The initial precipitate state is simulated using the thermodynamic software tool MatCalc. The particle radii and number densities are incorporated into the creep model in terms of Zener drag pressure. The Orowan's equation for creep strain rate is modified to account for tertiary creep using softening parameters related to precipitate coarsening and cavitation. For the first time the evolution of internal variables such as dislocation densities, glide velocities, effective stresses on dislocations, internal stress from the microstructure, subgrain size, pressure on subgrain boundaries and softening parameters is discussed in detail. The model is validated with experimental data of P92 steel reported in the literature.

  20. TRIP effect in austenitic-martensitic VNS9-Sh steel at various strain rates

    Science.gov (United States)

    Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.

    2016-10-01

    The mechanical properties of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) steel are studied at a static strain rate from 4.1 × 10-5 to 17 × 10-3 s-1 (0.05-20 mm/min). It is found that, as the strain rate increases, the ultimate tensile strength decreases and the physical yield strength remains unchanged (≈1400 MPa). As the strain rate increases, the yield plateau remains almost unchanged and the relative elongation decreases continuously. Because of high microplastic deformation, the conventional yield strength is lower than the physical yield strength over the entire strain rate range under study. The influence of the TRIP effect on the changes in the mechanical properties of VNS9-Sh steel at various strain rates is discussed.

  1. Mechanical Performance of Ferritic Martensitic Steels for High Dose Applications in Advanced Nuclear Reactors

    Science.gov (United States)

    Anderoglu, Osman; Byun, Thak Sang; Toloczko, Mychailo; Maloy, Stuart A.

    2013-01-01

    Ferritic/martensitic (F/M) steels are considered for core applications and pressure vessels in Generation IV reactors as well as first walls and blankets for fusion reactors. There are significant scientific data on testing and industrial experience in making this class of alloys worldwide. This experience makes F/M steels an attractive candidate. In this article, tensile behavior, fracture toughness and impact property, and creep behavior of the F/M steels under neutron irradiations to high doses with a focus on high Cr content (8 to 12) are reviewed. Tensile properties are very sensitive to irradiation temperature. Increase in yield and tensile strength (hardening) is accompanied with a loss of ductility and starts at very low doses under irradiation. The degradation of mechanical properties is most pronounced at reactor environment, the stress exponent is expected to be approximately one and the steady state creep rate in the absence of swelling is usually better than austenitic stainless steels both in terms of the creep rate and the temperature sensitivity of creep. In short, F/M steels show excellent promise for high dose applications in nuclear reactors.

  2. Fracture properties of neutron-irradiated martensitic 9Cr-WVTa steels below room temperature

    Science.gov (United States)

    Abe, F.; Narui, M.; Kayano, H.

    1994-09-01

    Fracture properties of the reduced activation martensitic 9Cr-1WVTa and 9Cr-3WVTa steels were investigated by carrying out instrumented Charpy impact tests and tensile tests at temperatures below room temperature after irradiation in the Japan Materials Testing Reactor at 493 and 538 K. Modified 9Cr-1MoVNb steel was also examined for comparison. The irradiation-induced increase in ductile-to-brittle transition temperature was 53, 26 and 40 K for the {1}/{3} size Charpy specimens of 9Cr-1WVTa, 9Cr-3WVTa and 9Cr-1MoVNb steels, respectively, which resulted primarily from the irradiation-induced increase in yield stress. The cleavage fracture stress was 1820-1870 MPa for the three steels in unirradiated conditions, which was scarcely affected by irradiation. The deflections to the maximum load and to the brittle fracture initiation were decreased by irradiation. In the tensile test, quasi-cleavage fracture occurred at 77 K in both unirradiated and irradiated conditions. The cleavage fracture stress was 1320-1380 MPa for the tensile specimens of the three steels, which was about 1.4 times smaller than that for the Charpy specimens.

  3. Studies on Nb Microalloying of 13Cr Super Martensitic Stainless Steel

    Science.gov (United States)

    Ma, Xiaoping; Wang, Lijun; Subramanian, Sundaresa V.; Liu, Chunming

    2012-12-01

    The effect of Nb microalloying on microstructure, mechanical properties, and pitting corrosion properties of quenched and tempered 13 pct Cr-5 pct Ni-0.02 pct C martensitic stainless steels with different Mo and N contents was investigated. The microstructure, density, and dispersion of high-angle boundaries, nanoscale precipitates, and amount of retained austenite were characterized by using electron backscattered diffraction, transmission electron microscopy, and X-ray diffraction to correlate with properties. The results show that the combined effects of lowering nitrogen content in 13 pct Cr-5 pct Ni-1~2 pct Mo-0.02 pct C steels to 0.01 wt pct, and adding 0.1 pct Nb are to decrease the amount of Cr-rich precipitates, as Nb preferentially combines with residual carbon and nitrogen to form carbonitrides, suppressing the formation of Cr2N and Cr23C6. Austenite grain refinement can be achieved by Nb microalloying through proper heat treatment. If the nitrogen content is kept high, then Cr-rich precipitates would occur irrespective of microalloying addition. The NbN would also occur at high temperature, which will act as substrate for nucleation of coarse precipitates during subsequent tempering, impairing the toughness of the steel. It was shown that the addition of Nb to low interstitial super martensitic stainless steel retards the formation of reversed austenite and results in the formation of nanoscale precipitates (5 to 15 nm), which contribute to a significant increase in strength. More importantly, the pitting corrosion resistance was found to increase with Nb addition. This is attributed to suppression of Cr-rich precipitates, which can cause local depletion of Cr in the matrix and the initiation of pitting corrosion.

  4. Effects of Pulsed Current and Pulsed Magnetic Field Complex Pretreatment on Martensite Transformation of Cr5 Steel during Continuous Cooling

    Institute of Scientific and Technical Information of China (English)

    Qing-chun LI; Li-juan LI; Guo-wei CHANG; Qi-jie ZHAI

    2015-01-01

    Carbide precipitation and martensite transformation in Cr5 steel have been observed in situ by high-temper-ature confocal laser-scanning microscopy.In this way,the influences of pulsed current and pulsed magnetic field complex pretreatment on carbide precipitation and martensite transformation during continuous cooling have been studied.The results show that the electropulsing complex pretreatment promotes the precipitation of M7 C3-type car-bides at high temperature,increases the start and finish temperatures of martensite transformation,and extends the phase transformation time.Martensite prefers to nucleate in the austenite with less precipitation of carbides due to the chemically homogeneous distribution of solute atoms.

  5. Role of Tungsten in the Tempered Martensite Embrittlement of a Modified 9 Pct Cr Steel

    Science.gov (United States)

    Fedoseeva, Alexandra; Dudova, Nadezhda; Kaibyshev, Rustam

    2017-01-01

    The effect of tempering on the mechanical properties and fracture behavior of two 3 pct Co-modified 9 pct Cr steels with 2 and 3 wt pct W was examined. Both steels were ductile in tension tests and tough under impact tests in high-temperature tempered conditions. At T ≤ 923 K (650 °C), the addition of 1 wt pct W led to low toughness and pronounced embrittlement. The 9Cr2W steel was tough after low-temperature tempering up to 723 K (450 °C). At 798 K (525 °C), the decomposition of retained austenite induced the formation of discontinuous and continuous films of M23C6 carbides along boundaries in the 9Cr2W and the 9Cr3W steels, respectively, which led to tempered martensite embrittlement (TME). In the 9Cr2W steel, the discontinuous boundary films played a role of crack initiation sites, and the absorption energy was 24 J cm-2. In the 9Cr3W steel, continuous films provided a fracture path along the boundaries of prior austenite grains (PAG) and interlath boundaries in addition that caused the drop of impact energy to 6 J cm-2. Tempering at 1023 K (750 °C) completely eliminated TME by spheroidization and the growth of M23C6 carbides, and both steels exhibited high values of adsorbed energy of ≥230 J cm-2. The addition of 1 wt pct W extended the temperature domain of TME up to 923 K (650 °C) through the formation of W segregations at boundaries that hindered the spheroidization of M23C6 carbides.

  6. Effect of Long-Term Service on Microstructure and Mechanical Properties of Martensitic 9% Cr Steel

    Science.gov (United States)

    Golański, Grzegorz; Zielińska-Lipiec, Anna; Zieliński, Adam; Sroka, Marek

    2017-02-01

    The paper presents the results of research on the X10CrMoVNbN9-1 (T91) steel after long-term service. The material for testing was taken from a pipe section of a boiler superheater coil serviced for around 105,000 h at the temperature of 540 °C, at the pressure of 12.5 MPa. A quantitative analysis including the measurement of mean diameter of subgrains and precipitates as well as the density of dislocations of the examined steel was performed by means of TEM. The microscopic tests of T91 steel were complemented with the results of tests on mechanical properties which included also the short creep tests. After service, the investigated steel was characterized by a retained lath microstructure of tempered martensite with fine subgrain and quite large density of dislocations as well as numerous precipitates. In the microstructure, apart from the particles of M23C6 and MX (VX, NbC, V-wings), the precipitates of Laves phase and single particles of Z phase were revealed. It has been shown that the extent of degradation of the T91 steel microstructure was minor, which resulted from its low temperature of service. Performed tests of mechanical properties showed that these properties fulfilled the minimum requirements for this steel in the as-received condition. A favorable influence of fine precipitates of Laves phase on mechanical properties was observed. Moreover, an insignificant influence of single precipitates of Z phase on the creep resistance of the examined steel was stated.

  7. Role of Tungsten in the Tempered Martensite Embrittlement of a Modified 9 Pct Cr Steel

    Science.gov (United States)

    Fedoseeva, Alexandra; Dudova, Nadezhda; Kaibyshev, Rustam

    2017-03-01

    The effect of tempering on the mechanical properties and fracture behavior of two 3 pct Co-modified 9 pct Cr steels with 2 and 3 wt pct W was examined. Both steels were ductile in tension tests and tough under impact tests in high-temperature tempered conditions. At T ≤ 923 K (650 °C), the addition of 1 wt pct W led to low toughness and pronounced embrittlement. The 9Cr2W steel was tough after low-temperature tempering up to 723 K (450 °C). At 798 K (525 °C), the decomposition of retained austenite induced the formation of discontinuous and continuous films of M23C6 carbides along boundaries in the 9Cr2W and the 9Cr3W steels, respectively, which led to tempered martensite embrittlement (TME). In the 9Cr2W steel, the discontinuous boundary films played a role of crack initiation sites, and the absorption energy was 24 J cm-2. In the 9Cr3W steel, continuous films provided a fracture path along the boundaries of prior austenite grains (PAG) and interlath boundaries in addition that caused the drop of impact energy to 6 J cm-2. Tempering at 1023 K (750 °C) completely eliminated TME by spheroidization and the growth of M23C6 carbides, and both steels exhibited high values of adsorbed energy of ≥230 J cm-2. The addition of 1 wt pct W extended the temperature domain of TME up to 923 K (650 °C) through the formation of W segregations at boundaries that hindered the spheroidization of M23C6 carbides.

  8. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    Science.gov (United States)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  9. Effect of Long-Term Service on Microstructure and Mechanical Properties of Martensitic 9% Cr Steel

    Science.gov (United States)

    Golański, Grzegorz; Zielińska-Lipiec, Anna; Zieliński, Adam; Sroka, Marek

    2017-03-01

    The paper presents the results of research on the X10CrMoVNbN9-1 (T91) steel after long-term service. The material for testing was taken from a pipe section of a boiler superheater coil serviced for around 105,000 h at the temperature of 540 °C, at the pressure of 12.5 MPa. A quantitative analysis including the measurement of mean diameter of subgrains and precipitates as well as the density of dislocations of the examined steel was performed by means of TEM. The microscopic tests of T91 steel were complemented with the results of tests on mechanical properties which included also the short creep tests. After service, the investigated steel was characterized by a retained lath microstructure of tempered martensite with fine subgrain and quite large density of dislocations as well as numerous precipitates. In the microstructure, apart from the particles of M23C6 and MX (VX, NbC, V-wings), the precipitates of Laves phase and single particles of Z phase were revealed. It has been shown that the extent of degradation of the T91 steel microstructure was minor, which resulted from its low temperature of service. Performed tests of mechanical properties showed that these properties fulfilled the minimum requirements for this steel in the as-received condition. A favorable influence of fine precipitates of Laves phase on mechanical properties was observed. Moreover, an insignificant influence of single precipitates of Z phase on the creep resistance of the examined steel was stated.

  10. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Sietsma, J. [Delft University of Technology, Faculty 3mE, Dept. MSE, 2628 CD Delft (Netherlands); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-01-15

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  11. Effect of copper on the formation of strain-induced martensite in two austenitic stainless steels AISI 304

    Energy Technology Data Exchange (ETDEWEB)

    Gilapa, Leonidas Cayo Mamani, E-mail: leonidas@ifsc.edu.br [Instituto Federal de Santa Catarina, Rua Pavão, 1337, Bairro Costa e Silva, Joinville, SC CEP 89220-200 (Brazil); Oliveira, Carlos Augusto Silva de, E-mail: carlos.a@ufsc.br [Universidade Federal de Santa Catarina, Campus Universitário Reitor João David Ferreira Lima, Trindade, Florianópolis, SC CEP 88040-970 (Brazil); Silva, Manoel Ribeiro da, E-mail: mrsilva@unifei.edu.br [Universidade Federal de Itajubá, Instituto de Ciências, Itajubá (Brazil)

    2015-01-12

    The transformation of strain-induced martensite in two metastable austenitic stainless steels, AISI 304, with the same basic composition and concentrations of Cu variables was characterized by transmission electron microscopy and magnetic measurements. The deformations to induce the formation of martensite were performed using the test of conformability with Nakajima tooling at room temperature. The results obtained for the various samples showed that the steel with lower content of Cu presented higher degree of magnetization. Also it was observed that the martensite magnetic α′ and paramagnetic ε are formed at the intersection of dislocation, in the grain boundary, inside and at the edge of twinned and the stacking faults in the austenite.

  12. Predicting Microstructure Development During HighTemperature Nitriding of Martensitic Stainless SteelsUsing Thermodynamic Modeling

    Directory of Open Access Journals (Sweden)

    Tschiptschin André Paulo

    2002-01-01

    Full Text Available Thermodynamic calculations of the Fe-Cr-N System in the region of the Gas Phase Equilibria have been compared with experimental results of maximum nitrogen absorption during nitriding of two Martensitic Stainless Steels (a 6 mm thick sheet of AISI 410S steel and green powder compacts of AISI 434L steel under N2 atmospheres. The calculations have been performed combining the Fe-Cr-N System description contained in the SGTE Solid Solution Database and the gas phase for the N System contained in the SGTE Substances Database. Results show a rather good agreement for total nitrogen absorption in the steel and nitrogen solubility in austenite in the range of temperatures between 1273 K and 1473 K and in the range of pressures between 0.1 and 0.36 MPa. Calculations show that an appropriate choice of heat treatment parameters can lead to optimal nitrogen absorption in the alloy. It was observed in the calculations that an increased pressure stabilizes CrN at expenses of Cr2N - type nitrides.

  13. Effect of Plasma Nitriding Process Conditions on Corrosion Resistance of 440B Martensitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Łępicka Magdalena

    2014-09-01

    Full Text Available Martensitic stainless steels are used in a large number of various industrial applications, e.g. molds for plastic injections and glass moldings, automotive components, cutting tools, surgical and dental instruments. The improvement of their tribological and corrosion properties is a problem of high interest especially in medical applications, where patient safety becomes a priority. The paper covers findings from plasma nitrided AISI 440B (PN-EN or DIN X90CrMoV18 stainless steel corrosion resistance studies. Conventionally heat treated and plasma nitrided in N2:H2 reaction gas mixture (50:50, 65:35 and 80:20, respectively in two different temperature ranges (380 or 450°C specimens groups were examined. Microscopic observations and electrochemical corrosion tests were performed using a variety of analytical techniques. As obtained findings show, plasma nitriding of AISI 440B stainless steel, regardless of the process temperature, results in reduction of corrosion current density. Nevertheless, applying thermo-chemical process which requires exceeding temperature of about 400°C is not recommended due to increased risk of steel sensitization to intergranular and stress corrosion. According to the results, material ion nitrided in 450°C underwent leaching corrosion processes, which led to significant disproportion in chemical composition of the corroded and corrosion-free areas. The authors suggest further research into corrosion process of plasma nitrided materials and its degradation products.

  14. Chromium redistribution in thermally aged and irradiated ferritic-martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Camus, E.; Wanderka, N.; Welzel, S.; Wollenberger, H. [Hahn-Meitner-Institut Berlin GmbH (Germany); Materna-Morris, E. [Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany)

    1998-07-15

    Ferritic-martensitic steels containing 8-12 at.% chromium are considered as structural materials for spallation sources and fusion reactors. Materials will be subjected to intense damage rates, e.g. 50-100 dpa per year at full power. Therefore, the behavior under irradiation of these steels must be investigated. Our earlier dual-beam irradiation results on the DIN 1.4914 steel showed a decomposition into chromium-enriched and chromium-depleted regions. The mean concentration of the chromium-depleted regions was found to be 5.19{+-}0.32 at.% after irradiation at 500 C to a fluence of 50 dpa, as measured by atom probe field-ion microscopy. The chromium distribution in the matrix of the DIN 1.4914 steel after thermal ageing at temperatures between 400 and 600 C has been investigated for times up to 17000 h. The carbides were characterized by means of transmission electron microscopy and extraction replicas. The concentrations of the constituents of the matrix were measured by means of atom probe. The mean chromium concentrations in the matrix are found to be 8.66{+-}0.32, 4.5{+-}0.3, and 7.2{+-}0.4 at.%, after ageing at 400, 500, and 600 C, respectively. The matrix contains virtually no carbon. The results are discussed in terms of phase decomposition and species segregation. (orig.) 15 refs.

  15. Precipitate phases in normalized and tempered ferritic/martensitic steel P92

    Science.gov (United States)

    Shen, Yinzhong; Liu, Huan; Shang, Zhongxia; Xu, Zhiqiang

    2015-10-01

    Ferritic/martensitic steel P92 is a promising candidate for cladding and duct applications in Sodium-Cooled Fast Reactor. The precipitate phases of the P92 steel normalized at 1323 K (1050 °C) for 30 min and tempered at 1038 K (765 °C) for 1 h have been investigated using transmission electron microscopes. Four types of phases consisting of M23C6, MX, M2X and sigma-FeCr were identified in the steel. MX phases consist of Nb-rich M(C,N) carbonitride, Nb-rich MC carbide, V-rich M(C,N) carbonitride, V-rich MC carbide, V-rich MN nitride, and complex MC carbides with Nb-rich MC core and V-rich MC wings. M2X phases consist of Cr-rich M2(C,N) carbonitride, Cr-rich M2C carbide and M2N nitride. Sigma-FeCr has a simple tetragonal lattice and a typical chemical formula of Fe0.45Cr0.45W0.1. M23C6 and MX are the dominant phases, while the sigma-FeCr has the lowest content. The formation of sigma-FeCr and M2X phases in the steel is also discussed.

  16. In-situ investigation of martensite formation in AISI 52100 bearing steel at sub-zero Celsius temperature

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Pantleon, Karen

    2013-01-01

    Martensite formation in AISI 52100 bearing steel at sub-zero Celsius temperature was investigated with Vibrating Sample Magnetometry. The investigation reports the stabilization of retained austenite in quenched samples during storage at room temperature and reveals the thermally activated nature...

  17. Thermal Aging Effect Analysis of 17-4PH Martensitic Stainless Steel Valves for Nuclear Power Plant

    Institute of Scientific and Technical Information of China (English)

    BAI; Bing; ZHANG; Chang-yi; TONG; Zhen-feng; YANG; Wen

    2015-01-01

    The valve stem used in the main steam system of nuclear power plant is usually martensitic stainless steel(such as 17.4ph16.4Mo etc.).When served in high temperature for a long time,the thermal aging embrittlement of valve stem will be significant,and even lead to the fracture.

  18. Tempering of martensitic steel for fasteners: Effects of micro-alloying on microstructure and mechanical property evolution

    NARCIS (Netherlands)

    Öhlund, C.E.I.C.

    2015-01-01

    The research presented in this thesis aims to deepen our understanding of the effect of micro-alloying on the microstructure and mechanical property evolution during tempering of martensitic steel for fasteners. The ongoing trend of engine down-sizing has led to the need for stronger and more

  19. Tempering of martensitic steel for fasteners: Effects of micro-alloying on microstructure and mechanical property evolution

    NARCIS (Netherlands)

    Öhlund, C.E.I.C.

    2015-01-01

    The research presented in this thesis aims to deepen our understanding of the effect of micro-alloying on the microstructure and mechanical property evolution during tempering of martensitic steel for fasteners. The ongoing trend of engine down-sizing has led to the need for stronger and more temper

  20. Effect of retained austenite on the dynamic tensile behavior of a novel quenching-partitioning-tempering martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Qingguo; Qin, Shengwei; Liu, Yu [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Zuo, Xunwei, E-mail: jeepling@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Nailu [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Huang, Wen [College of Civil Engineering, Shenzhen University, Shenzhen 518060 (China); Rong, Yonghua [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2016-04-26

    The dynamic tensile test with a strain rate of 500 s{sup −1} and the quasi-static tensile test with a strain rate of 5.6×10{sup −4} s{sup −1} were performed for a novel Fe-0.20C-1.49Mn-1.52Si-0.58Cr-0.05 Nb (wt%) quenching-partitioning-tempering (Q-P-T) martensitic steel with high amount of retained austenite, respectively. This low carbon steel was also treated by the traditional quenching and tempering (Q&T) process, and the same experimental tests were performed for the low carbon Q&T martensitic steel with little retained austenite to understand the effect of the retained austenite on the dynamic tensile behavior. The results indicate that compared with the quasi-static tensile test, the high strain rate in the dynamic tensile test raises the strength of the Q-P-T steel. However, the elongation slightly decreases. These results differ from the enhancement in both the strength and elongation of the Q&T steel in the dynamic tensile test. The increase in the strength of the Q-P-T steel in the dynamic tensile test is attributed to the strain rate hardening effect. The slight decrease in the elongation stems mainly from that the suppression of the dislocation absorption of the retained austenite (DARA) effect existing in the quasi-static tensile test, moreover, such a suppression is not effectively complemented by the adiabatic softening of the martensitic matrix in dynamic tensile test. The marked increase in the elongation of the Q&T steel in the dynamic tensile test is only attributed to the adiabatic softening of the martensite matrix because there is no DARA effect in the Q&T steel with little retrained austenite.

  1. Corrosion of ferritic-martensitic steels and nickel-based alloys in supercritical water

    Science.gov (United States)

    Ren, Xiaowei

    The corrosion behavior of ferritic/martensitic (F/M) steels and Ni-based alloys in supercritical water (SCW) has been studied due to their potential applications in future nuclear reactor systems, fossil fuel power plants and waste treatment processes. 9˜12% chromium ferritic/martensitic steels exhibit good radiation resistance and stress corrosion cracking resistance. Ni-based alloys with an austenitic face-centered cubic (FCC) structure are designed to retain good mechanical strength and corrosion/oxidation resistance at elevated temperatures. Corrosion tests were carried out at three temperatures, 360°C, 500°C and 600°C, with two dissolved oxygen contents, 25 ppb and 2 ppm for up to 3000 hours. Alloys modified by grain refinement and reactive element addition were also investigated to determine their ability to improve the corrosion resistance in SCW. A duplex oxide structure was observed in the F/M steels after exposure to 25 ppb oxygen SCW, including an outer oxide layer with columnar magnetite grains and an inner oxide layer constituted of a mixture of spinel and ferrite phases in an equiaxed grain structure. An additional outermost hematite layer formed in the SCW-exposed samples when the oxygen content was increased to 2 ppm. Weight gain in the F/M steels increased with exposure temperatures and times, and followed parabolic growth kinetics in most of the samples. In Ni-based alloys after exposure to SCW, general corrosion and pitting corrosion were observed, and intergranular corrosion was found when exposed at 600°C due to formation of a local healing layer. The general oxide structure on the Ni-based alloys was characterized as NiO/Spinel/(CrxFe 1-x)2O3/(Fe,Ni). No change in oxidation mechanism was observed in crossing the critical point despite the large change in water properties. Corrosion resistance of the F/M steels was significantly improved by plasma-based yttrium surface treatment because of restrained outward diffusion of iron by the

  2. Effects of Cold Rolling and Strain-Induced Martensite Formation in a SAF 2205 Duplex Stainless Steel

    Science.gov (United States)

    Breda, Marco; Brunelli, Katya; Grazzi, Francesco; Scherillo, Antonella; Calliari, Irene

    2015-02-01

    Duplex stainless steels (DSSs) are biphasic steels having a ferritic-austenitic microstructure that allows them to combine good mechanical and corrosion-resistance properties. However, these steels are sensitive to microstructural modifications, such as ferrite decomposition at high temperatures and the possibility of strain-induced martensite (SIM) formation from cold-worked austenite, which can significantly alter their interesting features. In the present work, the effects of cold rolling on the developed microstructural features in a cold-rolled SAF 2205 DSS and the onset of martensitic transformation are discussed. The material was deformed at room temperature from 3 to 85 pct thickness reduction, and several characterization techniques (scanning and transmission electron microscopy, X-ray diffraction, hardness measurements, and time-of-flight-neutron diffraction) were employed in order to fully describe the microstructural behavior of the steel. Despite the low stacking fault energy of DSS austenite, which contributed to SIM formation, the steel was found to be more stable than other stainless steel grades, such as AISI 304L. Rolling textures were similar to those pertaining to single-phase materials, but the presence of the biphasic (Duplex) microstructure imposed deformation constraints that affected the developed microstructural features, owing to phases interactions. Moreover, even if an intensification of the strain field in austenite was revealed, retarded SIM transformation kinetics and lower martensite amounts with respect to AISI 304L were observed.

  3. Plasticity-induced martensitic transformation around fatigue cracks in type SUS304 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Nakasone, Y. [Dept. of Mechanical Engineering, Faculty of Engineering, Tokyo Univ. of Science, Shinjuku-ku, Tokyo (Japan); Iwasaki, Y.; Shimizu, T.; Kasumi, S. [Tokyo Univ. of Science (Japan)

    2003-07-01

    The presented study investigates plasticity-induced martensitic transformation around fatigue cracks in Type SUS304 austenitic stainless steel. Volume fraction of {alpha}' martensite transformed in uniformly stretched SUS304 plates was measured and expressed as a function of the applied strain level. The distributions of {alpha}' phase fraction in the plastic wake regions produced around fatigue cracks were then measured by ferrite scope in fatigued SUS 304 plate specimens. The results were compared with the distributions of vertical magnetic flux density B{sub z} above the fatigue cracks in the specimens magnetized by a strong magnetic field higher than 0.4 T. It was revealed that the B{sub z} distributions reflected the {alpha}' phase fraction distributions in the wake regions: i.e., the distance between two outermost peaks of the B{sub z} distributions had good linear correlations with real fatigue crack length, and the maximum and the minimum values of B{sub z} also showed good linear relationships with the applied stress intensity factor range {delta}K. These results imply that not only crack length but also the applied {delta}K level or the applied stress range {delta}{sigma} level can be detected effectively in an electromagnetic non-destructive way. (orig.)

  4. Corrosion of High Chromium Ferritic/Martensitic Steels in High Temperature Water. a Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, P.; Lapena, J.; Blazquez, F. [Ciemat, Madrid (Spain)

    2000-07-01

    Available literature concerning corrosion of high-chromium ferritic/martensitic steels in high temperature water has been reviewed. The subjects considered are general corrosion, effect of irradiation on corrosion, stress corrosion cracking (SCC) and irradiation-assisted stress corrosion cracking (IASCC). In addition some investigations about radiation induced segregation (RIS) are shown in order to know the compositional changes at grain boundaries of these alloys and their influence on corrosion properties. The data on general corrosion indicate moderate corrosion rates in high temperature water up to 350 degree centigree. Considerably larger corrosion rates were observed under neutron irradiation. The works concerning to the behaviour of these alloys to stress corrosion cracking seem to conclude that in these materials is necessary to optimize the temper temperature and to carry out the post-weld heat treatments properly in order to avoid stress corrosion cracking. (Author) 40 refs.

  5. Investigation on the Enhanced Oxidation of Ferritic/Martensitic Steel P92 in Pure Steam

    Directory of Open Access Journals (Sweden)

    Juntao Yuan

    2014-04-01

    Full Text Available Oxidation of ferritic/martensitic steel P92 was investigated in pure oxygen and in pure steam at 600–800 °C by thermogravimetric analysis (TGA, optical microscopy (OM, scanning electron microscopy (SEM, and X-ray diffraction (XRD. The results showed that the oxidation of P92 was significantly enhanced and multilayer scale with an outer iron oxides layer formed in pure steam. At 700 °C, the gas switch markedly influenced the scaling kinetics and scale microstructure. It was supposed that the higher affinity of iron to steam would be attributed to the enhanced oxidation of P92 in pure steam, and the much easier transport of hydroxyl would account for the significant difference induced by gas switch.

  6. Hydrogen interaction with the low activation ferritic–martensitic steel EK-181 (Rusfer)

    Energy Technology Data Exchange (ETDEWEB)

    Golubeva, A.V., E-mail: anna-golubeva@yandex.ru [NRC “Kurchatov Institute”, Akademika Kurchatova pl. 1, 123098 Moscow (Russian Federation); Bobyr, N.P. [NRC “Kurchatov Institute”, Akademika Kurchatova pl. 1, 123098 Moscow (Russian Federation); Cherkez, D.I., E-mail: cherkez@list.ru [NRC “Kurchatov Institute”, Akademika Kurchatova pl. 1, 123098 Moscow (Russian Federation); Spitsyn, A.V. [NRC “Kurchatov Institute”, Akademika Kurchatova pl. 1, 123098 Moscow (Russian Federation); Mayer, M. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstraße 2, D-85748 Garching (Germany); Gasparyan, Yu.M.; Efimov, V.S. [National Research Nuclear University MEPHI, Kashirskoe Shosse 31, 115409 Moscow (Russian Federation); Chernov, V.M.; Leontieva-Smirnova, M.V. [JSC “A.A. Bochvar High-Technology Research Institute of Inorganic Materials”, Rogova str. 5a, 123098 Moscow (Russian Federation)

    2013-07-15

    Deuterium retention in and gas-driven permeation through the new ferritic–martensitic steel Rusfer EK-181 (Fe–12Cr–2W–V–Ta–B–C) developed in the Russian Federation is studied. The retention of deuterium was investigated in the temperature range of RT-773 K at pressures 10 and 10{sup 4} Pa. The amount of deuterium retained strongly increases with increasing temperature. The permeation of deuterium through tubes of EK-181 was investigated at gas loading in the pressure range of 5 × 10{sup −2}–100 Pa and in the temperature range of 573–923 K. In order to study the influence of surface impurities the front surfaces of the tube were cleaned by an argon plasma discharge, as a result the permeating flux was increased by a factor of 3.

  7. A study on Z-phase nucleation in martensitic chromium steels

    Energy Technology Data Exchange (ETDEWEB)

    Golpayegani, Ardeshir [Department of Applied Physics, Chalmers University of Technology (Sweden)], E-mail: ardeshir.golpayegani@sandvik.com; Andren, Hans-Olof [Department of Applied Physics, Chalmers University of Technology (Sweden); Danielsen, Hilmar; Hald, John [Department of Manufacturing Engineering and Management, Technical University of Denmark (Denmark)

    2008-08-20

    9-12% chromium martensitic steels are liable to the precipitation of Z-phase, Cr(V,Nb)N, after long time exposure at 550-650 deg. C. This complex nitride consumes vanadium nitrides and causes the creep strength of the material to fall drastically after several thousand hours of exposure. In this work, initial stages of precipitation of Z-phase have been studied and characterized using energy-filtered transmission electron microscopy (EFTEM). Vanadium nitrides were found to provide the most suitable nucleation site for Z-phase, since the misfit between the (0 0 1) planes of VN and Z-phase is very small. Furthermore, such a nucleation site would provide vanadium and nitrogen for the growth of Z-phase. The presence of niobium carbide has also been observed close to Z-phase nucleation sites, indicating niobium to be important for the nucleation and growth of Z-phase.

  8. Process improvement in laser hot wire cladding for martensitic stainless steel based on the Taguchi method

    Science.gov (United States)

    Huang, Zilin; Wang, Gang; Wei, Shaopeng; Li, Changhong; Rong, Yiming

    2016-09-01

    Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power ( P), scanning speed ( V s), wire feed rate ( V f), and wire current ( I), were optimized based on the analysis of signal-to-noise (S/N) ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.

  9. Microstructural evolution of reduced-activation martensitic steel under single and sequential ion irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Jin, Shuoxue; Li, Tiecheng; Zheng, Zhongcheng [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yang, Feng; Xiong, Xuesong; Suo, Jinping [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2013-07-15

    Microstructural evolution of super-clean reduced-activation martensitic steels irradiated with single-beam (Fe{sup +}) and sequential-beam (Fe{sup +} plus He{sup +}) at 350 °C and 550 °C was studied. Sequential-beam irradiation induced smaller size and larger number density of precipitates compared to single-beam irradiation at 350 °C. The largest size of cavities was observed after sequential-beam irradiation at 550 °C. The segregation of Cr and W and depletion of Fe in carbides were observed, and the maximum depletion of Fe and enrichment of Cr occurred under irradiation at 350 °C.

  10. Effect of Hydrogen and Strain-Induced Martensite on Mechanical Properties of AISI 304 Stainless Steel

    Directory of Open Access Journals (Sweden)

    Sang Hwan Bak

    2016-07-01

    Full Text Available Plastic deformation and strain-induced martensite (SIM, α′ transformation in metastable austenitic AISI 304 stainless steel were investigated through room temperature tensile tests at strain rates ranging from 2 × 10−6 to 2 × 10−2/s. The amount of SIM was measured on the fractured tensile specimens using a feritscope and magnetic force microscope. Elongation to fracture, tensile strength, hardness, and the amount of SIM increased with decreasing the strain rate. The strain-rate dependence of RT tensile properties was observed to be related to the amount of SIM. Specifically, SIM formed during tensile tests was beneficial in increasing the elongation to fracture, hardness, and tensile strength. Hydrogen suppressed the SIM formation, leading to hydrogen softening and localized brittle fracture.

  11. Fracture toughness master-curve analysis of the tempered martensitic steel Eurofer97

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Pablo [Fusion Technology-Materials, CRPP-EPFL, Association EURATOM-Confederation Suisse, ODGA-109, 5232 Villigen PSI (Switzerland)], E-mail: pablo.mueller@psi.ch; Spaetig, P.; Bonade, R. [Fusion Technology-Materials, CRPP-EPFL, Association EURATOM-Confederation Suisse, ODGA-109, 5232 Villigen PSI (Switzerland); Odette, G.R.; Gragg, D. [Materials and Mechanical Engineering Department, University of California, Santa Barbara, CA 93106-5070 (United States)

    2009-04-30

    We report fracture toughness data for the reduced activation tempered martensitic steel Eurofer97 in the lower to middle transition region. The fracture toughness was measured from tests carried out on 0.35T and 0.87T pre-cracked compact tension specimens. The data were first analyzed using the ASTM E1921 standard. The toughness-temperature behavior and scatter were shown to deviate from the ASTM E1921 standard predictions near the lower shelf. Using the method of maximum likelihood, the athermal component of the master-curve was calculated to better fit the data from the lower to the middle transition region. We showed that these master-curve adjustments are necessary to make the T{sub o} values obtained near the lower shelf with 0.35TC(T) specimens consistent with those obtained in the middle transition region with 0.87TC(T) specimens.

  12. Fracture toughness master-curve analysis of the tempered martensitic steel Eurofer97

    Science.gov (United States)

    Mueller, Pablo; Spätig, P.; Bonadé, R.; Odette, G. R.; Gragg, D.

    2009-04-01

    We report fracture toughness data for the reduced activation tempered martensitic steel Eurofer97 in the lower to middle transition region. The fracture toughness was measured from tests carried out on 0.35 T and 0.87 T pre-cracked compact tension specimens. The data were first analyzed using the ASTM E1921 standard. The toughness-temperature behavior and scatter were shown to deviate from the ASTM E1921 standard predictions near the lower shelf. Using the method of maximum likelihood, the athermal component of the master-curve was calculated to better fit the data from the lower to the middle transition region. We showed that these master-curve adjustments are necessary to make the To values obtained near the lower shelf with 0.35 TC( T) specimens consistent with those obtained in the middle transition region with 0.87 TC( T) specimens.

  13. Formation of alumina-aluminide coatings on ferritic-martensitic T91 steel

    Directory of Open Access Journals (Sweden)

    Choudhary R.K.

    2014-01-01

    Full Text Available In this work, alumina-aluminide coatings were formed on ferritic-martensitic T91 steel substrate. First, coatings of aluminum were deposited electrochemically on T91 steel in a room temperature AlCl3-1-ethyl-3-methyl imidazolium chloride ionic liquid, then the obtained coating was subjected to a two stage heat treatment procedure consisting of prolonged heat treatment of the sample in vacuum at 300 ○C followed by oxidative heat treatment in air at 650 ○C for 16 hours. X-ray diffraction measurement of the oxidatively heat treated samples indicated formation of Fe-Al and Cr-Al intermetallics and presence of amorphous alumina. Energy dispersive X-ray spectroscopy measurement confirmed 50 wt- % O in the oxidized coating. Microscratch adhesion test conducted on alumina-aluminide coating formed on T91 steel substrate showed no major adhesive detachment up to 20 N loads. However, adhesive failure was observed at a few discrete points on the coating along the scratch track.

  14. Formation of epsilon martensite by high-pressure torsion in a TRIP steel

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, Roberto B., E-mail: figueiredo-rb@ufmg.br [Department of Materials Engineering and Civil Construction, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Sicupira, Felipe L.; Malheiros, Livia Raquel C. [Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Kawasaki, Megumi [Division of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Santos, Dagoberto B. [Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Langdon, Terence G. [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States)

    2015-02-11

    An Fe–17% Mn–0.06% C–2% Si–3% Al–1% Ni steel exhibiting a phase transformation induced by room temperature deformation was processed by high-pressure torsion (HPT) using a pressure of 6.0 GPa and with the samples subjected to different amounts of torsional straining up to a maximum of 10 turns. A microstructural analysis revealed a phase transformation in the early stages of deformation and a gradual evolution towards a fully-deformed structure. Microhardness measurements showed two stages of hardening with eventual softening at large strains. From X-ray diffraction (XRD) analysis, there is evidence for a reverse martensitic transformation and the stabilization of an h.c.p. epsilon (ε) structure. The formation of an h.c.p. structure takes place in this steel at lower pressures than for pure iron but the results agree with earlier reports of the presence of an ε phase in stainless steel processed by HPT and with the expected reduction in the transition pressure due to the Mn addition.

  15. Microstructure control for high strength 9Cr ferritic-martensitic steels

    Science.gov (United States)

    Tan, L.; Hoelzer, D. T.; Busby, J. T.; Sokolov, M. A.; Klueh, R. L.

    2012-03-01

    Ferritic-martensitic (F-M) steels with 9 wt.%Cr are important structural materials for use in advanced nuclear reactors. Alloying composition adjustment, guided by computational thermodynamics, and thermomechanical treatment (TMT) were employed to develop high strength 9Cr F-M steels. Samples of four heats with controlled compositions were subjected to normalization and tempering (N&T) and TMT, respectively. Their mechanical properties were assessed by Vickers hardness and tensile testing. Ta-alloying showed significant strengthening effect. The TMT samples showed strength superior to the N&T samples with similar ductility. All the samples showed greater strength than NF616, which was either comparable to or greater than the literature data of the PM2000 oxide-dispersion-strengthened (ODS) steel at temperatures up to 650 °C without noticeable reduction in ductility. A variety of microstructural analyses together with computational thermodynamics provided rational interpretations on the strength enhancement. Creep tests are being initiated because the increased yield strength of the TMT samples is not able to deduce their long-term creep behavior.

  16. Development of new generation reduced activation ferritic-martensitic steels for advanced fusion reactors

    Science.gov (United States)

    Tan, L.; Snead, L. L.; Katoh, Y.

    2016-09-01

    International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M23C6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ∼500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods. Preliminary experimental results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. The strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9-20Cr oxide dispersion-strengthened ferritic alloys.

  17. Fracture toughness master curve analysis of the tempered martensitic steel Eurofer97

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, P.; Spatig, P.; Bonade, R. [EPFL-CBPP, Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH Villigen PSI (Switzerland); Odette, G. [UCSB, Santa-Barbara, Dept. of Mechanical Engineering UCSB, AK (United States)

    2007-07-01

    Full text of publication follows: The reduced activation tempered martensitic steel Eurofer97 is the European reference reduced activation steel for fusion applications. In this study, the fracture toughness properties of this steel are investigated in the ductile-to-brittle fracture transition region. The ASTM E-1921 master curve (equation 1 with {alpha} 0.019) describes well the temperature dependence of the median toughness of a variety of nuclear reactor pressure vessel steels. K{sub Jc(median)} = 30 + 70 exp[{alpha}(T - T{sub 0})] (1). We previously showed that fracture toughness data obtained with 0.35 T compact tension specimens are not satisfactorily described by the ASTM E1921 master curve in the lower transition region, corresponding to the temperature range [-150, -100 deg. C]. A better statistical description of the data was done, using a modified master curve shape with a coefficient {alpha} equal to 0.04 and a T{sub 0} value of -97 deg. C. In order to confirm the different shape of the fracture toughness curve of the Eurofer97, new fracture toughness tests were carried out at higher temperatures, up to -50 deg. C. These new data indicate that the K{sub Jc(median)}(T) curve in the transition is indeed steeper than the ASTM E1921 master curve. The validation of the modified master curve is discussed in terms of: i) the statistical predictions of scatter with temperature in comparison to the experimental data and ii) a self-consistent determination of T{sub 0} by performing series of single temperature T{sub 0}-analysis as well as multi-temperature T{sub 0}-analysis. A very good agreement between the predictions and experimental observations is found. Finally, the underlying possible physical reasons responsible for this specific fracture behavior of the Eurofer97 steel in the transition are briefly discussed in relation to its microstructure. (authors)

  18. Effect of the strain rate on the mechanical properties of a sheet TRIP steel with a high martensite content

    Science.gov (United States)

    Eliseev, E. A.; Terent'ev, V. F.; Voznesenskaya, N. M.; Slizov, A. K.; Sirotinkin, V. P.; Baikin, A. S.; Seval'nev, G. S.

    2017-04-01

    The laws of changing the mechanical properties of sheet austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) TRIP steel are studied when the static strain rate changes in the range 0.1-20 mm/min (8.3 × 10-5-17 × 10-3 s-1). The 0.35-mm strip under study is characterized by a high martensite content (≈100%) in the surface layer at an average content of 80-85%. The transformation induced plasticity effect is maximal at a strain rate of 0.1 mm/min (8.3 × 10-5 s-1).

  19. Relationship among wear-resistance of three-body abrasion,substructure and property in martensite steels

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of subsurface hardness on wear-resistance of martensitic steel 20Cr, 40CrSi, 60Mn, T8 and T10 in three-body abrasion under static load was investigated. It shows that the characteristic ofthe subsurface hardness distribution and the abrasive wear resistanceis related to the substructure near the worn surface. The substructure of the tested martensite steel has an apparent relationship with thecarbon content and steels with moderate carbon content and hardness exhibit good resistance to abrasive wear. The competition of the work-hardening effect and the temper softening effect, which resulted from deformation and friction heat generating during abrasive wear is considered to be a main reason for the relation among wear-resistance, hardness and substructure. At the test conditions, the wear-resistance of 40CrSi is the best.

  20. Real-time structural analysis of quenching and partitioning (Q and P) in an experimental martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Bigg, Timothy D., E-mail: t.d.bigg@leeds.ac.uk; Edmonds, David V., E-mail: d.v.edmonds@leeds.ac.uk; Eardley, Edwin S., E-mail: e_s_eardley@hotmail.com

    2013-11-15

    Highlights: •We present an innovative method of studying the Q and P heat treatment process. •A specially engineered steel was used to study carbon partitioning in real-time. •Measurements were obtained using a neutron diffractometer with an in situ furnace. •Real-time evidence of partitioning was observed in the form of lattice dilatation. •Carbon ‘trapping’ is hypothesised to reduce the carbon available for partitioning. -- Abstract: Quenching and Partitioning (Q and P) is a new concept in martensitic steel heat treatment which, as well as other opportunities, offers potential for expansion of the elongation versus strength envelope available to steel users, especially the automotive industry. The Q and P steel concept shares similarities with TRIP steel in that both promote multiphase microstructures of stabilised retained austenite and a harder phase of bainite (TRIP) or martensite (Q and P), although in Q and P the two stages of martensite formation and austenite stabilisation by carbon partitioning are separated. The procedure also provides for both protection and temper strengthening of the martensite fraction. However, confirmatory study of reaction mechanisms has been frustrated by the elevated temperatures required to date to apply Q and P heat treatment to commercial steel compositions. Consequently, a model alloy has been used to separate the various stages of the Q and P heat treatment process, thus allowing diffraction experiments, particularly real-time in situ neutron diffractometry, to measure lattice parameter, lattice strain and phase fraction in order to deduce the concentration and distribution of carbon at different stages during the Q and P treatment.

  1. Thermally activated formation of martensite in Fe-C alloys and Fe-17%Cr-C stainless steels during heating from boiling nitrogen temperature

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Somers, Marcel A. J.

    2016-01-01

    The thermally activated austenite-to-martensite transformation was investigated by magnetometry in three Fe-C alloys and in two 17%Cr stainless steels. After quenching to room temperature, samples were immersed in boiling nitrogen and martensite formation was followed during subsequent (re...

  2. Effect of Prior Athermal Martensite on the Isothermal Transformation Kinetics Below M s in a Low-C High-Si Steel

    NARCIS (Netherlands)

    Navarro-Lopez, A.; Sietsma, J.; Santofimia, M.J.

    2015-01-01

    Thermomechanical processing of Advanced Multiphase High Strength Steels often includes isothermal treatments around the martensite start temperature (M s). It has been reported that the presence of martensite formed prior to these isothermal treatments accelerates the kinetics of the subsequent tran

  3. TIG and HIP joining of Reduced Activation Ferrite/Martensitic steel for the Korean ITER-TBM

    Energy Technology Data Exchange (ETDEWEB)

    Ku, Duck Young [ITER Korea, National Fusion Research Institute, Gwahangno 113, Yuseong-gu, Daejeon 305-333 (Korea, Republic of); Oh, Seungjin, E-mail: osj0423@gmail.com [Nuclear Engineering and Technology Institute, KHNP, 508 Keumbyeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Ahn, Mu-Young; Yu, In-Keun; Kim, Duck-Hoi; Cho, Seungyon [ITER Korea, National Fusion Research Institute, Gwahangno 113, Yuseong-gu, Daejeon 305-333 (Korea, Republic of); Choi, Im-Sub; Kwon, Ki-Bum [Soles Co. LTD., 9-1 Horim-dong, Dalseo-gu, Daegu 704-249 (Korea, Republic of)

    2011-10-01

    Korea is developing a Helium Cooled Solid Breeder Test Blanket Module for ITER. The primary candidate structural material is a Reduced Activation Ferritic/Martensitic steel. The complex TBM structure requires developing joining technologies for successful fabrication. The characteristics of Tungsten Inert Gas welding and Hot Isostatic Pressing joining of RAFM steel were investigated. Metallurgical examinations showed that the steel grain size was increased after HIP joining and recovered by post joining heat treatment. Both TIG welding and HIP joining are found to be acceptable for ITER TBM based on mechanical tests and microstructure examination.

  4. Isothermal martensitic transformation in a 12Cr-9Ni-4Mo-2Cu stainless steel in applied magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    San Martin, D. [Fundamentals of Advanced Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)], E-mail: d.sanmartin@tudelft.nl; Aarts, K.W.P.; Rivera-Diaz-del-Castillo, P.E.J. [Fundamentals of Advanced Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands); Dijk, N.H. van [Fundamental Aspects of Materials and Energy group, Faculty of Applied Sciences, TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands); Brueck, E. [Van der Waals-Zeeman Institute, University of Amsterdam, Valcknierstraat 65, 1018 XE Amsterdam (Netherlands); Zwaag, S. van der [Fundamentals of Advanced Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)

    2008-05-15

    This work concerns an in situ study of the isothermal formation of martensite in a stainless steel under the influence of magnetic fields up to 9 T at three different temperatures (213, 233 and 253 K). It is shown that the presence of a constant applied magnetic field promotes the formation of martensite significantly. The activation energy for the nucleation of martensite has been derived using a semi-empirical kinetic model. The experimental results have been analyzed using the Ghosh and Olson model. While this model describes the time and field dependences of the experimental data well, the thermal frictional energy and the defect size values are much lower than those expected from earlier work.

  5. Ductility enhancement in ultrafine-grained Fe-Ni-Mn martensitic steel by stress-induced reverse transformation

    Energy Technology Data Exchange (ETDEWEB)

    Ghasemi-Nanesa, H. [School of Metallurgy and Materials Engineering, University of Tehran, P.O. Box 14395-731, Tehran (Iran, Islamic Republic of); Nili-Ahmadabadi, M., E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, University of Tehran, P.O. Box 14395-731, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Shirazi, H. [School of Metallurgy and Materials Engineering, University of Tehran, P.O. Box 14395-731, Tehran (Iran, Islamic Republic of); Hossein Nedjad, S. [Faculty of Materials Engineering, Sahand University of Technology, P.O. Box 51335-1996, Tabriz (Iran, Islamic Republic of); Pishbin, S.H. [School of Metallurgy and Materials Engineering, University of Tehran, P.O. Box 14395-731, Tehran (Iran, Islamic Republic of)

    2010-11-15

    Research highlights: Fe-10Ni-7Mn age-hardenable martensitic steel in the strain-free, aged condition shows premature fracture and zero ductility. By Large strain deformation, nano-grained wire could be fabricated. Ultrahigh straining improved the ultimate tensile stress up to 2540 MPa and strain up to 7%. X-ray and TEM observations determined reverse transformation of martensite to austenite to epsilon martensite in nanostructured Fe-Ni-Mn steel. As a result and as shown by X-ray diffraction and SFE calculation, deformation of austenite could lead to {epsilon}-martensite formation by stacking fault mechanism in nano-grains. These transformations could be the reasons for further mechanical properties improvement. - Abstract: The effect of large strain deformation on the mechanical properties was investigated in a martensitic Fe-Ni-Mn alloy. After a combined deformation route (cold rolling plus wire drawing), the mechanical properties improved. The tensile strength of alloy in this study reaches to 2540 MPa and total tensile strain to 7% which are much higher than our previous study which after cold rolling and aging tensile strength was 1840 MPa with total tensile strain of 2.8%, although in both cases the improvement are significant for this brittle alloy. The enhancement of ductility after aging might be attributed to the effective role of grain refining down to nanoscale and the formation of austenite during deformation process and stabilization of that austenite in the aged wire. The austenite transforms to {epsilon}-martensite during tensile testing because of its low stacking fault energy (SFE) and increases the total measured tensile strain more. X-ray diffraction (XRD) analyses and transmission electron microscopic (TEM) images clarified the suggested reason for this ductility enhancement.

  6. The influence of martensite shape, concentration, and phase transformation strain on the deformation behavior of stable dual-phase steels

    Science.gov (United States)

    Bhattacharyya, A.; Sakaki, T.; Weng, G. J.

    1993-02-01

    A continuum model is developed to examine the influence of martensite shape, volume fraction, phase transformation strain, and thermal mismatch on the initial plastic state of the ferrite matrix following phase transformation and on the subsequent stress-strain behavior of the dual-phase steels upon loading. The theory is developed based on a relaxed constraint in the ductile matrix and an energy criterion to define its effective stress. In addition, it also assumes the martensite islands to possess a spheroidal shape and to be randomly oriented and homogenously dispersed in the ferrite matrix. It is found that for a typical water-quenched process from an intercritical temperature of 760 °C, the critical martensite volume fraction needed to induce plastic deformation in the ferrite matrix is very low, typically below 1 pct, regardless of the martensite shape. Thus, when the two-phase system is subjected to an external load, plastic deformation commences immediately, resulting in the widely observed “continuous yielding” behavior in dual-phase steels. The subsequent deformation of the dual-phase system is shown to be rather sensitive to the martensite shape, with the disc-shaped morphology giving rise to a superior overall response (over the spherical type). The stress-strain relations are also dependent upon the magnitude of the prior phase transformation strain. The strength coefficient h and the work-hardening exponent n of the smooth, parabolic-type stress-strain curves of the dual-phase system also increase with increasing martensite content for each selected inclusion shape. Comparison with an exact solution and with one set of experimental data indicates that the theory is generally within a reasonable range of accuracy.

  7. Development of next generation tempered and ODS reduced activation ferritic/martensitic steels for fusion energy applications

    Science.gov (United States)

    Zinkle, S. J.; Boutard, J. L.; Hoelzer, D. T.; Kimura, A.; Lindau, R.; Odette, G. R.; Rieth, M.; Tan, L.; Tanigawa, H.

    2017-09-01

    Reduced activation ferritic/martensitic steels are currently the most technologically mature option for the structural material of proposed fusion energy reactors. Advanced next-generation higher performance steels offer the opportunity for improvements in fusion reactor operational lifetime and reliability, superior neutron radiation damage resistance, higher thermodynamic efficiency, and reduced construction costs. The two main strategies for developing improved steels for fusion energy applications are based on (1) an evolutionary pathway using computational thermodynamics modelling and modified thermomechanical treatments (TMT) to produce higher performance reduced activation ferritic/martensitic (RAFM) steels and (2) a higher risk, potentially higher payoff approach based on powder metallurgy techniques to produce very high strength oxide dispersion strengthened (ODS) steels capable of operation to very high temperatures and with potentially very high resistance to fusion neutron-induced property degradation. The current development status of these next-generation high performance steels is summarized, and research and development challenges for the successful development of these materials are outlined. Material properties including temperature-dependent uniaxial yield strengths, tensile elongations, high-temperature thermal creep, Charpy impact ductile to brittle transient temperature (DBTT) and fracture toughness behaviour, and neutron irradiation-induced low-temperature hardening and embrittlement and intermediate-temperature volumetric void swelling (including effects associated with fusion-relevant helium and hydrogen generation) are described for research heats of the new steels.

  8. Effects of Heat Treatment and Nitrogen on Microstructure and Mechanical Properties of 1Cr12NiMo Martensitic Stainless Steel

    National Research Council Canada - National Science Library

    Ruicheng Fan Ming Gao Yingche Ma Xiangdong Zha Xianchao Hao Kui Liu

    2012-01-01

    A series of heat treatments using the orthogonal experiment method were performed to study the microstruc- ture and mechanical properties of 1Cr12NiMo martensitic stainless steel containing various...

  9. Orientation dependence of the martensite transformation in a quenched and partitioned steel subjected to uniaxial tension

    NARCIS (Netherlands)

    De Knijf, D.; Nguyen-Minh, T.; Petrov, R.H.; Kestens, L.A.I.; Jonas, J.J.

    2014-01-01

    The orientation dependence of the austenite-to-martensite transformation during uniaxial tensile testing was modelled using the phenomenological theory of martensite crystallography and the mechanical driving force. It was validated experimentally by means of electron backscatter diffraction measure

  10. High-temperature mechanical properties improvement on modified 9Cr-1Mo martensitic steel through thermomechanical treatments

    Science.gov (United States)

    Hollner, S.; Fournier, B.; Le Pendu, J.; Cozzika, T.; Tournié, I.; Brachet, J.-C.; Pineau, A.

    2010-10-01

    In the framework of the development of generation IV nuclear reactors and fusion nuclear reactors, materials with an improved high temperature (≅650 °C) mechanical strength are required for specific components. The 9-12%Cr martensitic steels are candidate for these applications. Thermomechanical treatments including normalisation at elevated temperature (1150 °C), followed by warm-rolling in metastable austenitic phase and tempering, have been applied on the commercial Grade 91 martensitic steel in order to refine its microstructure and to improve its precipitation state. The temperature of the warm-rolling was set at 600 °C, and those of the tempering heat-treatment at 650 °C and 700 °C thanks to MatCalc software calculations. Microstructural observations proved that the warm-rolling and the following tempering heat-treatment lead to a finer martensitic microstructure pinned with numerous small carbide and nitride particles. The hardness values of thermomechanically treated Grade 91 steel are higher than those of the as-received Grade 91. It is also shown that the yield stress and the ductility of the thermomechanically treated Grade 91 steel are significantly improved compared to the as-received material. Preliminary creep results showed that these thermomechanical treatments improve the creep lifetime by at least a factor 14.

  11. IMPROVEMENT OF MECHANICAL PROPERTIES OF MARTENSITIC STAINLESS STEEL BY PLASMA NITRIDING AT LOW TEMPERATURE

    Institute of Scientific and Technical Information of China (English)

    Y.T. Xi; D.X. Liu; D. Han; Z.F. Han

    2008-01-01

    A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding ezperiments were carried out for 15 h at 350℃ by means of DC-pulsed plasma in 25%N2+ 75%H2 atmosphere. The microstructure, phase composition, and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied surfaces were also studied. The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basks of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle erosion tester. The results show that the 350℃ nitrided surface is dominated by ε-Fe3N and αN, which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, the fatigue limit of AISI 420 steel can also be improved by plasma nitriding at 350℃ because plasma nitriding produces residual compressive stress inside the modified layer.

  12. Delta ferrite in the weld metal of reduced activation ferritic martensitic steel

    Science.gov (United States)

    Sam, Shiju; Das, C. R.; Ramasubbu, V.; Albert, S. K.; Bhaduri, A. K.; Jayakumar, T.; Rajendra Kumar, E.

    2014-12-01

    Formation of delta(δ)-ferrite in the weld metal, during autogenous bead-on-plate welding of Reduced Activation Ferritic Martensitic (RAFM) steel using Gas Tungsten Arc Welding (GTAW) process, has been studied. Composition of the alloy is such that delta-ferrite is not expected in the alloy; but examination of the weld metal revealed presence of delta-ferrite in the weld metal. Volume fraction of delta-ferrite is found to be higher in the weld interface than in the rest of the fusion zone. Decrease in the volume fraction of delta-ferrite, with an increase in preheat temperature or with an increase in heat input, is observed. Results indicate that the cooling rate experienced during welding affects the volume fraction of delta-ferrite retained in the weld metal and variation in the delta-ferrite content with cooling rate is explained with variation in the time that the weld metal spends in various temperature regimes in which delta-ferrite is stable for the alloy during its cooling from the liquid metal to the ambient temperature. This manuscript will discuss the effect of welding parameters on formation of delta-ferrite and its retention in the weld metal of RAFM steel.

  13. Mechanism of intergranular stress corrosion cracking in HAZ for super-martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Miyata, Yukio; Kimura, Mitsuo [Tubular Products and Casting Research Dept., JFE Steel Corporation, 1-1, Kawasaki-cho, Handa (Japan); Nakamichi, Haruo; Sato, Kaoru [Analysis and Characterization Research Dept., JFE Steel Corporation, 1-1, Minamiwatarida-cho, Kawasaki-ku, Kawasaki (Japan); Itakura, Noritsugu [Products Service and Development Dept., Chita Works, JFE Steel Corporation. 1-1, Kawasaki-cho, Handa (Japan); Masamura, Katsumi [Tubular Products Business Planning Dept., JFE Steel Corporation, 2-2-3, Uchisaiwai-sho, Chiyoda-ku, Tokyo (Japan)

    2004-07-01

    Mechanism of intergranular stress corrosion cracking (IGSCC) for heat affected zone (HAZ) of super-martensitic stainless steel was studied using two types of the steel. One was a lean grade, which was Mo free and low Ni, and the other was a high grade, which was Mo added and high Ni. Specimens received heat treatments simulating welding thermal cycles were applied to SCC tests. Cracks were observed in some specimens after U-bend SCC test under low pH environments. Thermal cycle conditions with sensitization were verified from the results. No crack was observed in the specimen with the thermal cycle simulating post welding heat treatment (PWHT) after sensitizing conditions. Therefore, PWHT was clarified to be effective to prevent the cracking. Cr carbides were observed along prior austenite grain boundary intermittently, and Cr depleted zone was confirmed on the grain boundary adjacent to carbides that precipitated on the grain boundary. It is, therefore, concluded that the cracking results from Cr depletion on prior austenite grain boundary accompanied by precipitation of Cr carbides under specific welding conditions. (authors)

  14. Dependence of Microelastic-plastic Nonlinearity of Martensitic Stainless Steel on Fatigue Damage Accumulation

    Science.gov (United States)

    Cantrell, John H.

    2006-01-01

    Self-organized substructural arrangements of dislocations formed in wavy slip metals during cyclic stress-induced fatigue produce substantial changes in the material microelastic-plastic nonlinearity, a quantitative measure of which is the nonlinearity parameter Beta extracted from acoustic harmonic generation measurements. The contributions to Beta from the substructural evolution of dislocations and crack growth for fatigued martensitic 410Cb stainless steel are calculated from the Cantrell model as a function of percent full fatigue life to fracture. A wave interaction factor f(sub WI) is introduced into the model to account experimentally for the relative volume of material fatigue damage included in the volume of material swept out by an interrogating acoustic wave. For cyclic stress-controlled loading at 551 MPa and f(sub WI) = 0.013 the model predicts a monotonic increase in Beta from dislocation substructures of almost 100 percent from the virgin state to roughly 95 percent full life. Negligible contributions from cracks are predicted in this range of fatigue life. However, over the last five percent of fatigue life the model predicts a rapid monotonic increase of Beta by several thousand percent that is dominated by crack growth. The theoretical predictions are in good agreement with experimental measurements of 410Cb stainless steel samples fatigued in uniaxial, stress-controlled cyclic loading at 551 MPa from zero to full tensile load with a measured f(sub WI) of 0.013.

  15. Hot Deformation Behavior of 1Cr12Ni3Mo2VN Martensitic Stainless Steel

    Science.gov (United States)

    He, Xiaomao; Jiang, Peng; Zhou, Leyu; Chen, Chao; Deng, Xiaochun

    2017-08-01

    1Cr12Ni3Mo2VN is a new type of martensitic stainless steel for the last-stage blades of large-capacity nuclear and thermal power turbines. The deformation behavior of this steel was studied by thermal compression experiments that performed on a Gleeble-3500 thermal simulator at a temperature range of 850°C to 1200°C and a strain rate of 0.01s-1 to 20s-1. When the deformation was performed at high temperature and low strain rate, a necklace type of microstructures was observed, the plastic deformation mechanism is grain boundary slip and migration, when at low temperature and lower strain rate, the slip bands were observed, the mechanism is intracrystalline slips, and when at strain rate of 20s-1, twins were observed, the mechanism are slips and twins. The Arrhenius equation was applied to describe the constitutive equation of the flow stress. The accuracy of the equation was verified by using the experimental data and the correlation coefficient R2 = 0.9786, and the equation can provide reasonable data for the design and numerical simulation of the forging process.

  16. Phase transformation and long-term service of high-temperature martensitic chromium steels

    Science.gov (United States)

    Kalashnikov, I. S.; Tarasenko, L.; Acselrad, O.; Pereira, L. C.; Shalkevich, A.; Soboleva, G.

    2001-02-01

    Martensitic high Cr (10 - 16%) steels alloyed with Ni (Co), Mo, W, V, and N are widely used in constructions subjected to cyclic loads at temperatures up to 600 degrees Celsius, in general after quenching from 1100 - 1150 degrees Celsius followed by tempering at 650 - 690 degrees Celsius. Due to long term service exposure at high temperatures, different microstructural changes take place, such as second-phases precipitation, formation of low-angle grain boundaries, as well as internal damage caused by cyclic loads and creep. Specific phase diagrams are presented that can be used to define time periods for reliable operation of parts with given composition, based on the time required for the appearance of second phase particles known to be detrimental to mechanical strength and performance. Restoring thermal treatments to be applied after long time exposure at service conditions, aiming at increasing service life, are also presented and discussed. The combined use of the diagrams and the restoring treatment ensures prediction of a reliable service-life period for components made of these steels.

  17. Effect of thermal aging on microstructure and mechanical properties of China low-activation martensitic steel at 550 degrees C

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; Liu, Shao Jun; Xu, Gang; Zhang, Baoren; Huang, Qun Ying [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei (China)

    2016-04-15

    The thermal aging effects on mechanical properties and microstructures in China low-activation martensitic steel have been tested by aging at 550 degrees C for 2,000 hours, 4,000 hours, and 10,000 hours. The microstructure was analyzed by scanning and transmission electron microscopy. The results showed that the grain size and martensitic lath increased by about 4 μm and 0.3 μm, respectively, after thermal exposure at 550 degrees C for 10,000 hours. MX type particles such as TaC precipitated on the matrix and Laves-phase was found on the martensitic lath boundary and grain boundary on aged specimens. The mechanical properties were investigated with tensile and Charpy impact tests. Tensile properties were not seriously affected by aging. Neither yield strength nor ultimate tensile strength changed significantly. However, the ductile-brittle transition temperature of China low-activation martensitic steel increased by 46 degrees C after aging for 10,000 hours due to precipitation and grain coarsening.

  18. The role of martensitic transformation on bimodal grain structure in ultrafine grained AISI 304L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Sabooni, S., E-mail: s.sabooni@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Karimzadeh, F.; Enayati, M.H. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Ngan, A.H.W. [Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2015-06-11

    In the present study, metastable AISI 304L austenitic stainless steel samples were subjected to different cold rolling reductions from 70% to 93%, followed by annealing at 700 °C for 300 min to form ultrafine grained (UFG) austenite with different grain structures. Transmission electron microscopy (TEM) and nanoindentation were used to characterize the martensitic transformation, in order to relate it to the bimodal distribution of the austenite grain size after subsequent annealing. The results showed that the martensite morphology changed from lath type in the 60% rolled sample to a mixture of lath and dislocation-cell types in the higher rolling reductions. Calculation of the Gibbs free energy change during the reversion treatment showed that the reversion mechanism is shear controlled at the annealing temperature and so the morphology of the reverted austenite is completely dependent on the morphology of the deformation induced martensite. It was found that the austenite had a bimodal grain size distribution in the 80% rolled and annealed state and this is related to the existence of different types of martensite. Increasing the rolling reduction to 93% followed by annealing caused changing of the grain structure to a monomodal like structure, which was mostly covered with small grains of around 300 nm. The existence of bimodal austenite grain size in the 80% rolled and annealed 304L stainless steel led to the improvement of ductility while maintaining a high tensile strength in comparison with the 93% rolled and annealed sample.

  19. Steam oxidation behavior of high strength newly developed ferritic/martensitic steels at 650 C

    Energy Technology Data Exchange (ETDEWEB)

    Agueero, Alina; Gonzalez, Vanessa; Gutierrez, Marcos [Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz (Spain); Mayr, Peter [Massachusetts Inst. of Tech., Cambridge (United States). Dept. of Materials Science and Engineering; Spiradek-Hahn, Krystina [Austrian Institute of Technology GmbH (AIT), Seibersdorf (Austria)

    2010-07-01

    The efficiency of thermal power plants is currently limited by the strength and the oxidation resistance of the commercially available ferritic steels. The higher operating pressures and temperatures, essential to increase efficiency, impose important requirements on the materials from both the mechanical and chemical stability perspective. For instance, a creep rupture strength of 100 MPa after 100.000 hours at 650 C has been defined as the target for new steel development. Moreover, steam oxidation resistance is required as otherwise, at temperatures higher than 600 C, the resulting thick oxide scales will spall, causing blockage on bends as well as overheating of heat exchangers due to a thermal insulation effect, erosion of down-stream components and loss of cross-section in critical components such as blades. It has been shown that in general, a Cr wt. % higher than 9 is required for acceptable oxidation rates at 650 C, but such high Cr content results in a reduction of the creep strength. As an exception, several 9 wt. % steels developed by Abe which also containing Si and Mn, exhibit resistance to steam oxidation but only after having been subjected to a pre-oxidation heat treatment at 650 C for many hours. Substantial efforts are being carried out in Europe, North America and Japan attempting to design and produce steels with these properties. The steam oxidation behavior of high strength new alloys, such as CB2 and FT7 steels developed within the frame of European COST Actions 522 and 536, as well as of a NIMS developed B containing 9Cr3W3CoVNb (NPM) martensitic steel, was studied by exposing these materials to pure flowing steam in the laboratory for periods of time in excess of 10,000 h at 650 C. CB2 and FT7 have similar creep strength to P92 whereas NPM reaches 21,000 h at 100 MPa exceeding by far that of P92 according to the ECCC values. (orig.)

  20. HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Wei [ORNL; Chen, Gaoqiang [ORNL; Chen, Jian [ORNL; Yu, Xinghua [ORNL; Frederick, David Alan [ORNL; Feng, Zhili [ORNL

    2015-01-01

    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  1. Effect of Ni Contents on the Microstructure and Mechanical Properties of Martensitic Stainless Steel Guide Roll by Centrifugal Casting

    Institute of Scientific and Technical Information of China (English)

    Villando Thursdiyanto; Eun-Jae Bae; Eung-Ryul Baek

    2008-01-01

    A novel process based on centrifugal casting was developed to produce martensitic stainless steel for guideroll materials. Centrifugal casting provides a lower production cost and less of the thermal cracking defects which normally occur in the overlaid welding process. In this study, the effects of Ni on the microstructure and mechanical properties of martensitic stainless steel were investigated. The results show that the addition of Ni resulted in a decrease in the volume fraction of delta ferrite and an increase in the volume fraction of the retained austenite, respectively. Moreover, a tensile strength of 1600 MPa with an elongation of 4% were obtained after tempering at 500℃ for 2 h. These values were higher than those obtained by using the conventional overlaid process.

  2. Dynamic Recrystallization and Precipitation in 13Cr Super-Martensitic Stainless Steels

    Science.gov (United States)

    Ebrahimi, Gholam Reza; Momeni, Amir; Jahazi, Mohammad; Bocher, Philippe

    2014-04-01

    The influence of precipitation on the kinetics of static and dynamic recrystallization (DRX) was investigated in AISI 403 and 403Nb martensitic stainless steels. Hot compression tests were performed in the temperature range of 1073 K to 1473 K (800 °C to 1200 °C) and strain rates of 0.001 and 0.1 s-1 to study DRX and precipitation behaviors. In parallel, stress relaxation tests were conducted with pre-strains of 0.1, 0.15, 0.2, and 0.25, a strain rate of 0.1 s-1, and in the 1073 K to 1473 K (800 °C to 1200 °C) temperature range to study the kinetics of precipitation and recrystallization. Samples of hot compression and stress relaxation tests were quenched and the evolution of the microstructure was examined using optical and scanning electron microscopy. The results indicated that DRX interacts with dynamic precipitation (DP) over the temperature range of 1173 K to 1273 K (900 °C to 1000 °C). Hot compression testing results, confirmed by EBSD analysis, indicated that partial DRX occurs before precipitation in 403Nb, at 1073 K (800 °C). By contrast, no DRX was observed in 403 steel. At higher temperatures, i.e., over 1273 K (1000 °C), DRX preceded DP in both steels. Increasing the strain rate raised the temperature range of interaction between DRX and DP up to 1373 K (1100 °C). Strain-induced precipitation (SIP) was observed over the entire range of investigated test temperatures. Static recrystallization (SRX) took place predominantly in the temperature range of 1173 K to 1373 K (900 °C to 1100 °C), at which SIP significantly delayed the SRX finishing time. The results are analyzed in the framework of the classical nucleation theory and the underlying mechanisms are identified.

  3. Fracture mechanics behaviour of ductile cast iron and martensitic steel at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Udoh, A.; Klenk, A.; Roos, E. [Stuttgart Univ. (Germany). MPA; Sasikala, G. [Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam (India)

    2010-07-01

    Ductile cast iron is employed increasingly due to the advantages regarding foundry practice, design as well as economic advantages in the thermal machinery and power plant construction. It is employed preferably where higher toughness is required, e.g. in valves or thickwalled components of thermal or nuclear power plants. For this reason the safety and availability criteria for fracture mechanics assessment of components are necessary in addition to the conventional strength design. Alloys with silicon and molybdenum are developed for the application at higher temperatures. The increase in the thermal efficiency of fossil fired steam power plant that can be achieved by increasing the steam temperature and pressure has provided the incentive for development of the 9% chromium steels towards improved creep rupture strength. During the last twenty years, three such steels, P91 (9Cr-1Mo-VNb), E911 (9Cr-1Mo-1W-V-Nb) and P92 (9Cr-0,5Mo-1,8W-V-Nb), have been developed for commercial production. For application in piping systems and boiler construction sufficient reliable information concerning the long-term behaviour are necessary as well as knowledge about fracture mechanical behaviour in order to ensure integrity of components. Different methods to characterize fracture behaviour of ductile cast iron and martensitic steel at elevated temperature have been employed. The RBR method is a novel and simple method developed at IGCAR for characterizing the ductile fracture behaviour of materials from tensile tests of cylindrical specimens. Using the data evaluated at both institutes, a fracture mechanics characterisation by determining crack initiation and crack resistance by J{sub R}-curves and RBR parameters is presented. (orig.)

  4. Splitting phenomenon in martensitic transformation of X12CrMoWVNbN10-1-1 steel

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Xingang; Han, Lizhan; Gu, Jianfeng [Shanghai Jiao Tong Univ. (China). Shanghai Key Laboratory of Materials Laser Processing and Modification

    2015-06-15

    The splitting phenomenon was detected in martensitic transformation of X12CrMoWVNbN10-1-1 steel using high resolution dilatometry under certain conditions. In-situ observation of austenite grain growth was carried out. Direct experimental results indicated that this splitting is not connected with the concentration gradient in the austenite resulting from the dissolution of carbonitrides during heating, but instead may be caused by the occurrence of abnormal grain growth.

  5. Oxidation behavior of ferritic/martensitic steels in stagnant liquid LBE saturated by oxygen at 600 °C

    Science.gov (United States)

    Shi, Quanqiang; Liu, Jian; Luan, He; Yang, Zhenguo; Wang, Wei; Yan, Wei; Shan, Yiyin; Yang, Ke

    2015-02-01

    Ferritic/martensitic (F/M) steels are primary candidates for application as cladding and structural materials in the Generation IV Nuclear Reactor, especially accelerator driven sub-critical system (ADS). The compatibility of F/M steels with liquid lead-bismuth eutectic (LBE) is a critical issue for development of ADS using liquid LBE as the coolant. In this work, the corrosion tests of two F/M steels, including a novel 9-12 Cr modified F/M steel named SIMP steel and a commercial T91 steel, were conducted in the static oxygen-saturated liquid LBE at 600 °C up to 1000 h, the microstructure of the oxide scale formed on these two steels was analyzed, the relationship between the microstructure and the oxidation behavior was studied, and the reason why the SIMP steel showed better oxidation resistance compared to T91 steel was analyzed. The results of this study confirmed that the oxidation behavior of the F/M steels in liquid metals is influenced by their alloying elements and microstructures.

  6. Microstructure Evolution and Precipitation Behavior of 0Cr16Ni5Mo Martensitic Stainless Steel during Tempering Process

    Institute of Scientific and Technical Information of China (English)

    Wu-hua YUAN; Xue-hui GONG; Yong-qing SUN; Jian-xiong LIANG

    2016-01-01

    The microstructure,morphology of precipitates and retained austenite and the volume fraction of retained austenite in 0Cr1 6Ni5Mo stainless steel during the tempering process were analyzed using optical microscope (OM), transmission electron microscope (TEM),X-ray diffraction (XRD)and scanning transmission electron microscope (STEM).The results show that the microstructure of the tempered steel is mainly composed of tempered martens-ite,retained austenite,and delta ferrite.In the case of samples tempered from 500 to 700 ℃,the precipitates are mainly M23 C6 ,which precipitate along the lath martensite boundaries.The precipitate content increases with the tempering temperature.During the tempering process,the content of retained austenite initially increases and then decreases,the maximum content of retained austenite being 29 vol.% upon tempering at 600 ℃.TEM analysis of the tested steel reveals two morphology types of retained austenite.One is thin film-like retained austenite that exists along the martensite lath boundary.The other is blocky austenite located on packet at the boundary and the original austenite grain boundary.To further understand the stability of reversed austenite,the Ni content in reversed austen-ite was measured using STEM.Results show a significant difference in nickel concentrations between reversed aus-tenite and martensite.

  7. Parametric study of irradiation effects on the ductile damage and flow stress behavior in ferritic-martensitic steels

    Science.gov (United States)

    Chakraborty, Pritam; Biner, S. Bulent

    2015-10-01

    Ferritic-martensitic steels are currently being considered as structural materials in fusion and Gen-IV nuclear reactors. These materials are expected to experience high dose radiation, which can increase their ductile to brittle transition temperature and susceptibility to failure during operation. Hence, to estimate the safe operational life of the reactors, precise evaluation of the ductile to brittle transition temperatures of ferritic-martensitic steels is necessary. Owing to the scarcity of irradiated samples, particularly at high dose levels, micro-mechanistic models are being employed to predict the shifts in the ductile to brittle transition temperatures. These models consider the ductile damage evolution, in the form of nucleation, growth and coalescence of voids; and the brittle fracture, in the form of probabilistic cleavage initiation, to estimate the influence of irradiation on the ductile to brittle transition temperature. However, the assessment of irradiation dependent material parameters is challenging and influences the accuracy of these models. In the present study, the effects of irradiation on the overall flow stress and ductile damage behavior of two ferritic-martensitic steels is parametrically investigated. The results indicate that the ductile damage model parameters are mostly insensitive to irradiation levels at higher dose levels though the resulting flow stress behavior varies significantly.

  8. Effects of surface morphology on fatigue behavior of reduced activation ferritic/martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.W. [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)]. E-mail: kimsw@iae_kyoto-u.ac.jp; Tanigawa, H. [Japan Atomic Energy Agency, 2-4 Shirakata-shirane, Tokai-Mura, Ibaraki-ken 319-1195 (Japan); Hirose, T. [Japan Atomic Energy Agency, 2-4 Shirakata-shirane, Tokai-Mura, Ibaraki-ken 319-1195 (Japan); Shiba, K. [Japan Atomic Energy Agency, 2-4 Shirakata-shirane, Tokai-Mura, Ibaraki-ken 319-1195 (Japan); Kohyama, A. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2007-08-01

    Depending on the pulse lengths, the operating conditions, and the thermal conductivity, oscillating temperature gradients will cause elastic and elastic-plastic cyclic deformation giving rise to (creep-)fatigue in the structural first wall and blanket components of fusion systems. In order to perform an accurate fatigue lifetime assessment for the international thermonuclear experimental reactor-test blanket module (ITER-TBM) and advanced systems utilizing the existing data base, mechanical understanding of fatigue fracture is mandatory. In this work, the low cycle fatigue (LCF) properties of F82H IEA heat were examined for three kinds of surface morphology with miniaturized hourglass-type fatigue specimens (SF-1). The assumed fatigue lifetime of cooling channels for ITER-TBM was also compared and assessed by correlating the results of LCF tests performed with SF-1 type specimens. Fracture surfaces and crack initiation sites were investigated by scanning electron microscopy (SEM)

  9. Irradiation performance of 9--12 Cr ferritic/martensitic stainless steels and their potential for in-core application in LWRs

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R.H.; Gelles, D.S.

    1993-08-01

    Ferritic-martensitic stainless steels exhibit radiation stability and stress corrosion resistance that make them attractive replacement materials for austenitic stainless steels for in-core applications. Recent radiation studies have demonstrated that 9% Cr ferritic/martensitic stainless steel had less than a 30C shift in ductile-to-brittle transition temperature (DBTT) following irradiation at 365C to a dose of 14 dpa. These steels also exhibit very low swelling rates, a result of the microstructural stability of these alloys during radiation. The 9 to 12% Cr alloys to also exhibit excellent corrosion and stress corrosion resistance in out-of-core applications. Demonstration of the applicability of ferritic/martensitic stainless steels for in-core LWR application will require verification of the irradiation assisted stress corrosion cracking behavior, measurement of DBTT following irradiation at 288C, and corrosion rates measurements for in-core water chemistry.

  10. Fractographic examination of reduced activation ferritic/martensitic steel charpy specimens irradiated to 30 dpa at 370{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S.; Hamilton, M.L. [Pacific Northwest National Lab., Richland, WA (United States); Schubert, L.E. [Univ. of Missouri, Rolla, MO (United States)

    1996-10-01

    Fractographic examinations are reported for a series of reduced activation ferritic/Martensitic steel Charpy impact specimens tested following irradiation to 30 dpa at 370{degrees}C in FFTF. One-third size specimens of six low activation steels developed for potential application as structural materials in fusion reactors were examined. A shift in brittle fracture appearance from cleavage to grain boundary failure was noted with increasing manganese content. The results are interpreted in light of transmutation induced composition changes in a fusion environment.

  11. Ultra-fast grain boundary diffusion and its contribution to surface segregation on a martensitic steel. Experiments and modeling

    Science.gov (United States)

    Christien, F.; Le Gall, R.

    2011-09-01

    Phosphorus surface segregation was measured by Auger Electron Spectroscopy on a 17-4 PH martensitic stainless steel at 450, 550 and 600 °C. Surface segregation was shown to be much faster than expected which was attributed to a high contribution of phosphorus diffusion along the former austenitic grain boundaries. A model of surface segregation was developed following the Darken-du Plessis approach and taking account of both bulk and grain boundary solute diffusion. The phosphorus grain boundary diffusion coefficient in 17-4 PH was estimated: DGB17-4 PH steel than in α-iron.

  12. Effect of V and Ta on the precipitation behavior of 12%Cr reduced activation ferrite/martensite steel

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xiang [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Guoquan, E-mail: g.liu@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Hu, Benfu; Wang, Jinsan [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Ullah, Asad [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Department of Mathematics, Karakoram International University, Gilgit-Baltistan (Pakistan)

    2013-08-15

    12%Cr reduced activation ferrite/martensite steels are promising candidate materials for good corrosion and irradiation resistance used for supercritical water-cooled reactor cladding and in-core components. V and Ta are considered to have improved the creep strength of high Cr steels by precipitating as MX phase. In this paper, a series of trial products microalloyed with V and V–Ta are produced, and the microstructure is characterized after quenching at 1050 °C and tempering at 780 °C by using TEM method to investigate the effect of these elements on the precipitation behavior of 12%Cr reduced activation ferrite/martensite steel. The results from both the experimental observations and thermodynamic and kinetic calculations reveal that V and V–Ta can promote the stable MX precipitation instead of M{sub 2}X, thus increasing the volume fraction of M{sub 23}C{sub 6}. Two-phase separation behavior of the (Ta, V)(C, N) carbonitride into a Ta(V)C(N) phase and a V(Ta)N(C) phase in 12Cr3WVTa steel is observed and further discussed. - Highlights: • Microalloyed with V and V-Ta can promote the precipitation of MX instead of M{sub 2}X. • The presence of delta-ferrite in microstructure affects the morphology of MX. • Two-phase separation of MX carbonitride was observed in 12Cr3WVTa steel.

  13. The corrosion resistance of Eurofer 97 and ODS-Eurofer steels for nuclear applications

    Energy Technology Data Exchange (ETDEWEB)

    Terada, M. [Escola Politecnica da Univ. de Sao Paulo, Dept. de Engenharia Metalurgica e de Materiais, Sao Paulo-SP (Brazil); Zschommler Sandim, H.R. [Sao Paulo Univ., Dept. de Engenharia de Materiais, Polo Urbo-Industrial, Lorena-SP (Brazil); Costa, I. [Instituto de Pesquisas Energeticas e Nucleares IPEN-CCTM, Sao Paulo - SP (Brazil); Padilha, A.F. [Escola Politecnica da Universidade de Sao Paulo, Dept. de Engenharia Metalurgica e de Materiais, Sao Paulo-SP (Brazil)

    2009-07-01

    Reduced-activation-ferritic-martensitic (RAFM) steels are considered for application in fusion technology as structural materials for the first wall of future fusion reactors DEMO. Ferritic-martensitic steels show reasonably good thermo-physical and mechanical properties, low sensitivity to radiation-induced swelling and helium embrittlement under (fission) neutron irradiation and good compatibility with major cooling and breeding materials. In recent years, reduced activation versions of this type of steels have been developed in Japan and Europe in laboratory scale and tested with equivalent or even better mechanical properties. In result of a systematic development of reduced activation ferritic-martensitic (RAFM) steels in Europe, the 9% CrWVTa alloy EUROFER was specified, and industrial batches have been produced in a variety of different semi-finished product forms. The EUROFER 97 alloy was developed on the basis of the experience gained with steels of the OPTIFER, MANET and F82H-modified type. Oxide dispersion to strengthen (ODS) alloys have been used in order to increase the working temperature of RAFM steels increasing their potentiality for applications in fusion reactors that operate at temperatures higher than 650 C. The literature on the corrosion properties of these alloys is scarce. In the present work the corrosion resistance of EUROFER 97 and ODS-EUROFER was tested in solutions containing H{sub 2}SO{sub 4} and KSCN at 25 C. The results were compared to those of AISI 430 ferritic and AISI 410 martensitic conventional stainless steels. The as-received samples were tested by electrochemical techniques, specifically, potentiodynamic polarization curves and double loop electrochemical potentio-kinetic reactivation tests. The surfaces were observed by scanning electron microscopy (SEM) after exposure to corrosive media. The results showed that EUROFER 97 and ODS-EUROFER present similar corrosion resistance but lower than that of ferritic AISI 430 and

  14. Effect of W and Ta on creep–fatigue interaction behavior of reduced activation ferritic–martensitic (RAFM) steels

    Energy Technology Data Exchange (ETDEWEB)

    Shankar, Vani, E-mail: vani@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Institute for Plasma Research, Ahmedabad 382428 (India); Mariappan, K.; Sandhya, R.; Laha, K.; Jayakumar, T.; Kumar, E. Rajendra [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Institute for Plasma Research, Ahmedabad 382428 (India)

    2015-11-15

    Highlights: • SR correlated with deformation under CFI in RAFM steels. • Stress relaxation directly related to plastic strain accumulated, inversely to CFI life. • Optimum combination of W and Ta best for CFI life. • RAFM steels demonstrated compressive dwell sensitivity. • SR tends toward constant value at long hold. - Abstract: The aim of this work is to understand the effect of varying tungsten and tantalum contents on creep–fatigue interaction (CFI) behavior of reduced activation ferritic–martensitic (RAFM) steels. Increase in W improved CFI life. Effect of changing Ta and W upon the resultant CFI life seems to be interrelated and an optimum combination of both W and Ta works out to be the best for CFI life. Stress relaxation obtained during application of hold can be a useful parameter to relate deformation and damage in the RAFM steels.

  15. Microstructure and microhardness of CLAM steel irradiated up to 20.8 dpa in STIP-V

    Science.gov (United States)

    Peng, Lei; Ge, Hongen; Dai, Yong; Huang, Qunying; Ye, Minyou

    2016-01-01

    Specimens of China low activation martensitic (CLAM) steel were irradiated in the fifth experiment of SINQ target irradiation program (STIP-V) up to 20.8 dpa/1564 appm He. Microhardness measurements and transmission electron microscope (TEM) observations have been performed to investigate irradiation induced hardening effects. The results of CLAM steel specimens show similar trend in microhardness and microstructure changes with irradiation dose, compared to F82H/Optimax-A steels irradiated in STIP-I/II. Defects and helium bubbles were observed in all specimens, even at a very low dose of 5.4 dpa. For defects and bubbles, the mean size and number density increased with increasing irradiation dose to 13 dpa, and then the mean size increased and number density decreased with the increasing irradiation dose to 20.8 dpa.

  16. Linear Friction Welding Process Model for Carpenter Custom 465 Precipitation-Hardened Martensitic Stainless Steel

    Science.gov (United States)

    Grujicic, M.; Yavari, R.; Snipes, J. S.; Ramaswami, S.; Yen, C.-F.; Cheeseman, B. A.

    2014-06-01

    An Arbitrary Lagrangian-Eulerian finite-element analysis is combined with thermo-mechanical material constitutive models for Carpenter Custom 465 precipitation-hardened martensitic stainless steel to develop a linear friction welding (LFW) process model for this material. The main effort was directed toward developing reliable material constitutive models for Carpenter Custom 465 and toward improving functional relations and parameterization of the workpiece/workpiece contact-interaction models. The LFW process model is then used to predict thermo-mechanical response of Carpenter Custom 465 during LFW. Specifically, temporal evolutions and spatial distribution of temperature within, and expulsion of the workpiece material from, the weld region are examined as a function of the basic LFW process parameters, i.e., (a) contact-pressure history, (b) reciprocation frequency, and (c) reciprocation amplitude. Examination of the results obtained clearly revealed the presence of three zones within the weld, i.e., (a) Contact-interface region, (b) Thermo-mechanically affected zone, and (c) heat-affected zone. While there are no publicly available reports related to Carpenter Custom 465 LFW behavior, to allow an experiment/computation comparison, these findings are consistent with the results of our ongoing companion experimental investigation.

  17. Deuterium recycling rate constants derived from plasma implantation/desorption shots in a martensitic steel surface

    Energy Technology Data Exchange (ETDEWEB)

    Sedano, L.A. [CIEMAT/DIAE, Madrid (Spain); European Commission/JRC, H-Materials Interaction Sector, Ispra (Italy); Esteban, G.A. [UPV-EHU/ETSIIT, D. Nuc. Eng. and Fluid Mec., Bilbao (Spain); Perujo, A. [European Commission/JRC, H-Materials Interaction Sector, Ispra (Italy)

    2001-12-04

    The recombination (K{sub 2}) and dissociation rate constants (K{sub 1}) are essential magnitudes for the tracking of tritium at the first wall (FW) of fusion reactors (FR). This paper presents our plasma implantation/recycling test, the modelling of the experiment and the results obtained for K{sub 2} and K{sub 1} in the case of a deuterium (D{sub 3}{sup +}/D{sub 2}{sup +}) plasma in the martensitic steel DIN 1.4914 (MANET). Once parasitic contributions were accounted, the D{sub 2} release from the target was seen to be surface limited. The values obtained for K{sub 1} and K{sub 2} show low dispersion on impinging flux and ion energies. For K{sub 1} a roughly constant value of 7 x 10{sup -6} mol Pa{sup -1} m{sup -2} s{sup -1} is derived. The obtained K{sub 2} is written as: K{sub 2} = 2.414 exp (-1571/RT) (m{sup 4} mol{sup -1} s{sup -1}), with R = 8.314 J mol{sup -1} K{sup -1}. Our activation energies agree with those existing in the literature derived from permeation experiments. High reflection coefficients are derived, which are in good agreement with the classical theory of ion scattering at low energy. (orig.)

  18. An EFTEM study on Z-phase nucleation in martensitic chromium steels

    Energy Technology Data Exchange (ETDEWEB)

    Golpayegani, A.; Andren, H.O. [Chalmers Univ. of Technology, Gothenburg (Sweden). Microscopy and Microanalysis, Dept. of Applied Physics

    2006-07-01

    9-12% Cr martensitic steels that are used in crucial parts of steam power plants have been found liable to the precipitation of Z-phase after long time at service temperature. This complex nitride consumes vanadium nitrides and leaves the matrix with a relatively big vanadium poor region causing the creep strength of material to fall drastically after several thousand hours. it is of great importance to monitor the initial stages of precipitation of this phase to understand the factors promoting it and to get ideas about ways to suppress or eliminate it. In this work, Z-phase has been characterized using energy-filtered TEM. lt has been found that VN provides the most suitable nucleation site for Z-phase since its lattice has the minimum misfit for starting the nucleation and it also provides vanadium for the growth. it has also been observed that the presence of niobium carbide close to the nucleation site is crucial for the nucleation and growth of this phase. (orig.)

  19. Effects of thermal aging on microstructure and hardness of China low activation martensitic steel welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; Zhang, Junyu [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); University of Science and Technology of China, Hefei, Anhui (China); Xu, Gang, E-mail: gang.xu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2016-08-15

    Highlights: • The hardness of HAZ and WM decreases obviously after aging. • The precipitation of the Laves-phase in BM is similar to that in HAZ. • M{sub 23}C{sub 6} particles are conducive to the nucleation of Laves-phase. • Ta may have a role to retard the early precipitation of the Laves-phase. - Abstract: The aim of this paper is to investigate the microstructure evolution and the change in hardness distribution of China low activation martensitic steel welded joints after thermal aging at 550 °C for 6000 h. The joint was processed by electron beam welding. Compared to the base metal (BM) and heat affected zone (HAZ), Laves-phase was not formed in weld metal (WM) in the as-aged condition due to the higher tantalum content and less precipitation in WM before aging. The dislocation density decreased in HAZ and WM after aging for 6000 h. The property results showed that hardness of WM and HAZ was decreased significantly after aging for 6000 h due to the weakening of solution strengthening and dislocations strengthening. However, the change in the hardness of the base metal by aging remained at a minor level.

  20. A reassessment of the effects of helium on Charpy impact properties of ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S.; Hamilton, M.L. [Pacific Northwest National Lab., Richland, WA (United States); Hankin, G.L. [Loughborough Univ. (United Kingdom)

    1998-03-01

    To test the effect of helium on Charpy impact properties of ferritic/martensitic steels, two approaches are reviewed: quantification of results of tests performed on specimens irradiated in reactors with very different neutron spectra, and isotopic tailoring experiments. Data analysis can show that if the differences in reactor response are indeed due to helium effects, then irradiation in a fusion machine at 400 C to 100 dpa and 1000 appm He will result in a ductile to brittle transition temperature shift of over 500 C. However, the response as a function of dose and helium level is unlikely to be simply due to helium based on physical reasoning. Shear punch tests and microstructural examinations also support this conclusion based on irradiated samples of a series of alloys made by adding various isotopes of nickel in order to vary the production of helium during irradiation in HFIR. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys. However, helium itself, up to 75 appm at over 7 dpa appears to have little effect on the mechanical properties of the alloys. This behavior is instead understood to result from complex precipitation response. The database for effects of helium on embrittlement based on nickel additions is therefore probably misleading and experiments should be redesigned to avoid nickel precipitation.

  1. A closer look at the fracture toughness of ferritic/martensitic steels

    Science.gov (United States)

    Lucon, Enrico

    2007-08-01

    SCK·CEN has characterized the mechanical properties of several ferritic/martensitic steels, both unirradiated and irradiated. Fracture toughness has been evaluated using Charpy impact and fracture mechanics tests. Two safety-related features have emerged: (a) the applicability of the master curve approach (ASTM E1921-05) appears questionable; and (b) irradiation embrittlement is systematically larger when quantified in terms of quasi-static fracture toughness than when measured from Charpy tests. Both issues are examined in detail and possible interpretations are proposed; potential improvements given by the application of more advanced fracture toughness analysis methodologies are discussed. In order to clarify whether the Charpy/fracture toughness difference in embrittlement is due to loading rate effects, dynamic toughness tests have been performed in the unirradiated condition and for two irradiation doses (0.3 and 1.6 dpa). The corresponding dynamic T0 shifts have been compared with the shifts of Charpy and master curve quasi-static transition temperatures. Other possible contributions are examined and discussed.

  2. The development of ferritic-martensitic steels with reduced long-term activation

    Science.gov (United States)

    Ehrlich, K.; Kelzenberg, S.; Röhrig, H.-D.; Schäfer, L.; Schirra, M.

    1994-09-01

    Ferritic-martensitic 9-12% CrMoVNb steels of MANET type possess a number of advantageous properties for fusion reactor application. Their optimization has led to improved creep and fracture-toughness properties. New 9-10% CrWVTa alloys have been developed by KfK/IMF in collaboration with the SAARSTAHL GmbH which have a reduced long-term activation and show in addition superior fracture toughness properties. The calculation of dose rate and other radiological parameters with the presently available FISPACT/EAF codes, extended by KfK files for sequential reactions has shown that the long-term dose-rate in these alloys is governed by the remaining 'impurity level' of Nb and the alloying elements W and Ta. Sequential reactions — though relevant for single alloying elements like Cr, Mn, V and N — provide only a second order effect in Fe-based alloys. A challenge for the future materials development is the production of alloys with the desired narrow specification of elements and impurities, which necessitates new ways of steelmaking.

  3. Microstructural evolution and examination of α'-martensite during a multi-pass dissimilar stainless steel GTAW process

    Science.gov (United States)

    Hsieh, Chih-Chun; Lin, Dong-Yih; Wu, Weite

    2008-10-01

    This study discusses the microstructural evolution and examination of α'-martensite in fusion zones and heat-affected zones under multi-pass dissimilar stainless steels welding. The morphology, quantity, grain size, and chemical composition of the α'-martensite and δ-ferrite were analyzed using optical microscopy (OM), an image analyzer (IA), a ferritscope (FS), field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), respectively. Recrystallization induced grain refinement of α'-martensite in over-lapping heat-affected zones (HAZ1 > 2 and HAZ2 > 3) after the second and third pass of welding. The Creq, Nieq, and K-factor values were calculated in an elemental analysis according to the Kaltenhauser equation. The higher Nieq (8.0-9.26) and lower K-factor (7.73-9.50) were examined for α'-martensite in the second pass fusion zone (FZ-2) as opposed to δ-ferrite. Comparatively, the ä-ferrite indicated higher Creq (22.30-22.91) and K-factor (15.72-16.68) values.

  4. Influence of austenitizing temperature on microstructure and mechanical properties of AISI 431 martensitic stainless steel electron beam welds

    Energy Technology Data Exchange (ETDEWEB)

    Rajasekhar, A. [Department of Mechanical Engineering, SVITS, Mahaboob Nagar 509 001 (India)], E-mail: adula.rajasekhar@rediffmail.com; Madhusudhan Reddy, G.; Mohandas, T. [Defence Metallurgical Research Laboratory, Hyderabad 500 058 (India); Murti, V.S.R. [Department of Mechanical Engineering, SVITS, Mahaboob Nagar 509 001 (India)

    2009-05-15

    The relative effects of various austenitizing temperatures on microstructure and mechanical properties of electron beam welds of AISI 431martensitic stainless steel were studied. The post-weld heat treatments consist of austenitizing the weld samples for 1 h at various temperatures, i.e., at 950 deg. C, 1000 deg. C, 1050 deg. C, 1100 deg. C and at 1150 deg. C and air cooling followed by double tempering, i.e., tempering at 670 + 600 deg. C. In the as-welded condition the microstructure contains dendritic structure with ferrite network and retained austenite in a matrix of un-tempered martensite. The prior austenite grain size increased with increase in austenitizing temperature. Parent metal grain size was coarser as compared to grain size in the weld zone in respective conditions. Retained austenite content increased with increase in the austenitizing temperature. Presence of undissolved carbides was observed in welds and parent metal austenitized up to 1000 deg. C and they dissolved at austenitizing temperature {>=} 1050 deg. C. Coarsening of martensite laths was observed after tempering. The martensite laths were coarser in the samples subjected to higher austenitizing temperatures. Optimum mechanical properties, i.e., strength, hardness and toughness were observed when austenitized between 1050 deg. C and 1100 deg. C followed by tempering. Austenitizing at 1150 deg. C and tempering resulted in inferior mechanical properties. The mechanism for the observed trends is discussed in relation to the microstructure, fracture features and mechanical properties.

  5. Load partitioning between ferrite/martensite and dispersed nanoparticles of a 9Cr ferritic/martensitic (F/M) ODS steel at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guangming; Mo, Kun; Miao, Yinbin; Liu, Xiang; Almer, Jonathan; Zhou, Zhangjian; Stubbins, James F.

    2015-06-18

    In this study, a high-energy synchrotron radiation X-ray technique was used to investigate the tensile deformation processes of a 9Cr-ODS ferritic/martensitic (F/M) steel at different temperatures. Two minor phases within the 9Cr-ODS F/M steel matrix were identified as Y2Ti2O7 and TiN by the high-energy X-ray diffraction, and confirmed by the analysis using energy dispersive X-ray spectroscopy (EDS) of scanning transmission electron microscope (STEM). The lattice strains of the matrix and particles were measured through the entire tensile deformation process. During the tensile tests, the lattice strains of the ferrite/martensite and the particles (TiN and Y2Ti2O7) showed a strong temperature dependence, decreasing with increasing temperature. Analysis of the internal stress at three temperatures showed that the load partitioning between the ferrite/martensite and the particles (TiN and Y2Ti2O7) was initiated during sample yielding and reached to a peak during sample necking. At three studied temperatures, the internal stress of minor phases (Y2Ti2O7 and TiN) was about 2 times that of F/M matrix at yielding position, while the internal stress of Y2Ti2O7 and TiN reached about 4.5-6 times and 3-3.5 times that of the F/M matrix at necking position, respectively. It indicates that the strengthening of the matrix is due to minor phases (Y2Ti2O7 and TiN), especially Y2Ti2O7 particles. Although the internal stresses of all phases decreased with increasing temperature from RT to 600 degrees C, the ratio of internal stresses of each phase at necking position stayed in a stable range (internal stresses of Y2Ti2O7 and TiN were about 4.5-6 times and 3-3.5 times of that of F/M matrix, respectively). The difference between internal stress of the F/M matrix and the applied stress at 600 degrees C is slightly lower than those at RI and 300 degrees C, indicating that the nanoparticles still have good strengthening effect at 600 degrees C. (C) 2015 Elsevier B.V. All rights reserved.

  6. Effect of tensile pre-strain at different orientation on martensitic transformation and mechanical properties of 316L stainless steel

    Science.gov (United States)

    Wibowo, F.; Zulfi, F. R.; Korda, A. A.

    2017-01-01

    Deformation induced martensite was studied in 316L stainless steel through tensile pre-strain deformation in the rolling direction (RD) and perpendicular to the rolling direction (LT) at various %pre-strain. The experiment was carried out at various given %pre-strain, which were 0%, 4.6%, 12%, 17.4%, and 25.2% for the RD, whereas for LT were 0%, 4.6%, 12%, 18%, and 26% for LT. Changes in the microstructure and mechanical properties were observed using optical microscope, tensile testing, hardness testing, and X-ray diffraction (XRD) analysis. The experimental results showed that the volume fraction of martensite was increased as the %pre-strain increased. In the same level of deformation by tensile pre-strain, the volume of martensite for RD was higher than that with LT direction. The ultimate tensile strength (UTS), yield strength (YS), and hardness of the steel were increased proportionally with the increases in %pre-strain, while the value of elongation and toughness were decreased with the increases in %pre-strain.

  7. The potential significance of microalloying with niobium in governing very high cycle fatigue behavior of bainite/martensite multiphase steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P., E-mail: zhaoping12@mails.tsinghua.edu.cn [Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Beijing Iron & Steel Research Institute, Special Steel Institute, Beijing 100081 (China); Cheng, C.; Gao, G.; Hui, W. [Materials Science & Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Materials and Biomedical Engineering, University of Texas, El Paso 500 W. University Avenue, El Paso, TX 79968-0520 (United States); Bai, B.; Weng, Y. [Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2016-01-05

    We elucidate here the effect of microalloying with niobium (Nb) on very high cycle fatigue (VHCF) behavior in high-strength C–Mn–Si–Cr bainite/martensite (B/M) multiphase steels studied through ultrasonic fatigue testing. The tensile strength (R{sub m}) and fatigue limit strength after 10{sup 9} cycles (σ{sub w9}) and in the non-failure condition of the steel microalloyed with Nb were 1640 MPa and 900 MPa, respectively. Thus, the value of σ{sub w9}/R{sub m} exceeded in comparison to conventional steels and was approximate 0.55. Three types of failure modes were observed in Nb-bearing steels depending on the surface condition, inclusion, and the matrix microstructure, i.e., surface defect-induced failure mode (S-mode), inclusion-induced failure mode (I-mode), and non-inclusion induced failure mode (N-mode). Only two failure modes were observed in Nb-free steels, the S-mode and the N-mode. The study clearly suggests that Nb had a distinct effect on the VHCF properties of B/M steels. The VHCF limit of Nb-bearing steel was enhanced by 200 MPa because of refinement of the microstructure and pinning of dislocations by randomly distributed nanometer-sized Nb(C, N) precipitates. It is underscored that microalloying with Nb is a potential approach to enhance VHCF properties in advanced high-strength steels.

  8. Effect of the state of stress on the strain-induced martensite formation in 03Kh14N11K5M2YuT steel

    Science.gov (United States)

    Maltseva, L. A.; Loginov, Yu. N.; Maltseva, T. V.; Sharapova, V. A.

    2013-09-01

    The structural changes that occur in a metastable austenitic Fe-Cr-Ni-based steel during cold plastic deformation by drawing and tension are analyzed. A relation between the structure of the steel and its mechanical and magnetic properties is established. It is concluded that the stress state scheme considerably affects the rate of martensite formation.

  9. Investigation of the precipitation mechanism in HAZ of super-martensitic stainless steels. Two-pass weld simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ladanova, Elena; Solberg, Jan K. [The Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Rogne, Trond [SINTEF Materials and Chemistry, N-7465 Trondheim (Norway)

    2004-07-01

    Weld simulation is widely used for studying weldability of steels. Mostly, HAZ of one pass welding is simulated, and the produced specimens are mainly used for mechanical testing. Another way of applying weld simulation is to find the temperature history giving a certain microstructure observed in the HAZ of a real multipass weld. In the present work, a two-pass weld simulation was used to investigate the precipitation mechanism of carbides in the HAZ of two super-martensitic stainless steels. Previously, a model for carbide precipitation was suggested. According to this model, a reheating of the HAZ in the martensitic stage is needed to provoke strong carbide formation. In the present work, the peak temperatures of the first and second heating pass and also the temperature of the inter-pass holding were varied together with holding time during the reheat (the second pass). The most favourable heating regime for grain boundary carbide precipitation was found for both investigated steels. In addition, measurements of the chromium content across prior austenite grain boundaries were done for one of the investigated steels. The thin foils were prepared from the specimens where the strongest carbide precipitation was observed. (authors)

  10. Mechanical properties of neutron-irradiated nickel-containing martensitic steels: II. Review and analysis of helium-effects studies

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge National Laboratory, Metals and Ceramics Division, Building 4500S, P.O. Box 2008, MS 6151, Oak Ridge, TN 37831-6151 (United States)]. E-mail: kluehrl@ornl.gov; Hashimoto, N. [Oak Ridge National Laboratory, Metals and Ceramics Division, Building 4500S, P.O. Box 2008, MS 6151, Oak Ridge, TN 37831-6151 (United States); Sokolov, M.A. [Oak Ridge National Laboratory, Metals and Ceramics Division, Building 4500S, P.O. Box 2008, MS 6151, Oak Ridge, TN 37831-6151 (United States); Maziasz, P.J. [Oak Ridge National Laboratory, Metals and Ceramics Division, Building 4500S, P.O. Box 2008, MS 6151, Oak Ridge, TN 37831-6151 (United States); Shiba, K. [Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Tokai, Ibaraki 319-1195 (Japan); Jitsukawa, S. [Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Tokai, Ibaraki 319-1195 (Japan)

    2006-10-15

    In part I of this helium-effects study on ferritic/martensitic steels, results were presented on tensile and Charpy impact properties of 9Cr-1MoVNb (modified 9Cr-1Mo) and 12Cr-1MoVW (Sandvik HT9) steels and these steels containing 2% Ni after irradiation in the High Flux Isotope Reactor (HFIR) to 10-12 dpa at 300 and 400 deg. C and in the Fast Flux Test Facility (FFTF) to 15 dpa at 393 deg. C. The results indicated that helium caused an increment of hardening above irradiation hardening produced in the absence of helium. In addition to helium-effects studies on ferritic/martensitic steels using nickel doping, studies have also been conducted over the years using boron doping, ion implantation, and spallation neutron sources. In these previous investigations, observations of hardening and embrittlement were made that were attributed to helium. In this paper, the new results and those from previous helium-effects studies are reviewed and analyzed.

  11. Experimental Analysis of Residual Stresses in Samples of Austenitic Stainless Steel Welded on Martensitic Stainless Steel Used for Kaplan Blades Repairs

    Directory of Open Access Journals (Sweden)

    Vasile Cojocaru

    2011-01-01

    Full Text Available Residual stresses occur in materials as a result of mechanical processes: welding, machining, grinding etc. If residual stresses reach high values they can accelerate the occurrence of cracks and erosion of material. An experimental research was made in order to study the occurrence of residual stresses in the repaired areas of hydraulic turbine components damaged by cavitation erosion. An austenitic stainless steel was welded in various layer thicknesses on a martensitic stainless steel base. The residual stresses were determined using the hole drilling strain gage method.

  12. Diffusion Bonding Beryllium to Reduced Activation Ferritic Martensitic Steel: Development of Processes and Techniques

    Science.gov (United States)

    Hunt, Ryan Matthew

    Only a few materials are suitable to act as armor layers against the thermal and particle loads produced by magnetically confined fusion. These candidates include beryllium, tungsten, and carbon fiber composites. The armor layers must be joined to the plasma facing components with high strength bonds that can withstand the thermal stresses resulting from differential thermal expansion. While specific joints have been developed for use in ITER (an experimental reactor in France), including beryllium to CuCrZr as well as tungsten to stainless steel interfaces, joints specific to commercially relevant fusion reactors are not as well established. Commercial first wall components will likely be constructed front Reduced Activation Ferritic Martensitic (RAFM) steel, which will need to be coating with one of the three candidate materials. Of the candidates, beryllium is particularly difficult to bond, because it reacts during bonding with most elements to form brittle intermetallic compounds. This brittleness is unacceptable, as it can lead to interface crack propagation and delamination of the armor layer. I have attempted to overcome the brittle behavior of beryllium bonds by developing a diffusion bonding process of beryllium to RAFM steel that achieves a higher degree of ductility. This process utilized two bonding aids to achieve a robust bond: a. copper interlayer to add ductility to the joint, and a titanium interlayer to prevent beryllium from forming unwanted Be-Cu intermetallics. In addition, I conducted a series of numerical simulations to predict the effect of these bonding aids on the residual stress in the interface. Lastly, I fabricated and characterized beryllium to ferritic steel diffusion bonds using various bonding parameters and bonding aids. Through the above research, I developed a process to diffusion bond beryllium to ferritic steel with a 150 M Pa tensile strength and 168 M Pa shear strength. This strength was achieved using a Hot Isostatic

  13. In-Situ Investigation of Strain-Induced Martensitic Transformation Kinetics in an Austenitic Stainless Steel by Inductive Measurements

    Directory of Open Access Journals (Sweden)

    Carola Celada-Casero

    2017-07-01

    Full Text Available An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ to martensite (α′ phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction of α′-martensite has been found by comparing the results to the ex-situ characterization by magnetization measurements, light optical microscopy, and X-ray diffraction. The sensor has allowed for the observation of the stepwise transformation behavior, a not-well-understood phenomena that takes place in large regions of the bulk material and that so far had only been observed by synchrotron X-ray diffraction.

  14. Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

    Energy Technology Data Exchange (ETDEWEB)

    Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-05-15

    A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

  15. Investigation on hot-dip aluminised and subsequent HIP'ped steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Glasbrenner, H.; Konys, J. E-mail: juergen.konys@imf.fzk.de

    2001-11-01

    Tritium permeation can be reduced significantly by a suitable coating on the structural material. Since alumina has the capability of tritium permeation reduction the development of such coatings on ferritic martensitic steels by hot-dip aluminising of F82H-mod. steel sheets was already performed successfully. An improvement of these coatings were achieved by subsequent HIP'ping at 1040 deg. C for 0.5 h at 250, 500 and 750 bar and subsequently tempered at 750 deg. C for 1 h at 1 bar. All samples were investigated by means of metallographical examination, EDX line scan analysis and Vickers micro hardness measurements. The high pressure produced two observed changes: firstly, with increasing pressure the thickness of the FeAl phase increases and the thickness of the {alpha}-Fe(Al) phase decreases, and secondly the formation of pores could be suppressed successfully. The Vickers micro hardness of the base material F82H-mod. is not influenced by the heat-treatment under pressure and is about 215 HV.

  16. Metallurgical properties of reduced activation martensitic steel Eurofer'97 in the as-received condition and after thermal ageing

    Science.gov (United States)

    Fernández, P.; Lancha, A. M.; Lapeña, J.; Serrano, M.; Hernández-Mayoral, M.

    2002-12-01

    This paper describes the microstructural studies and the mechanical testing (hardness, tensile and charpy tests) performed on the Eurofer'97 steel in the as-received condition and after thermal ageing treatments up to 600 °C. In addition, fracture toughness tests on the as-received condition have been carried out in order to determine the Master Curve. During the thermal ageing treatments studied (500 °C/5000 h and 600 °C/1000 h) the general microstructure of the steel (tempered martensite with M 23C 6 and MX precipitates) remained stable. Only a slight growth of the particles has been observed. In terms of mechanical properties, the Eurofer'97 steel exhibited similar values of tensile properties (tensile and yield strength) and ductile-brittle transition temperature regardless of the material condition studied.

  17. Improved creep and oxidation behavior of a martensitic 9Cr steel by the controlled addition of boron and nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Mayr, Peter [Massachusetts Institute of Technology, Cambridge, MA (United States). Dept. of Materials Science; Graz Univ. of Technology (Austria). Inst. of Material Science and Welding; Holzer, Ivan; Mendez-Martin, Francisca [Graz Univ. of Technology (Austria). Inst. of Material Science and Welding; Albu, Mihaela; Mitsche, Stefan [Graz Univ. of Technology (Austria). Inst. for Electron Microscopy; Gonzalez, Vanessa; Agueero, Alina [Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz (Spain)

    2010-07-01

    This manuscript gives an overview on recent developments of a martensitic steel grade based on 9Cr3W3CoVNb with controlled additions of boron and nitrogen. Alloy design by thermodynamic equilibrium calculations and calculation of boron-nitrogen solubility is discussed. Out of this alloy design process, two melts of a 9Cr3W3CoVNbBN steel were produced. The investigation focused on microstructural evolution during high temperature exposure, creep properties and oxidation resistance in steam at 650 C. Microstructural characterization of ''as-received'' and creep exposed material was carried out using conventional optical as well as advanced electron microscopic methods. Creep data at 650 was obtained at various stress levels. Longest-running specimens have reached more than 20,000 hours of testing time. In parallel, long-term oxidation resistance has been studied at 650 C in steam atmosphere up to 5,000 hours. Preliminary results of the extensive testing program on a 9Cr3W3CoVNbBN steel show significant improvement in respect to creep strength and oxidation resistance compared to the state-of-the-art 9 wt. % Cr martensitic steel grades. Up to current testing times, the creep strength is significantly beyond the +20% scatterband of standard grade P92 material. Despite the chromium content of 9 wt % the material exhibits excellent oxidation resistance. Steam exposed plain base material shows comparable oxidation behavior to coated material, and the corrosion rate of the boron-nitrogen controlled steel is much lower compared to standard 9 wt % Cr steel grades, P91 and P92. (orig.)

  18. Isothermal and thermomechanical fatigue studies on a modified 9Cr-1Mo ferritic martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Nagesha, A., E-mail: nagesh@igcar.gov.in [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Kannan, R. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Sastry, G.V.S. [Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Sandhya, R. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Singh, Vakil [Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Bhanu Sankara Rao, K. [School of Engineering Sciences and Technology, Central University, Hyderabad (India); Mathew, M.D. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2012-09-30

    In-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) tests were carried out on a modified 9Cr-1Mo ferritic martensitic steel under a mechanical strain control mode employing a strain amplitude of {+-}0.4%. Different temperature ranges in the interval, 573-923 K were employed for the tests which were carried out using a constant strain rate of 1.2 Multiplication-Sign 10{sup -4} s{sup -1}. Isothermal low cycle fatigue tests were also performed concurrently at the maximum temperatures (T{sub max}) of TMF tests on similar specimens and employing the same strain amplitude and strain rate. The life variation was seen to follow the sequence: IF < OP TMF < IP TMF. However, the difference in lives narrowed down with an increase in the T{sub max} of TMF/test temperature of IF cycling. The cyclic stress response behaviour of the alloy was characterized by a continuous softening under all testing conditions. The lower lives observed under OP TMF in comparison with IP cycling was attributed to a combined influence of oxide cracking and a higher tensile hysteresis loop energy in the former. Cyclic life under IP TMF was observed to reduce more drastically compared to OP cycling with increase in T{sub max}, owing to the increasing prominence of dynamic recovery effects coupled with creep deformation. Transmission electron microscopy (TEM) investigations revealed that IF cycling at the T{sub max} resulted in a significantly greater substructural recovery compared to that produced by TMF cycling as a consequence of which, the former led to lower lives compared to both the IP and OP TMF. Dynamic strain ageing (DSA) associated with serrated flow was observed as the deformation temperature under TMF cycling traversed the regime of 300-400 Degree-Sign C.

  19. Gap Analysis of Material Properties Data for Ferritic/Martensitic HT-9 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Neil R. [Los Alamos National Laboratory; Serrano De Caro, Magdalena [Los Alamos National Laboratory; Rodriguez, Edward A. [Global Nuclear Network Analysis, LLC

    2012-08-28

    The US Department of Energy (DOE), Office of Nuclear Energy (NE), is supporting the development of an ASME Code Case for adoption of 12Cr-1Mo-VW ferritic/martensitic (F/M) steel, commonly known as HT-9, primarily for use in elevated temperature design of liquid-metal fast reactors (LMFR) and components. In 2011, Los Alamos National Laboratory (LANL) nuclear engineering staff began assisting in the development of a small modular reactor (SMR) design concept, previously known as the Hyperion Module, now called the Gen4 Module. LANL staff immediately proposed HT-9 for the reactor vessel and components, as well as fuel clad and ducting, due to its superior thermal qualities. Although the ASME material Code Case, for adoption of HT-9 as an approved elevated temperature material for LMFR service, is the ultimate goal of this project, there are several key deliverables that must first be successfully accomplished. The most important key deliverable is the research, accumulation, and documentation of specific material parameters; physical, mechanical, and environmental, which becomes the basis for an ASME Code Case. Time-independent tensile and ductility data and time-dependent creep and creep-rupture behavior are some of the material properties required for a successful ASME Code case. Although this report provides a cursory review of the available data, a much more comprehensive study of open-source data would be necessary. This report serves three purposes: (a) provides a list of already existing material data information that could ultimately be made available to the ASME Code, (b) determines the HT-9 material properties data missing from available sources that would be required and (c) estimates the necessary material testing required to close the gap. Ultimately, the gap analysis demonstrates that certain material properties testing will be required to fulfill the necessary information package for an ASME Code Case.

  20. Corrosion test of the ferritic-martensitic steel (Gr. 91) in molten Pb.Li

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yang Il; Park, Jeong Yong; Choi, Byoung Kwon; Jeong, Yong Hwan; Lee, Dong Won [Nuclea Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cho, Seung Yon [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    Design concepts for tritium breeding blankets for DEMO and/or fusion power plants are going to be tested by using various types of TBMs (test blanket modules) in ITER. Two TBM systems are proposed by Korea, i.e. a helium-cooled solid breeder (HCSB) blanket and a helium-cooled molten lithium (HCML) blanket, among several candidates. Both the TBMs consist of a ferritic-martensitic steel (FMS) as a structural material. In particular, FMS contacts with flowing molten metals (Pb.Li or Li) during the operation in the case of HCML blanket. Since FMS is corrosive in a Pb.Li solution, the compatibility of structural materials with breeder materials should be investigated. The compatibility of EUROFER with Pb.Li was tested at temperatures up to 550 .deg. C with PbLi flowing at up to 0.22 m/s for 5000 h in Europe. China performed corrosion tests of CLAM in experimental loops, such as the thermal convection Pb.Li loop (DRAGON I) at 450.500 .deg. C, the high-temperature thermal convection Pb.Li loop (DRAGON II) with up to 700 .deg. C. Japan also tested JLF alloys in the Li loop operated at up to 700 .deg. C. However, Korea does not have any developed FMS nor an experience of the corrosion test of FMS in a Pb.Li loop. The current study may be a first step to the compatibility test of TBM, although the test includes only a static Pb.Li melt

  1. The evaluation of tempered martensite embrittlement in 4130 steel by instrumented charpy V-notch testing

    Science.gov (United States)

    Zia-Ebrahimi, F.; Krauss, G.

    1983-06-01

    Tempered martensite embrittlement (TME) was studied in vacuum-melted 4130 steel with either 0.002 or 0.02 wt pct P. TME was observed as a severe decrease in Charpy V-notch impact energy, from 46 ft-lb. at 200 °C to 35 ft-lb. at 300 °C in the low P alloy. The impact energy of the high P alloy was consistently lower than that of the low P alloy in all tempered conditions. Fracture was transgranular for all specimens; therefore, segregation of P to the prior austenitic grain boundaries was not a factor in the o°Currence of TME. Analysis of load-time curves obtained by instrumented Charpy testing revealed that the embrittlement is associated with a drop in the pre-maximum-load and post-unstable-fracture energies. In specimens tempered at 400 °C the deleterious effect of phosphorus on impact energy became pronounced, a result more consistent with classical temper embrittlement rather than TME. A constant decrease in pre-maximum-load energy due to phosphorus content was observed. The pre-maximum-load energy decreases with increasing tempering temperature in the range of 200 °C to 400 °C, a result explained by the change in work hardening rate. Carbon extraction replicas of polished and etched as-quenched specimens revealed the presence of Fe2MoC and/or Fe3C carbides retained after austenitizing. Ductile crack extension close to the notch root was related to the formation of fine micro voids at the retained carbides.

  2. Estimation of Oxidation Kinetics and Oxide Scale Void Position of Ferritic-Martensitic Steels in Supercritical Water

    Directory of Open Access Journals (Sweden)

    Li Sun

    2017-01-01

    Full Text Available Exfoliation of oxide scales from high-temperature heating surfaces of power boilers threatened the safety of supercritical power generating units. According to available space model, the oxidation kinetics of two ferritic-martensitic steels are developed to predict in supercritical water at 400°C, 500°C, and 600°C. The iron diffusion coefficients in magnetite and Fe-Cr spinel are extrapolated from studies of Backhaus and Töpfer. According to Fe-Cr-O ternary phase diagram, oxygen partial pressure at the steel/Fe-Cr spinel oxide interface is determined. The oxygen partial pressure at the magnetite/supercritical water interface meets the equivalent oxygen partial pressure when system equilibrium has been attained. The relative error between calculated values and experimental values is analyzed and the reasons of error are suggested. The research results show that the results of simulation at 600°C are approximately close to experimental results. The iron diffusion coefficient is discontinuous in the duplex scale of two ferritic-martensitic steels. The simulation results of thicknesses of the oxide scale on tubes (T91 of final superheater of a 600 MW supercritical boiler are compared with field measurement data and calculation results by Adrian’s method. The calculated void positions of oxide scales are in good agreement with a cross-sectional SEM image of the oxide layers.

  3. A Novel Martensitic Creep-Resistant Steel Strengthened by MX Carbonitrides with Extremely Low Coarsening Rates: Design and Characterization

    Science.gov (United States)

    Lu, Qi; Ma, Wenjie; Yan, Wei; Yang, Ke; Toda, Yoshiaki; van der Zwaag, Sybrand; Xu, Wei

    2016-09-01

    A general computational alloy design approach, based on thermodynamics and thermokinetics and coupled with a genetic algorithm optimization routine, was applied to the design of novel creep martensitic resistant steels. The optimal alloy suggested by the model has a high density of barely coarsening MX carbonitride precipitates. The model yielded precise values for the concentrations of the 10 alloying elements considered. The model alloy was produced on a 10 kg lab scale. Samples of the new alloy of one of the best commercial martensitic steels on the market P92 were subjected to a high aging temperature of 923 K (650 °C) for times up to 1000 hours. The microstructure of the new alloy in the as-produced state as well as after 1000 hours exposure has all the intended features as predicted by the model. The coarsening rate of the MX rate carbonitrides was substantially lower than that of the precipitates in the P92 steel. The very low coarsening rate explains the superior hardness at very long exposure times.

  4. Fracture mechanisms in dual phase steels based on the acicular ferrite + martensite/austenite microstructure

    Science.gov (United States)

    Poruks, Peter

    The fracture mechanisms of low carbon microalloyed plate steels based on the acicular ferrite + marten site/austenite microstructure (AF + M/A) are investigated. The final microstructure consists of a dispersed phase of submicron equi-axed martensite particles with a bainitic ferrite matrix. A series of plates with M/A volume fractions of 0.076--0.179 are studied. Brittle fracture is investigated by Instrumented Charpy impact testing of samples at -196°C and subsequent metallography. The M/A particles are identified as the crack nucleation sites and the cleavage fracture stress calculated to be 2400 MPa in a complete AF microstrucuture. This value is significantly larger than in steels that contain significant proportions of conventional bainite. Standard Charpy and Instrumented Charpy impact testing is conducted through a temperature range from -80 to + 22°C to study ductile fracture behaviour. The total absorbed energy is separated into energies of crack nucleation and of crack propagation. It is found that the energy of crack nucleation is weakly dependent on the volume fraction of M/A and completely independent of temperature over the range studied. The crack propagation energy varies significantly with both variables, decreasing with increased volume fraction of M/A and with decreasing temperature. The peak load in the instrumented Charpy data is used to calculate the dynamic fracture toughness, KId, which is found to be 105--120 MPa-m1/2. The void nucleation and void growth stages of ductile fracture are studied by metallographic examination of tensile bars. The sites of void nucleation are identified as inclusions and M/A particles. Voids nucleate at the M/A particles by decohesion of the particle-matrix interface. A constant void nucleation strain of epsilon = 0.90 +/- 0.05 is measured for all of the samples independent of the volume fraction of M/A. A stress-based criterion is used to predict void nucleation and the interface strength is determined to be

  5. Improvement of the strength of a metastable austenitic stainless steel by cyclic deformation-induced martensitic transformation at 103 K

    Energy Technology Data Exchange (ETDEWEB)

    Bayerlein, M.; Mughrabi, H. (Inst. fuer Werkstoffwissenschaften, Lehrstuhl 1, Univ. Erlangen-Nuernberg, Erlangen (Germany)); Kesten, M.; Meier, B. (Messer Griesheim GmbH, Koeln (Germany))

    1992-12-15

    Specimens of a metastable austenitic stainless steel were cyclically deformed at 103 K under constant plastic strain control with constant plastic strain ranges [Delta][epsilon][sub pl] = 1% and 2%. The tests were performed both with a symmetrical plastic strain amplitude (mean plastic strain anti [epsilon][sub pl] = 0) and with an asymetrical plastic strain amplitude (anti [epsilon][sub pl] > 0) with the minimum plastic strain equal to zero. The cyclic deformation behaviour was investigated, especially in the stage of cyclic hardening, and correlated with the deformation-induced formation of martensitic phases which could be detected by transmission electron microscopy. The effect of the transformed martensite on the mechanical properties of the steel was quantified by subsequent tensile tests at room temperature with the cyclically deformed specimens. In contrast to results of earlier studies at room temperature, no cumulative plastic ''incubation'' strain was necessary at 103 K to trigger the deformation-induced martensitic transformation. At [Delta][epsilon][sub pl] = 2% and anti [epsilon][sub pl] = 0 the maximum cyclic range was attained after only 18 cycles. In the reference test with an asymmetrical plastic strain amplitude (anti [epsilon][sub pl] = 1%) 23 cycles were required to reach the maximum cyclic stress range. Tension tests revealed an increase of up to 200% in the 1% offset yield stress and a 75% increase in the tensile strength at room temperature after cycling the specimens to the maximum stress range with either symmetrical or asymmetrical plastic strain amplitudes. The ductility and the toughness of the steel remained surprisingly high with an elongation after failure of 45%. (orig.).

  6. Effect of martensite to austenite reversion on the formation of nano/submicron grained AISI 301 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, M.; Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, A., E-mail: ahmad_k@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandari, M. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2009-11-15

    The martensite to austenite reversion behavior of 90% cold rolled AISI 301 stainless steel was investigated in order to refine the grain size. Cold rolled specimens were annealed at 600-900 deg. C, and subsequently characterized by scanning electron microscopy, X-ray diffraction, Feritscope, and hardness measurements. The effects of annealing parameters on the formation of fully-austenitic nano/submicron grained structure and the mechanisms involved were studied. It was found that annealing at 800 deg. C for 10 s exhibited the smallest average austenite grain size of 240 {+-} 60 nm with an almost fully-austenitic structure.

  7. Martensitic transformation and residual stresses after thermomechanical treatment of heat treatable steel 42CrMo4 (SAE 4140)

    Energy Technology Data Exchange (ETDEWEB)

    Weise, A. [Technische Univ. Chemnitz-Zwickau, Chemnitz (Germany). Fakultaet fuer Maschinenbau und Verfahrenstechnik; Fritsche, G. [Technische Univ. Chemnitz-Zwickau, Chemnitz (Germany). Fakultaet fuer Maschinenbau und Verfahrenstechnik

    1996-01-01

    The influence of thermomechanical deformation on the residual stresses caused by quenching in bar shaped specimens of heat treatable steel 42CrMo4 has been investigated using a mechanical method for determining the distribution of residual stresses of the first kind. The results obtained show that the residual stress distribution after quenching is affected by the strengthening and softening of the austenite as a result of deformation and recrystallization and the modified transformation behaviour in martensite stage. An attempt is made to discuss qualitatively the influence of these changes on the generation of residual stresses as compared to results obtained after conventional hardening. (orig.).

  8. Status and key issues of reduced activation ferritic/martensitic steels as the structural material for a DEMO blanket

    Science.gov (United States)

    Tanigawa, H.; Shiba, K.; Möslang, A.; Stoller, R. E.; Lindau, R.; Sokolov, M. A.; Odette, G. R.; Kurtz, R. J.; Jitsukawa, S.

    2011-10-01

    The status and key issues of reduced activation ferritic/martensitic (RAFM) steels R&D are reviewed as the primary candidate structural material for fusion energy demonstration reactor blankets. This includes manufacturing technology, the as-fabricated and irradiates material database and joining technologies. The review indicated that the manufacturing technology, joining technology and database accumulation including irradiation data are ready for initial design activity, and also identifies various issues that remain to be solved for engineering design activity and qualification of the material for international fusion material irradiation facility (IFMIF) irradiation experiments that will validate the data base.

  9. Status and key issues of reduced activation ferritic/martensitic steels as the structural material for a DEMO blanket

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, Hiroyasu [ORNL; Stoller, Roger E [ORNL; Sokolov, Mikhail A [ORNL; Odette, G.R. [University of California, Santa Barbara; Jitsukawa, Shiro [Japan Atomic Energy Agency (JAEA); Shiba, K. [Japan Atomic Energy Agency (JAEA); Kurtz, Richard [Pacific Northwest National Laboratory (PNNL); Moeslang, A. [Forschungszentrum Karlsruhe, Karlsruhe, Germany; Lindau, R. [Forschungszentrum Karlsruhe, Karlsruhe, Germany

    2011-01-01

    The status and key issues of reduced activation ferritic/martensitic (RAFM) steels R&D are reviewed as the primary candidate structural material for fusion energy demonstration reactor blankets. This includes manufacturing technology, the as-fabricated and irradiates material database and joining technologies. The review indicated that the manufacturing technology, joining technology and database accumulation including irradiation data are ready for initial design activity, and also identifies various issues that remain to be solved for engineering design activity and qualification of the material for international fusion material irradiation facility (IFMIF) irradiation experiments that will validate the data base.

  10. Convoluted dislocation loops induced by helium irradiation in reduced-activation martensitic steel and their impact on mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yao, Z. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, Canada K7L 3N6 (Canada); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Suo, Jinping [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wen, Yongming [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2014-06-01

    Helium irradiation induced dislocation loops in reduced-activation martensitic steels were investigated using transmission electron microscopy. The specimens were irradiated with 100 keV helium ions to 0.8 dpa at 350 °C. Unexpectedly, very large dislocation loops were found, significantly larger than that induced by other types of irradiations under the same dose. Moreover, the large loops were convoluted and formed interesting flower-like shape. The large loops were determined as interstitial type. Loops with the Burgers vectors of b=〈100〉 were only observed. Furthermore, irradiation induced hardening caused by these large loops was observed using the nano-indentation technique.

  11. Surface modification of low activation ferritic–martensitic steel EK-181 (Rusfer) by high temperature pulsed plasma flows

    Energy Technology Data Exchange (ETDEWEB)

    Emelyanova, O.V.; Dzhumaev, P.S.; Yakushin, V.L.; Kalin, B.A.; Ganchenkova, M.G.; Khein, A.T. [National Research Nuclear University, MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Leontyeva-Smirnova, M.V. [JSC A.A. Bochvar All-Russian Scientific Research Institute for Inorganic Materials, Moscow (Russian Federation); Valiev, R.Z.; Enikeev, N.A. [Ufa State Aviation Technical University, Ufa (Russian Federation); Shao, L.; Aydogan, E. [Texas A& M University, College Station, TX 77840 (United States); Short, M. [Massachusetts Institute of Technology, Cambridge, MA (United States); Garner, F. [Radiation Effects Consulting, Richland, WA 99354 (United States)

    2015-12-15

    The changes due to pulsed plasma flow irradiation on the near-surface microstructure and mechanical properties of the high-chromium, ferritic–martensitic steel EK-181 (Fe16Cr12W2VTaB) have been quantified. Irradiation of EK-181 in this manner produces a microstructural gradient near the material surface, with a two dimensional nanostructured cellular surface. The microstructure and mechanical properties of the modified layer are independent of the initial microstructure and phase composition, and are strongly defined solely by parameters of the plasma flow. High thermal stability of the pulsed plasma-modified layer was explicitly demonstrated.

  12. Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel

    Institute of Scientific and Technical Information of China (English)

    Lin-qing Xu; Dan-tian Zhang; Yong-chang Liu; Bao-qun Ning; Zhi-xia Qiao; Ze-sheng Yan; Hui-jun Li

    2014-01-01

    Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili-tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi-croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for-mation of M3C (cementite) precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides (MX) along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener’s equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro-structural evolution and hardness variation, the process of tempering can be separated into three steps.

  13. Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel

    Science.gov (United States)

    Xu, Lin-qing; Zhang, Dan-tian; Liu, Yong-chang; Ning, Bao-qun; Qiao, Zhi-xia; Yan, Ze-sheng; Li, Hui-jun

    2014-05-01

    Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facilitates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the formation of M3C (cementite) precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides (MX) along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener's equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro-structural evolution and hardness variation, the process of tempering can be separated into three steps.

  14. Production and preliminary characterization of ferritic-martensitic steel T91 cladding tubes for LBE or Pb cooled nuclear systems

    Science.gov (United States)

    Van den Bosch, J.; Almazouzi, A.; Mueller, G.; Rusanov, A.

    2011-08-01

    Thin wall tubes with suitable dimensions for possible future use as nuclear fuel cladding based on ferritic-martensitic steel T91 have been produced. Several rolling routes for thin wall tube rolling have been successfully explored to produce T91 tubes of 8.5 mm OD and 0.5 mm wall thickness as well as 6.5 mm OD and 0.5 mm wall thickness. The results show that the cold rolled Т91 steel thin walled tubes remain ductile and the material easily carries fractional strains. Finally the microstructure of the resulting tubes was examined and preliminary burst and tensile tests were performed showing properties comparable to those of T91 plate material.

  15. Anti-Corrosion Performance of 1,3-BENZOTHIAZOLE on 410 Martensitic Stainless Steel in H2SO4

    Science.gov (United States)

    Loto, Roland Tolulope

    The corrosion inhibition effect of synthesized 1,3-benzothiazole at very low concentrations on 410 martensitic stainless steel in 3MH2SO4 solution was studied through potentiodynamic polarization and weight loss measurements. The observation showed that the organic compound performed effectively with average inhibition efficiencies of 94% and 98% at the concentrations studied from both electrochemical methods due to the inhibition action of protonated inhibitor molecules in the acid solution. The amine and aromatics functional groups of the molecules active in the corrosion inhibition reaction were exposed from Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopic analysis. Thermodynamic calculations showed cationic adsorption to be chemisorption adsorption, obeying the Langmuir adsorption isotherm. Images from optical microscopy showed an improved morphology in comparison to images from corroded stainless steel. Severe surface deterioration and macro-pits were observed in the uninhibited samples.

  16. Thermal Diffusivity of Reduced Activation Ferritic/Martensitic Steel Determined by the Time Domain Photoacoustic Piezoelectric Technique

    Science.gov (United States)

    Zhao, Binxing; Wang, Yafei; Gao, Chunming; Sun, Qiming; Wang, Pinghuai

    2015-06-01

    The thermal diffusivity of reduced activation ferritic/martensitic steel (CLF-1), which is recognized as the primary candidate structural material for the test blanket module of the international thermal-nuclear experimental reactor, has been studied by the time-domain (TD) photoacoustic piezoelectric (PAPE) technique. The TD PAPE model based on a simplified thermoelastic theory under square-wave modulated laser excitation is presented, relating the TD PAPE signal to the modulation frequency, thermal diffusivity, and other material parameters. Thermal diffusivities of reference samples such as copper and nickel were measured and analyzed, by which the validity of the technique is verified. The thermal diffusivity of the CLF-1 sample was measured to be , which is at a medium level among the ordinary steel materials ( to and has decent heat-dissipation ability. The results show that the TD PAPE technique can provide a fast and economic way for the investigation of the thermophysical properties of fusion reactor structural materials.

  17. Creep fracture behavior of dissimilar weld joints between T92 martensitic and HR3C austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Cao Jian; Gong Yi [Department of Materials Science, Fudan University, Shanghai 200433 (China); Yang Zhenguo, E-mail: zgyang@fudan.edu.c [Department of Materials Science, Fudan University, Shanghai 200433 (China); Luo Xiaoming; Gu Fuming [Shanghai Institute of Special Equipment Inspection and Technical Research, Shanghai 200062 (China); Hu Zhengfei [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)

    2011-02-15

    The creep fracture of T92/HR3C dissimilar weld joints is investigated. HR3C austenitic steel is welded with T92 martensitic steel to obtain a T92/HR3C weld joint. After welding, creep tests are carried out at 625 {sup o}C in the stress range 110-180 MPa. The results indicate that the creep fracture mechanism is dependent on stress. When stresses {>=}140 MPa, the fracture location is at the T92 base material and the connection of adjacent dimples results in transcrystalline fracture. For stresses <140 MPa, the fracture location is at the T92 coarse-grained heat affected zone and growth of M{sub 23}C{sub 6} particles as well as Laves phase (Fe{sub 2}(W, Mo)) precipitation on the grain boundaries leads to intergranular fracture.

  18. Evolution of the mechanical properties and microstructure of ferritic-martensitic steels irradiated in the BOR-60 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Shamardin, V.K. E-mail: fae@niiar.ru; Golovanov, V.N.; Bulanova, T.M.; Povstyanko, A.V.; Fedoseev, A.E.; Ostrovsky, Z.E.; Goncharenko, Yu.D

    2002-12-01

    The effect of neutron irradiation on mechanical properties of low-activation ferritic-martensitic (FM) steels 0.1C-9Cr-1W, V, Ta, B and 0.1C-12Cr-2W, V, Ti, B is studied under tension at temperatures of 330-540 deg. C and doses of 50 dpa. Steel 0.1C-13Cr-Mo, V, Nb, B was chosen for comparison. At irradiation temperatures of 330-340 deg. C, the radiation hardening of steel with 9%Cr achieves saturation at a dose of 10 dpa. In this case as compared to steels with 12%Cr, the fracture surface is characterized as ductile without cleavage traces. At irradiation temperatures higher than 420 deg. C, there is no difference in the behavior of the materials under investigation. The data on radiation creep obtained by direct measurement and from the profilometry data satisfy a model {epsilon}-bar/{sigma}-bar=B{sub 0}+DS, when B{sub 0} and D have the values typical for steels of FM type.

  19. Evolution of the mechanical properties and microstructure of ferritic-martensitic steels irradiated in the BOR-60 reactor

    Science.gov (United States)

    Shamardin, V. K.; Golovanov, V. N.; Bulanova, T. M.; Povstyanko, A. V.; Fedoseev, A. E.; Ostrovsky, Z. E.; Goncharenko, Yu. D.

    2002-12-01

    The effect of neutron irradiation on mechanical properties of low-activation ferritic-martensitic (FM) steels 0.1C-9Cr-1W, V, Ta, B and 0.1C-12Cr-2W, V, Ti, B is studied under tension at temperatures of 330-540 °C and doses of 50 dpa. Steel 0.1C-13Cr-Mo, V, Nb, B was chosen for comparison. At irradiation temperatures of 330-340 °C, the radiation hardening of steel with 9%Cr achieves saturation at a dose of 10 dpa. In this case as compared to steels with 12%Cr, the fracture surface is characterized as ductile without cleavage traces. At irradiation temperatures higher than 420 °C, there is no difference in the behavior of the materials under investigation. The data on radiation creep obtained by direct measurement and from the profilometry data satisfy a model ɛ¯/ σ¯=B 0+D Ṡ, when B0 and D have the values typical for steels of FM type.

  20. Influence of rapid heating process on the microstructure and tensile properties of high-strength ferrite-martensite dual-phase steel

    Institute of Scientific and Technical Information of China (English)

    Pei Li; Jun Li; Qing-ge Meng; Wen-bin Hu; Chun-fu Kuang

    2015-01-01

    Three low-carbon dual-phase (DP) steels with almost constant martensite contents of 20vol%were produced by intercritical an-nealing at different heating rates and soaking temperatures. Microstructures prepared at low temperature (1043 K, FH1) with fast-heating (300 K/s) show banded ferrite/martensite structure, whereas those soaked at high temperature (1103 K, FH2) with fast heating reveal blocky martensite uniformly distributed in the fine-grained ferrite matrix. Their mechanical properties were tested under tensile conditions and compared to a slow-heated (5 K/s) reference material (SH0). The tensile tests indicate that for a given martensite volume fraction, the yield strength and total elongation values are noticeably affected by the refinement of ferrite grains and the martensite morphology. Metallographic observations reveal the formation of microvoids at the ferrite/martensite interface in the SH0 and FH2 samples, whereas microvoids nucleate via the fracture of banded martensite particles in the FH1 specimen. In addition, analyses of the work-hardening behaviors of the DP micro-structures using the differential Crussard–Jaoul technique demonstrate two stages of work hardening for all samples.

  1. Martensite phase reversion-induced nano/ ultrafine grained AISI 304L stainless steel with magnificent mechanical properties

    Directory of Open Access Journals (Sweden)

    Mohammad Shirdel

    2015-06-01

    Full Text Available Austenitic stainless steels are extensively used in various applications requiring good corrosion resistance and formability. In the current study, the formation of nano/ ultrafine grained austenitic microstructure in a microalloyed AISI 304L stainless steel was investigated by the advanced thermomechanical process of reversion of strain-induced martensite. For this purpose, samples were subjected to heavy cold rolling to produce a nearly complete martensitic structure. Subsequently, a wide range of annealing temperatures (600 to 800°C and times (1 to 240 min were employed to assess the reversion behavior and to find the best annealing condition for the production of the nano/ultrafine grained austenitic microstructure. Microstructural characterizations have been performed using X-ray diffraction (XRD, scanning electron microscopy (SEM, and magnetic measurement, whereas the mechanical properties were assessed by tensile and hardness tests. After thermomechanical treatment, a very fine austenitic structure was obtained, which was composed of nano sized grains of ~ 85 nm in an ultrafine grained matrix with an average grain size of 480 nm. This microstructure exhibited superior mechanical properties: high tensile strength of about 1280 MPa with a desirable elongation of about 41%, which can pave the way for the application of these sheets in the automotive industry.

  2. Microstructure Evolution in an Advanced 9 pct Cr Martensitic Steel during Creep at 923 K (650 °C)

    Science.gov (United States)

    Fedorova, Irina; Kipelova, Alla; Belyakov, Andrey; Kaibyshev, Rustam

    2013-01-01

    Crept microstructures were examined in a 9 pct Cr martensitic steel with low carbon content. The steel was hot forged at 1323 K (1050 °C) followed by air cooling and then tempered at 1023 K (750 °C) for 3 hours. The tempered microstructure included numerous precipitates of MX-type carbonitrides and a small amount of M23C6-type carbides. Two groups of the MX-type particles were observed. The nanoscale MX-type precipitates appeared in the form of plate- and round-shaped particles. The plate-shaped MX-type particles were approximately 15 nm in the longitudinal direction and approximately 3 nm in thickness, and the round-shaped MX-type particles were 10 nm in diameter. In addition to the fine particles, the tempered martensite contained relatively coarse MX-type particles, which have a size of approximately 90 nm. The structural changes that occurred during the creep test were associated with an increase in the sizes of the lath and second-phase particles. Moreover, the creep was accompanied by appearance of Laves and Z-phase particles.

  3. Effects of strain-induced martensite and its reversion on the magnetic properties of AISI 201 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Souza Filho, I.R. [Escola de Engenharia de Lorena, University of Sao Paulo, 12602-810 Lorena (Brazil); Sandim, M.J.R., E-mail: msandim@demar.eel.usp.br [Escola de Engenharia de Lorena, University of Sao Paulo, 12602-810 Lorena (Brazil); Cohen, R.; Nagamine, L.C.C.M. [Instituto de Física, University of Sao Paulo, 05314-970 Sao Paulo (Brazil); Hoffmann, J. [Karlsruher Institut für Technologie, D-72061 Karlsruhe (Germany); Bolmaro, R.E. [Instituto de Física Rosario, CONICET-UNR, 2000 Rosario (Argentina); Sandim, H.R.Z. [Escola de Engenharia de Lorena, University of Sao Paulo, 12602-810 Lorena (Brazil)

    2016-12-01

    Strain-induced martensite (SIM) and its reversion in a cold-rolled AISI 201 austenitic stainless steel was studied by means of magnetic properties, light optical (LOM) and scanning electron (SEM) microscopy, electron backscatter diffraction (EBSD), texture measurements, and Vickers microhardness testing. According to Thermo-calc© predictions, the BCC phase (residual δ-ferrite and SIM) is expected to be stable until 600 °C. The current material was cold rolled up to 60% thickness reduction and submitted to both isothermal and stepwise annealing up to 800 °C. Magnetic measurements were taken during annealing (in situ) of the samples and also for their post mortem conditions. The Curie temperatures (T{sub c}) of residual δ-ferrite and SIM have similar values between 550 and 600 °C. Besides T{sub c}, the focused magnetic parameters were saturation magnetization (M{sub s}), remanent magnetization (M{sub R}), and coercive field (H{sub c}). SIM reversion was found to occur in the range of 600–700 °C in good agreement with Thermo-calc© predictions. The microstructures of the material, annealed at 600 and 700 °C for 1 h, were investigated via EBSD. Microtexture measurements for these samples revealed that the texture components were mainly those found for the 60% cold rolled material. This is an evidence that the SIM reversion occurred by an athermal mechanism. - Highlights: • H{sub c} and M{sub R}/M{sub S} ratio give information about distribution of strain-induced martensite. • According to Thermo-calc©, the BCC phase in AISI 201 steel is stable until 600 °C. • Thermo-calc predictions agrees with magnetic properties of AISI 201 steel. • Possible magnetic anisotropy induced by rolling in AISI 201 steel is investigated.

  4. Oxidation behavior of ferritic-martensitic and ODS steels in supercritical water

    Science.gov (United States)

    Bischoff, Jeremy

    water corroded much faster than those in steam (1.5 to 2 times faster). Additionally, during these corrosion tests a marker experiment was performed with the deposition of micrometric palladium markers on the surface of some samples prior to oxidation. The markers were found at the outer-inner layer interface, consistent with a corrosion mechanism of outward migration of iron to form the outer layer and inward migration of oxygen to form the inner layer. The discrepancy between the SCW and steam environments suggests that the outward migration of iron may be the rate-limiting step. A detailed study of the oxide advancement was performed using the TEM by analyzing the inner and diffusion layer structure. Energy-filtered TEM images were acquired to analyze the micrometric and nanometric distribution of elements in these layers. Such images from the inner layer revealed the presence of localized chromium enrichment regions associated with the presence of pores. Additionally, an iron-chromium nanometric segregation was observed and may be associated with the mixture of Fe3O4 and FeCr2O4. In the diffusion layer, small nanometric chromium-rich oxide particles were seen within metal grains. The (Fe,Cr)3O4 spinel oxide has an inverse spinel structure as Fe3O4 but becomes normal spinel as FeCr 2O4, thus the structure changes depending on the chromium content. Additionally, the spinel structure was analyzed using the ligand theory and showed that chromium does not migrate and that the main diffusing species is the Fe2+ ion. Calculations of the amount of iron leaving the inner layer showed that this amount accounted for the amount of iron necessary to form the outer layer, thus no dissolution of oxide in SCW is observed. Additionally, the differences in oxidation behavior in steam and SCW suggest that the rate-limiting step for the corrosion of ferritic-martensitic steels is the iron outward migration. The iron migration is driven by the gradient in the Fe2+/Fe 3+ ratio and is

  5. Isothermal Martensite Formation

    DEFF Research Database (Denmark)

    Villa, Matteo

    Isothermal (i.e. time dependent) martensite formation in steel was first observed in the 40ies of the XXth century and is still treated as an anomaly in the description of martensite formation which is considered as a-thermal (i.e. independent of time). Recently, the clarification of the mechanis...

  6. Softening and hardening by. gamma. yields. epsilon. martensitic transformation during deformation in high Mn steels. Ko Mn tetsu gokin ni okeru. gamma. yields. epsilon. martensite hentai ni yoru nanka to koka

    Energy Technology Data Exchange (ETDEWEB)

    Tomota, Y.; Ryufuku, S.; Piao, M. (Ibaraki University, Ibaraki (Japan). Faculty of Engineering)

    1991-01-15

    In high Mn steel, martensitic transformation of gamma to epsilon occurs under the ordinary pressure. Its application comprises utilization of its configuration memory properties and high work hardening characteristics. The present report studied, by using Fe-Mn type alloy, added with Si or Co, the influence of martensitic transformation of gamma to epsilon on the deformation behavior. Tensile test, 2mm/min in speed, being made on molten/cast alloy ingot, thermally treated as specified, epsilon was quantitatively analyzed by X-ray diffraction. The above test/analysis pointed out many notes in result and knowledge, as follows among others: The addition with Si or Co, lowering the Neel temperature, quantitatively increases the epsilon martensite, produced by the processing. The produced quantity of epsilon martensite in case of addition with Si is small, as compared with that in case of two-element Fe-Mn type alloy without addition and in case of addition with Co. All the tested alloys give the softening phenomenon by the martensitic transformation of gamma to epsilon. The pre-existing epsilon plate is a strong barrier for the further plastic flow, which accordingly accelerates the work hardening. 20 refs., 10 figs., 1 tab.

  7. Microstructural evolution of ferritic-martensitic steels under heavy ion irradiation

    Science.gov (United States)

    Topbasi, Cem

    Ferritic-martensitic steels are primary candidate materials for fuel cladding and internal applications in the Sodium Fast Reactor, as well as first-wall and blanket materials in future fusion concepts because of their favorable mechanical properties and resistance to radiation damage. Since microstructure evolution under irradiation is amongst the key issues for these materials in these applications, developing a fundamental understanding of the irradiation-induced microstructure in these alloys is crucial in modeling and designing new alloys with improved properties. The goal of this project was to investigate the evolution of microstructure of two commercial ferritic-martensitic steels, NF616 and HCM12A, under heavy ion irradiation at a broad temperature range. An in situ heavy ion irradiation technique was used to create irradiation damage in the alloy; while it was being examined in a transmission electron microscope. Electron-transparent samples of NF616 and HCM12A were irradiated in situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with 1 MeV Kr ions to ˜10 dpa at temperatures ranging from 20 to 773 K. The microstructure evolution of NF616 and HCM12A was followed in situ by systematically recording micrographs and diffraction patterns as well as capturing videos during irradiation. In these irradiations, there was a period during which no changes are visible in the microstructure. After a threshold dose (˜0.1 dpa between 20 and 573 K, and ˜2.5 dpa at 673 K) black dots started to become visible under the ion beam. These black dots appeared suddenly (from one frame to the next) and are thought to be small defect clusters (2-5 nm in diameter), possibly small dislocation loops with Burgers vectors of either ½ or . The overall density of these defect clusters increased with dose and saturated around 6 dpa. At saturation, a steady-state is reached in which defects are eliminated and created at the same rates so that the

  8. Effects of Vacuum-Carburizing Conditions on Surface-Hardened Layer Properties of Transformation-Induced Plasticity-Aided Martensitic Steel

    Directory of Open Access Journals (Sweden)

    Koh-ichi Sugimoto

    2017-08-01

    Full Text Available The effects of carbon potential in vacuum-carburization on the surface-hardened layer properties of the 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb transformation-induced plasticity-aided martensitic steel were investigated for the fabrication of precision gears. The volume fraction of retained austenite and hardness in the surface hardened layer of the steel increased with increasing carbon potential. Subsequent fine-particle peening enhanced the hardness and the compressive residual stress via severe plastic deformation and strain-induced martensite transformation, especially under a high carbon potential. The severe plastic deformation mainly contributed to increased hardness and compressive residual stress and the contribution of the strain-induced martensitic transformation was relatively small.

  9. An acoustic emission study of martensitic and bainitic transformations in carbon steel

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.

    2004-01-01

    Steel is one of the most commonly used materials today, especially in industrial sectors such as ship building and the automotive industry. In order to meet the requirements for steel applications, new multi-phase steels are being developed. The microstructure of these steels consists of a variety

  10. Effects of Ti element on the microstructural stability of 9Cr–WVTiN reduced activation martensitic steel under ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Jin, Shuoxue; Li, Tiecheng; Chen, Jihong [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Suo, Jinping; Yang, Feng [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Yao, Z. [Department of Mechanical and Materials Engineering, Queen’s University, Kingston K7L 3N6, ON (Canada)

    2014-12-15

    Microstructure of 9Cr–WVTiN reduced-activation martensitic steels with two different Ti concentrations irradiated with Fe{sup +}, He{sup +} and H{sup +} at 300 °C was studied with transmission electron microscopy. Small dislocation loops were observed in the irradiated steels. The mean size and number density of dislocation loops decreased with the increase of Ti concentration. The segregation of Cr and Fe in carbides was observed in both irradiated steels, and the enrichment of Cr and depletion of Fe were more severe in the low Ti-concentration 9Cr–WVTiN steel.

  11. Microstructural characterization of weld joints of 9Cr reduced activation ferritic martensitic steel fabricated by different joining methods

    Energy Technology Data Exchange (ETDEWEB)

    Thomas Paul, V.; Saroja, S.; Albert, S.K.; Jayakumar, T.; Rajendra Kumar, E., E-mail: vtp@igcar.gov.in

    2014-10-15

    This paper presents a detailed electron microscopy study on the microstructure of various regions of weldment fabricated by three welding methods namely tungsten inert gas welding, electron beam welding and laser beam welding in an indigenously developed 9Cr reduced activation ferritic/martensitic steel. Electron back scatter diffraction studies showed a random micro-texture in all the three welds. Microstructural changes during thermal exposures were studied and corroborated with hardness and optimized conditions for the post weld heat treatment have been identified for this steel. Hollomon–Jaffe parameter has been used to estimate the extent of tempering. The activation energy for the tempering process has been evaluated and found to be corresponding to interstitial diffusion of carbon in ferrite matrix. The type and microchemistry of secondary phases in different regions of the weldment have been identified by analytical transmission electron microscopy. - Highlights: • Comparison of microstructural parameters in TIG, electron beam and laser welds of RAFM steel • EBSD studies to illustrate the absence of preferred orientation and identification of prior austenite grain size using phase identification map • Optimization of PWHT conditions for indigenous RAFM steel • Study of kinetics of tempering and estimation of apparent activation energy of the process.

  12. Design and Analysis of HIP joined W and Ferritic-Martensitic Steel Mockup for Fusion Reactor Divertor Development

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D. W.; Shin, K. I.; Kim, S. K.; Jin, H. G.; Lee, E. H.; Yoon, J. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Moon, S. Y.; Hong, B. G. [Chonbuk National Univ., Jeonju (Korea, Republic of)

    2013-10-15

    Korea has developed a Helium Cooled Ceramic Reflector (HCCR) based Test Blanket System (TBS) for an ITER, which consists of the First Wall (FW), Breeding Zone (BZ), Side Wall (SW), and BZ box. Among them, the FW is an important component which faces the plasma directly and, therefore, it is subjected to high heat and neutron loads. The FW of the TBM is considered to be composed of a beryllium (Be) armor as a plasma-facing material and Ferritic-Martensitic (FM) steel as a structure material, or a tungsten (W) armor and FM steel, or bare FM steel. Since Be/FMS and bare FMS were developed and proved by high heat flux (HHF) test, W armor and FM steel joining, fabricated mock-ups, and preparation of the high heat flux (HHF) test for integrity investigation are introduced in the present study. For the application to fusion reactor, joining methods with W to FMS has been developed. The W mock-up was fabricated with HIP considering Ti interlayer and PHHT condition. And the HHF test was prepared by performing the preliminary analysis to determine the test conditions. From the analysis heating and cooling conditions were determined for 0.5 and 1.0 MW/m2 heat fluxes. In the near future, the thermal life-time will be evaluated to determine the test period of the mockups by the mechanical analysis with ANSYS.

  13. Toughness evolution of 9Cr–3W–3Co martensitic heat resistant steel during long time aging

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Peng, E-mail: maxeric@163.com [School of Materials Science and Engineering, Tsinghua University, Beijing (China); Institute for Special Steels, China Iron and Steel Research Institute, Beijing 100081 (China); Liu, Zhengdong [Institute for Special Steels, China Iron and Steel Research Institute, Beijing 100081 (China)

    2016-01-05

    Toughness of G115 martensitic heat resistant steel after heat treatment and aging for different time at 650 °C was tested at room temperature. The corresponding microstructure was also experimentally obtained by field emission scanning electron microscope (FESEM), field emission transmission electron microscope (FETEM), X-Ray diffraction (XRD), electron back-scattered diffraction (EBSD) characterization and phase analysis. The results show that the absorbed energy of G115 steel can reach 115 J after heat treatment. After the first 300 h aging, the absorbed energy decreases drastically to just 36 J and then keeps almost stable with further increasing aging time to 8000 h. The hardness of base metal and the amount of large angle (LA) boundaries (>15°) are not the main factors dominating the toughness of G115 steel during aging process. The main reason for the change of toughness can be attributed to the precipitation of Laves phase. Since Laves phase particles are large, angular and hard, it is difficult for them to harmonize with the matrix during deformation, resulting that the crack initiation and propagation become easy and then the toughness of the steel sharply decreases. The reason why the toughness keeps nearly stable from 300 h to 8000 h can be attributed to that the negative effect of the precipitation of Laves phase and the decrease of LA boundaries is counteracted by the positive effect of the softening of metal matrix.

  14. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    Science.gov (United States)

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

    2017-02-01

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

  15. Sub-Zero Celsius treatment: a promising option for future martensitic stainless steels

    DEFF Research Database (Denmark)

    Villa, Matteo; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2016-01-01

    and Vickers micro-hardness indentation.Complementary electron back-scatter diffraction was appliedfor determining the phase fractions of austenite and martensite.Data shows that sub-zero Celsius treatment yields anadditional hardening response when austenite is retained in thematerial. The relevance...

  16. Effect of Carbon Content on Microstructure and Mechanical Properties of 9 to 12 pct Cr Ferritic/Martensitic Heat-Resistant Steels

    Science.gov (United States)

    Yin, Feng-Shi; Tian, Li-Qian; Xue, Bing; Jiang, Xue-Bo; Zhou, Li

    2012-07-01

    Two heats of 9 to 12 pct Cr ferritic/martensitic heat-resistant steels were prepared. One has an ultralow carbon content of 0.01 wt pct, whereas another heat has a normal carbon content of 0.09 wt pct. The effect of carbon content on microstructure and mechanical properties of 9 to 12 pct Cr ferritic/martensitic heat-resistant steels was studied. The results show that the ultralow-carbon steel contains bimodal, nanosized MX precipitates with high density in the matrix but few M23C6 carbide particles in the normalized-and-tempered state. The smaller nanosized MX precipitates have two kinds of typical morphology: One is cubic and another is rectangular. The cubic MX precipitate contains Nb, Ti, and V, whereas the rectangular one only contains Nb and V. The normal carbon steel has abundant M23C6 carbide particles along the grain and lath boundaries and much less density of nanosized MX precipitates after the same heat treatments. After long-term aging at 923 K (650 °C) for 10,000 hours, the stress rupture properties of the ultralow carbon content steel degrades more significantly. The strength degradation mechanism of the 9 to 12 pct Cr ferritic/martensitic heat-resistant steels is discussed in this article.

  17. Anelastic effects connected with isothermal martensitic transformations in 24Ni4Mo austenitic and 12Cr9Ni4Mo maraging steels

    Energy Technology Data Exchange (ETDEWEB)

    Golovin, I.S. [Russian State Technol. Univ., Moscow (Russian Federation). Dept. of Mater.; Nilsson, J.-O. [Department of Physical Metallurgy, Steel Research and Development, AB Sandvik Steel, S-811 81, Sandviken (Sweden); Serzhantova, G.V.; Golovin, S.A. [Department of Physical Metallurgy, Tula State University, Lenin av. 90, 300600, Tula (Russian Federation)

    2000-09-28

    Anelasticity of the austenitic steel 24Ni5Mo and the stainless steel 12Cr9Ni4Mo has been investigated in the austenitic state after quenching with respect to isothermal martensitic transformation during cooling and subsequent heating. Maxima of anelasticity due to isothermal transformation at {approx}200 K (24Ni5Mo, 0.002% C) and {approx}250 K (12Cr9Ni4Mo; 0.01% C) coincided well with C-curve noses obtained by methods based on magnetic properties and electric resistivity. Corresponding internal friction maxima were found to be dependent on cooling or heating rate, quenching temperature and the frequency of oscillation and may therefore be described using the Delorme approximation. The activation energy of isothermal martensitic transformation calculated from the lower part of the C-curves estimated using the Borgenstam-Hillert and Arrhenius methods (3-8 kJ/mol for 24Ni5Mo and 15-20 kJ/mol for 12Cr9Ni4Mo) are comparable with the energy of impurity-dislocation interaction ({approx}10 kJ/mol) and interpreted as too low to be caused by diffusion processes: the activation energy for carbon diffusion in austenitic steel 24Ni5Mo is found to be {approx}135 kJ/mol and {approx}145 kJ/mol for austenite in two-phase 12Cr9Ni4Mo steel. An estimation showed that the activation energy for the isothermal martensitic transformation for the 24Ni5Mo alloy with so-called binary martensitic kinetics was higher in the vicinity of the nose of the C-curve, became lower with a decrease in temperature range and approached zero in the vicinity of the athermal martensitic point. A similar effect was not observed in the 12Cr9Ni4Mo steel. (orig.)

  18. Effect of the bainitic and martensitic microstructures on the hardening and embrittlement under neutron irradiation of a reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Marini, B., E-mail: bernard.marini@cea.fr [Commissariat à l' Energie Atomique et aux Energies Alternatives, DEN/DANS/DMN/SRMA, F-91191 Gif-sur Yvette (France); Averty, X. [Commissariat à l' Energie Atomique et aux Energies Alternatives, DEN/DANS/DMN/SEMI (now DEN/DANS/DM2S/SEMT), F-91191 Gif-sur Yvette (France); Wident, P.; Forget, P.; Barcelo, F. [Commissariat à l' Energie Atomique et aux Energies Alternatives, DEN/DANS/DMN/SRMA, F-91191 Gif-sur Yvette (France)

    2015-10-15

    The hardening and the embrittlement under neutron irradiation of an A508 type RPV steel considering three different microstructures (bainite, bainite-martensite and martensite)have been investigated These microstructures were obtained by quenching after autenitization at 1100 °C. The irradiation induced hardening appears to depend on microstructure and is correlated to the yield stress before irradiation. The irradiation induced embrittlement shows a more complex dependence. Martensite bearing microstructures are more sensitive to non hardening embrittlement than pure bainite. This enhanced sensitivity is associated with the development of intergranular brittle facture after irradiation; the pure martensite being more affected than the bainite-martensite. It is of interest to note that this mixed microstructure appears to be more embrittled than the pure bainitic or martensitic phases in terms of temperature transition shift. This behaviour which could emerge from the synergy of the embrittlement mechanisms of the two phases needs further investigations. However, the role of microstructure on brittle intergranular fracture development appears to be qualitatively similar under neutron irradiation and thermal ageing.

  19. Microstructure, Mechanical and Corrosion Properties of Friction Stir Welding High Nitrogen Martensitic Stainless Steel 30Cr15Mo1N

    Directory of Open Access Journals (Sweden)

    Xin Geng

    2016-11-01

    Full Text Available High nitrogen martensitic stainless steel 30Cr15Mo1N plates were successfully welded by friction stir welding (FSW at a tool rotation speed of 300 rpm with a welding speed of 100 mm/min, using W-Re tool. The sound joint with no significant nitrogen loss was successfully produced. Microstructure, mechanical and corrosion properties of an FSW joint were investigated. The results suggest that the grain size of the stir zone (SZ is larger than the base metal (BM and is much larger the case in SZ-top. Some carbides and nitrides rich in chromium were found in BM while not observed in SZ. The martensitic phase in SZ could transform to austenite phase during the FSW process and the higher peak temperature, the greater degree of transformation. The hardness of SZ is significantly lower than that of the BM. An abrupt change of hardness defined as hard zone (HZ was found in the thermo-mechanically affected zone (TMAZ on the advancing side (AS, and the HZ is attributed to a combination result of temperature, deformation, and material flow behavior. The corrosion resistance of SZ is superior to that of BM, which can be attributed to less precipitation and lower angle boundaries (LABs. The corrosion resistance of SZ-bottom is slight higher than that of SZ-top because of the finer grained structure.

  20. Mechanical properties of 9Cr–1W reduced activation ferritic martensitic steel weldment prepared by electron beam welding process

    Energy Technology Data Exchange (ETDEWEB)

    Das, C.R., E-mail: chitta@igcar.gov.in [Indira Gandhi Center for Atomic Research, Kalpakkam 603102 (India); Albert, S.K. [Indira Gandhi Center for Atomic Research, Kalpakkam 603102 (India); Sam, Shiju [Institute for Plasma Research, Gandhinagar (India); Mastanaiah, P. [Defense Research and Development Laboratory, Hyderabad (India); Chaitanya, G.M.S.K.; Bhaduri, A.K.; Jayakumar, T. [Indira Gandhi Center for Atomic Research, Kalpakkam 603102 (India); Murthy, C.V.S. [Defense Research and Development Laboratory, Hyderabad (India); Kumar, E. Rajendra [Institute for Plasma Research, Gandhinagar (India)

    2014-11-15

    Highlights: • Width of HAZ is smaller in the 9Cr–1W RAFM weldment prepared by EB process compared to that reported for TIG weldments in literature. • Weld joint is stronger than that of the base metal. • Toughness of weld metal prepared by EB welding process is comparable to that (in PWHT condition) prepared by TIG process. • DBTT of as-welded 9Cr–1W RAFM weldment prepared by EB process is comparable to that reported for TIG weld metal in PWHT condition. - Abstract: Microstructure and mechanical properties of the weldments prepared from 9Cr–1W reduced activation ferritic martensitic (RAFM) steel using electron beam welding (EBW) process were studied. Microstructure consists of tempered lath martensite where precipitates decorating the boundaries in post weld heat treated (PWHT) condition. Lath and precipitate sizes were found to be finer in the weld metal than in base metal. Accordingly, hardness of the weld metal was found to be higher than the base metal. Tensile strength of the cross weldment specimen was 684 MPa, which was comparable with the base metal tensile strength of 670 MPa. On the other hand, DBTT of 9Cr–1W weld metal in as-welded condition is similar to that reported for TIG weld metal in PWHT condition.

  1. Effects of Rare Earth Elements on the Characteristics of,Low Temperature Plasma Nitrocarburized Martensitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    R.L.Lju; Y.J. Qiao; M.F. Yan; Y.D. Fu

    2012-01-01

    Low temperature plasma nitrocarburizing of 17-4PH martensitic stainless steel was conducted at 430 ℃ with and without rare earth (RE) addition. The microstructure, kinetics, microhardness, wear behavior as well as corrosion resistance of the modified layer were studied by optical microscopy, X-ray diffraction, Vickers microhardness tester, pin-on-disc tribometer and potentiodynamic polarization tests. The results show that the thickness of plasma RE nitrocarburized layer is much thicker than that formed by nitrocarburizing without RE addition. The incorporation of RE does not change the kind of the phases and the nitrocarburized layer consists mainly of nitrogen and carbon expanded martensite (aN), γ-Fe4N and a-Fe with a trace of CrN phases. The surface microhardness of plasma nitrocarburized layer can be increased by 100 HV after RE addition. Wear resistance of the specimen can be apparently improved by low temperature plasma nitrocarburizing with and without RE addition and without sacrificing its corrosion resistance. Wear reduction effect of low temperature plasma nitrocarburizing with RE addition is better than that of the conventional one.

  2. Patent Analysis of Ferritic/Martensitic Steels for the Fuel Cladding in Sodium-cooled Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jong Hyuk; Kim, Sung Ho; Kim, Tae Kyu; Kim, Woo Gon; Jang, Jin Sung; Kim, Dae Whan; Han, Chang Hee; Lee, Chan Bock

    2007-09-15

    The Korean, Japanese, U.S. and European patents related to the ferritic/martensitic steels were systematically surveyed to evaluate their patent status, which would be applicable to the fuel cladding materials for the Sodium-cooled Fast Reactor (SFR). From the surveys, totally 38 patents were finally selected for the quantitative and qualitative analysis. Among them, 28 patents (74%) were processed by Japanese companies and Sumitomo Metal industries Ltd. was top-ranked in the number (9) of priority patents. On the basis of these surveys, most patents could be applicable to the fuel cladding materials for SFR and, especially, some useful patents as the cladding were registered by the Russian and the Korean.

  3. Role of quaternary additions on dislocated martensite, retain austenite and mechanical properties of Fe/Cr/C structural steels

    Energy Technology Data Exchange (ETDEWEB)

    Rao, B.V.N.

    1978-02-01

    The influence of quaternary alloy additions of Mn and Ni to Fe/Cr/C steels which have been designed to provide superior mechanical properties has been investigated. Transmission electron microscopy and x-ray analysis revealed increasing amounts of retained austenite with Mn up to 2 w/o and with 5 w/o Ni additions after quenching from 1100/sup 0/C. This is accompanied by a corresponding improvement in toughness properties of the quaternary alloys. In addition, the generally attractive combinations of strength and toughness in these quaternary alloys is attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. Grain-refining resulted in a further increase in the amount of retained austenite.

  4. Orientation dependence of variant selection and intersection reactions of ɛ martensite in a high-manganese austenitic steel

    Science.gov (United States)

    Zhang, X.; Sawaguchi, T.; Ogawa, K.; Yin, F.; Zhao, X.

    2011-09-01

    The orientation dependence of ɛ martensite during loading of a polycrystalline austenitic Fe-30Mn-4Si-2Al steel has been investigated by electron backscatter diffraction, emphasising the variant selection rule and plate-plate intersection reactions. Two types of plate-plate intersection reactions, which are characterised by incident shear direction of either 30° or 90° with respect to the intersection axis, were found in the grains along the [001]-[111] directions and [001]-[101] directions, respectively. In the intersecting volume of the latter type reaction, a γ phase rotated 90° from the austenite matrix along the ⟨011⟩ zone axis of the intersecting ɛ plates, which was theoretically predicted by Sleeswyk [A.W. Sleeswyk, Philos. Mag. 7 (1962) p.1597], has been experimentally observed for the first time.

  5. Determining the shear fracture properties of HIP joints of reduced-activation ferritic/martensitic steel by a torsion test

    Science.gov (United States)

    Nozawa, Takashi; Noh, Sanghoon; Tanigawa, Hiroyasu

    2012-08-01

    Hot isostatic pressing (HIP) is a key technology used to fabricate a first wall with cooling channels for the fusion blanket system utilizing a reduced-activation ferritic/martensitic steel. To qualify the HIPped components, small specimen test techniques are beneficial not only to evaluate the thin-wall cooling channels containing the HIP joint but also to use in neutron irradiation studies. This study aims to develop the torsion test method with special emphasis on providing a reasonable and comprehensive method to determine interfacial shear properties of HIP joints during the torsional fracture process. Torsion test results identified that the torsion process shows yield of the base metal followed by non-elastic deformation due to work hardening of the base metal. By considering this work hardening issue, we propose a reasonable and realistic solution to determine the torsional yield shear stress and the ultimate torsional shear strength of the HIPped interface. Finally, a representative torsion fracture process was identified.

  6. Patent Analysis of Ferritic/Martensitic Steels for the Fuel Cladding in Sodium-cooled Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jong Hyuk; Kim, Sung Ho; Kim, Tae Kyu; Kim, Woo Gon; Jang, Jin Sung; Kim, Dae Whan; Han, Chang Hee; Lee, Chan Bock

    2007-09-15

    The Korean, Japanese, U.S. and European patents related to the ferritic/martensitic steels were systematically surveyed to evaluate their patent status, which would be applicable to the fuel cladding materials for the Sodium-cooled Fast Reactor (SFR). From the surveys, totally 38 patents were finally selected for the quantitative and qualitative analysis. Among them, 28 patents (74%) were processed by Japanese companies and Sumitomo Metal industries Ltd. was top-ranked in the number (9) of priority patents. On the basis of these surveys, most patents could be applicable to the fuel cladding materials for SFR and, especially, some useful patents as the cladding were registered by the Russian and the Korean.

  7. Microstructural Variations Across a Dissimilar 316L Austenitic: 9Cr Reduced Activation Ferritic Martensitic Steel Weld Joint

    Science.gov (United States)

    Thomas Paul, V.; Karthikeyan, T.; Dasgupta, Arup; Sudha, C.; Hajra, R. N.; Albert, S. K.; Saroja, S.; Jayakumar, T.

    2016-03-01

    This paper discuss the microstructural variations across a dissimilar weld joint between SS316 and 9Cr-RAFM steel and its modifications on post weld heat treatments (PWHT). Detailed characterization showed a mixed microstructure of austenite and martensite in the weld which is in agreement with the phases predicted using Schaeffler diagram based on composition measurements. The presence of very low volume fraction of δ-ferrite in SS316L has been identified employing state of the art electron back-scattered diffraction technique. PWHT of the ferritic steel did not reduce the hardness in the weld metal. Thermal exposure at 973 K (700 °C) showed a progressive reduction in hardness of weld joint with duration of treatment except in austenitic base metal. However, diffusion annealing at 1073 K (800 °C) for 100 hours resulted in an unexpected increase in hardness of weld metal, which is a manifestation of the dilution effects and enrichment of Ni on the transformation characteristics of the weld zone. Migration of carbon from ferritic steel aided the precipitation of fine carbides in the austenitic base metal on annealing at 973 K (700 °C); but enhanced diffusion at 1073 K (880 °C) resulted in coarsening of carbides and thereby reduction of hardness.

  8. Ultra-high cycle fatigue behavior of high strength steel with carbide-free bainite/martensite complex microstructure

    Institute of Scientific and Technical Information of China (English)

    Xue-xia Xu; Yang Yu; Wen-long Cui; Bing-zhe Bai; Jia-lin Gu

    2009-01-01

    The ultra-high cycle fatigue behavior of a novel high strength steel with carbide-free bainite/martensite (CFB/M) complex microstructure was studied. The ultra-high cycle fatigue properties were measured by ultrasonic fatigue testing equipment at a fre-quency of 20 kHz. It is found that there is no horizontal part in the S-N curve and fatigue fracture occurs when the life of specimens exceeds 107 cycles. In addition, the origination of fatigue cracks tends to transfer from the surface to interior of specimens as the fa-tigue cycle exceeds 107 , and the fatigue crack originations of many specimens are not induced by inclusions, but by some kind of "soft structure". It is shown that the studied high strength steel performs good ultra-high cycle fatigue properties. The ultra-high fa-tigue mechanism was discussed and it is suggested that specific CFB/M complex microstrueture of the studied steel contributes to itssuperior properties.

  9. On the nucleation and dissolution process of Z-phase Cr(V,Nb)N in martensitic 12%Cr steels

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2009-01-01

    Precipitation of large Z-phase particles, Cr(V,Nb)N, replacing fine MX nitrides, (V,Nb)N, has recently been identified as a major cause of premature breakdown in long-term creep strength of a number of new 9–12%Cr martensitic steels. The Z-phase precipitates slowly during long-term exposure...... at around 650 ◦C accelerated by high Cr content in the steels. It appears that the nucleation process controls the precipitation rate of Z-phase. A 12%Cr steel, which had precipitated Z-phase during long-term operation at 660 ◦C/12,000 h, was further heat treated in order to investigate the dissolution...... and reappearance processes for the Z-phase. In both cases it appears that Z-phase and MXphase are in physical contact and have a preferred crystallographic orientation relationship. The proposed nucleation mechanism is a chromium diffusion controlled transformation of MX into Z-phase, which explains the rather low...

  10. Stress corrosion cracking of welded joints of super-martensitic stainless steel in H{sub 2}S free environment

    Energy Technology Data Exchange (ETDEWEB)

    Hoerner, Bertrand; Bayle, Bernard; Delafosse, David [Centre Science des Materiaux et des Structures - URA CNRS 5146, ENS Mines de Saint-Etienne, 158 Cours Fauriel, 42023 Saint-Etienne cedex 02 (France); Ligier, Vincent [CRMC, INDUSTEEL Creusot, 56, rue Clemenceau, BP 56 - 71 202 Le Creusot Cedex (France)

    2004-07-01

    Due to their combination of good weldability and good mechanical properties, low carbon super-martensitic stainless steels are good candidates for oil and gas flow line applications. These alloys have already been used in slightly sour environments containing chlorides, CO{sub 2} and H{sub 2}S. The properties of a welded joint whose composition is matching or superduplex that of the base metal are investigated. The base material is the super-martensitic stainless steels medium alloy: 13Cr-4.5Ni-1.5Mo. The Heat Affected Zone (HAZ) of girth welds may be sensitive to stress corrosion cracking and presents distinct features intergranular cracking when tested in four-point bending in a sour deaerated environment at temperatures around 100 deg. C. The electrochemical properties of the medium alloy and the matching welded joint + HAZ were determined in a chloride-containing environment without H{sub 2}S. A passive film is formed on polished samples. This film is less protective for the welded joint + HAZ samples than in the base metal. Moreover, the pitting corrosion resistance is strongly decreased in the HAZ. Slow strain rate tensile tests were conducted in a de-aerated solution without H{sub 2}S. They reproduce the same type of cracking as was observed in four point bending tests in a sour environment: initiation in the HAZ and an intergranular crack with a very brittle aspect and no significant trace of corrosion. The presence H{sub 2}S is not the prevailing factor for the occurrence of cracking. Furthermore, it is not necessary to have a specific surface condition for crack initiation to occur in slow strain rate tension, as it is the case four point bend tests where initiation appears to be controlled by the surface condition (chemical and / or geometrical). Finally, a simulated PWHT strongly increase the resistance to SSC. (authors)

  11. Effects of Heat Treatment and Nitrogen on Microstructure and Mechanical Properties of 1Cr12NiMo Martensitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    Ruicheng Fan; Ming Gao; Yingche Ma; Xiangdong Zha; Xianchao Hao; Kui Liu

    2012-01-01

    A series of heat treatments using the orthogonal experiment method were performed to study the microstruc- ture and mechanical properties of 1Cr12NiMo martensitic stainless steel containing various nitrogen content addition. The results indicate that the optimal heat treatment is annealing at 830 ℃ for 1 h, austenitizing at 985 ℃ for 1 h followed by oil quenching, and tempering at 630 ℃ for 4 h followed by air cooling, Nitrogen addition to 1Cr12NiMo steel can effectively hinder the austenite grain growth, refine the martensite lath, and increase the strength and hardness. The impact toughness of this steel only shows a minor decrease as the nitrogen content increases.

  12. Effect of Heat Treatment on the Microstructure and Hardness of 17Cr-0.17N-0.43C-1.7 Mo Martensitic Stainless Steel

    Science.gov (United States)

    Krishna, S. Chenna; Gangwar, Narendra Kumar; Jha, Abhay K.; Pant, Bhanu; George, Koshy M.

    2015-04-01

    The microstructure and hardness of a nitrogen-containing martensitic stainless steel were investigated as a function of heat treatment using optical microscopy, electron microscopy, amount of retained austenite, and hardness measurement. The steel was subjected to three heat treatments: hardening, cryo treatment, and tempering. The hardness of the steel in different heat-treated conditions ranged within 446-620 HV. The constituents of microstructure in hardened condition were lath martensite, retained austenite, M23C6, M7C3, MC carbides, and M(C,N) carbonitrides. Upon tempering at 500 °C, two new phases have precipitated: fine spherical Mo2C carbides and needle-shaped Cr2N particles.

  13. Investigation of influence of structure and TiAl3/TiAlN intermetallic coatings on the corrosion behavior of martensitic steels

    Science.gov (United States)

    Vardanyan, E.; Ramazanov, K.; Yagafarov, I.; Khamzina, A.; Agzamov, R.

    2017-05-01

    The paper considers several approaches to protect martensitic steels with ultrafine-grain (UFG) structure in aggressive environments. Scanning electron microscopy was used to study the microstructure and composition of steel substrates and coatings. The samples were also subjected to corrosion tests. Regularities of corrosion behavior were specified for the UFG steels. The samples were subjected to ion nitriding in a glow discharge and deposition of protective TiAl3/TiAlN coatings in vacuum arc discharge plasma. Corrosion rates were identified for different treatments.

  14. Hydrogen embrittlement property of a 1700-MPa-class ultrahigh-strength tempered martensitic steel

    Science.gov (United States)

    Li, Songjie; Akiyama, Eiji; Yuuji, Kimura; Tsuzaki, Kaneaki; Uno, Nobuyoshi; Zhang, Boping

    2010-04-01

    The hydrogen embrittlement property of a prototype 1700-MPa-class ultrahigh-strength steel (NIMS17) containing hydrogen traps was evaluated using a slow strain rate test (SSRT) after cathodic hydrogen precharging, cyclic corrosion test (CCT) and atmospheric exposure. The hydrogen content in a fractured specimen was measured after SSRT by thermal desorption spectroscopy (TDS). The relationship between fracture stress and hydrogen content for the hydrogen-precharged specimens showed that the fracture stress of NIMS17 steel was higher, at a given hydrogen content, than that of conventional AISI 4135 steels with tensile strengths of 1300 and 1500 MPa. This suggests better resistance of NIMS17 steel to hydrogen embrittlement. However, hydrogen uptake to NIMS17 steel under CCT and atmospheric exposure decreased the fracture stress. This is because of the stronger hydrogen uptake to the steel containing hydrogen traps than to the AISI 4135 steels. Although NIMS17 steel has a higher strength level than AISI 4135 steel with a tensile strength of 1500 MPa, the decrease in fracture stress is similar between these steels.

  15. Hydrogen embrittlement property of a 1700-MPa-class ultrahigh-strength tempered martensitic steel

    Directory of Open Access Journals (Sweden)

    Songjie Li, Eiji Akiyama, Kimura Yuuji, Kaneaki Tsuzaki, Nobuyoshi Uno and Boping Zhang

    2010-01-01

    Full Text Available The hydrogen embrittlement property of a prototype 1700-MPa-class ultrahigh-strength steel (NIMS17 containing hydrogen traps was evaluated using a slow strain rate test (SSRT after cathodic hydrogen precharging, cyclic corrosion test (CCT and atmospheric exposure. The hydrogen content in a fractured specimen was measured after SSRT by thermal desorption spectroscopy (TDS. The relationship between fracture stress and hydrogen content for the hydrogen-precharged specimens showed that the fracture stress of NIMS17 steel was higher, at a given hydrogen content, than that of conventional AISI 4135 steels with tensile strengths of 1300 and 1500 MPa. This suggests better resistance of NIMS17 steel to hydrogen embrittlement. However, hydrogen uptake to NIMS17 steel under CCT and atmospheric exposure decreased the fracture stress. This is because of the stronger hydrogen uptake to the steel containing hydrogen traps than to the AISI 4135 steels. Although NIMS17 steel has a higher strength level than AISI 4135 steel with a tensile strength of 1500 MPa, the decrease in fracture stress is similar between these steels.

  16. Hydrogen embrittlement property of a 1700-MPa-class ultrahigh-strength tempered martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Li Songjie; Zhang Boping [School of Materials Science and Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Hidian Zone, Beijing 100083 (China); Akiyama, Eiji; Yuuji, Kimura; Tsuzaki, Kaneaki [Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Uno, Nobuyoshi, E-mail: AKIYAMA.Eiji@nims.go.j [Nippon Steel and Sumikin Metal Products Co, Ltd, SA Bldg., 17-12 Kiba 2-chome, Koto-ku, Tokyo (Japan)

    2010-04-15

    The hydrogen embrittlement property of a prototype 1700-MPa-class ultrahigh-strength steel (NIMS17) containing hydrogen traps was evaluated using a slow strain rate test (SSRT) after cathodic hydrogen precharging, cyclic corrosion test (CCT) and atmospheric exposure. The hydrogen content in a fractured specimen was measured after SSRT by thermal desorption spectroscopy (TDS). The relationship between fracture stress and hydrogen content for the hydrogen-precharged specimens showed that the fracture stress of NIMS17 steel was higher, at a given hydrogen content, than that of conventional AISI 4135 steels with tensile strengths of 1300 and 1500 MPa. This suggests better resistance of NIMS17 steel to hydrogen embrittlement. However, hydrogen uptake to NIMS17 steel under CCT and atmospheric exposure decreased the fracture stress. This is because of the stronger hydrogen uptake to the steel containing hydrogen traps than to the AISI 4135 steels. Although NIMS17 steel has a higher strength level than AISI 4135 steel with a tensile strength of 1500 MPa, the decrease in fracture stress is similar between these steels.

  17. Production and qualification for fusion applications, a steel of low activity ferritic-martensitic ASTURFER; Produccion y cualificacion, para aplicaciones de fusion, de un acero de baja actividad ferritico-martensitico, ASTURFER

    Energy Technology Data Exchange (ETDEWEB)

    Moran, A.; Belzunce, J.; Artimez, J. M.

    2011-07-01

    This article details the work carried out in the design and development pilot plant scale of a steel ferritic-martensitic of reduced activity, Asturfer, with a chemical composition and metallurgical properties similar to steel Eurofer. We describe the different stages of steel production and the results of the characterizations made in the context of an extensive test program.

  18. Crystallographic Analysis of Martensite in 0.2C-2.0Mn-1.5Si-0.6Cr Steel using EBSD

    Institute of Scientific and Technical Information of China (English)

    Pasi P. Suikkanen; Cyril Cayron; Anthony J. DeArdo; L Pentti Karjalainen

    2011-01-01

    The crystallography of martensite formed in 0.2C-2.0Mn-1,5Si-0.6Cr steel was studied using the electron backscattered diffraction (EBSD) technique. The results showed that the observed orientation relationship (OR) was closer to that of Nishiyama-Wassermann (N-W) than Kurdjumov-Sachs. The martensite consisted of parallel laths forming morphological packets. Typically, there were three different lath orientations in a morphological packet consisting of three specific N-W OR variants sharing the same {111} austenite plane. A packet of martensite laths with a common {111} austenite plane was termed a crystallographic packet. Generally, the crystallographic packet size corresponded to the morphological packet size, but occasionally the morphological packet was found to consist of two or more crystallographic packets. Therefore, the crystallographic packet size appeared to be finer than the morphological packet size. The relative orientation between the variants in crystallographic packets was found to be near 60°〈110〉, which explains the strong peak observed near 60° in the grain boundary misorientation distribution. Martensite also contained a high fraction of boundaries with a misorientation in the range 2.5-8°. Typically these boundaries were found to be located inside the martensite laths forming sub-laths.

  19. Mechanical properties of neutron-irradiated nickel-containing martensitic steels: I. Experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge National Laboratory, P.O. Box 2008, MS 6151, Oak Ridge, Tennessee 37831-6151 (United States)]. E-mail: kluehrl@ornl.gov; Hashimoto, N. [Oak Ridge National Laboratory, P.O. Box 2008, MS 6151, Oak Ridge, Tennessee 37831-6151 (United States); Sokolov, M.A. [Oak Ridge National Laboratory, P.O. Box 2008, MS 6151, Oak Ridge, Tennessee 37831-6151 (United States); Shiba, K. [Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Tokai, Ibaraki 319-1195 (Japan); Jitsukawa, S. [Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Tokai, Ibaraki 319-1195 (Japan)

    2006-10-15

    Tensile and Charpy specimens of 9Cr-1MoVNb (modified 9Cr-1Mo) and 12Cr-1MoVW (Sandvik HT9) steels and these steels doped with 2% Ni were irradiated at 300 and 400 deg. C in the High Flux Isotope Reactor (HFIR) up to {approx}12 dpa and at 393 deg. C in the Fast Flux Test Facility (FFTF) to {approx}15 dpa. In HFIR, a mixed-spectrum reactor (n, {alpha}) reactions of thermal neutrons with {sup 58}Ni produce helium in the steels. Little helium is produced during irradiation in FFTF. After HFIR irradiation, the yield stress of all steels increased, with the largest increases occurring for nickel-doped steels. The ductile-brittle transition temperature (DBTT) increased up to two times and 1.7 times more in steels with 2% Ni than in those without the nickel addition after HFIR irradiation at 300 and 400 deg. C, respectively. Much smaller differences occurred between these steels after irradiation in FFTF. The DBTT increases for steels with 2% Ni after HFIR irradiation were 2-4 times greater than after FFTF irradiation. Results indicated there was hardening due to helium in addition to hardening by displacement damage and irradiation-induced precipitation.

  20. Microstructure of Z-phase strengthened martensitic steels: Meeting the 650°C challenge

    DEFF Research Database (Denmark)

    Liu, Fang; Rashidi, Masoud; Hald, John

    2017-01-01

    We studied three series of Z-phase strengthened steels using scanning electron microscopy, transmission electron microscopy, and atom probe tomography to reveal the detailed microstructure of these steels. In particular, the phase transformation from M(C,N) to Z-phase (CrMN) was studied. Carbon...... content in the steels is the governing factor in this transformation. The impact toughness of some test alloys was rather low. This is attributed to the formation of a continuous W-rich film along prior austenite grain boundaries. Cu and C addition to the test alloys changed Laves phase morphology...... to discrete precipitates and improved toughness dramatically. BN particles were found in some steels. Formation of BN is directly linked to the B concentration in the steels....

  1. Impact of the use of the ferritic/martensitic ODS steels cladding on the fuel reprocessing PUREX process

    Science.gov (United States)

    Gwinner, B.; Auroy, M.; Mas, D.; Saint-Jevin, A.; Pasquier-Tilliette, S.

    2012-09-01

    Some ferritic/martensitic oxide dispersed strengthened (F/M ODS) steels are presently developed at CEA for the fuel cladding of the next generation of sodium fast nuclear reactors. The objective of this work is to study if this change of cladding could have any consequences on the spent fuel reprocessing PUREX process. During the fuel dissolution stage the cladding can actually be corroded by nitric acid. But some process specifications impose not to exceed a limit concentration of the corrosion products such as iron and chromium in the dissolution medium. For that purpose the corrosion behavior of these F/M ODS steels is studied in hot and concentrated nitric acid. The influence of some metallurgical parameters such as the chromium content, the elaboration process and the presence of the yttrium oxides is first discussed. The influence of environmental parameters such as the nitric acid concentration, the temperature and the presence of oxidizing species coming from the fuel is then analyzed. The corrosion rate is characterized by mass loss measurements and electrochemical tests. Analyses of the corroded surface are carried out by X-ray photoelectron spectroscopy.

  2. Influence of high temperature pre-deformation on the dissolution rate of delta ferrites in martensitic heat-resistant steels

    Science.gov (United States)

    Li, Junru; Liu, Jianjun; Jiang, Bo; Zhang, Chaolei; Liu, Yazheng

    2017-03-01

    The dissolution process of delta ferrites and the influence of high temperature pre-deformation on the dissolution rate of delta ferrites in martensitic heat-resistant steel 10Cr12Ni3Mo2VN were studied by isothermal heating and thermal simulation experiments. The precipitation temperature of delta ferrites in experimental steel is about 1195 °C. M23C6-type carbides incline to precipitate and coarsen at the boundaries of delta ferrites below 930 °C, and can be rapidly dissolved by heating at 1180 °C. The percentage of delta ferrites gradually decreases with heating time. And a Kolmogorov-Johnson-Mehl-Avrami equation was established to describe the dissolution process of delta ferrites at 1180 °C. High temperature pre-deformation can markedly increase the dissolution rate of delta ferrites. Pre-deformation can largely increase the interface area between delta ferrite and matrix and thus increase the unit-time diffusing quantities of alloying elements between delta ferrites and matrix. In addition, high temperature pre-deformation leads to dynamic recrystallization and increases the number of internal grain boundaries in the delta ferrites. This can also greatly increase the diffusing rate of alloying elements. In these cases, the dissolution of delta ferrites can be promoted.

  3. Blister formation on 13Cr2MoNbVB ferritic-martensitic steel exposed to hydrogen plasma

    Science.gov (United States)

    Nikitin, A. V.; Tolstolutskaya, G. D.; Ruzhytskyi, V. V.; Voyevodin, V. N.; Kopanets, I. E.; Karpov, S. A.; Vasilenko, R. L.; Garner, F. A.

    2016-09-01

    The influence of pre-irradiation specimen deformation level on surface blister formation and sub-surface cracking of dual-phase 13Cr2MoNbVB ferritic-martensitic steel was studied using glow discharge hydrogen plasma with ion energy of 1 keV to fluences of 2 × 1025 H/m2. Protium was used for most studies, but deuterium was used for measuring the depth dependence of hydrogen diffusion. Formation of blisters was observed in the temperature range 230-340 K. It was found that pre-irradiation deformation caused changes in the threshold fluences of blister formation and also in blister size distribution. Subsurface cracks located on grain boundaries far beyond the implantation zone were formed concurrently with blisters, arising from hydrogen diffusion and trapping at defects. It was observed that cracks as long as 1 mm in length were formed in 95% deformed steel at depths up to 500 μm from surface.

  4. Blister formation on 13Cr2MoNbVB ferritic-martensitic steel exposed to hydrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, A.V. [Institute of Solid State Physics, Material Science and Technology NSC KIPT, Kharkov (Ukraine); Tolstolutskaya, G.D., E-mail: g.d.t@kipt.kharkov.ua [Institute of Solid State Physics, Material Science and Technology NSC KIPT, Kharkov (Ukraine); Ruzhytskyi, V.V.; Voyevodin, V.N.; Kopanets, I.E.; Karpov, S.A.; Vasilenko, R.L. [Institute of Solid State Physics, Material Science and Technology NSC KIPT, Kharkov (Ukraine); Garner, F.A. [Radiation Effects Consulting, Richland, WA (United States); National Research Nuclear University, Moscow Engineering Physics Institute, Moscow (Russian Federation)

    2016-09-15

    The influence of pre-irradiation specimen deformation level on surface blister formation and sub-surface cracking of dual-phase 13Cr2MoNbVB ferritic-martensitic steel was studied using glow discharge hydrogen plasma with ion energy of 1 keV to fluences of 2 × 10{sup 25} H/m{sup 2}. Protium was used for most studies, but deuterium was used for measuring the depth dependence of hydrogen diffusion. Formation of blisters was observed in the temperature range 230–340 K. It was found that pre-irradiation deformation caused changes in the threshold fluences of blister formation and also in blister size distribution. Subsurface cracks located on grain boundaries far beyond the implantation zone were formed concurrently with blisters, arising from hydrogen diffusion and trapping at defects. It was observed that cracks as long as 1 mm in length were formed in 95% deformed steel at depths up to 500 μm from surface.

  5. Effect of cyclic treatment on the formation of a fragmented structure in a sparingly alloyed martensitic steel

    Science.gov (United States)

    Tabatchikova, T. I.; Yakovleva, I. L.; Delgado Reina, S. Yu.; Plokhikh, A. I.

    2016-11-01

    Methods of metallography and transmission electron microscopy were used to study the structure of a high-alloy low-carbon steel of martensitic VKS-10 class subjected to cyclic treatment according to different regimes. It has been found that the warm deformation in the α state at 700°C causes the fragmentation of the structure; however, the decomposition of the α solid solution and the precipitation of coarse carbides leads to a significant decrease in the strength. It has been shown that 12 cycles of treatment, including austenitizing at 1000°C, rolling at 700°C, and subsequent γ → α transformation during rapid cooling do not lead to a noticeable fragmentation of the structure. It has been found that the deformation of the overcooled austenite by rolling carried out using 12 cycles in the range of temperatures of 700-500°C and subsequent γ → α transformation lead to the formation of a fragmented structure with a large fraction of fine grains with a size less than 0.5 μm. This treatment and the subsequent tempering at 530°C for 1 h allow us to increase the strength and hardness of the VKS-10 steel at an insignificant decrease in the plasticity.

  6. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

    Science.gov (United States)

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-01

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α‧-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α‧ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α‧N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  7. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel.

    Science.gov (United States)

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-05

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α'-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α' → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α'N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  8. Effect of Thermal Aging on Microstructure and Mechanical Properties of China Low-Activation Martensitic Steel at 550 °C

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2016-04-01

    Full Text Available The thermal aging effects on mechanical properties and microstructures in China low-activation martensitic steel have been tested by aging at 550 °C for 2,000 hours, 4,000 hours, and 10,000 hours. The microstructure was analyzed by scanning and transmission electron microscopy. The results showed that the grain size and martensitic lath increased by about 4 μm and 0.3 μm, respectively, after thermal exposure at 550 °C for 10,000 hours. MX type particles such as TaC precipitated on the matrix and Laves-phase was found on the martensitic lath boundary and grain boundary on aged specimens. The mechanical properties were investigated with tensile and Charpy impact tests. Tensile properties were not seriously affected by aging. Neither yield strength nor ultimate tensile strength changed significantly. However, the ductile–brittle transition temperature of China low-activation martensitic steel increased by 46 °C after aging for 10,000 hours due to precipitation and grain coarsening.

  9. Embrittlement behavior of neutron irradiated RAFM steels

    Energy Technology Data Exchange (ETDEWEB)

    Gaganidze, E. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)]. E-mail: ermile.gaganidze@imf.fzk.de; Schneider, H.-C. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Dafferner, B. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Aktaa, J. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2007-08-01

    The effects of neutron irradiation on the embrittlement behavior of reduced activation ferritic/martensitic (RAFM) steel EUROFER97 for different heat treatment conditions have been investigated. The irradiation to 16.3 dpa at different irradiation temperatures (250-450 {sup o}C) was carried out in the Petten High Flux Reactor in the framework of the HFR Phase-IIb (SPICE) irradiation project. Several reference RAFM steels (F82H-mod, OPTIFER-Ia, GA3X) and MANET-I were also irradiated at selected temperatures. The embrittlement behavior and hardening were investigated by instrumented Charpy-V tests with subsize specimens. The neutron irradiation induced embrittlement and hardening of as-delivered EUROFER97 are comparable to those of investigated reference steels, being mostly pronounced for 250 {sup o}C and 300 {sup o}C irradiation temperatures. Heat treatment of EUROFER97 at higher austenization temperature substantially improves the embrittlement behavior at irradiation temperatures of 250 {sup o}C and 350 {sup o}C.

  10. Embrittlement behavior of neutron irradiated RAFM steels

    Science.gov (United States)

    Gaganidze, E.; Schneider, H.-C.; Dafferner, B.; Aktaa, J.

    2007-08-01

    The effects of neutron irradiation on the embrittlement behavior of reduced activation ferritic/martensitic (RAFM) steel EUROFER97 for different heat treatment conditions have been investigated. The irradiation to 16.3 dpa at different irradiation temperatures (250-450 °C) was carried out in the Petten High Flux Reactor in the framework of the HFR Phase-IIb (SPICE) irradiation project. Several reference RAFM steels (F82H-mod, OPTIFER-Ia, GA3X) and MANET-I were also irradiated at selected temperatures. The embrittlement behavior and hardening were investigated by instrumented Charpy-V tests with subsize specimens. The neutron irradiation induced embrittlement and hardening of as-delivered EUROFER97 are comparable to those of investigated reference steels, being mostly pronounced for 250 °C and 300 °C irradiation temperatures. Heat treatment of EUROFER97 at higher austenization temperature substantially improves the embrittlement behavior at irradiation temperatures of 250 °C and 350 °C.

  11. Small punch tensile/fracture test data and 3D specimen surface data on Grade 91 ferritic/martensitic steel from cryogenic to room temperature.

    Science.gov (United States)

    Bruchhausen, Matthias; Lapetite, Jean-Marc; Ripplinger, Stefan; Austin, Tim

    2016-12-01

    Raw data from small punch tensile/fracture tests at two displacement rates in the temperature range from -196 °C to room temperature on Grade 91 ferritic/martensitic steel are presented. A number of specimens were analyzed after testing by means of X-ray computed tomography (CT). Based on the CT volume data detailed 3D surface maps of the specimens were established. All data are open access and available from Online Data Information Network (ODIN)https://odin.jrc.ec.europa.eu. The data presented in the current work has been analyzed in the research article "On the determination of the ductile to brittle transition temperature from small punch tests on Grade 91 ferritic-martensitic steel" (M. Bruchhausen, S. Holmström, J.-M. Lapetite, S. Ripplinger, 2015) [1].

  12. SSC Resistance of Super 13Cr Martensitic Stainless Steel%超级13Cr马氏体不锈钢抗SSC性能研究

    Institute of Scientific and Technical Information of China (English)

    吕祥鸿; 赵国仙; 王宇; 张建兵; 谢凯意

    2011-01-01

    H2S stress corrosion cracking (SSC) behavior of super 13Cr martensitic stainless steel at the simulated and standard environments has been studied with four-point bent test, electrochemical measurement as well as Scanning Electron Microscopy (SEM) analysis methods. The results show that the super 13Cr martensitic stainless steel behaves a high SSC susceptibility at the standard environments, and the cracks stem from surface corrosion pits because of the occurrence of H2S and Clmaking the pitting potential of super 13Cr martensitic stainless steel decreased significantly. While at the simulated environments, the SSC susceptibility of super 13Cr martensitic stainless steel decreased, and no cracks are found on the surface of the test specimen.%采用四点弯曲实验方法、电化学测试技术及扫描电子显微镜(SEM)等分析手段研究了超级13Cr马氏体不锈钢在模拟工况和标准工况中的H2S应力腐蚀开裂(SSC)行为.结果表明:超级13Cr 马氏体不锈钢在标准工况条件下具有很高的SSC敏感性,裂纹起源于表面点蚀坑处,H2S腐蚀性气体的存在及Cl-浓度的增加显著降低超级13Cr马氏体不锈钢的点蚀电位,明显增加超级13Cr马氏体不锈钢的SSC敏感性;在模拟工况条件下,超级13Cr发生SSC的敏感性降低,没有发生开裂现象.

  13. Investigations of the corrosion fatigue behaviour at a super pure martensitic stainless steel X5CrNiCuNb 17 4 PH in comparison to the soft martensitic stainless steel X4CrNiMo 16 5 1 ESR in chloride containing aqueous media. Pt. 2. Corrosion fatigue tests and crack initiation mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt-Thomas, K.G.; Happle, T.; Wunderlich, R.

    1989-07-01

    The following report concerns the study of the corrosion fatigue behaviour of the soft martensitic steel X4CrNiMo 16 5 1 ESR and the precipitation hardened X5CrNiCuNb 17 4 PH in sodium solution in the temperature range between 20/sup 0/ and 150/sup 0/C and the determination of their general corrosion properties and the mechanism of crack propagation. Their corrosion fatigue limits were compared with each other. A comparison was also made between an electro-slag-remelted soft martensitic steel and a charge without an ESR aftertreatment. Microfractographical fracture and crack path investigation were carried out for interpretation of the experimental results. It was observed that in both super pure steels (soft martensitic and precipitation hardened) the oxidic inclusions are not responsible for the crack initiation, as it was found in the non ESR treated steels. In the 17-4 PH steel copper containing inclusions in the crack initiation areas were observed. In concentrated sodium solution pitting corrosion was found at both steels. (orig.).

  14. Summary Report of Summer Work: High Purity Single Crystal Growth & Microstructure of Ferritic-Martensitic Steels

    Energy Technology Data Exchange (ETDEWEB)

    Pestovich, Kimberly Shay [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-18

    Harnessing the power of the nuclear sciences for national security and to benefit others is one of Los Alamos National Laboratory’s missions. MST-8 focuses on manipulating and studying how the structure, processing, properties, and performance of materials interact at the atomic level under nuclear conditions. Within this group, single crystal scintillators contribute to the safety and reliability of weapons, provide global security safeguards, and build on scientific principles that carry over to medical fields for cancer detection. Improved cladding materials made of ferritic-martensitic alloys support the mission of DOE-NE’s Fuel Cycle Research and Development program to close the nuclear fuel cycle, aiming to solve nuclear waste management challenges and thereby increase the performance and safety of current and future reactors.

  15. Factors affecting hydrogen-assisted cracking in a commercial tempered martensitic steel: Mn segregation, MnS, and the stress state around abnormal cracks

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Daisuke [Graduate School of Kyushu University, Fukuoka 819-0395 (Japan); Koyama, Motomichi [Department of Mechanical Engineering, Faculty of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku Fukuoka 819-0395 (Japan); Noguchi, Hiroshi, E-mail: nogu@mech.kyushu-u.ac.jp [Department of Mechanical Engineering, Faculty of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku Fukuoka 819-0395 (Japan)

    2015-07-29

    The purpose of this paper is to reveal the dominant factors affecting tensile fracture under a hydrogen gas atmosphere. Tensile tests were conducted in hydrogen gas with circumferentially-notched specimens of a commercial tempered martensitic steel. Two specimens were exposed to hydrogen gas for 48 h before tensile testing; the other two specimens were not pre-charged. Longitudinal cracks along the loading direction and a transverse crack perpendicular to the loading direction were observed on a cross section of the non-charged specimen, but there was only one small crack on a cross section of the pre-charged specimen. Electron back scatter diffraction, energy dispersive X-ray spectrometry and finite element method analyses were applied to clarify the relationships among the longitudinal crack, Mn segregation, microstructures of martensitic steel and hydrogen. As a result, it has been demonstrated that Mn segregation and MnS promote hydrogen-assisted cracking in the tempered martensitic steel, causing the longitudinal cracking which is a mechanically non-preferential direction in homogeneous situations. More specifically, we have shown that the role of the Mn segregation is to promote the hydrogen-enhanced decohesion effect (HEDE), which is particularly important for crack propagation in the present case. These considerations indicate that the presence of Mn is crucially important for hydrogen-assisted cracking associated with hydrogen-enhanced localized plasticity (HELP) as well as HEDE.

  16. High-dose neutron irradiation embrittlement of RAFM steels

    Energy Technology Data Exchange (ETDEWEB)

    Gaganidze, E. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, P.O. Box 3640, 76021 Karlsruhe (Germany)]. E-mail: ermile.gaganidze@imf.fzk.de; Schneider, H.-C. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, P.O. Box 3640, 76021 Karlsruhe (Germany); Dafferner, B. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, P.O. Box 3640, 76021 Karlsruhe (Germany); Aktaa, J. [Forschungszentrum Karlsruhe, Institut fuer Materialforschung II, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2006-09-01

    Neutron irradiation-induced embrittlement of the reduced-activation ferritic/martensitic (RAFM) steel EUROFER97 was studied under different heat treatment conditions. Irradiation was performed in the Petten High Flux Reactor within the HFR Phase-IIb (SPICE) irradiation project up to 16.3 dpa and at different irradiation temperatures (250-450 deg. C). Several reference RAFM steels (F82H-mod, OPTIFER-Ia, GA3X and MANET-I) were also irradiated at selected temperatures. The impact properties were investigated by instrumented Charpy-V tests with subsize specimens. Embrittlement and hardening of as-delivered EUROFER97 steel are comparable to those of reference steels. Heat treatment of EUROFER97 at a higher austenitizing temperature substantially improves the embrittlement behaviour at low irradiation temperatures. Analysis of embrittlement in terms of the parameter C = {delta}DBTT/{delta}{sigma} indicates hardening-dominated embrittlement at irradiation temperatures below 350 deg. C with 0.17 {<=} C {<=} 0.53 deg. C/MPa. Scattering of C at irradiation temperatures above 400 deg. C indicates no hardening embrittlement.

  17. High-dose neutron irradiation embrittlement of RAFM steels

    Science.gov (United States)

    Gaganidze, E.; Schneider, H.-C.; Dafferner, B.; Aktaa, J.

    2006-09-01

    Neutron irradiation-induced embrittlement of the reduced-activation ferritic/martensitic (RAFM) steel EUROFER97 was studied under different heat treatment conditions. Irradiation was performed in the Petten High Flux Reactor within the HFR Phase-IIb (SPICE) irradiation project up to 16.3 dpa and at different irradiation temperatures (250-450 °C). Several reference RAFM steels (F82H-mod, OPTIFER-Ia, GA3X and MANET-I) were also irradiated at selected temperatures. The impact properties were investigated by instrumented Charpy-V tests with subsize specimens. Embrittlement and hardening of as-delivered EUROFER97 steel are comparable to those of reference steels. Heat treatment of EUROFER97 at a higher austenitizing temperature substantially improves the embrittlement behaviour at low irradiation temperatures. Analysis of embrittlement in terms of the parameter C = ΔDBTT/Δ σ indicates hardening-dominated embrittlement at irradiation temperatures below 350 °C with 0.17 ⩽ C ⩽ 0.53 °C/MPa. Scattering of C at irradiation temperatures above 400 °C indicates no hardening embrittlement.

  18. Precipitation behavior of carbides in high-carbon martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao; Shi, Chang-min [University of Science and Technology, Beijing (China). State Key Laboratory of Advanced Metallurgy; Li, Ji-hui [Yang Jiang Shi Ba Zi Group Co., Ltd, Guangdong (China)

    2017-01-15

    A fundamental study on the precipitation behavior of carbides was carried out. Thermo-calc software, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, X-ray diffractometry and high-temperature confocal laser scanning microscopy were used to study the precipitation and transformation behaviors of carbides. Carbide precipitation was of a specific order. Primary carbides (M7C3) tended to be generated from liquid steel when the solid fraction reached 84 mol.%. Secondary carbides (M7C3) precipitated from austenite and can hardly transformed into M23C6 carbides with decreasing temperature in air. Primary carbides hardly changed once they were generated, whereas secondary carbides were sensitive to heat treatment and thermal deformation. Carbide precipitation had a certain effect on steel-matrix phase transitions. The segregation ability of carbon in liquid steel was 4.6 times greater that of chromium. A new method for controlling primary carbides is proposed.

  19. Hybrid Laser-arc Welding of 17-4 PH Martensitic Stainless Steel

    Science.gov (United States)

    Liu, Wei; Ma, Junjie; Atabaki, Mehdi Mazar; Pillai, Raju; Kumar, Biju; Vasudevan, Unnikrishnan; Sreshta, Harold; Kovacevic, Radovan

    2015-06-01

    17-4 PH stainless steel has wide applications in severe working conditions due to its combination of good corrosion resistance and high strength. The weldability of 17-4 PH stainless steel is challenging. In this work, hybrid laser-arc welding was developed to weld 17-4 PH stainless steel. This method was chosen based on its advantages, such as deep weld penetration, less filler materials, and high welding speed. The 17-4 PH stainless steel plates with a thickness of 19 mm were successfully welded in a single pass. During the hybrid welding, the 17-4 PH stainless steel was immensely susceptible to porosity and solidification cracking. The porosity was avoided by using nitrogen as the shielding gas. The nitrogen stabilized the keyhole and inhibited the formation of bubbles during welding. Solidification cracking easily occurred along the weld centerline at the root of the hybrid laser-arc welds. The microstructural evolution and the cracking susceptibility of 17-4 PH stainless steel were investigated to remove these centerline cracks. The results showed that the solidification mode of the material changed due to high cooling rate at the root of the weld. The rapid cooling rate caused the transformation from ferrite to austenite during the solidification stage. The solidification cracking was likely formed as a result of this cracking-susceptible microstructure and a high depth/width ratio that led to a high tensile stress concentration. Furthermore, the solidification cracking was prevented by preheating the base metal. It was found that the preheating slowed the cooling rate at the root of the weld, and the ferrite-to-austenite transformation during the solidification stage was suppressed. Delta ferrite formation was observed in the weld bead as well no solidification cracking occurred by optimizing the preheating temperature.

  20. Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing

    Science.gov (United States)

    Ghasemi-Nanesa, H.; Nili-Ahmadabadi, M.; Shirazi, H.

    2010-07-01

    Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was epsilon ~7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

  1. Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing

    Energy Technology Data Exchange (ETDEWEB)

    Ghasemi-Nanesa, H; Shirazi, H [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, P.O. Box 14395-731 (Iran, Islamic Republic of); Nili-Ahmadabadi, M, E-mail: sut.caster.81710018@gmail.co, E-mail: nili@ut.ac.i [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, P.O. Box 14395-731 (Iran, Islamic Republic of) and Center of Excellence for High Performance Materials, University of Tehran, P.O. Box 14395-731, Tehran (Iran, Islamic Republic of)

    2010-07-01

    Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was {epsilon} {approx}7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

  2. Diffusion Couple Alloying of Refractory Metals in Austenitic and Ferritic/Martensitic Steels

    Science.gov (United States)

    2012-03-01

    Top) Photograph of diffusion couple block after hot isostatic pressing. (Bottom) Schematic of diffusion couple cylinders...excess of thermal creep) may raise the susceptibility, initiate, and sustain stress corrosion cracking. Creep also relieves compressive stresses (such as...general corrosion. They have moderate yield strength (~205MPa) which can be cold -worked to further improve it. Stainless steels are relatively

  3. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    NARCIS (Netherlands)

    Bojack, A.; Zhao, L.; Morris, P.F.; Sietsma, J.

    2016-01-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stage

  4. Optimization of the Process of Carburizing and Heat Treatment of Low-Carbon Martensitic Steels

    Science.gov (United States)

    Ivanov, A. S.; Greben'kov, S. K.; Bogdanova, M. V.

    2016-05-01

    Steel 24Kh2G2NMFB is studied after carburizing and different heat treatments. The hardness and microhardness of the surface layer and of the matrix are measured. The content of retained austenite is determined by the method of x-ray diffraction analysis. Heat treatment modes improving the structure of the surface layer after carburizing are suggested.

  5. Microstructure and mechanical property of ferritic-martensitic steel cladding under a 650 °C liquid sodium environment

    Science.gov (United States)

    Kim, Jun Hwan; Kim, Sung Ho

    2013-11-01

    A study was carried out to investigate the effect of liquid sodium on the microstructural and mechanical property of ferritic-martensitic steel (FMS) used for a Sodium-cooled Fast Reactor (SFR) cladding tube. A quasi-dynamic device characterized by natural circulation was constructed and a compatibility test between FMS and liquid sodium was performed. HT9 (12Cr-1MoWVN) and Gr.92 (9Cr-2WNbVNB) coupons as well as a Gr.92 cladding tube were immersed in the 650 °C liquid sodium up to 3095 h and a microstructural observation, a mechanical property evaluation such as nanoindentation, and a ring tension test were also done in this study. The results showed that both HT9 and Gr.92 exhibited macroscopic weight loss behavior where pitting and decarburization took place. Weight loss as well as the decarburization process decreased as the chromium content increased. A compatibility test over the cladding tube revealed that a decrease of the mechanical property caused by the aging process governed the whole mechanical property of the cladding tube.

  6. Gas Metal Arc Welding Process Modeling and Prediction of Weld Microstructure in MIL A46100 Armor-Grade Martensitic Steel

    Science.gov (United States)

    Grujicic, M.; Arakere, A.; Ramaswami, S.; Snipes, J. S.; Yavari, R.; Yen, C.-F.; Cheeseman, B. A.; Montgomery, J. S.

    2013-06-01

    A conventional gas metal arc welding (GMAW) butt-joining process has been modeled using a two-way fully coupled, transient, thermal-mechanical finite-element procedure. To achieve two-way thermal-mechanical coupling, the work of plastic deformation resulting from potentially high thermal stresses is allowed to be dissipated in the form of heat, and the mechanical material model of the workpiece and the weld is made temperature dependent. Heat losses from the deposited filler-metal are accounted for by considering conduction to the adjoining workpieces as well as natural convection and radiation to the surroundings. The newly constructed GMAW process model is then applied, in conjunction with the basic material physical-metallurgy, to a prototypical high-hardness armor martensitic steel (MIL A46100). The main outcome of this procedure is the prediction of the spatial distribution of various crystalline phases within the weld and the heat-affected zone regions, as a function of the GMAW process parameters. The newly developed GMAW process model is validated by comparing its predictions with available open-literature experimental and computational data.

  7. Fabrication and integrity test preparation of HIP-joined W and ferritic-martensitic steel mockups for fusion reactor development

    Science.gov (United States)

    Lee, Dong Won; Shin, Kyu In; Kim, Suk Kwon; Jin, Hyung Gon; Lee, Eo Hwak; Yoon, Jae Sung; Choi, Bo Guen; Moon, Se Youn; Hong, Bong Guen

    2014-10-01

    Tungsten (W) and ferritic-martensitic steel (FMS) as armor and structural materials, respectively, are the major candidates for plasma-facing components (PFCs) such as the blanket first wall (BFW) and the divertor, in a fusion reactor. In the present study, three W/FMS mockups were successfully fabricated using a hot isostatic pressing (HIP, 900 °C, 100 MPa, 1.5 hrs) with a following post-HIP heat treatment (PHHT, tempering, 750 °C, 70 MPa, 2 hrs), and the W/FMS joining method was developed based on the ITER BFW and the test blanket module (TBM) development project from 2004 to the present. Using a 10-MHz-frequency flat-type probe to ultrasonically test of the joint, we found no defects in the fabricated mockups. For confirmation of the joint integrity, a high heat flux test will be performed up to the thermal lifetime of the mockup under the proper test conditions. These conditions were determined through a preliminary analysis with conventional codes such as ANSYS-CFX for thermal-hydraulic conditions considering the test facility, the Korea heat load test facility with an electron beam (KoHLT-EB), and its water coolant system at the Korea Atomic Energy Research Institute (KAERI).

  8. Influence of temperature on the oxidation/corrosion process of F82Hmod. martensitic steel in lead-bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Gomez Briceno, D.; Soler Crespo, L.; Martin Munoz, F.J.; Hernandez Arroyo, F

    2002-06-01

    A F82Hmod. martensitic steel has been tested in lead-bismuth under a gas atmosphere with a H{sub 2}/H{sub 2}O equilibrium of 0.3 to examine the influence of temperature on the oxidation/corrosion process. The temperature range studied was 535-550 deg. C, temperatures just below the temperature transformation of magnetite into wustite. The durations of the tests were 500 and 1000 h and the oxygen concentration in lead-bismuth was between 3x10{sup -7} and 4x10{sup -7} wt%. The results point out the existence of a threshold temperature, around 550 deg. C, above which corrosion occurs and the formation of a protective oxide layer is not possible. Two approaches have been considered to explain this behaviour: (a) a kinetic mechanism more than thermodynamic considerations as the driving force of the oxidation/corrosion in lead-bismuth under low oxygen potential, (b) the possible transformation of magnetite into wustite.

  9. Gas Metal Arc Welding Process Modeling and Prediction of Weld Microstructure in MIL A46100 Armor-Grade Martensitic Steel

    Science.gov (United States)

    2013-06-01

    bainitic , martensitic) phase trans- formations and the diffusional phase-transformations which produce microstructural constituents (e.g., pearlite...single-phase austenite region); (ii) the fine-grained sub-zone, which contains martensite and bainite formed during cooling from austenite with a...exposed and the products of austenite decompositionduringcooling (i.e.,martensite, bainite , ferrite); and (iv) the so-called sub-critical zone, within

  10. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

    2017-02-01

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at significantly lower strength region. It appeared that at high temperatures ≥ 600 ºC the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. It is reviewed, however, that the NFAs has much stronger radiation resistance at high temperatures, such as lower radiation-induced swelling, finer helium bubble formation and lower irradiation creep rate.

  11. Effects of strain rate on the hot deformation behavior and dynamic recrystallization in China low activation martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yuanyuan [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Xizhang, E-mail: kernel.chen@gmail.com [School of Mechanical and Electrical Engineering, Wenzhou University, Wenzhou 325035 (China); Madigan, Bruce [Montana Tech, Butte, MT (United States); Cao, Hongyan [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Konovalov, Sergey [Center for Collective Use Material Science, Siberian State Industrial University, Novokuznetsk (Russian Federation)

    2016-02-15

    Graphical abstract: - Highlights: • Average grain sizes of 1.8 μm are observed at strain rate of 10 s{sup −1}. • Peak stress value increased, but strain decreased with increasing of strain rate. • A catenuliform recrystallized occurred at a strain rate of 5 s{sup −1}. • DRX effect improved with increasing of deformation amounts. - Abstract: To investigate the effects of strain rate on dynamic recrystallization (DRX) behavior on China low activation martensitic steel, hot uniaxial compression tests with strain rates ranging from 0.1 s{sup −1} to 10 s{sup −1} and deformations amounts of 40% and 70% where conducted. The true stress–true strain curves were analyzed for the occurrence of DRX under the different strain rates and compressive deformation amounts. The steel microstructures were examined and linked to the observed stress-strain diagrams to study DRX. Results show that DRX was responsible for refining the grain structure over a wide range of strain rates under 70% deformation. However, significant DRX occurred only at the relatively low strain rate of 0.1 s{sup −1} under 40% deformation. The original elongated microstructure of the rolled plate from which the specimens were taken was replaced by dynamic recrystallization grains. At 70% deformation, the average grain size was 4.2 μm at a strain rate of 0.1 s{sup −1}, 2.5 μm at a strain rate of 5 s{sup −1}, 1.8 μm at a strain rate of 10 s{sup −1}. In conclusion, with increasing strain rate, the recrystallized grain size decreased and the peak stress increased.

  12. Optimization of mechanical alloying and spark-plasma sintering regimes to obtain ferrite–martensitic ODS steel

    Directory of Open Access Journals (Sweden)

    M.S. Staltsov

    2016-12-01

    Full Text Available The results of structure investigation, distribution uniformity of dispersed particles of Y2O3, porosity and density of the ferritic/martensitic reactor steel EP-450 (0.12C–13Cr–2Mo–Nb–V–B, wt% produced by spark-plasma sintering (SPS are presented. More than 140 samples were produced using different combinations of mechanical alloying (time, speed of attritor rotation and SPS parameters (temperature, speed of reaching preset temperature, pressure and time of exposure under pressure, concentration of strengthening particles. It is determined that the absence of strengthening Y2O3 nano-particles in local volumes of sintered specimens is connected with the imperfection of mechanical alloying, namely, the formation of agglomerates of matrix steel powder containing no oxide nano-particles. It has been determined that the time of mechanical alloying should not exceed 30h to provide minimum powder agglomeration, uniform distribution of Y2O3 particles in the powder mixture and minimum porosity of sintered samples. Spark-plasma sintering should be performed at the lowest possible temperature. As a result it was found that samples with 99% theoretical density can be obtained using the following optimized SPS-parameters: sintering temperature is 1098÷1163K; speed for reaching the preset temperature is >573K/min; load is 70÷80MPa; time of exposure under pressure – either without isothermal exposure, or exposure during ≥3min; optimum quantity of Y2O3 is 0.2÷0.5wt%.

  13. Hybrid Laser-Arc Welding of 10-mm-Thick Cast Martensitic Stainless Steel CA6NM: As-Welded Microstructure and Mechanical Properties

    Science.gov (United States)

    Mirakhorli, Fatemeh; Cao, Xinjin; Pham, Xuan-Tan; Wanjara, Priti; Fihey, Jean-Luc

    2016-07-01

    Cast CA6NM martensitic stainless steel plates, 10 mm in thickness, were welded using hybrid laser-arc welding. The effect of different welding speeds on the as-welded joint integrity was characterized in terms of the weld bead geometry, defects, microstructure, hardness, ultimate tensile strength, and impact energy. Significant defects such as porosity, root humping, underfill, and excessive penetration were observed at a low welding speed (0.5 m/min). However, the underfill depth and excessive penetration in the joints manufactured at welding speeds above 0.75 m/min met the specifications of ISO 12932. Characterization of the as-welded microstructure revealed untempered martensite and residual delta ferrite dispersed at prior-austenite grain boundaries in the fusion zone. In addition, four different heat-affected zones in the weldments were differentiated through hardness mapping and inference from the Fe-Cr-Ni ternary phase diagram. The tensile fracture occurred in the base metal for all the samples and fractographic analysis showed that the crack path is within the martensite matrix, along primary delta ferrite-martensite interfaces and within the primary delta ferrite. Additionally, Charpy impact testing demonstrated slightly higher fracture energy values and deeper dimples on the fracture surface of the welds manufactured at higher welding speeds due to grain refinement and/or lower porosity.

  14. Hydrogen embrittlement property of a 1700-MPa-class ultrahigh-strength tempered martensitic steel

    OpenAIRE

    Li, Songjie; Akiyama, Eiji; Yuuji, Kimura; Tsuzaki, Kaneaki; Uno, Nobuyoshi; Zhang, Boping

    2010-01-01

    The hydrogen embrittlement property of a prototype 1700-MPa-class ultrahigh-strength steel (NIMS17) containing hydrogen traps was evaluated using a slow strain rate test (SSRT) after cathodic hydrogen precharging, cyclic corrosion test (CCT) and atmospheric exposure. The hydrogen content in a fractured specimen was measured after SSRT by thermal desorption spectroscopy (TDS). The relationship between fracture stress and hydrogen content for the hydrogen-precharged specimens showed that the fr...

  15. Velocity hardening influence on the martensite transformation nature in constructional average alloy steel

    Institute of Scientific and Technical Information of China (English)

    Tsellermaer; V.; V.; Popova; N.; A.; Klimashin; S.; I.; Tihonikova; O.; V.; Konovalov; S.; V.; Kozlov; E.; V.; Gromov; V.; E.

    2005-01-01

    The quantitative study of the hardening velocity influence on the α-phase morphology in 30CrNi3MoVA (0.3% C, 1% Cr,3% Ni, 1% Mo, 1% V) cast average alloy steel after gomogenization (1125℃, 13 h), normalizing (980℃, 10 h) and high tempering (660℃, 10 h. with cooling on air) is the aim of this work.……

  16. Velocity hardening influence on the martensite transformation nature in constructional average alloy steel

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The quantitative study of the hardening velocity influence on the α-phase morphology in 30CrNi3MoVA (0.3% C, 1% Cr,3% Ni, 1% Mo, 1% V) cast average alloy steel after gomogenization (1125℃, 13 h), normalizing (980℃, 10 h) and high tempering (660℃, 10 h. with cooling on air) is the aim of this work.

  17. Modification in the Microstructure of Mod. 9Cr-1Mo Ferritic Martensitic Steel Exposed to Sodium

    Science.gov (United States)

    Prasanthi, T. N.; Sudha, Cheruvathur; Paul, V. Thomas; Bharasi, N. Sivai; Saroja, S.; Vijayalakshmi, M.

    2014-09-01

    Mod. 9Cr-1Mo is used as the structural material in the steam generator circuit of liquid metal-cooled fast breeder reactors. Microstructural modifications on the surface of this steel are investigated after exposing to flowing sodium at a temperature of 798 K (525 °C) for 16000 hours. Sodium exposure results in the carburization of the ferritic steel up to a depth of ~218 µm from the surface. Electron microprobe analysis revealed the existence of two separate zones with appreciable difference in microchemistry within the carburized layer. Differences in the type, morphology, volume fraction, and microchemistry of the carbides present in the two zones are investigated using analytical transmission electron microscopy. Formation of separate zones within the carburized layer is understood as a combined effect of leaching, diffusion of the alloying elements, and thermal aging. Chromium concentration on the surface in the α-phase suggested possible degradation in the corrosion resistance of the steel. Further, concentration-dependent diffusivities for carbon are determined in the base material and carburized zones using Hall's and den Broeder's methods, respectively. These are given as inputs for simulating the concentration profiles for carbon using numerical computation technique based on finite difference method. Predicted thickness of the carburized zone agrees reasonably well with that of experiment.

  18. Z phase precipitation in martensitic 12CrMoVNb steels

    Science.gov (United States)

    Vodarek, V.; Strang, A.

    2003-10-01

    Precipitation of Z phase contributes significantly to degradation of creep properties of 12CrMoVNb steels because its precipitation is accompanied by dissolution offinely dispersed nitrides and carbonitrides of M2X and/or MX type. The orientation relationship between Z phase and the ferritic matrix was determined as: (001)_z// (001)_{α}, [010]_z // [010]_{α}. Prolonged thcrmal/creep exposure is accompanied by recrystallisation of the matrix and this orientation relationship is destroyed. Nevertheless Z phase particles preserve the form of thin plates. Z phase is a nitride which is rich in vanadium, niobium and chromium and its composition depends on both the temperature of precipitation and the initial chemical composition of steels. The composition of Z phase does not change during long term exposure at the original precipitation temperature. A relationship between the composition of Z phase and its temperature of formation may be able to be used as a temperature exposure indicator of steels. However it is also necessary to know the Z phase composition for a given cast of material.

  19. Boron effect on the microstructure of 9% Cr ferritic-martensitic steels

    Science.gov (United States)

    Klimenkov, M.; Materna-Morris, E.; Möslang, A.

    2015-07-01

    The microstructure of reduces-activation 9Cr-WTaV steel alloyed with 83 and 1160 wt. ppm 10B was detailed analysed using transmission electron microscopy. The influence of boron content on the precipitation behaviour of M23C6 and MX (VN and TaC) phases and, hence, on the formation process of steel's grain and lath structure was studied. VN precipitates, which play an important role in the stabilisation of the lath structure, exhibit most sensitive reaction on presence of boron. Their spatial density significantly reduces in the alloy with 83 ppm boron. In the steel with 1160 wt. ppm boron, no formation of VN was detected, whereas TaC particles precipitate at the lath and grain boundaries. These changes in the structure stabilisation mechanism lead to an increasing lath width and a decreasing thermal stability of laths and grains. Analytical investigations of several BN particles reveal their complex multi-phase structure and allow conclusions to be drawn with respect to their precipitation sequence.

  20. Martensite reversion and texture formation in 17Mn-0.06C TRIP/TWIP steel after hot cold rolling and annealing

    Directory of Open Access Journals (Sweden)

    Diana Pérez Escobar

    2015-04-01

    Full Text Available High Mn steels with Si and Al present great plasticity when deformed due to the TRIP/TWIP effect. This work evaluated the microstructural evolution and texture formation of a 17Mn-0.06C steel after hot rolling, cold rolling to 45% of thickness reduction and annealing at 700 °C for different times. The microstructural analysis was performed by means of dilatometry, X-ray diffraction (XRD, optical (OM and scanning electron microscopy (SEM, electron backscattering diffraction EBSD and transmission electron microscopy (TEM. It was found that during the cooling process, after the steel is annealed, the athermal ɛ and α′ martensites are formed. Tensile test results showed that the steel exhibits yield and tensile strength around 650 and 950 MPa with a total elongation around 45%. The austenite texture contains brass, copper and Goss components while the α′ and ɛ martensites textures contain rotated cube and prismatic and pyramidal fibers, respectively.

  1. Reduced Antivation Ferritic/Martensitic Steel Eurofer 97 as Possible Structural Material for Fusion Devices. Metallurgical Characterization on As-Received Condition and after Simulated Services Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, P.; Lancha, A. M.; Lapena, J.; Serrano, M.; Hernandez-Mayoral, M.

    2004-07-01

    Metallurgical Characterization of the reduced activation ferritic/martensitic steel Eurofer'97, on as-received condition and after thermal ageing treatment in the temperature range from 400 degree centigree to 600 degree centigree for periods up to 10.000 h, was carried out. The microstructure of the steel remained stable (tempered martensite with M{sub 2}3 C{sub 6} and MX precipitates) after the thermal ageing treatments studied in this work. In general, this stability was also observed in the mechanical properties. The Eurofer'97 steel exhibited similar values of hardness, ultimate tensile stress, 0,2% proof stress, USE and T{sub 0}3 regardless of the investigated material condition. However, ageing at 600 degree centigree for 10.000 ha caused a slight increase in the DBTT, of approximately 23. In terms of creep properties, the steel shows in general adequate creep rupture strength levels for short rupture times. However, the results obtained up to now for long time creep rupture tests at 500 degree centigree suggests a change in the deformation mechanisms. (Author) 62 refs.

  2. Impurity content of reduced-activation ferritic steels and a vanadium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Grossbeck, M.L.; Bloom, E.E. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    Inductively coupled plasma mass spectrometry was used to analyze a reduced-activation ferritic/martensitic steel and a vanadium alloy for low-level impurities that would compromise the reduced-activation characteristics of these materials. The ferritic steel was from the 5-ton IEA heat of modified F82H, and the vanadium alloy was from a 500-kg heat of V-4Cr-4Ti. To compare techniques for analysis of low concentrations of impurities, the vanadium alloy was also examined by glow discharge mass spectrometry. Two other reduced-activation steels and two commercial ferritic steels were also analyzed to determine the difference in the level of the detrimental impurities in the IEA heat and steels for which no extra effort was made to restrict some of the tramp impurities. Silver, cobalt, molybdenum, and niobium proved to be the tramp impurities of most importance. The levels observed in these two materials produced with present technology exceeded the limits for low activation for either shallow land burial or recycling. The chemical analyses provide a benchmark for the improvement in production technology required to achieve reduced activation; they also provide a set of concentrations for calculating decay characteristics for reduced-activation materials. The results indicate the progress that has been made and give an indication of what must still be done before the reduced-activation criteria can be achieved.

  3. Corrosion behavior of EUROFER steel in flowing eutectic Pb-17Li alloy

    Energy Technology Data Exchange (ETDEWEB)

    Konys, J. E-mail: juergen.konys@imf.fzk.de; Krauss, W.; Voss, Z.; Wedemeyer, O

    2004-08-01

    Reduced-activation-ferritic-martensitic (RAFM) steels are considered for application in fusion technology as structural materials. The alloy EUROFER 97 was developed on the basis of the experience gained with steels of the OPTIFER, MANET and F82H-mod. type. These alloys will be in contact with the liquid breeder Pb-17Li and their corrosion behavior is of significance for their successful application. Corrosion tests of EUROFER 97 in flowing Pb-17Li at 480 deg. C were performed up to about 12 000 h to evaluate the kinetics of the dissolution attack. The exposed samples were analysed by metallography and scanning electron microscopy (SEM) with EDX. The results show that EUROFER 97 is attacked by flowing liquid Pb-17Li with a flow velocity of about 0.3 m/s similar to the earlier examined steels and that the typical steel elements are dissolved. The observed attack is of uniform type with values of about 90 {mu}m/year. The corrosion rate is a somewhat smaller for EUROFER compared to the other RAFM steels but with equal activation energy.

  4. Cyclic softening as a parameter for prediction of remnant creep rupture life of a Indian reduced activation ferritic–martensitic (IN-RAFM) steel subjected to fatigue exposures

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Aritra, E-mail: aritra@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Vijayanand, V.D.; Shankar, Vani; Parameswaran, P.; Sandhya, R.; Laha, K.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Rajendrakumar, E. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India)

    2014-12-15

    Sequential fatigue-creep tests were conducted on Indian reduced activation ferritic–martensitic steel at 823 K leading to sharp decrease in residual creep life with increase in prior fatigue exposures. Extensive recovery of martensitic-lath structure taking place during fatigue deformation, manifested as cyclic softening in the cyclic stress response, shortens the residual creep life. Based on the experimental results, cyclic softening occurring during fatigue stage can be correlated with residual creep life, evolving in an empirical model which predicts residual creep life as a function of cyclic softening. Predicted creep lives for specimens pre-cycled at various strain amplitudes are explained on the basis of mechanism of cyclic softening.

  5. Mechanical properties of ferrite-perlite and martensitic Fe-Mn-V-Ti-C steel processed by equal-channel angular pressing and high-temeperature annealing

    Science.gov (United States)

    Zakharova, G. G.; Astafurova, E. G.; Tukeeva, M. S.; Naidenkin, E. V.; Raab, G. I.; Dobatkin, S. V.

    2011-09-01

    Using the method of equal-channel angular pressing (ECAP), submicrocrystalline structure is formed in lowcarbon Fe-Mn-V-Ti-C steel with the average grain size 260 nm in the ferrite-perlite state and 310 nm in the martensitic state. It is established that the ECAP treatment gives rise to improved mechanical properties (Hμ = 2.9 GPa, σ0 = 990 MPa in the ferrite-perlite and Hμ = 3.7 GPa, σ0 = 1125 MPa in martensitic states), decreased plasticity, and results in plastic flow localization under tensile loading. The high strength properties formed by the ECAP are shown to sustain up to the annealing temperature 500°C.

  6. Microstructure of Welded Joints of X5CrNiCuNb16-4 (17-4 PH Martensitic Stainlees Steel After Heat Treatment

    Directory of Open Access Journals (Sweden)

    Ziewiec A.

    2014-10-01

    Full Text Available The paper presents rezults of microstructure (LM, TEM investigation and hardness measurments of welded joints in martensitic precipitation hardened stainless steel containing copper, subjected to heat treatment. For the aging temperature up to 540 °C even for the very long times, the microstructure of the welded joints is similar to this one at lower temerature aging. After aging at 620 °C a distinct change of the microstructure was observed. Non-equilibrium solidification conditions of the weld metal, segregation and the diffusion of copper and the elements stablilizing the austenite cause the occurrence of the reverse transformation of the martensite into austenite as fast as just 1 hour at 620 °C. TEM investigations revealed the differences in dispersion of hardening copper precipitates after aging at temperature 620 °C for 1 and 4 hours.

  7. A study of corrosion electrochemical properties of martensite-austenite steel Cr15Ni6Mo

    Energy Technology Data Exchange (ETDEWEB)

    Cihal, V.; Hubackova, J.; Kubelka, J.; Mezanec, K.

    1985-11-01

    The steel Cr15Ni6Mo (UHB 119) exhibits a very satisfactory corrosion resistance. However, its superior passivating ability depends on the heat treatment method used. The use of two-step tempering leads primarily to an improved resistance to reactivation and optimum properties are achieved when the basic matrix contains about 40% stable austenite in fine form. This structural state requires the use of tempering temperatures from 625 to 650/sup 0/C in Step 1, and 525/sup 0/C in Step 2 of tempering.

  8. Erosion visualisation and characteristics of a two dimensional diffusion treated martensitic stainless steel hydrofoil

    Energy Technology Data Exchange (ETDEWEB)

    Mann, B.S. [Corporate R and D Division, Hyderabad (India). Materials Science Lab.

    1998-04-15

    Erosive wear of complicated water pump and hydro turbine blades is a complex problem. This is due mainly to the many variables involved in the erosive wear. These depend upon type and erodant, base material and flow conditions. In this paper, visualisation and prevention of erosive wear on two dimensional forged 12Cr and 13Cr-4Ni cast steel hydrofoils under flow conditions similar to that of hydroturbines and water pumps is described. An experimental study was taken using a rotating disc apparatus. From the study, it was observed that the erosion of complicated hydrofoils depends on the flow conditions, especially flow separation, reattachment and boundary layer growth. The visualisation of wear on the hydrofoils was obtained from the wear replicas which were etched on the aluminium rotating disc. Further, to control the wear of these hydrofoils, these were given a hard diffused layer based on boronizing. The performance of these hard diffused layers along with wear prediction on 12Cr and 13Cr-4Ni steel hydrofoils are reported in this paper. (orig.)

  9. Evaluation of Electrochemical Characteristics on Graphene Coated Austenitic and Martensitic Stainless Steels for Metallic Bipolar Plates in PEMFC Fabricated with Hydrazine Reduction Methods

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Seong-Yun; Lee, Jae-Bong [School of Advanced Materials Engineering, Kookmin University, Seoul (Korea, Republic of)

    2016-04-15

    Graphene was coated on austenitic and martensitic stainless steels to simulate the metallic bipolar plate of proton exchange membrane fuel cell (PEMFC). Graphene oxide (GO) was synthesized and was reduced to reduced graphene oxide (rGO) via a hydrazine process. rGO was confirmed by FE-SEM, Raman spectroscopy and XPS. Interfacial contact resistance (ICR) between the bipolar plate and the gas diffusion layer (GDL) was measured to confirm the electrical conductivity. Both ICR and corrosion current density decreased on graphene coated stainless steels. Corrosion resistance was also improved with immersion time in cathodic environments and satisfied the criteria of the Department of Energy (DOE), USA. The total concentrations of metal ions dissolved from graphene coated stainless steels were reduced. Furthermore hydrophobicity was improved by increasing the contact angle.

  10. Boron effect on the microstructure of 9% Cr ferritic–martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Klimenkov, M., E-mail: michael.klimenkov@kit.edu; Materna-Morris, E.; Möslang, A.

    2015-07-15

    Highlights: • Detailed TEM characterization of BN, M{sub 23}C{sub 6}, VN and TaC precipitates in B-alloyed EUROFER97. • Determination of B content influence on density and composition of M{sub 23}C{sub 6} and MX precipitates and herewith on microstructure. • α-Al{sub 2}O{sub 3}–BN–TaC–VN precipitation sequence of different phases during cooling was proposed. • Decreasing of thermal stability of microstructure with boron content was measured. - Abstract: The microstructure of reduces-activation 9Cr–WTaV steel alloyed with 83 and 1160 wt. ppm {sup 10}B was detailed analysed using transmission electron microscopy. The influence of boron content on the precipitation behaviour of M{sub 23}C{sub 6} and MX (VN and TaC) phases and, hence, on the formation process of steel’s grain and lath structure was studied. VN precipitates, which play an important role in the stabilisation of the lath structure, exhibit most sensitive reaction on presence of boron. Their spatial density significantly reduces in the alloy with 83 ppm boron. In the steel with 1160 wt. ppm boron, no formation of VN was detected, whereas TaC particles precipitate at the lath and grain boundaries. These changes in the structure stabilisation mechanism lead to an increasing lath width and a decreasing thermal stability of laths and grains. Analytical investigations of several BN particles reveal their complex multi-phase structure and allow conclusions to be drawn with respect to their precipitation sequence.

  11. Radiation induced segregation and precipitation behavior in self-ion irradiated Ferritic/Martensitic HT9 steel

    Science.gov (United States)

    Zheng, Ce; Auger, Maria A.; Moody, Michael P.; Kaoumi, Djamel

    2017-08-01

    In this study, Ferritic/Martensitic (F/M) HT9 steel was irradiated to 20 displacements per atom (dpa) at 600 nm depth at 420 and 440 °C, and to 1, 10 and 20 dpa at 600 nm depth at 470 °C using 5 MeV Fe++ ions. The characterization was conducted using ChemiSTEM and Atom Probe Tomography (APT), with a focus on radiation induced segregation and precipitation. Ni and/or Si segregation at defect sinks (grain boundaries, dislocation lines, carbide/matrix interfaces) together with Ni, Si, Mn rich G-phase precipitation were observed in self-ion irradiated HT9 except in very low dose case (1 dpa at 470 °C). Some G-phase precipitates were found to nucleate heterogeneously at defect sinks where Ni and/or Si segregated. In contrast to what was previously reported in the literature for neutron irradiated HT9, no Cr-rich α‧ phase, χ-phases, η phase and voids were found in self-ion irradiated HT9. The difference of observed microstructures is probably due to the difference of irradiation dose rate between ion irradiation and neutron irradiation. In addition, the average size and number density of G-phase precipitates were found to be sensitive to both irradiation temperature and dose. With the same irradiation dose, the average size of G-phase increased whereas the number density decreased with increasing irradiation temperature. Within the same irradiation temperature, the average size increased with increasing irradiation dose.

  12. Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

    Science.gov (United States)

    Thomas Paul, V.; Sudha, C.; Saroja, S.

    2015-08-01

    9Cr-Reduced Activation Ferritic-Martensitic steels with 1 and 1.4 wt pct tungsten are materials of choice for the test blanket module in fusion reactors. The steels possess a tempered martensite microstructure with a decoration of inter- and intra-lath carbides, which undergoes extensive modification on application of heat. The change in substructure and precipitation behavior on welding and subsequent thermal exposure has been studied using both experimental and computational techniques. Changes i.e., formation of various phases, their volume fraction, size, and morphology in different regions of the weldment due to prolonged thermal exposure was influenced not only by the time and temperature of exposure but also the prior microstructure. Laves phase of type Fe2W was formed in the high tungsten steel, on aging the weldment at 823 K (550 °C). It formed in the fine-grained heat-affected zone (HAZ) at much shorter durations than in the base metal. The accelerated kinetics has been understood in terms of enhanced precipitation of carbides at lath/grain boundaries during aging and the concomitant depletion of carbon and chromium and enrichment of tungsten in the vicinity of the carbides. Therefore, the fine-grained HAZ in the weldment was identified as a region susceptible for failure during service.

  13. Mechanical characteristics and microstructure of weld joint of high-temperature martensitic steel containing 9% Cr

    Science.gov (United States)

    Shakhova, Ya. E.; Belyakov, A. N.; Kaibyshev, R. O.

    2016-04-01

    The structure and mechanical characteristics of a weld joint of 10Kh9K3V2MFBR steel (0.097 C, 0.17.Si, 0.54 Mn, 8.75 Cr, 0.21 Ni, 0.51 Mo, 0.07 Nb, 0.23 V, 0.004 N, 0.003 B, 1.6 W, 0.15 Cu, and Fe for balance, wt %) have been studied; the joint was produced by hand welding in an argon atmosphere using 03Kh20N45M7G6B welding wire (0.3 C, 20 Cr, 45 Ni, 7 Mo, 6 Mn, and 1 Nb, wt %). The weld joint is divided into the zone of the base metal, a thermal effect zone, which consists of zones that contain fine and coarse original austenitic grains, and the zone of seam metal. It has been shown that the weld joint of 10Kh9K3V2MFBR steel possesses high strength characteristics at the room temperature under static loading and a satisfactorily impact toughness, which has the minimum value of 30 J/cm2 in the zone of the seam metal and does not depend on the temperature. With a decrease in the temperature from the room temperature to 253 K, a ductile-brittle transition occurs in the thermal effect zone. Creep tests carried out at the temperature of 923 K have shown that the long-term strength of the weld seam is lower than that of the base material in the entire stress range being tested. At stresses of 140 MPa or higher, the acceleration of creep in the weld seam is observed, while at low stresses of about 120 MPa, the rates of creep in the weld seam and in the base metal remain similar until the transition to the stage of accelerated fracture occurs. The difference in the values of the long-term strength is due to premature fracture, which occurs in the thermal effect zone with the finegrained structure.

  14. Corrosion Behavior of Surface-treated Ferritic/Martensitic Steel in Liquid Sodium Environment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, JeongHyeon; Lee, Jung Ki; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Shin, Sang Hun [KAERI, Daejeon (Korea, Republic of)

    2015-10-15

    Their compatibility with sodium is one of issues especially dissolution, chemical reaction, and carbon transfer with impurities, which degraded the mechanical properties. The compatibility of cladding and structural materials with sodium has to be carefully investigated, as sodium could promote corrosion of cladding and structural materials in two ways. One is produced by the dissolution of alloy constituents into the sodium, and the other is produced through a chemical reaction with impurities (especially oxygen and carbon) in the sodium environment. Gr.92 is known as compatible in sodium environment because this steel possesses excellent properties. For instance, Gr.92 has high creep and tensile strength, low thermal expansion coefficient. In the Ultra-long Cycle Fast Reactor (UCFR) which is developed in UNIST, however, cladding is exposed long-term in high temperature liquid sodium environment. So, it is very important to investigate the corrosion-related behavior such as surface corrosion rate, carburization, decarburization and mechanical properties for its operation time. In this study, as-received and surface-treated Gr.92 specimen in the oxygen-saturated liquid sodium were examined at high temperature for 300h. The impedance results reveal the information for the corrosion behavior in liquid sodium. Also, microstructure results reveal the information for the maintenance of coating and role of coating.

  15. Method of Evaluating Delayed Fracture Susceptibility of Tempered Martensitic Steel Showing Quasi-Cleavage Fracture

    Science.gov (United States)

    Matsumoto, Yu; Takai, Kenichi

    2017-02-01

    The difference in the hydrogen charging methods, immersion in a NH4SCN aqueous solution, and cathodic electrolysis in a NaOH aqueous solution, did not affect the hydrogen state present in the steel, but it did affect the surface state of the specimens through corrosion, causing fracture strength to fluctuate in tensile testes. As for stress application method, the fracture strength at lower crosshead speeds in tensile tests was consistent with that found for hydrogen precharging prior to stress application in CLTs as long as hydrogen charging was conducted by cathodic electrolysis. However, the fracture strength obtained with concurrent hydrogen charging without precharging prior to stress application in CLTs was higher than that with hydrogen precharging prior to stress application in CLTs regardless of the same hydrogen content. In other words, delayed fracture susceptibility was affected by the order of hydrogen charging and stress application for quasi-cleavage fracture associated with local plastic deformation, i.e., dislocation motion. Therefore, by taking into account the cathodic electrolysis in the NaOH solution, the low crosshead speed and the order of hydrogen charging and stress application, the fracture strength in CLTs, and tensile tests coincided with respect to quasi-cleavage fracture even though the stress application methods were different.

  16. Solution of an Inverse Problem of Heat Conduction of 45 Steel with Martensite Phase Transformation in High Pressure during Gas Quenching

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to simulate thermal strains, thermal stresses, residual stresses and microstructure of the steel during gas quenching by means of the numerical method, it is necessary to obtain an accurate boundary condition of temperature field. The surface heat transfer coefficient is a key parameter. The explicit finite difference method, nonlinear estimation method and the experimental relation between temperature and time during gas quenching have been used to solve the inverse problem of heat conduction. The relationship between surface temperature and surface heat transfer coefficient of a cylinder has been given. The nonlinear surface heat transfer coefficients include the coupled effects between martensitic phase transformation and temperature.

  17. Effect of chromium and molybdenum on corrosion resistance of super 13Cr martensitic stainless steel in CO{sub 2} environment

    Energy Technology Data Exchange (ETDEWEB)

    Amaya, Hisashi; Kondo, Kunio; Hirata, Hiroyuki [Sumitomo Metal Industries, Ltd., Amagasaki (Japan). Corporate R and D Labs.; Ueda, Masakatsu; Mori, Tomoki [Sumitomo Metal Industries, Ltd., Wakayama (Japan). Wakayama Steel Works

    1998-12-31

    The effect of Cr and Mo on the corrosion resistance of super 13Cr stainless steel in CO{sub 2} environment has been investigated by the electrochemical technique and the surface film analysis. The corrosion rate in CO{sub 2} environment at elevated temperatures is reduced with the increase in the effective Cr content. The pitting resistance is improved by the addition of more than 0.25 mass% Mo, because Mo is effective to stabilize the passive film in the CO{sub 2} environment. The effect of the Mo content on the SSC susceptibility in CO{sub 2} environment with a little amount of H{sub 2}S has been also studied. Mo is also effective to improve the SSC resistance by the formation of Mo sulfide in the outer layer of the surface film, because the Mo sulfide film can assist the formation and/or stabilization of the Cr oxide passive film in the inner layer even in the CO{sub 2} environment with a little amount of H{sub 2}S at room temperature. Based on these results, O.O1C-13Cr-5.2Ni-0.7Mo steel chemical compositions has been determined to improve the corrosion resistance of 13Cr martensitic stainless steel. The applicable environment of the developed steel will be discussed compared with super 13Cr stainless steel containing 2mass% Mo and conventional 13Cr steel.

  18. Laser-based welding of 17-4 PH martensitic stainless steel in a tubular butt joint configuration with a built-in backing bar

    Science.gov (United States)

    Ma, Junjie; Atabaki, Mehdi Mazar; Liu, Wei; Pillai, Raju; Kumar, Biju; Vasudevan, Unnikrishnan; Kovacevic, Radovan

    2016-08-01

    Laser-based welding of thick 17-4 precipitation hardening (PH) martensitic stainless steel (SS) plates in a tubular butt joint configuration with a built-in backing bar is very challenging because the porosity and cracks are easily generated in the welds. The backing bar blocked the keyhole opening at the bottom surface through which the entrapped gas could escape, and the keyhole was unstable and collapsed overtime in a deep partially penetrated welding conditions resulting in the formation of pores easily. Moreover, the fast cooling rate prompted the ferrite transform to austenite which induced cracking. Two-pass welding procedure was developed to join 17-4 PH martensitic SS. The laser welding assisted by a filler wire, as the first pass, was used to weld the groove shoulder. The added filler wire could absorb a part of the laser beam energy; resulting in the decreased weld depth-to-width ratio and relieved intensive restraint at the weld root. A hybrid laser-arc welding or a gas metal arc welding (GMAW) was used to fill the groove as the second pass. Nitrogen was introduced to stabilize the keyhole and mitigate the porosity. Preheating was used to decrease the cooling rate and mitigate the cracking during laser-based welding of 17-4 PH martensitic SS plates.

  19. Development of pseudoelasticity in Fe–10Ni–7Mn (wt%) high strength martensitic steel by intercritical heat treatment and subsequent ageing

    Energy Technology Data Exchange (ETDEWEB)

    Koohdar, H.R. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Nili-Ahmadabadi, M., E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Habibi-Parsa, M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Jafarian, H.R. [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran (Iran, Islamic Republic of)

    2015-01-05

    In this research, ternary Fe–10Ni–7Mn (wt%) high strength martensitic steel was subjected to study the reverse transformation of martensite to austenite by intercritical annealing at 600 °C in the ferritic–austenitic (α+γ) dual phase region for various holding times. Subsequent isothermal ageing was performed at 480 °C for 3.6 ks. The experimental results revealed that during intercritical annealing above the heating rate of 5 °C/s, reverse martensite transformation occurs by the diffusionless mechanism. Also, the X-ray diffraction (XRD) and electron back scattering diffraction (EBSD) analyses represented that the volume fraction of the retained austenite at room temperature increases with increasing the holding time up to 7.2 ks and then it gradually decreases. Furthermore, the cyclic tensile test results revealed pseudoelastic behavior of the retained austenite after subsequent ageing. The maximum amount of pseudoelasticity was obtained about 40% at the sixth loading–unloading cycle for the specimen intercritically annealed at 600 °C for 7.2 ks after subsequent isothermal ageing at 480 °C for 3.6 ks.

  20. Fine structure characterization of martensite/austenite constituent in low-carbon low-alloy steel by transmission electron forward scatter diffraction.

    Science.gov (United States)

    Li, C W; Han, L Z; Luo, X M; Liu, Q D; Gu, J F

    2016-11-01

    Transmission electron forward scatter diffraction and other characterization techniques were used to investigate the fine structure and the variant relationship of the martensite/austenite (M/A) constituent of the granular bainite in low-carbon low-alloy steel. The results demonstrated that the M/A constituents were distributed in clusters throughout the bainitic ferrite. Lath martensite was the main component of the M/A constituent, where the relationship between the martensite variants was consistent with the Nishiyama-Wassermann orientation relationship and only three variants were found in the M/A constituent, suggesting that the variants had formed in the M/A constituent according to a specific mechanism. Furthermore, the Σ3 boundaries in the M/A constituent were much longer than their counterparts in the bainitic ferrite region. The results indicate that transmission electron forward scatter diffraction is an effective method of crystallographic analysis for nanolaths in M/A constituents. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  1. Fabrication of 13Cr-2Mo Ferritic/Martensitic Oxide-Dispersion-Strengthened Steel Components by Mechanical Alloying and Spark-Plasma Sintering

    Science.gov (United States)

    Bogachev, I.; Grigoryev, E.; Khasanov, O. L.; Olevsky, E.

    2014-06-01

    The outcomes of the mechanical alloying of 13Cr-2Mo ferritic/martensitic steel and yttria (oxide-dispersion-strengthened steel) powders in a ball mill are reported in terms of the powder particle size and morphology evolution. The optimal ball mill rotation speed and the milling time are discussed. The densification kinetics of the mechanically alloyed powder during the process of spark-plasma sintering is analyzed. An optimal set of the compaction processing parameters, including the maximum temperature, the dwell time, and the heating rate, is determined. The specifics of the densification are discussed in terms of the impact of major spark-plasma sintering parameters as well as the possible phase transformations occurring during compaction processing.

  2. Constitutive modelling and identification of parameters of the plastic strain-induced martensitic transformation in 316L stainless steel at cryogenic temperatures

    CERN Document Server

    Garion, C; Sgobba, Stefano

    2006-01-01

    The present paper is focused on constitutive modelling and identification of parameters of the relevant model of plastic strain- induced martensitic transformation in austenitic stainless steels at low temperatures. The model used to describe the FCCrightward arrow BCC phase transformation in austenitic stainless steels is based on the assumption of linearization of the most intensive part of the transformation curve. The kinetics of phase transformation is described by three parameters: transformation threshold (p/sub xi/), slope (A) and saturation level (xi/sub L/). It is assumed that the phase transformation is driven by the accumulated plastic strain p. In addition, the intensity of plastic deformation is strongly coupled to the phase transformation via the description of mixed kinematic /isotropic linear plastic hardening based on the Mori-Tanaka homogenization. The theory of small strains is applied. Small strain fields, corresponding to phase transformation, are decomposed into the volumic and the shea...

  3. Modification and characterization of the AISI 410 martensitic stainless steels surface; Modificacao e caracterizacao da superficie do aco inoxidavel martensitico AISI 410

    Energy Technology Data Exchange (ETDEWEB)

    Bincoleto, A.V.L. [Universidade Federal de Sao Carlos (PPG-CEM/UFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Nascente, P.A.P. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    Steam turbines are used in the generation of more than half the electric energy produced in the world nowadays. It is important the study which aims to improve the efficiency by means of the optimization of leaks and of the aerodynamic profiles, as well as to maintain the integrity of the components. The martensitic stainless steels are widely employed due to the combination of their good mechanical properties with higher corrosion resistance. However, their lower wear resistance and their poor tribological behavior limit their use, since they decrease the component life time. In order to evaluate the improvement in the performance of the AISI 410 stainless steel, several process of surface modification were employed. Five samples were produced: the first one was not treated, the second one received liquid nitriding, the third, gas nitriding, the forth, thermal aspersion of tungsten carbide, and the fifth, boronizing. The samples were characterized by optical microscopy, surface microhardness, and X-ray diffractometry. (author)

  4. Effect of Tungsten on Long-Term Microstructural Evolution and Impression Creep Behavior of 9Cr Reduced Activation Ferritic/Martensitic Steel

    <