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Sample records for steel-cr16ni9mo2

  1. Development of improved HP/IP rotor material 2% CrMoNiWV (23 CrMoNiWV 88)

    International Nuclear Information System (INIS)

    Wiemann, W.

    1989-01-01

    The new 2% CrMoNiWV steel has a sufficient strength level, a very good creep (rupture) behaviour and an excellent toughness behaviour for a creep resistant steel. Even after long time high temperature exposure the toughness degradation is so small that it is still better than this of best 1% CrMo(Ni)V steels. The fatigue behaviour is well comparable to this of 1% CrMo(Ni)V. The 2% CrMoNiWV steel has the capability to substitute the traditional 1% CrMo(Ni)V. (orig.) With 26 annexes

  2. Quasicrystalline and crystalline precipitation during isothermal tempering in a 12Cr-9Ni-4Mo maraging stainless steel

    International Nuclear Information System (INIS)

    Liu, P.; Stigenberg, A.H.; Nilsson, J.O.

    1995-01-01

    A thorough microstructural investigation has been performed on a high strength maraging steel of the type 12%Cr-9%Ni-4%Mo-2%Cu-1%Ti. The major precipitate formed during isothermal aging at 475 C is a quasicrystalline phase possessing icosahedral symmetry termed R'-phase with a typical chemical composition of 48%Mo-33%Fe-13%Cr-2%Ni-4%Si. At 550 C the major precipitate is trigonal R-phase with a typical composition of 45%Mo-31%Fe-18%Cr-4%Ni-2%Si. At 550 C also Laves phase with a composition of 48%Mo-35%Fe-13%Cr-2%Ni-2%Si could be observed. At both 475 and 550 C an ordered phase termed L-phase precipitated. This minority phase has an ordered face centered cubic (f.c.c.) structure of type L1 0 . Its composition is typically 9%Fe-4%Cr-52%Ni-15%Mo.-16%Ti-4%Al. R'-phase formed at 475 C transformed to R-phase and Laves phase during aging at 550 C. In an analogous manner, R-phase and Laves phase formed at 550 C transformed to R'-phase during subsequent aging at 475 C. This transformation was rationalized by a strong similarity in crystal structure between quasicrystalline R'-phase of icosahedral symmetry and Frank-Kasper phases such as R-phase and Laves phase

  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

  4. Microstructural evolution in 13Cr-8Ni-2.5Mo-2Al martensitic precipitation-hardened stainless steel

    International Nuclear Information System (INIS)

    Ping, D.H.; Ohnuma, M.; Hirakawa, Y.; Kadoya, Y.; Hono, K.

    2005-01-01

    The microstructure of 13Cr-8Ni-2.5Mo-2Al martensitic precipitation-hardened (PH) stainless steel has been investigated using transmission electron microscopy, three-dimensional atom probe and small-angle X-ray scattering. A high number density (∼10 23-25 m -3 ) of ultra-fine (1-6 nm) β-NiAl precipitates are formed during aging at 450-620 deg. C, which are spherical in shape and dispersed uniformly with perfect coherency with the matrix. As the annealing temperature increases, the size and concentration of the precipitates increase concurrently while the number density decreases. The Mo and Cr segregation to the precipitate-matrix interface has been detected and is suggested to suppress precipitate coarsening. In the sample aged for 500 h at 450 deg. C, the matrix decomposes into Cr-rich (α') and Cr-poor (α) regions. The decrease in the strength at higher temperature (above 550 deg. C) is attributed to the formation of larger carbides and reverted austenite

  5. Precipitation hardening in a 12%Cr-9%Ni-4%Mo-2%Cu stainless steel

    International Nuclear Information System (INIS)

    Haettestrand, Mats; Nilsson, Jan-Olof; Stiller, Krystyna; Liu Ping; Andersson, Marcus

    2004-01-01

    A combination of complementary techniques including one-dimensional and three-dimensional atom probe, energy-filtered transmission electron microscopy and conventional transmission electron microscopy has been used to assess the precipitation reactions at 475 deg. C in a 12%Cr-9%Ni-4%Mo-2%Cu precipitation hardening stainless steel. The continuous hardening up to at least 1000 h of ageing was attributed to a sequence of precipitation reactions involving nickel-rich precipitates nucleating at copper clusters followed by molybdenum-rich quasicrystalline precipitates and nickel-rich precipitates of type L1 0 . An estimate of the relative contributions to the strength increment during tempering based on measurements of particle densities was performed. Nickel-rich precipitates were found to play the most important role up to about 40 h of ageing after which the effect of quasicrystalline particles became increasingly important

  6. Mechanical properties of steel 8 CrMoNiNb 9 10 in dependence on the microstructural condition

    International Nuclear Information System (INIS)

    Fabritius, H.; Schnabel, E.

    1976-01-01

    Tension tests at room temperature to 600 0 C and creep-rupture tests at 500 to 600 0 C lasting up to about 75,000 h on two casts of steel 8 CrMoNiNb 9 10 with about 0.08% C, 0.3% Si, 0.7% Mn, 0.012% N, 0.005% Al, 2.34% Cr, 0.95% Mo, 0.8% Nb and 0.64% Ni in bainitic and ferritic microstructural condition. Influence of annealing at 650 to 800 0 C on the properties in the tension test. Influence of aging at 500 to 600 0 C lasting up to 30,000 h with and without mechanical stress on the properties in the tension test at aging temperature and on the toughness behaviour in the notched bar impact bend test at room temperature. (orig.) [de

  7. Substitution of modified 9 Cr-1 Mo steel for austentic stainless steels

    International Nuclear Information System (INIS)

    Sikka, V.K.

    1982-04-01

    This report describes the current program to develop a high-strength ferritic-martensitic steel. The alloy is essentially Fe-9% Cr-1% Mo with small additions of V and Nb and is known as modifed 9 Cr-1 Mo steel. Its elevated-temperature properties and design allowable stresses match those of type 304 stainless steel for temperatures up to 600 0 C and exceed those of other ferritic steels by factors of 2 to 3. The improved strength of this alloy permits its use in place of stainless steels for many applications

  8. Fatigue resistance of Cr-Ni-Mo-V steel

    International Nuclear Information System (INIS)

    Naumchenkov, N.E.; Filimonova, O.V.; Borisov, I.A.

    1985-01-01

    A study was made on the effect of additional alloying (Ni, Ni+Co), stress concentration, surface plastic strain on fatigue resistance of rotor steel of Cr-Ni-Mo-V-composition. It is shown that the steel with decreased carbon content possesses high complex of mechanical properties. Fatigue characteristics are not inferior to similar characteristics of steels of 25KhN3MFA type. Additional alloying of the steel containing 0.11...0.17% C and 4.5...4.7% N:, with niobium separately or niobium and cobalt in combination enabled to improve fatigue resistance of samles up to 25%. Strengthening of stress concentration zones by surface plastic strain is recommended for improving rotor suppporting 'nower under cyclic loading

  9. Microstructural Characterization of Clad Interface in Welds of Ni-Cr-Mo High Strength Low Alloy Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hong-Eun; Kim, Min-Chul; Lee, Ho-Jin; Kim, Keong-Ho [KAERI, Daejeon (Korea, Republic of); Lee, Ki-Hyoung [KAIST, Daejeon (Korea, Republic of); Lee, Chang-Hee [Hanyang Univ., Seoul (Korea, Republic of)

    2011-08-15

    SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at 610°C for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.

  10. Microstructural Characterization of Clad Interface in Welds of Ni-Cr-Mo High Strength Low Alloy Steel

    International Nuclear Information System (INIS)

    Kim, Hong-Eun; Kim, Min-Chul; Lee, Ho-Jin; Kim, Keong-Ho; Lee, Ki-Hyoung; Lee, Chang-Hee

    2011-01-01

    SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at 610°C for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.

  11. Optimizing Heat Treatment Process of Fe-13Cr-3Mo-3Ni Martensitic Stainless of Steel

    Science.gov (United States)

    Anwar, M. S.; Prifiharni, S.; Mabruri, E.

    2017-05-01

    The Fe-13Cr-3Mo-3Ni stainless steels are modified into martensitic stainless steels for steam turbine blades application. The working temperature of steam turbine was around 600 - 700 °C. The improvement properties of turbine blade material is necessary to maintain steam turbine work. The previous research revealed that it has corrosion resistance of Fe-13Cr-3Mo-3Ni which is better than 13Cr stainless steels in the chloride environment. In this work, the effect of heat treatment on microstructure and hardness of Fe-13Cr-3Mo-3Ni stainless steels has been studied. The steel was prepared by induction melting followed by hot forging. The steels were austenitized at 1000, 1050, and 1100 °C for 1 hour and were tempered at 600, 650, and 700 °C for 1 hour. The steels were then subjected to metallographic observation and hardness test of Rockwell C. The optimal heat treatment of Fe-13Cr-3Mo-3Ni was carried out austenitized in 1050 °C and tempered in 600 - 700 °C.

  12. Creep Rupture Analysis and Life Estimation of 1.25Cr-0.5Mo, 2.25Cr-1Mo and Modified 9Cr-1Mo Steel: A Comparative Study

    Science.gov (United States)

    Roy, Prabir Kumar

    2018-04-01

    This paper highlights a comparative assessment of creep life of 1.25Cr-0.5Mo, 2.25Cr-1Mo and modified 9Cr-1Mo steels based on accelerated creep rupture tests. Creep rupture test data have been analysed and creep life of the above mentioned materials have been assessed using Larson Miller parameter at the stress levels of 60 and 42 MPa for different temperatures. Limiting steam temperatures for minimum design life of 105 h at 42 and 60 MPa for the above mentioned steels have also been calculated. Microstructural studies for the three above mentioned steels are also done.

  13. Improved hardness of laser alloyed X12CrNiMo martensitic stainless steel

    CSIR Research Space (South Africa)

    Adebiyi, DI

    2011-07-01

    Full Text Available The improvement in hardness of X12CrNiMo martensitic stainless steel laser alloyed with 99.9% pure titanium carbide, stellite 6 and two cases of premixed ratio of titanium carbide and stellite 6 [TiC (30 wt.%)- stellite 6 (70 wt.%) and TiC (70 wt...

  14. Impact behavior of 9-Cr and 12-Cr ferritic steels after low-temperature irradiation

    International Nuclear Information System (INIS)

    Klueh, R.L.; Vitek, J.M.; Corwin, W.R.; Alexander, D.J.

    1987-01-01

    Miniature Charpy impact specimens of 9Cr-1MoVNb and 12Cr-1MoVW steels and these steels with 1 and 2% Ni were irradiated in the High-Flux Isotope Reactor (HFIR) at 50 0 C to displacement damage levels of up to 9 dpa. Nickel was added to study the effect of transmutation helium. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT). The 9Cr-1MoVNb steels, with and without nickel, showed a larger shift than the 12Cr-1MoVW steels, with and without nickel. The results indicated that helium also increased the DBTT. The same steels were previously irradiated at higher temperatures. From the present and past tests, the effect of irradiation temperature on the DBTT behavior can be evaluated. For the 9Cr-1MoVNb steel, there is a continuous decrease in the magnitude of the DBTT increase up to an irradiation temperature of about 400 0 C, after which the shift drops rapidly to zero at about 450 0 C. The DBTT of the 12Cr-1MoVW steel shows a maximum increase at an irradiation temperature of about 400 0 C and less of an increase at either higher or lower irradiation temperatures

  15. Welded joint properties of steel 2.25Cr1MoNiNb

    International Nuclear Information System (INIS)

    Gladis, R.; Ivanek, J.; Gottwald, M.

    1981-01-01

    Welded joints of steel 08Cr2.25Mo1NiNb for fast reactor steam generators made using manual arc welding with electrodes of identical compositions attain short-term mechanical properties and times to fracture when creep tested that match those of the base material. The reduction of the carbidic phase content in the steel and the welded joint metal did not adversely affect the tensile properties of the welded joint while increasing notch toughness of the heat-affected zone. Reduced carbon and niobium contents in the steel and the welded joint resulted in significant reduction in the proportion of carbidic eutectic particles in both the heat-affected zone and the weld metal. (Ha)

  16. The integrity of 9Cr-1Mo to stainless steel transition joints in AGR steam generators

    International Nuclear Information System (INIS)

    James, D.W.; Neumann, P.; Soo, J.

    1982-01-01

    The metallurgical aspects of the transition joint between 9Cr-1Mo and 316 stainless steel boiler tube sections are reviewed. A large minimum superheat margin (106 0 C) between the dryout zone and the 9Cr-1Mo to stainless steel transition joint was specified in the original design to eliminate the risk of wetting the stainless steel which is susceptible to stress corrosion cracking. However, small defects were discovered in the welds between the 9Cr-1Mo and Sanicro (72%Ni-16%Cr-10%Fe) transition piece, resulting from dilution of the weld pool by nickel from the transition piece. This led to the possibility of weld failure as a result of creep crack growth in service, and any significant reduction in operating temperature would mean that the large superheat margin could not be sustained. The creep properties of the joints, together with the transition joint temperature distribution, enabled tube failure rates to be determined as a function of operating temperature. A probabilistic model was developed so that the transition joint could be operated within a temperature 'window', the lower temperature limit being determined by stress corrosion considerations and the upper limit being set by creep rate limitations. This allows full load performance from the boilers throughout the anticipated life of the plant. (author)

  17. The research of axial corrosion fatigue on 10Ni3CrMoV steel

    Science.gov (United States)

    Xie, Xing; Yi, Hong; Xu, Jian; Xie, Kun

    2017-09-01

    Fatigue life had been studied with 10CrNi3MoV steel at different load ratios and in different environmental medias. The microstructure and micro-topography had been observed and analyzed by means of SEM, EDS and TEM. Our findings indicated that, the fatigue life of 10Ni3CrMoV steel in seawater was shorter than in air, the difference in longevity was larger with the decreasing of axis stress. Corrosion pits had a great influence on corrosion fatigue life.

  18. A Weakest-Link Approach for Fatigue Limit of 30CrNiMo8 Steels (Preprint)

    Science.gov (United States)

    2011-03-01

    34Application of a Weakest-Link Concept to the Fatigue Limit of the Bearing Steel Sae 52100 in a Bainitic Condition," Fatigue and Fracture of...AFRL-RX-WP-TP-2011-4206 A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) S. Ekwaro-Osire and H.V. Kulkarni Texas...2011 4. TITLE AND SUBTITLE A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT

  19. Alloying effect on hardening of martensite stainless steels of the Fe-Cr-Ni and Fe-Cr-Co systems

    International Nuclear Information System (INIS)

    Fel'dgandler, Eh.G.; Savkina, L.Ya.

    1975-01-01

    The effect of alloying elements is considered on the γ → a-transformation and hardening of certain compositions of the ternary Fe-Cr-Ni- and Fe-Cr-Co alloy systems with the martensite structure. In martensite Fe-(10 to 14)% Cr base steels the elements Co, Cu, W, Ni, Mo, Si, Cr decrease, Mn, Si, Mo, Cu increase, and Cr, Ni, Co decrease the temperature of α → γ-transition. The tempering of martensite steels of the Fe-Cr-Ni- and Fe-Cr-Co-systems containing 10 to 14% Cr, 4 to 9% Ni, and 7 to 12% Co does not lead to hardening. Alloyage of the martensite Fe-Cr-Ni-, Fe-Cr-Co- and Fe-Cr-Ni-Co base separately with Mo, W, Si or Cu leads to a hardening during tempering, the hardening being the higher, the higher is the content of Ni and, especially, of Co. The increase in the content of Mo or Si produces the same effect as the increase in the Co content. In on Fe-Cr-Co or Fe-Cr-Ni-Co based steels alloyed with Mo or Si, two temperature ranges of ageing have been revealed which, evidently, have different hardening natures. The compositions studied could serve as the base material for producing maraging stainless steels having a complex variety of properties

  20. Effects of Bond Coating on NiCrBSi-Mo Composite Functional Coating Properties in Plasma Spraying NiCrBSi-Mo/Ni Coating

    OpenAIRE

    DU Ji-yu; LI Fang-yi; LU Hai-yang; SHANG Jian-tong; LI Zhen

    2017-01-01

    Nickel-based bond coating and composite functional coating were sprayed on leaf blade steel material FV520B successively by using air plasma spraying system. NiCrBSi-Mo powder deposition rate, coating porosity, bonding strength and surface hardness were tested. The results indicate that, for the NiCrBSi-Mo/Ni coating, bond coating with 180-220μm thickness can improve NiCrBSi-Mo powder deposition rate while the surface coating with lower porosity, higher bonding strength and high hardness is p...

  1. Effect of heat treatment on workability of Cr-Ni-Mo steels

    International Nuclear Information System (INIS)

    Barcal, J.; Macek, K.

    1988-01-01

    The workability was studied of the new development generation of hardenable martensite Cr-Ni-Mo steels of the 10-10-2 and 6-11-3 types whose application is envisaged in future in nuclear engineering. Attention is paid to identification of inclusions and the phase analysis ofthe structure with respect to heat treatment and steel type. Face milling was used in the test of workability. In addition, tensile strength and impact bending strength testing was performed. The results showed that steel of the 6-11-3 type in the quenched condition was best workable. However, this steel showed a significant reduction in workability when in the hardened condition. Reduced workability can also be presumed for type 10-10-2 steel in the hardened condition when life is considered. Microstructure changes leading to softening of steel by aging had a favourable effect on workability, especially in steels of the 10-10-2 type. Hardened steels of the 6-11-3 type are recommended to be re-quenched. (Z.M.). 7 figs., 3 tabs., 9 refs

  2. Development of banded microstructure in 34CrNiMo6 steel

    Directory of Open Access Journals (Sweden)

    A. Nagode

    2016-07-01

    Full Text Available In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS, which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT diagrams of steel were calculated. They confirmed the formation of martensite in positive segregations and the formation of bainite in negative segregations.

  3. Welding and corrosion resistance of the new nitrogen alloyed steel X2 CrNiMnMoN241764

    International Nuclear Information System (INIS)

    Arit, N.; Henser, H.; GroB, V.

    1994-01-01

    Remanit 4565 S is a new developed nitrogen alloyed austenitic stainless steel. Characteristic features are: improved strength and toughness, delayed precipitation of carbides and intermetallic phases, improved corrosion resistance. Welding fabrication is possible without the risk of pore formation. TIG-welded joints are as resistant as the base metal, using filler metal SG-NiCr 20 Mo 15 (Thermanit Nimo C) respectively SG-NiCr 28 Mo(Thermanit 30/40 E) according to the area of application. (Author) 8 refs

  4. Characteristics of centrifugally cast GX25CrNiSi18-9 steel

    Directory of Open Access Journals (Sweden)

    R. Zapała

    2011-07-01

    Full Text Available The paper presents the results of microstructural examinations of the industrial heat-resistant centrifugally cast GX25CrNiSi18-9 steel characterised by increased content of Cu. The study included changes in the microstructure of base cast steel respective of the steel held at a temperature of 900 and 950°C for 48 hours. Based on the results obtained, an increase in microhardness of the examined cast steel matrix with increasing temperature was stated, which was probably caused by fine precipitates enriched in Cr, Mo, and C forming inside the matrix grains.The layer of scale formed on the tested cast steel oxidised in the atmosphere of air at 900 and 950°C was characterised by an increased tendency to degradation with increasing temperature of the conducted tests.

  5. The effects of minor alloy modifications and heat treatment on the microstructure and creep rupture behavior of 2.25Cr-1Mo Steel

    International Nuclear Information System (INIS)

    Todd, J.A.; Chung, D.W.; Parker, E.R.

    1983-01-01

    The effects of alloy additions on the microstructure of simulated cooled and tempered 2.25Cr-1Mo steels have been studied using transmission electron microscopy. Carbide precipitation sequences have been identified in the modification 3Cr-1Mo-1Mn-1Ni and compared to those in 2.25Cr-1Mo steels modified with Mn and Ni and also with Ti, V and B. The influence of minor compositional changes on the creep rupture behavior of 2.25Cr-1Mo steel has been studied at 500 C, 560 C, and 600 C. The most significant effect of alloy modifications on creep properties resulted from additions of Mn and Cr. Preliminary studies show that 1% Mn and 0.5Mn + 1Ni + 0.75Cr additions significantly reduce creep strength at all three temperatures for tests up to 2000 hours duration. The 3Cr-1Mo-1Mn-1Ni steel showed improvements in rupture ductility at all temperatures when compared with the base 2.25Cr-1Mo steel and the manganese-nickel modifications. Plots of the Larson-Miller parameter for both these modifications lay within the scatter band for commercial 2.25Cr-1Mo steels

  6. Investigation of Cr-Ni duplex stainless steel

    International Nuclear Information System (INIS)

    Lu Shiying

    1985-01-01

    At temperatures of 450 - 750 0 C, a laminate-shaped intermetallic phase Fe3Cr3Mo2Si2 has been observed. Intergranular brittle fracture is due to the precipitation of the Fe3Cr3Mo2SI2 phase, but quasi-cleavage fracture is connected with the precipitation of chi and σ phases. The formation of chi and σ during aging at 750 - 900 0 C results in a drastic decrease of the SCC resistance of Cr18Ni5 steel. In order to avoid a fully ferritic microstructure in Cr18Ni5 duplex steel after heating at high temperature or welding, the K value must be kept to 0.42 for thin wall tube. The decrease in SCC resistance after cold deformation is not due to the formation of strain-induced martensite but is connected with significant reduction in the resistance to pitting corrosion. (author)

  7. Influence of Normalizing Temperature on the Microstructure and Hardness of 9Cr-1Mo ODS Steel

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Ki Nam; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Kyu Tae [Dongguk University, Gyeongju (Korea, Republic of)

    2016-10-15

    Oxide dispersion strengthened(ODS) steel has superior high-temperature strength and creep properties because fine oxide particles having an excellent stability at high temperatures are uniformly distributed in the matrix. ODS steel has being developed for structure materials of sodium fast cooled reactor(SFR) because of its excellent irradiation resistance and mechanical properties. 9Cr-1Mo ODS steel has better high temperature strength and irradiation resistance than common 9Cr-1Mo steel because Y{sub 2}O{sub 3} nano-sized particles which interrupt dislocation movement and grain boundary slip are uniformly dispersed in the martensite matrix. The mechanical properties of the ODS steels are mainly determined by their microstructures, and the microstructure is considerably decided by the heat-treatment conditions. This study focused on the effect of normalizing temperature on microstructure and hardness of 9Cr-1Mo martensitic ODS steel so as to optimize the heat-treatment condition. In this study, the effect of normalizing temperature on mechanical property and microstructures of 9Cr-1Mo martensitic ODS steel was investigated. It was shown that the microhardness was steadily increased with increasing of the normalizing temperature. According to TEM observation, mechanical property of 9Cr-1Mo ODS steel was significantly affected by lath width. These observations, could be useful to understand the relationship between normalizing temperature and microstructure.

  8. Creep-fatigue-environment interaction of 9Cr-1Mo-V-Nb steel

    International Nuclear Information System (INIS)

    Shibata, Hiroyuki; Ishikawa, Akiyoshi; Asada, Yasuhide

    1996-01-01

    An extension of the creep-fatigue damage model has been conducted in the present study. The original damage model has been developed to the predict the creep-fatigue life of 9Cr-1Mo-V-Nb steel (Modified 9Cr-1Mo steel) in a very high vacuum environment. The present study is to extend an applicability of the model to the creep-fatigue damage accumulation in the air environment. (orig.)

  9. Void formation and helium effects in 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated in HFIR and FFTF at 400/degree/C

    International Nuclear Information System (INIS)

    Maziasz, P.J.; Klueh, R.L.

    1988-01-01

    Martensitic/ferritic 9Cr-1MoVNb and 12Cr-1MoVW steels doped with up to 2 wt% Ni have up to 450 appm He after HFIR irradiation to /approximately/38 dpa, but only 5 appm He after 47 dpa in FFTF. No fine He bubbles and few or no larger voids were observable in any of these steels after FFTF irradiation at 407/degree/C. By contrast, many voids were found in the undoped steels (30-90 appm He) irradiated in HFIR at 400/degree/C, while voids plus many more fine He bubbles were found in the Ni-doped steels (400-450 appm He). Irradiation in both reactors at /approximately/400/degree/C produced significant changes in the as-tempered lath/subgrain boundary, dislocation, and precipitation structures that were sensitive to alloy composition, including doping with Ni. However, for each specific alloy the irradiation-produced changes were exactly the same comparing samples irradiated in FFTF and HFIR, particularly the Ni-doped steels. Therefore, the increased void formation appears solely due to the increased helium generation found in HFIR. While the levels of void swelling are relatively low after 37-39 dpa in HFIR (0.1-0.4%), details of the microstructural evolution suggest that void nucleation is still progressing, and swelling could increase with dose. The effect of helium on void swelling remains a valid concern for fusion application that requires higher dose experiments. 15 refs., 14 figs., 8 tabs

  10. Stress-controlled inelastic behavior of modified 9 Cr-1 Mo steel at elevated temperatures

    International Nuclear Information System (INIS)

    Taguchi, Kosei.

    1989-01-01

    Interest in the ferritic steels of higher chromium concentration has increased recently because of an economical combination of mechanical and corrosion properties at elevated temperatures. A modified 9 Cr-1 Mo ferritic steel, developed in the United States, has been expected as an alternative structural material for fast breeder reactor components, in which Type 304 stainless steel or 2.25 Cr-1 Mo steel is currently used. For application of this material to the structural components, a lot of work has been done to develop evaluation methods for the deformation behavior and strength properties. The authors have studied the inelastic behavior and the creep-fatigue properties of modified 9 Cr-1 Mo steel at elevated temperatures, and proposed a constitutive equation and a creep-fatigue damage equation based on the overstress concept. In this paper, the applicability is discussed of the constitutive equation to stress-controlled inelastic behavior, such as creep strain hardening and stress cycling

  11. Effect of Cavitation on Surface Damage of 16.7Cr-10Ni-2Mo Stainless Steel in Marine Environment

    Energy Technology Data Exchange (ETDEWEB)

    Chong, Sang-Ok; Han, Min-Su; Kim, Seong-Jong [Mokpo National Maritime University, Mokpo (Korea, Republic of)

    2015-10-15

    Stainless steel is generally known to have characteristics of excellent corrosion resistance and durability, but in a marine environment it can suffer from localized corrosion due to the breakdown of passivity film due to chloride ion in seawater. Furthermore, the damage behaviors are sped up under a cavitation environment because of complex damage from electrochemical corrosion and cavitation-erosion. In this study the characteristics of electrochemical corrosion and cavitation erosion behavior were evaluated on 16.7Cr-10Ni-2Mo stainless steel under a cavitation environment in natural seawater. The electrochemical experiments have been conducted at both static conditions and dynamic conditions inducing cavitation with different current density parameters. The surface morphology and damage behaviors were compared after the experiment. After the cavitation test with time variables morphological examinations on damaged specimens were analyzed by using a scanning electron microscope and a 3D microscope. the galvanostatic experiment gave a cleaner surface morphology presented with less damage depth at high current density regions. It is due to the effect of water cavitation peening under the cavitation condition. In the cavitation experiment, with amplitude of 30 μm and seawater temperature of 25 ℃, weight loss and cavitation-erosion damage depth were dramatically increased after 5 hours inducing cavitation.

  12. Characteristics of Modified 9Cr-1Mo Steel for Reactor Pressure Vessel of Very High Temperature Gas Cooled Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Ho; Ryu, W. S.; Han, Chang Hee; Yoon, J. H.; Chang, Jong Hwa

    2004-11-15

    Many researches and developments have been progressed for the construction of VHTR by 2020 in Korea. Modified 9Cr-1Mo steel has been receiving attention for the application to the reactor pressure vessel material of VHTR. We collected and analyzed the research data for modified 9Cr-1Mo steel in order to understand the characteristics of modified 9Cr-1Mo steel. The modified 9Cr-1Mo steel is a modified alloy system similar to conventional 9Cr-1Mo grade ferritic steel. Modifications include additions of vanadium, niobium, and nitrogen, as well as lower carbon content. In this report, we summarized the change of microstructure and mechanical properties after tempering, thermal aging, and irradiation. Modified 9Cr-1Mo steel has high strength and thermal conductivity, low thermal expansion, and good resistance to corrosion. But the irradiation embrittlement behavior of modified 9Cr-1Mo steel should be evaluated and the evaluation methodology also should be developed. At the same time, the characteristics of weldment which is the weak part in pressure vessel should be evaluated.

  13. Microstructure-strength relations in a hardenable stainless steel with 16 pct Cr, 1.5 pct Mo, and 5 pct Ni

    Science.gov (United States)

    Grobner, P. J.; Blšs, V.

    1984-07-01

    Metallographic studies have been conducted on a 0.024 pct C-16 pct Cr-1.5 pct Mo-5 pct Ni stainless steel to study the phase reactions associated with heat treatments and investigate the strengthening mechanisms of the steel. In the normalized condition, air cooled from 1010 °C, the microstructure consists of 20 pct ferrite and 80 pct martensite. Tempering in a temperature range between 500 and 600 °C results in a gradual transformation of martensite to a fine mixture of ferrite and austenite. At higher tempering temperatures, between 600 and 800 °C, progressively larger quantities of austenite form and are converted during cooling to proportionally increasing amounts of fresh martensite. The amount of retained austenite in the microstructure is reduced to zero at 800 °C, and the microstructure contains 65 pct re-formed martensite and 35 pct total ferrite. Chromium rich M23C6 carbides precipitate in the single tempered microstructures. The principal strengthening is produced by the presence of martensite in the microstructure. Additional strengthening is provided by a second tempering treatment at 400 °C due to the precipitation of ultrafine (Cr, Mo) (C,N) particles in the ferrite.

  14. Irradiation hardening of Mod.9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Ryu, Woo-Seog; Kim, Sung-Ho; Choo, Kee-Nam; Kim, Do-Sik

    2009-01-01

    An irradiation test of Mod.9Cr-1Mo steel was carried out in the OR5 test hole of HANARO of a 30 MW thermal power at 390±10degC up to a fast neutron fluence of 4.4x10 19 (n/cm 2 ) (E > 1.0 MeV). The dpa of the irradiated specimens was evaluated to be 0.034 - 0.07. Tensile and impact tests of the irradiated Mod.9Cr-1Mo were done in the hot cell of the IMEF. The change of the tensile strength by irradiation was similar to the change of the yield strength. The increase of the yield and tensile strengths was up to 18% and 10% respectively. The elongation reduction of the weldment was up to 65%. (author)

  15. Soft zone formation in dissimilar welds between two Cr-Mo steels

    International Nuclear Information System (INIS)

    Albert, S.K.; Gill, T.P.S.; Tyagi, A.K.; Mannan, S.L.; Rodriguez, P.; Kulkarni, S.D.

    1997-01-01

    Two dissimilar weldments between 9Cr-1Mo and 2.25Cr-1Mo ferritic steels have been characterized for their microstructural stability during various postweld heat treatments (PWHTs). The samples for the investigation were extracted from bead-on-plate weldments made by depositing 2.25Cr-1Mo weld metal on 9Cr-1Mo base plate and vice versa. Subsequent application of PWHT resulted in the formation of a soft zone in the low Cr ferritic steel weld or base plate. A carbide-rich hard zone, adjoining the soft zone, was also detected in the high Cr side of the weldment. Unmixed zones in the weld metal provided additional soft and hard zones in the weld metals. The migration of carbon from low-Cr steel to high-Cr steel, driven by the carbon activity gradient, has been shown to be responsible for the formation of soft and hard zones. A carbon activity diagram for 2.25Cr-1Mo/9Cr-1Mo weldments has been proposed to aid in the selection of welding consumables for reducing or preventing the soft zone formation

  16. Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

    Science.gov (United States)

    Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup

    2016-04-01

    Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

  17. Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds.

    Science.gov (United States)

    Song, Wei; Liu, Xuesong; Berto, Filippo; Razavi, S M J

    2018-04-24

    The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2⁻1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

  18. Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds

    Directory of Open Access Journals (Sweden)

    Wei Song

    2018-04-01

    Full Text Available The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2–1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

  19. Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

    International Nuclear Information System (INIS)

    Rodak, Kinga; Hernas, Adam; Vodarek, Vlastimil

    2015-01-01

    Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M 23 C 6 carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

  20. Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, Kinga; Hernas, Adam [Silesian Univ. of Technology, Inst. of Materials Science, Katowice (Poland); Vodarek, Vlastimil [VSB-Technical Univ. of Ostrava (Czech Republic)

    2015-07-15

    Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M{sub 23}C{sub 6} carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

  1. Hydrogen effect on different melts of steel 03Cr10Ni10Mo2(Ti,Al)

    International Nuclear Information System (INIS)

    Hruby, J.; Novosad, P.; Axamit, R.

    1984-01-01

    The effect of hydrogen on martensitic 03Cr10Ni10Mo2(Ti,Al) steel was studied following vacuum induction melting and electroslag remelting with and without the effect of radiation. Under the influence of hydrogen and under the same parameters of catodic hydrogen charging of steel after vacuum induction melting shows a 20 - 30% reduction in total ductility. Steels after electroslag remelting show a higher reduction in total ductility - within the range of 26 - 33%, i.e., 33 - 43% for different melts, and contraction Z shows a reduction of 23 - 59%. Electroslag remelted steels show a greater reduction in plasticity owing to hydrogen than steels melted in vacuum induction furnaces. The reduction of the yield point and the breaking strength owing to hydrogen are more explicit than in steel after vacuum melting. In non-irradiated hydrogenated samples a higher yield point was evident. (B.S.)

  2. Evaluation of dynamic fracture toughness of cold worked 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Sathyanarayanan, S.; Sasikala, G.; Ray, S.K.

    2004-01-01

    Dynamic J-R curves for cold worked 9Cr-1Mo steel have been estimated from instrumented impact test data at ambient temperature on pre-cracked Charpy specimens using three methods of analysis, namely those by Ray et al., Schindler, and Sreenivasan and Mannan. It is concluded that of these three, Schindler's method is the best suited for the purpose since it gives consistent variations with cold work of dynamic J-R curves and dynamic fracture toughness. Cold work results in substantial degradation in dynamic fracture toughness of 9Cr-1Mo steel

  3. Precipitation sequences in austenitic Fe-22Cr-21Ni-6Mo-(N) stainless steels

    International Nuclear Information System (INIS)

    Kim, S.-J.; Lee, T.-H.

    1999-01-01

    Precipitation sequence of nitrogen containing Fe-22Cr-21Ni-6Mo-N austenitic stainless steel has been investigated after aging at high temperatures, and compared with nitrogen free steel. The σ phases and M 23 C 6 carbides were observed along the grain boundaries as well as in the matrix in both of the solution treated specimens. The M 6 C carbides and chi phase appeared successively in between 3 hours and 24 hours depending on the nitrogen content. Main difference in aging behavior was the precipitation of fine nitrides. Aging for 24 hours and 168 hours of nitrogen containing steel resulted in the formation of fine Cr 2 N and faceted AlN nitrides. The crystallography, structure and morphology were analyzed with analytical electron microscopy. (orig.)

  4. Effect of laser absorption on picosecond laser ablation of Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide

    Science.gov (United States)

    Wu, Baoye; Liu, Peng; Wang, Xizhao; Zhang, Fei; Deng, Leimin; Duan, Jun; Zeng, Xiaoyan

    2018-05-01

    Due to excellent properties, Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide are widely used in industry. In this paper, the effect of absorption of laser light on ablation efficiency and roughness have been studied using a picosecond pulse Nd:YVO4 laser. The experimental results reveal that laser wavelength, original surface roughness and chemical composition play an important role in controlling ablation efficiency and roughness. Firstly, higher ablation efficiency with lower surface roughness is achieved on the ablation of 9Cr18 at 532, comparing with 1064 nm. Secondly, the ablation efficiency increases while the Ra of the ablated region decreases with the decrease of original surface roughness on ablation of Cr12MoV mold steel at 532 nm. Thirdly, the ablation efficiency of H13A cemented carbide is much higher than 9Cr18 stainless steel and Cr12MoV mold steel at 1064 nm. Scanning electron microscopy images reveals the formation of pores on the surface of 9Cr18 stainless steel and Cr12MoV mold steel at 532 nm while no pores are formed at 1064 nm. As to H13A cemented carbide, worm-like structure is formed at 1064 nm. The synergetic effects of the heat accumulation, plasma shielding and ablation threshold on laser ablation efficiency and machining quality were analyzed and discussed systematically in this paper.

  5. Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi2 and CoCrFeNi2Mo0.25 under Sodium Chloride Aqueous Conditions

    Directory of Open Access Journals (Sweden)

    Alvaro A. Rodriguez

    2018-01-01

    Full Text Available The corrosion behavior of high-entropy alloys (HEAs CoCrFeNi2 and CoCrFeNi2Mo0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276 and stainless steel 316L (UNS 31600 to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pitting corrosion. Cyclic voltammetry (CV can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi2Mo0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi2 and stainless steel 316L.

  6. Analysis of High Temperature Deformed Structure and Dynamic Precipitation in W9Mo3Cr4V Steel

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    With TEM、SEM, various high-temperature deformed structures inW9Mo3Cr4V steel were investigated. The sub-structures,recrystallized nuclei, as well as the dynamic precipitation were also studied and analyzed. The relationship between recrystallized structures and dynamic precipitation was discussed. The results showed that the deformed structures in W9Mo3Cr4V steel are more complicated than those in low alloy steels. Because W9Mo3Cr4V steel is a high-speed steel, there are a large number of residual carbides on the matrix. Also, much dynamic precipitating carbides will precipitate during deformation at high temperature.

  7. Long-term Stability of 9- to 12 % Cr Steels

    DEFF Research Database (Denmark)

    Hald, John

    2004-01-01

    In the recent 25 years creep rupture strength of 9- to 12 %Cr steels for steam pipes and turbines has been doubled by development of new alloys. This development has formed a basis for improved efficiency of fossil fired steam power plants by introduction of advanced steam temperatures...... and pressures. Newly developed steam pipe steels are based on modifications of well-established steels like the X 20CrMoV12 1. Balanced addition of V, Nb and N to a 9Cr 1 Mo steel led to the Modified 9 Cr steel P 91. Addition of 1% W to a 9Cr 1 MoVNbN base composition led to steel E 911 and partial replacement...... of Mo with 1.8 % W combined with a slight amount of Boron led to steel P 92. The creep rupture strength of these new alloys are now secured with long-term tests up to 100,000 hours, which demonstrate improvements of 50% (P 91), 75 % (E 911) and 100 % (P 92) in strength compared to X 20CrMoV12 1....

  8. Creep and creep fatigue crack behavior of 1Cr- and 9Cr-steels

    International Nuclear Information System (INIS)

    Maile, K.; Klenk, A.; Schellenberg, G.; Granacher, J.; Tramer, M.

    2000-01-01

    A large database for creep crack initiation and propagation under constant load conditions is available on conventional power plant steels of types 1%Cr and 12%Cr. Modern plants are often used in the medium and peak load regime, thus the dominant loading situation in high temperature components is creep fatigue. For life assessment data about crack initiation and growth under creep fatigue loading are required. These characteristics can not be substituted by pure fatigue or creep crack data. Therefore, a comprehensive test programme was started to investigate the creep fatigue crack behaviour of a 1%CrMoNiV turbine rotor steel (30CrMoNiV 4 11) at 550 C and a new 9%CrMoVNb pipe steel (type P 9 1) at 600 C. DENT-specimen with 15 and 60 mm thickness as well as side grooved CT-specimen with 25 and 50 mm thickness have been tested to determine possible influences of geometry and thus to check the transferability of the data to components. The creep fatigue crack growth results of tests with dwell times between t H = 0,32h and 10 h lie in the scatterbands given by creep crack growth results. Nevertheless a higher crack growth rate under creep fatigue conditions can be stated. An increase in crack growth rate due to creep fatigue is clearly visible. Loading situations with frequencies higher than 1.10 -4 Hz should be not assessed with pure creep crack results or sufficient safety margins have to be applied. (orig.)

  9. Evaluation of rolling contact fatigue of induction heated 13Cr-2Ni-2Mo Stainless steel bar with Si3N4-ball

    Science.gov (United States)

    Yadoiwa, Ariyasu; Mizobe, Koshiro; Kida, Katsuyuki

    2018-03-01

    13Cr % martensitic stainless steels were used in various industry, because they have excellent corrosion resistance and high hardness among other stainless steels. They are also expected as a bearing material, however, the research on rolling contact fatigue (RCF) is not enough. In this study, 13Cr-2Ni-2Mo stainless steels were quenched by induction heating and their RCF lives were evaluated. A Si3N4-ball was used in order to apply higher stress (Pmax = 5.6 GPa) than our previous tests (Pmax=5.3 GPa), in a single-ball RCF testing machine. It was found that the basic life (L10) was 2.20×106 cycles and Median life (L50) was 6.04×106 cycles. In addition, Weibull modulus became higher than the previous tests.

  10. Heat treatment effects on impact toughness of 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated to 100 dpa

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

    Plates of 9Cr-1MoVNb and 12Cr-1MoVW steels were given four different heat treatments: two normalizing treatments were used and for each normalizing treatment two tempers were used. Miniature Charpy specimens from each heat treatment were irradiated to {approx}19.5 dpa at 365{degrees}C and to {approx}100 dpa at 420{degrees}C in the Fast Flux Test Facility (FFTF). In previous work, the same materials were irradiated to 4-5 dpa at 365{degrees}C and 35-36 dpa at 420{degrees}C in FFTF. The tests indicated that prior austenite grain size, which was varied by the different normalizing treatments, had a significant effect on impact behavior of the 9Cr-1MoVNb but not on the 12Cr-1MoVW. Tempering treatment had relatively little effect on the shift in DBTT for both steels. Conclusions are presented on how heat treatment can be used to optimize impact properties.

  11. Heat treatment effects on impact toughness of 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated to 100 dpa

    International Nuclear Information System (INIS)

    Klueh, R.L.; Alexander, D.J.

    1997-01-01

    Plates of 9Cr-1MoVNb and 12Cr-1MoVW steels were given four different heat treatments: two normalizing treatments were used and for each normalizing treatment two tempers were used. Miniature Charpy specimens from each heat treatment were irradiated to ∼19.5 dpa at 365 degrees C and to ∼100 dpa at 420 degrees C in the Fast Flux Test Facility (FFTF). In previous work, the same materials were irradiated to 4-5 dpa at 365 degrees C and 35-36 dpa at 420 degrees C in FFTF. The tests indicated that prior austenite grain size, which was varied by the different normalizing treatments, had a significant effect on impact behavior of the 9Cr-1MoVNb but not on the 12Cr-1MoVW. Tempering treatment had relatively little effect on the shift in DBTT for both steels. Conclusions are presented on how heat treatment can be used to optimize impact properties

  12. Room and elevated temperature Mechanical Behavior of 9-12% Cr Steels

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, Omer N.; Hawk, Jeffrey A.; Schrems, Karol K.

    2005-02-01

    The mechanical properties of medium Cr steels used in fossil fired power plants are very good because of their excellent high temperature microstructural stability. However, as the desire to increase the operating temperature (>650C) of the plant goes up, the need for steels that maintain their strength at these temperatures also increases. The mechanical properties of three medium Cr steels (0.08C-(9-12)Cr-1.2Ni-0.7Mo-3.0Cu-3.0Co-0.5Ti) were investigated through hardness, hot hardness and tensile measurements. The strength of the 9-12%Cr steels at room temperature after long-term isothermal aging (750C; 1000 hours) compares favorably with that of other power plant steels (e.g., P91). In addition, the elevated temperature strength and hot hardness also behave similarly. The mechanical behavior will be discussed in terms of the strength, elongation and tensile fracture characteristics.

  13. Microstructure investigation of NiAl-Cr(Mo) interface in a directionally solidified NiAl-Cr(Mo) eutectic alloyed with refractory metal

    International Nuclear Information System (INIS)

    Chen, Y.X.; Cui, C.Y.; Guo, J.T.; Li, D.X.

    2004-01-01

    The microstructure of a directionally solidified NiAl-Cr(Mo) eutectic alloyed with refractory metal in as-processed and heat-treated states has been studied by means of scanning electron microscopy and high resolution electron microscopy (HREM). The microstructure of the NiAl-Cr(Mo) eutectic was characterized by lamellar Cr(Mo) phases embedded within NiAl matrix with common growth direction of . The interface between NiAl and lamellar Cr(Mo) did not have any transition layers. Misfit dislocations were observed at the NiAl-Cr(Mo) interface. In addition to lamellar Cr(Mo) phases, coherent Cr(Mo, Ni, Al) precipitates and NiAl precipitates were also observed in the NiAl matrix and lamellar Cr(Mo) phases, respectively. After hot isostatic pressing and heat treatment, the NiAl-Cr(Mo) interfaces became smooth and straight. Square array of misfit dislocations was directly observed at the (0 0 1) interface between NiAl and Cr(Mo, Ni, Al) precipitate. The configuration of misfit dislocation network showed a generally good agreement with prediction based on the geometric O-lattice model

  14. Residual stress determination by neutron diffraction in a car gear-shaft made of 20NiCrMo2 alloyed case hardening steel

    Czech Academy of Sciences Publication Activity Database

    Rogante, M.; Mazzanti, M.; Mikula, Pavol; Vrána, Miroslav

    2012-01-01

    Roč. 50, č. 4 (2012), s. 213-220 ISSN 0023-432X R&D Projects: GA ČR(CZ) GAP204/12/1360 Institutional support: RVO:61389005 Keywords : 20NiCrMo2 steel * gear-shaft * caser hardening * residual stress * neutron diffraction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.687, year: 2012

  15. Microstructure and elevated temperature stability of 9-12% Cr steels

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, Omer N.; Hawk, Jeffrey A.

    2005-02-01

    Medium Cr steels have been used in fossil fired power plants for many years because of their excellent high temperature stability and mechanical properties. As the desire to increase the efficiency of power plants continues, the operating temperature (>650C) continues to go up. Currently available low and medium Cr containing steels will not withstand the new operating temperature and must be reassessed in terms of their solid-solution and precipitation strengthening schemes. Three medium Cr steels were developed to investigate high temperature alloy strengthening strategies: 0.08C-(9-12)Cr-1.2Ni-0.7Mo-3.0Cu-3.0Co-0.5Ti. The microstructure of the alloy will be described in the as-cast and thermo-mechanically worked states. In addition, the effect on microstructure from long-term high temperature exposure will also be discussed. Finally, the overall stability of these steels will be compared against currently available power plant steels.

  16. In-situ Raman and X-ray photoelectron spectroscopic studies on the pitting corrosion of modified 9Cr-1Mo steel in neutral chloride solution

    Science.gov (United States)

    Ramya, S.; Nanda Gopala Krishna, D.; Mudali, U. Kamachi

    2018-01-01

    In-situ Raman and X-ray photoelectron spectroscopic studies were performed for the identification of native and corroded surface oxide layers of modified 9Cr-1Mo steel. The Raman data obtained for native oxide layer of modified 9Cr-1Mo steel revealed that it was mainly composed of oxides of Fe and Cr. The presence of alloying element Mo was found to be less significant in the native oxide film. The oxides of Cr were dominant at the surface and were found to be decreasing closer to metal/oxide layer interface. The changes in the chemical composition of the native films upon in-situ pitting during potentiostatic polarization experiment were characterized by in-situ Raman analysis. The corrosion products of potentiostatically polarized modified 9Cr-1Mo steel was composed of dominant Fe (III) phases viz., γ- Fe2O3, α and γ - FeOOH along with the oxides of chromium. The results from Raman analysis were corroborated with the XPS experiments on as received and pitted samples of modified 9Cr-1Mo steel specimens. It was observed that the oxides of Cr and Mo contributed for the stability of the surface layer by forming Cr2O3 and MoO3. Also, the study attempted to find out the intermediate corrosion products inside the metastable pits to account for the pseudo passive behavior of modified 9Cr-1Mo steel in 0.1 M NaCl solution.

  17. Creep-fatigue evaluation method for modified 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Wada, Y.; Aoto, K.

    1997-01-01

    As creep-fatigue evaluation methods on normalized and tempered Modified 9Cr-1Mo steel for design use, the time fraction rule and the simplified conventional ductility exhaustion rule are investigated for the prediction of tension strain hold creep-fatigue damage of this material. For the above investigation, stress relaxation behaviour during strain hold has to be analyzed using stress-strain-time relation. The initial value of stress relaxation was determined by cyclic stress-strain curves in continuous cycling fatigue tests. Cyclic stress-strain behaviour of Mod.9Cr-1Mo(NT) steel is different from that of austenitic stainless steels, so this effect was considered. Stress relaxation analysis was performed using static creep strain-time relation and conventional hardening rule. The time fraction by using the above stress relaxation analysis results can give good prediction for creep-fatigue life of Mod.9Cr-1Mo(NT) steel. For design use it is practical to be able to estimate creep damages conservatively by both strain behaviour of cyclic plastic (in continuous cycling fatigue tests) and monotonic creep (in standard creep tests). The life reduction by strain hold at the minimum peak of compressive stress in creep-fatigue tests was examined, and this effects can be evaluated by the relationship between the location of oxidation and the effective deformation at crack tip. In an accelerated oxidation environment, for example in high temperature and high pressure steam, a different approach for life reduction should be developed based on the mechanism of growth of oxide and crack growth with oxidation. However, in the creep damage dominant region, its effect is saturated and the effect of cavity growth along grain boundary becomes dominant for long-term strain hold in the high temperature conditions. (author). 6 refs, 6 figs

  18. Effect of load ratio and saltwater corrosive environment on the initiation life of fatigue of 10Ni5CrMoV steel

    Science.gov (United States)

    Xie, Xing; Yi, Hong; Xu, Jian; Gen, Liming; Chen, Luyun

    2017-09-01

    Fatigue initiation life has been studied with 10CrNi5MoV steel for use in ocean engineering at different load ratios and in different environmental media. The microstructure and micro-topography have been observed and analyzed by means of SEM, EDS and EBSD. Our findings indicate that, the initiation life of 10Ni5CrMoV steel in seawater is shorter than that in air, and the difference in longevity is larger with the increasing of load ratio. Corrosion pits had a great influence on initial corrosion fatigue life.

  19. Toughness of 2,25Cr-1Mo steel and weld metal

    Science.gov (United States)

    Acarer, Mustafa; Arici, Gökhan; Acar, Filiz Kumdali; Keskinkilic, Selcuk; Kabakci, Fikret

    2017-09-01

    2,25Cr-1Mo steel is extensively used at elevated temperature structural applications in fossil fire power plants for steam pipes, nozzle chambers and petrochemical industry for hydrocracking unit due to its excellent creep resistance and good redundant to oxidation. Also they should have acceptable weldability and toughness. The steels are supplied in quenched and tempered condition and their welded components are subjected to post-weld heat treatment (PWHT). Tempering process is carried out at 690-710°C to improve toughness properties. However they are sensitive to reheat cracking and temper embrittlement. To measure temper embrittlement of the steels and their weld metal, temper embrittlement factor and formula (J factor - Watanabe and X formula- Bruscato) are used. Step cooling heat treatment is also applied to determine temper embrittlement. In this study, toughness properties of Cr Mo (W) steels were reviewed. Also transition temperature curves of 2,25Cr-1Mo steel and its weld metal were constructed before and after step cool heat treatment as experimental study. While 2,25Cr-1Mo steel as base metal was supplied, all weld metal samples were produced in Gedik Welding Company. Hardness measurements and microstructure evaluation were also carried out.

  20. Structure of steel 8 CrMoNiNb 9 10 and its variations in long-term thermal stress

    International Nuclear Information System (INIS)

    Fabritius, H.; Schnabel, E.

    1976-01-01

    On four casts of steel 8 CrMoNiNb 9 10 with about 0.06% C, 0.25; Si, 0.7% Mn, 0.012% N, 0.002 to 0.020% Al, 2.25% Cr, 0.94% Mo, 0.63 to 0.91% Nb and 0.67% Ni, transformation behaviour and structural changes during long-time annealing at 500 to 750 degC lasting up to 30,000 h were studied in unformed condition and after previous cold forming. The carbon content was largely bound in form of primary niobium carbonitrides so that during quenching and tempering low-carbon bainite was formed, or at very slow cooling a ferritic structure without pearlite. Martensite occurred only after fast cooling from temperatures above 1200 degC. Bainite exhibited a very high dislocation density and a large number of coherent niobium carbonitrides. During tempering, the precipitates overaged, and the dislocations started to arrange themselves to subgrain boundaries. Hardness and strength in quenched and tempered condition were essentially governed by dislocation density and size of subgrains. In the whole range of bainite transformation, they are only slightly dependent upon the cooling rate and hence upon the dimensions of the products. The structural changes which occurred in bainitic material during long-time aging and led to a ferritic structure in the final state were interpreted as recovery and recrystallization. In unformed and slightly formed material recrystallization led to a very coarse-grained structure. In highly formed material a very fine-grained structure was achieved by recrystallization. By a high degree of cold forming the recrystallization process was considerably promoted. With an annealing time of 10 5 h, no recrystallization is to be expected for unformed specimens of the studied cast up to 580 degC, but above 650 degC complete recrystallization. (author)

  1. Microchemistry of neutron irradiated 12%CrMoVNb martensitic steel

    International Nuclear Information System (INIS)

    Little, E.A.; Morgan, T.S.; Faulkner, R.G.

    1992-01-01

    Non-equilibrium solute segregation has been studied in a 12%CrMoVNb martensitic steel following fast reactor irradiation at 465 C and correlated with the development of M 6 X η-phase. Cr, Ni, Si, Mo, P and Mn are all shown to exhibit positive segregation to lath boundaries and are subsequently incorporated into M 6 X precipitates. The co-segregation of a combination of these elements which include P and Si, and possibly Cr or Mo, appears to promote M 6 X formation

  2. Fatigue Properties of Aged Mod. 9Cr-1Mo

    International Nuclear Information System (INIS)

    Kim, Dae Whan; Kim, Sung Ho; Lee, Chan Bock

    2007-01-01

    Ferritic/Martensitic steel has a good mechanical properties and a lower thermal expansion coefficient than austenitic stainless steel. Mechanical property of Mod. 9Cr-1Mo steel is less than austenitic stainless steel at high temperature. High temperature mechanical properties are affected by precipitation for Mod. 9Cr-1Mo. FMS steel is used for long time at high temperature and the effect of aging on mechanical properties is very important. In this study, low cycle fatigue properties with aging were investigated

  3. An examination of the potential for 9%Cr1%Mo steel as thick section tubeplates in fast reactors

    International Nuclear Information System (INIS)

    Orr, J.; Sanderson, S.J.

    1984-01-01

    The steam generator units of future commercial demonstration fast reactors are likely to have a requirement for heavy section tubeplates (up to 500mm thick) with good elevated temperature strength and creep-fatigue resistance. A comparison of the mechanical properties available for ferritic steels has suggested that 9%Cr1%Mo steel would be a strong candidate material for this application. Although this steel is covered in some national specifications for tubes, pipes, plates and forgings and is also well established in the UK nuclear industry, international experience to date is confined to sections less than ca 150mm. The potential of 9%Cr1%Mo steel for use in thick sections has therefore been assessed in the present study by using simulation heat treatments. The work reported here involved the laboratory-scale cooling of bar samples to simulate water-quenching rates in cylindrical sections up to 720mm diameter (ie: equivalent to 500mm thick plate). The tensile properties at ambient and 525 0 C and impact fracture appearance transition temperatures were determined for material tempered after cooling at simulated thick section rates; the transformation characteristics as influenced by the net chromium equivalent were also established. The results of this work show that 9%Cr1%Mo steel may be fully hardened in the equivalent of the section sizes examined,and the mechanical properties of tempered material show only a small reduction from those of thin section normalised and tempered 9%Cr1%Mo steel. These findings support the potential usage of heavy section 9%Cr1%Mo steel envisaged for fast reactor steam generator tubeplates

  4. Mechanical properties of irradiated 9Cr-2WVTa steel

    International Nuclear Information System (INIS)

    Klueh, R.L.; Alexander, D.J.; Rieth, M.

    1998-01-01

    An Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) steel has excellent strength and impact toughness before and after irradiation in the Fast Flux Test Facility and the High Flux Reactor (HFR). The ductile-brittle transition temperature (DBTT) increased only 32 C after 28 dpa at 365 C in FFTF, compared to a shift of ∼60 C for a 9Cr-2WV steel--the same as the 9Cr-2WVTa steel but without tantalum. This difference occurred despite the two steels having similar tensile but without tantalum. This difference occurred despite the two steels having similar tensile properties before and after irradiation. The 9Cr-2WVTa steel has a smaller prior-austenite grain size, but otherwise microstructures are similar before irradiation and show similar changes during irradiation. The irradiation behavior of the 9Cr-2WVTa steel differs from the 9Cr-2WV steel and other similar steels in two ways: (1) the shift in DBTT of the 9Cr-2WVTa steel irradiated in FFTF does not saturate with fluence by ∼28 dpa, whereas for the 9Cr-2WV steel and most similar steels, saturation occurs at <10 dpa, and (2) the shift in DBTT for 9Cr-2WVTa steel irradiated in FFTF and HFR increased with irradiation temperature, whereas it decreased for the 9Cr-2WV steel, as it does for most similar steels. The improved properties of the 9Cr-2WVTa steel and the differences with other steels were attributed to tantalum in solution

  5. Metallurgical aspects of the weldability of Cr-Mo stabilised ferritic steels

    International Nuclear Information System (INIS)

    Colombe, Gerard; Petrequin, Pierre; Donati, J.R.; Zacharie, C.

    1977-01-01

    Results of tests performed to compare the tendency of 2.25 Cr-Mo and 9 Cr-2 Mo steels stabilised with niobium and niobium + vanadium, to different cracking phenomena susceptible to occur during welding, stress-relieving and service in the conditions of fast breeder reactors are presented

  6. Comparison of low-cycle fatigue data of 2 1/4%CrMo steels

    International Nuclear Information System (INIS)

    Sanderson, S.J.; Petrequin, P.; Nieuwland, H.C.D.

    Data files have been produced on international strain-controlled fatigue information available for 2 1/4%CrMo steels; data assessment from these files is treated in three categories viz: annealed and isothermally annealed 2 1/4%Cr1%Mo steel; normalised and tempered and quenched and tempered 2 1/4%Cr1%Mo steel; and 2 1/4%CrMo variants. The available data have been considered generally in terms of total strain range vs. cycles to failure (Nsub(f)), tensile stress at Nsub(f)/2 vs. cycles to failure and time to failure vs. cycles to failure. Where possible the continuous cycling data have been statistically analysed in terms of the elastic and plastic strain components and cycles to failure to yield best-fit equations over defined temperature (T) regimes viz: T <= 427 deg. C, 427 deg. C < T <= 550 deg. C. and 550 deg. C < T <= 600 deg. C. The behaviour of the steels within the various classifications is discussed. (author)

  7. On the corrosion testing of weldments of high alloyed CrNiMo-stainless steels and NiCrMo-alloys

    International Nuclear Information System (INIS)

    Riedel, G.; Voigt, C.; Werner, H.

    1997-01-01

    Weldments of high-alloyed CrNiMo stainless steels and NiCrMo alloys can be more susceptible to localized corrosion than the solution annealed basic material owing to segregations and precipitations in the heat affected zone, the high temperature zone and/or in the weld. To investigate these differences the FeCl 3 -test (10% FeCl 3 . 6aq), the test ''green death'' (11.5% H 2 SO 4 , 1.2% HCl, 1% CuCl 2 , 1% FeCl 3 ) as well as chronopotentiostatic tests in artificial sea water or in 3% NaCl-solution are used. In particular for testing the highest alloyed materials a CaCl 2 -test was developed (4.5 M CaCl 2 , chronopotentiostatic test in duration of 8 to 10 hours at + 200 mV (SCE)), which can be carried out to a temperature of 115 C at atmospheric pressure. The aggressivity increases in the range FeCl 3 -test, ''green death''-test, CaCl 2 -test. Matching and graduated over-alloyed weldments (TIG, heat input of 7 and 15.5 kJ/cm) of materials 1.4529, 1.4562, 2.4856, 2.4819 (german materials No.) are comparingly examined in various tests, of materials 1.4406, 1.4539, 1.4439 and 1.4563 (german materials No.) only matching weldments in the FeCl 3 -test. In strongly oxidizing media only a highly over-alloyed performed weldment (filler material 2.4607, german material No.) produces the best corrosion behaviour, measured as the critical temperatures of localized corrosion. Measurements of critical current densities of passivation can be used for investigations of corrosion behaviour of weldments, too. Critical current densities of passivation are showing a tendency to inverse proportion to the critical temperatures of localized corrosion. Suitable electrolytes are among others 0.2 M H 2 SO 4 + 1 M NaCl + 10 -3 % KSCN, N 2 -bubbled, 25 to 60 C and xM H 2 SO 4 + 4 M NaCl + 10 -3 % KSCN (x = 0.05 to 1), 25 C, in contact with air. An influence of heat input at the welding is indicated in the test of localized corrosion, but it is only small. It is sometimes more clearly shown at

  8. Creep and time to rupture of a 16/16 Cr Ni Steel

    International Nuclear Information System (INIS)

    Solano, R.; Garcia, R.; Bohm, H.; Schirra, M.

    1972-01-01

    The influence of different thermal-mechanical treatments on the creep and time to rupture of a 16/16 Cr.Ni steel is studied. The solution treated material after annealing at 700-800 degree centigree did not affect time to rupture. At the contrary a 12% cold-working and annealing at 800 degree centigree improve the time to rupture. This treatment is preserved up to 700 degree centigree 10 4 hours. The ductility is not strongly affected. A metallographic study of the fracture was carried out. (Author) 23 refs

  9. Effects of air melting on Fe/0.3/3Cr/0.5Mo/2Mn and Fe/0.3C/3Cr/0.5Mo/2Ni structural alloy steels

    International Nuclear Information System (INIS)

    Steinberg, B.

    1979-06-01

    Changing production methods of a steel from vacuum melting to air melting can cause an increase in secondary particles, such as oxides and nitrides, which may have detrimental effects on the mechanical properties and microstructure of the alloy. In the present study a base alloy of Fe/0.3C/3Cr/0.5Mo with either 2Mn or 2Ni added was produced by air melting and its mechanical properties and microstructure were compared to an identical vacuum melted steel. Significant differences in mechanical behavior, morphology, and volume fraction of undissolved inclusions have been observed as a function of composition following air melting. For the alloy containing manganese, all properties remained very close to vacuum melted values but the 2Ni alloy displayed a marked loss in Charpy impact toughness and plane strain fracture toughness. This loss is attributed to an increase in volume fraction of secondary particles in the nickel alloy, as opposed to both the Mn alloy and vacuum melted alloys, as well as to substaintially increased incidence of linear coalescence of voids. Microstructural features are discussed

  10. Mechanical behavior of 9Cr-1Mo-1V steel due to creep fatigue deformation

    International Nuclear Information System (INIS)

    Kim, Sang Tae; Kim, Jae Kyoung; Lee, Hak Sun; Oh, Sang Hyun; Kwun, Sook In; Kim, Chung Seok

    2005-01-01

    Creep-fatigue tests with trapezoid load wave were performed on a 9Cr-1Mo-1V steel at high temperature(550 .deg. C). Trapezoid load wave is considering about hold time for creep effects. we could find out some information in the relationship between number of cycles to failure and hold time. The number of cycles to failure depended on hold time. The cyclic behavior of 9Cr-1Mo-1V steel was characterized by cyclic softening with increasing number of cycles in high temperature. Also we could observe some cavity in the specimens. The size of cavity was different from each hold time

  11. Characterization on the Microstructure Evolution and Toughness of TIG Weld Metal of 25Cr2Ni2MoV Steel after Post Weld Heat Treatment

    Directory of Open Access Journals (Sweden)

    Xia Liu

    2018-03-01

    Full Text Available The microstructure and toughness of tungsten inert gas (TIG backing weld parts in low-pressure steam turbine welded rotors contribute significantly to the total toughness of the weld metal. In this study, the microstructure evolution and toughness of TIG weld metal of 25Cr2Ni2MoV steel low-pressure steam turbine welded rotor under different post-weld heat treatment (PWHT conditions are investigated. The fractography and microstructure of weld metal after PWHT are characterized by optical microscope, SEM, and TEM, respectively. The Charpy impact test is carried out to evaluate the toughness of the weld. The optical microscope and SEM results indicate that the as-welded sample is composed of granular bainite, acicular ferrite and blocky martensite/austenite (M-A constituent. After PWHT at 580 °C, the blocky M-A decomposes into ferrite and carbides. Both the number and size of precipitated carbides increase with holding time. The impact test results show that the toughness decreases dramatically after PWHT and further decreases with holding time at 580 °C. The precipitated carbides are identified as M23C6 carbides by TEM, which leads to the dramatic decrease in the toughness of TIG weld metal of 25Cr2Ni2MoV steel.

  12. Effects of the Microstructure on Segregation behavior of Ni-Cr-Mo High Strength Low Alloy RPV Steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    SA508 Gr.4N Ni-Cr-Mo low alloy steel has an improved fracture toughness and strength, compared to commercial Mn-Mo-Ni low alloy RPV steel SA508 Gr.3. Higher strength and fracture toughness of low alloy steels could be achieved by adding Ni and Cr. So there are several researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and time of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, it requires a resistance of thermal embrittlement in the high temperature range including temper embrittlement resistance. S. Raoul reported that the susceptibility to temper embrittlement was increasing a function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So the comparison of temper embrittlement behavior was made between martensitic microstructure and bainitic microstructure with a viewpoint of boundary features in SA508 Gr.4N, which have mixture of tempered bainite/martensite. In this study, we have compared temper embrittlement behaviors of SA508 Gr.4N low alloy steel with changing volume fraction of martensite. The mechanical properties of these low alloy steels) were evaluated after a long-term heat treatment(450 .deg. C, 2000hr. Then, the images of the segregated boundaries were observed and segregation behavior was analyzed by AES. In order to compare the misorientation distributions of model alloys, grain boundary structures were measured with EBSD

  13. Effect of Welding Processes on the Microstructure, Mechanical Properties and Residual Stresses of Plain 9Cr-1Mo Steel Weld Joints

    Science.gov (United States)

    Nagaraju, S.; Vasantharaja, P.; Brahadees, G.; Vasudevan, M.; Mahadevan, S.

    2017-12-01

    9Cr-1Mo steel designated as P9 is widely used in the construction of power plants and high-temperature applications. It is chosen for fabricating hexcan fuel subassembly wrapper components of fast breeder reactors. Arc welding processes are generally used for fabricating 9Cr-1Mo steel weld joints. A-TIG welding process is increasingly being adopted by the industries. In the present study, shielded metal arc (SMA), tungsten inert gas (TIG) and A-TIG welding processes are used for fabricating the 9Cr-1Mo steel weld joints of 10 mm thickness. Effect of the above welding processes on the microstructure evolution, mechanical properties and residual stresses of the weld joints has been studied in detail. All the three weld joints exhibited comparable strength and ductility values. 9Cr-1Mo steel weld joint fabricated by SMAW process exhibited lower impact toughness values caused by coarser grain size and inclusions. 9Cr-1Mo steel weld joint fabricated by TIG welding exhibited higher toughness due to finer grain size, while the weld joint fabricated by A-TIG welding process exhibited adequate toughness values. SMA steel weld joint exhibited compressive residual stresses in the weld metal and HAZ, while TIG and A-TIG weld joint exhibited tensile residual stresses in the weld metal and HAZ.

  14. The influence of heating rate on reheat-cracking in a commercial 2 1/4Cr1Mo steel

    International Nuclear Information System (INIS)

    Hippsley, C.A.

    1983-03-01

    The effects of elevated heating rate on stress-relief cracking in a commercial 2 1/4 Cr1Mo steel have been investigated. A SEN bend-specimen stress-relaxation test was used to assess reheat cracking susceptibility and fracture mechanisms for an initial post-weld heating rate of 1000 Kh - 1 . Two factors controlling the influence of heating rate on the final severity of cracking were identified, i.e. the rate of stress-relaxation with respect to temperature, and the time available for crack-growth. The factors were found to counteract each other, but in the case of commercial 2 1/4 Cr1Mo steel, the crack-growth factor outweighed the relaxation factor, resulting in a reduction in the propensity to stress-relief cracking at the elevated heating rate. However, by reference to the results of a separate investigation concerning A508/2 MnMoNiCr steel it was demonstrated that the balance between these two factors may be reversed in other alloy systems, with the consequence that reheat cracking is exacerbated by increasing the initial heating rate. A computer model was addressed to the stress-relaxation test conditions using data from the commercial 2 1/4 Cr1Mo steel. The model predictions exhibited reasonable agreement with experimental test results for both 100 Kh - 1 and 1000 Kh - 1 heating rates. (author)

  15. Studies on the influence of processing methods on the corrosion characteristics of electroslag-tape-plating with NiMo16Cr16Ti. Untersuchungen zum Einfluss der Prozessfuehrung auf die Korrosionseigenschaften beim Elektroschlacke-Bandplattieren mit NiMo16Cr16Ti

    Energy Technology Data Exchange (ETDEWEB)

    Blum, J

    1991-01-01

    The aim of the project was to demonstrate an economic possibility of using NiMo16Cr16Ti reliably as a plating material with simple to use methods. For this, the electroslag and submerged arc welding with tape electrodes as a coating technology are compared with each other. As the research showed, it is possible to coat large surface area, thick walled components economically with NiMo16Cr16Ti using electroslag (RES) tape plating. The choice of powder is important for the hot crack freedom and the precipitation poverty and thus the corrosion resistance of the plating. The silicon content was proved to be of importance in the plating. With the right choice of powder, the second layer already possesses the endurance of laminated materials against intercrystalline corrosion in coating tests as well as against pitting in a 10% FeCl{sub 3} solution. The coating capability lies at 0.5 m{sup 2}/h. - In addition the use of video thermography for on-line surveillance of seam on RES plates is documented. The evaluation of the pictures makes possible the targeting of the external magnets and thus the influencing of the melting bath flux. (orig./RHM) With 80 figs., 12 tabs.

  16. Thermal Aging Evaluation of Mod. 9Cr-1Mo Steel using Nonlinear Rayleigh Waves

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Young-Sang; Kim, Hoe-Woong; Kim, Jong-Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Marino, Daniel; Kim, Jin-Yeon; Jacobs, L.J [Georgia Institute of Technology, Atlanta (United States); Ruiz, Alberto [UMSNH, Morelia (Mexico)

    2014-10-15

    Thermal aging can pose a high risk to decreases in the mechanical properties such as strength or creep resistance. This can lead to an unexpected failure during long term operation. Nonlinear NDE techniques are preferred over conventional NDE techniques (linear ultrasonic measurements) because nonlinear ultrasonic techniques have shown their capability to detect a microstructural damage in the structures undergoing fatigue and creep. These nonlinear ultrasonic techniques make use of the fact that the dislocation density increases, which will create a nonlinear distortion of an ultrasonic wave; this damage causes the generation of measurable higher harmonic components in an initially mono-chromatic ultrasonic signal. This study investigates the recently developed non-contact nonlinear ultrasonic technique to detect the microstructural damage of mod. 9Cr-1Mo steel based on nonlinear Rayleigh wave with varying propagation distances. Nonlinear Rayleigh surface wave measurements using a non-contact, air-coupled ultrasonic transducer have been applied for the thermal aging evaluation of modified 9Cr-1Mo ferritic-martensitic steel. Thermal aging for various heat treatment times of mod.. 9Cr-1Mo steel specimens is performed to obtain the nucleation and growth of precipitated particles in specimens. The amplitudes of the first and second harmonics are measured along the propagation distance and the relative nonlinearity parameter is obtained from these amplitudes. The relative nonlinearity parameter shows a similar trend with the Rockwell C hardness.

  17. The rate(time)- dependent mechanical behavior modified 9Cr-1Mo steel, 3

    International Nuclear Information System (INIS)

    Moosbrugger, J.C.

    1991-01-01

    In this paper, constitutive equations are presented for the nonisothermal small strain behavior of modified 9Cr-1Mo steel between 25degC - 600degC. The basic framework uses the superposition of nonlinear kinematic hardening rules as proposed by Chaboche and coworkes. A framework for accounting for isotropic softening is presented wherein this softening can be included in a drag stress, in a yield stress or as a decrease in the saturation level of kinematic hardening or some combination of these; a single isotropic softening equation is used as determined from experiments. The behavior of modified 9Cr-1Mo steel between 25degC - 600degC has been investigated by Swindeman, and Majors et. al. and many important features have been discussed. Here, model parameters are determined from available isothermal uniaxial data and some correlations with isothermal and nonisothermal tests are presented. (J.P.N.)

  18. 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.

  19. Precipitation behavior of Laves phase and its effect on toughness of 9Cr-2Mo ferritic-martensitic steel

    International Nuclear Information System (INIS)

    Hosoi, Y.; Wade, N.; Kunimitsu, S.; Urita, T.

    1986-01-01

    This study clarified the relationship between the toughness of a 9Cr-2Mo dual phase steel and precipitates formed during aging, with special attention to the Laves phase (Fe 2 Mo). The ductile-brittle transition temperature (DBTT) is increased and the upper shelf energy decreased when the Laves phase begins to precipitate during aging. Electron microscopy and X-ray diffraction indicate that elimination of Si in the steel reduces the precipitation of the Laves phase and results in maintaining good toughness. It is also noted that the toughness of the steel is controlled by the total amount of precipitates (Laves + carbides) in the aging at 873 K for more than 3.6x10 3 ks. A time-temperature-precipitation diagram for the Laves phase is established and it clearly shows that the precipitation of the Laves phase is markedly retarded by the decrease of Si content. In Si-free steel, no Laves phase is observed in the temperature and time range investigated. (orig.)

  20. Creep and time to rupture of a 16/16 Cr Ni Steel; Comportamiento a la fluencia lenta de la aleacion X 8 Cr Ni Mo Nb 1616 con distintos tratamientos termicos

    Energy Technology Data Exchange (ETDEWEB)

    Solano, R; Garcia, R; Bohm, H; Schirra, M

    1972-07-01

    The influence of different thermal-mechanical treatments on the creep and time to rupture of a 16/16 Cr.Ni steel is studied. The solution treated material after annealing at 700-800 degree centigree did not affect time to rupture. At the contrary a 12% cold-working and annealing at 800 degree centigree improve the time to rupture. This treatment is preserved up to 700 degree centigree 10{sup 4} hours. The ductility is not strongly affected. A metallographic study of the fracture was carried out. (Author) 23 refs.

  1. Phase transformation in a Ni-Mo-Cr alloy

    International Nuclear Information System (INIS)

    Dymek, S.; Wrobel, M.; Blicharski, M.; Dollar, M.

    2001-01-01

    The paper gives a characteristic of a nickel-based superalloy containing 25 wt.% Mo and 8 wt.% Cr with particular attention to the influence of a thermochemical and heat treatment on phase transformations. The applied heat treatments are comprised of soaking temperature 1100 o C followed by aging at 650 o C at three conditions: conventional aging for 72 hours, prolonged aging for 4000 hours and prolonged aging for 4000 hours followed by cold working and subsequent aging for 1000 hours. The conventional aging led to the formation of lenticular precipitates of the dispersed metastable Ni 2 (Mo,Cr) phase. The aging for 4000 hours brought about coarsening of the ordered domains without changing their crystallographic and ordering characteristics. The plastic deformation preceded the further aging for 1000 hours accelerated the decomposition of the Ni 2 (Mo,Cr) phase on the mixture of the Ni 3 Mo and Ni 4 Mo-based phases. (author)

  2. Shot Peening Effects on Subsurface Layer Properties and Fatigue Performance of Case-Hardened 18CrNiMo7-6 Steel

    Directory of Open Access Journals (Sweden)

    H. S. Ho

    2018-01-01

    Full Text Available The present study is conducted with a dual-aim: firstly, to examine the effect of several single shot peening conditions on the subsurface layer properties and fatigue performance of the case-hardened 18CrNiMo7-6 steel, and secondly, to propose an optimized peening condition for improved fatigue performance. By carrying out the subsurface integrity analysis and fatigue testing, the underlying relationships among the peening process, subsurface layer property and fatigue performance are investigated, the way peening conditions affect the fatigue life and its associated scatter for the case-hardened 18CrNiMo7-6 steel is quantitatively assessed. The in-depth study shows that dual peening can be an optimized solution, for it is able to produce a subsurface layer with enhanced properties and eventually gain a significant improvement in fatigue performance.

  3. Long-term strength and allowable stresses of grade 10Kh9MFB and X10CrMoVNb9-1 (T91/P91) chromium heat-resistant steels

    Science.gov (United States)

    Skorobogatykh, V. N.; Danyushevskiy, I. A.; Schenkova, I. A.; Prudnikov, D. A.

    2015-04-01

    Currently, grade X10CrMoVNb9-1 (T91, P91) and 10Kh9MFB (10Kh9MFB-Sh) chromium steels are widely applied in equipment manufacturing for thermal power plants in Russia and abroad. Compilation and comparison of tensile, impact, and long-term strength tests results accumulated for many years of investigations of foreign grade X10CrMoVNb9-1, T91, P91, and domestic grade 10Kh9MFB (10Kh9MFB-Sh) steels is carried out. The property identity of metals investigated is established. High strength and plastic properties of steels, from which pipes and other products are made, for operation under creep conditions are confirmed. Design characteristics of long-term strength on the basis of tests with more than one million of hour-samples are determined ( and at temperatures of 500-650°C). The table of recommended allowable stresses for grade 10Kh9MFB, 10Kh9MFB-SH, X10CrMoVNb9-1, T91, and P91 steels is developed. The long-time properties of pipe welded joints of grade 10Kh9MFB+10Kh9MFB, 10Kh9MFB-Sh+10Kh9MFB-Sh, X10CrMoVNb9-1+X10CrMoVNb9-1, P91+P91, T91+T91, 10Kh9MFB (10Kh9MFB-Sh)+X10CrMoVNb9-1(T/P91) steels is researched. The welded joint reduction factor is experimentally determined.

  4. Influence of cooling rates on the transformation behaviour of 9Cr-1Mo-0.07C steel

    International Nuclear Information System (INIS)

    Saroja, S.; Vijayalakshmi, M.; Raghunathan, V.S.

    1992-01-01

    The choice of various decomposition mechanisms of austenite in a 9Cr-1 Mo-0.07C steel under different rates of cooling has been studied. The techniques employed were electron probe micro-analysis, X-ray diffraction and electron microscopy. The observed morphological features may be explained based on the predominance of the two types of transformation, austenite → martensite and austenite → ferrite during cooling. In the steel used in this study, decomposition of austenite to proeutectoid ferrite was favoured at cooling rates less than about 2 Ks -1 . The mechanism by which the supersaturated proeutectoid ferrite relieves its excess solute concentration was also studied. A ''microstructural map'' has been proposed to predict the constitution at the end of any given cooling rate for 9Cr-1 Mo-0.07C steel. The choice of commercial treatment has been rationalized with respect to the resultant microstructural constituents. (Author)

  5. Effect of Cr3C2 content on the microstructure and properties of Mo2NiB2-based cermets

    International Nuclear Information System (INIS)

    Xie, Lang; Li, XiaoBo; Zhang, Dan; Yang, ChengMing; Yin, FuCheng; Xiangtan Univ., Hunan; Xiangtan Univ., Hunan; Xiao, YiFeng

    2015-01-01

    Four series of Mo 2 NiB 2 -based cermets with Cr 3 C 2 addition of between 0 and 7.5 wt.% in 2.5 wt.% increments were studied by means of scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffractometry. The transverse rupture strength and hardness were also measured. It was found that Cr 3 C 2 completely dissolved in Mo 2 NiB 2 -based cermets. Cr 3 C 2 addition improved the wettability of the Ni binder phase on the Mo 2 NiB 2 hard phase, which resulted in a decrease in the porosity and an increase in the phase uniformity. The cermets with 2.5 wt.% Cr 3 C 2 content showed relatively fine grains and almost full density. A high Cr 3 C 2 content resulted in the formation of M 6 C (M = Mo, Cr, Ni) phase. In addition, energy dispersive X-ray spectroscopy results showed that the content of Mo in the binder decreased with increasing Cr 3 C 2 content. The cermets with 2.5 wt.% Cr 3 C 2 addition exhibited the highest transverse rupture strength of 2210 MPa, whereas the cermets without Cr 3 C 2 addition exhibited the highest hardness.

  6. Welding of heterogeneous 12Kh2MFSR steels with the Mn-Cr-Si-Ni system

    International Nuclear Information System (INIS)

    Smirnov, A.N.; Belogolov, E.I.

    1978-01-01

    The process of welding pipes of the 12Kh2MFSR pearlitic steels and austenitic steels of the Mn-Cr-Si-Ni system was studied. The filler materials were selected, and the working capacity of welded joints was examined in ageing and cyclic heatings. The microhardness of steels was measured, and the ultimate strength of welded joints was determined. The following has been established: the composite joints of steels of the Mn-Cr-Si-Ni system and 12Kh2MFSR steel are advisable to be welded on a coating layer welded by the EhA395/9 electrodes on the surface of a pipe of the 12Kh2MFSR pearlitic steel; this guarantees the sufficient working capacity of welded joints

  7. Creep behaviour of the alloys NiCr22Co12Mo and 10CrMo9 10 under static and cyclic load conditions

    International Nuclear Information System (INIS)

    Wolf, H.

    1990-01-01

    The creep behaviour of NiCr20Co12Mo is investigated under static strain and at 800deg C, with stresses applied ranging from 105 MPa to 370 MPa. The ferritic steel 10CrMo 9 10 is tested for its creep behaviour under static strain and at the temperatures of 600deg C and 550deg C, with stresses applied between 154 MPa and 326 MPa (at 600deg C), or between 250 MPa and 458 MPa (at 550deg C). The experiments are made to determine the effects of changes in strain on the materials' deformation behaviour, placing emphasis on transient creep and elastic or anelastic response. The mean internal stress is determined from changes in strain. Cyclic creep is analysed as a behaviour directly responding to the pattern of change in strain. Effects of certain strain changes not clarified so far are analysed. The cyclic strain experiments are analysed according to the velocity factor concept. The usual models of creep deformation (theta projection concept) are compared with the model of effective strain, which is based on the fundamental equation of plastic deformation by dislocation motion (Orowan equation). (MM) [de

  8. Modelling and characterization of chi-phase grain boundary precipitation during aging of Fe-Cr-Ni-Mo stainless steel

    International Nuclear Information System (INIS)

    Xu, W.; San Martin, D.; Rivera Diaz del Castillo, P.E.J.; Zwaag, S. van der

    2007-01-01

    High molybdenum stainless steels may contain the chi-phase precipitate (χ, Fe 36 Cr 12 Mo 10 ) which may lead to undesirable effects on strength, toughness and corrosion resistance. In the present work, specimens of a 12Cr-9Ni-4Mo wt% steel are heat treated at different temperatures and times, and the average particle size and particle size distribution of chi-phase precipitate are studied quantitatively. A computer model based on the KWN framework has been developed to describe the evolution of chi-phase precipitation. The kinetic model takes advantage of the KWN model to describe the precipitate particle size distribution, and is coupled with the thermodynamic software ThermoCalc for calculating the instantaneous local thermodynamic equilibrium condition at the interface and the driving force for nucleation. A modified version of Zener's theory accounting for capillarity effects at early growth stages is implemented in this model. The prediction of the model for chi-phase precipitation at a grain boundary is compared to experimental results and both the average particle size and the particle size distribution are found to be in good agreement with experimental observations at late precipitation stages

  9. Soft-martensitic stainless Cr-Ni-Mo steel for turbine rotors in geothermic power stations

    International Nuclear Information System (INIS)

    Schonfeld, K.; Potthast, E.

    1986-01-01

    Steel Grade X5 Cr-Ni-Mo 12 6 containing 0.05% carbon, 12% chromium, 6% nickel, and 1.50% molybdenum is an advantageous material for turbine rotors in geothermic power stations because of its excellent strength and toughness properties in combination with good erosion and corrosion resistance. In terms of the phase diagram, this soft-martensitic steel has its place at the martensite/austenite/ferrite interface. Therefore, its chemical composition must be chosen so as to have a completely martensitic structure after hardening. The manufacture of and the mechanical properties of a turbine rotor 1200 mm in diameter by 5600 mm in length with a finished weight of approximately 21.5 tons are described in detail

  10. The influence of heat treatment and process parameters optimization on hardness and corrosion properties of laser alloyed X12CrNiMo steel

    CSIR Research Space (South Africa)

    Popoola, API

    2016-10-01

    Full Text Available Martensitic stainless steels are used in the production of steam turbine blades but their application is limited due to low hardness and poor corrosion resistance. Laser surface alloying and heat treatment of X12CrNiMo Martensitic stainless steel...

  11. PLASTIC DEFORMATION ON THE MACHINED SURFACE OF STEEL Cr20Ni10MoTi AT DRILLING

    Directory of Open Access Journals (Sweden)

    Jozef Jurko

    2009-07-01

    Full Text Available Information about material machinability is very important for the machining technology. Precise and reliable information on the machinability of a material before it enters the machining process is a necessity, and this brings the verification of technological methods in practice. This article presents the conclusions of machinability tests on austenitic stainless steel according to EN-EU (ISO: steel Cr20Ni10MoTi. This article presents the conclusions of VEGA grant agency at the Ministry of Education SR for supporting research work and co-financing the projects: Grant work #01/3173/2006 with the title „Experimental investigation of cutting zones in drilled and milled stainless steels

  12. Heterogeneity of structure and properties of 12Cr18Ni10Ti and 08Cr16Ni11Mo3 stainless steels irradiated up to high damaging doses in reactor Bn-350

    International Nuclear Information System (INIS)

    Maksimkin, O.P.; Tivanova, O.V.; Turubarova, L.G.; Silnyagina, N.S.; Doronina, T.A.

    2006-01-01

    Full text: Earlier, during investigation of post-operating properties and structure of responsible units of fast neutron reactors there was shown /1, 2/ that depending on character of preliminary treatment of austenite stainless steel (austenization, cold deformation, mechanical and thermal treatment) radiation effects could be different. In /2/ one could observe heterogeneity at swelling of cold- worked hexahedral ducts along perimeter, in particular, the swelling of corners was less than plates'. At the same time after mechanical-thermal treatment the corners swell in 3-5 times of magnitude higher than plates. By the present there are several assumptions about nature of this phenomenon. One of them is a difference of deformation degree of material in corners and plates of the duct. It is known that /3/ external effects (including deformation) induce martensitic γ→α transformation in austenitic steels, due to which the structure and properties of steel are changed. In particular, paramagnetic FCC matrix reveals sites with ferromagnetic BCC structure. Steel heating, containing martensitic α-phase higher than ∼ 450-800 deg C, results in reverse γ→α transformation in material, which in its turn leads to formation of phase phase-hardened austenite. We can expect that only peculiarities of processes of direct and reverse martensitic transformations, which took place during preliminary austenitic steel treatment, will predetermine its behavior under irradiation. Taking into account the above mentioned there have been carried out complex material-scientific investigations of 12Cr18Ni10Ti and 08Cr16Ni11Mo3 steel samples cut off from different sites (both adjacent to corners and far from them) of hexagonal ducts of spent fuel assemblies of BN-350 reactor. There were used samples in the form of plates of different sizes: 5x10x2 mm - for metallographic investigations (microscope Neophot-2) and determination of microhardness (PMT-3); 2x20x0,3 mm - for mechanical

  13. Comparison of the corrosion resistance of DIN W. Nr. 1.4970 (15%Cr-15%Ni-1.2%Mo-Ti and ASTM F-138 (17%Cr-13%Ni-2.5%Mo austenitic stainless steels for biomedical applications

    Directory of Open Access Journals (Sweden)

    Maysa Terada

    2006-09-01

    Full Text Available The resistance to localised corrosion of the full austenitic 15%Cr-15%Ni-1.2%Mo titanium stabilized stainless steel (DIN W. Nr. 1.4970 was investigated by electrochemical methods including electrochemical impedance spectroscopy (EIS, potentiodynamic polarization and potentiostatic polarization measurements in a phosphate-buffered solution (PBS. The low carbon and non-stabilized austenitic stainless steel, AISI 316L (ASTM F-138, widely used for surgical implants, was also tested for comparison. The tests were conducted at room temperature after a stable potential had been reached. After the electrochemical measurements, the surfaces of the specimens were observed using SEM to evaluate the presence of pits. Potentiodynamic polarization results showed that both steels are prone to localized corrosion. Larger pits were found on the surface of AISI 316L specimens after the electrochemical tests. EIS response has indicated the duplex structure of the passive oxides. The results showed that the electrochemical behaviour of the DIN W. Nr. 1.4970 is better than of AISI 316L steel. Therefore, their application as an implant material may be considered.

  14. Representation of the properties 10 CrMoNiNb 9 10

    International Nuclear Information System (INIS)

    Dette, M.; Hahn, H.; Nieuwland, H.C.D.; Tichler, J.W.

    The high-temperature ferritic steal 10 CrMoNiNb 9 10 is used as structural material in nuclear steam generators. It is exposed to loads within the creep range. In order to resist safety also loads caused by incidents after long temperature stress, the time-independent stability parameters must not fall below specified minimum values. The material is characterised by the stability degree Nb/C+N and the niobium excess δ Nb. (orig.) [de

  15. Effect of niobium on the embrittlement of 2.25 Cr and 2.25 Cr-1Mo steels by phosphous

    International Nuclear Information System (INIS)

    Antunes, J.L.B.

    1985-01-01

    The influence of niobium on the temper embrittlement of 2.25Cr and 2.25 Cr-1Mo steels doped with phosphorus is evaluated. The transition temperatures of the samples tempered at 650 0 C and aged at different temperatures for niobium steels. (M.J.C.) [pt

  16. Microstructural investigations of fast reactor irradiated austenitic and ferritic-martensitic stainless steel fuel cladding

    International Nuclear Information System (INIS)

    Agueev, V.S.; Medvedeva, E.A.; Mitrofanova, N.M.; Romanueev, V.V.; Tselishev, A.V.

    1992-01-01

    Electron microscopy has been used to characterize the microstructural changes induced in advanced fast reactor fuel claddings fabricated from Cr16Ni15Mo3NbB and Cr16Ni15Mo2Mn2TiVB austenitic stainless steels in the cold worked condition and Cr13Mo2NbVB ferritic -martensitic steel following irradiation in the BOR-60, BN-350 and BN-600 fast reactors. The data are compared with the results obtained from a typical austenitic commercial cladding material, Cr16Ni15Mo3Nb, in the cold worked condition. The results reveal a beneficial effect of boron and other alloying elements in reducing void swelling in 16Cr-15Ni type austenitic steels. The high resistance of ferritic-martensitic steels to void swelling has been confirmed in the Cr13Mo2NbVB steel. (author)

  17. The Effect of Si and Mn on Microstructure and Selected Properties of Cr-Ni Stainless Steels

    Directory of Open Access Journals (Sweden)

    Kalandyk B.

    2017-03-01

    Full Text Available Cast stainless steel of the Cr-Ni duplex type is used, among others, for the cast parts of pumps and valves handling various chemically aggressive media. Therefore, the main problem discussed in this article is the problem of abrasion wear resistance in a mixture of SiC and water and resistance to electrochemical corrosion in a 3% NaCl-H2O solution of selected cast steel grades, i.e. typical duplex cast steel, high silicon and manganese duplex cast steel, and Cr-Ni austenitic cast steel (type AISI 316L. The study shows that the best abrasion wear resistance comparable to Ni-Hart cast iron was obtained in the cast duplex steel, where Ni was partially replaced with Mn and N. This cast steel was also characterized by the highest hardness and matrix microhardness among all the tested cast steel grades. The best resistance to electrochemical corrosion in 3% NaCl-H2O solution showed the cast duplex steel with high content of Cr, Mo and N. The addition of Ni plays rather insignificant role in the improvement of corrosion resistance of the materials tested.

  18. The oxidation behaviour of Fe-9Cr-1Mo steels

    International Nuclear Information System (INIS)

    Rowlands, P.C.; Holmes, D.R.; Whittaker, A.; Brierley, R.A.; Garrett, J.C.P.

    1983-01-01

    The oxidation behaviour of Fe9Cr1Mo steels over a wide range of conditions covering likely operating environments has been determined. In particular the effects of temperature, gas composition and materials variables on production materials have been investigated. From this work the mechanisms of protective and breakaway corrosion have broadly been elucidated. The vital role of carbon deposition in the oxide and carburisation of the metal has been determined. Aspects of the breakaway and protective oxidation mechanisms have been incorporated into a statistical model for predicting breakaway initiation and boiler component life. The results obtained from the tube life calculations indicate very low probabilities of component failure for coolant gas compositions containing up to the equivalent of 825 vppm H 2 O and 1%CO. For a more aggressive gas at the upper limit of CO concentration (2%CO) there is a small probability of failure within 25 years for finned boiler tubes. Current work may in time allow these constraints composition to be relaxed. The information gained has been used in the design of Heysham II/Torness to reduce the probabilities of 9Cr component failure to insignificant levels. (author)

  19. Impingement wastage experiments with 9Cr 1Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Kishore, S., E-mail: skishore@igcar.gov.in [IGCAR (India); Beauchamp, François; Allou, Alexandre [CEA (France); Kumar, A. Ashok; Chandramouli, S.; Rajan, K.K. [IGCAR (India)

    2016-02-15

    Highlights: • Sodium heated steam generators are crucial components of fast breeder reactors. • A leak in steam generator tube will cause sodium water reaction that damages the tubes. • A collaborative study by CEA and IGCAR was conducted to quantify the extent of damage on 9Cr 1Mo tube due to a steam/water leak. • It was compared against the predictions of PROPANA code. - Abstract: Steam Generator (SG) is one of the vital components of sodium cooled fast reactor (SFR). The main safety concern with SG is a probable sodium–water reaction. In case, one of its water/steam carrying tubes leaks, water/steam gets into contact with sodium causing sodium-water reaction, which is highly exothermic and producing corrosive NaOH and hydrogen. The ejecting reaction products at high temperature, impinges upon adjacent tubes by a process called impingement wastage. It could damage one of the neighboring tubes in a short time, if the detection and protection systems are failing. IGCAR and CEA carried out a collaborative study on impingement wastage of 9Cr 1Mo steel, which is one of the candidate materials for SFR SG tubes. The studies comprise of experimental works at IGCAR and simulation works with PROPANA code at CEA. This paper brings out the data and experience gained through this cooperative work.

  20. Reversed austenite in 0Cr13Ni4Mo martensitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Song, Y.Y., E-mail: songyuanyuan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Li, X.Y.; Rong, L.J.; Li, Y.Y. [Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Nagai, T. [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan)

    2014-01-15

    The austenite reversion process and the distribution of carbon and other alloying elements during tempering in 0Cr13Ni4Mo martensitic stainless steel have been investigated by in-situ high temperature X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The microstructure of the reversed austenite was characterized using transmission electron microscopy (TEM). The results revealed that the amount of the reversed austenite formed at high temperature increased with the holding time. Direct experimental evidence supported carbon partitioning to carbides and Ni to the reversed austenite. The reversed austenite almost always nucleated in contact with lath boundary M{sub 23}C{sub 6} carbides during tempering and the diffusion of Ni promoted its growth. The Ni enrichment and the ultrafine size of the reversed austenite were considered to be the main factors that accounted for the stability of the reversed austenite. - Highlights: • The amount of the reversed austenite formed at high temperature increases with the holding time. • STEM results directly show that carbon is mainly partitioned into the carbides and Ni into the reversed austenite. • The Ni enrichment and the ultrafine size are the main factors leading to the stabilization of the reversed austenite.

  1. The irradiation hardening of Ni-Mo-Cr and Ni-W-Cr alloy under Xe26+ ion irradiation

    Science.gov (United States)

    Chen, Huaican; Hai, Yang; Liu, Renduo; Jiang, Li; Ye, Xiang-xi; Li, Jianjian; Xue, Wandong; Wang, Wanxia; Tang, Ming; Yan, Long; Yin, Wen; Zhou, Xingtai

    2018-04-01

    The irradiation hardening of Ni-Mo-Cr and Ni-W-Cr alloy was investigated. 7 MeV Xe26+ ion irradiation was performed at room temperature and 650 °C with peak damage dose from 0.05 to 10 dpa. With the increase of damage dose, the hardness of Ni-Mo-Cr and Ni-W-Cr alloy increases, and reaches saturation at damage dose ≥1 dpa. Moreover, the damage dose dependence of hardness in both alloys can be described by the Makin and Minter's equation, where the effective critical volume of obstacles can be used to represent irradiation hardening resistance of the alloys. Our results also show that Ni-W-Cr alloy has better irradiation hardening resistance than Ni-Mo-Cr alloy. This is ascribed to the fact that the W, instead of Mo in the alloy, can suppress the formation of defects under ion irradiation.

  2. Quantitative evaluation of safety use limit for crevice corrosion in Ni-Cr-Mo alloys

    International Nuclear Information System (INIS)

    Fukaya, Yuichi; Akashi, Masatsune; Sasaki, Hidetsugu; Tsujikawa, Shigeo

    2007-01-01

    The most important problem with corrosion-resistant alloys such as stainless steels is localized corrosion. Crevice corrosion, which is a typical localized corrosion, occurs under the mildest environmental conditions. Consequently, whether crevice corrosion occurs or not is an important issue in structural material selection. This study investigated highly corrosion-resistant Ni-Cr-Mo alloys whose resistance for crevice corrosion is difficult to evaluate with the JIS G 0592 standard for common strainless steels. The optimized procedures for determining the critical potential and temperature for crevice corrosion of the alloys were developed based on the JIS method. The limits of safety usage of various Ni-Cr-Mo alloys were evaluated quantitatively in chloride solution environments. (author)

  3. An evaluation procedure of sodium environmental effects on FBR grade SUS316 (316FR) and Modified 9Cr-1Mo steel. On the basis of the studies up to the fiscal year of 1998

    International Nuclear Information System (INIS)

    1999-01-01

    Evaluation of sodium environmental effects on structural materials of fast breeder reactors (FBR's) is one of the key issues for the integrity of the plants. The Elevated Temperature Structural Design Guide for Monju (ETSDG) incorporated an evaluation procedure of sodium environmental effects in the Appendix MA.2, for the conventional steels, such as SUS304, SUS316, SUS321 and 2 1/4Cr-1Mo. Following the establishment of the ETSDG, a new material with superior elevated temperature properties, FBR grade SUS316 (316FR), has been developed, and studies on Mod.9Cr-1Mo steel (Mod.9Cr-1Mo steel) has been performed, for the application to demonstration reactors and successive large-scale reactors. These materials were shown to have, at least equal, or better compatibility with sodium compared with the conventional steels. Moreover, studies have been continued with the conventional steels, particularly with SUS304, for the further validation of the procedure in the ETSDG, especially in terms of long-term properties. Those studies provide basis for the study on 316FR. This report proposed an evaluation procedure of sodium environmental effects on 316FR and Mod.9Cr-1Mo steel, which is to be incorporated into the structural design guide for demonstration fast breeder reactors. The procedure is summarized as follows: (1) Corrosion allowance of 316FR and Mod.9Cr-1Mo can be evaluated by the equation determined in the ETSTG. (2) Strength reduction factors on design allowable values are not necessary for either steel. Strength reduction due to the transfer of carbon and nitrogen, etc does not occur with 316FR, which was the same as SUS304. Mod.9Cr-1Mo steel does not show strength reduction, contrary to 2 l/4Cr-1Mo, similar ferritic steel. (3) Corrosion allowance can be determined separately for thin-walled components. The procedure allows design without correction factors for Mod.9Cr-1Mo steel, which was not possible for 2 1/4Cr-1Mo steel in the ETSDG. (author)

  4. The Effect of Hold Time on Creep-Fatigue in 9Cr-1Mo

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Tae Young; Kim, Dae Whan; Kim, Yong Wan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Baek, Kyoung Ho [Chungnam National University, Daejeon (Korea, Republic of)

    2009-05-15

    9Cr-1Mo steel is a candidate material for reactor vessel for VHTR. Because 9Cr-1Mo steel has a good mechanical properties and a lower thermal expansion coefficient than austenitic stainless steel. The reactor vessel of VHTR is operated at about 450 .deg. C. At this temperature, fatigue occurs during start-up and cool-down, and creep occurs during normal operation. Creep-fatigue damage by the interaction between fatigue and creep is an important factor that limits VHTR reactor vessel life. In this study, Effect of hold time on low cycle fatigue behavior of 9Cr-1Mo at 600 .deg. C was investigated in air.

  5. The Effect of Hold Time on Creep-Fatigue in 9Cr-1Mo

    International Nuclear Information System (INIS)

    Oh, Tae Young; Kim, Dae Whan; Kim, Yong Wan; Baek, Kyoung Ho

    2009-01-01

    9Cr-1Mo steel is a candidate material for reactor vessel for VHTR. Because 9Cr-1Mo steel has a good mechanical properties and a lower thermal expansion coefficient than austenitic stainless steel. The reactor vessel of VHTR is operated at about 450 .deg. C. At this temperature, fatigue occurs during start-up and cool-down, and creep occurs during normal operation. Creep-fatigue damage by the interaction between fatigue and creep is an important factor that limits VHTR reactor vessel life. In this study, Effect of hold time on low cycle fatigue behavior of 9Cr-1Mo at 600 .deg. C was investigated in air

  6. Correlation of yield stress and microhardness in 08Cr16Ni11Mo3 stainless steel irradiated to high dose in the BN-350 fast reactor

    International Nuclear Information System (INIS)

    Gusev, M.N.; Maksimkin, O.P.; Tivanova, O.V.; Silnaygina, N.S.; Garner, F.A.

    2006-01-01

    The relationship between the microhardness and the engineering yield stress in 08Cr16Ni11Mo3 steel after irradiation in the BN-350 reactor has been experimentally derived and agrees with a previously published correlation developed by Toloczko for unirradiated 316 in a variety of cold-work conditions. Even more importantly, when the correlation is derived in the K Δ format where the correlation involves changes in the two properties, excellent agreement is found with a universal K Δ correlation developed by Busby and coworkers. Additionally, this report points out that microhardness measurements must take into account that sodium exposure at high temperature and neutron fluence alters the metal surface to produce ferrite, and therefore the altered layers should be removed prior to testing

  7. Supercritical water corrosion of high Cr steels and Ni-base alloys

    International Nuclear Information System (INIS)

    Jang, Jin Sung; Han, Chang Hee; Hwang, Seong Sik

    2004-01-01

    High Cr steels (9 to 12% Cr) have been widely used for high temperature high pressure components in fossil power plants. Recently the concept of SCWR (supercritical water-cooled reactor) has aroused a keen interest as one of the next generation (Generation IV) reactors. Consequently Ni-base (or high Ni) alloys as well as high Cr steels that have already many experiences in the field are among the potential candidate alloys for the cladding or reactor internals. Tentative inlet and outlet temperatures of the anticipated SCWR are 280 and 510 .deg. C respectively. Among many candidate alloys there are austenitic stainless steels, Ni base alloys, ODS alloys as well as high Cr steels. In this study the corrosion behavior of the high Cr steels and Ni base (or high Ni) alloys in the supercritical water were investigated. The corrosion behavior of the unirradiated base metals could be used in the near future as a guideline for the out-of-pile or in-pile corrosion evaluation tests

  8. Strength behaviour of 10CrMo9.10 steel in nonsteady-state applications

    International Nuclear Information System (INIS)

    Seidel, C.

    2 testing runs with cyclic temperature increase were conducted on steel 10CrMo9.10 samples, i.e., at 500 degC and cyclic increase by 10, 25 and 50 degC, and at 550 degC and cyclic increase by 50 degC. Long-term strength was studied under a strain of 6.1 to 25.6 kp/mm 2 for 22,000 hours and the effect of periodical unloading was investigated on long-term strength at 550 degC. Sample loading and unloading proceeded within the range of 8.8 to 24.7 kp/mm 2 at an unloading rate of 8 to 100 %/min. Steel lifetime was not affected by the number of cycles. The effect of the changing load and of constant temperature without load on the long-term strength of the steel at 550 degC is shown graphically. The results showed a clear dependence of steel life on dwell time at the given temperature without load. (J.P.)

  9. Crystallography of sigma phase precipitation in superaustenitic Fe-22Cr-21Ni-6Mo-0.3N stainless steels

    International Nuclear Information System (INIS)

    Lee, Tae Ho; Jung, Yun Chul; Kim, Sung Joon

    1999-01-01

    The crystallographic features of sigma phase precipitation in super austenitic Fe-22Cr-21Ni-6Mo-(0.3N) stainless steels during isothermal aging were investigated utilizing transmission electron microscopy. The sigma phase precipitated along the austenite grain boundaries even after solution treatment due to higher Mo contents and remained stable throughout aging at 900 .deg. C up to 168 hours. The sigma phase observed in this study was found to be ternary Fe-Cr-Mo sigma phase and had tetragonal structure with lattice parameters of a=9.17A and c=4.74A. The orientation relationships between the sigma phase and austenite were determined from the analyses of selected area diffraction patterns taken by various zone axes and stereo graphic analyses. The orientation relationships between sigma and austenite phases obtained in this study were as follows; 1) (110) γ ll (110) σ , [111] γ ll [001] σ and (112) γ ll (110) σ , [111] γ ll [001] σ and 2) (110) γ ll (110) σ , [112] γ ll [113] σ and (111) γ ll (332) σ , [112] γ ll [113] σ . However, the former orientation relationship was predominant throughout aging and the latter orientation relationship was scarcely observed in very limited aging condition

  10. Assessment of the integrity of ferritic-austenitic dissimilar weld joints of different grades of Cr-Mo ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Laha, K.; Chandravathi, K.S.; Parameswaran, P.; Goyal, Sunil; Mathew, M.D. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Group

    2010-07-01

    Integrity of the 2.25 Cr-1Mo / Alloy 800, 9Cr-1Mo / Alloy 800 and 9Cr-1Mo-VNb / Alloy 800 ferritic-austenitic dissimilar joints, fusion welded employing Inconel 182 electrode, has been assessed under creep conditions at 823 K. The dissimilar weld joints displayed lower creep rupture strength than their respective ferritic steel base metals. The strength reduction was more for 2.25Cr-1Mo steel joint and least for 9Cr-1Mo steel joint. The failure location in the joints was found to shift from the ferritic steel base metal to the intercritical region of heat-affected zone (HAZ) in ferritic steel (type IV cracking) with decrease in stress. At still lower stresses the failure occurred at the ferritic / austenitic weld interface. Localized creep deformation and cavitation in the soft intercritical HAZ induced type IV failure whereas creep cavitation at the weld interface particles induced ferritic / austenitic interface cracking due to high creep strength mismatch across it. Micromechanisms of type IV failure and interface cracking in the ferritic / austenitic joints and different susceptibility to failure for different grades of ferritic steels are discussed based on microstructural investigation, mechanical testing and finite element analysis. (Note from indexer: paper contains many typographical errors.)

  11. Correlation of microstructure and fracture toughness of advanced 9Cr/CrMoV dissimilarly welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Qian [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Yang, Renjie [Shanghai Turbine Works Company, Shanghai 200240 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China)

    2015-06-25

    In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly welded joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly welded joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of welded joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole welded joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.

  12. Effect of quenching temperature on martensite multi-level microstructures and properties of strength and toughness in 20CrNi2Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Long, Shao-lei [College of Materials Science and Metallurgical Engineering, Guizhou University (China); Guizhou Key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China); Liang, Yi-long, E-mail: liangyilong@126.com [College of Materials Science and Metallurgical Engineering, Guizhou University (China); Guizhou Key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China); Jiang, Yun [Guizhou Key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China); Liang, Yu; Yang, Ming; Yi, Yan-liang [College of Materials Science and Metallurgical Engineering, Guizhou University (China); Guizhou Key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China)

    2016-10-31

    The martensite multi-level microstructures of 20CrNi2Mo steel, which were quenched at the different temperatures of 900–1200 °C and tempered at 200 °C, were investigated by optical microscope (OM), scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM), and the relationship between the microstructures and properties of strength and toughness was discussed by the classic formula of Hall–Petch. The results show that the size of prior austenite grain (d{sub r}), martensite packet (d{sub p}) and block (d{sub b}) increase with increasing of the quenching temperature, while the martensite lath (d{sub l}) size is opposite. On another hand, the confusion degree of the martensite packets changes from disorder to order. The boundaries of prior austenite grain, packet, block and the martensite lath are high angle boundaries (HBs) and low angle boundaries (LBs), respectively, and the ratio of the low angle boundaries increase with the quenching temperature by calculating to the multi-level microstructure size with the mathematical model established by myself. In addition, the relationship between the packet/block and strength follows the classical formula of Hall–Petch, and the size of d{sub b} is far lower than the size of d{sub p}, d{sub b} is the effective control unit of the strength. Meanwhile, d{sub l} is the effective control unit of toughness because it strongly impacts the crack initiation and propagation and follows also the Hall-Petch with toughness in 20CrNi2Mo steel.

  13. Quantification by image analysis of grain size of the high temperature phase (austenite) of martensitic steels 9Cr-1Mo

    International Nuclear Information System (INIS)

    Barcelo, F.; Brachet, J.C.

    1993-01-01

    In martensitic steels, the austenitic grain size before transformation may influence mechanical properties. 9Cr-1Mo steel (EM10) is used in hexagonal pipes fabrication in fast neutrons reactors. Image analysis allows to quantify the older grain size in function of the austenization heat treatment conditions. (A.B.). 2 figs

  14. Hydrogen induced plastic damage in pressure vessel steel of 2.25Cr-1Mo

    International Nuclear Information System (INIS)

    Han, G.W.; Song, Y.J.

    1995-01-01

    2.25Cr-1Mo steel is generally employed as a hydrogenation reaction vessel material used at elevated temperature and in a hydrogen containing environment. During service of the reaction vessel, a large number of hydrogen atoms would enter its wall. When the reaction vessel is shutdown and the temperature reduces to about ambient temperature, the hydrogen atoms remaining in the wall would induce plastic damage in the steel. The mechanism of hydrogen induced plastic damage is different for various materials with different microstructures. Investigations have demonstrated that the hydrogen induced plastic damage in carbide annealed carbon steels is caused by hydrogen accelerating the initiating and growing of microvoids from the carbide particles. However, SEM examination on the fracture surface of hydrogen charged tensile specimen of 2.25Cr-1Mo steel show that a large number of fisheyes appear on the fracture surface. This indicates that hydrogen induced plastic damage in 2.25Cr-1Mo steel is related to the occurrence of fisheye cracks during plastic deformation. By means of micro-fracture mechanics to analyze fisheye crack occurrence from the first generation microvoid, the mechanism of hydrogen induced plastic damage in the pressure vessel steel is investigated

  15. Influence of dynamic sodium environment on the creep-fatigue behaviour of Modified 9Cr-1Mo ferritic-martensitic steel

    International Nuclear Information System (INIS)

    Kannan, R.; Ganesan, V.; Mariappan, K.; Sukumaran, G.; Sandhya, R.; Mathew, M.D.; Bhanu Sankara Rao, K.

    2011-01-01

    Highlights: → The effects of dynamic sodium on the CFI behaviour of Mod. 9Cr-1Mo steel has investigated. → The cyclic stress response of Mod. 9Cr-1Mo steel under flowing sodium environment is similar to that of air environment. → The creep-fatigue endurance of the alloy is found to decrease with introduction of hold time and with increase in the duration of hold time and the factor of life increase in sodium compared to air environment is reduced with increase in hold time. → In contrast to air environment, tensile holds were found to be more damaging than compression hold in sodium environment. → Design rules based on air environment can be safely applied for the components operating in sodium environment. - Abstract: The use of liquid sodium as a heat transfer medium for sodium-cooled fast reactors (SFRs) necessitates a clear understanding of the effects of dynamic sodium on low cycle fatigue (LCF), creep and creep-fatigue interaction (CFI) behaviour of reactor structural materials. Mod. 9Cr-1Mo ferritic steel is the material of current interest for the steam generator components of sodium cooled fast reactors. The steam generator has a design life of 30-40 years. The effects of dynamic sodium on the LCF and CFI behaviour of Mod. 9Cr-1Mo steel have been investigated at 823 and 873 K. The CFI life of the steel showed marginal increase under flowing sodium environment when compared to air environment. Hence, the design rules for creep-fatigue interaction based on air tests can be safely applied for components operating in sodium environment. This paper attempts to explain the observed LCF and CFI results based on the detailed metallography and fractography conducted on the failed samples.

  16. Metallographical investigations on cavitation erosion of the steel X 2 CrNiMoN 22 5 3

    International Nuclear Information System (INIS)

    Pohl, M.; Goecke, A.

    1989-01-01

    The development of erosion-resistant material, however, presupposes a precise knowledge of the mechanism and progress of the destruction. For this reason, cavitation erosion was studied in this investigation using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultra-microhardness tests (UMHT) - as well as gravimetry. A Cr-Ni-Mo steel with a ferritic-austenitic structure was investigated. This material was selected to provide information about the possible interaction between the phases within such a structure and about the damage mechanism of the individual phases. The experimental material was modified by a heat treatment to precipitate the σ-phase so that a three-phase model material could be obtained as well as the two-phase alloy. (orig./MM) [de

  17. Effect of chemical composition on irradiation embrittlement and annealing in Ni-Cr-Mo-V reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Novosad, P [Czech Nuclear Society, Prague (Czech Republic)

    1994-12-31

    Results concerning copper and phosphorus influence on radiation-induced changes in the Ni-Cr-Mo-V steel mechanical properties, are presented. Correlations between different mechanical properties for steels with different chemical composition, are presented. A comparison of transition temperature shifts obtained for static and dynamic fracture toughness tests and Charpy impact tests, is discussed. Recovery of radiation hardening, measured by hardness test after isochronal annealing of steels with different compositions, is also shown. Copper content strongly affects irradiation-induced changes of mechanical properties, but phosphorus content in connection with variable copper content has only a small effect. (author). 4 refs., 4 figs., 4 tabs.

  18. Diffusion complex layers of TiC-Ni-Mo type produced on steel during vacuum titanizing process combined with the electrolytic deposition

    International Nuclear Information System (INIS)

    Kasprzycka, E.; Krolikowski, A.

    1999-01-01

    Diffusion carbide layers produced on steel surface by means of vacuum titanizing process have been studied. A new technological process combining a vacuum titanizing with an electrolytic deposition of Ni-Mo alloy has been proposed to increase of corrosion resistance of carbide layers. The effect of preliminary electrolytic deposition of Ni-Mo alloy on the NC10 steel surface on the titanized layer structure and its corrosion resistance has ben investigated. As a result, diffusion complex layers of TiC-Ni-Mo type on NC10 steel surface have been obtained. An X-ray structural analysis of titanized surfaces on NC10 steel precovered with an electrolytic Ni-Mo alloy coating (70%Ni+30%Mo) revealed a presence of titanium carbide TiC, NiTi, MoTi and trace quantity of austenite. The image of the TiC-Ni-Mo complex layer on NC10 steel surface obtained by means of joined SEM+TEM method and diagrams of elements distribution in the layer diffusion zone have been shown. Concentration of depth profiles of Ti, Ni, Mo, Cr and Fe in the layer diffusion zone obtained by means of the joined EDS+TEM method are shown. Concentration depth profiles of Ti, Ni, Mo, Cr and Fe in the layer diffusion zone obtained by means of the X r ay microanalysis and microhardness of the layer are shown. An X-ray structural analysis of titanized surfaces on the NC10 steel, without Ni-Mo alloy layer, revealed only a substantial presence of titanium carbide TiC. For corrosion resistance tests the steel samples with various diffusion layers and without layers were used: (i) the TiC-Ni-Mo titanized complex layers on NC10 steel, (ii) the TiC titanized carbide layers on the NC10 steel, (iii) the NC10 steel without layers. Corrosion measurements of sample under test have been performed in 0.1 M H 2 SO 4 by means of potentiodynamic polarization and electrochemical impedance tests. It has been found that the corrosion resistance of titanized steel samples with the TiC and TiC-Ni-Mo layers is higher than for the steel

  19. Nondestructive testing for microstructural characterization in 9Cr-1Mo ferritic steel towards assessment of fabrication quality and in-service degradation

    Energy Technology Data Exchange (ETDEWEB)

    Jayakumar, T.; Rao, K.B.S.; Raj, Baldev [Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    1999-07-01

    The paper discusses the usefulness of non destructive testing for microstructural characterization in 9Cr-1Mo ferritic steel. Ultrasonic velocity and attenuation measurements and spectral analysis have been used in a complementary way for characterizing Ac{sub 1} and Ac{sub 3} temperatures, amount of martensite and ferrite, dissolution of V{sub 4}C{sub 3} and NbC and formation of {delta}-ferrite. The microstructural degradation occurring due to thermal ageing and creep has also been studied by ultrasonic velocity measurements. Magnetic Barkhausen noise technique has been used for estimating the extent of various regions in heat affected zone (HAZ) of 9Cr-1Mo ferritic steel weldment. The same technique has been used for the assessment of low cycle fatigue damage in 9Cr-1Mo steel. The study establishes that non destructive methods can be used for the assessment of fabrication quality and in service degradation of the components. (author)

  20. Comparison of the segregation behavior between tempered martensite and tempered bainite in Ni-Cr-Mo high strength low alloy RPV steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Kim, Min Chul; Kim, Hyung Jun; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    SA508 Gr.4N Ni-Cr-Mo low alloy steel has an superior fracture toughness and strength, compared to commercial Mn-Mo-Ni low alloy RPV steel SA508 Gr.3. Higher strength and fracture toughness of low alloy steels could be obtained by adding Ni and Cr. So several were performed on researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and term of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, the resistance of thermal embrittlement in the high temperature range including temper embrittlement is required. S. Raoul reported that the susceptibility to temper embrittlement was increasing a function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So the comparison of temper embrittlement behavior was made between martensitic microstructure and bainitic microstructure with a viewpoint of boundary features in SA508 Gr.4N, which have mixture of tempered bainite/martensite. We have compared temper embrittlement behaviors of SA508 Gr.4N low alloy steel with changing volume fraction of martensite. The mechanical properties of these low alloy steels were evaluated after a long-term heat treatment. Then, the the segregated boundaries were observed and segregation behavior was analyzed by AES. In order to compare the misorientation distributions of model alloys, grain boundary structures were measured with EBSD

  1. Effects of sodium environment on the mechanical properties of Fe-2 1/4Cr-1Mo steel

    International Nuclear Information System (INIS)

    Chopra, O.K.

    Mechanical property data on isothermally annealed, thermally aged, and sodium-exposed Fe-2 1/4Cr-1Mo steel are analyzed to evaluate the influence of the sodium environment as well as the effects of the microstructural and compositional changes that occur in the steel during long-term exposure to sodium. Correlations are developed to predict the environmental effects on tensile, creep, fatigue, and creep-fatigue properties of Fe-2 1/4Cr-1Mo steel in sodium. The results indicate that at temperatures <823 K (550 deg. C), degradation of mechanical properties is essentially due to thermal aging. Loss of carbon from the steel reduces both the tensile and creep-rupture strength, but has little or no effect on the fatigue properties. The cyclic properties of Fe-2 1/4Cr-1Mo steel in sodium are superior to those in air. The creep-fatigue behaviour in sodium is significantly different from that in an air environment. The creep-fatigue data are analyzed using the interactive damage rate equations to predict the time-dependent fatigue bahaviour of isothermally annealed Fe-2 1/4Cr-1Mo steel in sodium. (author)

  2. Effects of sodium environment on the mechanical properties of Fe-2 1/4Cr-1Mo steel

    International Nuclear Information System (INIS)

    Chopra, O.K.

    1983-09-01

    Mechanical property data on isothermally annealed, thermally aged, and sodium-exposed Fe-2 1/4Cr-1Mo steel are analyzed to evaluate the influence of the sodium environment as well as the effects of the microstructural and compositional changes that occur in the steel during long-term exposure to sodium. Correlations are developed to predict the environmental effects on tensile, creep, fatigue, and creep-fatigue properties of Fe-2 1/4Cr-1Mo steel in sodium. The results indicate that at temperatures 0 C), degradation of mechanical properties is essentially due to thermal aging. Loss of carbon from the steel reduces both the tensile and creep-rupture strength, but has little or no effect on the fatigue properties. The cyclic properties of Fe-2 1/4Cr-1Mo steel in sodium are superior to those in air. The creep-fatigue behavior in sodium is significantly different from that in an air environment. The creep-fatigue data are analyzed using the interactive damage rate equations to predict the time-dependent fatigue behavior of isothermally annealed Fe-2 1/4Cr-1Mo steel in sodium. 15 references, 7 figures, 1 table

  3. Processing parameters for the mechanical working of 9 Cr-1 Mo steel: processing maps approach

    Energy Technology Data Exchange (ETDEWEB)

    Sivaprasad, P.V.; Mannan, S.L.; Prasad, Y.V.R.K. [Indira Ghandi Centre for Atomic Research, Tamilnadu (India)

    2004-12-15

    Processing and instability maps using a dynamic materials model have been developed for 9Cr-1Mo steel in the temperature range 850 to 1200{sup o}C and strain rate range 0.001-100 s{sup -1} with a view to optimising its hot workability. The efficiency of power dissipation increased with increase in temperature and decrease in strain rate. The 9Cr-1Mo material exhibited two dynamic recrystallisation domains, one with a peak efficiency of 37% occurring at 950{sup o}C and 0.001 s{sup -1} and the other with a peak efficiency of 35% occurring at 1200{sup o}C and 0.1 s{sup -1}. These results are in good agreement with those found in industry. (author)

  4. Creep behaviour of modified 9Cr-1Mo ferritic steel

    International Nuclear Information System (INIS)

    Choudhary, B.K.; Isaac Samuel, E.

    2011-01-01

    Creep deformation and fracture behaviour of indigenously developed modified 9Cr-1Mo steel for steam generator (SG) tube application has been examined at 823, 848 and 873 K. Creep tests were performed on flat creep specimens machined from normalised and tempered SG tubes at stresses ranging from 125 to 275 MPa. The stress dependence of minimum creep rate obeyed Norton's power law. Similarly, the rupture life dependence on stress obeyed a power law. The fracture mode remained transgranular at all test conditions examined. The analysis of creep data indicated that the steel obey Monkman-Grant and modified Monkman-Grant relationships and display high creep damage tolerance factor. The tertiary creep was examined in terms of the variations of time to onset of tertiary creep with rupture life, and a recently proposed concept of time to reach Monkman-Grant ductility, and its relationship with rupture life that depends only on damage tolerance factor. SG tube steel exhibited creep-rupture strength comparable to those reported in literature and specified in the nuclear design code RCC-MR.

  5. Some elevated temperature tensile and strain-controlled fatigue properties for a 9%Cr1Mo steel heat treated to simulate thick section material

    International Nuclear Information System (INIS)

    Sanderson, S.J.; Jacques, S.

    Current interest has been expressed in the usage of thick section 9%Cr1%Mo steel, particularly for UK Commercial Demonstration Fast Reactor (CDFR) steam generator tubeplates. This paper presents the results of some preliminary mechanical property test work on a single cast of the steel, heat treated to simulate heavy ruling sections encompassing thicknesses likely to be met in the CDFR context. The microstructures of the simulated thick section material were found to remain predominantly as tempered martensite even at the slowest transformation cooling rates used (50 deg. C/h). The effect of microstructure is reflected in the elevated temperature proof stress, tensile strength and strain-controlled fatigue endurance which were found to be comparable with the properties established for thin section normalised and tempered 9%Cr1%Mo steel. These results are extremely encouraging and, taken in conjunction with the results from other simulation work on this material, further demonstrate the potential of thick section 9%Cr1%Mo steel. (author)

  6. Enhancement of tribological properties of 9Cr18 stainless steel by dual Mo and S Co implantation

    International Nuclear Information System (INIS)

    Zhang Tao; Song Jiaohua; Li Guoqing; Chu, Paul K.; Brown, Ian G.

    2001-01-01

    Mo and S ions were simultaneously implanted into 9Cr18 stainless steel samples. The frictional properties of the implanted samples were assessed using a pin-on-disk tester and the elemental depth profiles were measured by Auger electron spectroscopy. The hardness of the samples was also measured. We find that this dual-element implantation process reduces the coefficient of friction by a factor of 2 and increases the low-friction lifetime by a factor of 4 compared to the 9Cr18 surface with Mo or S implantation alone. This enhancement is related to the synergistic coexistence of the implanted elements at the same place. We have also investigated the process using computer simulation. The simulation results help disclose the characteristics of the modified layer and explain the effects of dual-element ion implantation

  7. The effect of spheroidizing by thermal cycling in low concentration Cr-Mo alloy steel

    International Nuclear Information System (INIS)

    Yun, H.S.; Kang, C.Y.

    1979-01-01

    An intensive study was carried out on spheroidizing of pearlite (Sph) and number of spherical carbide in proeutectoid ferrite (No/100) of low concentration Cr-Mo steel with thermal cycling. Physical and mechanical properties of steel containing 0.33 % C with thermal cycling were compared with those of low concentration Cr-Mo steel with thermal cycling. The effect of normal heat treatment and cooling rate on spheroidizing of pearlite and precipitation of fine spherical carbide in the steels were investigated. The results obtained were as follows: 1) Thermal cycling of low concentration Cr-Mo steel promoted the spheroidizing of pearlite compared with that of steel without Cr and Mo to steel had significant effect on spheroidizing of pearlite. 2) Number of fine spherical carbides of low concentration Cr-Mo steel with thermal cycling was over 5 times to that of fine spherical carbides of hypoeutectoid steel with thermal cycling. 3) Spheroidizing of pearlite and number of fine spherical carbide in proeutectoid ferrite of low concentration Cr-Mo steel with increasing thermal cycle and cooling rate. 4) Hardness of steel with thermal cycling was decreased. However, low concentration Cr-Mo steel had little decreasing rate in hardness with increasing thermal cycle on the basis of 100 times in thermal cycle. Therefore, toughness was considered to be increased with increasing spheroidizing of pearlite without changing mechanical properties. (author)

  8. Technology development and production of elongated shell for reactor vessel active zone of WWER-TOI project from steel 15Cr2NiMoVN class 1

    International Nuclear Information System (INIS)

    Shklyaev, S.Eh.; Titova, T.I.; Ratushev, D.V.; Shul'gan, N.A.; Eroshkin, S.B.; Durynin, V.A.; Efimov, S.V.; Dub, V.S.; Kulikov, A.P.; Romashkin, A.N.

    2015-01-01

    Production process for the elongated shell blank of the active zone of the reactor pressure vessel made from steel 15Cr2NiMoVN Class 1 with finished sizes Dext=4.655 mm, Dint=4.240 mm, H=4.910 mm (height for heat treatment – 5.750 mm) is presented. For the first time in Russia in production site of OMZ-Special steel LLC a unique elongated shell blank of the reactor vessel active zone was made from ingot 420.0 t for WWER-TOI project fully meeting the specified requirements in terms of metallurgical quality and set of service properties [ru

  9. Corrosion critique of the 2 1/4 Cr--1 Mo steel for LMFBR steam generation system applications

    International Nuclear Information System (INIS)

    Zima, G.E.

    1977-07-01

    The unstabilized ferritic steel of nominal composition, 2 1 / 4 Cr-1Mo, has been proposed for critical structural assignments in LMFBR powerplants, specifically: the tubing, tubesheet and shell of the evaporator and superheater components. The interest in this steel has been based on a presumably favorable general corrosion property spectrum, acceptable mechanical properties and fabricability, and certain economies associated with the low alloy content. This report is an attempt at a general corrosion assessment for the 2 1 / 4 Cr-1Mo steel and an identification of corrosion problem areas potential to this steel from the sodium and water/steam systems of the proposed working environment. There is a considerable area of uncertainty in the sodium-side response of 2 1 / 4 Cr-1Mo steel, centered in the loss and redisposition of carbon during long-term exposure to sodium of various impurity backgrounds. It is submitted that present evidence relating to the water/steam-side corrosion behavior of the 2 1 / 4 Cr-1Mo steel, under nominal and conceivable perturbed environmental conditions, constitutes the principal concern for the proposed LMFBR powerplant applications of this steel. It is suggested that this unfavorable corrosion aspect represents an inherent limitation of the low alloy content of this steel, probably largely independent of melting and processing recourses, and it is a sufficient basis to question the incentive for a continuation of the collateral studies of this steel for the proposed LMFBR steam generation system assignments

  10. Prediction and Monitoring Systems of Creep-Fracture Behavior of 9Cr-1Mo Steels for Reactor Pressure Vessels

    International Nuclear Information System (INIS)

    Potirniche, Gabriel; Barlow, Fred D.; Charit, Indrajit; Rink, Karl

    2013-01-01

    A recent workshop on next-generation nuclear plant (NGNP) topics underscored the need for research studies on the creep fracture behavior of two materials under consideration for reactor pressure vessel (RPV) applications: 9Cr-1Mo and SA-5XX steels. This research project will provide a fundamental understanding of creep fracture behavior of modified 9Cr-1Mo steel welds for through modeling and experimentation and will recommend a design for an RPV structural health monitoring system. Following are the specific objectives of this research project: Characterize metallurgical degradation in welded modified 9Cr-1Mo steel resulting from aging processes and creep service conditions; Perform creep tests and characterize the mechanisms of creep fracture process; Quantify how the microstructure degradation controls the creep strength of welded steel specimens; Perform finite element (FE) simulations using polycrystal plasticity to understand how grain texture affects the creep fracture properties of welds; Develop a microstructure-based creep fracture model to estimate RPVs service life; Manufacture small, prototypic, cylindrical pressure vessels, subject them to degradation by aging, and measure their leak rates; Simulate damage evolution in creep specimens by FE analyses; Develop a model that correlates gas leak rates from welded pressure vessels with the amount of microstructural damage; Perform large-scale FE simulations with a realistic microstructure to evaluate RPV performance at elevated temperatures and creep strength; Develop a fracture model for the structural integrity of RPVs subjected to creep loads; and Develop a plan for a non-destructive structural health monitoring technique and damage detection device for RPVs.

  11. Prediction and Monitoring Systems of Creep-Fracture Behavior of 9Cr-1Mo Steels for Teactor Pressure Vessels

    Energy Technology Data Exchange (ETDEWEB)

    Potirniche, Gabriel [Univ. of Idaho, Moscow, ID (United States); Barlow, Fred D. [Univ. of Idaho, Moscow, ID (United States); Charit, Indrajit [Univ. of Idaho, Moscow, ID (United States); Rink, Karl [Univ. of Idaho, Moscow, ID (United States)

    2013-11-26

    A recent workshop on next-generation nuclear plant (NGNP) topics underscored the need for research studies on the creep fracture behavior of two materials under consideration for reactor pressure vessel (RPV) applications: 9Cr-1Mo and SA-5XX steels. This research project will provide a fundamental understanding of creep fracture behavior of modified 9Cr-1Mo steel welds for through modeling and experimentation and will recommend a design for an RPV structural health monitoring system. Following are the specific objectives of this research project: Characterize metallurgical degradation in welded modified 9Cr-1Mo steel resulting from aging processes and creep service conditions; Perform creep tests and characterize the mechanisms of creep fracture process; Quantify how the microstructure degradation controls the creep strength of welded steel specimens; Perform finite element (FE) simulations using polycrystal plasticity to understand how grain texture affects the creep fracture properties of welds; Develop a microstructure-based creep fracture model to estimate RPVs service life; Manufacture small, prototypic, cylindrical pressure vessels, subject them to degradation by aging, and measure their leak rates; Simulate damage evolution in creep specimens by FE analyses; Develop a model that correlates gas leak rates from welded pressure vessels with the amount of microstructural damage; Perform large-scale FE simulations with a realistic microstructure to evaluate RPV performance at elevated temperatures and creep strength; Develop a fracture model for the structural integrity of RPVs subjected to creep loads; and Develop a plan for a non-destructive structural health monitoring technique and damage detection device for RPVs.

  12. Experiences with new and improved oil quenched CrMoV rotor materials

    International Nuclear Information System (INIS)

    Ewald, J.; Keienburg, K.H.; Wiemann, W.; Sauer, D.L.

    1987-01-01

    The improvement gained with 1% CrMoNiV rotors of modern manufacturing processes are described. It was possible to raise the creep strength as well as the toughness level. The aim of this paper is to present representative data from older 1% CrMoNiV rotors and to compare them with test results from rotors of modern steel making technology and with improved chemical composition. The results prove, that the todays oil quenched version of the 1% CrMoNiV rotor material represents a good compromise with respect to creep rupture and (fracture) toughness behaviour. In addition the 1% CrMoNiV-steels have a stable microstructure which implements minor changes of properties during long term service

  13. Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

    Science.gov (United States)

    Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

    1994-09-01

    The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement.

  14. Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

    International Nuclear Information System (INIS)

    Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

    1994-01-01

    The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement. ((orig.))

  15. Heat treated 9 Cr-1 Mo steel material for high temperature application

    Science.gov (United States)

    Jablonski, Paul D.; Alman, David; Dogan, Omer; Holcomb, Gordon; Cowen, Christopher

    2012-08-21

    The invention relates to a composition and heat treatment for a high-temperature, titanium alloyed, 9 Cr-1 Mo steel exhibiting improved creep strength and oxidation resistance at service temperatures up to 650.degree. C. The novel combination of composition and heat treatment produces a heat treated material containing both large primary titanium carbides and small secondary titanium carbides. The primary titanium carbides contribute to creep strength while the secondary titanium carbides act to maintain a higher level of chromium in the finished steel for increased oxidation resistance, and strengthen the steel by impeding the movement of dislocations through the crystal structure. The heat treated material provides improved performance at comparable cost to commonly used high-temperature steels such as ASTM P91 and ASTM P92, and requires heat treatment consisting solely of austenization, rapid cooling, tempering, and final cooling, avoiding the need for any hot-working in the austenite temperature range.

  16. Structural evolution of Fe-18Ni-16Cr-4Al steel during aging at 950 .deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Man; Jang, Jinsung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Zhou, Zhangjian [School of Materials Science and Engineering, USTB, Beijing (China)

    2015-05-15

    Austenitic stainless steels are also among important structural materials for in-core components of nuclear reactors, and the performance, the oxidation resistance as well as the mechanical strength at high temperature are further expected after Fukushima accident. Alumina-forming austenitic (AFA) steel was first developed by Y. Yamamoto et al. , which showed a good combination of oxidation resistance and creep resistance. The strengthening is achieved through nano-sized MX and Laves. Microstructural evolution of Fe-18Ni-16Cr-4Al during aging at 950 .deg. C was studied. This steel consists of two phases of austenite and ferrite. During aging, needle-shaped NiAl precipitates in austenite, while round shaped NiAl form in ferrite, which is supposed to be due to different crystal structural parameters.

  17. Comparative study of creep behaviour in three Cr Ni 15/15 steel stabilized with Ti and with different contents in W, Mn, Mo and Bor

    International Nuclear Information System (INIS)

    Solano, R.R.; Rivas, M. de las; Schirra, M.; Seith, B.

    1975-01-01

    The main difference between the three steels which are tested at temperature range from 650 0 C to 750 0 C is due to the hardening elements pf the matrix and the Boron content: 1. 12R72HV (X10NiCrMoTiB 1515) 2% Mn 1,5% Mo 80 ppmB 2. Vaccutherm (X12CrNiWTi 1613) 3% W 2,5 ppmB 3. RGT 21 (X12CrNiWTi 1613) 3% W 50 ppm B. The investigations of all casts are carried out in two different heat treatments which are suitable for the conditions required for the operation of the reactor. Cond. I: 1150 0 C 30 min, water quenced; 800 0 32 hour, air; 10% cold work. Cond. II: 1150 0 C 30 min, water quenched; 10% cold work. In connection with creep test the condition I irrespective of 3 steels show no remarkable difference. The observation at 750 0 C test temperature and also at condition II above 650 0 C on Boron-free Vaccutherm cast shows an unfavourable behaviour. There is no significant difference in the stress dependence of secondary creep rate and also absolute creep rate. A definite superiority is to be found for 12R72HV when considering the values for time-yield-limit-ratio and ductility compared to the W-steels. The test results shows different fracture behaviour. Transcrystalline fracture is found on cast 12R72HV, whereas RGT 21 and Vaccutherm show transition from transcrystalline to intercrystalline fracture, depending on the rupture time and test temperature. The long term rupture specimens show intercrystalline fracture. (author)

  18. Thermal fatigue strength estimation of 2.25Cr-1Mo steel under creep-fatigue interaction

    International Nuclear Information System (INIS)

    Kuwahara, Kazuo; Nitta, Akihito; Kitamura, Takayuki

    1980-01-01

    A 2-1/4Cr-1Mo steel is one of principal materials for high temperature equipments in nuclear and thermal power plants. The authors experimentally analyzed the high temperature fatigue strength and creep strength of a 2-1/4 Cr-1Mo steel main steam pipe which had been used in a thermal plant for operation up to 130,000 hours, and pointed out that the strain-range vs. life curves crossed each other due to the difference of temperature-strain phase in thermal fatigue. This suggests that it is difficult to estimate thermal fatigue life of steel materials having been subjected to different temperature-strain phase on the basis of isothermal low-cycle fatigue life at the upper limit temperature of thermal fatigue, and that it is urgently required to establish an appropriate method of evaluating thermal fatigue life. The authors attempted to prove that the strain range partitioning method used for the evaluation of thermal fatigue life in SUS 304 steels is applicable to this 2-1/4Cr-1Mo steel. Consequently, it was found that the thermal fatigue life could be estimated within a factor of 2.5 by the application of this method. (author)

  19. Carbon transfer between 2 1/4 Cr 1 Mo alloy and austenitic steels (experiments in anisothermal loops)

    International Nuclear Information System (INIS)

    Baque, P.; Besson, M.; Champeix, L.; Donati, J.R.; Oberlin, C.; Saint-Paul, P.

    1976-01-01

    Studies on carbon transfer between the ferritic steel 2 1/4 Cr 1 Mo and the austenitic steels 316L and 321H have shown that there is not any measurable carbon transfer in the operating conditions of the secondary circuit of PHENIX (475 deg C was the maximal temperature of the 2 1/4 Cr 1 Mo steel). A significant carbon transfer has been observed between the ferritic steel and the 316L steel when the 321H was replaced by the 2 1/4 Cr 1 Mo steel in the same thermohydraulic conditions (the ferritic steel was then used up to 545 deg C). This experiment has demonstrated the importance of the temperature and the initial carbon content of the ferritic steel as parameters in the decarburization process. It appears that decarburization may not be sensitive to the thermohydraulic conditions at least in the range investigated in those experiments. In the other hand the 316L steel is observed to have been carburized, the degree of carburization remaining appreciably constant and independent on the temperature between 400 deg C and 550 deg C [fr

  20. Effect of heat treatment on pitting corrosion of austenitic Cr-Ni-Mo steels in sodium chloride solution

    International Nuclear Information System (INIS)

    Stefec, R.; Franz, F.; Holecek, A.

    1979-01-01

    The pitting corrosion resistance of Cr17Ni12Mo2,5 type steel under potentiostatic polarization in a sodium chloride solution is adversely affected by previous annealing. The data obtained were systematically dependent on annealing temperature, time and surface roughness. The corrosion current, the number of pits or the mean area of pit opening and the corrosion rate within the pits were increased by previous annealing at 550 to 750 0 C for 1-100 hrs. The highest corrosion rate estimated corresponded to heat treatments provoking severe sensitization to intergranular corrosion. The paercentage area of corrosion pit openings and the estimated pit penetration rates were several times higher for as-machined than for polished surfaces. It can be assumed that pitting corrosion is little affected by the carbon content and that molybdenum depletion of grain-boundary zones is responsible for the reduced pitting resistance of annealed steels. (orig./HP) [de

  1. Experimental study on kinematic hardening of 1Cr18Ni9Ti stainless steel under low cycle fatigue

    International Nuclear Information System (INIS)

    Shao Er; Yang Xianjie; Mao Jianghui; Sun Yafang

    2006-01-01

    To study the effect of the monotonic loading on subsequent cyclic plastic hardening and flow properties of 1Cr18Ni9Ti steel, an experimental study of the low cycle fatigue tests with mean strains for 1Cr18Ni9Ti stainless steel was carried out. An analysis on the evolutions of the yield surface radius and the back stresses under symmetric and asymmetric cyclic strain loading with different strain amplitudes was made. The dependence of the evolutions of the material kinematic hardening and isotropic hardening on the strain amplitude and mean strain was observed. These results provide the experimental foundation for the constitutive model of the material under combined monotonic and cyclic complicated loads. (authors)

  2. The permeation behavior of deuterium through 1Cr18Ni9Ti stainless steel with TiN+TiC-TiN multiple films

    International Nuclear Information System (INIS)

    Xiong, Y.; Song, J.; Luo, D.; Lei, Q.; Chen, C.

    2015-01-01

    The prevention of tritium losses via permeation through structure components is an important issue in fusion technology. The production of thin layers on materials with low diffusivity and/or low surface recombination constants (so-called permeation barriers) seems to be the most practical method to reduce or hinder the permeation of tritium through materials. TiN+TiC+TiN multiple films are deposited on the surface of 1Cr18Ni9Ti stainless steel by ion-beam assisted deposition technology. The characteristics of films are tested by XPS ASEM and XRD, which shows that the film are compact and uniform with a thickness of about 15 μm, and have a good adherence with the substrate below 773 K. The diffraction peaks in the XRD patterns for TiC and TiN are broadened, implying that the multiple films are deposited on the surface of 1Cr18Ni9Ti stainless steel. Meanwhile, the C-H bonded CH 4 -appears in the infrared spectra of multiple films, suggesting that the CH 4 - is in a static state, so hydrogen atom cannot migrate from the site bonded with carbon to a neighboring site. The measured deuterium permeability in 1Cr18Ni9Ti stainless steel coated with multiple films is 2-3 orders of magnitude lower than that of pure 1Cr18Ni9Ti stainless steel substrate from 473 K to 773 K. However, this barrier is partly destroyed above 773 K

  3. Corrosion behavior of steels in liquid lead bismuth with low oxygen concentrations

    Science.gov (United States)

    Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru

    2008-02-01

    Corrosion tests in pots were conducted to elucidate corrosion behavior of various steels in liquid lead-bismuth for 3000 h under the condition of an oxygen concentration of 5 × 10 -8 wt% at 450 °C and an oxygen concentration of 3 × 10 -9 wt% at 550 °C, respectively. Significant corrosion was not observed at 450 °C for ferritic/martensitic steels, F82H, Mod.9Cr-1Mo steel, 410SS, 430SS except 2.25Cr-1Mo steel. Pb-Bi penetration into steels and dissolution of elements into Pb-Bi were severe at 550 °C even for ferritic/martensitic steels. Typical dissolution attack occurred for pure iron both at 550 °C without surface Fe 3O 4 and at 450 °C with a thin Fe 3O 4 film. Ferritization due to dissolution of Ni and Cr, and Pb-Bi penetration were recognized for austenitic stainless steels, 316SS and 14Cr-16Ni-2Mo steel at both temperatures of 450 °C and 550 °C. The phenomena were mitigated for 18Cr-20Ni-5Si steel. In some cases oxide films could not be a corrosion barrier in liquid lead-bismuth.

  4. Molybdenum depletion around P-phases Ni-Cr-Mo-W weld metals

    International Nuclear Information System (INIS)

    Silva, Cleiton Carvalho; Miranda, Helio Cordeiro de; Farias, Jesualdo Pereira

    2010-01-01

    This work evaluated the local chemical composition in matrix/precipitate interface in a Ni-Cr-Mo-W alloy weld metals deposited on substrate of C-Mn steel. The microstructural characterization was carried out through optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The results had shown that the presence of secondary phases precipitates in the interdendritic region. Through SEM analysis were observed indications of depletion of Mo around these phases. These precipitates were identified as P-phase by TEM analysis. The Mo depletion indications were confirmed through EDS. The Mo depletion was a result of a reheating due to several welding heat cycles deposited to promote the coating layer. (author)

  5. Caustic cracking of 2 1/4 CrMo steel

    International Nuclear Information System (INIS)

    Cowen, H.C.; Thorley, A.W.

    1983-12-01

    Stress corrosion cracking tests performed on the 21/4 Cr Mo ferritic steel are described. The principal environments studied were strong, aqueous caustic soda, molten anhydrous caustic soda, and caustic soda with an addition of sodium. Emphasis has been placed on material in the quenched-hardened condition. (author)

  6. Effect of carbon activity on the creep behaviour of 21/4Cr, 1Mo steel in sodium

    International Nuclear Information System (INIS)

    Cordwell, J.E.; Charnock, W.; Nicholson, R.D.

    1979-02-01

    The creep endurance and creep cracking behaviour of 2 1/4Cr, 1Mo steel in sodium at 475 0 C have been studied at three different sodium carbon activities. Creep endurance was found to increase with increasing carbon activity of the sodium. Tests carried out in high carbon activity sodium were discontinued before fracture. Creep crack initiation displacement at notches decreased with increasing carbon activity, presumably as a result of notch tip carburisation. The plastic zones at the tips of blunt notches in specimens exposed in high carbon activity sodium were preferentially carburised. These observations were similar to those made previously on 9Cr, 1Mo steel. One difference detected metallographically was that in a high carburising environment uniform carburisation was obtained in the 2 1/4Cr, 1Mo steel specimens whereas carburisation gradients were observed in the 9Cr, 1Mo steel. Creep crack propagation rates for given notch opening displacement rates in low and intermediate carbon activity sodium were indistinguishable. However, the strenthening that resulted from the mild carburisation of the specimen in the intermediate carbon activity sodium caused slower notch opening displacement rates and crack propagation rates than in the low carbon activity sodium, when the rates were compared at the same crack length. (author)

  7. Review of time-dependent fatigue behavior and life prediction for 2 1/4 Cr-1 Mo steel

    International Nuclear Information System (INIS)

    Booker, M.K.; Majumdar, S.

    1982-01-01

    Available data on creep-fatigue life and fracture behavior of 2 1/4 Cr-1 Mo steel are reviewed. Whereas creep-fatigue interaction is important for Type 304 stainless steel, oxidation effects appear to dominate the time-dependent fatigue behavior of 2 1/4 Cr-1 Mo steel. Four of the currently available predictive methods - the Linear Damage Rule, Frequency Separation Equation, Strain Range Partitioning Equation, and Damage Rate Equation - are evaluated for their predictive capability. Variations in the parameters for the various predictive methods with temperature, heat of material, heat treatment, and environment are investigated. Relative trends in the lives predicted by the various methods as functions of test duration, waveshape, etc., are discussed. The predictive methods will need modification in order to account for oxidation and aging effects in the 2 1/4 Cr-1 Mo steel. Future tests that will emphasize the difference between the various predictive methods are proposed

  8. Monotonic and Cyclic Behavior of DIN 34CrNiMo6 Tempered Alloy Steel

    Directory of Open Access Journals (Sweden)

    Ricardo Branco

    2016-04-01

    Full Text Available This paper aims at studying the monotonic and cyclic plastic deformation behavior of DIN 34CrNiMo6 high strength steel. Monotonic and low-cycle fatigue tests are conducted in ambient air, at room temperature, using standard 8-mm diameter specimens. The former tests are carried out under position control with constant displacement rate. The latter are performed under fully-reversed strain-controlled conditions, using the single-step test method, with strain amplitudes lying between ±0.4% and ±2.0%. After the tests, the fracture surfaces are examined by scanning electron microscopy in order to characterize the surface morphologies and identify the main failure mechanisms. Regardless of the strain amplitude, a softening behavior was observed throughout the entire life. Total strain energy density, defined as the sum of both tensile elastic and plastic strain energies, was revealed to be an adequate fatigue damage parameter for short and long lives.

  9. Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

    OpenAIRE

    Huttunen, E.; Honkanen, M.; Tsipas, Sophia Alexandra; Omar, H.; Tsipas, D.

    2012-01-01

    Degradation of materials by a combination of erosive wear and atmospheric oxidation at elevated temperatures constitutes a problem in some power generation processes, such as fluidized-bed combustion. In this work, 9Cr-1Mo steel, a common tube material in combustion chambers, is coated by a pack cementation method from an Al-containing pack in order to improve the resistance to erosion-oxidation at elevated temperatures. The resulting coating is studied in terms of microstructure and microhar...

  10. A comparison of low-chromium and high-chromium reduced-activation steels for fusion applications

    International Nuclear Information System (INIS)

    Klueh, R.L.; Maziasz, P.J.; Alexander, D.J.

    1996-01-01

    Ferritic steels have been considered candidate structural materials for first wall and blanket structures for fusion power plants since the late 1970s. The first steels considered in the United States were the conventional Cr-Mo steels Sandvik HT9 (nominally 12Cr-1Mo-0.25V-0.5W-0.5Ni-0.2C, here designated l2Cr-1MoVW), modified 9Cr-1Mo steel (9Cr-1Mo-0.2V-0.06Nb-0. IC, designated 9Cr-1MoVNb) and, to a lesser extent, 2 1/4Cr-1Mo steel (2.25Cr-Mo-0.1C). All compositions are in wt. %. The normalized-and-tempered 9 and 12Cr steels had a tempered martensite microstructure, and the normalized-and-tempered 2 1/4 Cr steel had a tempered bainite microstructure. This report describes chromium steels tested in normalized and tempered conditions. Miniature tensile and Charpy specimens were tested

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

    Energy Technology Data Exchange (ETDEWEB)

    Mabruri, Efendi, E-mail: effe004@lipi.go.id; Anwar, Moch Syaiful, E-mail: moch.syaiful.anwar@lipi.go.id; Prifiharni, Siska, E-mail: siska.prifiharni@lipi.go.id; Romijarso, Toni B.; Adjiantoro, Bintang [Research Center for Metallurgy and Materials, Indonesian Institute of Sciences (LIPI) Kawasan Puspiptek Gd. 470 Serpong, Tangerang Selatan 15314 (Indonesia)

    2016-04-19

    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.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

  13. Effect of ETA treatment on corrosion fatigue in rotors and blades and stress corrosion cracking in 3.5 NiCrMoV steel low-pressure turbine discs

    International Nuclear Information System (INIS)

    Hitomi, Itoh; Takashi, Momoo; Takayuki, Shiomi

    2001-01-01

    In recent years, to increase the reliability and reduce the amount of feed water iron to prevent of fouling of steam generator tubes, ethanolamine (ETA) treatment has been adopted into the secondary system. In this investigation, the authors verified that ethanolamine treatment does not adversely affect the susceptibility of either stress corrosion cracking (SCC) in the turbine discs that are the principal units in the secondary system or corrosion fatigue (CF) in rotors and blades. In the first stage, a laboratory investigation was made of (1) SCC initiation and propagation in 3,5 NiCrMoV steel and (2) CF in 3,5 NiCrMoV steel and blade steels, in both cases using deaerated water to which had been added ethanolamine with few organic acids that is 10 times the estimated concentration. It was confirmed that the ethanolamine treatment had almost no effect. In the second stage, test pieces (removed from the disc steel inserted into the turbine extraction chamber before the ethanolamine treatment was started) were used to observe the initiation and propagation of SCC. Even after long-term observation, ethanolamine treatment into the secondary system was found to have almost no effect on the susceptibility of SCC in discs. (author)

  14. Fatigue damage evolution of cold-worked austenitic nickel-free high-nitrogen steel X13CrMnMoN18-14-3 (1.4452)

    Energy Technology Data Exchange (ETDEWEB)

    Tikhovskiy, I.; Weiss, S.; Fischer, A. [Univ. of Duisburg-Essen, Materials Science and Engineering II, Duisburg (Germany)

    2004-07-01

    Due to the fact that the risk of Ni-allergies becomes more and more important for modern therapies, the necessity of Ni-free implant materials becomes increasingly important. Beside Co- and Ti-base alloys Ni-free high-nitrogen steels may offer an attractive alternative. The present work presents the austenitic high-nitrogen and nickel-free steel X13CrMnMoN18-14-3, (Material No.: 1.4452) after 20% cold-working. In addition this material was deformed under axial cyclic total strain controlled fatigue tests at room temperature. The development of dislocation structure due to different loading amplitudes was compared to none cyclically deformed material. The good mechanical und fatigue properties of these austenitic high-nitrogen steels as well as the better tribological, chemical and biological properties compared to CrNiMo-steels qualify these steels as a promising alternative in medical applications. (orig.)

  15. Effect of Cr, Ni, and Mo additions on the susceptibility of the 0Kh6n7m7c steel to hot cracking

    International Nuclear Information System (INIS)

    Tolstykh, L.G.; Pryakhin, A.V.; Popov, A.N.; Usynin, V.F.

    1977-01-01

    The effect of chromium, molybdenum, and nickel on the tendency of surfacing materials to form hot cracks (Vsub(kp) was studied using the mathematical statistics method. The St3 steel and 38KhN3MFA steel were used in the study. A device facilitating the hot cracking tendency test procedure was developed. It was found that, in the concentration range involved, Ni and Mo produce no effect on Vsub(kp), and Cr enhances it. A new powder wire, PP-OKh7N8M6S, capable of increasing surface material resistance by 1.5-2 times, has been developed

  16. Corrosion resistance of amorphous NiCrZr and NiCrMoZr alloys

    International Nuclear Information System (INIS)

    Naka, M.; Miyake, M.; Okamoto, I.

    1987-01-01

    One of the authors has reported that the corrosion resistance of chromium containing amorphous alloys is extremely improved by alloying phosphorus among metalloids. Two factors operate for the improvement of corrosion resistance of the amorphous alloys. First, phosphorus serves for the rapid formation of protective passive film. Second, the compositional and structural homogeneity in amorphous state also account for the formation of protective film. The latter factor has been clearly seen in the high corrosion resistance of CoCrMoZr and CoCrWZr alloys without metalloids. In order to clarify the separately two factors in the corrosion resistance of amorphous alloys, the corrosion resistance of amorphous alloys without metalloids has to be further investigated. This paper also deals with the corrosion resistance and electrochemical behavior of NiCrZr and NiCrMoZr alloys in 1N HCl, and compare them with the corrosion behavior of the crystalline alloys containing the same composition as that of the amorphous alloys

  17. Tensile properties and flow behavior analysis of modified 9Cr-1Mo steel clad tube material

    Science.gov (United States)

    Singh, Kanwarjeet; Latha, S.; Nandagopal, M.; Mathew, M. D.; Laha, K.; Jayakumar, T.

    2014-11-01

    The tensile properties and flow behavior of modified 9Cr-1Mo steel clad tube have been investigated in the framework of various constitutive equations for a wide range of temperatures (300-923 K) and strain rates (3 × 10-3 s-1, 3 × 10-4 s-1 and 3 × 10-5 s-1). The tensile flow behavior of modified 9Cr-1Mo steel clad tube was most accurately described by Voce equation. The variation of instantaneous work hardening rate (θ = dσ/dε) and σθ with stress (σ) indicated two stage behavior characterized by rapid decrease at low stresses (transient stage) followed by a gradual decrease in high stresses (Stage III). The variation of work hardening parameters and work hardening rate in terms of θ vs. σ and σθ vs. σ with temperature exhibited three distinct regimes. Rapid decrease in flow stress and work hardening parameters and rapid shift of θ vs. σ and σθ vs. σ towards low stresses with increase in temperature indicated dynamic recovery at high temperatures. Tensile properties of the material have been best predicted from Voce equation.

  18. Tensile properties of modified 9Cr-1Mo steel by shear punch testing and correlation with microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Karthik, V., E-mail: karthik@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603102 (India); Laha, K.; Parameswaran, P.; Chandravathi, K.S.; Kasiviswanathan, K.V.; Jayakumar, T.; Raj, Baldev [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603102 (India)

    2011-10-15

    Modified 9Cr-1Mo ferritic steel (P91) is subjected to a series of heat treatments consisting of soaking for 5 min at the selected temperatures in the range 973 K-1623 K (below Ac{sub 1} to above Ac{sub 4}) followed by oil quenching and tempering at 1033 K for 1 h to obtain different microstructural conditions. The tensile properties of the different microstructural conditions are evaluated from small volumes of material by shear punch test technique. A new methodology for evaluating yield strength, ultimate tensile strength and strain hardening exponent from shear punch test by using correlation equations without employing empirical constants is presented and validated. The changes in the tensile properties are related to the microstructural changes of the steel investigated by electron microscopic studies. The steel exhibits minimum strength and hardness when soaked between Ac{sub 1} and Ac{sub 3} (intercritical range) temperatures due to the replacement of original lath martensitic structure with subgrains. The finer martensitic microstructure produced in the steel after soaking at temperatures above Ac{sub 3} leads to a monotonic increase in hardness and strength with decreasing strain hardening exponent. For soaking temperatures above Ac{sub 4}, the hardness and strength of the steel increases marginally due to the formation of soft {delta} ferrite. - Highlights: > A methodology presented for computing tensile properties from shear punch test. > UTS and strain hardening estimated using extended analysis of blanking models. > The analysis methodology validated for different heat treated 9Cr-1Mo steel. > Changes in tensile properties of steel correlated with microstructures.

  19. Effect of ageing on the microstructural stability of cold-worked titanium-modified 15Cr-15Ni-2.5Mo austenitic stainless steel

    International Nuclear Information System (INIS)

    Venkadesan, S.; Bhaduri, A.K.; Rodriguez, P.; Padmanabhan, K.A.

    1992-01-01

    A titanium-modified 15Cr-15Ni-2.5Mo austenitic stainless steel conforming to ASTM A 771 (UNS S 38660), commercially called Alloy D9, is being indigenously developed for application as material for the fuel clad and the hexagonal wrapper for fuel subassemblies of the Prototype Fast Breeder Reactor. As this material would be used in the cold-worked condition and would be subjected to prolonged exposure to elevated service temperatures, the effect of ageing on the microstructural stability was studied as a function of the amount of cold work. The material was given 2.5-30% prior cold work and then aged at temperatures in the range 923 to 1173 K for times ranging from 0.25 to 1000 h. Hardness measurements made before and after ageing were correlated with the Larson-Miller parameter to determine the highest stable prior cold-work level. Optical microscopy was used to study the microstructural changes. The influence of prolonged exposure for two and three years at the operating temperatures of clad and wrapper, on the elevated temperature tensile properties of a 20% prior cold-worked Alloy D9 was also studied through accelerated ageing treatments based on the present parametric approach. (orig.)

  20. Applicability of the θ projection method to creep curves of Ni-22Cr-18Fe-9Mo alloy

    International Nuclear Information System (INIS)

    Kurata, Yuji; Utsumi, Hirokazu

    1998-01-01

    Applicability of the θ projection method has been examined for constant-load creep test results at 800 and 1000degC on Ni-22Cr-18Fe-9Mo alloy in the solution-treated and aged conditions. The results obtained are as follows: (1) Normal type creep curves obtained at 1000degC for aged Ni-22Cr-18Fe-9Mo alloy are fitted using the θ projection method with four θ parameters. Stress dependence of θ parameters can be expressed in terms of simple equations. (2) The θ projection method with four θ parameters cannot be applied to the remaining creep curves where most of the life is occupied by a tertiary creep stage. Therefore, the θ projection method consisting of only the tertiary creep component with two θ parameters was applied. The creep curves can be fitted using this method. (3) If the θ projection method with four θ or two θ parameters is applied to creep curves in accordance with creep curve shapes, creep rupture time can be predicted in terms of formulation of stress and/or temperature dependence of θ parameters. (author)

  1. Optimum alloy compositions in reduced-activation martensitic 9Cr steels for fusion reactor

    International Nuclear Information System (INIS)

    Abe, F.; Noda, T.; Okada, M.

    1992-01-01

    In order to obtain potential reduced-activation ferritic steels suitable for fusion reactor structures, the effect of alloying elements W and V on the microstructural evolution, toughness, high-temperature creep and irradiation hardening behavior was investigated for simple 9Cr-W and 9Cr-V steels. The creep strength of the 9Cr-W steels increased but their toughness decreased with increasing W concentration. The 9Cr-V steels exhibited poor creep rupture strength, far below that of a conventional 9Cr-1MoVNb steel and poor toughness after aging at 873 K. It was also found that the Δ-ferrite should be avoided, because it degraded both the roughness and high-temperature creep strength. Based on the results on the simple steels, optimized martensitic 9Cr steels were alloy-designed from a standpoint of enough thoughness and high-temperature creep strength. Two kinds of optimized 9Cr steels with low and high levels of W were obtained; 9Cr-1WVTa and 9Cr-3WVTa. These steels indeed exhibited excellent toughness and creep strength, respectively. The 9Cr-1WVTa steel exhibiting an excellent roughness was shown to be the most promising for relatively low-temperature application below 500deg C, where irradiation embrittlement is significant. The 9Cr-3WVTa steel was the most promising for high temperature application above 500deg C from the standpoint of enough high-temperature strength. (orig.)

  2. Effects of Ni and Mo on the microstructure and some other properties of Co-Cr dental alloys

    International Nuclear Information System (INIS)

    Matkovic, Tanja; Matkovic, Prosper; Malina, Jadranka

    2004-01-01

    Influences of adding Ni and Mo on the microstructure and properties of as-cast Co-Cr base alloys have been investigated in order to determine the region of their optimal characteristics for biomedical application. The alloys were produced by arc-melting technique under argon atmosphere. Using optical metallography and scanning electron micro analyser it has been established that among 10 samples of Co-Cr-Ni alloys only samples 5 and 9 with the composition Co 55 Cr 40 Ni 5 and Co 60 Cr 30 Ni 10 have appropriate dendritic solidification microstructure. This microstructure, typical for commercial dental alloys, appears and beside greater number of as-cast Co-Cr-Mo alloys. The results of hardness and corrosion resistance measurements revealed the strong influence of different alloy chemistry and of as-cast microstructure. Hardness of alloys decreases with nickel content, but increases with chromium content. Therefore all Co-Cr-Ni alloys have significantly lower hardness than Co-Cr-Mo alloys. Corrosion resistance of alloys in artificial saliva was evaluated on the base of pitting potential. Superior corrosion characteristics have the samples with typical dendritic microstructure and higher chromium content, until nickel content have not significant effect. According to this, in ternary Co-Cr-Ni phase diagram was located the small concentration region (about samples 5 and 9) in them alloy properties can satisfied the high requirements for biomedical applications. This region is considerably larger in Co-Cr-Mo phase diagram

  3. Kinetics of Cr/Mo-rich precipitates formation for 25Cr-6.9Ni-3.8Mo-0.3N super duplex stainless steel

    Science.gov (United States)

    Byun, Sang-Ho; Kang, Namhyun; Lee, Tae-Ho; Ahn, Sang-Kon; Lee, Hae Woo; Chang, Woong-Seong; Cho, Kyung-Mox

    2012-04-01

    The amount and composition of Cr-rich (σ) and Mo-rich (χ) precipitates in super duplex stainless steels was analyzed. An isothermal heat treatment was conducted at temperatures ranging from 700 °C to 1000 °C for up to 10 days. A time-temperature transformation (TTT) diagram was constructed for the mixture of σ and χ phases. The mixture of the σ and χ phases exhibited the fastest rate of formation at approximately 900 °C. Minor phases, such as Cr2N, M23C6, and M7C3, were also detected using a transmission electron microscopy (TEM). Also, a continuous cooling transformation (CCT) diagram was constructed for the mixture of σ and χ phases using the Johnson-Mehl-Avrami equation. Compared with the known CCT diagram of the σ phase, this study revealed faster kinetics with an order of magnitude difference and a new CCT diagram was also developed for a mixture of σ and χ phases. The calculated fraction of σ and χ phases obtained at a cooling speed of 0.5 °C/s was in good agreement with the experimental data.

  4. A new methodology based on ultrasonic attenuation to characterize dynamically recrystallized microstructure in a 15Cr-15Ni-2.2Mo-Ti modified austenitic stainless steel

    International Nuclear Information System (INIS)

    Mandal, S.; Kumar, A.; Sivaprasad, P.V.; Jayakumar, T.; Baldev Raj; Kumar, S.; Samajdar, I.

    2010-01-01

    In this study, a C-scan ultrasonic imaging system has been employed for imaging the microstructural variations during dynamic recrystallization (DRX) of a 15Cr-15Ni-2.2Mo-Ti modified austenitic stainless steel. Four specimens were forged at 1273 K for different strains in the range of 0.1-0.5. It has been observed that the specimen with 0.2 strain or lower did not show any variation in the amplitude of the first backwall echo. However, at and above 0.3 strain, a visible variation in the C-scan images has been observed. This variation has been attributed to the evolution of fine grains. The formation of fine grains, on the other hand, was related to DRX, as indicated by electron back scattered diffraction (EBSD). (author)

  5. Creep Strength of Dissimilar Welded Joints Using High B-9Cr Steel for Advanced USC Boiler

    Science.gov (United States)

    Tabuchi, Masaaki; Hongo, Hiromichi; Abe, Fujio

    2014-10-01

    The commercialization of a 973 K (700 °C) class pulverized coal power system, advanced ultra-supercritical (A-USC) pressure power generation, is the target of an ongoing research project initiated in Japan in 2008. In the A-USC boiler, Ni or Ni-Fe base alloys are used for high-temperature parts at 923 K to 973 K (650 °C to 700 °C), and advanced high-Cr ferritic steels are planned to be used at temperatures lower than 923 K (650 °C). In the dissimilar welds between Ni base alloys and high-Cr ferritic steels, Type IV failure in the heat-affected zone (HAZ) is a concern. Thus, the high B-9Cr steel developed at the National Institute for Materials Science, which has improved creep strength in weldments, is a candidate material for the Japanese A-USC boiler. In the present study, creep tests were conducted on the dissimilar welded joints between Ni base alloys and high B-9Cr steels. Microstructures and creep damage in the dissimilar welded joints were investigated. In the HAZ of the high B-9Cr steels, fine-grained microstructures were not formed and the grain size of the base metal was retained. Consequently, the creep rupture life of the dissimilar welded joints using high B-9Cr steel was 5 to 10 times longer than that of the conventional 9Cr steel welded joints at 923 K (650 °C).

  6. Effect of shot peening on the residual stress and mechanical behaviour of low-temperature and high-temperature annealed martensitic gear steel 18CrNiMo7-6

    DEFF Research Database (Denmark)

    Yang, R.; Zhang, X.; Mallipeddi, D.

    2017-01-01

    A martensitic gear steel (18CrNiMo7-6) was annealed at 180 degrees C for 2h and at similar to 750 degrees C for 1h to design two different starting microstructures for shot peening. One maintains the original as-transformed martensite while the other contains irregular-shaped sorbite together...... with ferrite. These two materials were shot peened using two different peening conditions. The softer sorbite + ferrite microstructure was shot peened using 0.6 mm conditioned cut steel shots at an average speed of 25 m/s in a conventional shot peening machine, while the harder tempered martensite steel...

  7. Establishment of Wear Resistant HVOF Coatings for 50CrMo4 Chromium Molybdenum Alloy Steel as an Alternative for Hard Chrome Plating

    Science.gov (United States)

    Karuppasamy, S.; Sivan, V.; Natarajan, S.; Kumaresh Babu, S. P.; Duraiselvam, M.; Dhanuskodi, R.

    2018-05-01

    High cost imported components of seamless steel tube manufacturing plants wear frequently and need replacement to ensure the quality of the product. Hard chrome plating, which is time consuming and hazardous, is conventionally used to restore the original dimension of the worn-out surface of the machine components. High Velocity Oxy-Fuel (HVOF) thermal spray coatings with NiCrBSi super alloy powder and Cr3C2 NiCr75/25 alloy powder applied on a 50CrMo4 (DIN-1.7228) chromium molybdenum alloy steel, the material of the wear prone machine component, were evaluated for use as an alternative for hard chrome plating in this present work. The coating characteristics are evaluated using abrasive wear test, sliding wear test and microscopic analysis, hardness test, etc. The study results revealed that the HVOF based NiCrBSi and Cr3C2NiCr75/25 coatings have hardness in the range of 800-900 HV0.3, sliding wear rate in the range of 50-60 µm and surface finish around 5 microns. Cr3C2 NiCr75/25 coating is observed to be a better option out of the two coatings evaluated for the selected application.

  8. Unified inelastic constitutive equations incorporating dynamic strain aging for Mod. 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Yaguchi, Masatsugu; Takahashi, Yukio

    1998-01-01

    A unified constitutive model considering dynamic strain aging effect was developed in order to describe inelastic deformation behavior of the Mod. 9Cr-1Mo steel precisely. The inelastic behavior of the steel was summarized as follows. A rate dependent deformation was observed above 500degC, and there was no rate dependency under 400degC. However, stress relaxation behavior was observed even at rate independent temperature region. Further, a stress after relaxation depended on prior loading strain rate, and it showed a higher value as the strain rate was slow. A feature of the proposed constitutive model was that an applied stress consists of three stress components: a back stress, an overstress and an aging stress which corresponds to dynamics strain aging and shows a negative strain rate dependency. The aging stress was measured by strain rate change tests, and it showed larger values as the strain rates were slow and the temperatures were low. The backstress and the overstress were measured by strain dip tests. The backstress was approximately rate independent under 400degC, however it showed rate dependency above 500degC. The overstress showed larger values as the strain rates were fast and the temperatures were high. The material constants were determined systematically based on the measured values of each internal variable. In order to evaluate the validity of the constitutive model, numerical simulations were done for various inelastic deformation behavior of Mod. 9Cr-1Mo steel. The simulations agreed with experimental results very well in all cases. (author)

  9. Effect of normalization heat treatment on creep and tensile properties of modified 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Panneer Selvi, S.; Sakthivel, T.; Parameswaran, P.; Laha, K.

    2016-01-01

    Creep and tensile properties have been investigated on modified 9Cr-1Mo steel subjected to single and double normalization heat treatments. Optical, scanning and transmission electron microscopic investigation revealed the presence of refined prior austenite grain size and fine M 23 C 6 precipitates in the double normalized steel compared to the steel subjected to single normalization heat treatment. Increased creep strain and significant reduction in creep rupture life were observed with the double normalized steel in comparison with single normalized steel. Increased tensile ductility coupled with marginal decrease in tensile strength at higher test temperature was observed with double normalized steel compared to single normalized steel. It has been attributed to the presence of refined prior austenite grain size and coarsening of Nb rich MX precipitates in double normalized steel. (author)

  10. Creep-fatigue life prediction method using Diercks equation for Cr-Mo steel

    International Nuclear Information System (INIS)

    Sonoya, Keiji; Nonaka, Isamu; Kitagawa, Masaki

    1990-01-01

    For dealing with the situation that creep-fatigue life properties of materials do not exist, a development of the simple method to predict creep-fatigue life properties is necessary. A method to predict the creep-fatigue life properties of Cr-Mo steels is proposed on the basis of D. Diercks equation which correlates the creep-fatigue lifes of SUS 304 steels under various temperatures, strain ranges, strain rates and hold times. The accuracy of the proposed method was compared with that of the existing methods. The following results were obtained. (1) Fatigue strength and creep rupture strength of Cr-Mo steel are different from those of SUS 304 steel. Therefore in order to apply Diercks equation to creep-fatigue prediction for Cr-Mo steel, the difference of fatigue strength was found to be corrected by fatigue life ratio of both steels and the difference of creep rupture strength was found to be corrected by the equivalent temperature corresponding to equal strength of both steels. (2) Creep-fatigue life can be predicted by the modified Diercks equation within a factor of 2 which is nearly as precise as the accuracy of strain range partitioning method. Required test and analysis procedure of this method are not so complicated as strain range partitioning method. (author)

  11. Susceptibility of 2 1/4 Cr-1Mo steel to liquid metal induced embrittlement by lithium-lead solutions

    International Nuclear Information System (INIS)

    Eberhard, B.A.; Edwards, G.R.

    1984-08-01

    An investigation has been conducted on the liquid metal induced embrittlement susceptibility of 2 1/4Cr-1Mo steel exposed to lithium and 1a/o lead-lithium at temperatures between 190 0 C and 525 0 C. This research was part of an ongoing effort to evaluate the compatibility of liquid lithium solutions with potential fusion reactor containment materials. Of particular interest was the microstructure present in a weld heat-affected zone, a microstructure known to be highly susceptible to corrosive attack by liquid lead-lithium solutions. Embrittlement susceptibility was determined by conducting tension tests on 2 1/4Cr-1Mo steel exposed to an inert environment as well as to a lead-lithium liquid and observing the change in tensile behavior. The 2 1/4Cr-1Mo steel was also given a base plate heat treatment to observe its embrittlement susceptibility to 1a/o lead-lithium. The base plate microstructure was severely embrittled at temperatures less than 500 0 C. Tempering the base plate was effective in restoring adequate ductility to the steel

  12. Corrosion resistance of Ni-Cr-Mo alloys. Chemical composition and metallurgical condition's effects

    International Nuclear Information System (INIS)

    Zadorozne, N.S.; Rebak, Raul B.

    2009-01-01

    Ni-Cr-Mo alloys offer an outstanding corrosion resistance in a wide variety of highly-corrosive environments. This versatility is due to the excellent performance of nickel in hot alkaline solutions and the beneficial effect of chromium and molybdenum in oxidizing and reducing conditions, respectively. Alloy C-22 (22 % Cr-13 % Mo-3% W) is a well known versatile member of this family. Due to its excellent corrosion resistance in a wide variety of environments, Alloy C-22 has been selected for the fabrication of the corrosion-resistant outer shell of the high-level nuclear waste container. The increasing demand of the industry for corrosion resistant alloys with particular properties of corrosion and mechanical resistance has led to the development of new alloys. Alloy C-22HS (Ni-21 % Cr-17 % Mo) is a new high-strength corrosion resistant material recently developed and introduced into the market. This alloy provides a corrosion resistance comparable with that of other C-type alloys, and it can also be age hardened to effectively double its yield strength. HASTELLOY HYBRID-BC1 (Ni-22 % Mo-15 % Cr) is a new development intended for filling the gap between Ni-Mo and Ni-Cr-Mo alloys. This novel alloy is able to withstand HCl and H 2 SO 4 , even in the presence of dissolved oxygen and other oxidizing species. Its resistance to chloride-induced pitting corrosion, crevice corrosion and stress corrosion cracking is also remarkable. Thermal aging of Ni-Cr-Mo alloys leads to microstructure changes depending on the temperature range and exposure time at temperature. A Long Range Ordering (LRO) reaction can occur in the range of 350 C degrees to 600 C degrees, producing an ordered Ni 2 (Cr,Mo) phase. This ordering reaction does not seem to affect the corrosion resistance and produces only a slight loss in ductility. LRO transformation is homogeneous and has proven to be useful to fabricate the age-hard enable Alloy C22-HS. Tetrahedral Close Packed (TCP) phases, like μ, σ and

  13. Effect of various heat treatments on microstructure and mechanical properties of 34CrNiMo6 steel

    International Nuclear Information System (INIS)

    Abd El-Azim, M.E.; Ghoneim, M.M.; Nasreldin, A.M.; Soliman, S.

    1997-01-01

    Three different austenitization treatments were applied to high strength 34CrNiMo6 steel: conventional austenitization (CAT), high temperature austenitization (HTA) and duplex treatment (DT). It was found that DT structure has finer prior austenite grain size (30 μm) than those of HTA (200 μm) and CAT (70 μm) structures. DT and HTA structures have coarser lath size for martensite than CAT structure. DT results in higher room temperature impact toughness than HTA and CAT structures and shifts the ductile-brittle transition to lower temperatures by 14 K and 32 K in comparison with HTA and CAT structures, respectively. However, DT structure has intermediate values of room temperature yield stress and ultimate tensile strength between those of CAT and HTA structures. When this steel was tempered at 300 and 400 C it underwent tempered martensite embrittlement associated with intergranular fracture. (orig.)

  14. Microstructure and long-term creep properties of 9–12% Cr steels

    DEFF Research Database (Denmark)

    Hald, John

    2008-01-01

    Advanced microstructure characterisation and microstructure modelling has demonstrated that long-term microstructure stability in 9–12% Cr steels under technical loading conditions is equivalent to precipitate stability. Mo and W can have a positive influence on long-term creep strength of 9–12% Cr...

  15. Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments

    International Nuclear Information System (INIS)

    Gaffard, V.

    2004-12-01

    Chromium martensitic stainless steels are under development since the 70's with the prospect of using them as structural components in thermal and nuclear power plants. The modified 9Cr1Mo-NbV steel is already used, especially in England and Japan, as a material for structural components in thermal power plants where welding is a commonly used joining technique. New generations of chromium martensitic stainless steels with improved mechanical properties for high pressure and temperature use are currently under development. However, observations of several in-service premature failures of welded components in 9Cr1Mo-NbV steel, outline a strong need for understanding the high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steels and weldments. The present study aimed at experimentally determining and then modelling the high temperature creep flow and damage behaviour of both 9Cr1Mo-NbV steels and weldments (typically in the temperature range from 450 C to 650 C). The base metal was first studied as the reference material. It was especially evidenced that tempered chromium martensitic steels exhibit a change in both creep flow and damage behaviour for long term creep exposure. As a consequence, the classically performed extrapolation of 1,000 hours creep data to 100,000 hours creep lifetime predictions might be very hazardous. Based on experimental observations, a new model, integrating and coupling multiple creep flow and damage mechanisms, was developed in the framework of the mechanics of porous media. It was then successfully used to represent creep flow and damage behaviour of the base metal from high to low stress levels even for complex multiaxial loading conditions. Although the high temperature creep properties of the base metal are quite good, the occurrence of premature failure in weldments in high temperature creep conditions largely focused the attention of the scientific community. The lower creep strength of the weld component was also

  16. Effect of χ Phase Formation on the Mechanical Properties of 25Cr-7Ni-4Mo-0.2N Super Duplex Stainless Steel

    International Nuclear Information System (INIS)

    Kang, Chang Yong; Kim, Jae Hwan

    2011-01-01

    This study was carried out to investigate the precipitation behavior of χ phase and effect of χ-phase which precipitated at the initial stage of aging on mechanical properties of 25%Cr-7%Ni-4%Mo-0.2%N super duplex stainless steel. χ-phase was precipitated mainly at the interface of ferrite / austenite phases and inside of the ferrite phase at the initial stage of aging, and it was transformed into σ-phase with an increase of aging time. The ferrite phase was decomposed into new austenite(γ 2 )phase and σ-phase by aging treatment. The hardness and tensile strength of the initial stage of aging when χ-phase was precipitated did not changed considerably, while elongation rapidly decreased. Accordingly, it is considered that χ-phase didn't affect the hardness and strength significantly, but it affected the elongation.

  17. Heat treatment for improvement in lower temperature mechanical properties of 0.40 pct C-Cr-Mo ultrahigh strength steel

    Science.gov (United States)

    Tomita, Yoshiyuki; Okabayashi, Kunio

    1983-11-01

    In the previous paper, it was reported that isothermal heat treatment of a commercial Japanese 0.40 pct C-Ni-Cr-Mo ultrahigh strength steel (AISI 4340 type) at 593 K for a short time followed by water quenching, in which a mixed structure of 25 vol pct lower bainite and 75 vol pct martensite is produced, results in the improvement of low temperature mechanical properties (287 to 123 K). The purpose of this paper is to study whether above new heat treatment will still be effective in commercial practice for improving low temperature mechanical properties of the ultrahigh strength steel when applied to a commercial Japanese 0.40 pct C-Cr-Mo ultrahigh strength steel which is economical because it lacks the expensive nickel component (AISI 4140 type). At and above 203 K this new heat treatment, as compared with the conventional 1133 K direct water quenching treatment, significantly improved the strength, tensile ductility, and notch toughness of the 0.40 pct C-Cr-Mo ultrahigh strength steel. At and above 203 K the new heat treatment also produced superior fracture ductility and notch toughness results at similar strength levels as compared to those obtained by using γ α' repetitive heat treatment for the same steel. However, the new heat treatment remarkably decreased fracture ductility and notch toughness of the 0.40 pct C-Cr-Mo ultrahigh strength steel below 203 K, and thus no significant improvement in the mechanical properties was noticeable as compared with the properties produced by the conventional 1133 K direct water quenching treatment and the γ α' repetitive heat treatment. This contrasts with the fact that the new heat treatment, as compared with the conventional 1133 K direct water quenching treatment and the γ α' repetitive heat treatment, dramatically improved the notch toughness of the 0.40 pct C-Ni-Cr-Mo ultrahigh strength steel, providing a better combination of strength and ductility throughout the 287 to 123 K temperature range. The difference

  18. Effect of Mo contents on corrosion behaviors of welded duplex stainless steel

    Science.gov (United States)

    Bae, Seong Han; Lee, Hae Woo

    2013-05-01

    The corrosion behaviour and change of the phase fraction in welded 24Cr Duplex stainless steel was investigated for different chemical composition ranges of Mo contents. Filler metal was produced by fixing the contents of Cr, Ni, N, and Mn while adjusting the Mo content to 0.5, 1.4, 2.5, 3.5 wt%. The δ-ferrite fraction was observed to increase as the content of Mo increased. A polarisation test conducted in a salt solution, indicated the pitting corrosion potential increased continuously to 3.5 wt% Mo, while the corrosion potential changed most between 0.5 and 1.41 wt% Mo. The location of the pitting corrosion in 0.5 wt% Mo steel was randomly distributed, but it occurred selectively at the grain boundary between the γ- and δ-ferrite phases in 1.4, 2.5 and 3.5 wt% Mo steel. Energy dispersive X-ray spectroscopy mapping analysis showed that areas deficient in Cr, Mo, and Ni occurred around the grain boundary of the γ- and δ-ferrite phases. Non-metallic inclusions are thought to act as initiation points for the pitting corrosion that occurs in the salt solution initially as a result of the potential difference between the matrix structure and the incoherent inclusions.

  19. Thermomechanical Model and Bursting Tests to Evaluate the Risk of Swelling and Bursting of Modified 9Cr-1Mo Steel Steam Generator Tubes during a Sodium-Water Reaction Accident

    Directory of Open Access Journals (Sweden)

    C. Bertrand

    2014-01-01

    Full Text Available The MECTUB code was developed to evaluate the risk of swelling and bursting of Steam Generator (SG tubes. This code deals with the physic of intermediate steam-water leaks into sodium which induce a Sodium-Water Reaction (SWR. It is based on a one-dimensional calculation to describe the thermomechanical behavior of tubes under a high internal pressure and a fast external overheating. The mechanical model of MECTUB is strongly correlated with the kind of the material of the SG tubes. It has been developed and validated by using experiments performed on the alloy 800. A change to tubes made of Modified 9Cr-1Mo steel requires more knowledge of Modified 9Cr-1Mo steel behavior which influences the bursting time at high temperatures (up to 1200°C. Studies have been initiated to adapt the mechanical model and to qualify it for this material. The first part of this paper focuses on the mechanical law modelling (elasticity, plasticity, and creep for Modified 9Cr-1Mo steel and on overheating thermal data. In a second part, the results of bursting tests performed on Modified 9Cr-1Mo tubes in the SQUAT facility of CEA are used to validate the mechanical model of MECTUB for the Modified 9Cr-1Mo material.

  20. Microstructure of reactive synthesis TiC/Cr18Ni8 stainless steel bonded carbides

    Institute of Scientific and Technical Information of China (English)

    Jiang Junsheng; Liu Junbo; Wang Limei

    2008-01-01

    TiC/Cr18Ni8 steel bonded carbides were synthesized by vacuum sintering with mixed powders of iron, ferrotitanium, ferrochromium, colloidal graphite and nickel as raw materials. The microstructure and microhardness of the steel bonded carbides were analyzed by scanning electron microscope (SEM),X-ray diffraction (XRD) and Rockwell hardometer. Results show that the phases of steel bonded carbides mainly consist of TiC and Fe-Cr-Ni solid solution. The synthesized TiC particles are fine. Most of them are not more than 1 μm With the increase of sintering temperature, the porosity of TiC/Cr18Ni8 steel bonded carbides decreases and the density and hardness increase, but the size of TiC panicles slightly increases. Under the same sintering conditions, the density and hardness of steel bonded carbides with C/Ti atomic ratio 0.9 are higher than those with C/Ti atomic ratio 1.0.The TiC particles with C/Ti atomic ratio 0.9 are much finer and more homogeneous.

  1. Mechanical behaviour of SFR materials: proposition of fatigue weld joint coefficient for MOD9CR-1MO

    International Nuclear Information System (INIS)

    Ancelet, O.; Matheron, Ph.

    2012-01-01

    Mod 9Cr-1Mo steel (T91) is a candidate material for steam generator of SFR (Sodium Fast Reactors). In order to validate this choice, it is necessary, firstly to verify that it is able to withstand the planned environmental and operating conditions, and secondly to check if it is covered by the existing design codes, concerning its procurement, fabrication, welding, examination methods and mechanical design rules. A large R and D program on mod9Cr-1Mo steel has been undertaken at CEA in order to characterize the behavior of this material and of its welded junctions. In this program, the role of the Laboratory for structural Integrity and Standards (LISN) is to develop high temperature defect assessment procedures under fatigue and creep loadings. In this frame, complementary studies are conducted in order to validate the existing methods (developed for the fast reactors) and to get new experimental data on Mod9Cr-1Mo steel. In particular, some new experiments are conducted on specimen with a weld joint and compared with classical experiments on base metal specimen. These results associated with finite element modeling allow to propose a weld joint coefficient at 550 degrees C for the Mod9Cr1Mo steel. (authors)

  2. The study of tribological and corrosion behavior of plasma nitrided 34CrNiMo6 steel under hot and cold wall conditions

    International Nuclear Information System (INIS)

    Maniee, A.; Mahboubi, F.; Soleimani, R.

    2014-01-01

    Highlights: • 34CrNiMo6 steel was plasma nitrided under hot and cold wall conditions. • The amount of ε phase in hot wall condition was more than that of cold wall condition. • Wear resistance of hot wall nitrided samples was more than cold wall treated ones. • Hot wall nitriding provides better corrosion behavior than cold wall nitriding. - Abstract: This paper reports on a comparative study of tribological and corrosion behavior of plasma nitrided 34CrNiMo6 low alloy steel under modern hot wall condition and conventional cold wall condition. Plasma nitriding was carried out at 500 °C and 550 °C with a 25% N 2 + 75% H 2 gas mixture for 8 h. The wall temperature of the chamber in hot wall condition was set to 400 °C. The treated specimens were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), microhardness and surface roughness techniques. The wear test was performed by pin-on-disc method. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were also used to evaluate the corrosion resistance of the samples. The results demonstrated that in both nitriding conditions, wear and corrosion resistance of the treated samples decrease with increasing temperature from 500 °C to 550 °C. Moreover, nitriding under hot wall condition at the same temperature provided slightly better tribological and corrosion behavior in comparison with cold wall condition. In consequence, the lowest friction coefficient, and highest wear and corrosion resistance were found on the sample treated under hot wall condition at 500 °C, which had the maximum surface hardness and ε-Fe 2–3 N phase

  3. Effect of cold work on decarburization of 2.25Cr-1Mo steel in high temperature sodium

    International Nuclear Information System (INIS)

    Aoki, Norichika; Yoshida, Eiichi; Wada, Yusaku.

    1994-01-01

    It is known that the mechanical properties of a 2.25Cr-1Mo steel deteriorated due to the decarburization during immersion in the melt sodium at high temperatures. In low-alloy steel as well as a 2.25Cr-1Mo steel, precipitation reactions of carbides are known to be accelerated by cold working and aging. Thus, it may be expected that cold working and aging effectively suppress the decarburization of the mechanical properties of a 2.25Cr-1Mo steel because the decarburization will be restrained owing to fixation of carbon as precipitates of the carbides. In the present article, effects of cold-working and heat treatments on the kinetics of the decarburization of a 2.25Cr-1Mo steel has been studied experimentally. The annealed, cold-rolled, and normalized and tempered specimens were immersed in the melt of sodium at 500, 600 and 700degC for 425, 437 and 432h, respectively. On the basis of the observations obtained from these specimens, the experiment was also carried out at 450, 500 and 550degC for 2270 and 5465h. The microstructures before and after the immersion were observed with optical and scanning electron microscopes. An average concentration of carbon in each specimen was analyzed by an inert gas fusion method. The carbides extracted from the specimens were identified by X-ray diffraction. At immersion temperatures of 450 and 500degC, a 10% reduction of the decarburization in thickness by cold-working is sufficiently effective for retardation of the decarburization at both 2270 and 5465h. Whereas, at 550degC, more than 30% reduction in thickness by cold-working is needed for it at 2270h but even 80% reduction in thickness by cold-working causes merely slight retardation of the decarburization at 5465h. (author)

  4. Tribological properties and surface structures of ion implanted 9Cr18Mo stainless steels

    International Nuclear Information System (INIS)

    Fengbin, Liu; Guohao, Fu; Yan, Cui; Qiguo, Sun; Min, Qu; Yi, Sun

    2013-01-01

    The polished quenched-and-tempered 9Cr18Mo steels were implanted with N ions and Ti ions respectively at a fluence of 2 × 10 17 ions/cm 2 . The mechanical properties of the samples were investigated by using nanoindenter and tribometer. The results showed that the ion implantations would improve the nanohardness and tribological property, especially N ion implantation. The surface analysis of the implanted samples was carried out by using XRD, XPS and AES. It indicated that the surface exhibits graded layers after ion implantation. For N ion implantation, the surface about 20 nm thickness is mainly composed of supersaturated interstitial N solid solution, oxynitrides, Cr x C y phase and metal nitrides. In the subsurface region, the metal nitrides dominate and the other phases disappear. For Ti ion implantation, the surface of about 20 nm thickness is mainly composed of titanium oxides and carbon amorphous phase, the interstitial solid solution of Ti in Fe is abundant in the subsurface region. The surface components and structures have significant contributions to the improved mechanical properties

  5. Impression creep behaviour of Mod. 9Cr-1Mo steel weld joints

    International Nuclear Information System (INIS)

    Ridhin Raj, V.R.; Kottda, Ravi Sankar; Kamaraj, M.; Maduraimuthu, V.M.; Vasudevan, M.

    2016-01-01

    P91 steel (9Cr-1Mo) steel is extensively used in power plants for super heater coils, headers and steam piping. The aim of the present work is to study the creep behaviour of different zones of A-TIG weld joint using impression creep technique and compare it with that of the TIG weld joint. P91 steel weld joints were made by A-TIG welding without using any filler material and multi-pass TIG welding is done using ER90S-B9 filler rods. Welds were subjected to post-weld heat treatment (PWHT). Impression creep tests were carried out at 650 °C on the base metal, weld metal and HAZ regions. Optical Microscope and TEM were used to correlate microstructures with observed creep rates. The FGHAZ showed significantly higher impression creep rate compared to that of the base metal and weld metal. Fine grain size and relatively coarser M 23 C 6 carbide particles are responsible for higher creep rate. The impression creep rate of A-TIG weld metal and coarse grain HAZ was found to be lower than that of base metal. This is attributed to the higher grain size in weld metal and coarse HAZ attributed to the higher grain size in weld metal and to the higher peak temperature observed during A-TIG welding. (author)

  6. Microstructure and annealing behavior of a modified 9Cr-1Mo steel after dynamic plastic deformation to different strains

    DEFF Research Database (Denmark)

    Zhang, Zhenbo; Mishin, Oleg; Tao, N.R.

    2015-01-01

    The microstructure, hardness and tensile properties of a modified 9Cr-1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level...... in a loss of strength with only a small gain in ductility, coarsening combined with pronounced partial recrystallization enables a combination of appreciably increased ductility and comparatively high strength....

  7. Ferritic stainless steels: corrosion resistance + economy

    International Nuclear Information System (INIS)

    Remus, A.L.

    1976-01-01

    Ferritic stainless steels provide corrosion resistance at lower cost. They include Type 409, Type 439, 18SR, 20-Mo (1.6 Mo), 18-2 (2 Mo), 26-1S, E-Brite 26-1, 29 Cr-4 Mo, and 29 Cr-4 Mo-2 Ni. Their corrosion and mechanical properties are examined. Resistance to stress-corrosion cracking is an advantage compared to austenitic types

  8. Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel Part II: Plate bending test and proposal of a simplified evaluation method

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Masanori, E-mail: ando.masanori@jaea.go.jp; Takaya, Shigeru, E-mail: takaya.shigeru@jaea.go.jp

    2016-12-15

    Highlights: • Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel is proposed. • A simplified evaluation method is also proposed for the codification. • Both proposed evaluation method was validated by the plate bending test. • For codification, the local stress and strain behavior was analyzed. - Abstract: In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for evaluating the creep-fatigue life of Mod.9Cr-1Mo steel weld joints was proposed based on finite element analysis (FEA) and a series of cyclic plate bending tests of longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and the failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. Inelastic FEA models consisting of the base metal, heat-affected zone and weld metal were employed to estimate the elastic follow-up behavior caused by the metallurgical discontinuities. The elastic follow-up factors determined by comparing the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints. The creep-fatigue life obtained using the plate bending test was compared to those estimated from the results of inelastic FEA and by a simplified evaluation method.

  9. Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel Part II: Plate bending test and proposal of a simplified evaluation method

    International Nuclear Information System (INIS)

    Ando, Masanori; Takaya, Shigeru

    2016-01-01

    Highlights: • Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel is proposed. • A simplified evaluation method is also proposed for the codification. • Both proposed evaluation method was validated by the plate bending test. • For codification, the local stress and strain behavior was analyzed. - Abstract: In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for evaluating the creep-fatigue life of Mod.9Cr-1Mo steel weld joints was proposed based on finite element analysis (FEA) and a series of cyclic plate bending tests of longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and the failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. Inelastic FEA models consisting of the base metal, heat-affected zone and weld metal were employed to estimate the elastic follow-up behavior caused by the metallurgical discontinuities. The elastic follow-up factors determined by comparing the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints. The creep-fatigue life obtained using the plate bending test was compared to those estimated from the results of inelastic FEA and by a simplified evaluation method.

  10. Reduction factors for creep strength and fatigue life of modified 9 Cr-1 Mo steel weldments

    International Nuclear Information System (INIS)

    Blass, J.J.; Battiste, R.L.; O'Connor, D.G.

    1991-01-01

    The provisions of ASME B ampersand PV Code Case N-47 currently include reduction factors for creep strength and fatigue life of weldments. To provide experimental confirmation of such factors for modified 9 Cr-1 Mo steel, tests of tubular specimens were conducted at 538 degree C (1000 degree F). Three creep-rupture specimens with longitudinal welds were tested in tension; and, of three with circumferential welds, two were tested in tension and one in torsion. In each specimen with a circumferential weld, a nonuniform axial distribution of strain was easily visible. The test results were compared to an existing empirical model of creep-rupture life. For the torsion test, the comparison was based on a definition of equivalent normal stress recently adopted in Code Case N-47. Some 27 fatigue specimens, with longitudinal, circumferential, or no welds, were tested under axial or torsional strain control. In specimens with welds, fatigue cracking initiated at fusion lines. In axial tests cracks grew in the circumferential direction, and in torsional tests cracks grew along fusion lines. The test results were compared to empirical models of fatigue life based on two definition of equivalent normal strain range. The results have provided some needed confirmation of the reduction factors for creep strength and fatigue life of modified 9 Cr-1 Mo steel weldments currently under consideration by ASME Code committees. 8 refs., 5 figs

  11. Effect of Cr and Mo on strain ageing behaviour of low carbon steel

    International Nuclear Information System (INIS)

    Pereloma, E.V.; Bata, V.; Scott, R.I.; Smith, R.M.

    2010-01-01

    This work explores the effects of Cr (0.26-0.74 wt%) and Mo (0.09-0.3 wt%) additions on the kinetics of strain ageing process in low carbon steel. The strain ageing behaviour of the steels was investigated by using tensile tests and transmission electron microscopy. The results have shown that Mo-alloyed steels undergo the same four stages of ageing as unalloyed low carbon steel, whereas Cr-alloyed steels exhibit only three stages of ageing. At the same time, the addition of Mo accelerates the ageing response, while alloying with Cr reduces the rate of strain ageing by ∼3 times in comparison with non-alloyed low carbon steel. It especially delays the offset of Stage III. This is explained by the reduction of carbon content in ferrite due to the enrichment of cementite with Cr leading to the reduction of its equilibrium solubility in ferrite.

  12. Effect of Cr and Mo on strain ageing behaviour of low carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Pereloma, E.V., E-mail: elenap@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522 (Australia); Bata, V. [Department of Materials Engineering, Monash University (Australia); Scott, R.I.; Smith, R.M. [BlueScope Steel Limited, Port Kembla (Australia)

    2010-04-25

    This work explores the effects of Cr (0.26-0.74 wt%) and Mo (0.09-0.3 wt%) additions on the kinetics of strain ageing process in low carbon steel. The strain ageing behaviour of the steels was investigated by using tensile tests and transmission electron microscopy. The results have shown that Mo-alloyed steels undergo the same four stages of ageing as unalloyed low carbon steel, whereas Cr-alloyed steels exhibit only three stages of ageing. At the same time, the addition of Mo accelerates the ageing response, while alloying with Cr reduces the rate of strain ageing by {approx}3 times in comparison with non-alloyed low carbon steel. It especially delays the offset of Stage III. This is explained by the reduction of carbon content in ferrite due to the enrichment of cementite with Cr leading to the reduction of its equilibrium solubility in ferrite.

  13. Gradient microstructure and microhardness in a nitrided 18CrNiMo7-6 gear steel

    Science.gov (United States)

    Yang, R.; Wu, G. L.; Zhang, X.; Fu, W. T.; Huang, X.

    2017-07-01

    A commercial gear steel (18CrNiMo7-6) containing a tempered martensite structure was nitrided using a pressurized gas nitriding process under a pressure of 5 atm at 530 °C for 5 hours. The mechanical properties and microstructure of the nitrided sample were characterized by Vickers hardness measurements, X-ray diffraction, and backscatter electron imaging in a scanning electron microscope. A micro-hardness gradient was identified over a distance of 500 μm with hardness values of 900 HV at the top surface and 300 HV in the core. This micro-hardness gradient corresponds to a gradient in the microstructure that changes from a nitride compound layer at the top surface (∼ 20 μm thick) to a diffusion zone with a decreasing nitrogen concentration and precipitate density with distance from the surface, finally reaching the core matrix layer with a recovered martensite structure.

  14. Interdiffusion between U-Zr-Mo and stainless steel cladding

    International Nuclear Information System (INIS)

    Hwang, J. Y.; Lee, B. S.; Lee, J. T.; Kang, Y. H.

    1998-01-01

    Interdiffusion investigations were carried out at 700 deg C for 200 hours for the diffusion couples assembled with the U-Zr-Mo ternary fuel versus austenitic stainless steel D9 and the U-Zr-Mo ternary fuel versus martensitic stainless steel HT9 respectively to investigate the fuel-cladding compatibility. SEM-EDS analysis was utilized to determine the composition and the penetration depths of the reaction layers. In the case of Fuel/D9 couple, (Fe, Cr, Ni) of the cladding elements formed the precipitates with the Zr, Mo and diminished the U concentration upto 800μ length from the fuel side. Composition of the precipitates was varied with the penetrated elements. In Fuel/HT9 couple, reaction layer was smaller than that of D9 couples and was less affected by cladding elements. The eutectic reaction appeared partially in the Fuel/HT9 diffusion couple

  15. Stress corrosion cracking in repair-welded 3.5 NiCrMoV steel in an actual turbine environment

    International Nuclear Information System (INIS)

    Hitomi, Itoh; Takashi, Shige; Takashi, Momoo

    2001-01-01

    Temporary welding repairs are sometimes needed when damage occurs at the teeth of blade grooves in a low-pressure turbine rotor operated at the dry/wet boundary region. When repair welding has been performed for the 3,5 NiCrMoV steel used in low-pressure turbines, the soundness of the weld must be confirmed. For this reason, a laboratory investigation of susceptibility for stress corrosion cracking (SCC) was conducted for test specimens taken from simulated welds, and then an exposure test was conducted in an actual turbine environment for approximately 7,000 hours. As no SCC initiation was detected and also the propagation was extremely small, repair welding is deemed to be applicable. (author)

  16. Passive behaviour of alloy corrosion-resistant steel Cr10Mo1 in simulating concrete pore solutions with different pH

    International Nuclear Information System (INIS)

    Ai, Zhiyong; Jiang, Jinyang; Sun, Wei; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

    2016-01-01

    Highlights: • A new alloy corrosion-resistant steel Cr10Mo1 is developed for reinforcing rebar of concrete in severe environments. • The effects of pH on the passive behaviour of Cr10Mo1 steel compared with plain carbon steel were studied systematically by electrochemical techniques and surface analysis. • The mechanism for self-reinforcing passivity against carbonation of the corrosion-resistant steel is revealed. - Abstract: The passive behaviour of new alloy corrosion-resistant steel Cr10Mo1 and plain carbon steel (as a comparison) in simulating concrete pore solutions of different pH (ranging from 13.5 to 9.0) under open circuit potential conditions, was evaluated by various electrochemical techniques: potentiodynamic polarization, capacitance measurements and electrochemical impedance spectroscopy. The chemical composition and structure of passive films were investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The electrochemical responses of passive films show that Cr10Mo1 steel has an increasing passivity with pH decreasing while carbon steel dose conversely, revealing carbonation does no negative effect on passivation of the corrosion-resistant steel. SIMS reveals that the passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer mainly consisting of Fe oxides and hydroxides, and an inner layer enriched in Cr species, while only a Fe-concentrated layer for carbon steel. According to the XPS analysis results, as the pH decreases, more stable and protective Cr oxides are enriched in the film on Cr10Mo1 steel while Fe oxides gradually decompose. Higher content of Cr oxides in the film layer provides Cr10Mo1 corrosion-resistant steel more excellent passivity at lower pH.

  17. Passive behaviour of alloy corrosion-resistant steel Cr10Mo1 in simulating concrete pore solutions with different pH

    Energy Technology Data Exchange (ETDEWEB)

    Ai, Zhiyong, E-mail: 230139452@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); Jiang, Jinyang, E-mail: jiangjinyang16@163.com [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); Sun, Wei, E-mail: sunwei@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); Song, Dan, E-mail: songdancharls@hhu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); College of Mechanics and Materials, Hohai University, Nanjing 210098, Jiangsu (China); Ma, Han, E-mail: mahan-iris@shasteel.cn [Research Institute of Jiangsu Shasteel Iron and Steel, Zhangjiagang 215625, Jiangsu (China); Zhang, Jianchun, E-mail: Zhangjc-iris@shasteel.cn [Research Institute of Jiangsu Shasteel Iron and Steel, Zhangjiagang 215625, Jiangsu (China); Wang, Danqian, E-mail: wonderbaba@126.com [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China)

    2016-12-15

    Highlights: • A new alloy corrosion-resistant steel Cr10Mo1 is developed for reinforcing rebar of concrete in severe environments. • The effects of pH on the passive behaviour of Cr10Mo1 steel compared with plain carbon steel were studied systematically by electrochemical techniques and surface analysis. • The mechanism for self-reinforcing passivity against carbonation of the corrosion-resistant steel is revealed. - Abstract: The passive behaviour of new alloy corrosion-resistant steel Cr10Mo1 and plain carbon steel (as a comparison) in simulating concrete pore solutions of different pH (ranging from 13.5 to 9.0) under open circuit potential conditions, was evaluated by various electrochemical techniques: potentiodynamic polarization, capacitance measurements and electrochemical impedance spectroscopy. The chemical composition and structure of passive films were investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The electrochemical responses of passive films show that Cr10Mo1 steel has an increasing passivity with pH decreasing while carbon steel dose conversely, revealing carbonation does no negative effect on passivation of the corrosion-resistant steel. SIMS reveals that the passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer mainly consisting of Fe oxides and hydroxides, and an inner layer enriched in Cr species, while only a Fe-concentrated layer for carbon steel. According to the XPS analysis results, as the pH decreases, more stable and protective Cr oxides are enriched in the film on Cr10Mo1 steel while Fe oxides gradually decompose. Higher content of Cr oxides in the film layer provides Cr10Mo1 corrosion-resistant steel more excellent passivity at lower pH.

  18. Effects of welding on toughness of Mod. 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Ryu, W. S.; Kim, S. H.; Yoon, J. H.

    2008-01-01

    Nuclear energy is being seriously considered to meet the increasing demand for a world-wide energy supply without environmental effects. Generation IV reactors are being developed to produce a reliable energy safely and with an economic benefit. Since these new reactors require an elevated temperature, ferritic/martensitic steels are attracting attention as candidate materials for the reactor vessel of a very high temperature reactor (VHTR) and the cladding of a sodium fast reactor (SFR,) due to their high strength and thermal conductivity, low thermal expansion, and good resistance to corrosion. in recent years, new ferritic/martensitic steels have been developed for ultra supercritical fossil power plants. Advanced technologies for a steel fabrication have improved the elevated temperature properties of ferritic/martensitic steels to make them comparable with austenitic stainless steels. The microstructural stability of the pressure vessel, cladding and core structural materials of the VHTR and SCWR is very important. Welding process affects the microstructure and residual stress, so the toughness of ferritic/martensitic steels decreases in general. In this paper; Mod. 9Cr-1Mo steel is welded by SMAW with V-groove, and the effects of welding on tensile and impact properties are evaluated. The upper self energy of the weldment was only 57% of that of the base metal, and the DBTT T 41J and T 68J index temperatures of the weldment were higher than those of the base metal by 17 deg. C, 38 deg. C and 37 deg. C, respectively. (authors)

  19. Microstructure Evolution and Chemical Analysis on Carbon Steels and Fe-Cr-Mo Alloys after FAC Simulation Tests

    International Nuclear Information System (INIS)

    Kim, Seunghyun; Kim, Taeho; Lee, Yun Ju; Kim, Ji Hyun

    2017-01-01

    Flow-accelerated corrosion (FAC) is an environment assisted degradation of structural materials, which usually occurs in pipelines of power plants. There have been many studies to investigate the fundamental mechanism and corresponding countermeasures against FAC, and recently the carbon steels have been replaced by ASTM A 335 P22, which contains approximately 2.2 wt.% of Cr and 1 wt.% of Mo. By enhancing passivity of P22 by Cr, it is reported that FAC rate has been greatly reduced. However, while corrosion behavior of Fe-based alloys is relatively well known, their behavior under high-temperature flowing water is not well investigated. In other words, effects of Cr and its corrosion and oxidation behavior is not clearly revealed. Furthermore, it is known that Mo enhances the pitting corrosion resistance of alloys however its mechanism is not clearly investigated. Recently, replacement of Mo in alloy contents has been widely studied because of the cost of Mo. Carbon steels undergo severe environmental-assisted degradation behavior so called FAC, and as its countermeasure the carbon steel has been replaced by P22 which contains Cr and Mo. It is generally known that Cr and Mo enhances passivity of Fe-based alloys however their corrosion and oxidation behavior has not been fully investigated especially in high-temperature flowing water environments. In this study, we employed HRTEM and synchrotron XAS techniques in order to investigate detailed microstructure evolution and chemical bonding of the commercialized carbon steel and the Fe-Cr-Mo alloys. From the analysis, it is found that while carbon steels exhibit porous oxide P22 exhibit oxide structures with thin Cr-rich oxide and spinel. Therefore, carbon steel undergoes severe FAC compared to P22 however effects of Cr and Mo and their behavior in high-temperature flowing water will be investigated.

  20. Improvements in the susceptibility to hydrogen attack and stress-relief cracking of 2 1/4Cr-1Mo steels

    International Nuclear Information System (INIS)

    Imanaka, T.; Sato, S.; Shimomura, J.; Aso, K.

    1985-01-01

    The influence of sulphur content at extremely low level on the susceptibility to hydrogen attack and stress-relief cracking in 2 1/4Cr-1Mo steels was studied. The reduction of sulphur content and/or the addition of REM (rare earth metal) or Ca in accordance with sulphur content remarkably improve the resistivity against hydrogen attack and stress-relief cracking. Micro-structural examination has showed that there exist Mn-REM-S-Al-O complex particles in the REM-added steels. It is concluded that the effect of REM on hydrogen attack and stress-relief cracking is to reduce ''the free sulphur'' in 2 1/4Cr-1Mo steels

  1. Compatibility evaluation between La 2Mo 2O 9 fast oxide-ion conductor and Ni-based materials

    Science.gov (United States)

    Corbel, Gwenaël; Lacorre, Philippe

    2006-05-01

    The chemical reactivity of La 2NiO 4+δ and nickel metal or nickel oxide with fast oxide-ion conductor La 2Mo 2O 9 is investigated in the annealing temperature range between 600 and 1000 °C, using room temperature X-ray powder diffraction. Within the La 2NiO 4+δ/La 2Mo 2O 9 system, subsequent reaction is evidenced at relatively low annealing temperature (600 °C), with formation of La 2MoO 6 and NiO. The reaction is complete at 1000 °C. At reverse, no reaction occurs between Ni or NiO and La 2Mo 2O 9 up to 1000 °C. Together with a previous work [G. Corbel, S. Mestiri, P. Lacorre, Solid State Sci. 7 (2005) 1216], the current study shows that Ni-CGO cermets might be chemically and mechanically compatible anode materials to work with LAMOX electrolytes in solid oxide fuel cells.

  2. Welding repair of the high-intermediate pressure steam casings made of Cr-Mo and Cr-Mo-V steel

    International Nuclear Information System (INIS)

    Mazur, Z.; Cristalinas, V.; Kubiak, J.

    1996-01-01

    An analysis of typical failure causes and their location at high-intermediate pressure steam turbine casing, and weldability analysis of the Cr-Mo and Cr-Mo-V steels, is carried out. basing on the steam turbine of 158 MW capacity, the internal high pressure casing failures and development of in situ repair welding technology is described. After repair, the casing was put back into service

  3. Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

    International Nuclear Information System (INIS)

    Venkatesh, L.; Samajdar, I.; Tak, Manish; Doherty, Roger D.; Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S.V.

    2015-01-01

    Highlights: • Microstructural development during laser cladding has been studied. • In this multi component system Cr 7 C 3 is found to be the stable carbide phase. • Phases were identified by EBSD since XRD results were not conclusive. • Increase in laser power and/or scanning speed reduced the carbide content. • Hardness seems to depend on phase content as well as microstructure. - Abstract: Microstructural development in laser clad layers of Chromium carbide (Cr x C y )-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr 3 C 2 and Cr 7 C 3 , the clad layers showed only the presence of Cr 7 C 3 . Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr 7 C 3 with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr 7 C 3 is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ 2 ) of the Cr 7 C 3 dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

  4. Electrochemical and metallurgical characterization of ZrCr{sub 1-x}NiMo{sub x} AB{sub 2} metal hydride alloys

    Energy Technology Data Exchange (ETDEWEB)

    Erika, Teliz [Universidad de la República, Facultad de Ciencias, Laboratorio de Electroquímica Fundamental, Núcleo Interdisciplinario Ingeniería Electroquímica, Igua 4225, CP 11400 Montevideo (Uruguay); Ricardo, Faccio [Universidad de la República, Crystallography, Solid State and Materials Laboratory (Cryssmat-Lab), DETEMA, Centro NanoMat, Polo Tecnológico de Pando, Espacio Interdisciplinario, Facultad de Química, Montevideo (Uruguay); Fabricio, Ruiz [Consejo Nacional de Investigaciones Científicas y Técnicas , CONICET, Av. Rivadavia 1917, C1033AAJ Ciudad de Buenos Aires (Argentina); Centro Atómico Bariloche , Comisión Nacional de Energía Atómica (CAB-CNEA), Av. Bustillo 9500, CP 8400 S.C. de Bariloche, RN (Argentina); Fernando, Zinola [Universidad de la República, Facultad de Ciencias, Laboratorio de Electroquímica Fundamental, Núcleo Interdisciplinario Ingeniería Electroquímica, Igua 4225, CP 11400 Montevideo (Uruguay); and others

    2015-11-15

    The effects of partial replacement of chromium by molybdenum was studied on the structure and electrochemical kinetic properties of ZrCr{sub 1-x}NiMo{sub x}(x = 0.0, 0.3 and 0.6) metal hydride alloys. The arc-melting prepared alloys were metallurgically characterized by X-ray diffraction and energy dispersive spectroscopy microanalysis, which showed AB{sub 2} (with hexagonal C14 structure) and Zr{sub x}Ni{sub y} (Zr{sub 7}Ni{sub 10}, Zr{sub 9}Ni{sub 11}) phases. After a partial substitution of chromium by molybdenum, secondary phases monotonically increase with the C14 unit cell volume indicating that most of molybdenum atoms locate in the B-site. The alloys were electrochemically characterized using charge/discharge cycling, electrochemical impedance spectroscopy and rate capability experiments that allowed the determination of hydriding reaction kinetic parameters. The presence of molybdenum produces a positive effect for hydrogen diffusion in the alloy lattice, and ZrCr{sub 0.7}NiMo{sub 0.3} alloy depicts the better kinetics associated with a fast activation, lower charge transfer resistance and the best high rate discharge behavior. This fact would be related to a lower diffusion time constant and a bigger value of the product between exchange density current and surface active area. There is a trade-off in the amounts of secondary phase and Laves phases in order to improve the kinetic performance. - Highlights: • Metallurgical characterization evidences the presence of Zr{sub x}Ni{sub y} and C14 phases. • The partial replacement of Cr by Mo promotes the segregation of Zr{sub x}Ni{sub y} phase. • The incorporation of molybdenum improves the kinetics for the hydriding process. • Mo produces a decrease in the diffusion time constant.

  5. [Studies on the tolerance of the organism to X 5 CrNiMo 18.10 steel (Königsee). II. Light microscopic studies of the surrounding tissue of metal implants (X 5 CrNiMo 18.10 steel) in guinea pigs].

    Science.gov (United States)

    Höhndorf, H; Drössler, K; Stiehl, P

    1977-06-01

    The tissue around X 5 CrNiMo 18.10-steel implantates with different surfaces was examined in 72 guinea-pigs. Aside from controls, these animals were preoperatively sensibilized against chromium and nickel. The results can be summarized since the histologic findings showed no different peculiarities. The authors describe an intussusception of the implantate in connective tissue which evidently depends on time and surface. Further the spreading of alien material in the surrounding of the implantate, and morphologic findings are reported. The morphologic evidences are described and discussed in detail, since they are interpreted as signs of cell-mediated immune reactions. The presence of lymphocytes, lymphoblasts, histiocytes (mostly carrying alien material), and granulocytes, as well as proliferations at the arterioles suggest an overlapping of immune reactions.

  6. Basic investigation for life assessment technology of modified 9CR-1Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Okamura, Hiroyuki [Science Univ. of Tokyo (Japan); Ohtani, Ryuichi [Kyoto Univ. (Japan); Fujii, Kazuya [Japan Power Engineering and Inspection Corp., Tokyo (Japan); Kimura, Kazushige; Ishii, Ryuichi; Fujiyama, Kazunari; Hongo, Shigetada; Iseki, Takashi; Uchida, Hiroshi [Toshiba Corp., Kawasaki, Kanagawa (Japan)

    1998-11-01

    For the basic study of life assessment technologies for aged components made of mod.9Cr-1Mo steel, specimens were artificially deteriorated by aging, creep and fatigue tests at elevated temperatures. And metallurgical and mechanical properties were examined. The change in the precipitates caused the decrease in toughness. The creep damage in base metal corresponded to the decrease in hardness. The fatigue damage in base metal correlated to the maximum length of a crack among micro-cracks initiated during fatigue cycle. In the welded joint, the creep fracture occurred by the formation and growth of voids in the fine grained region of HAZ near base metal. The creep damage was associated with the increase in both number and area fraction of voids. (orig.)

  7. Análisis mecánico y tribológico de los recubrimientos fe-cr-ni-c y ni-al-mo

    Directory of Open Access Journals (Sweden)

    JORGE E. MUÑOZ

    2007-01-01

    Full Text Available En este trabajo de investigación se evaluaron dos recubrimientos aplicados por medio de la técnica de rociado térmico por combustión, la aleación: Ni=89%, Al = 5,5%, Mo=5,5% y la aleación Fe=81,8%, Cr=16%, Ni=2%, C=0,2. La preparación superficial de las probetas se realizó usando chorro de arena. Se realizaron pruebas de resistencia al cortante, adherencia, desgaste abrasivo, desgaste por deslizamiento y flexión en cuatro puntos. El recubrimiento Fe-Cr-Ni-C presentó menor pérdida de masa, tanto para desgaste abrasivo como para el desgaste por deslizamiento. La multicapa presentó una mayor porosidad en el recubrimiento Ni-Al- Mo usado como capa base y la capa exterior de Fe-Cr-Ni-C presentó mayor cantidad de partículas no fundidas y óxidos. La falla ocurrida en el ensayo de adherencia para las probetas con recubrimiento multicapa fue de característica adhesiva y cohesiva. El esfuerzo en el que se presenta la fisura por flexión en el recubrimiento multicapa disminuyó con el aumento del espesor

  8. Microstructural features of dissimilar welds between 316LN austenitic stainless steel and alloy 800

    International Nuclear Information System (INIS)

    Sireesha, M.; Sundaresan, S.

    2000-01-01

    For joining type 316LN austenitic stainless steel to modified 9Cr-1Mo steel for power plant application, a trimetallic configuration using an insert piece (such as alloy 800) of intermediate thermal coefficient of expansion (CTE) has been sometimes suggested for bridging the wide gap in CTE between the two steels. Two joints are thus involved and this paper is concerned with the weld between 316LN and alloy 800. These welds were produced using three types of filler materials: austenitic stainless steels corresponding to 316,16Cr-8Ni-2Mo, and the nickel-base Inconel 182 1 . The weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy. The 316 and Inconel 182 weld metals solidified dendritically, while the 16-8-2(16%Cr-8%Ni-2%Mo) weld metal showed a predominantly cellular substructure. The Inconel weld metal contained a large number of inclusions when deposited from flux-coated electrodes, but was relatively inclusion-free under inert gas-shielded welding. Long-term elevated-temperature aging of the weld metals resulted in embrittling sigma phase precipitation in the austenitic stainless steel weld metals, but the nickel-base welds showed no visible precipitation, demonstrating their superior metallurgical stability for high-temperature service. (orig.)

  9. An analysis of a set of creep data for a 9Cr-1Mo-0.2V (P91 type) steel

    International Nuclear Information System (INIS)

    Cadek, J.; Sustek, V.; Pahutova, M.

    1997-01-01

    Recently published creep data for a 9Cr-1Mo-0.2V steel are analysed and an attempt is made to interpret them applying the concept of thermally activated detachment of dislocations from carbide particles as the rate controlling process. For the data, very high and stress dependent apparent activation energy of creep, Q c , and very high and temperature dependent apparent stress exponent, m c , are characteristic. The modelling of creep behavior applying the above mentioned concept is shown to fail to account for this temperature and applied stress dependence of minimum creep strain rate and/or the values of Q c and m c following from the data analysis. It is suggested that the behavior of the dislocation substructure, which is affected by the presence of carbide particles, must be introduced into any model to adequately describe the unusual creep behavior of the steel of interest. (orig.)

  10. High-Temperature Oxidation Behavior and Kinetics of Forged 12Cr-MoVW Steel

    Directory of Open Access Journals (Sweden)

    Kim Yong Hwan

    2017-06-01

    Full Text Available The oxidation kinetics of forged 12Cr-MoVW steel was investigated in an air (N2+O2 atmosphere at 873-1073 K (Δ50 K using thermogravimetric analysis. The oxidized samples were characterized using X-ray diffraction, and the surface and cross-sectional morphologies were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The forged 12Cr-MoVW steel samples exhibited parabolic behavior and a low oxidation rate compared with their as-cast counterparts. A protective oxide layer was uniformly formed at relatively low temperature (≤973 K for the forged samples, which thus exhibited better oxidation resistance than the as-cast ones. These oxides are considered solid-solution compounds such as (Fe, Cr2O3.

  11. Stress-relieving annealing of Cr-Mo steel for high temperature pressure vessels and the quality change in use

    International Nuclear Information System (INIS)

    Makioka, Minoru; Hirano, Hiromichi

    1976-01-01

    The securing of good mechanical properties is difficult in thick plates for large pressure vessels because cooling rate is insufficient and time is prolonged in heat treatment. Cr-Mo steel plates are usually used in the state of improved notch toughness though somewhat reduced strength by normalizing or accelerated cooling and tempering. If the time for heat treatment is prolonged, the embrittlement occurs. The effects of temperature, holding time, and cooling rate in stress-relieving treatment on the mechanical properties of 1-1/4Cr - 1/2Mo, 2-1/4Cr - 1Mo, 3Cr - 1Mo, and 5Cr - 1/2Mo steels were investigated. The tensile strength lowered almost linearly as the hollomon-Jaffe parameter of heat treatment condition increased in all the steels. The transition temperature shifted continuously to high temperature side in 1-1/4Cr - 1/2Mo steel, but the notch toughness was improved up to certain values and then the tendency turning to brittleness was shown in the other steels, as the H-J parameter increased. When the holding time became longer, the transition temperature shifted to higher temperature side, but the cooling rate showed no effect. The condition for stress relieving treatment must be selected so that the ferrite bands observed in welded metal do not arise. The embrittlement at the operation temperature of 400 - 450 0 C for a long time is evaluated by the comparison with that by stepped cooling method. (Kako, I.)

  12. Impact of saline aquifer water on surface and shallow pit corrosion of martensitic stainless steels during exposure to CO2 environment (CCS)

    Science.gov (United States)

    Pfennig, Anja; Kranzmann, Axel

    2018-05-01

    Pipe steels suitable for carbon capture and storage technology (CCS) require resistance against the corrosive environment of a potential CCS-site, e.g. heat, pressure, salinity of the aquifer, CO2-partial pressure. Samples of different mild and high alloyed stainless injection-pipe steels partially heat treated: 42CrMo4, X20Cr13, X46Cr13, X35CrMo4 as well as X5CrNiCuNb16-4 were kept at T=60 °C and ambient pressure as well as p=100 bar for 700 h - 8000 h in a CO2-saturated synthetic aquifer environment similar to possible geological on-shore CCS-sites in the northern German Basin. Main corrosion products are FeCO3 and FeOOH. Corrosion rates obtained at 100 bar are generally much lower than those measured at ambient pressure. Highest surface corrosion rates are 0.8 mm/year for 42CrMo4 and lowest 0.01 mm/year for X5CrNiCuNb16-4 in the vapour phase at ambient pressure. At 100 bar the highest corrosion rates are 0.01 mm/year for 42CrMo4, X20Cr13 (liquid phase), X46Cr13 and less than 0.01 mm/year for X35CrMo4 and X5CrNiCuNb16-4 after 8000 h of exposure with no regard to atmosphere. Martensitic microstructure offers good corrosion resistance.

  13. Ion backscattering, channeling and nuclear reaction analysis study of passive films formed on FeCrNi and FeCrNiMo (100) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, C; Schmaus, D [Paris-7 Univ., 75 (France). Groupe de Physique des Solides de l' ENS; Elbiache, A; Marcus, P [Ecole Nationale Superieure de Chimie, 75 - Paris (France)

    1990-01-01

    The compositions of passive films formed on Fe-17Fr-13Ni (at. %) and Fe-18.5Cr-14Ni-1.5Mo (100) single crystals have been determined and the structure of the alloy under the film has been investigated. The alloys were passivated in 0.05M H{sub 2}SO{sub 4} at 250 mV/SHE for 30 min. The oxygen content was measured by nuclear microanalysis using the {sup 16}O(d,p) {sup 17}O* reaction. The oxygen content in the passive film is similar for the two alloys and equal to (12{plus minus}2) 10{sup 15} O/cm{sup 2}. The cationic compositions of the passive films have been determined by {sup 4}He channeling at two incident beam energies: 0.8 and 2.0 MeV. For the two alloys studied, a total cation content of (5{plus minus}2)10{sup 15} at/cm{sup 2} is found in the passive films. The corresponding thickness is about 12 A. There is an excess of oxygen, which can be attributed to the presence of hydroxyls and sulfate. A strong chromium enrichment is found in the passive film formed on both alloys: chromium represents about 50% of the cations. There is no evidence of molybdenum enrichment in the passive film formed on the Mo-alloyed stainless steel. The comparison of the results obtained at the two different incident beam energies (0.8MeV and 2MeV) reveals the existence of defects at the alloy/passive film interface. (author).

  14. Density of liquid NiCrAlMo quarternary alloys measured by a modified sessile drop method

    International Nuclear Information System (INIS)

    Fang, L.; Wang, Y.F.; Xiao, F.; Tao, Z.N.; MuKai, K.

    2006-01-01

    The densities of liquid NiCrAlMo quaternary alloys with a fixed molar ratio of Ni:Cr:Al (approximately as 73:14:13) and molybdenum concentration from 0 to 10 mass% were measured by a modified sessile drop method (MSDM). It was found that the density of the liquid NiCrAlMo quaternary alloys decreases with increasing temperature, but increases with the increase of molybdenum concentration. The molar volume of liquid NiCrAlMo quaternary alloys increases with the increase of temperature and molybdenum concentration. The density of liquid NiCrAlMo quaternary alloys calculated from the partial molar volumes of nickel, chromium, aluminum and molybdenum in the corresponding Ni-based binary alloys are in good agreement with the experimental results, means, within the error tolerance range the density of liquid Ni-based multi-component alloys can be predicted from the partial volumes of elements in Ni-based binary alloys in liquid state

  15. Structure and delayed failure behaviour of 0.25C-Ni-Cr-Mo-V steel

    International Nuclear Information System (INIS)

    Kang, C.H.; Maeng, S.C.

    1980-01-01

    Delayed failure behaviour of the different transformation structures of 0.25C-2.5Ni-2.5Cr-0.5Mo-0.1V low alloy steel has been studied. The studied microstructures are martensite, lower bainite, and mixed structure of 50% martensite and 50% lower bainite. All these structures have been tempered at 450 deg C for 40 min to have the same tensile strength level of 143 kg/mm 2 . Delayed failure testing has been carried out with cantilever bend tester, in distilled water at 25 deg C. By comparing K 1 sub(scc) values, lower bainitic structure has shown the highest value, although it is only slightly higher than that of the martensitic structure. Mixed structure has the lowest resistance to delayed failure. The fracture modes of both martensitic and mixed structures have been observed as intergranular. In the martensitic structure, however, it is noticeable that there is a larger amount of ductile tearing between intergranular facets. The fracture mode of lower bainitic structure is the mixed topography of microplastic tearing and microvoid coalescence. The above experimental results are discussed in terms of Oriani's decohesion theory of hydrogen embrittlement. The lowest resistance of the mixed structure to delayed failure may be due to the enhanced decohesion by hydrogen at the phase boundaries of martensite and lower bainite. (author)

  16. Boron-bearing Influences of 9Cr-0.5Mo-2W-V-Nb Ferritic/Martensitic Steels for a SFR Fuel Cladding

    International Nuclear Information System (INIS)

    Baek, Jong-Hyuk; Han, Chang-Hee; Kim, Woo-Gon; Kim, Sung-Ho; Lee, Chan-Bock

    2008-01-01

    modification, the influences of B-bearing 9Cr-0.5Mo-2W-V-Nb ferritic/ martensitic steels on the microstructural and mechanical properties were systematically investigated in order to evaluate the applicable validity as a cladding material for the Gen-IV SFR fuel

  17. Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesh, L., E-mail: venkatesh@arci.res.in [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005 (India); Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Samajdar, I. [Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Tak, Manish [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005 (India); Doherty, Roger D. [Department of Materials Engineering, Drexel University, Philadelphia, PA 19104 (United States); Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S.V. [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005 (India)

    2015-12-01

    Highlights: • Microstructural development during laser cladding has been studied. • In this multi component system Cr{sub 7}C{sub 3} is found to be the stable carbide phase. • Phases were identified by EBSD since XRD results were not conclusive. • Increase in laser power and/or scanning speed reduced the carbide content. • Hardness seems to depend on phase content as well as microstructure. - Abstract: Microstructural development in laser clad layers of Chromium carbide (Cr{sub x}C{sub y})-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr{sub 3}C{sub 2} and Cr{sub 7}C{sub 3}, the clad layers showed only the presence of Cr{sub 7}C{sub 3}. Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr{sub 7}C{sub 3} with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr{sub 7}C{sub 3} is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ{sub 2}) of the Cr{sub 7}C{sub 3} dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

  18. Effect of Activated Flux on the Microstructure, Mechanical Properties, and Residual Stresses of Modified 9Cr-1Mo Steel Weld Joints

    Science.gov (United States)

    Maduraimuthu, V.; Vasudevan, M.; Muthupandi, V.; Bhaduri, A. K.; Jayakumar, T.

    2012-02-01

    A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials. The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint.

  19. Fundamental modelling of particle strengthened 9-12% Cr steels

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, Hans; Sandstroem, Rolf [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering; Royal Inst. of Tech., Stockholm (Sweden). Brinell Centre

    2010-07-01

    Creep strength of particle strengthened 9-12% Cr steels can be predicted by fundamental modelling. The creep strength is evaluated from the state of the microstructure during creep. Particle hardening at high temperatures can be predicted by taking dislocation climb across particles into account. Work hardening is calculated from immobile dislocations in subgrain interiors and at boundaries using the composite theory. Subgrain coarsening will lower the influence of the mechanically hard boundaries. Recovery in dislocation density is predicted through static recovery by climb and dynamic recovery by locking and dipole formation. Solid solution hardening is needed in order to explain the difference in creep strength between different 9-12% Cr steels. The accumulation of large atoms such as Mo and W will slow down the dislocation climb velocity, and thereby the microstructure recovery rate. 100000h rupture strength is predicted for X20, P91, P92 steels without any use of fitting parameters. The creep strength of P91 steel with different microstructure due to Al additions. Z-phase transformation and heat affected material is presented. (orig.)

  20. Multiaxial creep of fine grained 0.5Cr-0.5Mo-0.25V and coarse grained 1Cr-0.5Mo steels

    International Nuclear Information System (INIS)

    Browne, R.J.; Flewitt, P.E.J.; Lonsdale, D.

    1991-01-01

    To explore the multiaxial creep response of materials used for electrical power generating plant, two steels, a fine grained 0.5Cr-0.5Mo-0.25V steel in a normalised and tempered condition with high creep ductility and a coarse grained 1Cr-0.5Mo steel in a quenched and tempered condition with low uniaxial creep ductility, have been selected. A range of multiaxial stress testing techniques which span the stress states that would allow identification of any technique dependent variables has been used. The deformation and failure of the normalised and tempered 0.5Cr-0.5Mo-0.25V steel for a range of multiaxial test techniques and, therefore, stress states may be described by an equivalent stress criterion. The results from the multiaxial tests carried out on the fully bainitic 1Cr-0.5Mo steel show that the multiaxial stress rupture criterion (MSRC) varies with stress state; at high triaxiality (notch), it is controlled by the maximum principal stress, whereas at low triaxiality (shear) it is dependent on both maximum principal stress and equivalent stress. Furthermore, a simple description of stress state based on maximum principal and equivalent stress does not define this uniquely, since the MSRC derived from uniaxial and torsion testing does not describe the failure of notch, tube, or double shear tests. (author)

  1. Modified 9Cr-1Mo steel for advanced steam generator applications

    International Nuclear Information System (INIS)

    Brinkman, C.R.; Alexander, D.J.; Maziasa, P.J.

    1990-01-01

    Results are reported from several types of mechanical property tests conducted on a number of commercial heats of modified 9Cr-1Mo steel. Data from long term creep-rupture tests conducted on base and weldment material were compared with an analytical model which has been shown to give good agreement between measured and predicted values. Weldment material had somewhat inferior creep-rupture strength in comparison to base material due to a soft zone at the edge of the HAZ. Data are presented from elevated temperature tensile and creep-rupture tests conducted on material thermally aged for periods of up to 75,000 h (8.6 years). Some reduction in strength was shown to occur in comparison to unaged material. Models were developed for predicting the reduction in short term elevated temperature tensile and yield strength for material thermally aged in the temperature range of 482 to 704 degrees C. Results from Charpy impact tests conducted on material thermally aged at 538 degrees C for periods of up to 75,000 h show an increase in the ductile-brittle transition temperature

  2. Comparative Effect of Mo and Cr on Microstructure and Mechanical Properties in NbV-Microalloyed Bainitic Steels

    Directory of Open Access Journals (Sweden)

    Andrii Kostryzhev

    2018-02-01

    Full Text Available Steel product markets require the rolled stock with further increasing mechanical properties and simultaneously decreasing price. The steel cost can be reduced via decreasing the microalloying elements contents, although this decrease may undermine the mechanical properties. Multi-element microalloying with minor additions is the route to optimise steel composition and keep the properties high. However, this requires deep understanding of mutual effects of elements on each other’s performance with respect to the development of microstructure and mechanical properties. This knowledge is insufficient at the moment. In the present work we investigate the microstructure and mechanical properties of bainitic steels microalloyed with Cr, Mo, Nb and V. Comparison of 0.2 wt. % Mo and Cr additions has shown a more pronounced effect of Mo on precipitation than on phase balance. Superior strength of the MoNbV-steel originated from the strong solid solution strengthening effect. Superior ductility of the CrNbV-steel corresponded to the more pronounced precipitation in this steel. Nature of these mechanisms is discussed.

  3. Corrosive sliding wear behavior of laser clad Mo2Ni3Si/NiSi intermetallic coating

    International Nuclear Information System (INIS)

    Lu, X.D.; Wang, H.M.

    2005-01-01

    Many ternary metal silicides such as W 2 Ni 3 Si, Ti 2 Ni 3 Si and Mo 2 Ni 3 Si with the topologically closed-packed (TCP) hP12 MgZn 2 type Laves phase crystal structure are expected to have outstanding wear and corrosion resistance due to their inherent high hardness and sluggish temperature dependence and strong atomic bonds. In this paper, Mo 2 Ni 3 Si/NiSi intermetallic coating was fabricated on substrate of an austenitic stainless steel AISI321 by laser cladding using Ni-Mo-Si elemental alloy powders. Microstructure of the coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Wear resistance of the coating is evaluated under corrosive sliding wear test condition. Influence of corrosion solutions on the wear resistance of the coating was studied and the wear mechanism was discussed based on observations of worn surface morphology. Results showed that the laser clad Mo 2 Ni 3 Si/NiSi composite coating have a fine microstructure of Mo 2 Ni 3 Si primary dendrites and the interdendritic Mo 2 Ni 3 Si/NiSi eutectics. The coating has excellent corrosive wear resistance compared with austenitic stainless steel AISI321 under acid, alkaline and saline corrosive environments

  4. Corrosion resistance of stainless steels and high Ni-Cr alloys to acid fluoride wastes

    International Nuclear Information System (INIS)

    Smith, H.D.; Mackey, D.B.; Pool, K.H.; Schwenk, E.B.

    1992-04-01

    TRUEX processing of Hanford Site waste will utilize potentially corrosive acid fluoride processing solutions. Appropriate construction materials for such a processing facility need to be identified. Toward this objective, candidate stainless steels and high Ni-Cr alloys have been corrosion tested in simulated acid fluoride process solutions at 333K. The high Ni-Cr alloys exhibited corrosion rates as low as 0.14 mm/y in a solution with an HF activity of about 1.2 M, much lower than the 19 to 94 mm/y observed for austenitic stainless steels. At a lower HF activity (about 0.008 M), stainless steels display delayed passivation while high Ni-Cr alloys display essentially no reaction

  5. Developing of complex for hot plastic deformation modeling of steel type 20-30CrNiMoV for heavy forging

    Directory of Open Access Journals (Sweden)

    Dub Vladimir

    2017-01-01

    Full Text Available Production of heavy forging of bars weighing more then 235 tons for such products as rotors made of steel type 20-30CrNiMoV is a critical independent work, failure to perform which entails high costs related to repeated production (in case of defective product and untimely launch of production plants. One of the frequent causes of a defective product is the impossibility of ultrasonic testing in the barrel-gate zones on the rotor workpiece, which is due to the microstructure of the metal, namely the grain size. Determing the stages of deformation process wich causes such defects in structure is the main goal of this work.

  6. Resistencia a la corrosión a alta temperatura de recubrimientos NiCrAlY y NiCrFeNbMoTiAl depositados por APS

    Directory of Open Access Journals (Sweden)

    José Luis Tristancho-Reyes

    2014-12-01

    Full Text Available La corrosión a alta temperatura de las tuberías utilizadas en equipos generadores de vapor (calderas ha sido reconocida como un grave problema que trae consigo el adelgazamiento de éstas y, por consiguiente, la falla de los equipos. En la última década se han incrementado las investigaciones que involucran recubrimientos protectores que ayudan de alguna manera a prolongar la vida útil de estos equipos. Esta investigación determinó el comportamiento de los recubrimientos NiCrAlY y NiCrFeNbMoTiAl depositados por proyección térmica asistida por plasma (APS sobre la aleación SA213 – T22 (2¼Cr – 1Mo, en un ambiente corrosivo de 80%V2O5–20%K2SO4 a 800°C. Los valores de la cinética de corrosión fueron determinados mediante resistencia a la polarización lineal (RPL y espectroscopia de impedancia electroquímica (EIE. Los resultados obtenidos muestran una menor cinética de corrosión en el recubrimiento NiCrFeNbMoTiAl que la presentada por el recubrimiento NiCrAlY, corroborado por Microscopia Electrónica de Barrido (MEB.

  7. Elevated-temperature tensile properties of 2 1/4 Cr-1 Mo steel irradiated in the EBR-II, AD-2 experiment

    International Nuclear Information System (INIS)

    Klueh, R.L.; Vitek, J.M.

    1984-01-01

    The effect of irradiated on the tensile properties of 2 1/4 Cr-1 Mo steel was determined for specimens irradiation in EBR-II at 390 to 550 0 C. Unirradiated control specimens and specimens aged for 5000 h at the irradiation temperatures were also tested. Irradiation to approximately 9 dpa at 390 0 C increased the strength and decreased the ductility compared with the unirradiated and aged specimens. Softening occurred in samples irradiated and tested at 450, 500, and 550 0 C

  8. The causes of relaxation- and hot cracking in the heat-affected zone of 22 NiMoCr 37 and 20 MnMoNi 55

    International Nuclear Information System (INIS)

    Schellhammer, W.

    1977-01-01

    Non-destructive and metallographic investigations with a view to relaxation cracking and hot cracking were carried out in 53 component-specific welds with wall thicknesses of 40 to 360 mm and 21 experimental welds with wall thicknesses of 140 to 275 mm of high-temperature, fine-grained structural steel 22 NiMoCr 37 as well as in 27 component-specific welds of high-strength, fine-grained structural steel 20 MnMoNi 55. Non-destructive tests and conventional metallographic analyses by means of transverse structure micrography were unable to give a sufficiently accurate picture of the two types of cracks in the micro- and millimeter range, a 'volumetric' method was employed (tangential structure micrography with stepwise abrasion) which permitted semi-automatic and fast evaluation. The experimental results showed the selective influence of several elements and led to the development of a method to evaluate the cumulative effect of the chemical elements on relaxation cracking and hot cracking by addition of the selective influence. The method gives quantitative data on material optimisation with regard to the reduction of brittle and crack-prone states and confirms the findings of welding simulation tests. (orig./IHOE) 891 IHOE/orig.- 892 HIS [de

  9. Evaluation of environmental effect on creep-fatigue of 2 1/4Cr-1Mo steel

    International Nuclear Information System (INIS)

    Yang Beinan; Ishikawa, Akiyoshi; Asada, Yasuhide.

    1991-01-01

    In the present study, a trial evaluation was made to evaluate the environmental effect of air separately from the behavior of material origin. Data with 2 1/4Cr-1Mo steel at 550degC in air were subjected to the evaluation based on data of the steel in high vacuum with a newly developed procedure using the overstress concept. An empirical expression was proposed to describe the environmental effect of air on the creep-fatigue behavior. Following conclusions were obtained in the present study on a separation of the environmental effect of air on a creep-fatigue behavior of 2 1/4Cr-1Mo steel at 550degC. 1) The environmental effect of air reduces a fatigue life, that is, it increases the time-independent damage component of the creep-fatigue. 2) The environmental effect of air brings on the frequency effect which is mainly dependent upon a strain rate or time in a compression going stroke. Other environmental effect on F-S or compression hold-time cycles depends upon the strain rate in compression. 3) The rate-time dependent damage component, that is, the creep damage is reduced by the environmental effect of air. That means a creep-fatigue life recovers in air environment. (author)

  10. Influência do teor de Mo na microestrutura de ligas Fe-9Cr-xMo Effect of the content of molybdenum in the microstructure of Fe-9Cr-xMo alloy

    Directory of Open Access Journals (Sweden)

    Rodrigo Freitas Guimarães

    2010-12-01

    Full Text Available Aços Cr-Mo são usados na indústria do petróleo em aplicações com óleos crus ricos em compostos sulfurosos. Aços comerciais como 2.5Cr1Mo ou 9Cr1Mo têm se mostrado ineficientes em consequência de altos índices de corrosão naftênica. Uma estratégia para resolver este problema é o aumento do teor de molibdênio destes aços. Neste trabalho foi estudado o efeito do aumento do teor de molibdênio na microestrutura de ligas Fe-9Cr-xMo, solubilizadas e soldadas. Foram levantados os diagramas de fases com auxílio de um programa comercial para verificar as possíveis fases a serem formadas e identificar os problemas de soldagem. A microestrutura das ligas solubilizadas foi analisada por microscopia óptica e EBSD, além da medição da dureza. Foram realizadas soldagens autógenas para verificar o efeito do aporte térmico na microestrutura e na dureza das ligas. O aumento do teor de molibdênio resultou no aumento da dureza das ligas. A análise microestrutural das ligas soldadas apresentou uma particularidade para a liga com menor teor de molibdênio, a presença de martensita. Já as ligas com maior teor de molibdênio apresentaram uma microestrutura completamente ferrítica. A formação de martensita pode ser um problema na solda da liga com menor teor de molibdênio, uma vez que a mesma pode causar perdas nas propriedades mecânicas comprometendo sua aplicação.Cr-Mo steels are used in the petroleum industry in applications with crude oils rich in sulfur compounds. 2.5Cr1Mo or 9Cr1Mo do not resist to operating conditions when in contact with crude oils. The increasing of molybdenum content can improve the corrosion resistance of these alloys. This paper studied the effect of increased concentration of molybdenum in the microstructure of Fe-9Cr-xMo alloys, annealed and welded. Phase diagrams were built with the aid of commercial program to check the possible phases to be formed and to identify the problems of welding. Analyses were

  11. Effect of Tempering Temperature on the Microstructure and Properties of Fe-2Cr-Mo-0.12C Pressure Vessel Steel

    Science.gov (United States)

    Wang, Qi-wen; Li, Chang-sheng; Peng, Huan; Chen, Jie; Zhang, Jian

    2018-03-01

    To obtain the high-temperature strength and toughness of the medium-high-temperature-pressure steel, the microstructure evolution and mechanical properties of Fe-2Cr-Mo-0.12C steel subjected to three different tempering temperatures after being normalized were investigated. The results show that the microstructure of the sample, tempered in the range 675-725 °C for 50 min, did not change dramatically, yet the martensite/austenite constituents decomposed, and the bainite lath merged together and transformed into polygonal ferrite. At the same time, the precipitate size increased with an increase in tempering temperature. With the increase in the tempering temperature from 675 to 725 °C, the impact absorbed energy of the Fe-2Cr-Mo-0.12C steel at -40 °C increased from 257 to 325 J, and the high-temperature yield strength decreased; however, the high-temperature ultimate tensile strength tempered at 700 °C was outstanding (422-571 MPa) at different tested temperatures. The variations of the properties were attributed to the decomposition of M/A constituents and the coarsening of the precipitates. Fe-2Cr-Mo-0.12C steel normalized at 930 °C and tempered at 700 °C was found to have the best combination of ductility and strength.

  12. Effect of Si and Mn additions on ferrite and austenite phase fractions in 25Cr-7Ni-1.5Mo-3W base super duplex stainless steels

    International Nuclear Information System (INIS)

    Jeong, S.W.; Lee, Z.-H.; Lee, H.M.

    2000-01-01

    The effect of heat treatment and Si and Mn additions on the ferrite and austenite phase fractions of the super duplex stainless steel (SDSS), Fe-25Cr-7Ni-1.5Mo-3W-Si-Mn-0.25N (numbers are all in wt.% unless specified otherwise), was investigated. The thermodynamic calculations of phase equilibria and phase fractions were performed using the Thermo-Calc program. Based on the calculated results, specific compositions of Si and Mn were selected and alloys with these compositions were analysed by Feritscope, X-ray diffractometry and scanning electron microscopy. The calculated phase fractions and experimentally analysed ones were compared and there was a good agreement between calculations and measurements. The optimum heat treatment condition for Fe-25Cr-7Ni-1.5Mo-3W-0.5Si-0.5Mn-0.25N is to hold at 1050 to 1100 C for 2 h in considering the ferrite to austenite ratio of 50:50 and to avoid second phase precipitation such as the σ phase. It was suggested that an excessive addition of more than 0.8Si and 1.0Mn may induce the σ phase precipitation. (orig.)

  13. 3D Modelling of Flash Formation in Linear Friction Welded 30CrNiMo8 Steel Chain

    Directory of Open Access Journals (Sweden)

    Pedro Effertz

    2017-10-01

    Full Text Available Linear friction welding (LFW is a solid-state welding process that has been thoroughly investigated for chain welding in recent years in order to replace the currently in use Flash Butt Welding (FBW process. Modelling has proven to be an indispensable tool in LFW, thus providing necessary insight to the process, regardless of its final application. This article describes a 3D model developed in the commercial software DEFORM to study the LFW process of 30CrNiMo8 high strength steel in the Hero chain. Hence, a weakly coupled thermal and mechanical model were used, by means of the process experimental input such as displacement histories. The flash morphology and intervening mechanisms were analyzed. A thermal evaluation of different regions in the studied geometry was considered, and a correlation of the modeled and experimental width of the extrusion zone was established.

  14. Thermodynamic investigation on the formation of inclusions containing MgAl2O4 spinel during 16Cr-14Ni austenitic stainless steel manufacturing processes

    International Nuclear Information System (INIS)

    Park, J.H.

    2008-01-01

    The formation mechanism of the inclusions containing the spinel crystals has been developed based on the experimental results for the equilibrium between the Fe-16%Cr-14%Ni stainless steel melts and the inclusions as well as the compositions of the inclusions in the plant samples. In the laboratory experiments, the molar content of alumina in the inclusions linearly increases with increasing content of aluminum according to the theoretical expectation and the composition of the inclusions could be described as a function of the activity of aluminum and silicon. From the analysis of the plant samples, the content of MgO and Al 2 O 3 in the calcium silicate type inclusions continuously increases as the steel melts transfer from AOD converter to LT processes and thus, the spinel phase could be crystallized and grown in the calcium silicate matrix during cooling through tundish to cast slabs. On the other hand, the manganese silicate type inclusions were observed after tapping molten steel to the ladle, and then the MnO and Cr 2 O 3 (and SiO 2 ) in the inclusions were reduced by silicon and aluminum through LT to CC mold. The fraction of the inclusions containing spinel crystals at cast slabs was null at (Al 2 O 3 ) 2 O 3 ) > 20 mass%

  15. Excellent corrosion resistance of 18Cr-20Ni-5Si steel in liquid Pb-Bi

    International Nuclear Information System (INIS)

    Kurata, Y.; Futakawa, M.

    2004-01-01

    The corrosion properties of three austenitic steels with different Si contents were studied under oxygen-saturated liquid Pb-Bi condition for 3000 h. The three austenitic steels did not exhibit appreciable dissolution of Ni and Cr at 450 deg. C. At 550 deg. C, the thick ferrite layer produced by dissolution of Ni and Cr was found in JPCA and 316SS with low Si contents while the protective oxide film composed of Si and O was formed on 18Cr-20Ni-5Si steel and prevented dissolution of Ni and Cr

  16. Boron Steel: An Alternative for Costlier Nickel and Molybdenum Alloyed Steel for Transmission Gears

    Directory of Open Access Journals (Sweden)

    A. Verma

    2010-06-01

    Full Text Available Case Carburized (CC low carbon steels containing Ni, Cr and Mo alloying elements are widely used for transmission gears in automobile, as it possesses desired mechanical properties. In order to cut cost and save scarce materials like Ni and Mo for strategic applications, steel alloyed with Boron has been developed, which gives properties comparable to Ni-Cr-Mo alloyed steel. In the process of steel development, care was taken to ensure precipitation of boron which results in precipitation hardening. The characterization of the developed boron steel had exhibited properties comparable to Ni-Cr-Mo alloyed steel and superior to conventional boron steel.

  17. Characterizing microstructural changes in ferritic steels by positron annihilation spectroscopy: Studies on modified 9Cr-1Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Hari Babu, S., E-mail: shb@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Rajkumar, K.V. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Hussain, S. [UGC-DAE CSR, Kokilamedu 603 104, TN (India); Amarendra, G.; Sundar, C.S. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Positron lifetime technique probing microstructure of ferritic/martensitic steels. Black-Right-Pointing-Pointer Correlation between positron lifetime, ultrasonic and hardness. Black-Right-Pointing-Pointer Complementary nature of positron annihilation spectroscopy in probing defects. Black-Right-Pointing-Pointer Distinguishing precipitation stages by positron annihilation spectroscopy. - Abstract: Applicability of positron annihilation spectroscopy in probing the microstructural changes in ferritic steels has been investigated with thermal treatment studies on modified 9Cr-1Mo steel, during 300-1273 K. Positron lifetime results are compared with those of ultrasonic velocity and hardness techniques with two initial microstructural conditions i.e., normalized and tempered condition as well as only normalized condition. In first case, positron lifetime is found to be sensitive to small changes in metal carbide precipitation which could not be probed by other two techniques. In later case, positron lifetime is found to be sensitive to defect annealing until 673 K and in distinguishing the growth and coarsening of metal carbide precipitation stages during 773-1073 K. The present study suggests that by combining positron lifetime, ultrasonic velocity and hardness measurements, it is possible to distinguish distinct microstructures occurring at different stages.

  18. The Structure and Mechanical Properties of Ni-Mo PM Steels with Addition of Mn And Cu

    Science.gov (United States)

    Lichańska, E.; Kulecki, P.; Pańcikiewicz, K.

    2017-12-01

    The aim of the study was to evaluate the effect of chemical composition on the structure and mechanical properties of Mn-Ni-Mo and Ni-Mo-Cu PM steels. Pre-alloyed powder Astaloy 85Mo, diffusion alloyed powders Distaloy AQ and Distaloy AB produced by Höganäs, low carbon ferromanganese, carbonyl nickel powder T255 with three-dimensional filamentary structure and graphite CU-F have been used as the basic powders. Three mixtures with compositions of Fe-1%Mn-(0.5/1.75)%Ni-(0.5/0.85)%Mo-0.8%C and Fe-1.75%Ni-0.5%Mo-1.5%Cu-0.8%C were prepared in a Turbula mixer. Green compacts were single pressed in a steel die at 660 MPa according to PN-EN ISO 2740 standard. Sinterhardening was carried out at 1250°C in a mixture of 95% N2+5% H2 for 60 minutes. Mechanical tests (tensile, bend, hardness) and microstructural investigations were performed. Additionally, XRD and EDS analysis, fractographic investigations were carried out. The microstructures of steels investigated were mainly bainitic or bainitic-martensitic. Addition 1% Mn to Distaloy AQ based steel caused increase of tensile properties (YS from 422 to 489 MPa, UTS from 522 to 638 MPa, TRS from 901 to 1096 MPa) and decrease of plasticity (elongation from 3.65 to 2.84%).

  19. Inelastic constitutive models for the simulation of a cyclic softening behavior of modified 9Cr-lMo steel at elevated temperatures

    International Nuclear Information System (INIS)

    Koo, Gyeong Hoi; Lee, Jae Han

    2007-01-01

    In this paper, the inelastic constitutive models for the simulations of the cyclic softening behavior of the modified 9Cr-1Mo steel, which has a significant cyclic softening characteristic especially in elevated temperature regions, are investigated in detail. To do this, the plastic modulus, which primarily governs the calculation scheme of the plasticity, is formulated for the inelastic constitutive models such as the Armstrong-Frederick model, Chaboche model, and Ohno-Wang model. By implementing the extracted plastic modulus and the consistency conditions into the computer program, the inelastic constitutive parameters are identified to present the best fit of the uniaxial cyclic test data by strain-controlled simulations. From the computer simulations by using the obtained constitutive parameters, it is found that the Armstrong-Frederick model is simple to use but it causes significant overestimated strain results when compared with the Chaboche and the Ohno-Wang models. And from the ratcheting simulation results, it is found that the cyclic softening behavior of the modified 9Cr-1Mo steel can invoke a ratcheting instability when the applied cyclic loads exceed a certain level of the ratchet loading condition

  20. Tribological properties and surface structures of ion implanted 9Cr18Mo stainless steels

    Science.gov (United States)

    Fengbin, Liu; Guohao, Fu; Yan, Cui; Qiguo, Sun; Min, Qu; Yi, Sun

    2013-07-01

    The polished quenched-and-tempered 9Cr18Mo steels were implanted with N ions and Ti ions respectively at a fluence of 2 × 1017 ions/cm2. The mechanical properties of the samples were investigated by using nanoindenter and tribometer. The results showed that the ion implantations would improve the nanohardness and tribological property, especially N ion implantation. The surface analysis of the implanted samples was carried out by using XRD, XPS and AES. It indicated that the surface exhibits graded layers after ion implantation. For N ion implantation, the surface about 20 nm thickness is mainly composed of supersaturated interstitial N solid solution, oxynitrides, CrxCy phase and metal nitrides. In the subsurface region, the metal nitrides dominate and the other phases disappear. For Ti ion implantation, the surface of about 20 nm thickness is mainly composed of titanium oxides and carbon amorphous phase, the interstitial solid solution of Ti in Fe is abundant in the subsurface region. The surface components and structures have significant contributions to the improved mechanical properties.

  1. Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application

    Science.gov (United States)

    Muralidharan, Govindarajan

    2017-09-05

    An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.

  2. Evaluation of strength property variations across 9Cr-1Mo steel weld joints using automated ball indentation (ABI) technique

    International Nuclear Information System (INIS)

    Nagaraju, S.; GaneshKumar, J.; Vasantharaja, P.; Vasudevan, M.; Laha, K.

    2017-01-01

    The variations of strength properties across 9Cr-1Mo steel weld joints fabricated by different arc welding processes such as shielded metal arc welding (SMAW), tungsten inert gas (TIG) and activated tungsten inert gas (A-TIG) have been evaluated employing automatic ball indentation (ABI) technique. ABI tests were conducted at 298 K across various zones of the weld joints comprising of base metal, weld metal, heat affected zone (HAZ) and intercritical HAZ (ICHAZ) regions. The flow curves obtained from ABI tests were correlated with corresponding conventional tensile test results. In general, the tensile strength decreased systematically across the weld joint from weld metal to base metal. Inter critical HAZ exhibited the least strength implying that it is the weakest zone. The incomplete phase transformation in the ICHAZ during weld thermal cycle caused the softening. The A-TIG weld metal exhibited higher UTS and strain hardening values due to higher carbon in the martensite. The strain hardening exponent exhibited only slight variation across the various regions of the weld joints. A-TIG weld joint exhibited higher weld metal and HAZ strength, marginally higher UTS to YS ratio in the weld metal and HAZ compared to that of the other two processes. Hence, among the three welding processes chosen, A-TIG welding process is found to be superior in producing a 9Cr-1Mo steel weld joint with better strength properties.

  3. Evaluation of strength property variations across 9Cr-1Mo steel weld joints using automated ball indentation (ABI) technique

    Energy Technology Data Exchange (ETDEWEB)

    Nagaraju, S. [Nuclear Recycle Board, BARCF, Kalpakkam (India); GaneshKumar, J.; Vasantharaja, P. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Vasudevan, M., E-mail: dev@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Laha, K. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    2017-05-17

    The variations of strength properties across 9Cr-1Mo steel weld joints fabricated by different arc welding processes such as shielded metal arc welding (SMAW), tungsten inert gas (TIG) and activated tungsten inert gas (A-TIG) have been evaluated employing automatic ball indentation (ABI) technique. ABI tests were conducted at 298 K across various zones of the weld joints comprising of base metal, weld metal, heat affected zone (HAZ) and intercritical HAZ (ICHAZ) regions. The flow curves obtained from ABI tests were correlated with corresponding conventional tensile test results. In general, the tensile strength decreased systematically across the weld joint from weld metal to base metal. Inter critical HAZ exhibited the least strength implying that it is the weakest zone. The incomplete phase transformation in the ICHAZ during weld thermal cycle caused the softening. The A-TIG weld metal exhibited higher UTS and strain hardening values due to higher carbon in the martensite. The strain hardening exponent exhibited only slight variation across the various regions of the weld joints. A-TIG weld joint exhibited higher weld metal and HAZ strength, marginally higher UTS to YS ratio in the weld metal and HAZ compared to that of the other two processes. Hence, among the three welding processes chosen, A-TIG welding process is found to be superior in producing a 9Cr-1Mo steel weld joint with better strength properties.

  4. How TEM Projection Artifacts Distort Microstructure Measurements: A Case Study in a 9 pct Cr-Mo-V Steel

    Science.gov (United States)

    Monsegue, Niven; Reynolds, William T.; Hawk, Jeffrey A.; Murayama, Mitsuhiro

    2014-08-01

    Morphological data obtained from two-dimensional (2D) and three-dimensional (3D) transmission electron microscopy (TEM) observations were compared to assess the effects of TEM projection errors for submicron-size precipitates. The microstructure consisted of M23C6 carbides in a 9 pct Cr-Mo-V heat resistant steel before and after exposure to creep conditions. Measurements obtained from about 800 carbides demonstrate that particle size and spacing estimates made from 2D observations overestimate the more accurate values obtained from 3D reconstructions. The 3D analysis also revealed the M23C6 precipitates lengthen anisotropically along lath boundary planes, suggesting that coarsening during the early stage of creep in this alloy system is governed by grain boundary diffusion.

  5. Effect of boron on the hot ductility of 2.25Cr1Mo steel

    International Nuclear Information System (INIS)

    Song, S.-H.; Guo, A.-M.; Shen, D.-D.; Yuan, Z.-X.; Liu, J.; Xu, T.-D.

    2003-01-01

    The effect of boron on the hot ductility of 2.25Cr1Mo steel is investigated by means of a Gleeble 2000 thermomechanical simulator. There is a trough in the hot ductility-temperature curve, which is located between 1000 and 700 deg. C. The ductility trough shifts to lower temperatures with increasing boron content and the hot brittle range becomes shallow and narrow. In general, boron may improve the steel hot ductility in that it may retard the formation of pro-eutectoid ferrite and increase grain boundary cohesion. These effects may be related to the segregation of boron to austenite grain boundaries

  6. Residual stresses in 2 1/4Cr1Mo welds

    International Nuclear Information System (INIS)

    Fidler, R.; Jerram, K.

    1978-01-01

    Two separate investigations, initiated in an attempt to explain the large amount of residual stress scatter previously observed in the weld metal of eighteen nominally identical thick-section 2 1/4Cr1Mo butt welds, are described in this paper. The first examined the detailed surface residual stress distributions in 2 1/4Cr1Mo manual arc circumferential butt welds in 80mm and 100mm thick 1/2Cr1/2Mo1/4V steam pipe. High residual stresses were found in the regions of overlap between adjacent weld beads, with low values in virgin weld metal. The second utilised single pass manual metal arc bead-in-groove welds to investigate the effects of preheat and weld metal composition on weld metal residual stresses. In four weld metals, mild steel, 1/2Cr1/2Mo1/4V, 1Cr1/2Mo, and 2 1/4Cr1Mo, the residual stresses were very similar, becoming less tensile (or more compressive) with increase of preheat, while the residual stresses in the fifth weld metal (12Cr) were significantly different, being compressive and less affected by preheat. In both investigations the effects have been described in terms of the basic metallurgical phenomena occurring in the weld metal. (author)

  7. Evaluation of 2 1/4 Cr-1 Mo steel for liquid lithium containment. II. Effects of post-weld heat treatment and niobium content. Annual report, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, T.L.; Edwards, G.R.

    1979-01-01

    The lithium corrosion resistance of the regular grade of 2 1/4 Cr-1 Mo steel can be vastly improved with a proper postweld heat treatment, but even greater improvements are needed. Results indicate that if weldments were tempered sufficiently long at 760C to remove all Mo/sub 2/C from the microstructure, even greater resistance to attack by low nitrogen lithium could be achieved. Corrosion tests should eventually be performed on regular grade 2 1/4 Cr-1 Mo steel weldments which have been given a long-term (> 25 h) post-weld temper at 760C. Lithium corrosion resistance of regular grade 2 1/4 Cr-1 Mo steel may also be improved by employing a quench and temper heat treatment. Quenched microstructures have more homogenous distribution of carbides than isothermally annealed microstructures, and if properly tempered, should provide excellent lithium corrosion resistance. Furthermore, the toughness of such a lower bainite microstructure should be better than that of the ferrite-bainitic microstructure created by an isothermal anneal. Numerous parameters, all potentially deleterious to the lithium corrosion resistance of 2 1/4 Cr-1 Mo steel, remain to be investigated; two such variables are velocity effects and lead content in the lithium.

  8. Evaluation of 2 1/4 Cr-1 Mo steel for liquid lithium containment. II. Effects of post-weld heat treatment and niobium content. Annual report, 1979

    International Nuclear Information System (INIS)

    Anderson, T.L.; Edwards, G.R.

    1979-01-01

    The lithium corrosion resistance of the regular grade of 2 1/4 Cr-1 Mo steel can be vastly improved with a proper postweld heat treatment, but even greater improvements are needed. Results indicate that if weldments were tempered sufficiently long at 760C to remove all Mo 2 C from the microstructure, even greater resistance to attack by low nitrogen lithium could be achieved. Corrosion tests should eventually be performed on regular grade 2 1/4 Cr-1 Mo steel weldments which have been given a long-term (> 25 h) post-weld temper at 760C. Lithium corrosion resistance of regular grade 2 1/4 Cr-1 Mo steel may also be improved by employing a quench and temper heat treatment. Quenched microstructures have more homogenous distribution of carbides than isothermally annealed microstructures, and if properly tempered, should provide excellent lithium corrosion resistance. Furthermore, the toughness of such a lower bainite microstructure should be better than that of the ferrite-bainitic microstructure created by an isothermal anneal. Numerous parameters, all potentially deleterious to the lithium corrosion resistance of 2 1/4 Cr-1 Mo steel, remain to be investigated; two such variables are velocity effects and lead content in the lithium

  9. Prediction of Ductile Fracture Behaviors for 42CrMo Steel at Elevated Temperatures

    Science.gov (United States)

    Lin, Y. C.; Liu, Yan-Xing; Liu, Ge; Chen, Ming-Song; Huang, Yuan-Chun

    2015-01-01

    The ductile fracture behaviors of 42CrMo steel are studied by hot tensile tests with the deformation temperature range of 1123-1373 K and strain rate range of 0.0001-0.1 s-1. Effects of deformation temperature and strain rate on the flow stress and fracture strain of the studied steel are discussed in detail. Based on the experimental results, a ductile damage model is established to describe the combined effects of deformation temperature and strain rate on the ductile fracture behaviors of 42CrMo steel. It is found that the flow stress first increases to a peak value and then decreases, showing an obvious dynamic softening. This is mainly attributed to the dynamic recrystallization and material intrinsic damage during the hot tensile deformation. The established damage model is verified by hot forging experiments and finite element simulations. Comparisons between the predicted and experimental results indicate that the established ductile damage model is capable of predicting the fracture behaviors of 42CrMo steel during hot forging.

  10. Influence of heat treatment on microstructure and properties of GX12CrMoVNbN9-1 cast steel

    Directory of Open Access Journals (Sweden)

    G. Golański

    2010-07-01

    Full Text Available The paper presents results of research on the influence of multistage heat treatment on microstructure and properties of high-chromiummartensitic GX12CrMoVNbN9 – 1 (GP91 steel. The material under investigation were samples taken out from a test coupon. Heattreatment of GP91 cast steel was performed at the parameters of temperature and time typical of treatment for multi-ton steel casts. The research has proved that in the as-received condition (as-cast state GP91 cast steel was characterized by a coarse grain, martensitic microstructure which provided the required standard mechanical properties. The heat treatment of GP91 cast steel contributed to obtainment of a fine grain microstructure of high tempered martensite with numerous precipitations of carbides of diverse size. The GP91 cast steel structure received through heat treatment made it possible to obtain high plastic properties, particularly impact strength, maintaining strength properties on the level of the required minimum.

  11. Study of 13Cr-4Ni-(Mo (F6NM Steel Grade Heat Treatment for Maximum Hardness Control in Industrial Heats

    Directory of Open Access Journals (Sweden)

    Massimo De Sanctis

    2017-09-01

    Full Text Available The standard NACE MR0175 (ISO 15156 requires a maximum hardness value of 23 HRC for 13Cr-4Ni-(Mo steel grade for sour service, requiring a double tempering heat treatment at temperature in the range 648–691 °C for the first tempering and 593–621 °C for the second tempering. Difficulties in limiting alloy hardness after the tempering of forged mechanical components (F6NM are often faced. Variables affecting the thermal behavior of 13Cr-4Ni-(Mo during single and double tempering treatments have been studied by means of transmission electron microscopy (TEM observations, X-ray diffraction measurements, dilatometry, and thermo-mechanical simulations. It has been found that relatively low Ac1 temperatures in this alloy induce the formation of austenite phase above 600 °C during tempering, and that the formed, reverted austenite tends to be unstable upon cooling, thus contributing to the increase of final hardness via transformation to virgin martensite. Therefore, it is necessary to increase the Ac1 temperature as much as possible to allow the tempering of martensite at the temperature range required by NACE without the detrimental formation of virgin martensite upon final cooling. Attempts to do so have been carried out by reducing both carbon (<0.02% C and nitrogen (<100 ppm levels. Results obtained herein show final hardness below NACE limits without an unacceptable loss of mechanical strength.

  12. Development of the dentistry alloy Ni-Cr-Nb; Desenvolvimento de ligas odontologicas Ni-Cr-Nb

    Energy Technology Data Exchange (ETDEWEB)

    Souza, M.A.; Ramos, A.S.; Hashimoto, T.M., E-mail: mari_sou@hotmail.co [UNESP/FEG, Guaratingueta, SP (Brazil). Fac. de Engenharia. Dept. de Materiais e Tecnologia

    2010-07-01

    This work reports on the structural characterization of Ni-Cr-Mo and Ni-Cr-Nb alloys produced by arc melting. Samples were characterized by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and EDS analysis. Results indicated that the arc melting process was efficient to produce homogeneous structures in Ni-Cr-Mo and Ni-Cr-Nb alloys. The nickel dissolved large amounts of Cr, Mo and Nb, which was detected by EDS analysis and X-ray diffraction. The alloy containing molybdenum indicated the presence of structure based on Ni{sub SS}, while that the alloys containing niobium presented primary grains of Ni{sub SS} and precipitates formed by the simultaneous transformation of the Ni and Ni{sub 3}Nb phases. (author)

  13. Microstructural evolution in modified 9Cr-1Mo ferritic/martensitic steel irradiated with mixed high-energy proton and neutron spectra at low temperatures

    International Nuclear Information System (INIS)

    Sencer, B.H.; Garner, F.A.; Gelles, D.S.; Bond, G.M.; Maloy, S.A.

    2002-01-01

    Modified 9Cr-1Mo ferritic/martensitic steel was exposed at 32-57 deg. C to a mixed proton/neutron particle flux and spectrum at the Los Alamos Neutron Science Center. The microstructure of unirradiated 9Cr-1Mo consists of laths, dislocations and carbides. Examination of electron diffraction patterns obtained from extraction replicas of unirradiated 9Cr-1Mo revealed that the precipitate microstructure was primarily dominated by M 23 C 6 carbides. The post-irradiation microstructure contained black-spot damage in addition to precipitates and dislocations. Examination of electron diffraction patterns revealed diffuse rings from M 23 C 6 carbides, indicating amorphization and/or nanocrystallinity. Crystalline MC carbides were also found. No cavity formation was found although a significant amount of helium and hydrogen generation had been generated. TEM-EDS examination of extraction replicas for carbides from unirradiated and irradiated samples did not show any detectable changes in composition of either M 23 C 6 or MC carbides. There was also no evident change in carbide size. Lattice images of M 23 C 6 carbides revealed an amorphous microstructure following irradiation, but MC carbides were still crystalline

  14. Modified 9Cr-1Mo steel for advanced steam generator applications

    International Nuclear Information System (INIS)

    Brinkman, C.R.; Alexander, D.J.; Maziasz, P.J.

    1990-01-01

    Results are reported from several types of mechanical property tests conducted on a number of commercial heats of modified 9Cr-1Mo steel. Data from long term creep-rupture tests conducted on base and weldment material were compared with an analytical model which has been shown to give good agreement between measured and predicted values. Weldment material had somewhat inferior creep-rupture strength in comparison to base material due to a soft zone at the edge of the HAZ. Data are presented from elevated temperature tensile and creep-rupture tests conducted n material thermally aged for periods of up to 75,000 h (8.6 years). Some reduction in strength was shown to occur in comparison to unaged material. Models were developed for predicting the reduction in short term elevated temperature tensile and yield strength for material thermally aged in the temperature range of 482 to 704 degree C. Results from Charpy impact tests conducted on material thermally aged at 538 degree C for periods of up to 75,000 h showed an increase in the ductile-brittle transition temperature. Finally, results from transmission electron microscopy studies were presented to explain changes in mechanical properties due to thermal aging. These observations showed that Laves phase precipitation and recovery occurs on prolonged exposure of this alloy in this temperature range. 9 refs

  15. The Phase Transformations in Hypoeutectoid Steels Mn-Cr-Ni

    Directory of Open Access Journals (Sweden)

    RoŻniata E.

    2015-04-01

    Full Text Available The results of a microstructure and hardness investigations of the hypoeutectoid steels Mn-Cr-Ni, imitating by its chemical composition toughening steels, are presented in the paper. The analysis of the kinetics of phase transformations of undercooled austenite of steels containing different amounts of alloying elements in their chemical composition, constitutes the aim of investigations.

  16. Alloy Design and Development of Cast Cr-W-V Ferritic Steels for Improved High-Temperature Strength for Power Generation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R L; Maziasz, P J; Vitek, J M; Evans, N D; Hashimoto, N

    2006-09-23

    Economic and environmental concerns demand that the power-generation industry seek increased efficiency for gas turbines. Higher efficiency requires higher operating temperatures, with the objective temperature for the hottest sections of new systems {approx} 593 C, and increasing to {approx} 650 C. Because of their good thermal properties, Cr-Mo-V cast ferritic steels are currently used for components such as rotors, casings, pipes, etc., but new steels are required for the new operating conditions. The Oak Ridge National Laboratory (ORNL) has developed new wrought Cr-W-V steels with 3-9% Cr, 2-3% W, 0.25% V (compositions are in wt.%), and minor amounts of additional elements. These steels have the strength and toughness required for turbine applications. Since cast alloys are expected to behave differently from wrought material, work was pursued to develop new cast steels based on the ORNL wrought compositions. Nine casting test blocks with 3, 9, and 11% Cr were obtained. Eight were Cr-W-V-Ta-type steels based on the ORNL wrought steels; the ninth was COST CB2, a 9Cr-Mo-Co-V-Nb cast steel, which was the most promising cast steel developed in a European alloy-development program. The COST CB2 was used as a control to which the new compositions were compared, and this also provided a comparison between Cr-W-V-Ta and Cr-Mo-V-Nb compositions. Heat treatment studies were carried out on the nine castings to determine normalizing-and-tempering treatments. Microstructures were characterized by both optical and transmission electron microscopy (TEM). Tensile, impact, and creep tests were conducted. Test results on the first nine cast steel compositions indicated that properties of the 9Cr-Mo-Co-V-Nb composition of COST CB2 were better than those of the 3Cr-, 9Cr-, and 11Cr-W-V-Ta steels. Analysis of the results of this first iteration using computational thermodynamics raised the question of the effectiveness in cast steels of the Cr-W-V-Ta combination versus the Cr-Mo

  17. Creep and Oxidation Behavior of Modified CF8C-Plus with W, Cu, Ni, and Cr

    Science.gov (United States)

    Unocic, Kinga A.; Dryepondt, Sebastien; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-04-01

    The microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-rich Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.

  18. Neutron irradiation embrittlement of reactor pressure vessel steel 20 MnMoNi55 weld

    International Nuclear Information System (INIS)

    Ghoneim, M.M.

    1987-05-01

    The effect of neutron irradiation on the mechanical and fracture properties of an 'improved' 20 MnMoNi 55 Pressure Vessel Steel (PVS) weld was investigated. In addition to very low residual element content, especially Cu (0.035 wt.%), and relatively higher Ni content (0.9 wt.%), this steel has higher strength (30% more) than the steels used currently in nuclear reactor pressure vessels. The material was irradiated to 3.5x10 19 and 7x10 19 n/cm 2 (E > 1 Mev) at 290 0 C and 2.5x10 19 n/cm 2 (E > 1 MeV) at 160 0 C in FRJ-1 and FRJ-2 research reactors at KFA, Juelich, F.R.G. Test methods used in the evaluation included instrumented impact testing of standard and precracked Charpy specimens, tensile, and fracture toughness testing. Instrumented impact testing provided load and energy vs. time (deflection) data in addition to energy absorption data. The results indicated that the investigated high strength improved steel is more resistant to irradiation induced embrittlement than conventional PVSs. (orig./IHOE)

  19. Experimental observations of transient phases during long-range ordering to Ni4Mo in a Ni-Mo-Fe-Cr alloy

    International Nuclear Information System (INIS)

    Tawancy, H.M.; Aboelfotoh, M.O.

    1987-01-01

    Experimental observations are reported of transient phases which form during long-range ordering to Ni 4 Mo (f.c.c. → Dl/sub a/ superlattice) in the quaternary alloy Ni-19.2 at% Mo-1.2 at% Fe-1.06 at% Cr using electron diffraction. In the early stages of ordering during isothermal annealing, diffuse intensity maxima centered at the short-range order reflections (1 1/2 O)/sub f.c.c./ and along /sub f.c.c./ directions are observed. Subsequently, a DO 22 superlattice is generated from the short-range order state. The coexistence of the DO 22 , Pt 2 Mo-type, and Dl/sub a/ superlattices is observed in this alloy system which indicates that these three superlattices have similar energy. With continued annealing, both the DO 22 and Pt 2 Mo-type superlattices have similar energy. With continued annealing, both the DO 22 and Pt 2 Mo-type superlattices disappear, indicating that they are transient phases. These results are not inconsistent with the theoretical treatments of ordered alloys which are based on an Ising model with pairwise atomic interactions. (author)

  20. Z-phase in 9-12% Cr Steels

    DEFF Research Database (Denmark)

    Danielsen, Hilmar; Hald, John

    2004-01-01

    The complex nitride Z-phase, Cr(V,Nb)N, has recently been identified as a major cause for premature breakdown in creep strength of a number of new 9-12%Cr martensitic steels. A thermodynamic model of the Z-phase has been created based on the Thermo-Calc software. The model predicts the Z-phase to......The complex nitride Z-phase, Cr(V,Nb)N, has recently been identified as a major cause for premature breakdown in creep strength of a number of new 9-12%Cr martensitic steels. A thermodynamic model of the Z-phase has been created based on the Thermo-Calc software. The model predicts the Z......-phase to be stable in all of the new 9-12%Cr martensitic steels. This has generally been confirmed by the performed experiments. Z-phase precipitation seems to be a kinetic problem, and drivning force calculations using Thermo-Calc with the developed model have been used to predict steel compositions, which...

  1. Interaction of high cycle fatigue and creep in 9%Cr-1%Mo steel at elevated temperature

    International Nuclear Information System (INIS)

    Vasina, R.; Lukas, P.; Kunz, L.; Sklenicka, V.

    1995-01-01

    High-cycle-fatigue/creep experiments were performed on a 9%Cr-1%Mo tempered martensite ferritic steel at 873 K in air. The stress ratio R = σ min /σ max ranged from -1 (''pure'' fatigue) to 1 (''pure'' creep). The maximum stress σ max was kept constant at 240 MPa.The lifetime depends on the stress ratio R in a non-monotonic way. In the stress ratio interval 0.6 mean of the stress cycle. In the stress ratio interval -1 a . The fatigue/creep interaction occurs in between these intervals. The fatigue/creep loading induces transformation of the tempered martensite ferritic structure into an equiaxed subgrain structure. The resulting subgrain size depends strongly on the stress ratio. (author)

  2. Fatigue crack growth and endurance data on 9% Cr 1% Mo steels for AGR applications

    International Nuclear Information System (INIS)

    Priddle, E.K.

    1987-01-01

    Experimental investigations have been carried out on 9%Cr 1%Mo steels to examine: (1) The significance of carburisation on the fatigue endurance of plain and welded boiler tubes, and tube spacer strip; (2) the high cycle fatigue endurance of spacer strip and spacer weld metal; (3) fatigue crack growth rates in spacer strip and spacer weld metal. This report summarises the results of these investigations and where necessary compares the data to that in current data sheets. The effects of carburisation are variable depending on the structure and type of carburisation. The fatigue endurance properties of spacer strip and spacer weld metal are also similar and need not be considered separately for assessment or design purposes. Fatigue crack growth rates in spacer strip and space weld metal are similar and are influenced by both stress ratio and temperature. A design curve from a fast reactor data sheet may be used as an upper bound to these fatigue crack growth results. (author)

  3. Microstructure and wear behaviors of laser clad NiCr/Cr3C2-WS2 high temperature self-lubricating wear-resistant composite coating

    Science.gov (United States)

    Yang, Mao-Sheng; Liu, Xiu-Bo; Fan, Ji-Wei; He, Xiang-Ming; Shi, Shi-Hong; Fu, Ge-Yan; Wang, Ming-Di; Chen, Shu-Fa

    2012-02-01

    The high temperature self-lubricating wear-resistant NiCr/Cr3C2-30%WS2 coating and wear-resistant NiCr/Cr3C2 coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17 °C), 300 °C and 600 °C, respectively. Results indicated that the laser clad NiCr/Cr3C2 coating consisted of Cr7C3 primary phase and γ-(Fe,Ni)/Cr7C3 eutectic colony, while the coating added with WS2 was mainly composed of Cr7C3 and (Cr,W)C carbides, with the lubricating WS2 and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr3C2-30%WS2 is lower than the coating without WS2 whatever at room-temperature, 300 °C, 600 °C, but its wear rate is only lower at 300 °C. It is considered that the laser clad NiCr/Cr3C2-30%WS2 composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300 °C.

  4. Behaviour of Z phase in 9–12%Cr steels

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2006-01-01

    The literature on the behaviour of modified Z phase Cr(V,Nb)N in creep resistant martensitic 9–12%Cr steels is briefly reviewed. Ten different 9–12%Cr steels were investigated after prolonged exposure at 600–660uC; the modified Z phase was found in all of them. In steels with high Cr content (11......–12%), Z phase precipitates much faster than in 9%Cr steels. Precipitation of Z phase is associated with dissolution of MX carbonitrides, and causes a breakdown in long term creep strength in 9–12%Cr steels. High Cr steels show creep instabilities accompanied with Z phase precipitation, whereas low Cr...... steels show good long term creep stability. A niobium free CrVN variant of the modified Z phase was observed for the first time during the course of this work. The solution temperature of the Cr(V,Nb)N and CrVN modified Z phases was found to be close to 800uC for 11–12%Cr steels, much lower than the 1200...

  5. Comparison of SA508 Gr.3 and SA508 Gr.4N Low Alloy Steels for Reactor Pressure Vessel Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Chul; Lee, B. S

    2009-12-15

    The microstructural characteristics and mechanical properties of SA508 Gr.3 Mn-Mo-Ni low alloy steel and SA508 Gr.4N Ni-Mo-Cr low alloy steel were investigated. The differences in the stable phases between these two low alloy steels were evaluated by means of a thermodynamic calculation using ThermoCalc. They were then compared to microstructural features and correlated with mechanical properties. Mn-Mo-Ni low alloy steel shows the upper bainite structure which has the coarse cementite in the lath boundaries. However, Ni-Mo-Cr low alloy steel shows the mixture of lower bainite and tempered martensite structure that homogeneously precipitates the small carbides such as M{sub 23}C{sub 6} and M{sub 7}C{sub 3} due to an increase of hardenability and Cr addition. In the mechanical properties, Ni-Mo-Cr low alloy steel has higher strength and toughness than Mn-Mo-Ni low alloy steel. Ni and Cr additions increase the strength by solid solution hardening. Besides, microstructural changes from upper bainite to tempered martensite improve the strength of the low alloy steel by grain refining effect. And the changes in the precipitation behavior by Cr addition improve the ductile-brittle transition behavior along with a toughening effect of Ni addition.

  6. Effect of microstructure on the mechanical properties of a commercial 12Cr-1Mo steel (HT-9)

    International Nuclear Information System (INIS)

    Lechtenberg, T.A.

    1981-08-01

    The microstructure of a commercial 12Cr-1Mo steel (HT-9) and its associated effect on strength and toughness properties is being studied in a continuing program aimed at qualifying the alloy for use in fusion energy machines. Interim results show this alloy is subject to a degree of tempered martensite embrittlement and temper embrittlement. For applications projected for fusion machines at lower temperatures, a new heat treatment (1000 0 C, 1 h, air-cooled followed by 650 0 C tempering) at lower temperatures and shorter times than the vendor-recommended heat treatment has been identified. Microstructural differences between the treatments are discussed, and mechanical properties are correlated. 6 figures

  7. The morphology and ageing behaviour of δ-ferrite in a modified 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Kishore, R.; Singh, R.N.; Sinha, T.K.; Kashyap, B.P.

    1992-01-01

    Dual phase (martensite + δ-ferrite) microstructures were developed in a modified 9Cr-1Mo steel, by austenitising at 1523-1623 K, followed by water-quenching. These duplex structures were thermally aged at 973 K for ageing periods varying from 30 min to 21 h. Morphological aspects of δ-ferrite phase and its response to age-hardening were studied by optical, scanning electron and transmission electron microscopy, X-ray diffraction, electron probe microanalysis and microhardness testing. It was observed that austenitizing at 1523 K produced fine, acicular δ-ferrite while the δ-ferrite formed by austenitising at higher temperatures (1573-623 K) were massive, irregular-shaped and banded. Moreover the presence of δ-ferrite caused an abnormally strong (110) reflection, observed in X-ray diffraction patterns of martensite plus δ-ferrite structures. This behaviour is thought to be due to development of (110) texture in δ-ferrite phase. Thermal ageing at 973 K caused age-hardening of δ-ferrite with a peak hardness attained after 3.6 ks of ageing. Electron microscopic results suggest that the observed hardening was caused by the formation of Fe 2 Mo Laves phase. (orig.)

  8. Development of ferritic steels for fusion reactor applications

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Maziasz, P.J.; Corwin, W.R.

    1988-08-01

    Chromium-molybdenum ferritic (martensitic) steels are leading candidates for the structural components for future fusion reactors. However, irradiation of such steels in a fusion environment will produce long-lived radioactive isotopes that will lead to difficult waste-disposal problems. Such problems could be reduced by replacing the elements in the steels (i.e., Mo, Nb, Ni, N, and Cu) that lead to long-lived radioactive isotopes. We have proposed the development of ferritic steels analogous to conventional Cr-Mo steels, which contain molybdenum and niobium. It is proposed that molybdenum be replaced by tungsten and niobium be replaced by tantalum. Eight experimental steels were produced. Chromium concentrations of 2.25, 5, 9, and 12% were used (all concentrations are in wt %). Steels with these chromium compositions, each containing 2% W and 0.25% V, were produced. To determine the effect of tungsten and vanadium, 2.25 Cr steels were produced with 2% W and no vanadium and with 0.25% V and O and 1% W. A 9Cr steel containing 2% W, 0.25 V, and 0.07% Ta was also studied. For all alloys, carbon was maintained at 0.1%. Tempering studies on the normalized steels indicated that the tempering behavior of the new Cr-W steels was similar to that of the analogous Cr-Mo steels. Microscopy studies indicated that 2% tungsten was required in the 2.25 Cr steels to produce 100% bainite in 15.9-mm-thick plate during normalization. The 5Cr and 9Cr steels were 100% martensite, but the 12 Cr steel contained about 75% martensite with the balance delta-ferrite. 33 refs., 35 figs., 5 tabs.

  9. Development of ferritic steels for fusion reactor applications

    International Nuclear Information System (INIS)

    Klueh, R.L.; Maziasz, P.J.; Corwin, W.R.

    1988-08-01

    Chromium-molybdenum ferritic (martensitic) steels are leading candidates for the structural components for future fusion reactors. However, irradiation of such steels in a fusion environment will produce long-lived radioactive isotopes that will lead to difficult waste-disposal problems. Such problems could be reduced by replacing the elements in the steels (i.e., Mo, Nb, Ni, N, and Cu) that lead to long-lived radioactive isotopes. We have proposed the development of ferritic steels analogous to conventional Cr-Mo steels, which contain molybdenum and niobium. It is proposed that molybdenum be replaced by tungsten and niobium be replaced by tantalum. Eight experimental steels were produced. Chromium concentrations of 2.25, 5, 9, and 12% were used (all concentrations are in wt %). Steels with these chromium compositions, each containing 2% W and 0.25% V, were produced. To determine the effect of tungsten and vanadium, 2.25 Cr steels were produced with 2% W and no vanadium and with 0.25% V and O and 1% W. A 9Cr steel containing 2% W, 0.25 V, and 0.07% Ta was also studied. For all alloys, carbon was maintained at 0.1%. Tempering studies on the normalized steels indicated that the tempering behavior of the new Cr-W steels was similar to that of the analogous Cr-Mo steels. Microscopy studies indicated that 2% tungsten was required in the 2.25 Cr steels to produce 100% bainite in 15.9-mm-thick plate during normalization. The 5Cr and 9Cr steels were 100% martensite, but the 12 Cr steel contained about 75% martensite with the balance delta-ferrite. 33 refs., 35 figs., 5 tabs

  10. Microstructure characteristics and temperature-dependent high cycle fatigue behavior of advanced 9% Cr/CrMoV dissimilarly welded joint

    International Nuclear Information System (INIS)

    Wu, Qingjun; Lu, Fenggui; Cui, Haichao; Ding, Yuming; Liu, Xia; Gao, Yulai

    2014-01-01

    Advanced 9% Cr and CrMoV steels chosen as candidate materials are first welded by narrow-gap submerged arc welding (NG-SAW) to fabricate the heavy section rotor. The present work focuses on studying the high-cycle fatigue (HCF) behavior of advanced 9% Cr/CrMoV dissimilarly welded joint at different temperatures. Conditional fatigue strength of this dissimilarly welded joint was obtained by HCF tests at room temperature (RT), 400 °C and 470 °C. It was observed that the failure occurred at the side of CrMoV base metal (BM), weld metal (WM) and heat affected zone (HAZ) of CrMoV side over 5×10 7 cycles for the specimens tested at RT, 400 °C and 470 °C. The detailed microstructures of BMs, WMs and HAZs as well as fracture appearance were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Precipitation and aggregation of carbides along the grain boundaries were clearly detected with the increase of temperature, which brought a negative effect on the fatigue properties. It is interesting to note that the inclusion size leading to crack initiation became smaller for the HCF test at higher temperature. Therefore, reduction in the inclusion size in a welded joint helps to improve the HCF performance at high temperature

  11. Microstructure characteristics and temperature-dependent high cycle fatigue behavior of advanced 9% Cr/CrMoV dissimilarly welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qingjun [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Yuming; Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China)

    2014-10-06

    Advanced 9% Cr and CrMoV steels chosen as candidate materials are first welded by narrow-gap submerged arc welding (NG-SAW) to fabricate the heavy section rotor. The present work focuses on studying the high-cycle fatigue (HCF) behavior of advanced 9% Cr/CrMoV dissimilarly welded joint at different temperatures. Conditional fatigue strength of this dissimilarly welded joint was obtained by HCF tests at room temperature (RT), 400 °C and 470 °C. It was observed that the failure occurred at the side of CrMoV base metal (BM), weld metal (WM) and heat affected zone (HAZ) of CrMoV side over 5×10{sup 7} cycles for the specimens tested at RT, 400 °C and 470 °C. The detailed microstructures of BMs, WMs and HAZs as well as fracture appearance were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Precipitation and aggregation of carbides along the grain boundaries were clearly detected with the increase of temperature, which brought a negative effect on the fatigue properties. It is interesting to note that the inclusion size leading to crack initiation became smaller for the HCF test at higher temperature. Therefore, reduction in the inclusion size in a welded joint helps to improve the HCF performance at high temperature.

  12. Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments; Etude experimentale et modelisation, du comportement, de l'endommagement et de la rupture en fluage a haute temperature de joint soudes en acier 9Cr1Mo-NbV

    Energy Technology Data Exchange (ETDEWEB)

    Gaffard, V

    2004-12-15

    Chromium martensitic stainless steels are under development since the 70's with the prospect of using them as structural components in thermal and nuclear power plants. The modified 9Cr1Mo-NbV steel is already used, especially in England and Japan, as a material for structural components in thermal power plants where welding is a commonly used joining technique. New generations of chromium martensitic stainless steels with improved mechanical properties for high pressure and temperature use are currently under development. However, observations of several in-service premature failures of welded components in 9Cr1Mo-NbV steel, outline a strong need for understanding the high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steels and weldments. The present study aimed at experimentally determining and then modelling the high temperature creep flow and damage behaviour of both 9Cr1Mo-NbV steels and weldments (typically in the temperature range from 450 C to 650 C). The base metal was first studied as the reference material. It was especially evidenced that tempered chromium martensitic steels exhibit a change in both creep flow and damage behaviour for long term creep exposure. As a consequence, the classically performed extrapolation of 1,000 hours creep data to 100,000 hours creep lifetime predictions might be very hazardous. Based on experimental observations, a new model, integrating and coupling multiple creep flow and damage mechanisms, was developed in the framework of the mechanics of porous media. It was then successfully used to represent creep flow and damage behaviour of the base metal from high to low stress levels even for complex multiaxial loading conditions. Although the high temperature creep properties of the base metal are quite good, the occurrence of premature failure in weldments in high temperature creep conditions largely focused the attention of the scientific community. The lower creep strength of the weld component was also

  13. HAZ microstructure in joints made of X13CrMoCoVNbNB9-2-1 (PB2 steel welded with and without post-weld heat treatment

    Directory of Open Access Journals (Sweden)

    M. Łomozik

    2016-07-01

    Full Text Available The article presents the results of research butt welded joints made of X13CrMoCoVNbNB9-2-1 steel. The joints were welded with post-weld heat treatment PWHT and without PWHT, using the temper bead technique TBT. After welding the joint welded with PWHT underwent stress-relief annealing at 770 °C for 3 hours. The scope of structural tests included the microstructural examination of the coarse-grained heat affected zone (HAZ areas of the joints, the comparison of the morphology of these areas and the determination of carbide precipitate types of the coarse grain heat affected zone (CGHAZ of the joints welded with and without PWHT.

  14. Microstructure and phase transformations in laser clad CrxSy/Ni coating on H13 steel

    Science.gov (United States)

    Lei, Yiwen; Sun, Ronglu; Tang, Ying; Niu, Wei

    2015-03-01

    Laser cladding was carried out onto H13 steel with preplaced NiCrBSi+Ni/MoS2 powders using CO2 laser under the optimized experimental parameters of laser power 2 kW, scanning velocity 6 mm/s and laser beam diameter 3 mm. An X-ray diffractometer and scanning electron microscope with energy dispersive spectroscopy were applied to analyze the microstructure and phase compositions of the coating. Thermodynamic calculation was performed with Thermo-Calc software on the basis of a commercially available Ni-based Alloys' database. The experimental results show that MoS2 decomposed and S reacted with Cr to form nonstoichiometric CrxSy during the laser cladding process. The coating consists of spherical CrxSy particles, primary γ-Ni dendrite, interdendritic eutectic (γ-Ni+NiMo) and precipitated NiMo. The precipitated NiMo was fine and uniformly distributed in primary γ-Ni dendrite. The calculated results and experimental data indicate that the solidification process in the coating during laser cladding process was liquid→liquid+CrxSy→ liquid+CrxSy+γ-Ni→liquid+CrxSy+γ-Ni+ eutectic (γ-Ni+NiMo). A solid state phase transformation (fine and uniformly distributed NiMo precipitated from γ-Ni) occurred after the solidification process. The calculations agree well with the experimental data and it is helpful to understand the phase transformation and microstructure evolution in the coating.

  15. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    International Nuclear Information System (INIS)

    Schuon, S.R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life

  16. Evaluation of microstructure and mechanical properties of 50Cr5NiMoV steel for forged backup roll

    Energy Technology Data Exchange (ETDEWEB)

    Song, X.Y.; Zhang, X.J.; Fu, L.C.; Yang, H.B.; Yang, K.; Zhu, L., E-mail: zl508@126.com

    2016-11-20

    The microstructure and mechanical properties of forged 50Cr5NiMoV steel backup roll were evaluated in this study. The microstructure characteristics from surface to center along radial direction of the backup roll were carefully observed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the chemical composition, hardness, tensile property, impact and fracture toughness in different position of the backup roll were also examined. The results indicate that the finely precipitated carbides at different matrix during heat treatment process strongly influence mechanical properties of the backup roll. Especially, the spheroidized pearlite at the inner regions which consists of large globular or rod-like M{sub 7}C{sub 3} and a little of small globular M{sub 23}C{sub 6} possesses much better toughness and fracture resistance properties than those of the lamellar pearlite with lamellar M{sub 23}C{sub 6} and a little of globular M{sub 7}C{sub 3}.

  17. Overview of research trends and problems on Cr-Mo low alloy steels for pressure vessel

    International Nuclear Information System (INIS)

    Chi, Byung Ha; Kim, Jeong Tae

    2000-01-01

    Cr-Mo low alloy steels have been used for a long time for pressure vessel due to its excellent corrosion resistance, high temperature strength and toughness. The paper reviewed the latest trends on material development and some problems on Cr-Mo low alloy steel for pressure vessel, such as elevated temperature strength, hardenability, synergetic effect between temper and hydrogen embrittlement, hydrogen attack and hydrogen induced disbonding of overlay weld-cladding

  18. Determination of the Fe-Cr-Ni and Fe-Cr-Mo Phase Diagrams at Intermediate Temperatures using a Novel Dual-Anneal Diffusion-Multiple Approach

    Science.gov (United States)

    Cao, Siwei

    Phase diagrams at intermediate temperatures are critical both for alloy design and for improving the reliability of thermodynamic databases. There is a significant shortage of experimental data for phase diagrams at the intermediate temperatures which are defined as around half of the homologous melting point (in Kelvin). The goal of this study is to test a novel dual-anneal diffusion multiple (DADM) methodology for efficient determination of intermediate temperature phase diagrams using both the Fe-Cr-Ni and Fe-Cr-Mo systems as the test beds since both are very useful for steel development. Four Fe-Cr-Ni-Mo-Co diffusion multiples were made and annealed at 1200 °C for 500 hrs. One sample was used directly for evaluating the isothermal sections at 1200 ° C. The other samples (and cut slices) were used to perform a subsequent dual annealing at 900 °C (500 hrs), 800 °C (1000 hrs), 700 °C (1000 hrs), and 600 °C (4500 hrs), respectively. The second annealing induced phase precipitation from the supersaturated solid solutions that were created during the first 1200 °C annealing. Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to identify the phases and precipitation locations in order to obtain the compositions to construct the isothermal sections of both ternary systems at four different temperatures. The major results obtained from this study are isothermal sections of the Fe-Cr-Ni and Fe-Cr-Mo systems at 1200 °C, 900 °C, 800 °C, and 700 °C. For the Fe-Cr-Ni system, the results from DADMs agree with the majority of the literature results except for results at both 800 °C and 700 °C where the solubility of Cr in the fcc phase was found to be significantly higher than what was computed from thermodynamic calculations using the TCFE5 database. Overall, it seems that the Fe-Cr-Ni thermodynamic assessment only needs slight improvement to

  19. Electron-beam welding of 21-6-9 (Cr--Ni--Mn) stainless steel: effect of machine parameters on weldability

    International Nuclear Information System (INIS)

    Casey, H.

    1975-04-01

    The high-manganese, nitrogen-strengthened 21-6-9 (Cr--Ni--Mn) austenitic stainless steel has a weldability rating similar to that of more common austenitic stainless steels in terms of cracking, porosity, etc. However, weld pool disruption problems may occur with this alloy that can be related to instability within the molten weld pool. Selection of machine parameters is critical to achieving weld pool quiescence as this report confirms from recent tests. Test samples came from heats of air-melted, vacuum-arc remelted, and electroslag remelted material. Low- and high-voltage machine parameters are discussed, and effects of parameter variation on weld pool behavior are given. Data relate weld pool behavior to weld fusion-zone geometry. Various weld parameters are recommended for the 21-6-9 alloy, regardless of its source or chemistry. (auth)

  20. Relationship of bainitic microstructure to impact toughness in Cr-Mo and Cr-W steels

    International Nuclear Information System (INIS)

    Klueh, R.L.; Alexander, D.J.

    1992-01-01

    Non-classical bainite microstructures can develop during continuous cooling of low-carbon alloy steels. These differ from classical upper and lower bainite developed by isothermal transformation. Two non-classical bainite microstructures were produced in a 3Cr-1.5Mo0.25V-0.lC steel using different cooling rates after austenitizing--water quenching and air cooling. The carbide-free acicular bainite formed in the quenched steel had a lower ductile-brittle transition temperature (DBTT) than the granular bainite formed in the air-cooled steel. With increasing tempering parameter (defined bv tempering time and temperature), the DBTT of both decreased and approached a common value, although the final value occurred at a much lower tempering parameter for the quenched steel than for the air-cooled steel. The upper-shelf enery was similarly affected by microstructure. These observations along with similar observations in two Cr-W steels indicate that control of the bainite microstructure can be used to optimize strength and toughness

  1. First-Principles Study on the Structural Stability and Segregation Behavior of γ-Fe/Cr2N Interface with Alloying Additives M (M = Mn, V, Ti, Mo, and Ni

    Directory of Open Access Journals (Sweden)

    Hui Huang

    2016-07-01

    Full Text Available This study investigated the structural stability and electrochemical properties of alloying additives M (M = Mn, V, Ti, Mo, or Ni at the γ-Fe(111/Cr2N(0001 interface by the first-principles method. Results indicated that V and Ti were easily segregated at the γ-Fe(111/Cr2N(0001 interface and enhanced interfacial adhesive strength. By contrast, Ni and Mo were difficult to segregate at the γ-Fe(111/Cr2N(0001 interface. Moreover, the results of the work function demonstrated that alloying additives Mn reduced local electrochemical corrosion behavior of the γ-Fe(111/Cr2N(0001 interface by cutting down Volta potential difference (VPD between clean γ-Fe(111 and Cr2N(0001, while alloying additives V, Ti, Mo, and Ni at the γ-Fe(111/Cr2N(0001 interface magnified VPD between clean γ-Fe(111 and Cr2N(0001, which were low-potential sites that usually serve as local attack initiation points.

  2. Creep properties and simulation of weld repaired low alloy heat resistant CrMo and Mo steels at 540 deg C. Sub-project 2 - Ex-serviced 2.25Cr1M0 weld metal and cross weld repairs

    Energy Technology Data Exchange (ETDEWEB)

    Rui Wu; Storesund, Jan; Borggreen, Kjeld; Feilitzen, Carl von

    2007-12-15

    Weld repair has been carried out in an ex-serviced 10 CrMo 9 10 pipe by using 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 consumables. Application of current welding procedure and consumables results in an over matched weld repair. This is verified by both creep tests and the creep simulations at even lower stresses than tested. Creep specimens have been extracted from ex-serviced 10 CrMo 9 10 parent metal (PM) and weld metal (WM), from virgin 10 CrMo 9 10 WM, from virgin 13 CrMo 4 4 WM, and from virgin 15 Mo 3 WM. In addition, cross weld specimens including weld metal, heat affected zone (HAZ) and parent metal have been taken from the ex-serviced 10 CrMo 9 10 weld joint, and from three weld repairs. In total, there are nine test series. The sequence of creep lifetime at 540 deg C at given stresses is; virgin 10 CrMo 9 10 weld metal > virgin 15 Mo 3 weld metal approx virgin 13 CrMo 4 4 weld metal approx ex-serviced 10 CrMo 9 10 weld metal >> ex-serviced 10 CrMo 9 10 parent metal > ex-serviced 10 CrMo 9 10 cross weld approx 10 CrMo 9 10 cross weld repair approx 13 CrMo 4 4 cross weld repair approx and 15 Mo 3 cross weld repair. All the series show good creep ductility. The ex-serviced 10 CrMo 9 10 parent metal shows a creep lifetime about one order of magnitude shorter than that for both the virgin parent metal and the ex-serviced 10 CrMo 9 10 weld metal, independent of stresses. Differences in creep lifetime among the ex-serviced 10 CrMo 9 10 cross weld and other cross weld repairs are negligible, simply because rupture always occurred in the ex-serviced 10 CrMo 9 10 parent metal, approximately 10 mm from HAZ, for all the cross welds. Necking is frequently observed in the ex-serviced 10 CrMo 9 10 parent metal at the opposite side of the fracture. Creep damage to a large and a small extend is found adjacent to the fracture and at the necking area, respectively. Other parts of the weld joint like weld metal and HAZ are damage-free, independent of stress, weld metal and

  3. Ion bombardment damage in a modified Fe-9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Farrell, K.; Lee, E.H.

    1984-01-01

    A normalized-and-tempered Fe-9Cr-1Mo steel, with small Nb and V additions, was bombarded with 4-MeV iron ions to 100 dpa at 400, 450, 500, 550, and 600 0 C. Major damage feature was dislocation tangles which coarsened with increasing bombardment temperature. Sparse cavities were heterogeneously distributed at 500 and 550 0 C. Incorporation of helium and deuterium simultaneously in the bombardments at rates of 10 and 45 appM/dpa, respectively, introduced very high concentrations of small cavities at all temperatures, many of them on grain boundaries. These cavities were shown to be promoted by helium. A small fraction of the matrix cavities exhibited bias-driven growth at 500 and 550 0 C, with swelling 0 C higher than the peak swelling temperature found in neutron irradiations, which is compatible with the higher damage rate used in the ion bombardments. High concentrations of subgrain boundaries and dislocations resulting from the heat treatment, and unbalanced cavity and dislocation sink strengths in the damage structures contribute to the swelling resistance. Such resistance may not be permanent. High densities of bubbles on grain boundaries indicate a need for helium embrittlement tests

  4. Creep damage behaviour of modified 9Cr-1Mo steel weld joints

    International Nuclear Information System (INIS)

    Sakthivel, T.; Laha, K.; Vasudevan, M.; Panneer Selvi, S.

    2016-01-01

    Creep deformation and rupture behaviour of modified 9Cr-1Mo steel weld joints fabricated by single-pass activated TIG (A-TIG) and shielded metal arc welding (SMAW) processes have been investigated at 923 K over a stress range of 50 to 110 MPa after post weld heat treatment (PWHT). The weld joints exhibited significantly lower creep rupture lives than the base metal at lower applied stresses. Creep rupture location of the weld joints were found to occur in the ICHAZ. An extensive localized creep deformation, coarsening of M 23 C 6 precipitates in the ICHAZ with creep exposure led to the premature type IV failure of the joints. The coarsening of M 23 C 6 precipitates was extensive in the mid-section of the ICHAZ than the sub-surface of the joints, and was more predominant in the SMAW joint. While A-TIG weld joint exhibited reduced creep cavitation and coarsening of M 23 C 6 precipitates due to lower deformation constraints by adjacent regions in the ICHAZ. Hence, A-TIG weld joint exhibited higher creep rupture life than the SMAW joint. (author)

  5. Effect of welding thermal cycles on the structure and properties of simulated heat-affected zone areas in X10CrMoVNb9-1 (T91) steel at a state after 100,000 h of operation

    Energy Technology Data Exchange (ETDEWEB)

    Łomozik, Mirosław, E-mail: miroslaw.lomozik@is.gliwice.pl [Instytut Spawalnictwa, Testing of Materials Weldability and Welded Constructions Department, 44-100 Gliwice, Bł. Czesława 16-18 (Poland); Hernas, Adam, E-mail: adam.hernas@polsl.pl [Silesian University of Technology, Faculty of Materials Engineering and Metallurgy, 40-019 Katowice, Krasińskiego 8 str. (Poland); Zeman, Marian L., E-mail: marian.zeman@is.gliwice.pl [Instytut Spawalnictwa, Testing of Materials Weldability and Welded Constructions Department, 44-100 Gliwice, Bł. Czesława 16-18 (Poland)

    2015-06-18

    The article presents results of structural tests (light, scanning electron and scanning transmission electron microscopy) of X10CrMoVNb9-1 (T91) creep-resisting steel after approximately 100,000 h of operation. It was ascertained that the parent metal of T91 steel is characterized by the microstructure of tempered martensite with M{sub 23}C{sub 6} carbide precipitates and few dispersive precipitates of MX-type niobium and vanadium carbonitrides. The most inconvenient change in T91 steel precipitate morphology due to long-term operation is the appearance of the Laves Fe{sub 2}Mo phase which along with M{sub 23}C{sub 6} carbide particles forms elongated blocks and conglomerates on grain boundaries. The article also presents results of tests related to the effect of simulated welding thermal cycles on selected properties of X10CrMoVNb9-1 (T91) grade steel at a state after approximately 100,000 h of operation. The tests involved the determination of the chemical composition of the steel tested as well as impact tests, hardness measurements and microscopic metallographic examination (based on light microscopy) of simulated heat-affected zone (HAZ) areas for a cooling time (t{sub 8/5}) restricted within a range between 3 s and 120 s, with and without heat treatment. The tests revealed that, among other results, hardness values of simulated HAZ areas in X10CrMoVNb9-1 (T91) steel do not guarantee cold crack safety of the steel at the state without additional heat treatment. It was also observed that simulated welding thermal cycles of cooling times t{sub 8/5}=3, 12, 60 and 120 s do not significantly affect the toughness and hardness of simulated HAZ areas of the steel tested.

  6. Martensite shear phase reversion-induced nanograined/ultrafine-grained Fe-16Cr-10Ni alloy: The effect of interstitial alloying elements and degree of austenite stability on phase reversion

    Energy Technology Data Exchange (ETDEWEB)

    Misra, R.D.K., E-mail: dmisra@louisiana.edu [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Madison Hall Room 217, P.O. Box 44130, Lafayette, LA 70504-1430 (United States); Zhang, Z.; Venkatasurya, P.K.C. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Madison Hall Room 217, P.O. Box 44130, Lafayette, LA 70504-1430 (United States); Somani, M.C.; Karjalainen, L.P. [Department of Mechanical Engineering, University of Oulu, P.O. Box 4200, Oulu 90014 (Finland)

    2010-11-15

    Research highlights: {yields} Development of a novel process involving phase-reversion annealing process. {yields} Austensite stability strongly influences development of nanograined structure. {yields} Interstitial elements influence microstructural evolution during annealing. - Abstract: We describe here an electron microscopy study of microstructural evolution associated with martensitic shear phase reversion-induced nanograined/ultrafine-grained (NG/UFG) structure in an experimental Fe-16Cr-10Ni alloy with very low interstitial content. The primary objective is to understand and obtain fundamental insights on the influence of degree of austenite stability (Fe-16Cr-10Ni, 301LN, and 301 have different austenite stability index) and interstitial elements (carbon and nitrogen) in terms of phase reversion process, microstructural evolution during reversion annealing, and temperature-time annealing sequence. A relative comparison of Fe-16Cr-10Ni alloy with 301LN and 301 austenitic stainless steels indicated that phase reversion in Fe-16Cr-10Ni occurred by shear mechanism, which is similar to that observed for 301, but is different from the diffusional mechanism in 301LN steel. While the phase reversion in the experimental Fe-16Cr-10Ni alloy and 301 austenitic stainless steel occurred by shear mechanism, there were fundamental differences between these two alloys. The reversed strain-free austenite grains in Fe-16Cr-10Ni alloy were characterized by nearly same crystallographic orientation, where as in 301 steel there was evidence of break-up of martensite laths during reversion annealing resulting in several regions of misoriented austenite grains in 301 steel. Furthermore, a higher phase reversion annealing temperature range (800-900 deg. C) was required to obtain a fully NG/UFG structure of grain size 200-600 nm. The difference in the phase reversion and the temperature-time sequence in the three stages is explained in terms of Gibbs free energy change that

  7. Microstructure and Properties of the Interface Area in the Laser Cladded Ni Based Coatings on the 1Cr10Mo1NiWVNbN Steel

    Directory of Open Access Journals (Sweden)

    Yunxia Chen

    2017-05-01

    Full Text Available The Ni-based coatings were deposited on the 1Cr10Mo1NiWVNbN steel by using laser cladding process. The microstructure and properties of the coatings interface area were investigated by OM (Optical Microscopy, SEM (Scanning Electron Microscope, XRD (X-Ray Diffraction microhardness test and EDS (Energy Spectrum Analysis analysis. The results show that the bonding condition of the coatings interface is different in the monolayer and the trilayer. The monolayer coatings have a small dilution area. The dilution rate in a coating layer increases by layers. The scale of ferrite (α phase increases with the layer increases. The surface cladding quality of a monolayer is better than that of the trilayer coatings. The width of the interface increases with the increase of the layer. The width of the interface region in the trilayer coatings increases significantly. The microhardness of the interface zone is much higher than that in the coatings zone and the substrate zone. The microhardness of trilayer coatings is higher than that of the monolayer.

  8. Properties of the passive films on Ni-Cr-Mo alloys

    International Nuclear Information System (INIS)

    Lloyd, A.C.; Noel, J.J.; McIntyre, N.S.; Shoesmith, D.W.

    2003-01-01

    Ni-Cr-Mo alloys are among the most corrosion resistant materials known, showing exceptional localized corrosion resistance under extreme industrial conditions. Accordingly, one such alloy, Alloy-22. is a candidate material for the outer sheathing of nuclear waste packages for the Yucca Mountain repository. Nevada, USA. We briefly report our results on the passive behaviour for a series of Ni-Cr-Mo alloys, with the emphasis on determining if there is a temperature dependence associated with it. The change of passive corrosion rate with temperature is a critical parameter required for long-term performance assessment calculations. The results show that alloy C22 performed better than the other members of the C-series of alloys under acidic conditions. This indicates that its selection as a waste package material is appropriate, and that it possess the potential for long-term containment of radio-nuclides. (author)

  9. Reheat cracking in 1/2 CrMoV steel. Heat affected zones

    International Nuclear Information System (INIS)

    Batte, A.D.; Miller, R.C.; Murphy, M.C.

    1976-01-01

    Low alloy creep resisting steels are inherently susceptible to cracking during stress relief heat treatment (reheat cracking) though few welds give rise to problems in manufacture or service. Mechanical tests on simulated affected zone structures in CrMoV forgings have shown that cracking occurs when the high temperature ductility is inadequate to accommodate the residual welding strain. Differences in susceptibility result from differences in heat affected zone grain size if the purity level is sufficiently high; reheat cracking may then be avoided by ensuring complete grain refinement during welding. The susceptibility of a lower purity forging was insensitive to grain size; heat affected zone refinement is unlikely to eliminate cracking in such steel. (orig.) [de

  10. Low-activation Mn-Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

    Energy Technology Data Exchange (ETDEWEB)

    Onozuka, M.; Saida, T.; Hirai, S. [Mitsubishi Heavy Ind. Ltd., Yokohama (Japan); Kusuhashi, M.; Sato, I.; Hatakeyama, T. [The Japan Steel Works Ltd., Chatsu-machi 4, Muroran 051-8505 (Japan)

    1998-06-01

    Low-activation austenitic stainless steel based on Mn-Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn-Cr austenitic stainless steel, 24.5Mn-13.5Cr-0.02C-0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn-Cr steels. (orig.) 22 refs.

  11. Low-activation Mn Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

    Science.gov (United States)

    Onozuka, Masanori; Saida, Tomikane; Hirai, Shouzou; Kusuhashi, Mikio; Sato, Ikuo; Hatakeyama, Tsuyoshi

    1998-06-01

    Low-activation austenitic stainless steel based on Mn-Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn-Cr austenitic stainless steel, 24.5Mn-13.5Cr-0.02C-0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn-Cr steels.

  12. Fireside corrosion and steamside oxidation of 9-12% Cr martensitic steels exposed for long term testing

    DEFF Research Database (Denmark)

    Montgomery, Melanie; Jensen, S. A.; Rasmussen, F.

    2009-01-01

    MoV121 and HCM12 for the 12% Cr steels. The test tubes were welded in as part of the existing final superheaters in actual plants and exposure has been conducted over a ten year period (1994-2005). Compared to the older steel types, T92 and HCM12 utilise tungsten to improve their creep strength. From......To obtain long term corrosion and steam oxidation data for the 9-12%Cr ferritic steels, test tube sections have been exposed in Amager 3 and Avedore 1 coal fired power plants in Denmark (formerly run by ENERGI E2). Thus direct comparisons can be made for T91 and T92 for the 9% Cr steels and X20Cr...... Avedore I testing, T91 and T92 can be compared for exposure times up to similar to 48 000 h exposure. From Amager 3 testing, X20, HCM12 and T92 were tested; T92 has been exposed for up to 31 000 h and X20 and HCM12 have had 84 500 h exposure. Tube sections were removed for various exposure durations...

  13. Effect of cloric acid concentration on corrosion behavior of Ni/Cr coated on carbon steel

    Science.gov (United States)

    Desiati, Resetiana Dwi; Sugiarti, Eni; Thosin, K. A. Zaini

    2018-05-01

    Corrosion is one of the causes of metal degradation. Carbon steel (Fe) is easy to corrode in the extreme environment. Coating on carbon steel is required to improve corrosion resistance owing to protection or hindrance to extreme environmental conditions. In this present work, carbon steel was coated by electroplating techniques for nickel and pack cementation for chrome. The corrosion rate test was performed by Weight Loss method on FeNiCr, FeNi, FeCr and uncoated Fe as comparator which was dyed in 37% HCl and 25% HCl which had previously been measured dimension and mass. The immersion test result of FeNiCr and FeNi specimen were better than FeCr and uncoated Fe in terms of increasing corrosion resistance. The corrosion rate for 56 hours in 37% HCl for FeNiCr was 1.592 mm/y and FeNi was 3.208 mm/y, FeCr only lasted within 32 hours with corrosion rate was 6.494 mm/y. Surface of the sample after the corrosion test there was pitting, crevice corrosion and alloy cracking caused by chloride. The higher the concentration of HCl the faster the corrosion rate.

  14. Creep-fatigue behavior of 2 1/4Cr-1Mo steel at 5500C in air and vacuum

    International Nuclear Information System (INIS)

    Asayama, T.; Cheng, S.Z.; Asada, Y.; Mitsuhashi, S.; Tachibana, Y.

    1987-01-01

    Following studies on creep-fatigue behaviors of 304 steel at 650 0 C (Asada et al (1980) and Morishita et al (1984), (1985), (1987)), 2 1/4Cr-1Mo steel was studied on its creep-fatigue behaviors at 550 0 C in air and vacuum of 100 and 0.1 μPa. The present study intends to give a base for an evaluation of the environmental effect through obtaining a pure creep-fatigue behavior of this steel which is free from the environmental effect. In the previous studies on 304 steel, tests were conducted in three kinds of environment of air, 100 and 0.1 μPa vacuum. It seemed to be plausible that the 0.1 μPa vacuum shows the pure creep-fatigue behavior of 304 steel at 650 0 C which is almost completely free from the environment. A creep-fatigue life in 0.1 μPa vacuum is almost one order of magnitude higher than that in air. The 100 μPa vacuum suggested that the environmental effect of air still remains but is so small that a creep-fatigue life in 100 μPa is same to that in 0.1 μPa in some strain wave forms. The present study intends to examine if similar observations are obtained with 2 1/4Cr-1Mo steel at 550 0 C. This paper describes the analysis of the overstress and damages, in addition to a creep-fatigue result. (orig.GL)

  15. On the rational alloying of structural chromium-nickel steels

    International Nuclear Information System (INIS)

    Astaf'ev, A.A.

    1982-01-01

    A study was made on the influence of chromium nickel, phosphorus on the critical brittleness temperature of Cr-Ni-Mo-V structural steels. It is shown that the critical brittleness temperature of these steels increases at chromium content more over than 2% and nickel content more than 2% in the result of carbide transformations during tempering. Increase of nickel content in Cr-Ni-Mo-V-steels strengthens the tendency to embrittlement during slow cooling, from tempering temperature owing to development of process of phosphorus grain-boundary segregation. Two mentioned mechanisms of embrittlement determine principles of rational steel alloying. The extreme dependence of the critical brittleness temperature on chromium and nickel content, which enables to choose the optimum composition of Cr-Ni-Mo-V-steels, was established

  16. Influence of the Mo and W additions on the microstructure evolution and mechanical properties in Si-Cr spring steels

    International Nuclear Information System (INIS)

    Ban, Deok Young; Lee, Sang Lae; Nam, Won Jong

    1998-01-01

    Effects of the Mo and W additions to Si-Cr spring steels on the microstructural evolution and mechanical properties in spring steels were investigated. It was found that the Mo and/or W addition does not change the behavior of tempered carbide at low temperatures, such as the precipitation of ε-carbide and the conversion of ε-carbide to cementite, via dilatometry tests and the observation of microstructure using TEM. However, it would reduce the coarsening rate of cementite at high temperature above 450 .deg. C, resulting in the smaller size of cementite particles due to the lower diffusion rate. Since the sag resistance depends on the distribution and the size of precipitates, steel C(0.2% W) showed the strongest sag resistance whereas steel A showed the weakest sag resistance, when tempered at 450 .deg. C. Also, an abundance of precipitates at 350 deg. C tempering exhibits the maximum loop area, i.e., the sag resistance for all the tested steels. The Mo and W additions to Si-Cr spring steels raised the ratio of loop area/tensile strength. Therefore, the Mo and W additions would be effective method to increase the sag resistance as well as strength in Si-Cr spring steels

  17. Kinetics of phase transformations of undercooled austenite in 18CrNiMo7-6 steel applied for toothed wheels

    Directory of Open Access Journals (Sweden)

    J. Krawczyk

    2010-07-01

    Full Text Available Toothed wheels constitute essential part of the steel structural elements market. The most often hypereutectoid structural steels forcarburizing are used for toothed wheels. The final producers of toothed wheels are not demanding regarding a microstructure, providedthat the determined requirements will be fulfilled (e.g. metallurgical purity determined by ultrasounds. Therefore delivered forgings can be in an annealed or quenched state. This results from the situation that the final heat treatment or heat-chemical one is being done at one of the last stages of the toothed wheel production. An essential factor allowing to develop the proper heat treatment is the knowledge of the kinetics of phase transformations of undercooled austenite and its relating to technological conditions, being at the producer disposal, as well as to forging dimensions. Such investigations should be carried out on real melts used for forgings for toothed wheels production together with an analysis of microstructure changes on the forging cross-section. They should be based on calculation methods determining the distribution of cooling rates on its cross-section in dependence of an applied cooling medium.The mentioned above problems in relation to 18CrNiMo7-6 steel - are elucidated in this paper. The aim of the investigations wasthe description of the kinetics of phase transformations of undercooled austenite in this steel. The CCT diagram was constructed for the austenitizing temperature determined on the basis of phase transformations temperatures (the so-called critical points.

  18. Influence of chemical composition in crystallographic texture Fe-Cr-Mo alloys; Influencia da composicao quimica na textura cristalografica de ligas Fe-Cr-Mo

    Energy Technology Data Exchange (ETDEWEB)

    Moura, L.B.; Guimaraes, R.F. [Instituto Federal de Educacao, Ciencia e Tecnologia do Ceara, Fortaleza, CE (Brazil). Dept. da Industria; Abreu, H.F.G. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil)

    2010-07-01

    The use of steels with higher contents of Mo in the oil industry has been an alternative to reduce the effect of naphthenic corrosion in refining units. The addition of Mo in Fe-Cr alloys in the same manner that increases resistance to corrosion naphthenic causes some difficulties such as difficulty of forming, welding and embrittlement. In this work, experimental ingots of Fe-Cr-Mo alloys (Cr - 9, 15 and 17%, Mo - 5, 7 and 9%) were melted in vacuum induction furnace and hot and cold rolled in a laboratory rolling mill. The influence of chemical composition on crystallographic texture of samples subjected to the same thermo-mechanical treatment was analyzed by x-ray diffraction. The results indicate that fiber (111) becomes more intense with increasing Mo and/or Cr contents. (author)

  19. Structure change in 25 Cr - 20 Ni steels as a function of their Cr, Ni, Si and W content

    International Nuclear Information System (INIS)

    Gribaudo, L.M.; Durand, F.; Durand-Charre, M.

    1983-01-01

    The influence of varying the Cr, Ni, Si and W concentrations on the type and composition of the carbides of solidification and on the phase shift temperature is studied with 18 alloys of composition close to stainless steel-25-20 (AISI 310) composition. Experimental techniques used are differential thermal analysis, microprobe and scanning electron microscope. Crystallization is interpreted with the equilibrium diagram Ni-Cr-C. The formation of the interdendritic σ phase for a chromium rich alloys is interpreted with the phase equilibrium diagram of Fe-Ni-Cr-C. Mechanical properties and corrosion resistance are dependent on the morphology of the carbides M 7 C 3 and M 23 C 6 [fr

  20. Microstructure of laser cladded martensitic stainless steel

    CSIR Research Space (South Africa)

    Van Rooyen, C

    2006-08-01

    Full Text Available and martensite with 10% ferrite for Material B. Table 7 - Proposed martensitic stainless steel alloys for laser cladding Material C* Cr Ni Mn Si Mo Co Ms (ºC)* Cr eq Ni eq Material A 0.4 13 - 1 0.5 2.5 5.5 120 16.5 12.5 Material B 0.2 15 2 1 0.7 2.5 5.5 117... dilution, low heat input, less distortion, increased mechanical and corrosion properties excellent repeatability and control of process parameters. Solidification of laser cladded martensitic stainless steel is primarily austenitic. Microstructures...

  1. Study on elevated-temperature flow behavior of Ni-Cr-Mo-B ultra-heavy-plate steel via experiment and modelling

    Science.gov (United States)

    Gao, Zhi-yu; Kang, Yu; Li, Yan-shuai; Meng, Chao; Pan, Tao

    2018-04-01

    Elevated-temperature flow behavior of a novel Ni-Cr-Mo-B ultra-heavy-plate steel was investigated by conducting hot compressive deformation tests on a Gleeble-3800 thermo-mechanical simulator at a temperature range of 1123 K–1423 K with a strain rate range from 0.01 s‑1 to10 s‑1 and a height reduction of 70%. Based on the experimental results, classic strain-compensated Arrhenius-type, a new revised strain-compensated Arrhenius-type and classic modified Johnson-Cook constitutive models were developed for predicting the high-temperature deformation behavior of the steel. The predictability of these models were comparatively evaluated in terms of statistical parameters including correlation coefficient (R), average absolute relative error (AARE), average root mean square error (RMSE), normalized mean bias error (NMBE) and relative error. The statistical results indicate that the new revised strain-compensated Arrhenius-type model could give prediction of elevated-temperature flow stress for the steel accurately under the entire process conditions. However, the predicted values by the classic modified Johnson-Cook model could not agree well with the experimental values, and the classic strain-compensated Arrhenius-type model could track the deformation behavior more accurately compared with the modified Johnson-Cook model, but less accurately with the new revised strain-compensated Arrhenius-type model. In addition, reasons of differences in predictability of these models were discussed in detail.

  2. Cyclic and isothermal oxidation behavior of 2.25Cr-1Mo steel

    International Nuclear Information System (INIS)

    Proy, M.; Utrilla, M. v.; Otero, E.

    2014-01-01

    Cyclic and isothermal oxidation of chromium-molybdenum steel 2.25Cr-1Mo were analyzed at 550 degree centigrade and 650 degree centigrade during 360 hours in air atmospheres. The cycles were performed with two stages; one of heating in furnace during 90 minutes and then the sample were cooled to 50 degree centigrade by air flow. Thermogravimetric analyses were performed to obtain high temperature corrosion kinetics. Several characterization techniques have been used to identify the corrosion mechanism, as X-Ray Diffraction (XRD), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). Thermal cycling tests can changes the corrosion mechanism, due cracks propagation in oxide scale, that witch can favors the access of oxidant agent to the substrate. (Author)

  3. Formability of high-alloy dual-phase Cr-Ni steels

    International Nuclear Information System (INIS)

    Elfmark, J.

    2004-01-01

    The formability of dual-phase high-alloy Cr-Ni steel within the temperature range from 900 to 1250 C was studied using laboratory tensile and torsion tests. The dual-phase steels on 24% Cr basis are characterized by poor hot formability due to very low stable deformation values and slow recrystallization. Mathematical description of deformation stability exhaustion was derived, as well as a model of formability control based on analysis of the gradual diffuse deformation stability from the stability limit to the moment when the deformation starts to concentrate in a small volume of the test piece. Rolling simulation of dual-phase steel strip was used as an example demonstrating the draught scheme optimization technique which avoids the danger of crack occurrence during the rolling of dual-phase steel strip. (orig.)

  4. Fracture Resistances of Y_2O_3 Particle Dispersion Strengthened 9Cr Steel at Room Temperature and High Temperatures

    International Nuclear Information System (INIS)

    Yoon, Ji Hyun; Kang, Suk Hoon; Lee, Yongbok; Kim, Sung Soo

    2012-01-01

    The fracture resistance and tensile properties of Y_2O_3 oxide dispersion strengthened steel containing 9 wt% Cr (9Cr-ODS) were measured at various temperatures up to 700°C. The fracture characteristics were compared with those of commercial E911 ferritic/martensitic steel. The strength of 9Cr-ODS was at least 30% higher than that of E911 steel at the test temperatures below 500°C. The strength difference between the two materials was almost diminished at 700°C. 9Cr-ODS showed cleavage fracture behavior at room temperature and unstable crack growth behaviors at 300°C and 500°C. The J-R fracture resistance of 9Cr-ODS was much lower than that of E911 steel at all temperatures. It was deduced that the coarse Cr_2O_3 particles that were formed during the alloying process provided the crack initiation sites of cleavage fracture in 9Cr-ODS.

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

    International Nuclear Information System (INIS)

    Jung, Byong Ho; Ahn, Yong Sik

    1998-01-01

    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∼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 δ-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. Microstructure and tribological properties of NiMo/Mo2Ni3Si intermetallic 'in-situ' composites

    International Nuclear Information System (INIS)

    Gui Yongliang; Song Chunyan; Yang Li; Qin Xiaoling

    2011-01-01

    Research highlights: → Wear resistant NiMo/Mo 2 Ni 3 Si intermetallic 'in-situ' composites was fabricated successfully with Mo-Ni-Si powder blends as the starting materials. Microstructure of the NiMo/Mo 2 Ni 3 Si composites consists of Mo 2 Ni 3 Si primary dendrites, binary intermetallic phase NiMo and small amount of Ni/NiMo eutectics structure. The NiMo/Mo 2 Ni 3 Si composites exhibited high hardness and outstanding tribological properties under room-temperature dry-sliding wear test conditions which were attributed to the covalent-dominant strong atomic bonds and excellent combination of strength and ductility and toughness. - Abstract: Wear resistant NiMo/Mo 2 Ni 3 Si intermetallic 'in-situ' composites with a microstructure of ternary metal silicide Mo 2 Ni 3 Si primary dendritic, the long strip-like NiMo intermetallic phase, and a small amount of Ni/NiMo eutectics structure were designed and fabricated using molybdenum, nickel and silicon elemental powders. Friction and wear properties of NiMo/Mo 2 Ni 3 Si composites were evaluated under different contact load at room-temperature dry-sliding wear test conditions. Microstructure, worn surface morphologies and subsurface microstructure were characterized by OM, XRD, SEM and EDS. Results indicate that NiMo/Mo 2 Ni 3 Si composites have low fiction coefficient, excellent wear resistance and sluggish wear-load dependence. The dominant wear mechanisms of NiMo/Mo 2 Ni 3 Si composites are soft abrasion and slightly superficial oxidative wear.

  7. Corrosion and wear behavior of Ni60CuMoW coatings fabricated by combination of laser cladding and mechanical vibration processing

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hongxi, E-mail: piiiliuhx@sina.com [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Xu, Qian [Faculty of Adult Education, Kunming University of Science and Technology, Kunming 650051 (China); Wang, Chuanqi; Zhang, Xiaowei [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

    2015-02-05

    Highlights: • Ni60CuMoW coatings were fabricated by mechanical vibration assisted laser cladding hybrid process. • The maximum micro-hardness of the coating with mechanical vibration increases by 16%. • The mass loss and friction coefficient of the coating decreases by 17% and 16%, respectively. • The E{sub corr} positive shifts 1134.9 mV and i{sub corr} decreases by nearly one order of magnitude. • The ideal vibration parameters is vibration frequency 200 Hz and vibration amplitude 140 μm. - Abstract: Ni60CuMoW composite coatings were fabricated on 45 medium carbon steel using mechanical vibration assisted laser cladding surface modification processing. The microstructure, element distribution, phase composition, microhardness, wear and corrosion resistance of cladding coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), hardness tester, friction and wear apparatus and electrochemical workstation. The results indicate that the microstructure of M{sub 23}C{sub 6} (Cr{sub 23}C{sub 6} or (Fe, Ni){sub 23}C{sub 6}) carbide dispersion strengthening phase is uniformly distributed in eutectic (Ni, Fe) phase. The in-situ BCr and MoC compounds distribute in lamellar structure Fe{sub 3}B and dendrite Fe{sub 3}Ni{sub 3}Si, and some new W{sub 2}C phases also generated in Ni60CuMoW coating. In addition, the coarse dendrite has been replaced by some fine grain structure at the bonding interface. The fine grain hard phase makes the average microhardness of cladding coating increase from 720 to 835 HV{sub 0.5}. Under the condition of 200 Hz mechanical vibration frequency, the wear mass loss and friction coefficient of Ni60CuMoW coating are 7.6 mg and 0.068, 17% and 16% lower than the coating without mechanical vibration, respectively. The corrosion potential of cladding coating with mechanical vibration increases by 1134.9 mV and the corrosion current density decreases by nearly one order of

  8. Characteristics of Ni-Cr-Fe laser clad layers on EA4T steel

    Science.gov (United States)

    Chen, Wenjing; Chen, Hui; Wang, Yongjing; Li, Congchen; Wang, Xiaoli

    2017-07-01

    The Ni-Cr-Fe metal powder was deposited on EA4T steel by laser cladding technology. The microstructure and chemical composition of the cladding layer were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The bonding ability between the cladding layer and the matrix was measured. The results showed that the bonding between the cladding layer and the EA4T steel was metallurgical bonding. The microstructure of cladding layer was composed of planar crystals, columnar crystals and dendrite, which consisted of Cr2Ni3, γ phase, M23C6 and Ni3B phases. When the powder feeding speed reached 4 g/min, the upper bainite occurred in the heat affected zone (HAZ). Moreover, the tensile strength of the joint increased, while the yield strength and the ductility decreased.

  9. 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.

  10. Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

    Science.gov (United States)

    Reza, M. S.; Aqida, S. N.; Ismail, I.

    2016-06-01

    Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

  11. Fracture characteristic in creep of a 5 Cr-1/2 Mo steel at 600 and 6500C

    International Nuclear Information System (INIS)

    Paiva, R.L.C. de; Monteiro, S.N.; Silveira, T.L.

    The creep behavior of a 5 Cr-1/2 Mo steel was studied at 600 and 650 0 C. The caracteristics of fracture, observed by optical and scanning metallography, displayed a transition from intergranular to transgranular mode of rupture in the range of temperatures and stresses studied. This behavior was dicussed based upon the possible mechanisms for creep deformation taking place in this material [pt

  12. Dry sliding wear behavior and corrosion resistance of NiCrBSi coating deposited by activated combustion-high velocity air fuel spray process

    International Nuclear Information System (INIS)

    Liu, Shenglin; Zheng, Xueping; Geng, Gangqiang

    2010-01-01

    NiCrBSi is a Ni-based superalloy widely used to obtain high wear and corrosion resistant coatings. This Ni-based alloy coating has been deposited onto 0Cr13Ni5Mo stainless steel using the AC-HVAF technique. The structure and morphologies of the Ni-based coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). The wear resistance and corrosion resistance were studied. The tribological behaviors were evaluated using a HT-600 wear test rig. The wear resistance of the Ni-based coating was shown to be higher than that of the 0Cr13Ni5Mo stainless steel because Fe 3 B, with high hardness, was distributed in the coating so the dispersion strengthening in the Ni-based coating was obvious and this increased the wear resistance of the Ni-based coating in a dry sliding wear test. Under the same conditions, the worn volume of 0Cr13Ni5Mo stainless steel was 4.1 times greater than that of the Ni-based coating. The wear mechanism is mainly fatigue wear. A series of the electrochemical tests was carried out in a 3.5 wt.% NaCl solution in order to examine the corrosion behavior. The mechanisms for corrosion resistance are discussed.

  13. Electrochemical testing of passivity state and corrosion resistance of supermartensitic stainless steels

    Directory of Open Access Journals (Sweden)

    S. Lasek

    2010-01-01

    Full Text Available On low interstitial - supermartensitic stainless steels (X1CrNiMo 12-5-1, X2CrNiMo 13-6-2, X1CrNiMo 12-6-2 the electrochemical potentiodynamic polarization tests were carried out and the passive state stability and localized corrosion resistance were compared and evaluated. The effect of quenching and tempering as well as the changes in microstructure on polarisation curves and corrosion properties at room temperature were established. Small differences in chemical composition of steels were also registered on their corrosion parameters changes and resistance.

  14. Mechanical properties and microstructure changes of low-activation 3Cr-2W-V-Ti ferritic steels developed for nuclear applications

    International Nuclear Information System (INIS)

    Asakura, Kentaro; Kohyama, Akira; Yamada, Takemi.

    1990-01-01

    The effects of alloying elements such as Cr, W, V and Mn on tensile strength at elevated temperatures, creep-rupture properties and toughness of low activation (2.25-3)Cr-(2-2.5)W-V-Ti steels were investigated together with their microstructure change during high temperature exposure. These steels were normalized to produce bainitic structures in the same manner as that for a conventional 2.25Cr-1Mo steel. They presented superior tensile strength at elevated temperatures and creep-rupture strength in comparison with a conventional 2.25Cr-1Mo steel. The creep-rupture strength of the steels at 500degC for 100 000 h demonstrated about twice that of the conventional 2.25Cr-1Mo steel. The 3Cr-2.5W-0.2V-0.01Ti steel is recommended as a potential low activation ferritic steel for nuclear applications with well optimized mechanical properties, such as tensile strength at elevated temperatures, creep-rupture strength and toughness. The effects of alloying elements were discussed with correlating microstructural and mechanical aspects. (author)

  15. Role of butter layer in low-cycle fatigue behavior of modified 9Cr and CrMoV dissimilar rotor welded joint

    International Nuclear Information System (INIS)

    Wu, Qingjun; Lu, Fenggui; Cui, Haichao; Liu, Xia; Wang, Peng; Tang, Xinhua

    2014-01-01

    Highlights: • Modified 9Cr–CrMoV dissimilar turbine rotor was successfully welded by NG-SAW. • LCF properties of both welded joints were approximate at smaller strain amplitude. • Tempered martensite with amounts of carbides in HAZ contributed to weakest zones. • Matched BL determined LCF properties of whole joint for dissimilar welded rotor. - Abstract: The present work aims at studying the role of butter layer (BL) in low-cycle fatigue (LCF) behavior of modified 9Cr steel and CrMoV steel dissimilar welded joint. The significant difference of the chemical composition of base metals (BMs) makes it a challenge to achieve sound welded joint. Therefore, buttering was considered to obtain a transition layer between the dissimilar steels. The LCF tests of two kinds of specimens without and with butter layer were performed applying strain-controlled cyclic load with different axial strain amplitudes. The test results indicated that the number of cycles at higher strain amplitudes of welded joint without butter layer was greatly higher than that of the joint with butter layer, while the fatigue lifetime to crack initiation (2N f ) became closer to each other at low and middle strain amplitudes. The failure was in the tempered heat affected zone (HAZ) at the CrMoV side for specimens without BL, while the fracture occurred at the tempered HAZ in the BL for specimens with BL. The microstructure details of BM, BL, HAZ and weld metals (WMs) were revealed by optical microscopy (OM). It was found that the tempered martensite was major microstructure for welded joint and much more carbides were observed in tempered HAZ than other parts due to the repeated tempering. Microhardness test indicated a softest zone existing tempered HAZ of BL and also there was a softer zone in tempered HAZ at the CrMoV side due to repeated tempering during welding and post weld heat treatment (PWHT). And scanning electron microscopy (SEM) was applied to observe the fractography. It was

  16. Alloying and heat treatment optimization of Fe/Cr/C steels for improved mechanical properties

    International Nuclear Information System (INIS)

    Sarikaya, M.

    1979-06-01

    The effects of alloying elements and heat treatments on the microstructural changes and strength-toughness properties were investigated in optimization of vacuum melted Fe/Cr/C base steels. The structure of the steels in the as-quenched conditions consisted of highly dislocated autotempered lath martensite (strong phase) and thin continuous interlath films of retained austenite (tough phase). It has been emphasized again that the mechanical properties of the steels are sensitive to the amount and the stability of retained austenite. To increase the stability of retained austenite in the as-quenched condition 2 w/o Mn or 2 w/o Ni was added to the base steel, viz., Fe/3Cr/0.3C. Partial replacement of Cr by about 0.5 w/o Mo did not alter the beneficial microstructure

  17. Combined equilibrium and non-equilibrium phosphorus segregation to grain boundaries in a 2.25Cr1Mo steel

    International Nuclear Information System (INIS)

    Song, S.-H.; Shen, D.-D.; Yuan, Z.-X.; Liu, J.; Xu, T.-D.; Weng, L.-Q.

    2003-01-01

    Grain boundary segregation of phosphorus in a P-doped 2.25Cr1Mo steel during ageing at 540 deg. C after quenching from 980 deg. C is examined by Auger electron spectroscopy. The segregation is a combined effect of equilibrium segregation and non-equilibrium segregation. The effect of phosphorus non-equilibrium segregation is to enhance the kinetics of its equilibrium segregation

  18. Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Zieliński A.

    2016-06-01

    Full Text Available This paper presents the characteristics of the performance of P91 (X10CrMoVNb9-1, P92 (X10CrWMoVNb9-2 and VM12 (X12CrCoWVNb12-2-2 steels used for condition assessment of the pressure components of boilers with supercritical steam parameters. Studies on the mechanical properties, microstructure tests using scanning and transmission electron microscopy, and X-ray analysis of the phase composition of precipitates were performed for selected steels in the as-received condition and after long-term annealing. These steel characteristics are used for the evaluation of the microstructural changes and mechanical properties of the material of components after long-term service. The result of this study is the database of material characteristics representing the mechanical properties related to the microstructure analysis and it can be used for diagnosis of the components of pressure parts of power boilers.

  19. Correlation of Yield Stress And Microhardness in 08cr16ni11mo3 Irradiated To High Dose In The Bn-350 Fast Reactor

    International Nuclear Information System (INIS)

    Maksimkin, O.P.; Gusev, M.N.; Tivanova, O.S.; Silnaygina, N.S.; Garner, Francis A.

    2006-01-01

    The relationship between values of the microhardness and the engineering yield stress in steel 08Cr16Ni11Mo3 (Russian analog of AISI 316) heavily irradiated in the BN-350 reactor has been experimentally derived. It agrees very well with the previously published correlation developed by Toloczko for unirradiated 316 in a variety of cold-work conditions. Even more importantly, when the correlation is derived in the K δ format where the correlation involves changes in the two properties, we find excellent agreement with a universal K δ correlation developed by Busby and coworkers. With this K δ correlation, one can predict the value of yield stress in irradiated material based on measured values of microhardness. The technique is particularly suitable when the material of interest is in an inconvenient location or configuration, or when significant gradients in mechanical properties are anticipated over small dimensions. This approach makes it possible to reduce the labor input and risk when conducting such work. It appears that the derived correlation is equally applicable to both Russian and Western austenitic steel, and also in both irradiated and unirradiated conditions. Additionally, this report points out that microhardness measurements must take into account that high temperature sodium exposure alters the metal surface to produce ferrite, and therefore the altered layers should be removed prior to testing

  20. Comparison of low-cycle fatigue data of 2 1/4 % CrMo steels

    International Nuclear Information System (INIS)

    Sanderson, S.J.; Petrequin, P.; Nieuwland, H.C.D.; Breuer, H.J.

    1983-01-01

    Data files have been produced on international strain-controlled fatigue information available for 2 1/4 %CrMo steels. The available data have been considered generally in terms of total strain range vs. cycles to failure (Nsub(f)), tensile stress at Nsub(f)/2 vs. cycles to failure and time to failure vs. cycles to failure. Where possible the continuous cycling data been statistically analysed in terms of the elastic and plastic strain components and cycles to failure to yield best-fit equations over defined temperature (T) regime viz: T 0 C, 427 0 C 0 C and 550 0 C 0 C. Increasing test temperatures result in a progressive decrease in continuous cycling fatigue endurance and sustainable stress range

  1. The influence of interstitial impurities on temperature ranges of deuterium retention in austenitic stainless steel 18Cr10NiTi

    International Nuclear Information System (INIS)

    Neklyudov, I.M.; Morozov, O.M.; Kulish, V.G.; Zhurba, V.I.; Galytsky, A.G.; Piatenko, E.V.

    2009-01-01

    The influence of nitrogen, oxygen and helium on the temperature range of deuterium retention in 18Cr10NiTi stainless steel (of AISI304L type) has been investigated. It is demonstrated that the introduction of oxygen, nitrogen or helium into 18Cr10NiTi steel extends the upper limit in the high-temperature range of deuterium retention. It has been found that for 18Cr10NiTi stainless steel, pre-irradiated with helium ions, the increase in the temperature range of deuterium retention occurs in steps: on attainment of helium concentration of ∼0.5 at.% He the temperature range increases by ∼100 K, and on attainment of helium concentration of ∼2.5 at.% He the temperature range increases by ∼350 K. The introduction of oxygen into 18Cr10NiTi stainless steel results in the increase of the temperature range of deuterium retention in the direction of rise in temperature. In the deuterium thermodesorption spectrum, this manifests itself by the occurrence of an additional low-amplitude peak with the maximum temperature T m ∼ 560 K. The introduction of nitric impurity into 18Cr10NiTi stainless steel results in the extension of the temperature range of deuterium retention towards higher temperatures.

  2. Nitrogen-containing superlow-carbon austenitic steel 02Kh25N22AM2

    Science.gov (United States)

    Fe'ldgandler, É. G.; Svistunova, T. V.; Savkina, L. Ya.; Lapshina, O. B.

    1996-02-01

    At present the equipment for manufacturing carbamide mineral fertilizers is produced from domestic steel 03Kh17N14M3 having "carbamide quality." Imported equipment also used in the industry is produced from steel of the 25-22-2 (Cr -Ni-Mo) type shipped by various firms, namely, 2RE69 (Sandvik, Sweden), 254SFER (Avesta, Sweden), 2522LCN (VDM, Germany), DM 1.4466 (Germany), and X2CrNiMo 25-22-2 (Dalmine, Italy). The imported steels are used because in some units steel 03Khl7Nl4M3 does not provide the requisite corrosion resistance in an intensified process of carbamide manufacturing. We currently possess domestic high-alloyed steel for producing new and repairing imported equipment operating under the severe conditions of carbamide synthesis. The present paper concerns the structure, mechanical properties, and corrosion resistance of industrially produced steel 02Kh25N22AM2 (ChS-108) and the recommended range of its application.

  3. Fatigue Resistance of GX12CrMoVNbN9-1 Cast Steel after Ageing Process

    Directory of Open Access Journals (Sweden)

    Stanisław MROZIŃSKI

    2014-12-01

    Full Text Available In the present paper, low cycle fatigue behaviour of GX12CrMoVNbN9-1 (GP91 cast steel is presented. Fatigue tests were performed under isothermal conditions at room temperature and at 550 and 600oC, on five levels of total strain amplitude value ɛac = 0.25÷0.60%. The cast steel subject to investigation was in the as-received condition (after heat treatment and after 8000 hours of ageing at the temperature of 600oC. Performed research has shown an insignificant influence of the ageing process on mechanical properties of GP91 cast steel, determined with the static test of tension. Analysis of the performed tests has proved that GP91 cast steel in the as-received condition and after ageing process was characterized by strong cyclic softening without a clear period of stabilization of the hysteresis loop parameters. The fatigue lifetime curves at each temperature were obtained based on Basquin and Coffin – Manson equations. The process of ageing of GP91 cast steel contributed to a decrease in its fatigue life Nf from a few to a few dozen percent, and the level of fatigue life was dependent on the value of strain amplitude ɛac. It has also been stated that the fatigue life Nf of GP91 cast steel is determined by its plastic properties, and the degree of changes in fatigue life Nf was dependent not only on the temperature of testing, but also on the value of strain amplitude ɛac. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6077

  4. Influence of graphite-alloy interactions on corrosion of Ni-Mo-Cr alloy in molten fluorides

    Science.gov (United States)

    Ai, Hua; Hou, Juan; Ye, Xiang-Xi; Zeng, Chao Liu; Sun, Hua; Li, Xiaoyun; Yu, Guojun; Zhou, Xingtai; Wang, Jian-Qiang

    2018-05-01

    In this study, the effects of graphite-alloy interaction on corrosion of Ni-Mo-Cr alloy in molten FLiNaK salt were investigated. The corrosion tests of Ni-Mo-Cr alloys were conducted in graphite crucibles, to examine the differences of test specimens in conditions of electric contact and isolated with graphite, respectively. The corrosion attack is severer with more weight loss and deeper Cr depletion layer in samples electric contact with graphite than those isolated with graphite. The occurrence of galvanic corrosion between alloy specimens and graphite container was confirmed by electrochemical measurement. The corrosion is controlled by nonelectric transfer in isolated test while electrochemical reaction accelerated corrosion in electric contact test.

  5. Measurement of high temperature elastic moduli of an 18Cr-9Ni-2.95 Cu-0.58 Nb-0.1C (Wt %) austenitic stainless steel

    Science.gov (United States)

    Tripathy, Haraprasanna; Hajra, Raj Narayan; Sudha, C.; Raju, S.; Saibaba, Saroja

    2018-04-01

    The Young's modulus (E) and Shear modulus (G) of an indigenously developed 18Cr-9Ni-0.1C-2.95 Cu-0.58Nb (wt %) austenitic stainless steel has been evaluated in the temperature range 298 K to 1273 K (25 °C to 1000 °C), using Impulse excitation technique (IET). The Bulk modulus (K) and the poison's ratio have been estimated from the measured values of E and G. It is observed that the elastic constants (E, G and K) are found to decrease in a nonlinear fashion with increase in temperature. The Cu precipitation is found to influence the elastic moduli of the steel in the cooling cycle. The observed elastic moduli are fitted to 3rd order polynomial equations in order to describe the temperature dependence of E, G, K moduli in the temperature range 298-1273 K (25 °C to 1000 °C). The room temperature values of E,G and K moduli is found to be 207, 82 and 145 GPa respectively for the present steel.

  6. High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

    Science.gov (United States)

    Bhatia, Rakesh; Sidhu, Hazoor Singh; Sidhu, Buta Singh

    2015-03-01

    Erosion-corrosion is a serious problem observed in steam-powered electricity generation plants, and industrial waste incinerators. In the present study, four compositions of Cr3C2-(Ni-20Cr) alloy coating powder were deposited by high-velocity oxy-fuel spray technique on T-91 boiler tube steel. The cyclic studies were performed in a coal-fired boiler at 1123 K ± 10 K (850 °C ± 10 °C). X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis and elemental mapping analysis techniques were used to analyze the corrosion products. All the coatings deposited on T-91 boiler tube steel imparted hot corrosion resistance. The 65 pctCr3C2 -35 pct (Ni-20Cr)-coated T-91 steel sample performed better than all other coated samples in the given environment.

  7. Systematic study of formation of soft and hard zones in the dissimilar weldments of Cr-Mo steels

    International Nuclear Information System (INIS)

    Sudha, C.; Terrance, A.L.E.; Albert, S.K.; Vijayalakshmi, M.

    2002-01-01

    The microstructural stability and elemental redistribution in dissimilar weldments between 9Cr-1Mo and 2.25Cr-1Mo ferritic steels during various postweld heat treatments (PWHTs) have been studied using microscopy techniques ranging from optical to transmission electron microscopy and electron probe microanalyser. Application of PWHT at 1023 K for various times resulted in the formation of a soft zone in the low Cr side and a carbide rich hard zone adjoining the soft zone in the high Cr side of the weldment. The width of these zones and their hardness are influenced by the time of exposure at elevated temperature. A measurable increase in the width and a decrease in the hardness of the soft and hard zones with aging times are observed. Correlation between these observed effects and the elemental redistribution responsible for the formation of these zones is being attempted. Micromechanisms responsible for the formation of these zones are proposed. Migration of carbon from low Cr side to high Cr side driven by the gradient in the carbon activity has been found to be responsible for the formation of these zones

  8. Chemical reactions during sintering of Fe-Cr-Mn-Si-Ni-Mo-C-steels with special reference to processing in semi-closed containers

    Directory of Open Access Journals (Sweden)

    Cias A.

    2015-01-01

    Full Text Available Sintering of Cr, Mn and Si bearing steels has recently attracted both experimental and theoretical attention and processing in semiclosed containers has been reproposed. This paper brings together relevant thermodynamic data and considers the kinetics of some relevant chemical reactions. These involve iron and carbon, water vapour, carbon monoxide and dioxide, hydrogen and nitrogen of the sintering atmospheres and the alloying elements Cr, Mn, Mo and Si. The paper concludes by presenting mechanical properties data for three steels sintered in local microatmosphere with nitrogen, hydrogen, nitrogen-5% hydrogen and air as the furnace gas.

  9. On mechanism of austenite chromium-nickel-molybdenum steels intercrystalline corrosion in weak and strong oxidizing media

    International Nuclear Information System (INIS)

    Plaskeev, A.V.; Savkina, L.Ya.; Knyazheva, V.M.; Kolotyrkin, Ya.M.; Fil'dgandler, Eh.G.; Rodin, N.N.

    1975-01-01

    Wide possibilities γ-spectrometry for kinetic investigation of intercrystalline corrosion (ICC) and also for recognizing the nature of the selectively soluble structural components at the stages of their initiation and development has been determined using 00Cr16Ni15Mo steel, containing 0,05 and 0,03%C. It is shown by γ-spectrometry, autoradiography, electrochemistry, optical and electron metallography in combination with (Cr,Fe,Mo) 23 C 6 carbide properties investigation, that ICC of sensitized 00Cr16Ni15Mo3 steel, is determined by selective dissolution of chromium and molybdenum depleted boundary regions of solid solutions. At potentials of passivation region (imitation of D method) the main cause of ICC is the selective dissolution of (Cr;Fe;Mo) 23 C 6 carbides arranged at grain boundaries. This process is facilitated in the presence of molybdenum in carbide

  10. Wastage-resistant characteristics of 12Cr steel tube material. Small leak sodium-water reaction test

    International Nuclear Information System (INIS)

    Shimoyama, Kazuhito

    2004-03-01

    In the water leak accident of a steam generator designed for a sodium cooled reactor in the Feasibility Study, the localization of tube failure propagation by using an advanced water leak detector will be required from the viewpoints of the safety and economical efficiency of the plant. So far, the conventional knowledge and analytical tools have been used in the investigation and evaluation of water leak phenomenon; nevertheless, there was neither test data nor the study of quantitative evaluation on the corrosion behavior, so-called wastage-resistant characteristics, of 12Cr steel tube material in sodium-water reactions. Wastage tests for the 12Cr steel tube material were conducted in small water leaks by use of the Sodium-Water Reaction Test Rig (SWAT-1R), and the data of wastage rate were obtained in the parameter of water leak rate under the constant sodium temperature and distance between leak and target tubes. The test results lead to the following conclusions: (1) The wastage-resistibility of 12Cr steel is 1.6 times greater than that of 9Cr steel and is 2.7 times greater than that of 2.25Cr-1Mo steel. (2)The wastage-resistibility of 12Cr steel increases in smaller water leaks; especially in water leak rates of 1 g/sec or less, it is more excellent than that of SUS321 stainless steel used as Monju superheater tube material. (3) Based on the correlation of wastage rate for the 9Cr steel, the correlation for the 12Cr steel has been obtained to be used for the evaluation of tube failure propagation. As the correlation of wastage rate for the 12Cr steel is based on the correlation for the 9Cr steel, it gives enough conservatism in smaller water leaks. To serve in accurately evaluating the tube failure propagation in smaller water leaks, it is necessary to obtain new correlation of wastage rate for the 12Cr steel based on the data in the wide range of water leak rates. (author)

  11. Effect of Mo/B atomic ratio on the properties of Mo2NiB2-based cermets

    International Nuclear Information System (INIS)

    Xie, Lang; Li, XiaoBo; Zhang, Dan; Yi, Li; Gao, XiaoQing; Xiangtan Univ.

    2015-01-01

    Using three elementary substances, Mo, Ni, and amorphous B as raw materials, four series of Mo 2 NiB 2 -based cermets with the Mo/B atomic ratio ranging from 0.9 to 1.2 were successfully prepared via reaction sintering. The effect of Mo/B atomic ratio on the microstructure and properties was studied for the cermets. The results indicate that there is a strong correlation between the Mo/B atomic ratio and properties. The transverse rupture strength of the cermets increases with an increase in Mo/B ratio and shows a maximum value of 1 872 MPa at an Mo/B atomic ratio of 1.1 and then decreases with increasing Mo/B atomic ratio. The hardness and the corrosion resistance of the cermets increase monotonically with an increase in Mo/B atomic ratio. In Mo-rich cermets with an atomic ratio of Mo/B above 1.1, a small amount Ni-Mo intermetallic compound is found precipitated at the interface of Mo 2 NiB 2 grains.

  12. Influence of chemical composition in crystallographic texture Fe-Cr-Mo alloys

    International Nuclear Information System (INIS)

    Moura, L.B.; Guimaraes, R.F.

    2010-01-01

    The use of steels with higher contents of Mo in the oil industry has been an alternative to reduce the effect of naphthenic corrosion in refining units. The addition of Mo in Fe-Cr alloys in the same manner that increases resistance to corrosion naphthenic causes some difficulties such as difficulty of forming, welding and embrittlement. In this work, experimental ingots of Fe-Cr-Mo alloys (Cr - 9, 15 and 17%, Mo - 5, 7 and 9%) were melted in vacuum induction furnace and hot and cold rolled in a laboratory rolling mill. The influence of chemical composition on crystallographic texture of samples subjected to the same thermo-mechanical treatment was analyzed by x-ray diffraction. The results indicate that fiber (111) becomes more intense with increasing Mo and/or Cr contents. (author)

  13. Results obtained so far with the production of turbine and valve casings made of the new 9% Cr cast steel types G-X 12 CrMoWVNbN 10 11 and G-X 12 CrMoVNbN 91; Erfahrungsbericht ueber die Herstellung von Turbinen- und Ventilgehaeusen aus den neuen 9% Cr-Stahlgusssorten G-X 12 CrMoWVNbN 10 1 1 und G-X 12 CrMoVNbN 91

    Energy Technology Data Exchange (ETDEWEB)

    Schuster, F.; Buberl, A.; Hanus, R. [VOEST-ALPINE STAHL LINZ GmbH, Linz (Austria); Cerjak, H. [Technische Univ., Graz (Austria)

    1996-12-31

    In the course of production start-up of new 9-10% Cr cast steel types, and application of R and D results to practice, the following examinations and modifications have been performed: 1. Reduction of average chromium content from 10.5 to 9.5% in order to suppress delta ferrite segregation, and adjustment of austenite and ferrite stabilizing alloying constituents. 2. Analysis of typical defects in castings, and modification of casting and feeding techniques in compliance with the saturation behaviour of the new 9-10% Cr steels. These measures achieved a reduction of feeding-based flaws (shrinkage) in the last few cast pieces. 3. The good weldability was proven of the new 9-10% Cr steels by means of welding tests and crack-free production and construction welds made in cast pieces. (orig./MM) [Deutsch] Im Zuge der Produktionsaufnahme neuer 9-10% Cr-Stahlgusssorten und der Ueberleitung der F and E Ergebnisse in die betriebliche Praxis wurden folgende Untersuchungen und Anpassungen vorgenommen: 1. Um die Deltaferritausscheidung zu unterdruecken, wurde der mittlere Chromgehalt von 10,5 auf 9,5% abgesenkt und die austenit- und ferritstabilisierenden Legierungselemente besser angepasst. 2. Die Analyse typischer Fehlererscheinungen an Gussstuecken machten eine Anpassung der Giess- und Speisungstechnik an das Saettigungsverhalten der neuen 9-10% Cr-Staehle erforderlich. Diese Massnahmen fuehrten zu einer Verringerung der Speisungsfehler (Lunker) bei den zuletzt abgegossenen Gussstuecken. 3. Bei Schweissversuchen und an Gussstuecken rissfrei ausgefuehrten Fertigungs- und Konstruktionsschweissungen konnte die gute Schweisseignung der neuen 9-10% Cr-Staehle nachgewiesen werden. (orig./MM)

  14. Microstructure of HFIR-irradiated 12-Cr 1 MoVW ferritic steel

    International Nuclear Information System (INIS)

    Vitek, J.M.; Klueh, R.L.

    1983-01-01

    As part of the fusion materials development program in the United States, a 12 Cr-1 MoVW ferritic steel was irradiated in the High Flux Isotope Reactor (HFIR) to a damage level of 36 dpa at 300, 400, 500, and 600 0 C. During irradiation in HFIR, a transmutation reaction of nickel results in the production of helium, to a level of 99 at. ppM in the present experiment. The microstructures were evaluated after irradiation and the results are presented. Cavities were found at all temperatures. Small cavities (3 to 9 nm) were observed after irradiation at 300, 500 and 600 0 C. At 500 and 600 0 C, the cavities were found preferentially at dislocations, lath boundaries, and prior austenite grain boundaries. After irradiation at 400 0 C, larger cavities (4 to 30 nm) were observed homogeneously distributed throughout the tempered martensite structure. The maximum swelling was 0.07% after irradiation at 400 0 C. Comparision of the results with other studies in which helium was not present at such high levels indicated helium enhances the swelling of 12 Cr-1 MoVW

  15. Determination of chemical activities of Fe, Cr, Ni and Mn in stainless steel 316 by Knudsen effusion cell mass spectrometry

    International Nuclear Information System (INIS)

    Venugopal, V.; Kulkarni, S.G.; Subbanna, C.S.; Sood, D.D.

    1995-01-01

    Cold-worked austenitic stainless steel of the type AISI 316 is being used as the cladding and wrapper materials in fast reactor fuel pins. Knowledge of the thermodynamic activities of the steel constituents is necessary to predict the possibility of fuel-cladding, coolant-cladding or fission product-cladding chemical reactions. The thermodynamic activities of Fe, Cr, Ni and Mn for stainless steel 316 were determined by measuring their partial pressures in the temperature range 1293-2120 K, using Knudsen effusion cell mass spectrometry. High purity Ag was used as an internal calibrant. The chemical activities of Fe (a Fe ), Cr (a Cr ), Ni (a Ni ) and Mn (a Mn ) were evaluated using literature data for the vapour pressures of pure metals. log a Fe ±0.18=-1.586+2074/T (T=1293-1872 K)log a Cr ±0.30=-2.350+2612/T (T=1293-2120 K)log a Ni ±0.20=-2.140+1794/T (T=1468-1974 K)log a Mn ±0.23=-2.041-5478/T (T=1302-1894 K) ((orig.))

  16. Stress corrosion cracking in 3,5 NiCrMoV steel in a 403 K potential-PH diagram

    International Nuclear Information System (INIS)

    Hitomi, Itoh; Takashi, Momoo

    2001-01-01

    3,5 NiCrMoV steel is used in low-pressure turbine rotors and discs. It has been pointed out that intergranular stress corrosion cracking may occur in this material in the wet region at temperatures of about 400 K. Accordingly, the authors focused on the environmental conditions under which stress corrosion cracking (SCC) occurs. A potential-pH diagram was used to investigate the region in which SCC occurs in the high strength materials that are particularly susceptible to SCC. The investigation found that SCC is initiated in this material not only in the high caustic region but in the neutral region as well. The investigation also found that initiation and propagation were accelerated in dissolved oxygen environments with increased chemical potential in the neutral region. Since careful observation of the starting point of cracks has shown that corrosion pits trigger SCC, subsequent immersion tests under constant potential were conducted. The results showed that corrosion pits are generated at the high potential range. These results led to the development of an acceleration test environment for laboratory to determine the susceptibility of SCC in field turbine disc and rotor materials. (author)

  17. A New Method to Produce Ni-Cr Ferroalloy Used for Stainless Steel Production

    Science.gov (United States)

    Chen, Pei-Xian; Chu, Shao-Jun; Zhang, Guo-Hua

    2016-08-01

    A new electrosilicothermic method has been proposed in the present paper to produce Ni-Cr ferroalloy, which can be used for the production of 300 series stainless steel. Based on this new process, the Ni-Si ferroalloy is first produced as the intermediate alloy, and then the desiliconization process of Ni-Si ferroalloy melt with chromium concentrate is carried out to generate Ni-Cr ferroalloy. The silicon content in the Ni-Si ferroalloy produced in the submerged arc furnace should be more than 15 mass% (for the propose of reducing dephosphorization), in order to make sure the phosphorus content in the subsequently produced Ni-Cr ferroalloy is less than 0.03 mass%. A high utilization ratio of Si and a high recovery ratio of Cr can be obtained after the desiliconization reaction between Ni-Si ferroalloy and chromium concentrate in the electric arc furnace (EAF)-shaking ladle (SL) process.

  18. Microstructure refinement and strengthening mechanisms of a 9Cr oxide dispersion strengthened steel by zirconium addition

    International Nuclear Information System (INIS)

    Xu, Hai Jian; Lu, Zheng; Wang, Dong Mei; Liu, Chunming

    2017-01-01

    To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of Fe-9Cr-2W-0.3Y_2O-3 and Fe-9Cr-2W-0.3Zr-0.3Y_2O_3 were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal δ-phase Y_4Zr_3O_1_2 oxides and body-centered cubic Y_2O_3 oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of Y_4Zr_3O_1_2 particles is much smaller than that of Y_2O_3. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is 1.1 x 10"2"3/m"3 with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time

  19. Nitrogen effect on the tendency of Cr-Ni-MN steels to delayed fracture under stress and hydrogen effects

    International Nuclear Information System (INIS)

    Suvorova, S.O.; Fillipov, G.A.

    1996-01-01

    Austenitic steels types 03Kh17N16G10AM5, 03Kh6N12G10AM5 and 07Kh13AG20 with various nitrogen contents were studied for their tendency to delayed fracture using mechanical tests, fractography and X ray diffraction analysis. The steel type 07Kh13G20 exhibited the highest strength in the initial state but showed an increase tendency to delayed fracture after hydrogenation. It is underlined that nitrogen additions essentially intensify the tendency of cold worked steels to delayed fracture. This fact should be taken into account when using nitrogen-containing Cr-Ni-Mn steels under severe operational conditions. 4 refs., 2 tabs

  20. Cladding nuclear steels - the application of plasma-arc hot wire surfacing

    International Nuclear Information System (INIS)

    Trarbach, K.O.

    1981-01-01

    The effect of one and two layer plasma-arc hot wire cladding on the HAZ microstructure of the fine grained structural steel 22 NiMoCr 3 7, which is similar to ASTM A 508, class 2, and steel 20 MnMoNi 5 5, similar to ASTM A 533, grade B, class 1 is determined. Attention is directed particularly to the behaviour of the susceptible region, and the consumables considered are cladding materials X 2 CrNiNb 19 9, similar to ER 347 Elc, and S-NiCr 20 Nb, similar to ER NiCr-3 (Inconel 82). Results of corrosion resistance tests show that this cladding technique can be recommended for manufacture of equipment for the chemical industry to avoid corrosion failure. Plasma-arc hot wire surfacing is also shown to be capable of depositing single or double clad layers to meet the highest safety requirements and could be applied to nuclear power plants for the special manufacture of wear resistant parts and for protection of equipment subject to a variety of corrosive environments. (U.K.)

  1. Impact properties of 2 1/4 Cr--1 Mo steel after ten years EBR-II service

    International Nuclear Information System (INIS)

    Shields, J.A.; Server, W.L.; Sheckherd, J.W.; Longua, K.J.

    1976-01-01

    The material studied in this investigation was obtained from a 2 1 / 4 Cr--1 Mo steel superheated steam line which had been in service for approximately 90,000 hours. Of that 90,000 hours, approximately 40,000 hours were at a temperature of approximately 820 0 F and a pressure of 1250 psi, and 35,000 hours were at a temperature of 500 0 F and 1250 psi. The results of optical metallography and instrumented impact testing performed on the materials are presented

  2. Hot cracking of welded joints of the 7CrMoVTiB 10-10 (T/P24) steel

    Energy Technology Data Exchange (ETDEWEB)

    Adamiec, J, E-mail: janusz.adamiec@polsl.pl [Department of Materials Science, Silesian University of Technology, Krasinskiego 8, 40-019 Katowice (Poland)

    2011-05-15

    Bainitic steel 7CrMoVTiB10-10 is one the newest steels for waterwalls of modern industrial boilers. In Europe, attempts have been made to make butt welded joints of pipes made of this steel of the diameter up to 51 mm and thickness up to 8 mm. Many cracks have been observed in the welded joint, both during welding and transport and storage. The reasons of cracking and the prevention methods have not been investigated. No comprehensive research is carried out in Europe in order to automate the welding process of the industrial boiler elements made of modern bainitic steel, such as 7CrMoVTiB10-10. There is no information about its overall, operative and local weldability, influence of heat treatment, as well as about resistance of the joints to cracking during welding and use. The paper presents experience of Energoinstal SA from development of technology and production of waterwalls of boilers made of the 7CrMoVTiB 10-10 steel on a multi-head automatic welder for submerged arc welding.

  3. Dissolution and oxidation behaviour of various austenitic steels and Ni rich alloys in lead-bismuth eutectic at 520 °C

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Marion, E-mail: marion.roy@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Martinelli, Laure, E-mail: laure.martinelli@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Ginestar, Kevin, E-mail: kevin.ginestar@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Favergeon, Jérôme, E-mail: jerome.favergeon@utc.fr [Laboratoire Roberval, UMR 7337, Université de Technologie de Compiègne, Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex (France); Moulin, Gérard [Laboratoire Roberval, UMR 7337, Université de Technologie de Compiègne, Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex (France)

    2016-01-15

    Ten austenitic steels and Ni rich alloys were tested in static lead-bismuth eutectic (LBE) at 520 °C in order to obtain a selection of austenitic steels having promising corrosion behaviour in LBE. A test of 1850 h was carried out with a dissolved oxygen concentration between 10{sup −9} and 5 10{sup −4} g kg{sup −1}. The combination of thermodynamic of the studied system and literature results leads to the determination of an expression of the dissolved oxygen content in LBE as a function of temperature: RT(K)ln[O](wt%) = −57584/T(K) −55.876T(K) + 254546 (R is the gas constant in J mol{sup −1} K{sup −1}). This relation can be considered as a threshold of oxygen content above which only oxidation is observed on the AISI 316L and AISI 304L austenitic alloys in static LBE between 400 °C and 600 °C. The oxygen content during the test leads to both dissolution and oxidation of the samples during the first 190 h and leads to pure oxidation for the rest of the test. Results of mixed oxidation and dissolution test showed that only four types of corrosion behaviour were observed: usual austenitic steels and Ni rich alloys behaviour including the reference alloy 17Cr-12Ni-2.5Mo (AISI 316LN), the 20Cr-31Ni alloy one, the Si containing alloy one and the Al containing alloy one. According to the proposed criteria of oxidation and dissolution kinetics, silicon rich alloys and aluminum rich alloy presented a promising corrosion behaviour. - Highlights: • 10 austenitic steels and Ni rich alloys were tested in LBE at 520 °C with dissolved oxygen content between 10{sup -9} and 5 10{sup -4} wt%. • It is shown that only thermodynamics cannot explain the Ni rich alloys corrosion behaviour in LBE. • The role of oxygen on corrosion behaviour in LBE was highlighted. • An equilibrium line was defined above which only oxidation has occurred on 316L: RTln[O](wt%) = -57584/T(K)-55.876T(K)+254546. • 18Cr-15Ni-3.7Si, 21Cr-11Ni-1.6Si and 14Cr-25Ni-3.5Al

  4. Estimation of the Temperature-Dependent Nitrogen Solubility in Stainless Fe-Cr-Mn-Ni-Si-C Steel Melts During Processing

    Science.gov (United States)

    Wendler, Marco; Hauser, Michael; Sandig, Eckhard Frank; Volkova, Olena

    2018-04-01

    The influence of chemical composition, temperature, and pressure on the nitrogen solubility of various high alloy stainless steel grades, namely Fe-14Cr-(0.17-7.77)Mn-6Ni-0.5Si-0.03C [wt pct], Fe-15Cr-3Mn-4Ni-0.5Si-0.1C [wt pct], and Fe-19Cr-3Mn-4Ni-0.5Si-0.15C [wt pct], was studied in the melt. The temperature-dependent N-solubility was determined using an empirical approach proposed by Wada and Pehlke. The thus calculated N-concentrations overestimate the actual N-solubility of all the studied Fe-Cr-Mn-Ni-Si-C steel melts at a given temperature and pressure. Consequently, the calculation model has to be modified by Si and C because both elements are not recognized in the original equation. The addition of the 1st and 2nd order interaction parameters for Si and C to the model by Wada and Pehlke allows a precise estimation of the temperature-dependent nitrogen solubility in the liquid steel bath, and fits very well with the measured nitrogen concentrations during processing of the steels. Moreover, the N-solubility enhancing effect of Cr- and Mn-additions has been demonstrated.

  5. Recovery and Precipitate Analysis of 9 Pct Cr-1 Pct MoVNb Steel during Creep

    NARCIS (Netherlands)

    Kabadwal, A.; Tamura, M.; Shinozuka, K.; Esaka, H.

    The effect of tempering temperature and creep exposure on the microstructure of a modified 9Cr steel was investigated. Creep-interrupted specimens, including the grip portion, were investigated precisely using mainly X-ray and inductively coupled plasma (ICP) spectroscopy. After saturation of

  6. Effect of Cooling Rate on Microstructures and Mechanical Properties in SA508 Gr4N High Strength Low Alloy Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Minchul; Park, Sanggyu; Choi, Kwonjae; Lee, Bongsang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    The microstructure of Ni-Cr-Mo low alloy steel is a mixture of tempered martensite and tempered lower bainite and that of Mn-Mo-Ni low alloy steel is predominantly tempered upper bainite. Higher strength and toughness steels are very attractive as an eligible RPV steel, so several researchers have studied to use the Ni-Cr-Mo low alloy steel for the NPP application. Because of the thickness of reactor vessel, there are large differences in austenitizing cooling rates between the surface and the center locations of thickness in RPV. Because the cooling rates after austenitization determine the microstructure, it would affect the mechanical properties in Ni-Cr-Mo low alloy steel, and it may lead to inhomogeneous characteristics when the commercial scale of RPV is fabricated. In order to apply the Ni-Cr-Mo low alloy steel to RPV, it is necessary to evaluate the changes of microstructure and mechanical properties with varying phase fractions in Ni-Cr-Mo low alloy steel. In this study, the effects of martensite and bainite fractions on mechanical properties in Ni-Cr-Mo low alloy steel were examined by controlling the cooling rate after austenitization. First of all, continuous cooling transformation(CCT) diagram was established from the dilatometric analyses. Then, the phase fractions at each cooling rate were quantitatively evaluated. Finally, the mechanical properties were correlated with the phase fraction, especially fraction of martensite in Ni-Cr-Mo low alloy steel.

  7. Effect of microstructure on the cleavage fracture strength of low carbon Mn-Ni-Mo bainitic steels

    International Nuclear Information System (INIS)

    Im, Young-Roc; Lee, Byeong-Joo; Oh, Yong Jun; Hong, Jun Hwa; Lee, Hu-Chul

    2004-01-01

    The effects of the microstructure on the cleavage fracture strength of low carbon Mn-Ni-Mo bainitic steels were examined. A four-point bend test and double-notched bend specimens were used to measure the cleavage fracture strength of the alloys and identify the cleavage initiating micro-cracks, respectively. The cleavage fracture strength and DBTT of Mn-Ni-Mo bainitic steels were strongly affected by the alloy carbon content. The decrease in the alloy carbon content resulted in a decrease in the inter-lath cementite-crowded layers and higher cleavage fracture strength. Micro-cracks that formed across the inter-lath cementite-crowded layers were observed to initiate cleavage fracture. The width of these inter-lath cementite-crowded layers was accepted as a cleavage initiating micro-crack size in the micro-mechanical modeling of the cleavage fracture, and the measured cleavage strength values of the bainitic Mn-Ni-Mo steels were well represented by the modified Griffith relationship

  8. Properties of welded joints of 2,25Cr-1Mo steel with various carbon content

    International Nuclear Information System (INIS)

    Vornovitskij, I.N.; Brodetskaya, E.Z.; Pozdnyakova, A.S.

    1980-01-01

    Properties of welded joints of 2,25 Cr - 1 Mo steel pipelines with different carbon content are considered. It is shown that application of electrodes developed in some countries for welding permits in many cases to exclude heat treatment of welded joints owing to high ductility of weld deposited metal. To improve the ductility, it is necessary to limit both carbon content down to 0,03-0,06% and detrimental elements (sulfur, phosphorus). Heat affected zone hardness may be increased at the expense of carbon. Weld deposited metal possesses the highest long-term strength at the given test temperature; in this case long-term strength of welded joints and base metal is practically the same. The long-term strength of high-carbon steel is higher at the test temperature of 565 deg C as compared to mean-carbon and low-carbon steels, whose long-term strength is practically equal at this temperature. The long-term strength of high-carbon and mean-carbon steels is practically the same and higher as compared with low-carbon one at the test temperature of 510 deg C

  9. Application of long-range ordering in the synthesis of a nanoscale Ni2 (Cr,Mo) superlattice with high strength and high ductility

    International Nuclear Information System (INIS)

    Tawancy, H.M.; Aboelfotoh, M.O.

    2009-01-01

    We demonstrate that bulk nanoscale materials with high strength and high ductility can be synthesized by using long-range ordering in certain alloy systems. In the case of a Ni-18.6 atomic % Mo-15.1 atomic % Cr, a bulk nanoscale superlattice of Ni 2 (Cr,Mo) isomorphous with Pt 2 Mo has been synthesized by thermal aging at 700 deg. C. The superlattice is shown to have high strength and high ductility as well as high thermal stability. Although the yield strength is nearly doubled in the ordered state exceeding 800 MPa, the material is found to maintain about 70% of its initial tensile ductility corresponding to 42% engineering strain. This behavior has been related to the crystallography of the ordering transformation. Although most of the slip systems of the parent face-centered cubic lattice are suppressed by ordering, most of the twinning systems remain energetically favorable. Therefore, deformation in the ordered state is found to predominantly occur by twinning rather than by slip giving rise to the observed combination of high strength and high ductility

  10. Comparison of extrapolation methods for creep rupture stresses of 12Cr and 18Cr10NiTi steels

    International Nuclear Information System (INIS)

    Ivarsson, B.

    1979-01-01

    As a part of a Soviet-Swedish research programme the creep rupture properties of two heat resisting steels namely a 12% Cr steel and an 18% Cr12% Ni titanium stabilized steel have been studied. One heat from each country of both steels were creep tested. The strength of the 12% Cr steels was similar to earlier reported strength values, the Soviet steel being some-what stronger due to a higher tungsten content. The strength of the Swedish 18/12 Ti steel agreed with earlier results, while the properties of the Soviet steel were inferior to those reported from earlier Soviet creep testings. Three extrapolation methods were compared on creep rupture data collected in both countries. Isothermal extrapolation and an algebraic method of Soviet origin gave in many cases rather similar results, while the parameter method recommended by ISO resulted in higher rupture strength values at longer times. (author)

  11. Creep properties and simulation of weld repaired low alloy heat resistant CrMo and Mo steels at 540 deg C. Sub project 1 - Ex-serviced parent metal and virgin weld metals

    Energy Technology Data Exchange (ETDEWEB)

    Rui Wu; Storesund, Jan; Borggreen, Kjeld; Weilin Zang

    2006-10-15

    Many existing power generating and process plants, where low alloy heat resistant CrMo(V) steels are extensively used for critical components, have exceeded their design lifetime of usually 100,000 hours. Assessment of residual lifetime and extension of economic life by weld repair have become increasingly important and attractive. This project aims at i) performing weld repair and determining the degree of mismatching, ii) evaluating the creep properties of weld repairs, iii) analysing creep behaviour of weld repair and providing necessary data for further reliable simulations of weld repair creep behaviour in long term service, and iv), simulating and assessing lifetime and creep damage evolution of weld repair. Weld repair using 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 consumables has been carried out in a service-exposed 10 CrMo 9 10 pipe. Creep specimens have been extracted from the service-exposed 10 CrMo 9 10 parent metal (PM), from the virgin 10 CrMo 9 10 weld metal (WM), from the virgin 13 CrMo 4 4 WM as well as from the virgin 15 Mo 3 WM. Iso-thermal uniaxial creep tests have been performed at 540 deg C in air. Pre- and post-metallography are carried out on the selected samples. FEM simulations using obtained creep data are executed. Pre-test metallography shows normal and acceptable weld repairs at given welding conditions. Creep tests demonstrate that the virgin 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 WMs have apparently longer creep lifetime than the service-exposed CrMo 9 10 PM at higher stresses than 110 MPa. Among the weld metals, the longest creep lifetime is found in 10 CrMo 9 10. Higher creep strength and lower creep strain rate in the weld metals indicate an overmatch weld. At 95 MPa, however, lifetime of 13 CrMo 4 4 WM is surprisingly short (factors which may shorten lifetime are discussed and one more test will start to verify creep strength at low stress) and tests are still running for other two weld metals. More results regarding low stress

  12. Effect of tensile deformation on micromagnetic parameters in 0.2% carbon steel and 2.25Cr-1Mo steel

    Energy Technology Data Exchange (ETDEWEB)

    Moorthy, V.; Vaidyanathan, S.; Jayakumar, T.; Raj, B. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Group; Kashyap, B.P. [Indian Inst. of Tech., Bombay (India). Dept. of Metallurgical Engineering and Materials Science

    1999-04-23

    The influence of prior tensile deformation on the magnetic Barkhausen emission (MBE) and the hysteresis (B-H) curve has been studied in 0.2% carbon steel and 2.25Cr-1Mo steel under different tempered conditions. This study shows that the micromagnetic parameters can be used to identify the four stages of deformation, namely (1) perfectly elastic, (2) microplastic yielding, (3) macroyielding and (4) progressive plastic deformation. However, it is observed that the MBE profile shows more distinct changes at different stages of tensile deformation than the hysteresis curve. It has been established that the beginning of microplastic yielding and macroyielding can be identified from the MBE profile which is not possible from the stress-strain plot. The onset of microplastic yielding can be identified from the decrease in the MBE peak height. The macroyielding can be identified from the merging of the initially present two-peak MBE profile into a single central peak with relatively higher peak height and narrow profile width. The difference between the variation of MBE and hysteresis curve parameters with strain beyond macroyielding indicates the difference in the deformation state of the surface and bulk of the sample.

  13. Thermal expansion of Cr2xFe2-2xMo3O12, Al2xFe2-2xMo3O12 and Al2xCr2-2xMo3O12 solid solutions

    International Nuclear Information System (INIS)

    Ari, M.; Jardim, P.M.; Marinkovic, B.A.; Rizzo, F.; Ferreira, F.F.

    2008-01-01

    The transition temperature from monoclinic to orthorhombic and the thermal expansion of the orthorhombic phase were investigated for three systems of the family A 2 M 3 O 12 : Cr 2x Fe 2-2x Mo 3 O 12 , Al 2x Fe 2-2x Mo 3 O 12 and Al 2x Cr 2-2x Mo 3 O 12 . It was possible to obtain a single-phase solid solution in all studied samples (x=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1). A linear relationship between the transition temperature and the fraction of A 3+ cations (x) was observed for each system. In all orthorhombic solid solutions studied here the observed thermal expansion was anisotropic. These anisotropic thermal expansion properties of crystallographic axes a, b and c result in a low positive or near-zero overall linear coefficient of thermal expansion (α l =α V /3). The relationship between the size of A 3+ cations in A 2 M 3 O 12 and the coefficient of thermal expansion is discussed. Near-zero thermal expansion of Cr 2 Mo 3 O 12 is explained by the behavior of Cr-O and Mo-O bond distances, Cr-Mo non-bond distances and Cr-O-Mo bond angles with increasing temperature, estimated by Rietveld analysis of synchrotron X-ray powder diffraction data. - Graphical abstract: In this figure, all published overall linear coefficients of thermal expansion for orthorhombic A 2 M 3 O 12 family obtained through diffraction methods as a function of A 3+ cation radii size, together with dilatometric results, are plotted. Our results indicate that Cr 2 Mo 3 O 12 does not exactly follow the established relationship

  14. Alloying effect on martensite transformation in stainless steels

    International Nuclear Information System (INIS)

    Gulyaev, A.P.; Shlyamnev, A.P.; Sorokina, N.A.

    1975-01-01

    The effect of cobalt, nickel, molybdenum on the martensite transformation kinetics in stainless steels containing 9 to 13% Cr has been studied. Cobalt in Fe-Cr base alloys decreases the temperature of the Msub(in) and Msub(fin) points without a considerable decrease of the martensite phase amount after the transformation. Nickel reduces the martensite transformation temperature range, the nickel effect being enhanced in the presence of cobalt, which is characterized by a change of the linear dependence Msub(in)=f(%Ni) for a quadratic one. Molybdenum decreases the temperature of the Msub(in) and Msub(fin) points intensively, thus, substantially increasing the residual austenite amount. In the steels investigated Ni and Co decrease, whereas Mo increases, to some extent, the temperature of the reverse a-γ-transformation. The reduction of chromium content from 13 to 9% stimulates the martensite transformation initiation, that is why, in alloys containing 9% Cr, the increase in the contents of Ni, Co., Mo with the martensite structure maintained is possible. A further alloying of steel containing 13% Cr with these elements is rather limited due to the inhibition of the martensite transformation

  15. Overview of 9Cr steels properties for structural application in sodium fast reactors

    International Nuclear Information System (INIS)

    Cabet, Celine; Courouau, Jean-Louis; Dalle, France; Desgranges, Clara; Forest, Laurent; Martinelli, Laure; Sauzay, Maxime

    2015-01-01

    A research and development programme has been launched by CEA, EDF and AREVA for the choice and qualification of material for sodium fast reactor (SFR) structural components. The requirements on steam generator (SG) are demanding, with operating temperatures ranging from 240 deg. C to 530 deg. C in water/steam and in sodium for an extended design life of several decades. The selection of the SG materials is based on many characteristics: fabrication, welding, thermal properties, mechanical strength at low and high temperature, environmental resistance. 9%Cr steels which are relevant candidate alloys for different designs of SGs have been extensively studied in the past decade. The objective of this paper is to review some advances made at CEA on determining properties of the X10CrMoVNb9-1 steel (hereafter named 'grade 91'): welding, modelling of cyclic softening, modelling of long-term creep, compatibility with liquid sodium, corrosion in steam. (authors)

  16. Microstructure refinement and strengthening mechanisms of a 9Cr oxide dispersion strengthened steel by zirconium addition

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hai Jian; Lu, Zheng; Wang, Dong Mei; Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang (China)

    2017-02-15

    To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of Fe-9Cr-2W-0.3Y{sub 2}O-3 and Fe-9Cr-2W-0.3Zr-0.3Y{sub 2}O{sub 3} were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal δ-phase Y{sub 4}Zr{sub 3}O{sub 12} oxides and body-centered cubic Y{sub 2}O{sub 3} oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of Y{sub 4}Zr{sub 3}O{sub 12} particles is much smaller than that of Y{sub 2}O{sub 3}. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is 1.1 x 10{sup 23}/m{sup 3} with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time.

  17. Solidification Segregation and Homogenization Behavior of 1Cr-1.25Mo-0.25V Steel Ingot

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Bae [Dae-gu Mechatronics and Materials Institute, Daegu (Korea, Republic of); Na, Young-Sang; Seo, Seong-Moon [Korea Institute of Materials Science, Changwon (Korea, Republic of); Lee, Je-Hyun [Changwon National University, Changwon (Korea, Republic of)

    2016-09-15

    As a first step to optimizing the homogenization heat treatment following high temperature upset forging, the solidification segregation and the homogenization behaviors of solute elements were quantitatively analyzed for 1Cr-1.25Mo-0.25V steel ingot by electron probe micro-analysis (EPMA). The random sampling approach, which was designed to generate continuous compositional profiles of each solute element, was employed to clarify the segregation and homogenization behaviors. In addition, ingot castings of lab-scale and a 16-ton-sized 1Cr-1.25Mo-0.25V steel were simulated using the finite element method in three dimensions to understand the size effect of the ingot on the microsegregation and its reduction during the homogenization heat treatment. It was found that the microsegregation in a large-sized ingot was significantly reduced by the promotion of solid state diffusion due to the extremely low cooling rate. On the other hand, from the homogenization point of view, increasing the ingot size causes a dramatic increase in the dendrite arm spacing, and hence the homogenization of microsegregation in a large-sized ingot appears to be practically difficult.

  18. Fracture behavior of unirradiated HT-9 and modified 9Cr-1Mo welds

    International Nuclear Information System (INIS)

    Huang, F.H.; Gelles, D.S.

    1983-05-01

    Fracture toughness tests on HT-9 weld and HAZ samples and modified 9Cr-1Mo weld samples were performed at 93, 205, 427 and 538 0 C. Specimens were of circular compact tension type fabricated from welded material with the notch orientation parallel to the fusion line. The test results were analyzed using the J-integral approach. The results demonstrated that the toughness of HT-9 and 9Cr-1Mo was not significantly reduced due to welding. However, the tearing modulus of the welded material was lower than that of base metal, indicating that the alloys become less resistant to crack propagation as a result of welding

  19. Detection of Hydrogen Sulphide Gas Sensor Based Nanostructured Ba2CrMoO6 Thick Films

    Directory of Open Access Journals (Sweden)

    A. V. Kadu

    2007-11-01

    Full Text Available Nanocrystalline pure and doped Ba2CrMoO6, having an average crystallite size of 40 nm were synthesized by the sol-gel citrate method. Structural and gas-sensing characteristics were performed by using X-ray diffraction (XRD and sensitivity measurements. The gas sensing properties to reducing gases like Hydrogen sulphide (H2S, liquefied petroleum gas (LPG, carbon monoxide (CO and hydrogen gas (H2 were also discussed. The maximum sensitivity was obtained for 5 wt % Ni doped Ba2CrMoO6 at an operating temperature 250oC for H2S gas. Pd incorporation over 5 wt% Ni doped Ba2CrMoO6 improved the sensitivity, selectivity, response time, and reduced the operating temperature from 250 to 200oC of the sensor for H2S gas. This sensor also shows good satiability.

  20. Effect of silicon contents on the microstructures and mechanical properties of heat affected zones for 9Cr2WVTa steels

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jian [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Lu, Shanping, E-mail: shplu@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Rong, Lijian [Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Li, Dianzhong [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China)

    2016-03-15

    The weldability of 9Cr2WVTa steels with silicon content varying from 0.30 wt.% to 1.36 wt.% was studied to meet the requirement of Generation-Ⅳ nuclear reactor. Samples of enlarged HAZs were fabricated by a thermal-mechanical simulator based on the simulation and measurement of non-equilibrium phase transformation. The content of δ-ferrite in the HAZs increased with the silicon content and the peak temperature of welding thermal cycle. The impact toughness in the HAZs decreased in different degrees when the δ-ferrite exhibits stripe (lower than 4.82%) or blocky types (higher than 4.82%). Post weld heat treatment (PWHT) has a significant role on improving the toughness. Adding silicon content increased the volume of δ-ferrite and therefore, decreased the tensile strength of the HAZs for 9Cr2WVTa steels. Silicon also as solid solution strengthening element increased the tensile strength. The 9Cr2WVTa steel has good weldability when the silicon content is lower than 0.60 wt.%. - Highlights: • The weldability of 9Cr2WVTa steel with different silicon contents was studied. • The impact toughness decreased in different degrees owing to the δ-ferrite. • PWHT has a significant role on improving the impact toughness. • The 9Cr2WVTa steel with silicon content not exceeding 0.60 wt.% has good weldability.

  1. Constant strain rate test and SCC-behaviour of stainless steels

    International Nuclear Information System (INIS)

    Krauss, H.; Speckhardt, H.

    1979-01-01

    In the present work, the stress corrosion cracking behaviour in boiling aqueous 35% magnesium chloride solution under conditions of no external current was investigated as a function of the defined extension rates for the two austenitic steels X 2 CrNi 189 and X 2 CrNiSi 1815, as well as for both ferritic austenitic steels X 6 CrNiMoCu 217 and X 2 CrNiMoN 225. The endurance time found until cracking, the maximum tensile stress, the sample stretching up to cracking and the relative rupture energy were determined for the evaluation, as well as metallographic investigations to describe the crack picture, test surface appearance and attack picture carried out. (orig.) 891 RW/orig. 892 BRE [de

  2. Creep life assessment of Mod.9Cr-1Mo steel. Pt. 2. Quantitative evaluation of microstructural damage in creep-interrupted specimens

    International Nuclear Information System (INIS)

    Sawada, Kota; Maruyama, Kouichi; Komine, Ryuji; Nagae, Yuji

    1998-02-01

    Mod.9Cr-1Mo steel has a martensitic lath structure. Recovery of the lath structure takes place in the course of creep. Microstructural degradation due to the recovery results in the acceleration of creep rate and the subsequent failure of a specimen. Change of lath width during creep of the steel was quantitatively investigated to propose a residual life assessment methodology based on the recovery process. Since the steel was tempered at 1053K, the lath structure is thermally stable at the testing temperatures (848K-923K). However, recovery of lath structure readily takes place during creep, indicating that the recovery is induced by creep deformation. Lath width d increases with creep strain and saturates to a value d s determined by creep stress. The increase of d is faster at a higher stress and temperature. A normalized change in lath width, Δd/Δd s , was introduced to explain the variation of lath growth rate with creep stress and temperature. Δd is the change in lath width from the initial value d 0 , and Δd s is the difference between d s and d 0 . Δd/Δd s is uniquely related to creep strain ε and the relationship is independent of creep stress as well as creep temperature. This Δd/Δd s -ε relationship obtained by an accelerated creep test at a higher temperature or stress is applicable to any creep condition including service conditions of engineering plants. Creep strain can be evaluated from the measurement of Δd/Δd s based on the Δd/Δd s -ε relationship. A creep curve under any creep condition can readily be calculated by creep data of the steel. Combining these information one can assess residual life of a structural component made of the steel. (author)

  3. Mean Stress Effect on the Axial Fatigue Strength of DIN 34CrNiMo6 Quenched and Tempered Steel

    Directory of Open Access Journals (Sweden)

    Luis Pallarés-Santasmartas

    2018-03-01

    Full Text Available The present study consists of a theoretical and experimental investigation of the effect of axial mean stresses on the high cycle fatigue behaviour of DIN 34CrNiMo6 high strength steel in quenched and tempered conditions. The axial S-N curves under 4 different stresses ratios were obtained. Experimental results show that increasing the value of the tension mean stresses gradually reduces the axial stress amplitude the material can withstand without failure. Moreover, the compressive mean stresses show a beneficial effect in terms of the axial fatigue strength, resulting in a non-symmetrical Haigh diagram. A historic review of the axial mean stress effect is presented, showing the shape of the Haigh diagrams for ductile metals and presenting the most-known empirical and physical theories. The results for this steel are compared with the physical theories of Findley based on the critical plane; the Froustey’s and Marin’s methods, based on energetic theories; and the Crossland invariants method based on the Gough’s theory of fatigue damage. Taking into account the experimental results, a physical fatigue function based on energetic considerations is proposed. Its application to the fatigue case with mean stresses can be interpreted in terms of a balance of elastic energies of distortion and volume change. Macro-analyses of specimen fracture appearance were conducted in order to obtain the fracture characteristics for different mean stress values.

  4. Composition design of superhigh strength maraging stainless steels using a cluster model

    Directory of Open Access Journals (Sweden)

    Zhen Li

    2014-02-01

    Full Text Available The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3, where NiFe12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni with surplus Ni was then determined to ensure the second phase (Ni3M precipitation, based on which new multi-component alloys [(Ni,Cu16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V16 were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu4Ni12Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1 alloy (Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78 wt% has higher tensile strengths with YS=1456 MPa and UTS=1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.

  5. Development of oxide dispersion strengthened 9Cr ferritic-martensitic steel clad tube for fast reactor

    International Nuclear Information System (INIS)

    Laha, K.; Saroja, S.; Mathew, M.D.; Jayakumar, T.; Vijay, R.; Venugopal Reddy, A.; Lakshminarayana, B.; Kapoor, Komal; Jha, S.K.; Tonpe, S.S.

    2012-01-01

    One of the key issues in the economical operation of FBR is to achieve high burn-up of fuel (200-250 GWd/t) which considerably reduces the fuel cycle cost. This imposes stringent requirements of void swelling resistance upto 200 dpa for the core structural materials. Presently used alloy 09 (a modified austenitic stainless steel, 15Cr-15Ni-Ti) for PFBR has void swelling limit less than 150 dpa. Because of the inherent void swelling resistance, 9-12Cr steels ferritic/martensitic steels are qualified for irradiation upto 200 dpa but their low creep strength at temperatures above 600 deg C restricts their application as a clad material. Oxide dispersion strengthening is found to be promising means of extending the creep resistance of ferritic/martensitic steels beyond 650 deg C without sacrificing the inherent advantages of high thermal conductivity and low swelling of ferritic steels

  6. Elevated temperature creep and fatigue damage of a 2.25 Cr--1 Mo steel weldment

    International Nuclear Information System (INIS)

    Van Den Avyle, J.A.

    1978-01-01

    In weldments between dissimilar metals wide variations occur in metallurgical structure and mechanical properties, so that for good structural design it is necessary to understand the mechanical response of individual microstructural segments of the weld. This study investigates elevated temperature properties of a 2.25 Cr--1 Mo ferritic steel base metal welded with Chromenar 382V (Inconel 82) filler metal. Creep and low-cycle fatigue tests at 866 0 K (1100 0 F) show the filler metal and heat affected zone to be much stronger than the base metal. Optical microscopy does not show significant aging effects in the short-term fatigue tests or creep tests of 1180 hour duration

  7. Application of long-range ordering in the synthesis of a nanoscale Ni{sub 2} (Cr,Mo) superlattice with high strength and high ductility

    Energy Technology Data Exchange (ETDEWEB)

    Tawancy, H.M. [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1639, Dhahran 31261 (Saudi Arabia)], E-mail: tawancy@kfupm.edu.sa; Aboelfotoh, M.O. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7909 (United States)

    2009-01-25

    We demonstrate that bulk nanoscale materials with high strength and high ductility can be synthesized by using long-range ordering in certain alloy systems. In the case of a Ni-18.6 atomic % Mo-15.1 atomic % Cr, a bulk nanoscale superlattice of Ni{sub 2}(Cr,Mo) isomorphous with Pt{sub 2}Mo has been synthesized by thermal aging at 700 deg. C. The superlattice is shown to have high strength and high ductility as well as high thermal stability. Although the yield strength is nearly doubled in the ordered state exceeding 800 MPa, the material is found to maintain about 70% of its initial tensile ductility corresponding to 42% engineering strain. This behavior has been related to the crystallography of the ordering transformation. Although most of the slip systems of the parent face-centered cubic lattice are suppressed by ordering, most of the twinning systems remain energetically favorable. Therefore, deformation in the ordered state is found to predominantly occur by twinning rather than by slip giving rise to the observed combination of high strength and high ductility.

  8. Passivation Characteristics of Alloy Corrosion-Resistant Steel Cr10Mo1 in Simulating Concrete Pore Solutions: Combination Effects of pH and Chloride.

    Science.gov (United States)

    Ai, Zhiyong; Sun, Wei; Jiang, Jinyang; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

    2016-09-01

    The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance spectroscopy and capacitance measurements. The chemical composition and structure of passive films were determined by XPS. The morphological features and surface composition of the immersed steel were evaluated by SEM together with EDS chemical analysis. The results evidence that pH plays an important role in the passivation of the corrosion-resistant steel and the effect is highly dependent upon the chloride contents. In solutions with low chloride (0.2 M), the corrosion-resistant steel has notably enhanced passivity with pH falling from 13.3 to 9.0, but does conversely when in presence of high chloride (1.0 M). The passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer, rich in Cr species. The film composition varies with pH values and chloride contents. As the pH drops, more Cr oxides are enriched in the film while Fe oxides gradually decompose. Increasing chloride promotes Cr oxides and Fe oxides to transform into their hydroxides with little protection, and this is more significant at lower pH (10.5 and 9.0). These changes annotate passivation characteristics of the corrosion-resistant steel in the solutions of different electrolyte.

  9. Phase formation in Na2MoO4 - MgMoO4 - Cr2(MoO4)3 system

    International Nuclear Information System (INIS)

    Kotova, I.Yu.; Kozhevnikova, N.M.

    1998-01-01

    Interaction within Na 2 MoO 4 - MgMoO 4 - Cr 2 (MoO 4 ) 3 ternary system is studied by X ray phase and DTA methods. State diagram of NaCr(MoO 4 ) 2 - MgMoO 4 section is plotted. Production of ternary molybdates of Na 1-x Mg 1-x Cr 1+x (MoO 4 ) 3 , where 0 ≤ x ≤ 0.3, and NaMg 3 Cr(MoO 4 ) 5 composition is ascertained [ru

  10. Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

    Science.gov (United States)

    Huttunen-Saarivirta, E.; Honkanen, M.; Tsipas, S. A.; Omar, H.; Tsipas, D.

    2012-10-01

    Degradation of materials by a combination of erosive wear and atmospheric oxidation at elevated temperatures constitutes a problem in some power generation processes, such as fluidized-bed combustion. In this work, 9Cr-1Mo steel, a common tube material in combustion chambers, is coated by a pack cementation method from an Al-containing pack in order to improve the resistance to erosion-oxidation at elevated temperatures. The resulting coating is studied in terms of microstructure and microhardness and tested for its resistance against impacts by sand particles in air at temperatures of 550-700 °C under several conditions, with thickness changes and appearance of the exposed surfaces being studied. The coating was found to contain several phases and layers, the outermost of which was essentially Al-rich and contained e.g., small AlN precipitates. The microhardness values for such coating ranged from 950 to 1100 HV20g. The coating provided the substrate with increased protection particularly against normal particle impacts, as manifested by smaller thickness losses for coated specimens as compared to uncoated counterparts. However, much of the coating was lost under all test conditions, despite the fact that particle debris formed a homogeneous layer on the surface. These results are described and discussed in this paper.

  11. Transfer of modified 9Cr-1Mo steel technology through cooperative programs (1980-1985)

    International Nuclear Information System (INIS)

    Sikka, V.K.; DiStefano, J.R.; Patriarca, P.

    1986-06-01

    The principal objective of the United States Department of Energy (DOE) 9Cr-1Mo steel development program has been to provide the data and analyses required by designers for use of the alloy in advanced liquid metal reactors to reduce technical tasks and plant capital costs. It was recognized early that designers would not consider use of any material for nuclear applications unless there was a considerable body of experience already established. Toward this end, the plan has been to get the alloy accepted in Section I (Power Boilers), Section II (Materials Specifications), Section VIII (Pressure Vessels), and Section III (Nuclear power Plant Components) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code as logical steps in the process. To achieve this objective, extensive interaction with the industrial community was considered mandatory. Accordingly, an intensive effort to achieve technology transfer was initiated, which resulted in the involvement of many organizations. This report is a compilation of 47 status sheets describing 35 participating organizations and funding sources, purpose of the interactions, material and product forms utilized, summary of the work completed, findings, and appropriate references. These interactions contributed significantly toward the fulfillment of the program goals

  12. Kinetics of steel corrosion in water

    International Nuclear Information System (INIS)

    Vettegren', V.I.; Bashkarev, A.Ya.; Danchukov, K.G.; Morozov, G.I.

    2003-01-01

    Kinetics of corrosion damage accumulation in steels of different composition (Cr-Ni-Mo-Ti, Cr-Ni-Mn-N-V, Cr-Ni-N-Mn-Mo, Cr-Ni-Nb, Cr-Ni-Ti, Cr-Mn-Ni, Mn-Al-Nb-Si, Mn-Cr-Al-Si and Mn-Al-Si) in NaCl solution and in sea water was studied. It is shown that degree of corrosion damage relates to time according to the first order reaction expression. The values of corrosion activation energy and of parameter characterizing protection properties of corrosion film are determined [ru

  13. Characterization of corrosion resistant on NiCoCr coating layer exposed to 5%NaCl

    Science.gov (United States)

    Sugiarti, E.; Sundawa, R.; Desiati, R. D.; Zaini, K. A.

    2018-03-01

    Highly corrosion resistant of carbon steel coated NiCoCr was applied in corrosive of marine environtment. Carbon steel coated NiCoCr was prepared by a two step technique of NiCo electro-deposition and Cr pack cementation. The samples were exposed to 5 wt.% NaCl for 48 and 168 hours. The microstructure and corrosion product were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The corrosion resistance of carbon steel coated NiCoCr was found to be better than that of carbon steel substrate without coating. The results showed the microstructure of 48 h corroded sample has duplex layer composed of inner α-(Ni,Co), α-Cr and outer Cr2O3, while a quite thin and continues protective oxide of Cr2O3 was observed in outer layer of 168 h corroded sample. The formation of oxide scale rich in Cr2O3 has contributed for the better corrosion resistance of carbon steel coated NiCoCr, whereas the formation of non protective oxide of iron might caused low corrosion resistance of carbon steel substrate.

  14. Erosion-oxidation behavior of thermal sprayed Ni20Cr alloy and WC and Cr3C2 cermet coatings

    Directory of Open Access Journals (Sweden)

    Clarice Terui Kunioshi

    2005-06-01

    Full Text Available An apparatus to conduct high temperature erosion-oxidation studies up to 850 °C and with particle impact velocities up to 15 m.s-1 was designed and constructed in the Corrosion Laboratories of IPEN. The erosion-oxidation behavior of high velocity oxy fuel (HVOF sprayed alloy and cermet coatings of Ni20Cr, WC 20Cr7Ni and Cr3C2 Ni20Cr on a steel substrate has been studied. Details of this apparatus and the erosion-oxidation behavior of these coatings are presented and discussed. The erosion-oxidation behavior of HVOF coated Cr3C2 25(Ni20Cr was better than that of WC 20Cr7Ni, and the erosion-oxidation regimes have been identified for these coatings at particle impact velocity of 3.5 m.s-1, impact angle of 90° and temperatures in the range 500 to 850 °C.

  15. Reduction factors for creep strength and fatigue life of modified 9Cr-1 Mo steel weldments

    International Nuclear Information System (INIS)

    Blass, J.J.; Battiste, R.L.; O'Connor, D.G.

    1991-01-01

    This paper reports on the provisions of ASME B and PV code Case N-47 currently include reduction factors for creep strength and fatigue life of weldments. To provide experimental confirmation of such factors for modified 9 Cr-1 Mo steel, tests of tubular specimens were conducted at 538 degrees C (1000 degrees F). Three creep-rupture specimens with longitudinal welds were tested in tension; and, of three with circumferential welds, two were tested in tension and one in torsion. In each specimen with a circumferential weld, a nonuniform axial distribution of strain was easily visible. The test results were compared to an existing empirical model of creep-rupture life. For the torsion test, the comparison was based on a definition of equivalent normal stress recently adopted in code Case N-47. some 27 fatigue specimens, with longitudinal, circumferential, or no welds, were tested under axial or torsional strain control. In specimens with welds, fatigue cracking initiated at fusion lines. In axial tests cracks grew in the circumferential direction, and in torsional tests cracks grew along fusion lines

  16. Creep constitutive equation of dual phase 9Cr-ODS steel

    International Nuclear Information System (INIS)

    Sakasegawa, Hideo; Ukai, Shigeharu; Tamura, Manabu; Ohtsuka, Satoshi; Tanigawa, Hiroyasu; Ogiwara, Hiroyuki; Kohyama, Akira; Fujiwara, Masayuki

    2008-01-01

    9Cr-ODS (oxide dispersion strengthened) steels developed by JAEA (Japan Atomic Energy Agency) have superior creep properties compared with conventional heat resistant steels. The ODS steels can enormously contribute to practical applications of fast breeder reactors and more attractive fusion reactors. Key issues are developments of material processing procedures for mass production and creep life prediction methods in present R and D. In this study, formulation of creep constitutive equation was performed against the backdrop. The 9Cr-ODS steel displaying an excellent creep property is a dual phase steel. The ODS steel is strengthened by the δ ferrite which has a finer dispersion of oxide particles and shows a higher hardness than the α' martensite. The δ ferrite functions as a reinforcement in the dual phase 9Cr-ODS steel. Its creep behavior is very unique and cannot be interpreted by conventional theories of heat resistant steels. Alternative qualitative model of creep mechanism was formulated at the start of this study using the results of microstructural observations. Based on the alternative creep mechanism model, a novel creep constitutive equation was formulated using the exponential type creep equation extended by a law of mixture

  17. Formation of Al{sub 2}O{sub 3}/FeAl coatings on a 9Cr-1Mo steel, and corrosion evaluation in flowing Pb-17Li loop

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, Sanjib, E-mail: sanjib@barc.gov.in [High Temperature Materials Development Section, Materials Processing & Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Paul, Bhaskar [High Temperature Materials Development Section, Materials Processing & Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Chakraborty, Poulami [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Kishor, Jugal; Kain, Vivekanand [High Temperature Materials Development Section, Materials Processing & Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Dey, Gautam Kumar [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Materials Group, Bhabha Atomic Research Centre, Trombay, Mumbai (India)

    2017-04-01

    Iron aluminide coating layers were formed on a ferritic martensitic grade 9Cr-1Mo (P 91) steel using pack aluminizing process. The formation of different aluminide compositions such as orthorhombic-Fe{sub 2}Al{sub 5}, B2-FeAl and A2-Fe(Al) on the pack chemistry and heat treatment conditions have been established. About 4–6 μm thick Al{sub 2}O{sub 3} scale was formed on the FeAl phase by controlled heat treatment. The corrosion tests were conducted using both the FeAl and Al{sub 2}O{sub 3}/FeAl coated specimens in an electro-magnetic pump driven Pb-17Li Loop at 500 °C for 5000 h maintaining a flow velocity of 1.5 m/s. The detailed characterization studies using scanning electron microscopy, back-scattered electron imaging and energy dispersive spectrometry revealed no deterioration of the coating layers after the corrosion tests. Self-healing oxides were formed at the cracks generated in the aluminide layers during thermal cycling and protected the base alloy (steel) from any kind of elemental dissolution or microstructural degradation. - Highlights: •Al{sub 2}O{sub 3}/FeAl coating produced on P91 steel by pack aluminizing and heat treatment. •Corrosion tests of coated steel conducted in flowing Pb-17Li loop at 500 °C for 5000 h. •Coating was protective against molten metal corrosion during prolonged exposure. •Self-healing protective oxides formed in the cracks generated in aluminide layers.

  18. High strain rate tensile properties of annealed 2 1/4 Cr--1 Mo steel

    International Nuclear Information System (INIS)

    Klueh, R.L.; Oakes, R.E. Jr.

    1975-01-01

    The high strain rate tensile properties of annealed 2 1 / 4 Cr-1 Mo steel were determined and the tensile behavior from 25 to 566 0 C and strain rates of 2.67 x 10 -6 to 144/s were described. Above 0.1/s at 25 0 C, both the yield stress and the ultimate tensile strength increased rapidly with increasing strain rate. As the temperature was increased, a dynamic strain aging peak appeared in the ultimate tensile strength-temperature curves. The peak height was a maximum at about 350 0 C and 2.67 x 10 -6 /s. With increasing strain rate, a peak of decreased height occurred at progressively higher temperatures. The major effect of strain rate on ductility occurred at elevated temperatures, where a decrease in strain rate caused an increase in total elongation and reduction in area

  19. Microstructures and mechanical properties of 9Cr oxide dispersion strengthened steel produced by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Rui [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); School of Metallurgy, Northeastern University, Shenyang 110819 (China); Lu, Zheng, E-mail: luz@atm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Lu, Chenyang; Li, Zhengyuan [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Ding, Xueyong [School of Metallurgy, Northeastern University, Shenyang 110819 (China); Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China)

    2017-02-15

    Highlights: • A 9Cr-ODS steel was produced by mechanical alloying and spark plasma sintering. • Bimodal grain size distribution was observed. • Formation mechanism of bimodal grain size distribution was discussed. • The size and number density of nanoscale particles were obtained by SAXS and HRTEM. • The contribution of nano-sized particles to yield strength is dominating. - Abstract: 9Cr oxide dispersion strengthened (ODS) steel was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The nano-sized particles, grain size distribution and mechanical properties of 9Cr-ODS steel sintered at 950 °C were studied by synchrotron radiation small angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (HRTEM), electron backscatter diffraction (EBSD) and tensile experiment. The results showed that bimodal grain size distribution in the matrix is observed, which is attributed to the heterogeneous recrystallization process during the SPS. High-density nano-sized Y{sub 2}Ti{sub 2}O{sub 7} and some large oxides of Cr{sub 2}Mn(Ti)O{sub 4} are formed in 9Cr-ODS steel. The number density and average size of Y{sub 2}Ti{sub 2}O{sub 7} obtained from SAXS are 4.72 × 10{sup 22}/m{sup 3} and 4.4 nm, respectively. The yield strengths of 9Cr-ODS steel fabricated by SPS are compared with the typical 9Cr-ODS steel produced by HIP.

  20. Magnetoresistance in Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions.

    Science.gov (United States)

    Zhang, Han; Ye, Meng; Wang, Yangyang; Quhe, Ruge; Pan, Yuanyuan; Guo, Ying; Song, Zhigang; Yang, Jinbo; Guo, Wanlin; Lu, Jing

    2016-06-28

    Semiconducting single-layer (SL) and few-layer MoS2 have a flat surface, free of dangling bonds. Using density functional theory coupled with non-equilibrium Green's function method, we investigate the spin-polarized transport properties of Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions with MoS2 layer numbers of N = 1, 3, and 5. Well-defined interfaces are formed between MoS2 and metal electrodes. The junctions with a SL MoS2 spacer are almost metallic owing to the strong coupling between MoS2 and the ferromagnets, while those are tunneling with a few layer MoS2 spacer. Both large magnetoresistance and tunneling magnetoresistance are found when fcc or hcp Co is used as an electrode. Therefore, flat single- and few-layer MoS2 can serve as an effective nonmagnetic spacer in a magnetoresistance or tunneling magnetoresistance device with a well-defined interface.

  1. Cooperation on impingement wastage experiment of Mod. 9Cr-1Mo steel using SWAT-1R sodium-water reaction test facility

    International Nuclear Information System (INIS)

    Beauchamp, F.; Allou, A.; Nishimura, M.; Umeda, R.

    2013-01-01

    Conclusion: • 6 experiments were carried out in the SWAT-1R facility of JAEA Oarai R&D Center to study the wastage resistance of the Mod. 9Cr-1Mo steel (T91) straight tubes. • These experiments were performed under the cooperation between CEA and JAEA. • The experiments were conducted successfully: - all the tubes were punctured by the reaction jet, - wastage and steam/water leak rates were obtained, - experimental results brought some new determining sets of wastage data on T91. • This fruitful cooperation has contributed to: - expanding the wastage database on T91, - upgrading wastage rates prediction from modelling, - the safety demonstration of future steam generators units

  2. Microstructural evaluation and non-destructive examination of 2.25 Cr--1 Mo steel

    International Nuclear Information System (INIS)

    Van Den Avyle, J.A.; Jones, W.B.; Gieske, J.H.

    1978-07-01

    Specimens of 2.25 Cr-1 Mo steel were damaged to various levels by creep and combined creep-fatigue cycling at 886 0 K (1100 0 F) with hold periods. Ultrasonic shear wave velocity measurements were performed and showed small changes with large amounts of creep or fatigue damage; these changes were deemed too small for practical application. Measurements of magnetic properties were unsuccessful in following damage. Optical and transmission electron microscopy (TEM) were performed on the samples. TEM observations showed that microstructural changes which occurred at 886 0 K (1100 0 F) did not occur homogeneously throughout the matrix; during creep, carbide spheroidization and coarsening began in widely separated regions, with an increasing fraction of the material undergoing the process with time. A precipitate was observed to form during fatigue which did not occur during simple aging or creep

  3. Microstructure, state of internal stress and corrosion resistance of the short-time laser heat-treated nitrogen high-alloyed tool steel X30CrMoN151; Mikrostruktur, Eigenspannungszustand und Korrosionsbestaendigkeit des kurzzeitlaserwaermebehandelten hochstickstofflegierten Werkzeugstahls X30CrMoN151

    Energy Technology Data Exchange (ETDEWEB)

    Bohne, C. (ed.)

    2000-07-01

    This study compares the crystalline structure, state of internal stress and chemical properties of the high-alloyed nitrogen tool steel X30CrMoN15 1 and conventional cold work steel X39CrMo17 1. Transformation points A{sub c}1b and A{sub c}1e were calculated from residual austenite analysis and the c{sub m}/a{sub m} martensite ratios for various heating rates. This was used to generate a TTA (time-temperature-austenitisation) graph for X30CrMoN15 1 for the first time. Transmission electron microscopy and small-angle neutron scattering show that precipitates in nitrogen high-alloyed steel X30CrMoN15 1 can be eliminated completely by short-time laser heat treatment. The corrosion tests show that in contrast to X39CrMo17 1 X30CrMoN15 1 reacts more sensitively to parameter changes during short-time heat treatment in oxidising acid at pH 5-6. [German] Im Rahmen der Arbeit werden die Gefuegeausbildung, Eigenspannungen und chemische Eigenschaften des hochstickstofflegierten Werkzeugstahls X30CrMoN15 1 und des konventionellen Kaltarbeitsstahls X39CrMo17 1 verglichen. Aus den Restaustenitanalysen und den c{sub m}/a{sub m}-Verhaeltnissen des Martensits konnten die Umwandlungspunkte A{sub c1b} und A{sub c1e} fuer verschiedene Aufheizraten bestimmt und daraus ein bisher nicht bekanntes ZTA-Schaubild fuer den X30CrMoN15 1 erstellt werden. Transmissionselektronenmikroskopie und Neutronenkleinwinkelstreuung zeigen, dass sich die Ausscheidungen im hochstickstofflegierten Stahl X30CrMoN14 1 durch die Kurzzeitlaserwaermebehandlung vollstaendig aufloesen koennen. Die Korrosionsversuche zeigen, dass im Gegensatz zum X39CrMo17 1 der X30CrMoN15 1 in oxidierender Saeure bei pH 5-6 empfindlicher auf Parameteraenderungen bei der Kurzzeitwaermebehandlung reagiert. (orig.)

  4. Numerical simulation of Cr2N age-precipitation in high nitrogen stainless steels

    International Nuclear Information System (INIS)

    Dai, Q.X.; Yuan, Z.Z.; Luo, X.M.; Cheng, X.N.

    2004-01-01

    At the temperature raging from 700 to 950 deg. C, the Cr 2 N age-precipitation in high nitrogen austenitic stainless steels Fe24Mn18Cr3Ni0.62N was investigated in this paper. A qualitative mathematical model of Cr 2 N age-precipitation, ln t S = f (Me,1/T), was established based on the thermodynamics and kinetics and phase transformation theories. Satisfactory results were obtained by means of the test of artificial neural network. This mathematical model can be applied to the calculation design and predication of Cr 2 N age-precipitation in high nitrogen stainless steels

  5. Effects of iron spallation products Ti, P and S on the physical metallurgy of 9Cr martensitic steels

    International Nuclear Information System (INIS)

    Danylova, O.; Carlan, Y. de; Hamon, D.; Brachet, J.C.; Alamo, A.

    2002-01-01

    The design of an Accelerator Driven System (ADS) requires that the 'window', which separates the proton accelerator from the spallation target, be able to withstand very severe irradiation conditions. Fe-9/12Cr martensitic steels are good candidates for the window material due to their intrinsic stability under neutron irradiation, but the influence of iron spallation elements on their behaviour is not known. To elucidate the effects of the spallation elements titanium, phosphorus and sulphur on the behaviour of martensitic steels, it was decides to obtain different castings of 9Cr 1Mo steels doped with these elements. The aim of this paper is to present the data obtained on the physical metallurgy of these steels and to show the possible methods of obtaining titanium, phosphorus and sulphur in solid solution for subsequent study of the evolution of the microstructure and mechanical properties. (authors)

  6. High temperature corrosion behavior of different grain size specimens of 2.25 Cr-1 Mo steel in SO2+O2 environment

    International Nuclear Information System (INIS)

    Ghosh, D.; Mitra, S.K.

    2011-01-01

    The investigation is primarily aimed at the high temperature corrosion behavior of different grain sizes of 2.25 Cr-1 Mo steel at SO 2 +O 2 (mixed oxidation and sulfidation). The various grain sizes (18 μm,26 μm, 48 μm, and 72 μm) are obtained by different annealing treatment. Isothermal corrosion studies are carried out in different grain size specimens at 973K for 8 hours. The corrosion growth rate and the reaction kinetics are studied by weight gain method. The external scales of the post corroded specimen are studied in Scanning Electron Microscope (SEM) to examine the corrosion products morphology on the scale. X-ray mapping analysis of the different elements (Fe, O, Cr and S) is carried out by Energy Dispersive Spectroscopy (EDS) attached with SEM. The X-ray Diffraction Analysis (XRD) is also carried out to identify the corrosion products in the external scale. Finally, it is concluded that that the corrosion rate of 2.25 Cr-1 Mo steel strongly depend on grain sizes of the specimens. The corrosion rate increases with the decreases of grain size. The finer grain (18 μm) show higher corrosion rate than the coarse grains (72 μm). The weight gain kinetics follows the parabolic growth rate which further indicates that the corrosion process is diffusion controlled. The scale analysis shows the thicker scale and extensive scale cracking and spallations in case of finer grain size specimen (18 μm), whereas the coarse grain specimen (72 μm) shows compact and adherent layer. The XRD analysis shows that the corrosion products consist of mixtures of iron oxides( Fe 3 O 4 and Fe 2 O 3 ) and iron sulfides (FeS). The details mechanism of the corrosion is discussed to explain the difference in corrosion rate for different grain sizes. (author)

  7. Ternary alloying study of MoSi2

    International Nuclear Information System (INIS)

    Yi, D.; Li, C.; Akselsen, O.M.; Ulvensoen, J.H.

    1998-01-01

    Ternary alloying of MoSi 2 with adding a series of transition elements was investigated by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). Iron, Co, Ni, Cr, V, Ti, and Nb were chosen as alloying elements according to the AB 2 structure map or the atomic size factor. The studied MoSi 2 base alloys were prepared by the arc melting process from high-purity metals. The EDS analysis showed that Fe, Co, and Ni have no solid solubility in as-cast MoSi 2 , while Cr, V, Ti, and Nb exhibit limited solid solubilities, which were determined to be 1.4 ± 0.7, 1.4 ± 0.4, 0.4 ± 0.1, and 0.8 ± 0.1. Microstructural characterization indicated that Mo-Si-M VIII (M VIII = Fe, Co, Ni) and Mo-Si-Cr alloys have a two-phase as-cast microstructure, i.e., MoSi 2 matrix and the second-phase FeSi 2 , CoSi, NiSi 2 , and CrSi 2 , respectively. In as-cast Mo-Si-V, Mo-Si-Ti, and Mo-Si-Nb alloys, besides MoSi 2 and C40 phases, the third phases were observed, which have been identified to be (Mo, V) 5 Si 3 , TiSi 2 , and (Mo, Nb) 5 Si 3

  8. Comparison of the mechanical strength properties of several high-chromium ferritic steels

    International Nuclear Information System (INIS)

    Booker, M.K.; Sikka, V.K.; Booker, B.L.P.

    1981-01-01

    A modified 9 Cr-1 Mo ferritic steel has been selected as an alternative material for breeder reactors. Different 9 Cr-1 Mo steels are already being used commercially in UK and USA and a 9 Cr-2 Mo steel (EM12) is being used commercially in France. The 12% Cr steel alloy HT9 is also often recommended for high-temperature service. Creep-rupture data for all six seels were analyzed to yield rupture life as a function of stress, temperature, and lot-to-lot variations. Yield and tensile strength data for the three 9 Cr-1 Mo materials were also examined. All results were compared with Type 304 stainless steel, and the tensile and creep properties of the modified and British 9 Cr-1 Mo materials were used to calculate allowable stress values S 0 per Section VIII, Division 1 and S/sub m/ per code Case N-47 to section III of the ASME Boiler and Pressure Vessel Code. these values were compared with code listings for American commercial 9 Cr-1 Mo steel, 2 1/4 Cr-1 Mo steel, and Type 304 stainless steel. The conclusion is made that the modified 9 Cr-1 Mo steel displays tensile and creep strengths superior to those of the other ferritic materials examined and is at least comparable to Type 304 stainless steel from room temperature to about 625 0 C. 31 figures

  9. Effect of HTGR helium on fatigue and creep properties of 2 1/4Cr-1Mo steel

    International Nuclear Information System (INIS)

    Kurumaji, T.; Yamazaki, H.; Kudo, A.

    1982-01-01

    Low cycle fatigue and creep tests have been carried out on 2 1/4Cr-1Mo steel (candidate steel for VHTR reactor pressure vessel) in helium environment containing 200 approx. 300 μatm of H 2 , 100 approx. 150 μatm CO, 7 approx. 10 μatm CH 4 , 7 approx. 10 μatm CO 2 and 1 μatm H 2 O (JAERI B Helium). Fatigue life in helium environment was longer than that in air at 450 0 C. This results can be explained by supposing that oxidation at the crack tip causes the wedge effect to promote crack propagation in air. On the otherhand, creep rupture strength showed no significant difference in both helium and air. Equivalent creep rupture strength in both helium and air may be due to the fact that detrimental internal oxidation and carburization or decarburization hardly occur at 400 approx. 450 0 C

  10. Influence of damage rate on physical and mechanical properties and swelling of 18Cr-9Ni austenitic steel in the range of 3.10-9 to 4.10-8 dpa/sec

    International Nuclear Information System (INIS)

    Shcherbakov, E.N.; Kozlov, A.V.; Yagovitin, R.I.; Evseev, M.V.; Kinev, E.A.; Isobe, Y.; Sagisaka, M.; Okita, T.; Sekimura, N.; Garner, F.

    2007-01-01

    Full text of publication follows: Whereas most data on radiation-induced changes in mechanical properties or dimensional stability needed for fusion - relevant dpa levels and dpa rates are generated at relatively high neutron flux in fast reactors, many fusion and fission components will operate at much lower dpa rates. Much less data are available from long-lived structural components operating at very low flux levels. In addition most published data were generated from relatively thin specimens (∼1-2 mm or less), while some actual fusion structural components can be on the order of 1-2 cm thick. In this study we have examined a 9 cm diameter pipe constructed from Fe-18Cr-9Ni steel analogous to AISI 304 that stayed outside the core of BN-600 for 22 years. The walls of the pipe were 2 cm thick and experienced temperatures in the range 370-375 deg. C. The walls were sectioned into 5 slices at a number of positions to yield doses in the range 1.5 to 22 dpa at 3 x 10 -9 to 4 x 10 -8 dpa/s. Changes in elastic moduli were studied using an ultrasonic technique and changes in electrical resistivity and mechanical properties of the 18Cr9Ni austenitic steel was examined. Swelling was measured both by immersion density and electron microscopy, reaching a maximum of ∼3 %. Swelling appears to be accelerated somewhat at these lower dpa rates as observed in other recent studies. Tensile properties were also measured. Radiation-induced changes of electrical resistivity, Young's and shear moduli were observed but did not agree fully with predictions based on voids alone. Strong contributions from second phase precipitates were found to be contributing to changes in both physical and mechanical properties. (authors)

  11. Tribological Properties of HVOF-Sprayed TiB2-NiCr Coatings with Agglomerated Feedstocks

    Science.gov (United States)

    Zhao, Zichun; Li, Hui; Yang, Tianlong; Zhu, Hongbin

    2018-04-01

    Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB2-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni20Ti3B6) derived from the reaction between TiB2 and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB2-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB2, CrB, and the binder phase. No evidence of Ni20Ti3B6 phase was found in the coating. The mechanical properties of HVOF-sprayed TiB2-NiCr coating were comparable to the conventional Cr3C2-NiCr coating. The frictional coefficient of the TiB2-NiCr coating was lower than the Cr3C2-NiCr coating when sliding against a bearing steel ball.

  12. Tribological Properties of HVOF-Sprayed TiB2-NiCr Coatings with Agglomerated Feedstocks

    Science.gov (United States)

    Zhao, Zichun; Li, Hui; Yang, Tianlong; Zhu, Hongbin

    2018-03-01

    Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB2-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni20Ti3B6) derived from the reaction between TiB2 and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB2-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB2, CrB, and the binder phase. No evidence of Ni20Ti3B6 phase was found in the coating. The mechanical properties of HVOF-sprayed TiB2-NiCr coating were comparable to the conventional Cr3C2-NiCr coating. The frictional coefficient of the TiB2-NiCr coating was lower than the Cr3C2-NiCr coating when sliding against a bearing steel ball.

  13. Laves-phase evolution during aging in 9Cr-1.8W-0.5Mo-VNb steel for USC power plants

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue, E-mail: wangxue2011@whu.edu.cn [School of Power and Mechanics, Wuhan University, Wuhan 430072 (China); Xu, Qiang [School of Computing and Engineering, The University of Huddersfield, Huddersfield HD1 3DH, England (United Kingdom); Yu, Shu-min; Hu, Lei [School of Power and Mechanics, Wuhan University, Wuhan 430072 (China); Liu, Hong [DongFang Boiler Group Co.,Ltd., Zigong 643001 (China); Ren, Yao-yao [School of Power and Mechanics, Wuhan University, Wuhan 430072 (China)

    2015-08-01

    Long term precipitation and coarsening of Laves-phase in tungsten strengthened 9% Cr steel under thermal aging at 923 K was investigated and reported in this paper. It experimentally measured the evolution of mean particle size, the number density, the volume fraction of Laves-phase precipitates, the partition coefficients of W and Mo in the matrix, as well as the change of hardness. Its main conclusions were: 1) Laves-phase nucleates and grows rapidly on grain boundaries and lath boundaries within the first 1500 h of aging time; 2) The two stages characteristics and kinetics of Laves-phase nucleation and growth which were determined experimentally; 3) The coarsening of Laves-phase is much faster than that of M{sub 23}C{sub 6} carbides; 4) The precipitation of Laves-phase produces a pronounced matrix depletion of W and Mo atoms; and 5) The precipitated Laves-phase gives rise to weaker precipitation strengthening in comparison with M{sub 23}C{sub 6} carbides, and causes the loss of hardness due to the depletion of Mo and W from the solid solution. This paper contributes to the knowledge of kinetics of Laves-phase precipitation and coarsening, providing the essential information for comparative investigation of creep damage mechanisms. This paper also contributes to the understanding the creep damage broadly. - Highlights: • The characteristics of precipitation and coarsening of Laves-phase were determined. • The matrix depletion of W and Mo due to Laves-phase precipitation was quantified. • The effect of precipitated Laves-phase on the hardness was evaluated.

  14. Residual creep life assessment by change of martensitic lath structure in modified 9Cr-1Mo steels

    International Nuclear Information System (INIS)

    Sawada, Kota; Takeda, Masaaki; Maruyama, Kouichi; Komine, Ryuji; Nagae, Yuji

    1998-01-01

    Mod.9Cr-1Mo steel has a martensitic lath structure. Recovery of the lath structure takes place in the course of creep. Microstructural degradation due to the recovery results in the acceleration of creep rate and the subsequent failure of a specimen. Change of lath width during creep of the steel was quantitatively investigated to propose a residual life assessment methodology based on the recovery process. Since the steel was tempered at 1053 K, the lath structure is thermally stable at the testing temperatures (848 K - 923 K). However, recovery of lath structure readily takes place during creep, indicating that the recovery is induced by creep deformation. Lath width d increases with creep strain and saturates to a value d s determined by creep stress. The increase of d is faster at a higher stress and temperature. A normalized change in lath width, Δd/Δd s , was introduced to explain the variation of lath growth rate with creep stress and temperature. Δd is the change in lath width from the initial value d 0 , and Δd s is the difference between d s , and d 0 . Δd/Δd s is uniquely related to creep strain ε and the relationship is independent of creep stress as well as creep temperature. This Δd/Δd s -ε relationship obtained by an accelerated creep test at a higher temperature or stress is applicable to any creep condition including service conditions of engineering plants. Creep strain can be evaluated from the measurement of Δd/Δd s based on the Δd/Δd s -ε relationship. A creep curve under any creep condition can readily be calculated by creep data of the steel. Combining these information one can assess residual life of a structural component made of the steel. (author)

  15. Fabrication of Fe-Cr-Mo powder metallurgy steel via a mechanical-alloying process

    Science.gov (United States)

    Park, Jooyoung; Jeong, Gowoon; Kang, Singon; Lee, Seok-Jae; Choi, Hyunjoo

    2015-11-01

    In this study, we employed a mechanical-alloying process to manufacture low-alloy CrL and CrM steel powders that have similar specifications to their water-atomized counterparts. X-ray diffraction showed that Mo and Cr are alloyed in Fe after four cycles of planetary milling for 1 h at 150 RPM with 15-min pauses between the cycles (designated as P2C4 process). Furthermore, the measured powder size was found to be similar to that of the water-atomized counterparts according to both scanning electron microscope images and laser particle size analysis. The samples were sintered at 1120 °C, after which the P2C4-milled CrL showed similar hardness to that of water-atomized CrL, whereas the P2C4-milled CrM showed about 45% lower hardness than that of its water-atomized counterpart. Water-atomized CrM consists of a well-developed lathtype microstructure (bainite or martensite), while a higher fraction of polygonal ferrite is observed in P2C4-milled CrM. This phase difference causes the reduction of hardness in the P2C4-milled CrM, implying that the phase transformation behavior of specimens produced via powder metallurgy is influenced by the powder fabrication method.

  16. Ordering in rapidly solidified Ni/sub 2/Mo

    International Nuclear Information System (INIS)

    Kulkarni, U.D.; Dey, G.K.; Banerjee, S.

    1988-01-01

    Ordering processes in the Ni-Mo system have been a subject of several investigations. Although the ordering behaviour of the Ni/sub 4/Mo and the Ni/sub 3/Mo has been examined in detail, no such study has been reported in the case of the Ni/sub 2/Mo alloy. The lack of experimental work on ordering transformations in Ni/sub 2/Mo is presumably due to the difficulty in obtaining a single phase fcc alloy of this composition. Enhanced solid solubility of Mo in Ni, which accompanies rapid solidification processing (RSP) makes the formation of such a phase possible. The ordering processes in Ni-Mo based alloys show several remarkable features. Firstly, the alloy (15 - 28 at % Mo) quenched from the α -phase filed exhibit a short range order (SRO) characterized by the presence of intensity maxima at /1 1/2 0/ fcc positions of the reciprocal space. This state of SRO has been attributed to the occurrence of 1 1/2 O spinodal ordering in the system. Secondly, the transformation from the state of SRO to the equilibrium/metastable coherent long range ordered (LRO) structures appears to take place in a continuous manner at relatively low temperatures of aging. Three different coherent LRO structures, namely: the equilibrium Ni/sub 4/Mo (prototype structure D1/sub a/) and the metastable Ni/sub 3/Mo (DO/sub 22/) and Ni/sub 2/Mo (Pt/sub 2/Mo) structures have reported to evolve from the SRO alloy, depending upon the aging treatment and the composition of the alloy

  17. Microstructural defect evolution in neutron – Irradiated 12Cr18Ni9Ti stainless steel during subsequent isochronous annealing

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, K.V.; Maksimkin, O.P.; Turubarova, L.G.; Rofman, O.V. [Institute of Nuclear Physics NNC RK, Almaty (Kazakhstan); Garner, F.A., E-mail: frank.garner@dslextreme.com [Radiation Effects Consulting, Richland, WA (United States)

    2013-08-15

    Transmission electron microscopy and microhardness measurements were used to examine changes in microstructure and associated strengthening induced in austenitic stainless steel 12Cr18Ni9Ti irradiated to ∼0.001 and ∼5 dpa in the WWR-K reactor before and after being subjected to post-irradiation isochronal annealing. The relatively low values of irradiation temperature and dpa rate (∼80 °C and ∼1.2 × 10{sup −8} dpa/s) experienced by this steel allowed characterization of defect microstructures over a wide range of defect ensembles, all at constant composition, produced first by irradiation and then by annealing at temperatures between 450 and 1050 °C. It was shown that the dispersed barrier hardening model with commonly accepted physical properties successfully predicted the observed hardening. It was also observed that when TiC precipitates form at higher annealing temperatures, the alloy does not change in hardness, reflecting a balance between precipitate-hardening and matrix-softening due to removal of solute-strengthening elements titanium and carbon. Such matrix-softening is not often considered in other studies, especially where the contribution of precipitates to hardening is a second-order effect.

  18. Microstructural defect evolution in neutron – Irradiated 12Cr18Ni9Ti stainless steel during subsequent isochronous annealing

    International Nuclear Information System (INIS)

    Tsay, K.V.; Maksimkin, O.P.; Turubarova, L.G.; Rofman, O.V.; Garner, F.A.

    2013-01-01

    Transmission electron microscopy and microhardness measurements were used to examine changes in microstructure and associated strengthening induced in austenitic stainless steel 12Cr18Ni9Ti irradiated to ∼0.001 and ∼5 dpa in the WWR-K reactor before and after being subjected to post-irradiation isochronal annealing. The relatively low values of irradiation temperature and dpa rate (∼80 °C and ∼1.2 × 10 −8 dpa/s) experienced by this steel allowed characterization of defect microstructures over a wide range of defect ensembles, all at constant composition, produced first by irradiation and then by annealing at temperatures between 450 and 1050 °C. It was shown that the dispersed barrier hardening model with commonly accepted physical properties successfully predicted the observed hardening. It was also observed that when TiC precipitates form at higher annealing temperatures, the alloy does not change in hardness, reflecting a balance between precipitate-hardening and matrix-softening due to removal of solute-strengthening elements titanium and carbon. Such matrix-softening is not often considered in other studies, especially where the contribution of precipitates to hardening is a second-order effect

  19. 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...

  20. Microstructural changes due to laser peening in modified 9Cr-1Mo steel subjected to creep damage at 823K and 923K in air

    International Nuclear Information System (INIS)

    Nakasone, Yuji; Kizuki, Yuta; Suzuki, Hayao; Minowa, Takuya

    2013-01-01

    The present study has investigated microstructural changes due to laser peening in modified 9Cr-1Mo steel subjected to creep. The EBSD or Electron Backscatter Diffraction studies have been made on round-bar type specimens creeping at applied stresses of 230 and 240 MPa at 823 K and 105 MPa at 923K in air. Prior to the creep tests, laser peening was applied to specimens at laser power of 8.4-22GW/cm 2 per pulse in water. Microstructural change in each specimen after its creep test was investigated by EBSD/SEM. The EBSD/SEM analyses revealed that the laser peening treatment makes creep rupture time longer and it reveals local misorientation value for rupture. (author)

  1. Chemical diffusion of Cr, Ni and Si in welded joints. II

    International Nuclear Information System (INIS)

    Kucera, J.; Ciha, K.

    1987-01-01

    The results are given of a study in chemical diffusion in welded joints P2/A and P3/A. P2 stands for the steel (Fe-17.48 Cr-8.15 Ni-0.14 Si), P3 for (Fe-18.52 Cr-8.20 Ni-1.78 Si) and A for the Fe-Arema. Triadic sandwiche-like samples were diffusion heated at temperatures from 920 to 1170 degC. The concentration distributions N(x,t) of the given elements were measured with microprobe JXA-3A. The evaluation of the experimental data was carried out either by Grube's method, or in some cases by the spline-polynomial method. The evaluated diffusivities D-bar satisfy the Arrhenius relation and yield the standard diffusion characteristics D 0 and H. The diffusivities D-bar of Cr, Ni and Si in P1/A, in P2/A and P3/A welded joints vary with Si content in P1, P2 and P3 alloys, similar to the Cr-51 and Ni-63 self-diffusivities in Fe-18 Cr-12 Ni-X Si steels, and tend to increase with increasing Si content. The values D-bar measured in the vicinity of grain boundaries are higher than the bulk diffusion coefficients. The most rapid diffusant is Si and the slowest one Ni. Thus, the relations D-bar Si :D-bar Cr :D-bar Ni ≅ 6:3:1 (P3/A) and D-bar Si :D-bar Cr :D-bar Ni ≅ 1.7:1.4:1 (P3/A) are valid at 1050 degC. Comparing the results with those published if can be noted that the Cr-51 and Ni-63 self-diffusion in Fe-18 Cr-12 Ni-X Si steels is faster than chemical diffusion of these elements in the said steel welded joints P2/A and P3/A; X varies from 0.14 to 1.98. (author). 7 tabs., 7 figs., 20 refs

  2. Microstructural, mechanical and tribological investigation of 30CrMnSiNi2A ultra-high strength steel under various tempering temperatures

    Science.gov (United States)

    Arslan Hafeez, Muhammad; Farooq, Ameeq

    2018-01-01

    The aim of the research was to investigate the variation in microstructural, mechanical and tribological characteristics of 30CrMnSiNi2A ultra-high strength steel as a function of tempering temperatures. Steel was quenched at 880 °C and tempered at five different tempering temperatures ranging from 250 °C to 650 °C. Optical microscopy and pin on disc tribometer was used to evaluate the microstructural and wear properties. Results show that characteristics of 30CrMnSiNi2A are highly sensitive to tempering temperatures. Lathe and plate shaped martensite obtained by quenching transform first into ε-carbide, second cementite, third coarsened and spheroidized cementite and finally into recovered ferrite and austenite. Hardness, tensile and yield strengths decreased while elongation increased with tempering temperatures. On the other hand, wear rate first markedly decreased and then increased. Optimum amalgamation of characteristics was achieved at 350 °C.

  3. Effect of nitrogen alloying of stainless steels on their corrosion stability

    International Nuclear Information System (INIS)

    Chigal, V.; Knyazheva, V.M.; Pitter, Ya.; Babich, S.G.; Bogolyubskij, S.D.

    1986-01-01

    Results of corrosion tests and structural investigations of 03Cr18Ni10 and 03Cr18Ni10Mo3 steels without nitrogen and with nitrogen content of 0.15-0.3% are presented. Corrosion-electrochemical behaviour of Cr20Ni20 steel with ultralow carbon content (0.004-0.006%) and nitrogen content with 0-0.5% as well as Cr 2 N nitride behaviour are investigated. A conclusion is made on nitrogen and excessive nitride phase effect on corrosion stability of steel in corrosive media with different reduction-oxidation properties

  4. Corrosion Study of Super Ferritic Stainless Steel UNS S44660 (26Cr-3Ni-3Mo) and Several Other Stainless Steel Grades (UNS S31603, S32101, and S32205) in Caustic Solution Containing Sodium Sulfide

    Science.gov (United States)

    Chasse, Kevin R.; Singh, Preet M.

    2013-11-01

    Electrochemical techniques, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used in this study to show how the corrosion mechanism of several commercial grades of stainless steel in hot caustic solution is strongly influenced by the presence of sodium sulfide. Experimental results from super ferritic stainless steel UNS S44660 (26Cr-3Ni-3Mo) were compared to austenitic stainless steel UNS S31603, lean duplex stainless steel (DSS) UNS S32101, and standard DSS UNS S32205 in caustic solution, with and without sodium sulfide, at 443 K (170 °C). Weight loss measurements indicated that corrosion rates of UNS44660 were much lower than the other grades of stainless steel in the presence of the sodium sulfide. Potentiodynamic polarization and linear polarization resistance measurements showed that the electrochemical behavior was altered by the adhesion of sulfur species, which reduced the polarization resistances and increased the anodic current densities. SEM and XPS results imply that the surface films that formed in caustic solution containing sodium sulfide were defective due to the adsorption of sulfide, which destabilized the passive film and led to the formation of insoluble metal sulfide compounds.

  5. Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

    Science.gov (United States)

    Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

    2017-06-01

    Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

  6. Fractographic examination of HT-9 and 9Cr-1Mo Charpy specimens irradiated in the AD-2 test

    International Nuclear Information System (INIS)

    Gelles, D.S.; Hu, W.L.

    1983-01-01

    Fracture surface topologies have been examined using scanning electron microscopy for 20 selected half sized Charpy impact specimens of HT-9 and Modified 9Cr-1Mo in order to provide improved understanding of fracture toughness degradation as a result of irradiation for Path E alloys. The specimen matrix included unirradiated specimens and specimens irradiated in EBR-II in the AD-2 experiment. Also, hardness measurements have been made on selected irradiated Charpy specimens. The results of examinations indicate that irradiation hardening due to G-phase formation at 390 0 C is responsible for the large shift in ductile-to-brittle transition temperature (DBTT) found in HT-9. Toughness degradation in HT-9 observed following higher temperature irradiations is attributed to precipitation at delta ferrite stringers. Reductions in toughness as a consequence of irradiation in Modified 9Cr-1Mo are attributed to in-reactor precipitation of (V,Nb)C and M 23 C 6 . It is shown that crack propagation rates for ductile and brittle failure modes can be measured, that they differ by over an order of magnitude and that unexpected multiple shifts in fracture mode from ductile to brittle failure can be attributed to the effect of delta ferrite stringers on crack propagation rates

  7. Development of Cr3C2-25(Ni20Cr) nanostructured coatings

    International Nuclear Information System (INIS)

    Cunha, Cecilio Alvares da

    2012-01-01

    This study is divided in two parts. The first part is about the preparation of nanostructured Cr 3 C 2 -25(Ni20Cr) powders by high energy milling followed by characterization of the milled and the as received powder. Analyses of some of the data obtained were done using a theoretical approach. The second part of this study is about the preparation and characterization of coatings prepared with the nanostructured as well as the as received Cr 3 C 2 -25(Ni20Cr) powders. The high temperature erosion-oxidation (E-O) behavior of the coatings prepared with the two types of powders has been compared based on a technological approach. The average crystallite size of the Cr 3 C 2 -25(Ni20Cr) powder decreased rapidly from 145 nm to 50 nm in the initial stages of milling and thereafter decreased slowly to a steady state value of around 10 nm with further increase in milling time. This steady state corresponds to the beginning of a dynamic recovery process. The maximum lattice strain (ε = 1,17%) was observed in powders milled for 16 hours, and this powders critical crystallite size was 28 nm. In contrast, the lattice parameter attained a minimum for powders milled for 16 hours. Upon reaching the critical crystallite size, the dislocation density attained a steady state regime and all plastic deformation introduced in the material there after was in the form of events occurring at the grain boundaries, due mainly to grain boundary sliding. The deformation energy stored in the crystal lattice of the Cr 3 C 2 -25(Ni20Cr) powders milled for different times was determined from enthalpy variation measurements. These results indicated that the maximum enthalpy variation (δH = 722 mcal) also occurred for powders milled for 16 hours. In a similar manner, the maximum specific heat variation (δC p = 0,278 cal/gK) occurred for powders milled for 16 hours. The following mechanical properties of Cr 3 C 2 -25(Ni20Cr) coatings prepared using the HVOF thermal spray process were determined

  8. Precipitation process of Z-phase in 9-12%CR steels

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson

    2014-01-01

    Precipitation of Z-phase, Cr(V,Nb)N, is known to negatively affect creep properties of 9-12%Cr steels for power plant applications as it dissolves finely distributed MX particles, (V,Nb)N, especially in high Cr steels. As the Z-phase precipitates slowly as large particles, this causes a net drop ...... and crystallographically into Z-phase CrTaN particles. Copyright © 2014 Electric Power Research Institute, Inc. Distributed by ASM International®. All rights reserved....

  9. Structure of Oxide Nanoparticles in Fe-16Cr MA/ODS Ferritic Steel

    Energy Technology Data Exchange (ETDEWEB)

    Hsiung, L; Fluss, M; Kimura, A

    2010-04-06

    Oxide nanoparticles in Fe-16Cr ODS ferritic steel fabricated by mechanical alloying (MA) method have been examined using high-resolution transmission electron microscopy (HRTEM) techniques. A partial crystallization of oxide nanoparticles was frequently observed in as-fabricated ODS steel. The crystal structure of crystalline oxide particles is identified to be mainly Y{sub 4}Al{sub 2}O{sub 9} (YAM) with a monoclinic structure. Large nanoparticles with a diameter larger than 20 nm tend to be incoherent and have a nearly spherical shape, whereas small nanoparticles with a diameter smaller than 10 nm tend to be coherent or semi-coherent and have faceted boundaries. The oxide nanoparticles become fully crystallized after prolonged annealing at 900 C. These results lead us to propose a three-stage formation mechanism of oxide nanoparticles in MA/ODS steels.

  10. Effect of composition on corrosion resistance of high-alloy austenitic stainless steel weld metals

    International Nuclear Information System (INIS)

    Marshall, P.I.; Gooch, T.G.

    1993-01-01

    The corrosion resistance of stainless steel weld metal in the ranges of 17 to 28% chromium (Cr), 6 to 60% nickel (Ni), 0 to 9% molybdenum (Mo), and 0.0 to 0.37% nitrogen (N) was examined. Critical pitting temperatures were determined in ferric chloride (FeCl 3 ). Passive film breakdown potentials were assessed from potentiodynamic scans in 3% sodium chloride (NaCl) at 50 C. Potentiodynamic and potentiostatic tests were carried out in 30% sulfuric acid (H 2 SO 4 ) ar 25 C, which was representative of chloride-free acid media of low redox potential. Metallographic examination and microanalysis were conducted on the test welds. Because of segregation of alloying elements, weld metal pitting resistance always was lower than that of matching composition base steel. The difference increased with higher Cr, Mo, and N contents. Segregation also reduced resistance to general corrosion in H 2 SO 4 , but the effect relative to the base steel was less marked than with chloride pitting. Segregation of Cr, Mo, and N in fully austenitic deposits decreased as the Ni' eq- Cr' eq ratio increased. Over the compositional range studied, weld metal pitting resistance was dependent mainly on Mo content and segregation. N had less effect than in wrought alloys. Both Mo and N enhanced weld metal corrosion resistance in H 2 SO 4

  11. Microstructural changes during creep and life assessment of Mod.9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Sawada, Kota; Maruyama, Kouichi; Komine, Ryuji; Nagae, Yuji.

    1997-01-01

    Several microstructural changes take place in a material during the course of creep. These changes can be a measure of creep life. In this paper, microstructural changes in Mod.9Cr-1Mo steel were studied and it was examined which is a good measure of creep life. Microscopic structural changes, such as void growth, lath structure uniformly oriented to the tensile axis and elongation of grains, are evident only in the necked portion of ruptured specimens. These macroscopic structural changes are not useful for creep life assessment. Lath width increases and dislocation density within lath decreases with increasing creep duration. These changes in dislocation substructure start in the early stage of creep life, and cause the increase of strain rate in the tertiary creep stage. The lath width and the dislocation density reach a saturated value before rupture. The saturated values are independent of temperature, and uniquely related to creep stress normalized by shear modulus. The extent of these microstructural changes are greater at lower stresses under which the material is practically used. These facts suggest that the lath width and the dislocation density within lath can be a useful measure of creep life. Hardness of crept specimens is closely related to the lath width and the dislocation density within lath. The changes of these microstructural features can be evaluated by the measurement of hardness. (author)

  12. Resistivity, hysteresis, and magnetization of 9% Cr stainless steel as a function of temperature and its electromagnetic shielding effects in cylindrical structures

    International Nuclear Information System (INIS)

    Praeg, W.F.

    1979-01-01

    Ferromagnetic stainless steels may offer significantly greater wall life-times for first wall/blanket and vacuum vessel structures than commonly used non-magnetic stainless steels. One steel under consideration has the following composition, in wt %, Fe(86.24), Cr(9), Mo(2), Mn(1), Si(0.75), Nb(0.50), V(0.30), C(0.15), P(0.3), S(0.30). There appears to be no literature on the electromagnetic properties of this material. Therefore, the resistivity, the hysteresis loops, and magnetization were measured as a function of temperature up to the Curie point

  13. Degradation of mechanical properties of CrMo creep resistant steel operating under conditions of creep

    Directory of Open Access Journals (Sweden)

    J. Michel

    2012-01-01

    Full Text Available Mechanical properties of a steam tube made of CrMo creep resistant steel are analysed in this contribution after up to 2,6•105 hours service life in creep conditions at temperature 530 °C and calculated stress level in the tube wall 46,5 MPa. During service life there were in the steel gradual micro structure changes, fi rst pearlite spheroidization, precipitation, coaugulation and precipitate coarsening. Nevertheless the strength and deformation properties of the steel (Re, Rm, A5, Z, and the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2,1•105 hours in service. The steam tube is now in service more than 2,6•105 h.

  14. Structure of Fe-Ni-Cr steel welded joints

    International Nuclear Information System (INIS)

    Bratukhin, A.G.; Maslenkov, S.B.; Logunov, A.V.

    1993-01-01

    Properties of a welded joint depend on the structure of metal of the joint and near the joint areas subjected to thermal effect in the process of welding. The well-known phenomena, accompanying the welding (grain growth in near the joint area, intergrain slip, stressed state related to crystallization and rapid cooling), as well as certain other processes, which have been insufficiently studied either due to their poor pronouncement or owing to imperfection of the equipment and methods employed, were analyzed, as applied to stainless hihg-strength Fe-Ni-Cr steels

  15. Research on 16Mo3 (16M Steel Pipes Overlaid with Haynes Nicro625 Alloy Using MIG (131 Method / Badania Rur Ze Stali 16Mo3 (16M Napawanych Metodą MIG (131 Stopem Haynes Nicro625

    Directory of Open Access Journals (Sweden)

    Golański G.

    2015-12-01

    Full Text Available The paper presents the research on the microstructure and mechanical properties of a pipe made of 16Mo3 steel, overlaid with superalloy based on Haynes NiCro625 nickel. The overlay weld was overlaid using the MIG (131 method. The performed macro - and microscopic tests have shown the correct structure of the overlay weld without any welding unconformities. The examined overlay weld was characterized by a dendritic structure of the primary crystals accumulating towards the heat removal. It has been proved that the content of iron in the surface zone does not exceed 7%, and the steel-superalloy joint shows the highest properties in comparison with the materials joined.

  16. Phase transformation and tribological properties of Ag-MoO3 contained NiCrAlY based composite coatings fabricated by laser cladding

    Science.gov (United States)

    Wang, Lingqian; Zhou, Jiansong; Xin, Benbin; Yu, Youjun; Ren, Shufang; Li, Zhen

    2017-08-01

    Ag-MoO3 contained NiCrAlY based composite coating was successfully prepared on GH4169 stainless steel substrate by high energy ball milling and laser cladding. The microstructure and phase transformation were investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction spectrum (XRD). The tribological behavior and mechanism from room temperature to 800 °C were investigated. Results showed that MoO3 in the composite powders transformed to Mo2C reinforcement under the high energy density of laser, and a series of opposite transformation occurred during friction process. The coating showed the lowest friction coefficient and low wear rate at 600 °C and 800 °C due to the generation of Ag2MoO4 during tribo-chemical reactions and the formation of lubrication glaze on the worn surface. Ag made effective lubrication when the temperature rose up to 200 °C. The coating displayed a relatively high friction coefficient (about 0.51) at 400 °C, because though MoO3 (oxidation products of Mo2C) and Ag2MoO4 were detected on the worn surface, they could not realize effective lubrication at this temperature. Abrasive wear, adhesive wear and plastic deformation contributed to the increased friction and wear.

  17. Design of aging-resitant martensitic stainless steels for pressurized water reactors

    International Nuclear Information System (INIS)

    Cozar, R.; Meyzaud, Y.

    1983-06-01

    With the exception of AISI 403 or 410 grades, the use of high strength martensitic stainless steels in PWR is poorly developped because these materials, like ferritic stainless steels, become embrittled by the precitation of a b.c.c. chromium-rich phase during aging at the operating temperature (290 to 350 0 C). The influence of alloying elements and microstructure on the aging behavior of forged low-carbon martensitic stainless steels containing 12 to 16% Cr, 0 to 2% Mo and 0 to 8% Ni was determined during accelerated aging at 450 0 C. Quantitative relationships were derived between the maximum increase in hardness, the maximum shift in CVN transition temperature and the chemical composition (Cr, Mo, C) and microstructure

  18. Impurity Antimony-Induced Creep Property Deterioration and Its Suppression by Rare Earth Ceriumfor a 9Cr-1Mo Ferritic Heat-Resistant Steel

    Directory of Open Access Journals (Sweden)

    Yewei Xu

    2016-08-01

    Full Text Available The high temperature creep properties of three groups of modified 9Cr-1Mo steel samples, undoped, doped with Sb, and doped with Sb and Ce, are evaluated under the applied stresses from 150 MPa to 210 MPa and at the temperatures from 873–923 K. The creep behavior follows the temperature-compensated power law as well as the Monkman-Grant relation. The creep activation energy for the Sb-doped steel (519 kJ/mol is apparently lower than that for the undoped one (541 kJ/mol, but it is considerably higher for the Sb+Ce-doped steel (621 kJ/mol. Based on the obtained relations, both the creep lifetimes under 50 MPa, 80 MPa, and 100 MPa in the range 853–923 K and the 105 h creep rupture strengths at 853 K, 873 K, and 893 K are predicted. It is demonstrated that the creep properties of the Sb-doped steel are considerably deteriorated but those of the Sb+Ce-doped steel are significantly improved as compared with the undoped steel. Microstructural and microchemical characterizations indicate that the minor addition of Ce can stabilize the microstructure of the steel by segregating to grain boundaries and dislocations, thereby offsetting the deleterious effect of Sb by coarsening the microstructure and weakening the grain boundary.

  19. Mechanical properties data of 2-1/4Cr-1Mo steel for the experimental very high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Oku, Tatsuo; Kikuyama, Toshihiko; Fukaya, Kiyoshi; Kodaira, Tsuneo

    1978-11-01

    This is a collection of mechanical properties data of 2-1/4Cr-1Mo steel necessary for structural design and safety analysis of the pressure vessel of the Experimental Very High Temperature Gas-Cooled Reactor (VHTR). These include physical properties, mechanical properties, temper embrittlement, creep with fatigue, fracture toughness and irradiation effects. A review of the data shows the research areas to be carried out particularly in the future for more data. (author)

  20. The creep and stress-rupture behaviour under internal pressure of tubes made from austenitic stainless steel X8 CrNiMoNb 1616 (Material No. 1.4981)

    International Nuclear Information System (INIS)

    Schaefer, L.; Polifka, F.; Kempe, H.

    1979-05-01

    Creep and stress rupture tests have been performed at 600, 650, 700 and 750 0 C on tubes made from three different heats from the austenitic stainless steel X8 CrNiMoNb 1616 (Material No. 1.4981). The tubes were loaded by internal pressure and the tangential (hoop) creep strain was measured continuously. The results are presented in form of creep curves, stress-time to rupture curves and curves for a creep limit. The average and minimum creep rates as a function of the applied stress have been evaluated and are described with a creep law analogous to Norton's creep law. An interpolation and extrapolation of the stress-rupture-strength and the creep strength are possible using the time-temperature-parameter-plot after Larson and Miller. (orig.) [de

  1. Study of mechanical properties and high temperature oxidation behavior of a novel cold-spray Ni-20Cr coating on boiler steels

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Narinder [Semiconductor Materials and Device Laboratory, Department of Semiconductor Science, Dongguk University-Seoul, Seoul 100715 (Korea, Republic of); Kumar, Manoj [School of Mechanical, Materials & Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab (India); Sharma, Sanjeev K.; Kim, Deuk Young [Semiconductor Materials and Device Laboratory, Department of Semiconductor Science, Dongguk University-Seoul, Seoul 100715 (Korea, Republic of); Kumar, S.; Chavan, N.M.; Joshi, S.V. [International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI), Hyderabad 500005 (India); Singh, Narinder [Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar, Punjab (India); Singh, Harpreet, E-mail: harpreetsingh@iitrpr.ac.in [School of Mechanical, Materials & Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab (India)

    2015-02-15

    Highlights: • A presynthesized Ni-20Cr nanocrystalline powder was successfully deposited on T22 and SA 516 boilers steels using cold spray process. • The coatings are observed to have more than 2-folds microhardness in comparison with the base steels. • The coating was successful in reducing the weight gain of T22 and SA 516 steel by 71% and 94%. - Abstract: In the current investigation, high temperature oxidation behavior of a novel cold-spray Ni-20Cr nanostructured coating was studied. The nanocrystalline Ni-20Cr powder was synthesized by the investigators using ball milling, which was deposited on T22 and SA 516 steels by cold spraying. The crystallite size based upon Scherrer's formula for the developed coatings was found to be in nano-range for both the substrates. The accelerated oxidation testing was performed in a laboratory tube furnace at a temperature 900 °C under thermal cyclic conditions. Each cycle comprised heating for one hour at 900 °C followed by cooling for 20 min in ambient air. The kinetics of oxidation was established using weight change measurements for the bare and the coated steels. The oxidation products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and X-ray mapping techniques. It was found from the results that the coating was successful in reducing the weight gain of SA213-T22 and SA 516-Grade 70 steel by 71% and 94%, respectively. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the coating. Moreover, the developed nano-structured Ni-20Cr powder coating was found to perform better than its counterpart micron-sized Ni-20Cr powder coating, in terms of offering higher oxidation resistance and hardness.

  2. Chemical reduction of rust on 2 1/4 Cr-1 Mo steel surface in sodium

    International Nuclear Information System (INIS)

    Yokota, N.; Shimoyashiki, S.

    1986-01-01

    Low-alloy Fe-2 1/4 Cr-1 Mo ferritic steel has been favored for the tube material of steam generators in fast breeder reactors (FBRs). However, this material rusts easily due to moisture condensation on its surface when left in air. Therefore, measures to prevent tube materials from rusting have been taken during manufacturing of the steam generators. When rust is present on tube surfaces, its oxygen and iron dissolve into liquid sodium. When the concentration of these impurities in the sodium increases rapidly, the cold traps can become choked locally and lose their removal ability. This work has been done, therefore, to clarify reduction processes of rust in sodium and to select optimum operating temperatures of steam generators in the initial operation

  3. Ratchetting deformation behavior of modified 9Cr-1Mo steel and applicability of existing constitutive models

    International Nuclear Information System (INIS)

    Yaguchi, Masatsugu; Takahashi, Yukio

    2001-01-01

    A series of ratchetting deformation tests was conducted on modified 9Cr-1Mo steel at 550degC under uniaxial and multiaxial stress conditions. Ratchetting behavior depended on various parameters such as mean stress, stress/strain rate and those range, hold time and prior cyclic deformation. Under uniaxial conditions, untraditional ratchetting behavior was observed; the ratchetting deformation rate was the fastest when the stress ratio was equal to -1, while no ratchetting deformation was predicted by conventional constitutive models. In order to discuss the reason for this untraditional ratchetting behavior, a lot of monotonic compression tests were conducted and compared with tension data. The material showed a difference of deformation resistance of about 30 MPa between tension and compression at high strain rates. Furthermore, the authors' previous model and Ohno-Wang model were applied to the test conditions to evaluate their description capability for ratchetting behavior of the material. It was shown that the authors' model has a tendency to overestimate the ratchetting deformation and that the Ohno-Wang model has a tendency to underestimate the uniaxial ratchetting deformation at small stress rates. (author)

  4. Solute grain boundary segregation during high temperature plastic deformation in a Cr-Mo low alloy steel

    International Nuclear Information System (INIS)

    Chen, X.-M.; Song, S.-H.; Weng, L.-Q.; Liu, S.-J.

    2011-01-01

    Highlights: → The segregation of P and Mo is evidently enhanced by plastic deformation. → The boundary concentrations of P and Mo increase with increasing strain. → A model with consideration of site competition in grain boundary segregation in a ternary system is developed. → Model predictions show a reasonable agreement with the observations. - Abstract: Grain boundary segregation of Cr, Mo and P to austenite grain boundaries in a P-doped 1Cr0.5Mo steel is examined using field emission gun scanning transmission electron microscopy for the specimens undeformed and deformed by 10% with a strain rate of 2 x 10 -3 s -1 at 900 deg. C, and subsequently water quenched to room temperature. Before deformation, there is some segregation for Mo and P, but the segregation is considerably increased after deformation. The segregation of Cr is very small and there is no apparent difference between the undeformed and deformed specimens. Since the thermal equilibrium segregation has been attained prior to deformation, the segregation produced during deformation has a non-equilibrium characteristic. A theoretical model with consideration of site competition in grain boundary segregation between two solutes in a ternary alloy is developed to explain the experimental results. Model predictions are made, which show a reasonable agreement with the observations.

  5. Electrochemical characterisation of X10CrNi 18-8 steel in artificial plasma

    Directory of Open Access Journals (Sweden)

    J. Przondziono

    2015-01-01

    Full Text Available Quality of applied guide wires conditions the course of treatment and its success to a great extent. In order to simulate conditions that can be found in blood vascular system samples were exposed to artificial blood plasma (T = 37 } 1 oC for the time of 8 h. In order to obtain information regarding physical and chemical properties of modified surface of wire made of X10CrNi 18-8 steel, electrochemical impedance spectroscopy (EIS test and tests of chemical composition of the surface layer X-ray photoelectron spectroscopy (XPS were made. On the ground of performed EIS and XPS tests, favourable impact of steam sterilisation process on corrosion resistance of X10CrNi 18-8 steel was observed only for the case when chemical passivation was applied prior to sterilisation.

  6. Refinement of grain structure in 20 MnNiMo (SA508C) steel

    International Nuclear Information System (INIS)

    Sheng Zhongqi; Xiao Hong; Peng Feng; Zou Min

    1997-04-01

    The size of prior austenite grains and bainitic colonies of 20 MnNiMo (SA508C) steel (a reactor pressure vessel steel) after normal heat treatment is measured and its controlling factors are discussed. Results show that low aluminium content can induce serious mixed structure with fine and coarse grains in prior austenite. Fast cooling rate can promote refinement of bainitic colonies. Further refinement of grains can be obtained by inter-critical quenching. (5 figs., 1 tab.)

  7. Creep rupture properties of oxidised 20%Cr austenitic stainless steels

    International Nuclear Information System (INIS)

    Lobb, R.C.; Ecob, R.C.

    1989-02-01

    Sheet specimens of stabilised 20%Cr/25%Ni/Nb and nitrided 20%Cr/25%Ni/Ti stainless steels, both used as fuel cladding materials in CAGRs, have been oxidised in simulated reactor gas (Co 2 /1-2%CO) for up to l.9kh at 850 0 C, including intermediate thermal cycles to room temperature. The oxidised specimens have been creep tested subsequently at 750 0 C, under conditions of constant stress. The creep rupture properties are affected differently for the two materials. For 20%Cr/25%Ni/Nb stainless steel, there was no effect of oxidation on the intrinsic microstructure, when compared with thermally aged, non-oxidised material. Any differences in creep ductility were ascribed to geometric effects in specimens of this alloy. Lower ductilities were associated with an increased incidence of pitting attack (higher oxide spallation) and it was concluded that the extent of local, rather than general, loss of section controlled the ductility. For nitrided 20%Cr/25%Ni/Ti stainless steel, the intrinsic microstructure was affected by oxidation, such that increased grain boundary precipitation of M 23 C 6 occurred. The resultant effect was for a greater tendency for intergranular failure at lower ductility than for the thermally aged material. The magnitude of this reduction could not be quantified because the specimen geometry was also changed by oxidation. In this instance, the oxidation mode that produced the most severe loss of section was grain boundary, rather than pitting, attack. This mode of attack was not linked directly to oxide fracture/spallation, but to the period of oxidation. (author)

  8. The use of nitrogen to improve the corrosion resistance of FeCrNiMo alloys for the chemical process industries

    Energy Technology Data Exchange (ETDEWEB)

    Kearns, J.R.; Deverell, H.E.

    1987-06-01

    The addition of 0.1 to 0.25 wt% nitrogen to austenitic alloys has been shown to enhance resistance to localized corrosion in oxidizing chloride and reducing acid solutions. Further tests of FeCrNiMo alloys assess the effects of nitrogen additions on: mechanical properties, chloride and caustic stress corrosion cracking resistance, passivation characteristics, and general corrosion rates in various acid, alkali, and salt solutions pertinent to the chemical process industries. The precipitation of chromium-rich secondary phases was retarded by solid solution additions of 0.1 to 0.25 wt% nitrogen. The corrosion resistance of FeCrNiMoN alloys in the welded condition was improved by using shield-gas mixtures of argon and 2.5 to 5.0 wt% nitrogen.

  9. Effects of the phase fractions on the carbide morphologies, Charpy and tensile properties in SA508 Gr.4N High Strength Low Alloy RPV Steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    To improve the strength and toughness of RPV (reactor pressure vessel) steels for nuclear power plants, an effective way is the change of material specification from tempered bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel into tempered martensitic/bainitic SA508 Gr.4N Ni-Cr-Mo low alloy steel. It is known that the phase fractions of martensitic/bainitic steels are very sensitive to the austenitizing cooling rates. Kim reported that there are large differences of austenitizing cooling rates between the surface and the center locations in RPV due to its thickness of 250mm. Hence, the martensite/bainite fractions would be changed in different locations, and it would affect the microstructure and mechanical properties in Ni-Cr-Mo low alloy steel. These results may lead to inhomogeneous characteristics after austenitizing. Therefore, it is necessary to evaluate the changes of microstructure and mechanical properties with varying phase fractions in Ni-Cr-Mo low alloy steel. In this study, the effects of martensite/bainite fractions on microstructure and mechanical properties in Ni-Cr-Mo low alloy steel were examined. The changes in phase fractions of Ni-Cr-Mo low alloy steel with different cooling rates were analyzed, and then the phase fractions were correlated with its microstructural observation and mechanical properties

  10. Postirradiation notch ductility tests of ESR alloy HT-9 and modified 9Cr-1Mo alloy from UBR reactor experiments

    International Nuclear Information System (INIS)

    Hawthorne, J.R.

    1984-01-01

    During this period, irradiation exposures at 300 0 C and 150 0 C to approx. 8 x 10 19 n/cm 2 , E > 0.1 MeV, were completed for the Alloy HT-9 plate and the modified Alloy 9Cr-1Mo plates, respectively. Postirradiation tests of Charpy-V (C/sub v/) specimens were completed for both alloys; other specimen types included in the reactor assemblies were fatigue precracked Charpy-V (PCC/sub v/), half-size Charpy-V, and in the case of the modified 9Cr-1Mo, 2.54 mm thick compact tension specimens

  11. Development of Cr{sub 3}C{sub 2}-25(Ni20Cr) nanostructured coatings; Desenvolvimento de revestimentos nanostruturados de Cr{sub 3}C{sub 2}-25(Ni20Cr)

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, Cecilio Alvares da

    2012-07-01

    This study is divided in two parts. The first part is about the preparation of nanostructured Cr{sub 3}C{sub 2}-25(Ni20Cr) powders by high energy milling followed by characterization of the milled and the as received powder. Analyses of some of the data obtained were done using a theoretical approach. The second part of this study is about the preparation and characterization of coatings prepared with the nanostructured as well as the as received Cr{sub 3}C{sub 2}-25(Ni20Cr) powders. The high temperature erosion-oxidation (E-O) behavior of the coatings prepared with the two types of powders has been compared based on a technological approach. The average crystallite size of the Cr{sub 3}C{sub 2}-25(Ni20Cr) powder decreased rapidly from 145 nm to 50 nm in the initial stages of milling and thereafter decreased slowly to a steady state value of around 10 nm with further increase in milling time. This steady state corresponds to the beginning of a dynamic recovery process. The maximum lattice strain ({epsilon} = 1,17%) was observed in powders milled for 16 hours, and this powders critical crystallite size was 28 nm. In contrast, the lattice parameter attained a minimum for powders milled for 16 hours. Upon reaching the critical crystallite size, the dislocation density attained a steady state regime and all plastic deformation introduced in the material there after was in the form of events occurring at the grain boundaries, due mainly to grain boundary sliding. The deformation energy stored in the crystal lattice of the Cr{sub 3}C{sub 2}-25(Ni20Cr) powders milled for different times was determined from enthalpy variation measurements. These results indicated that the maximum enthalpy variation ({delta}H = 722 mcal) also occurred for powders milled for 16 hours. In a similar manner, the maximum specific heat variation ({delta}C{sub p} = 0,278 cal/gK) occurred for powders milled for 16 hours. The following mechanical properties of Cr{sub 3}C{sub 2}-25(Ni20Cr) coatings

  12. Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

    Directory of Open Access Journals (Sweden)

    Quanshun Luo

    2017-07-01

    Full Text Available Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 °C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed X-ray diffraction method has been employed to dissolve the bainitic/martensitic ferrite phase as two sub-phases of different tetragonal ratios, which provides quantitative analyses of the carbon partitioning between the resultant ferrites and the retained austenite. The results show that, a short-term austempering treatment was in the incubation period of the bainite transformation, which resulted in maximum hardness being equivalent to the oil-quenching treatment. The associated microstructure comprises fine carbide-free martensitic and bainitic ferrites of supersaturated carbon contents as well as carbon-rich retained austenite. In particular, the short-term austempering treatment helped prevent the formation of lengthy martensitic laths as those being found in the microstructure of oil-quenched sample. When the austempering time was increased from 20 to 80 min, progressive decrease of the hardness was associated with the evolution of the microstructure, including progressive coarsening of bainitic ferrite, carbide precipitating inside high-carbon bainitic ferrite and its subsequent decarbonisation.

  13. Effect of carbon content on microstructure and mechanical properties of hot-rolled low carbon 12Cr-Ni stainless steel

    International Nuclear Information System (INIS)

    Zheng, H.; Ye, X.N.; Li, J.D.; Jiang, L.Z.; Liu, Z.Y.; Wang, G.D.; Wang, B.S.

    2010-01-01

    Research highlights: → Hot-rolled ultra low carbon martensite is characterized by dislocation cells substructure. → The formation of dislocation cells is attributed to high Ms and low interstitial atoms content. → Hot-rolled ultra low carbon 12Cr-Ni stainless steel has excellent impact toughness. → Delta ferrite deteriorates the impact toughness of hot-rolled 12Cr-Ni stainless steel. - Abstract: 12Cr-Ni stainless steels containing different carbon contents from 0.004 wt.% to 0.034 wt.% were hot-rolled and air-cooled. Their corresponding microstructures were observed with optical microscope and transmission electron microscope, and the Vickers hardness, tensile and impact tests were also carried out. It was found that the martensitic morphology was significantly influenced by carbon content. The as-received ultra low carbon martensite in the steel containing 0.004 wt.% C is characterized by dislocation cells substructure. The formation of dislocation cells is attributed to high martensite finishing point (above 400 deg. C) and low interstitial atoms content. On the other hand, the martensite in the steel containing 0.034 wt.% C consists mainly of typical martensite laths because of low martensite finishing point and high interstitial atoms content which hinder dislocation motion. Furthermore, carbon content has an evident effect on the mechanical properties of 12Cr-Ni steels. The hardness and strength of the as-received steels increase with an increase in carbon content, but their elongation and impact toughness decrease with the carbon content. The steel containing 0.004 wt.% C has excellent impact toughness due to the ultra low carbon content in the martensite composed of dislocation cells.

  14. Changes of structure and properties of cast steels GX10NiCrNb32-20 and GX10NiCrNb3-25 after long-term tempering at 600-1000 C

    International Nuclear Information System (INIS)

    Gommans, R.; Schrijen, H.; Sundermann, J.; Steinkusch, W.; Hering, W.

    2001-01-01

    Low-alloy cast steels of type GX 10NiCrNb 32.20 are commonly used for the outlet section of reformer and cracker tubes for the temperature range of 600-1000 C. There was a lack of data on the ductility of the 25%Cr alloyed cast steel GX10NiCrNb 35.25 at room temperature after tempering, which was investigated in a joint project of Pose-Marre and DSM. Mechanical tests were carried out at room temperature and at elevated temperatures. Apart from light microscopy, also SEM/EDX, SAM and TEM analyses were carried out. The 25% alloy has lower ductility than the 20% alloy, owing primarily to the more pronounced development of M 6 C carbide from primary NbC carbide, which takes up Ni and Si during tempering. The microstructure and composition of the M 6 C carbide wre not fully clarified. Information is presented on the potential application of low-carbon materials of the type GX10NiCrNb35.25 [de

  15. Application of newly developed heat resistant materials for USC boilers

    International Nuclear Information System (INIS)

    Sato, T.; Tamura, K.; Fukuda, Y.; Matsuda, J.

    2004-01-01

    This paper describes the research on the development and improvement of new high strength heat resistant steels such as SUPER304H (18Cr-9Ni-3Cu-Nb-N), NF709 (20Cr-25Ni-1.5Mo-Nb-Ti-N) and HR3C (25Cr-20Ni-Nb-N) as boiler tube, and NF616 (9Cr-0.5Mo-1.8W-Nb-V) and HCM12A (11Cr-0.4Mo-2W-Nb-V-Cu) as thick section pipe. The latest manufacturing techniques applied for these steels are introduced. In addition the high temperature strength of Alloy617 (52Ni-22Cr-13Co-9Mo-Ti-Al) that is one of the candidate materials for the next generation 700 □ USC boilers is described. (orig.)

  16. Observations on thermally cycled 20% Cr/25% Ni/Nb stabilised stainless steel

    International Nuclear Information System (INIS)

    Lobb, R.C.

    1984-06-01

    A variety of optical and electron techniques, such as optical metallography, scanning electron microscopy and electron probe microanalysis, have been used to study the morphology and composition of oxides formed on 20 Cr/25 Ni/Nb stainless steel during oxidation at 850 0 C and subsequent thermal cycling in simulated reactor gas. (author)

  17. Cyclic and isothermal oxidation behavior of 2.25Cr-1Mo steel; Estudio del comportamiento del acero 2.25Cr-1Mo frente a los fenomenos de oxidacion ciclica e isoterma

    Energy Technology Data Exchange (ETDEWEB)

    Proy, M.; Utrilla, M. v.; Otero, E.

    2014-04-01

    Cyclic and isothermal oxidation of chromium-molybdenum steel 2.25Cr-1Mo were analyzed at 550 degree centigrade and 650 degree centigrade during 360 hours in air atmospheres. The cycles were performed with two stages; one of heating in furnace during 90 minutes and then the sample were cooled to 50 degree centigrade by air flow. Thermogravimetric analyses were performed to obtain high temperature corrosion kinetics. Several characterization techniques have been used to identify the corrosion mechanism, as X-Ray Diffraction (XRD), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). Thermal cycling tests can changes the corrosion mechanism, due cracks propagation in oxide scale, that witch can favors the access of oxidant agent to the substrate. (Author)

  18. Conversion of MX Nitrides to Modified Z-Phase in 9-12%Cr Ferritic Steels

    DEFF Research Database (Denmark)

    Cipolla, Leonardo

    for Z-phase formation was highlighted during the studies. Several 9-12%Cr commercial steels with prolonged high-temperature exposures have been investigated, too. The same mechanism of Z-phase formation observed in 12%Cr model alloys was identified in industrial 9-12%Cr steels after thousands of hours......The 9-12%Cr ferritic steels are extensively used in modern steam power plants at service temperature up to 620°C. Currently the best perform ing ferritic creep resistance steel is the ASTM Grade 92, whose high temperature strength has recently been assessed by European Creep Collaborative Committee...... in 2005 as 600°C/113MPa/10 5h. All previous attempts made in the last twenty years to develop ferritic steels for 650°C applications have failed due to the incapacity to combine the superior oxidation resistance, given by 12%Cr content, with excellent creep resistance of high-alloyed ferritic steels...

  19. Wastage Behavior of Modified 9Cr-1Mo Steel Tube Material by Sodium-Water Reaction

    International Nuclear Information System (INIS)

    Jeong, Ji Young; Kim, Jong Man; Kim, Tae Joon; Choi, Jong Hyeun; Kim, Byung Ho; Park, Nam Cook

    2009-01-01

    The development of a sodium-heated steam generator with safety and reliability is an essential requirement from the viewpoint of the economic efficiency of a sodium-cooled fast reactor. In most cases, these steam generators, which are in the process of development or operating, are of a shell-in tube type, with a high pressure water/steam inside the tubes and low pressure sodium on the shell-side, with a single wall tube as a barrier between these fluids. Therefore, if there is a hole or a crack in a heat transfer tube, a leakage of water/steam into the sodium may occur, resulting in a sodium-water reaction. When such a leak occurs, so-called 'wastage' is the result which may cause damage to or a failure of the adjacent tubes. If a steam generator is operated for some time in this condition, it is possible that it might create an intermediate leak state which would then give rise to the problems of a multi-target wastage in a very short time. Therefore, it is very important to predict these phenomena quantitatively from the view of designing a steam generator and its leak detection systems. The objective of this study is a basic investigating of the sodium-water reaction phenomena by small water/steam leaks. For this, wastage tests for modified 9Cr-1Mo steel were conducted

  20. Evaluation of creep residual life for modified 9Cr-1Mo steel based on Omega method

    International Nuclear Information System (INIS)

    Nonaka, Isamu; Torihata, Shoji; Kihara, Shigemitu; Umaki, Hideo; Maruyama, Kouichi.

    1997-01-01

    In order to study the accuracy of creep residual life prediction by the Omega method which is based on creep deformation, a series of creep tests on modified 9Cr-1Mo steel were conducted at 500degC, 550degC and 600degC, and the Omega method was applied to the residual life estimation. The main results obtained are as follows: (1) There was a obvious linear portion, which corresponded to the tertiary creep, in the relationship between logarithm of strain and strain. So it was easy to define the Omega value as a gradient of linear portion. (2) It was proved that the Omega value depended on stress and temperature in such a way as it was the larger, the lower the stress and the lower the temperature. (3) By using the Omega value and strain rate which were determined experimentally, the residual life could be predicted within a factor of 1.5 at the stage of 50% and 80% of actual life. It was confirmed that the accuracy of this method was higher than that of the former method based on rupture time. (4) To apply this method to the residual life evaluation of operating plant materials, the Omega value has to be determined in the lower stress condition. So it is important to develop the extrapolation method of the Omega value based on the laboratory acceleration test to the longer service life. (author)

  1. Quality of Metal Deposited Flux Cored Wire With the System Fe-C-Si-Mn-Cr-Mo-Ni-V-Co

    Science.gov (United States)

    Gusev, Aleksander I.; Kozyrev, Nikolay A.; Osetkovskiy, Ivan V.; Kryukov, Roman E.; Kozyreva, Olga A.

    2017-10-01

    Studied the effect of the introduction of vanadium and cobalt into the charge powder fused wire system Fe-C-Si-Mn-Cr-Ni-Mo-V, used in cladding assemblies and equipment parts and mechanisms operating under abrasive and abrasive shock loads. the cored wires samples were manufactured in the laboratory conditions and using appropriate powder materials and as a carbonfluoride contained material were used the dust from gas purification of aluminum production, with the following components composition, %: Al2O3 = 21-46.23; F = 18-27; Na2O = 8-15; K2O = 0.4-6; CaO = 0.7-2.3; Si2O = 0.5-2.48; Fe2O3 = 2.1-3.27; C = 12.5-30.2; MnO = 0.07-0.9; MgO = 0.06-0.9; S = 0.09-0.19; P = 0.1-0.18. Surfacing was produced on the St3 metal plates in 6 layers under the AN-26C flux by welding truck ASAW-1250. Cutting and preparation of samples for research had been implemented. The chemical composition and the hydrogen content of the weld metal were determined by modern methods. The hardness and abrasion rate of weld metal had been measured. Conducted metallographic studies of weld metal: estimated microstructure, grain size, contamination of oxide non-metallic inclusions. Metallographic studies showed that the microstructure of the surfaced layer by cored wire system Fe-C-Si-Mn-Cr-Mo-Ni-V-Co is uniform, thin dendrite branches are observed. The microstructure consists of martensite, which is formed inside the borders of the former austenite grain retained austenite present in small amounts in the form of separate islands, and thin layers of δ-ferrite, which is located on the borders of the former austenite grains. Carried out an assessment the effect of the chemical composition of the deposited metal on the hardness and wear and hydrogen content. In consequence of multivariate correlation analysis, it was determined dependence to the hardness of the deposited layer and the wear resistance of the mass fraction of the elements included in the flux-cored wires of the system Fe-C-Si-Mn-Cr-Mo-Ni

  2. High temperature strength and aging behavior of 12%Cr-15%Mn austenitic steels

    International Nuclear Information System (INIS)

    Miyahara, Kazuya; Bae, Dong-Su; Sakai, Hidenori; Hosoi, Yuzo

    1993-01-01

    High Mn-Cr austenitic steels are still considered to be an important high temperature structural material from the point of view of reduced radio-activation. The objective of the present study is to make a fundamental research of mechanical properties and microstructure of 12%Cr-15%Mn austenitic steels. Especially the effects of alloying elements of V and Ti on the mechanical properties and microstructure evolution of high Mn-Cr steels were studied. Precipitation behaviors of carbides, nitrides and σ phase are investigated and their remarkable effects on the high temperature strength are found. The addition of V was very effective for strengthening the materials with the precipitation of fine VN. Ti was also found to be beneficial for the improvement of high temperature strength properties. The results of high temperature strengths of the 12Cr-15Mn austenitic steels were compared with those of the other candidate and/or reference materials, for example, JFMS (modified 9Cr-2Mo ferritic stainless steel) and JPCAs (modified 316 austenitic stainless steels). (author)

  3. Cyclic creep, mechanical ratchetting and amplitude history dependence of modified 9Cr-1Mo steel and evaluation of unified constitutive models

    International Nuclear Information System (INIS)

    Tanaka, Eiichi; Yamada, Hiroshi

    1993-01-01

    The purpose of the present paper is to elucidate inelastic behavior of modified 9Cr-1Mo steel as a candidate material for the next-generation fast breeder reactor and to provide the information for the formulation of a unified constitutive model. For this purpose, cyclic creep, mechanical ratchetting and amplitude history dependence of cyclic hardening were first examined at 550degC. As a result, systematic cyclic creep and mechanical ratchetting behavior were observed under various loading conditions, and little amplitude history dependence was found. Then these results were simulated by three unified constitutive models, i.e. the Chaboche, Bodner-Partom and modified Chaboche models. The simulated results show that these models cannot describe the cyclic creep and mechanical ratchetting behavior with high accuracy, but succeed in describing the inelastic behavior of amplitude variation experiments. (author)

  4. Effect of Elemental Sulfur and Sulfide on the Corrosion Behavior of Cr-Mo Low Alloy Steel for Tubing and Tubular Components in Oil and Gas Industry.

    Science.gov (United States)

    Khaksar, Ladan; Shirokoff, John

    2017-04-20

    The chemical degradation of alloy components in sulfur-containing environments is a major concern in oil and gas production. This paper discusses the effect of elemental sulfur and its simplest anion, sulfide, on the corrosion of Cr-Mo alloy steel at pH 2 and 5 during 10, 20 and 30 h immersion in two different solutions. 4130 Cr-Mo alloy steel is widely used as tubing and tubular components in sour services. According to the previous research in aqueous conditions, contact of solid sulfur with alloy steel can initiate catastrophic corrosion problems. The corrosion behavior was monitored by the potentiodynamic polarization technique during the experiments. Energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) have been applied to characterize the corrosion product layers after each experiment. The results show that under the same experimental conditions, the corrosion resistance of Cr-Mo alloy in the presence of elemental sulfur is significantly lower than its resistance in the presence of sulfide ions.

  5. The influences of impurity content, tensile strength, and grain size on in-service temper embrittlement of CrMoV steels

    International Nuclear Information System (INIS)

    Cheruvu, N.S.; Seth, B.B.

    1989-01-01

    The influences of impurity levels, grain size, and tensile strength on in-service temper embrittlement of CrMoV steels have been investigated. The samples for this study were taken from steam turbine CrMoV rotors which had operated for 15 to 26 years. The effects of grain size and tensile strength on embrittlement susceptibility were separated by evaluating the embrittlement behavior of two rotor forgings made from the same ingot after an extended step-cooling treatment. Among the residual elements in the steels, only P produces a significant embrittlement. The variation of P and tensile strength has no effect on in-service temper embrittlement susceptibility, as measured by the shift in fracture appearance transition temperature (FATT). However, the prior austenite grain size plays a major role in service embrittlement. The fine grain steels with a grain size of ASTM No. 9 or higher are virtually immune to in-service embrittlement. In steels having duplex grain sizes, embrittlement susceptibility is controlled by the size of coarser grains. For a given steel chemistry, the coarse grain steel is more susceptible to in-service embrittlement, and a decrease in ASTM grain size number from 4 to 0/1 increases the shift in FATT by 61 degrees C (10/10 degrees F). It is demonstrated that long-term service embrittlement can be simulated, except in very coarse grain steels, by using the extended step-cooling treatment. The results of step-cooling studies show that the coarse grain rotor steels take longer time during service to reach a fully embrittled state than the fine grain rotor steels

  6. High-strength maraging steels

    International Nuclear Information System (INIS)

    Grachev, S.V.; Shejn, A.S.

    1989-01-01

    Analysis of data on technological and operation properties of maraging steels on Fe-Cr-Ni, Fe-Ni, Fe-Cr-Co-Mo bases is given. Their advantages and drawbacks are pointed out. The scheme of strengthening heat treatment is considered. The fields of the most effective application of maraging steels for instance, for products operating under conditions of low-cycle and shock cyclic loading are mentioned

  7. The effect of hydrostatic pressure on the creep life of a 2.25% Cr1% Mo Steel

    International Nuclear Information System (INIS)

    Lonsdale, D.; Flewitt, P.E.J.

    1979-01-01

    The effect of superimposed hydrostatic pressures on the creep life of a 2.25% Cr 1% Mo steel, with a bainitic microstructure, is examined. Creep tests have been carried out at 923K with uniaxial stresses in the range 55 to 80 MPa and superimposed hydrostatic pressures up to 35 MPa. Optical and scanning electron microscopy have been used to evaluate the contribution of the hydrostatic stress to grain boundary cavitation. Increasing the hydrostatic pressure for a given uniaxial stress suppresses cavitation, but little changes the secondary creep rate, thereby excending the creep life. Furthermore, the time to failure depends on both the applied uniaxial stress and the hydrostatic pressure and not simply the principal stress. (orig.) [de

  8. Effects of HFIR irradiation at 550C on the microstructure and toughness of HT-9 and 9Cr-1Mo

    International Nuclear Information System (INIS)

    Gelles, D.S.; Hu, W.L.; Huang, F.H.; Johnson, G.D.

    1984-01-01

    Results are reported for base metal and weld metal specimens of HT-9 and Modified 9Cr-1Mo following irradiation in HFIR at 55 0 C to 5 dpa. The DBTT shifts in irradiated base metal specimens were 30 0 C for HT-9 and 90 0 C for 9Cr-1Mo with further shifts of 20 0 C for weld metal. Concurrently, strength as measured by hardness increased 15 percent for HT-9 and 25 percent for 9Cr-1Mo. The hardness increases can be attributed in part to defect clusters 1.5 to 3.0 nm in diameter at densities approaching 10 17 cm -3 and also to lower rates of cavity nucleation ahead of the propagating crack

  9. The Synergy Effect of Ni-M (M = Mo, Fe, Co, Mn or Cr Bicomponent Catalysts on Partial Methanation Coupling with Water Gas Shift under Low H2/CO Conditions

    Directory of Open Access Journals (Sweden)

    Xinxin Dong

    2017-02-01

    Full Text Available Ni-M (M = Mo, Fe, Co, Mn or Cr bicomponent catalysts were prepared through the co-impregnation method for upgrading low H2/CO ratio biomass gas into urban gas through partial methanation coupling with water gas shift (WGS. The catalysts were characterized by N2 isothermal adsorption, X-ray diffraction (XRD, H2 temperature programmed reduction (H2-TPR, H2 temperature programmed desorption (H2-TPD, scanning electron microscopy (SEM and thermogravimetry (TG. The catalytic performances demonstrated that Mn and Cr were superior to the other three elements due to the increased fraction of reducible NiO particles, promoted dispersion of Ni nanoparticles and enhanced H2 chemisorption ability. The comparative study on Mn and Cr showed that Mn was more suitable due to its smaller carbon deposition rate and wider adaptability to various H2/CO and H2O/CO conditions, indicating its better synergy effect with Ni. A nearly 100 h, the lifetime test and start/stop cycle test further implied that 15Ni-3Mn was stable for industrial application.

  10. Changes in mechanical properties and structure of electrolytic plasma treated X 12 CrNi 18 10 Ti stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kurbanbekov, Sherzod; Baklanov, Viktor; Karakozov, Batyrzhan [Republican State Enterprise National Nuclear Center of Kazakhstan, Kurchatov (Kazakhstan). Inst. of Atomic Energy Branch; Skakov, Mazhyn [Republican State Enterprise National Nuclear Center of Kazakhstan, Kurchatov (Kazakhstan)

    2017-05-01

    The paper addresses findings regarding the influence of electrolytic plasma treatment on the mechanical properties as well as structural and phase states of X 12 CrNi 18 10 Ti steel. Electrolytic plasma treatment is based on carburizing of stainless steel heated in electrolytes. Treatment of steel samples has been performed as follows: the samples were heated up to a temperature between 850 and 950 C and then they were cured for 7 minutes in an electrolyte of an aqueous solution containing 10 % glycerol (C{sub 3}H{sub 8}O{sub 3}) and 15 % sodium carbonate (Na{sub 2}CO{sub 3}). It is found that, after plasma electrolytic treatment, the surface of X 12 CrNi 18 10 Ti steel had a modified structure and high hardness. Increasing wear resistance of X 12 CrNi 18 10 Ti steel has been observed after carburizing and the coefficient of friction has been reduced. X-ray analysis showed that retained austenite γ-Fe is a main phase, and there are some diffraction lines of orthorhombic Fe{sub 3}C phase as well as Fe{sub 3}O{sub 4} cubic phase. It has been determined, that, after plasma electrolytic treatment, a carbide phase in the modified surface layer, irrespective of the location in the steel structure has the chemical composition Fe{sub 3}C. High concentration of carbon atoms in a solid solution based on γ- and α-iron, a large dislocation density, presence of particles of carbide phase and retained austenite layers have been found.

  11. Microstructure and Wear Behavior of FeCoCrNiMo0.2 High Entropy Coatings Prepared by Air Plasma Spray and the High Velocity Oxy-Fuel Spray Processes

    Directory of Open Access Journals (Sweden)

    Tianchen Li

    2017-09-01

    Full Text Available In the present research, the spherical FeCoCrNiMo0.2 high entropy alloy (HEA powders with a single FCC solid solution structure were prepared by gas atomization. Subsequently, the FeCoCrNiMo0.2 coatings with a different content of oxide inclusions were prepared by air plasma spraying (APS and high-velocity oxy-fuel spraying (HVOF, respectively. The microstructure, phase composition, mechanical properties, and tribological behaviors of these HEA coatings were investigated. The results showed that both HEA coatings showed a typical lamellar structure with low porosity. Besides the primary FCC phase, a mixture of Fe2O3, Fe3O4, and AB2O4 (A = Fe, Co, Ni, and B = Fe, Cr was identified as the oxide inclusions. The oxide content of the APS coating and HVOF coating was calculated to be 47.0% and 12.7%, respectively. The wear resistance of the APS coating was approximately one order of magnitude higher than that of the HVOF coating. It was mainly attributed to the self-lubricated effect caused by the oxide films. The mass loss of the APS coating was mainly ascribed to the breakaway of the oxide film, while the main wear mechanism of the HVOF coating was the abrasive wear.

  12. Effect of Mo and nano-Nd{sub 2}O{sub 3} on the microstructure and wear resistance of laser cladding Ni-based alloy coatings

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Lin; Hu, Shengsun; Shen, Junqi [Tianjin University, Tianjin Key Laboratory of Advanced Joining Technology, School of Materials Science and Engineering, Tianjin (China); Quan, Xiumin [Lu' an Vocation Technology College, School of Automobile and Mechanical and Electrical Engineering, Lu' an (China)

    2016-04-15

    Three kinds of coatings were successfully prepared on Q235 steel by laser cladding technique through adulterating with Mo and nano-Nd{sub 2}O{sub 3} into Ni-based alloys. The effect of Mo and nano-Nd{sub 2}O{sub 3} on the microstructure and properties of Ni-based coatings was investigated systematically by means of optical microscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and microhardness testing and wear testing. The results indicated a certain amount of fine grains and polygonal equiaxed grains synthesized after adding Mo and nano-Nd{sub 2}O{sub 3}. Both the microhardness and wear resistance of Ni-based coatings improved greatly with a moderate additional amount of Mo and nano-Nd{sub 2}O{sub 3}. The largest improvement in microhardness was 31.9 and 14.7 %, and the largest reduction in loss was 45.0 and 30.7 %, respectively, for 5.0 wt% Mo powders and 1.0 wt% nano-Nd{sub 2}O{sub 3}. The effect of Mo on microhardness and wear resistance of laser cladding Ni-based alloy coatings is greater than the effect of nano-Nd{sub 2}O{sub 3}. (orig.)

  13. Effects of Cr2N Precipitation on the Antibacterial Properties of AISI 430 Stainless Steel

    OpenAIRE

    Je-Kang Du; Chih-Yeh Chao; Yu-Ting Jhong; Chung-Hao Wu; Ju-Hui Wu

    2016-01-01

    Based on their mechanical properties and good corrosion resistance, some commercial Ni-Cr stainless steels have been widely applied as biomaterials, including the austenitic 304 stainless steel, the austenitic 316 stainless steel, the duplex 2205 stainless steel, and the ferritic 430 stainless steel. In order to reduce the occurrence of infections resulting from biomaterial implants, instruments, and medical devices, Cu2+ and Ag2+ ions have been added onto biomaterials for increasing the anti...

  14. The creep-fatigue crack growth behaviour of a 1CrMoV rotor steel

    International Nuclear Information System (INIS)

    Priest, R.H.; Miller, D.A.; Gladwin, D.N.; Maguire, J.

    1989-01-01

    Crack growth rates under simultaneous creep-fatigue conditions have been quantified for a 1CrMoV rotor steel. Measured growth rates were partitioned into cyclic and hold period contributions and these characterized by the relevant fracture mechanics parameters K and C. Cyclic growth rates measured in the creep-fatigue tests were enhanced compared with pure fatigue rates. This observation is compared with the behaviour of other steels and explained by quantitative metallography. The resulting crack growth equation can be used during integrity assessments for plant components containing cracks which are subject to thermal fatigue

  15. Properties of Ni-Mo steel prepared from premixed and prealloyed powder in sintered, forged and annealed state

    International Nuclear Information System (INIS)

    Salak, A.; Hrubjak, M.

    Investigated were 2Ni-0.5Mo steel specimens made of premixed powder on the base of Hametag iron and of ATST-A prealloyed powder with graphite additives of 0.3% and 0.8%. In the sintered and forged state, specimens prepared from premixed powder exhibit better strength properties compared with those made of prealloyed ATST-A powder. After annealing, the carbon content has a different bearing on both systems. With premixed powder steel of 0.6% carbon content the tensile strength amounts to 1,800 MPa whilst that of prealloyed steel specimens with 0.2% carbon content is about 1,240 MPa. (author)

  16. Microstructure evolution and mechanical properties of X12CrMoWVNbN10-1-1 steel during quenching and tempering process

    Directory of Open Access Journals (Sweden)

    Xingang Tao

    2016-01-01

    Full Text Available The effect of heat treatments was investigated on the microstructure evolution and mechanical properties of X12CrMoWVNbN10-1-1 steel. The as-received steel was austenitized at 1080 °C for 16 h and cooled in furnace, following tempered in two steps, i.e. at 570 °C for 18 h and then at 690 °C for 24 h. The austenitized sample had a typical lath martensite structure with some retained austenite and no delta ferrite was observed after austenitization. After the first tempering at 570 °C, there was no retained austenite remained but it resulted in the forming of precipitates, such as Cr-rich M7C3, Cr-rich M23C6, Cr-rich M2N, Nb-rich MN, and the subgrain, as well as the reduction in dislocation density. However, microstructure observation after secondary tempering proved the further arrangement of dislocation, subgrain growth and the coarsening of precipitates. Hardness and impact tests were carried out for establishing a correlation between microstructure and mechanical properties. Finally, a careful fractographic analysis of impact samples had been done using SEM and EDS.

  17. Fabrication and characterization of reference 9Cr and 12Cr-ODS low activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Muroga, T., E-mail: muroga@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Nagasaka, T. [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Li, Y.; Abe, H. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Ukai, S. [Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo 060-8628 (Japan); Kimura, A. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Okuda, T. [Kobelco Research Institute, 1-5-5 Takatsukadai, Nishi-ku, Kobe, Hyogo 651-2271 (Japan)

    2014-10-15

    For the purpose of arranging reference alloys available for various characterization efforts by Japanese fusion research groups, fabrication of reference 9Cr and 12Cr-ODS steels have been carried out with similar manufacturing processes followed by various characterizations. The fabrication proceeded with powder mixing, MA, encapsulation into mild steel cases, hot extrusion and hot forging, followed by final heat treatments. Each alloy was extruded into three bars. The characterization included chemical composition analysis, SEM and TEM microstructural observations, hardness tests, tensile tests at RT and 973 K, and relatively short-term thermal creep tests at 973 K. Room temperature hardness for 9Cr-ODS was larger than 12Cr-ODS, the former showing large increase when annealing temperature exceeded 1200 K and the latter showing no significant change with annealing temperature. Tensile strength of 9Cr-ODS was significantly larger than that of 12Cr-ODS at RT but comparable at 973 K. 9Cr-ODS showed longer and shorter creep rupture time than 12Cr-ODS at high and low stress levels, respectively. The mechanism of the difference in creep properties of the two alloys was discussed.

  18. Creep-fatigue behavior of 2 1/4Cr-1Mo steel at 5500C in air and vacuum

    International Nuclear Information System (INIS)

    Asayama, T.; Cheng, S.Z.; Asada, Y.; Mitsuhashi, S.; Tachibana, Y.

    1987-01-01

    Creep-fatigue tests were conducted with 2 1/4Cr-1Mo steel at 550 0 C under various strain wave forms in air and vacuum of 100 and 0.1 μPa. No indication of environmental effect of air was observed in 0.1 μPa vacuum in which a strain rate effect diminished. However, there observed still a time/rate dependent life reduction in a case of wave forms with a longer tension going time than compression. In addition, there observed an effect of mean stress with this steel. An analysis of stress-strain response showed the response is not affected by the test environment. Internal stresses of back and drag stress were obtained with this steel and an overstress was predicted based on phenomenology. A pure creep-fatigue life reduction was predicted based on a damage model composed of the overstress. The prediction showed a scatter of a factor of two. An effect of air environment was evaluated based on the prediction procedure. The method should be improved to include the effect of mean stress on creep-fatigue behavior of this steel

  19. Evaluation of mechanical properties and nano-meso structures of 9–11%Cr ODS steels

    Energy Technology Data Exchange (ETDEWEB)

    Tanno, Takashi, E-mail: tanno.takashi@jaea.go.jp [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan); Ohtsuka, Satoshi; Yano, Yasuhide; Kaito, Takeji [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan); Oba, Yojiro; Ohnuma, Masato [National Institute for Materials Science, Tsukuba 305-1195 (Japan); Koyama, Shinichi; Tanaka, Kenya [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan)

    2013-09-15

    Highlights: • We successfully manufactured 11Cr-ODS steels with residual α-ferrite controlled. • Dispersion conditions of nano oxide particles were quantitatively characterized. • Tungsten solid solution could improve only tensile strength of ODS steels at 973 K. • Oxide dispersion strengthening was dominant in creep strength of ODS steels at 973 K. -- Abstract: This study carried out mechanical tests and microstructural characterizations of several 9Cr and 11Cr-ODS tempered martensitic steels. From those results, the appropriate chemical composition range of 11Cr-ODS tempered martensitic steel was discussed from the viewpoint of high temperature strength improvement. It was shown that the residual α-ferrite fraction in 11Cr-ODS steel was successfully controlled to the same level as the 9Cr