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Sample records for alloy-based ferritic steels

  1. Fe-Cr-V ternary alloy-based ferritic steels for high- and low-temperature applications

    International Nuclear Information System (INIS)

    The phase stability of alloys and steels developed for application in nuclear fission and fusion technology is one of the decisive factors determining the potential range of operating temperatures and radiation conditions that the core elements of a power plant can tolerate. In the case of ferritic and ferritic-martensitic steels, the choice of the chemical composition is dictated by the phase diagram for binary FeCr alloys where in the 0-9% range of Cr composition the alloy remains in the solid solution phase at and below the room temperature. For Cr concentrations exceeding 9% the steels operating at relatively low temperatures are therefore expected to exhibit the formation of α' Cr-rich precipitates. These precipitates form obstacles for the propagation of dislocations, impeding plastic deformation and embrittling the material. This sets the low temperature limit for the use of of high (14% to 20%) Cr steels, which for the 20% Cr steels is at approximately 600 deg. C. On the other hand, steels containing 12% or less Cr cannot be used at temperatures exceeding ∼600 deg. C due to the occurrence of the α-γ transition (912 deg. C in pure iron and 830 deg. C in 7% Cr alloy), which weakens the steel in the high temperature limit. In this study, we investigate the physical properties of a concentrated ternary alloy system that attracted relatively little attention so far. The phase diagram of ternary Fe-Cr-V alloy shows no phase boundaries within a certain broad range of Cr and V concentrations. This makes the alloy sufficiently resistant to corrosion and suggests that steels and dispersion strengthened materials based on this alloy composition may have better strength and stability at high temperatures. Experimental heats were produced on a laboratory scale by arc melting the material components to pellets, then by melting the pellets in an induction furnace and casting the melt into copper moulds. The compositions in weight percent (iron base) are 10Cr5V, 10Cr

  2. Articles comprising ferritic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Rakowski, James M.

    2016-06-28

    An article of manufacture comprises a ferritic stainless steel that includes a near-surface region depleted of silicon relative to a remainder of the ferritic stainless steel. The article has a reduced tendency to form an electrically resistive silica layer including silicon derived from the steel when the article is subjected to high temperature oxidizing conditions. The ferritic stainless steel is selected from the group comprising AISI Type 430 stainless steel, AISI Type 439 stainless steel, AISI Type 441 stainless steel, AISI Type 444 stainless steel, and E-BRITE.RTM. alloy, also known as UNS 44627 stainless steel. In certain embodiments, the article of manufacture is a fuel cell interconnect for a solid oxide fuel cell.

  3. Rapid solidification of candidate ferritic steels

    International Nuclear Information System (INIS)

    HT-9 and 9Cr-1Mo steels were rapidly solidified by the liquid dynamic compaction process and 2-1/4Cr-1Mo steel was prepared by the ultrasonic gas atomization process. The consolidation was performed in the ferritic temperature range in order to minimize segregation. These alloys will be tested at ORNL using 1/3 CVN test specimens and the results will be compared with those for conventially processed alloys

  4. Plasma spot welding of ferritic stainless steels

    International Nuclear Information System (INIS)

    Plasma spot wedding of ferritic stainless steels studied. The study was focused on welding parameters, plasma and shieldings and the optimum welding equipment. Plasma-spot welded overlap joints on a 0.8 mm thick ferritic stainless steel sheet were subjected to a visual examination and mechanical testing in terms of tension-shear strength. Several macro specimens were prepared Plasma spot welding is suitable to use the same gas as shielding gas and as plasma gas , i. e. a 98% Ar/2% H2 gas mixture. Tension-shear strength of plasma-spot welded joint was compared to that of resistance sport welded joints. It was found that the resistance welded joints withstand a somewhat stronger load than the plasma welded joints due to a large weld sport diameter of the former. Strength of both types of welded joints is approximately the same. (Author) 32 refs

  5. Modelling fracture in ferritic steel

    CERN Document Server

    Smith, G

    2002-01-01

    Results from mathematical models and computer simulations of fracture in polycrystalline steels are presented for a range of temperatures. The proportions of intergranular and intragranular failure predicted are compared with experimental results for brittle fracture, ductile fracture and in the transition region. Interactive software to create two-dimensional polycrystalline models, which allow a range of physical to be varied independently, is described. The results include those for model materials chosen to match steels used by the power generation industry. The models simulate segregation and cavitation effects in steel and fracture of weldments and their associated heat-affected zones.

  6. Buckling response of ferritic stainless steel columns at elevated temperatures

    OpenAIRE

    Afshan, S; Gardner, L; Baddoo, NR

    2013-01-01

    This paper presents a numerical study on the buckling behaviour of ferritic stainless steel columns in fire. Finite element models were developed and validated against existing test results to predict the elevated temperature non-linear response of ferritic stainless steel columns. A total of nine austenitic and three ferritic stainless steel column tests were replicated using the finite element analysis package ABAQUS. Parametric studies were performed to investigate the effects of variation...

  7. New ferritic steels for advanced steam plants

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, K.H; Koenig, H. [GEC ALSTHOM Energie GmbH, Nuremberg (Germany)

    1998-12-31

    During the last 15-20 years ferritic-martensitic 9-12 % chromium steels have been developed under international research programmes which permit inlet steam temperatures up to approx. 625 deg C and pressures up to about 300 bars, thus leading to improvements in thermal efficiency of around 8 % and a CO{sub 2} reduction of about 20 % versus conventional steam parameters. These new steels are already being applied in 13 European and 34 Japanese power stations with inlet steam temperature up to 610 deg C. This presentation will give an account of the content, scope and results of the research programmes and of the experience gained during the production of components which have been manufactured from the new steels. (orig.) 13 refs.

  8. Annealing-induced Grain Refinement in a Nanostructured Ferritic Steel

    Institute of Scientific and Technical Information of China (English)

    Limin Wang; Zhenbo Wangt; Sheng Guo; Ke Lu

    2012-01-01

    A nanostructured surface layer with a mean ferrite grain size of -8 nm was produced on a Fe-gCr steel by means of surface mechanical attrition treatment. Upon annealing, ferrite grains coarsen with increasing temperature and their sizes increase to -40 nm at 973 K. Further increasing annealing temperature leads to an obvious reduction of ferrite grain sizes, to -14 nm at 1173 K. The annealing-induced grain refinement is analyzed in terms of phase transformations in the nanostructured steel.

  9. Delta ferrite in the weld metal of reduced activation ferritic martensitic steel

    International Nuclear Information System (INIS)

    Formation of delta(δ)-ferrite in the weld metal, during autogenous bead-on-plate welding of Reduced Activation Ferritic Martensitic (RAFM) steel using Gas Tungsten Arc Welding (GTAW) process, has been studied. Composition of the alloy is such that delta-ferrite is not expected in the alloy; but examination of the weld metal revealed presence of delta-ferrite in the weld metal. Volume fraction of delta-ferrite is found to be higher in the weld interface than in the rest of the fusion zone. Decrease in the volume fraction of delta-ferrite, with an increase in preheat temperature or with an increase in heat input, is observed. Results indicate that the cooling rate experienced during welding affects the volume fraction of delta-ferrite retained in the weld metal and variation in the delta-ferrite content with cooling rate is explained with variation in the time that the weld metal spends in various temperature regimes in which delta-ferrite is stable for the alloy during its cooling from the liquid metal to the ambient temperature. This manuscript will discuss the effect of welding parameters on formation of delta-ferrite and its retention in the weld metal of RAFM steel

  10. Delta ferrite in the weld metal of reduced activation ferritic martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Sam, Shiju, E-mail: shiju@ipr.res.in [Institute for Plasma Research, Gandhinagar, Gujarat 382 428 (India); Das, C.R.; Ramasubbu, V.; Albert, S.K.; Bhaduri, A.K.; Jayakumar, T. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Rajendra Kumar, E. [Institute for Plasma Research, Gandhinagar, Gujarat 382 428 (India)

    2014-12-15

    Formation of delta(δ)-ferrite in the weld metal, during autogenous bead-on-plate welding of Reduced Activation Ferritic Martensitic (RAFM) steel using Gas Tungsten Arc Welding (GTAW) process, has been studied. Composition of the alloy is such that delta-ferrite is not expected in the alloy; but examination of the weld metal revealed presence of delta-ferrite in the weld metal. Volume fraction of delta-ferrite is found to be higher in the weld interface than in the rest of the fusion zone. Decrease in the volume fraction of delta-ferrite, with an increase in preheat temperature or with an increase in heat input, is observed. Results indicate that the cooling rate experienced during welding affects the volume fraction of delta-ferrite retained in the weld metal and variation in the delta-ferrite content with cooling rate is explained with variation in the time that the weld metal spends in various temperature regimes in which delta-ferrite is stable for the alloy during its cooling from the liquid metal to the ambient temperature. This manuscript will discuss the effect of welding parameters on formation of delta-ferrite and its retention in the weld metal of RAFM steel.

  11. The behaviour of ferritic steels under fast neutron irradiation

    International Nuclear Information System (INIS)

    Ferritic steels have been irradiated in Rapsodie and Phenix to doses up to 150 dpa F. The swelling and irradiation creep characteristics and the mechanical properties of these materials are reported. (author)

  12. Radiation resistance and thermal creep of ODS ferritic steels

    International Nuclear Information System (INIS)

    Oxide dispersion strengthened (ODS) ferritic steels containing 0.38-0.39 wt% Y2O3 have been produced by mechanical alloying. After thermo-mechanical treatment, the structure of ODS steels includes polygonized extended grains and a great number (to ∼1016-1017 cm-3) of ultrafine complex yttrium oxides ∼2-3 nm in diameter. Irradiation by fast neutrons to 4.5x1026 n/m2 (340 K) and 1.5x1022 n/m2 (77 K) leads to strengthening and plasticity decreasing in ODS alloys. The advantages of ODS ferritic steels in creep resistance and strength against ferritic-martensitic steel 12Cr-2Mo-Nb-B-V and austenitic steel 16Cr-15Ni-3Mo-Ti-V display obviously when creep rate is approximately 10-2 h-1 and fracture time is longer than 1000 h

  13. Plasma spot welding of ferritic stainless steels

    Directory of Open Access Journals (Sweden)

    Lešnjak, A.

    2002-06-01

    Full Text Available Plasma spot welding of ferritic stainless steels is studied. The study was focused on welding parameters, plasma and shielding gases and the optimum welding equipment. Plasma-spot welded overlap joints on a 0.8 mm thick ferritic stainless steel sheet were subjected to a visual examination and mechanical testing in terms of tension-shear strength. Several macro specimens were prepared. Plasma spot welding is suitable to use the same gas as shielding gas and as plasma gas, i.e., a 98 % Ar/2 % H 2 gas mixture. Tension-shear strength of plasma-spot welded joints was compared to that of resistance-spot welded joints. It was found that the resistance welded joints withstand a somewhat stronger load than the plasma welded joints due to a larger weld spot diameter of the former. Strength of both types of welded joints is approximately the same.

    El artículo describe el proceso de soldeo de aceros inoxidables ferríticos por puntos con plasma. La investigación se centró en el establecimiento de los parámetros óptimos de la soldadura, la definición del gas de plasma y de protección más adecuado, así como del equipo óptimo para la realización de la soldadura. Las uniones de láminas de aceros inoxidables ferríticos de 0,8 mm de espesor, soldadas a solape por puntos con plasma, se inspeccionaron visualmente y se ensayaron mecánicamente mediante el ensayo de cizalladura por tracción. Se realizaron macro pulidos. Los resultados de la investigación demostraron que la solución más adecuada para el soldeo por puntos con plasma es elegir el mismo gas de plasma que de protección. Es decir, una mezcla de 98 % de argón y 2 % de hidrógeno. La resistencia a la cizalladura por tracción de las uniones soldadas por puntos con plasma fue comparada con la resistencia de las uniones soldadas por resistencia por puntos. Se llegó a la conclusión de que las uniones soldadas por resistencia soportan una carga algo mayor que la uniones

  14. Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

    OpenAIRE

    Mehanna, Maha; Basséguy, Régine; Délia, Marie-Line; Bergel, Alain

    2009-01-01

    The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (Eoc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of Eoc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended ess...

  15. Breakdown of protective oxide films on ferritic and austenitic steels

    International Nuclear Information System (INIS)

    The kinetics and morphology of scale formation on a 9% Cr ferritic and an 18% Cr austenitic steel in high pressure CO2 are discussed. For the ferritic steel, the normal protective oxidation mode is growth of a duplex scale with an Fe3O4 outer layer and an (Fe, Cr) spinel inner layer. After long times at elevated temperatures, the protective scale may break down. The more rapid attack that follows requires conjoint oxidation and carbon deposition. The austenitic steel is not susceptible to this kind of breakaway attack, but a 'breakaway' transition from M2O3 to duplex spinel growth can be induced by temperature cycling. (author)

  16. Ferritic/martensitic steels - overview of recent results

    Science.gov (United States)

    Klueh, R. L.; Gelles, D. S.; Jitsukawa, S.; Kimura, A.; Odette, G. R.; van der Schaaf, B.; Victoria, M.

    2002-12-01

    Considerable research work has been conducted on the ferritic/martensitic steels since the last International Conference on Fusion Reactor Materials in 1999. Since only a limited amount of that work can be reviewed in this paper, four areas will be emphasized: (1) the international collaboration under the auspices of the International Energy Agency (IEA) to address potential problems with ferritic/martensitic steels and to prove their feasibility for fusion, (2) the major uncertainty that remains concerning the effect of transmutation helium on mechanical properties of the steels when irradiated in a fusion neutron environment, (3) development of new reduced-activation steels beyond the F82H and JLF-1 steels studied in the IEA collaboration, and (4) work directed at developing oxide dispersion-strengthened steels for operation above 650 °C.

  17. Simulation of Ferrite Formation in Fe-C Alloys Based on a Three-Dimensional Mixed-Mode Transformation Model

    Science.gov (United States)

    van Bohemen, S. M. C.; Bos, C.; Sietsma, J.

    2011-09-01

    A three-dimensional mixed-mode (MM) transformation model accounting for both soft impingement and hard impingement was developed that calculates the growth kinetics of ferrite grains in an austenite matrix. The simulations are compared to the kinetics of ferrite formation in high-purity Fe-C alloys for which phase-transformation kinetics were measured isothermally by dilatometry at several temperatures in the range of 973 K to 1043 K (700 °C to 770 °C). The interface mobility is obtained from the best fit of the data at 1023 K (750 °C) for which the nucleus density N is estimated from the final microstructure. Subsequently, the experimental ferrite kinetics in Fe-0.36C at the other temperatures are simulated. The values of N extracted from the fits can be described with a nucleation model. The significance of the MM calculations is rationalized by comparing the results for Fe-0.17C with simulations assuming purely diffusion-controlled (DC) and purely interface-controlled (IC) growth. Comparison of simulated fraction curves for Fe-0.57C with the three models demonstrates that the transformation in high-carbon steels is essentially DC.

  18. Sintering and characterization of YAG dispersed ferritic stainless steels

    International Nuclear Information System (INIS)

    The present study investigates the effect of yttrium aluminium garnet (YAG) addition on the densification, mechanical, tribological and corrosion behaviour of ferritic (434L) stainless steels. The composites were sintered at both solid-state (1200 deg. C) and supersolidus (1400 deg. C) sintering conditions. Supersolidus sintering results in superior densification, hardness and corrosion resistance of both straight 434L stainless steel as well as YAG reinforced 434L stainless steels. The addition of YAG to 434L stainless steels at supersolidus sintered conditions improves the strength and wear resistance of 434L stainless steels without significantly degrading the corrosion performance

  19. 77 FR 60478 - Control of Ferrite Content in Stainless Steel Weld Metal

    Science.gov (United States)

    2012-10-03

    ... COMMISSION Control of Ferrite Content in Stainless Steel Weld Metal AGENCY: Nuclear Regulatory Commission... Ferrite Content in Stainless Steel Weld Metal.'' This guide describes a method that the NRC staff considers acceptable for controlling ferrite content in stainless steel weld metal. Revision 4 updates...

  20. Intragranular ferrite in inoculated low-carbon steels

    International Nuclear Information System (INIS)

    Inoculated low-carbon plate steels have been developed which provide improved low temperature toughness compared with conventional HSLA steels, and also exhibit better weldability with high heat input welding processes. These characteristics make inoculated steels suitable for large structures in severe environments. The improved toughness and weldability are attributed to the formation of microstructures containing fine, intragranular ferrite which nucleates on inclusion dispersions, similar to acicular ferrite formation in weld metals. The development of various inoculated steels is described and the role of inclusions in intragranular ferrite formation is reviewed. The primary role of inclusions is to provide heterogeneous nucleation sites, but nucleation appears to be enhanced to a certain extent by a number of other phenomena at the inclusion surface. Various phases have been shown to enhance intragranular ferrite nucleation, and the most effective of these for inoculation of plate steels are phases rich in titanium and oxygen. Inoculated Ti-O steels have found limited commercial acceptance, but further development depends on achievement of reliable steelmaking technology to optimise microstructural control with particles

  1. Development of ferritic steels for reduced activation: the US program

    International Nuclear Information System (INIS)

    The Cr-Mo ferritic (martensitic) steels are candidates for the structural components of fusion reactors. Irradiation of such steels in a fusion environment produces long-lived radioactive isotopes, which lead to difficult radioactive waste disposal problems once the structure is removed from service. Such problems could be reduced by using steels that contain only elements that produce radioactive isotopes that decay to low levels in a reasonable time (tens of years instead of hundreds or thousands of years). The US Department of Energy has a program to develop steels to meet the criteria for shallow land burial as opposed to deep geologic storage. A review of the alloy development programs indicates that ferritic steels that meet these criteria can be developed

  2. The filler powders laser welding of ODS ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Shenyong, E-mail: s_y_liang@126.com; Lei, Yucheng; Zhu, Qiang

    2015-01-15

    Laser welding was performed on Oxide Dispersion Strengthened (ODS) ferritic steel with the self-designed filler powders. The filler powders were added to weld metal to produce nano-particles (Y–M–O and TiC), submicron particles (Y–M–O) and dislocation rings. The generated particles were evenly distributed in the weld metal and their forming mechanism and behavior were analyzed. The results of the tests showed that the nano-particles, submicron particles and dislocation rings were able to improve the micro-hardness and tensile strength of welded joint, and the filler powders laser welding was an effective welding method of ODS ferritic steel.

  3. Low-chromium reduced-activation ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Development of reduced-activation ferritic steels has concentrated on high-chromium (8-10 wt% Cr) steels. However, there are advantages for a low-chromium steel, and initial ORNL studies on reduced-activation steels were on compositions with 2.25 to 12% Cr. Those studies showed an Fe-2.25Cr-2W-0.25V-0.1C (2 1/4Cr-2WV) steel to have the highest strenglth of the steels studied. Although this steel had the best strength, Charpy impact properties were inferior to those of an Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) and an Fe-2.25Cr-2W-0.1C (2 1/4Cr-2W) steel. Therefore, further development of the low-chromium Cr-W steels was required. These results indicate that it is possible to develop low-chromium reduced-activation ferritic steels that have tensile and impact properties as good or better than those of high-chromium (7-9% Cr) steels. Further improvement of properties should be possible by optimizing the composition.

  4. Deuterium Retention and Physical Sputtering of Low Activation Ferritic Steel

    Institute of Scientific and Technical Information of China (English)

    T. Hino; K. Yamaguchi; Y. Yamauchi; Y. Hirohata; K. Tsuzuki; Y.Kusama

    2005-01-01

    Low activation materials have to be developed toward fusion demonstration reactors. Ferritic steel, vanadium alloy and SiC/SiC composite are candidate materials of the first wall,vacuum vessel and blanket components, respectively. Although changes of mechanical-thermal properties owing to neutron irradiation have been investigated so far, there is little data for the plasma material interactions, such as fuel hydrogen retention and erosion. In the present study,deuterium retention and physical sputtering of low activation ferritic steel, F82H, were investigated by using deuterium ion irradiation apparatus.After a ferritic steel sample was irradiated by 1.7 kev D+ ions, the weight loss was measured to obtain the physical sputtering yield. The sputtering yield was 0.04, comparable to that of stainless steel. In order to obtain the retained amount of deuterium, technique of thermal desorption spectroscopy (TDS) was employed to the irradiated sample. The retained deuterium desorbed at temperature ranging from 450 K to 700 K, in the forms of DHO, D2, D2O and hydrocarbons. Hence, the deuterium retained can be reduced by baking with a relatively low temperature. The fluence dependence of retained amount of deuterium was measured by changing the ion fluence. In the ferritic steel without mechanical polish, the retained amount was large even when the fluence was low. In such a case, a large amount of deuterium was trapped in the surface oxide layer containing O and C. When the fluence was large, the thickness of surface oxide layer was reduced by the ion sputtering, and then the retained amount in the oxide layer decreased. In the case of a high fluence, the retained amount of deuterium became comparable to that of ferritic steel with mechanical polish or SS 316 L, and one order of magnitude smaller than that of graphite. When the ferritic steel is used, it is required to remove the surface oxide layer for reduction of fuel hydrogen retention.Ferritic steel sample was

  5. Microstructural Features During Strain Induced Ferrite Transformation in 08 and 20Mn Steels

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure evolution during strain induced ferrite transformation was followed in thermal-simulation tests of clean 08 and 20Mn steels. The influences of carbon equivalence and initial austenite grain size on ferrite grain refinement and the volume fraction of ferrite during straining were inspected. The results revealed that the accelerating effect of ferrite transformation by strain was increased as the carbon equivalence decreased. However, finer ferrite grains were obtained at higher carbon content. At strain of ~1.5 ferrite grains less than 3m and 2m can be obtained in 08 and 20Mn steels respectively. Whereas the ferrite grain refinement in 08 steel was due to both effects of strain induced transformation and ferrite dynamic recrystallization, that in 20Mn was mainly due to strain induced transformation. Heavy strain can produce fine ferrite grains in coarse austenite grained 08 steel, but it would lead to band microstructure in coarse austenite grained 20Mn.

  6. FERRITE STRUCTURE AND MECHANICAL PROPERTIES OF LOW ALLOY DUPLEX STEELS

    Energy Technology Data Exchange (ETDEWEB)

    Hoel, R.H.; Thomas, G.

    1981-04-01

    The purpose of this communication is threefold. 1) To confirm the presence of and to characterize the precipitates in the ferrite phase of the base + Nb and base + Mo steels, 2) to study any possible variation in precipitate density as the martensitic volume fraction is changed and 3) to determine the level of precipitation strengthening.

  7. Nanostructures in a ferritic and an oxide dispersion strengthened steel induced by dynamic plastic deformation

    DEFF Research Database (Denmark)

    Zhang, Zhenbo

    fission and fusion reactors. In this study, two candidate steels for nuclear reactors, namely a ferritic/martensitic steel (modified 9Cr-1Mo steel) and an oxide dispersion strengthened (ODS) ferritic steel (PM2000), were nanostructured by dynamic plastic deformation (DPD). The resulting microstructure...

  8. 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.)

  9. Chromium Enrichment on P11 Ferritic Steel by Pack Cementation

    Directory of Open Access Journals (Sweden)

    Fauzi F. A.

    2016-01-01

    Full Text Available The future thermal power plant is expected to operate at higher temperature to improve its efficiency and to reduce greenhouse gas emission. This target requires better corrosion properties of ferritic steels, which commonly used as materials for superheater and reheater of boiler tubes. In this work, chromium enrichment on the surface of ferritic steel is studied. The deposited chromium is expected to become a reservoir for the formation of chromia protective layer. Chromium was deposited on the substrate of steel by pack cementation process for two hours at the temperature of 850ºC, 950ºC and 1050ºC, respectively. XRD analysis indicated that chromium was successfully deposited at all temperatures. Somehow, SEM cross sectional image showed that continuous layer of chromium was not continuously formed at 850oC. Therefore, this research clarify that chromium enrichment by pack cementation may be conducted at the temperature above 950°C.

  10. Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Mehanna, Maha [Laboratoire de Genie Chimique, CNRS - Universite de Toulouse, 5 rue Paulin Talabot, BP1301, 31029 Toulouse (France)], E-mail: mum34@psu.edu; Basseguy, Regine; Delia, Marie-Line; Bergel, Alain [Laboratoire de Genie Chimique, CNRS - Universite de Toulouse, 5 rue Paulin Talabot, BP1301, 31029 Toulouse (France)

    2009-11-15

    The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (E{sub oc}) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of E{sub oc} ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1-10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment.

  11. Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

    International Nuclear Information System (INIS)

    The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (Eoc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of Eoc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1-10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment.

  12. Determination of delta ferrite volumetric fraction in austenitic stainless steel

    International Nuclear Information System (INIS)

    Measurements of delta ferrite volumetric fraction in AISI 304 austenitic stainless steels were done by X-ray diffraction, quantitative metallography (point count) and by means of one specific commercial apparatus whose operational principle is magnetic-inductive: The Ferrite Content Meter 1053 / Institut Dr. Foerster. The results obtained were comparated with point count, the reference method. It was also investigated in these measurements the influence of the martensite induced by mechanical deformation. Determinations by X-ray diffraction, by the ratio between integrated intensities of the ferrite (211) and austenite (311) lines, are in excelent agreement with those taken by point count. One correction curve for the lectures of the commercial equipment in focus was obtained, for the range between zero and 20% of delta ferrite in 18/8 stainless steels. It is demonstrated that, depending on the employed measurement method and surface finishing of the material to be analysed, the presence of martensite produced by mechanical deformation of the austenitic matrix is one problem to be considered. (Author)

  13. 78 FR 63517 - Control of Ferrite Content in Stainless Steel Weld Metal

    Science.gov (United States)

    2013-10-24

    ... COMMISSION Control of Ferrite Content in Stainless Steel Weld Metal AGENCY: Nuclear Regulatory Commission... revision to Regulatory Guide (RG) 1.31, ``Control of Ferrite Content in Stainless Steel Weld Metal.'' This... content in stainless steel weld metal. It updates the guide to remove references to outdated standards...

  14. Ferrite hardening response in a low alloy ferrite–martensite dual phase steel

    International Nuclear Information System (INIS)

    Highlights: • The ferrite hardening response varies with ferrite volume fraction. • A considerable variation in hardness was observed within a specific ferrite grain. • Finer ferrite grains were accompanied by more homogenized carbon content. • Coarser ferrite grains depicted a significant gradient of carbon content. • Ferrite hardness increased along the center to the peripheral regions of a grain. -- Abstract: This paper is concerned to investigate in details the variation of ferrite hardening response in conjunction with carbon partitioning developed within ferrite during austenite to ferrite phase transformation in a low alloy ferrite–martensite dual phase (DP) steel. For this purpose, a wide variety of ferrite–martensite DP microstructures consisting different volume fractions of ferrite and martensite have been prepared using step quenching heat treatment processes at isothermal temperature of 600 °C for various holding times. Nanoindentation measurements have been supplemented by energy dispersive X-ray and microprobe wavelength-dispersive spectroscopic analyses to follow the variation of ferrite hardening response and its relation to the carbon concentration of ferrite in the ferrite–martensite DP microstructures. The experimental results showed that the ferrite hardening response is quite variable depending on the progress of ferrite formation in the ferrite–martensite DP microstructures. For a specific ferrite grain in a specific ferrite martensite DP microstructure, the location nearer to the ferrite–martensite interfaces has been accompanied with a significant higher carbon concentration and simultaneously higher ferrite hardening response in comparison to that of central regions of ferrite grains. These results are rationalized with a higher concentration of carbon within ferrite developed as a consequence of higher carbon entrapment within defected ferrite area generated at early stage of austenite to ferrite phase transformation

  15. Ultra-Pure Ferritic Stainless Steels-Grade, Refining Operation, and Application

    Institute of Scientific and Technical Information of China (English)

    YOU Xiang-mi; JIANG Zhou-hua; LI Hua-bing

    2007-01-01

    The grades of ultra-pure ferritic stainless steels, especially the grades used in automobile exhaust system, were reviewed. The dependence of properties on alloying elements, the refining facilities, and the mechanism of the reactions in steel melts were described in detail. Vacuum, strong stirring, and powder injection proved to be effective technologies in the melting of ultra-pure ferritic stainless steels. The application of the ferritic grades was also briefly introduced.

  16. THE INFLUENCE OF POSTHEAT TREATMENT ON FERRITE REDISTRIBUTION IN DUPLEX STEELS ELECTRON BEAM WELDS

    OpenAIRE

    Zita Iždinská; František Kolenič

    2009-01-01

    The duplex stainless steel is two-phase steel with the structure composed of austenite and ferrite with optimum austenite/ferrite proportion 50%. At present, classical arc processes for welding duplex steels are generally regarded as acceptable. On the other hand electron and laser beam welding is up to now considered less suitable for welding duplex steels. The submitted work presents the results of testing various thermal conditions at welding duplex stainless steel with electron beam. It w...

  17. Deformation Behavior of Ultra-low Carbon Steel in Ferrite Region during Warm Processing

    Institute of Scientific and Technical Information of China (English)

    XU Guang; CHEN Zhenye; LIU Li; YU Shengfu

    2008-01-01

    The hot deformation experiments of ultra-low carbon steel in ferrite range were carried out ina hot simulator in order to research hot deformation behaviors of ultra-low carbon steel in ferrite range at low temperature.The results show that the influences of deformation parameters on flow stress are different to those in austenitic deformation.The deformation characteristic parameters were calculated for ultra-low carbon steel in ferrite region.The flow stress equation for ultra-low carbon steel in ferritic deformation at low temperature was obtained.

  18. Superplastic solid state welding steel and copper alloy based on laser quenching of steel surface

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ke-ke; HAN Cai-xia; QUAN Shu-li; CHENG Guang-hui; YANG Jie; YANG Yun-lin

    2005-01-01

    Based on the feasibility of isothermal superplastic solid state welding of steel and copper alloy, the welded surface of steel surface was ultra-fined through laser quenching, and then the welding process tests between different base metals of 40Cr and QCr0.5 were made under the condition of non vacuum and non shield gas. The experimental results show that, with the sample surface of steel after laser quenching and that of copper alloy carefully cleaned, and under the pre-pressed stress of 56.6 -84.9 MPa, at the welding temperature of 750 -800 ℃ and at initial strain rate of (2.5 - 7.5) × 10-4 s-1 , the solid state welding can be finished in 120 - 180 s so that the strength of the joint is up to that of QCr0.5 base metal and the expansion rate of the joint does not exceed 6%. The plastic deformation of the joint was further analysed. The superplastic deformation of the copper alloy occurs in welding process and the deformation of steel are little.

  19. Ferrite hardening response in a low alloy ferrite–martensite dual phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Fereiduni, E., E-mail: e.fereiduni@yahoo.com; Ghasemi Banadkouki, S.S.

    2014-03-15

    Highlights: • The ferrite hardening response varies with ferrite volume fraction. • A considerable variation in hardness was observed within a specific ferrite grain. • Finer ferrite grains were accompanied by more homogenized carbon content. • Coarser ferrite grains depicted a significant gradient of carbon content. • Ferrite hardness increased along the center to the peripheral regions of a grain. -- Abstract: This paper is concerned to investigate in details the variation of ferrite hardening response in conjunction with carbon partitioning developed within ferrite during austenite to ferrite phase transformation in a low alloy ferrite–martensite dual phase (DP) steel. For this purpose, a wide variety of ferrite–martensite DP microstructures consisting different volume fractions of ferrite and martensite have been prepared using step quenching heat treatment processes at isothermal temperature of 600 °C for various holding times. Nanoindentation measurements have been supplemented by energy dispersive X-ray and microprobe wavelength-dispersive spectroscopic analyses to follow the variation of ferrite hardening response and its relation to the carbon concentration of ferrite in the ferrite–martensite DP microstructures. The experimental results showed that the ferrite hardening response is quite variable depending on the progress of ferrite formation in the ferrite–martensite DP microstructures. For a specific ferrite grain in a specific ferrite–martensite DP microstructure, the location nearer to the ferrite–martensite interfaces has been accompanied with a significant higher carbon concentration and simultaneously higher ferrite hardening response in comparison to that of central regions of ferrite grains. These results are rationalized with a higher concentration of carbon within ferrite developed as a consequence of higher carbon entrapment within defected ferrite area generated at early stage of austenite to ferrite phase

  20. Low-chromium reduced-activation ferritic steels

    International Nuclear Information System (INIS)

    Steels are being developed for fusion-reactor applications that contain only elements that produce radioactive isotopes that decay to low levels in a reasonable time. These reduced-activation or fast induced-radioactivity decay ferritic steels are being developed to be analogous to the Cr-Mo steels presently in the fusion program, but with molybdenum replaced by tungsten. In this paper, steels with 2-1/4% Cr will be discussed. To determine the effect of tungsten and vanadium on these steels, heats were produced with 2% W, with 0.25% V, with 1% W and 0.25% V, and with 2% W and 0.25% V. Tempering and microstructural studies were made and tensile and impact tests were conducted. Preliminary results indicate that it should be possible to develop a low-chromium Cr-W steel without molybdenum or niobium. Such steels should have properties as good as or better than the three Cr-Mo steels presently being considered as candidates for fusion-reactor applications. 22 refs., 12 figs., 3 tabs

  1. Hot-rolling of reduced activation 8CrODS ferritic steel

    International Nuclear Information System (INIS)

    Highlights: •Hot-rolling can induce a coarser ferrite grain in 8CrODS ferritic steel. •HR specimen consists of martensite, residual ferrite and transformed ferrite. •The coarsening of the transformed ferrite was analyzed by EBSD. •Hot-rolling can improve the strength of 8CrODS ferritic steel at 700 °C. -- Abstract: The 8CrODS ferritic steel is based on J1-lot developed for the advanced fusion blanket material to increase the coolant outlet temperature. A hot-rolling was conducted at the temperature above Ar3 of 716 °C, and its effect on the microstructure and tensile strength in 8CrODS ferritic steel was evaluated, comparing together with normalized and tempered specimen. It was confirmed that hot-rolling leads to slightly increased fraction of the ferrite and highly improved tensile strength. This ferrite was formed by transformation from the hot-rolled austenite during cooling due to fine austenite grains induced by hot-rolling. The coarsening of the transformed ferrite in hot-rolled specimen can be attributed to the crystalline rotation and coalescence of the similar oriented grains. The improved strength of hot-rolled specimen was ascribed to the high dislocation density and replacement of easily deformed martensite with the transformed coarse ferrite

  2. Hot-rolling of reduced activation 8CrODS ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaochao, E-mail: chaoxiaowu_008@163.com [Hokkaido University, Graduate School of Engineering, Materials Science and Engineering, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Ukai, Shigeharu [Hokkaido University, Faculty of Engineering, Materials Science and Engineering, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Leng, Bin [Hokkaido University, Graduate School of Engineering, Materials Science and Engineering, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Oono, Naoko; Hayashi, Shigenari [Hokkaido University, Faculty of Engineering, Materials Science and Engineering, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Sakasegawa, Hideo; Tanigawa, Hiroyasu [Japan Atomic Energy Agency, 4002 Oarai, Ibaraki 311-1393 (Japan)

    2013-11-15

    Highlights: •Hot-rolling can induce a coarser ferrite grain in 8CrODS ferritic steel. •HR specimen consists of martensite, residual ferrite and transformed ferrite. •The coarsening of the transformed ferrite was analyzed by EBSD. •Hot-rolling can improve the strength of 8CrODS ferritic steel at 700 °C. -- Abstract: The 8CrODS ferritic steel is based on J1-lot developed for the advanced fusion blanket material to increase the coolant outlet temperature. A hot-rolling was conducted at the temperature above A{sub r3} of 716 °C, and its effect on the microstructure and tensile strength in 8CrODS ferritic steel was evaluated, comparing together with normalized and tempered specimen. It was confirmed that hot-rolling leads to slightly increased fraction of the ferrite and highly improved tensile strength. This ferrite was formed by transformation from the hot-rolled austenite during cooling due to fine austenite grains induced by hot-rolling. The coarsening of the transformed ferrite in hot-rolled specimen can be attributed to the crystalline rotation and coalescence of the similar oriented grains. The improved strength of hot-rolled specimen was ascribed to the high dislocation density and replacement of easily deformed martensite with the transformed coarse ferrite.

  3. Friction stir joining of dissimilar ferritic ODS steels

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Suk Hoon; Jang, Jin Sung; Noh, Sang Hoon; Kim, Tae Kyu [Nuclear Materials Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    Application of the latest developments in materials technology may greatly aid in the successful pursuit of next generation reactor and transmutation technologies. Oxide dispersion strengthened (ODS) ferritic steels are expected to be used as a long life cladding in the future advanced fast reactor. Comparing to the other steels, ODS steels have excellent resistance to creep and swelling as well as superior mechanical strength. Applications of ODS steels grow faster in nuclear engineering society; however, not so many studies have been made for improving weld properties. In ODS steels, it is well known that uniform nano oxide depressed act as pinning points to obstruct dislocation and grain boundary motion, however, those advantages will be disappeared while the material is subjected to the high temperature of conventional fusion welding. Rotary friction welding, also referred to as friction stir welding (FSW), has shown great promise as a method for joining traditionally difficult to join materials such as aluminum alloys. This relatively new technology, first developed in 1991, has more recently been applied to higher melting temperature alloys such as steels, nickel-based and titanium alloys. In this study, FSW is used as a substitutive welding process for ferritic ODS steels, solid state microstructure modification is performed. During the FSW, dynamic recrystallized grains are developed; the uniform oxides dispersion is preserved in the metal matrix. The microstructure and micro texture of the material near the stir zone was found to be influenced by the rotational behavior of the tool. The response of material for different process variables have been discussed in terms of plastic deformation amount and heat input.

  4. Thin slab processing of acicular ferrite steels with high toughness

    Energy Technology Data Exchange (ETDEWEB)

    Reip, Carl-Peter; Hennig, Wolfgang; Hagmann, Rolf [SMS Demag Aktiengesellschaft, Duesseldorf (Germany); Sabrudin, Bin Mohamad Suren; Susanta, Ghosh; Weng Lan Lee [Megasteel Sdn Bhd, Banting (Malaysia)

    2005-07-01

    Near-net-shape casting processes today represent an important option in steelmaking. High productivity and low production cost as well as the variety of steel grades that can be produced plus an excellent product quality are key factors for the acceptance of such processes in markets all over the world. Today's research focuses on the production of pipe steel with special requirements in terms of toughness at low temperatures. The subject article describes the production of hot strip made from acicular ferritic / bainitic steel grades using the CSP thin-slab technology. In addition, the resulting strength and toughness levels as a function of the alloying concepts are discussed. Optimal control of the CSP process allows the production of higher-strength hot-rolled steel grades with a fine-grain acicular-ferritic/bainitic microstructure. Hot strip produced in this way is characterized by a high toughness at low temperatures. In a drop weight tear test, transition temperatures of up to -50 deg C can be achieved with a shear-fracture share of 85%. (author)

  5. Corrosion of an austenite and ferrite stainless steel weld

    Directory of Open Access Journals (Sweden)

    BRANIMIR N. GRGUR

    2011-07-01

    Full Text Available Dissimilar metal connections are prone to frequent failures. These failures are attributed to the difference in the mechanical properties across the weld, the coefficients of thermal expansion of the two types of steels and the resulting creep at the interface. For the weld analyzed in this research, it was shown that corrosion measurements can be used for a proper evaluation of the quality of weld material and for the prediction of whether or not the material, after the applied welding process, can be in service without failures. It was found that the corrosion of the weld analyzed in this research resulted from the simultaneous activity of different types of corrosion. In this study, electrochemical techniques including polarization and metallographic analysis were used to analyze the corrosion of a weld material of ferrite and austenitic stainless steels. Based on surface, chemical and electrochemical analyses, it was concluded that corrosion occurrence was the result of the simultaneous activity of contact corrosion (ferrite and austenitic material conjuction, stress corrosion (originating from deformed ferrite structure and inter-granular corrosion (due to chromium carbide precipitation. The value of corrosion potential of –0.53 V shows that this weld, after the thermal treatment, is not able to repassivate a protective oxide film.

  6. INTRAGRANULAR FERRITE FORMED IN ASSOCIATION WITH INCLUSIONS IN A VANADIUM MICROALLOYED STEEL

    Institute of Scientific and Technical Information of China (English)

    K.M. Wu; M. Enomoto

    2004-01-01

    Intragranular ferrite was formed at inclusions in a vanadium microalloyed steel with excess amount of sulfur. The chemical composition of inclusions in the steel was analyzed by SEM-EDS. The inclusions were mainly composed of MnS and aluminum oxides. The precipitation of MnS at aluminum oxides might result in Mn depletion, which, in turn, promotes the formation of intragranular ferrite. Optical and SEM observations and threedimensional (3D) reconstruction demonstrated that intragranular ferrite was formed at inclusions. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite was nearly equiaxed whereas it was plate-like or lath-like at lower temperatures.

  7. Optimization and testing results of Zr-bearing ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tyburska-Puschel, Beata [Univ. of Wisconsin, Madison, WI (United States); Sridharan, K. [Univ. of Wisconsin, Madison, WI (United States)

    2014-09-01

    The mission of the Nuclear Energy Enabling Technologies (NEET) program is to develop crosscutting technologies for nuclear energy applications. Advanced structural materials with superior performance at elevated temperatures are always desired for nuclear reactors, which can improve reactor economics, safety margins, and design flexibility. They benefit not only new reactors, including advanced light water reactors (LWRs) and fast reactors such as sodium-cooled fast reactor (SFR) that is primarily designed for management of high-level wastes, but also life extension of the existing fleet when component exchange is needed. Developing and utilizing the modern materials science tools (experimental, theoretical, and computational tools) is an important path to more efficient alloy development and process optimization. Ferritic-martensitic (FM) steels are important structural materials for nuclear reactors due to their advantages over other applicable materials like austenitic stainless steels, notably their resistance to void swelling, low thermal expansion coefficients, and higher thermal conductivity. However, traditional FM steels exhibit a noticeable yield strength reduction at elevated temperatures above ~500°C, which limits their applications in advanced nuclear reactors which target operating temperatures at 650°C or higher. Although oxide-dispersion-strengthened (ODS) ferritic steels have shown excellent high-temperature performance, their extremely high cost, limited size and fabricability of products, as well as the great difficulty with welding and joining, have limited or precluded their commercial applications. Zirconium has shown many benefits to Fe-base alloys such as grain refinement, improved phase stability, and reduced radiation-induced segregation. The ultimate goal of this project is, with the aid of computational modeling tools, to accelerate the development of a new generation of Zr-bearing ferritic alloys to be fabricated using conventional

  8. Development of oxide dispersion strengthened ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, D.K. [Vista Metals, Inc., McKeesport, PA (United States); Froes, F.H. [Univ. of Idaho, ID (United States); Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    An oxide dispersion strengthened (ODS) ferritic steel with high temperature strength has been developed in line with low activation criteria for application in fusion power systems. The composition Fe-13.5Cr-2W-0.5Ti-0.25Y{sub 2}O{sup 3} was chosen to provide a minimum chromium content to insure fully delta-ferrite stability. High temperature strength has been demonstrated by measuring creep response of the ODS alloy in uniaxial tension at 650 and 900 C in an inert atmosphere chamber. Results of tests at 900 C demonstrate that this alloy has creep properties similar to other alloys of similar design and can be considered for use in high temperature fusion power system designs. The alloy selection process, materials production, microstructural evaluation and creep testing are described.

  9. Fracture toughness of steels of martensite-ferrite structure

    International Nuclear Information System (INIS)

    The effect is studied of ferrite, incorporated in a martensitic structure, upon the resistance to cracking of a low-tempered grade 40Kh steel, said resistance being in evaluated terms of the parameter Ksub(1C) and the kinetics of the fatigue crack. It has been shown that, for low values of the stress intensity factor in the mouth of a crack Δ K, the combined martensitic-ferritic structure possesses a greater resilience than the purely martensitic one. The increase in Δ K to Ksub(1C) lowers the resistance to cracking of the combined structure as compared to the purely martensitic one. Said effects are explained on the basis of electron-diffraction fractographic and microscopic observations of crack development

  10. Nucleation and three-dimensional morphology of intragranular ferrite in a vanadium microalloyed steel

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The formation of intragranular ferrite at inclusions was analyzed by SEM-EDX in a vanadium microalloyed steel with an excess amount of sulfur. The precipitation of MnS at aluminum oxides may result in Mn depletion, which, in turn, promotes the formation of intragranular ferrite. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite is nearly equiaxed whereas it is plate-like at lower temperatures.

  11. Microstructure and Mechanical Propertiesof a Nitride-Strengthened Reduced ActivationFerritic/Martensitic Steel

    OpenAIRE

    Zhou, Qiangguo; Zhang, Wenfeng; Yan, Wei; Wang, Wei; SHA, WEI; Shan, Yiyin; Yang, Ke

    2012-01-01

    Nitride-strengthened reduced activation ferritic/martensitic (RAFM) steels are developed taking advantage of the high thermal stability of nitrides. In the current study, the microstructure and mechanical properties of a nitride-strengthened RAFM steel with improved composition were investigated. Fully martensitic microstructure with fine nitrides dispersion was achieved in the steel. In all, 1.4 pct Mn is sufficient to suppress delta ferrite and assure the steel of the full martensitic micro...

  12. Nano-indentation hardness evaluation of 9Cr-ODS ferritic steel

    International Nuclear Information System (INIS)

    An oxide dispersion strengthened (ODS) ferritic steel is the most prospective candidate cladding material for the sodium-cooled fast reactor (SFR) and other Generation IV reactors. Their target average burnup is 150 GWd/t and relevant neutron dose is as high as 250 dpa. For SFR fuel elements, Japan Atomic Energy Agency has been extensively developing 9Cr-ODS ferritic steel cladding, which exhibits the distinguished creep rupture strength at 973K. In order to elucidate its strengthening mechanism, hardness measurement using 1 mN load was conducted by means of nano-indentaion technique. The 9Cr-ODS ferritic steel exhibits the unique composite structure consisting of the ferrite grains designated as residual ferrite and surrounding tempered martensite grains. The nano-scopic hardness corresponding to individual grains, i.e. residual ferritic grains and tempered martensite grains, was directly measured at the condition of the normalizing and tempering. The inherent hardness of martensite grains reduces with increasing tempering temperature, whilst residual ferrite grains maintain almost constant hardness. TEM observation of the dispersed oxide particles suggested that a dispersion strengthening is slightly higher in residual ferritic grains, but dominant strengthening mechanism could be owing to extremely high density of dislocations, and their recovery retards in residual ferritic grains. The excellent high-temperature strength of 9Cr-ODS ferritic steel is attributed to optimum balancing between hard residual ferrite and soft tempered martensite grains. (authors)

  13. Predication of Plastic Flow Characteristics in Ferrite/Pearlite Steel Using a Fern Unit Cell Method

    Institute of Scientific and Technical Information of China (English)

    Hong Li; Jingtao Han; Jing Liu; Lv Zhang

    2004-01-01

    The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.

  14. The properties and weldability of low activation ferritic steels

    International Nuclear Information System (INIS)

    A series of ferritic steels patterned on the chromium-molybdenum alloys, 2 1/4Cr--1Mo, 9Cr--1MoVNb and 12Cr--1MoVW, were tested for weldability. These steels are being developed as candidates for the first wall and blanket structures of fusion reactors. Use of these materials will minimize the long term radioactive hazards associated with disposal after service. In these low activation alloys, elements which become activated during irradiation with long half lives (Mo and Nb) are replaced. The major changes include the replacement of molybdenum with tungsten, the addition of vanadium in 2 1/4% Cr steels, and the replacement of niobium in the 9% Cr steel with tantalum. These replacement elements radically modify both the mechanical properties and weldability of the alloys. In this study, the effect of the alloy modifications on the microstructure and the mechanical properties of the welds are presented. Bainitic steels (2 1/4 Cr%) usually exhibit good weldability, while the martensitic steels (5, 9 and 12 Cr%) are suspectable to embrittlement in the heat affected zone (HAZ). The objective of this study was to characterize the welded microstructure and mechanical properties of these low activation alloys. Autogeneous bead-on-plate welds were produced using the gas tungsten arc welding (GTAW) process. Microstructure, microhardness, weld bend and tensile test results are reported for the base metal, heat affected zone and fusion zone of the weld. 46 refs., 36 figs., 14 tabs

  15. Analysis of ridging in ferritic stainless steel sheet

    Energy Technology Data Exchange (ETDEWEB)

    Wu, P.D. [Novelis Inc., Novelis Global Technology Centre, 945 Princess Street, Kingston, Ont., K7L 5L9 (Canada)]. E-mail: wupeidong@hotmail.com; Jin, H. [Novelis Inc., Novelis Global Technology Centre, 945 Princess Street, Kingston, Ont., K7L 5L9 (Canada); Shi, Y. [Novelis Inc., Novelis Global Technology Centre, 945 Princess Street, Kingston, Ont., K7L 5L9 (Canada); Lloyd, D.J. [Novelis Inc., Novelis Global Technology Centre, 945 Princess Street, Kingston, Ont., K7L 5L9 (Canada)

    2006-05-15

    The finite element method is used to numerically simulate the development of ridging/roping in ferritic stainless steel sheet under stretching. The measured electron backscattered diffraction (EBSD) data (grain orientations and their spatial distributions) are directly incorporated into the finite element model and the constitutive response at an integration point is described by the single crystal plasticity theory. The effects of spatial orientation distribution, imposed deformation path, and inhomogeneous deformation within individual grains on the roping are discussed. It is found that the initial texture and its spatial distribution are the predominant factors for the development of ridging.

  16. Foucault current testing of ferritic steel fuel cans

    International Nuclear Information System (INIS)

    The analysis of impedance involved by a Foucault current test of ferritic steel tubes, is quite different from the classical analysis which refers to non-magnetic tubes; more particularly, volume defects are considered as magnetic anomalies. Contrarily to current instructions which recommend to test the product in a satured magnetic state, it is very interesting to work with a continuous energizing field, comparatively low, corresponding to a sequenced magnetization, of which value is obtained according to the magnetic structure of the product. This analysis is useful when testing fast reactor fuel cans

  17. Microstructural change on electron irradiated oxide dispersion strengthened ferritic steels

    Science.gov (United States)

    Kinoshita, H.; Akasaka, N.; Takahashi, H.; Shibahara, I.; Onose, S.

    1992-09-01

    Oxide dispersion strengthened (ODS) ferritic steels were irradiated in a high voltage electron microscope (HVEM) to study their response to irradiation. Fe-13Cr with 0.25 wt% Y2O3 as dispersed particles and containing additions of either 0.45% Nb, 0.45% V and 0.67% Zr were irradiated at 673 and 723 K up to 15 dpa. The Y2O3 particles in all specimens were stable under these irradiation conditions. During irradiation, two types of dislocations were formed but observable voids were not formed. Furthermore, plate-like and granular-like precipitates formed in both the irradiated and nonirradiated regions.

  18. Effect of initial microstructures on the properties of Ferrite-Martensite Dual-Phase pipeline steels with Strain-Based design

    OpenAIRE

    Yueyue Hu; Xiurong Zuo; Rutao Li; Zhanzhan Zhang

    2012-01-01

    This study aims to investigate the effect of initial microstructures on the properties of ferrite-martensite dual-phase pipeline steels with strain-based design. For this purpose, the as-received acicular ferrite steels were first austenitized at 920 ºC for 15 minutes followed by air cooling and water quenching to produce ferrite-pearlite and ferrite-martensite microstructure, respectively. Subsequently, the steels with ferrite-pearlite, ferrite-martensite and as-received acicular ferrite mic...

  19. Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

    Science.gov (United States)

    Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

    2010-03-16

    An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

  20. Sticking Phenomenon Occurring during Hot Rolling of Ferritic Stainless Steels

    International Nuclear Information System (INIS)

    Sticking phenomenon occurring during hot rolling of two ferritic stainless steels, STS 430J1L and STS 436L, was investigated in this study. A hot rolling simulation test was carried out using a high-temperature wear tester capable of controlling rolling speed, load, and temperature. The simulation test results at 900 .deg. C and 1000 .deg. C revealed that the sticking process proceeded with three stages, i.e., nucleation, growth, and saturation, for the both stainless steels, and that STS 430J1L had a smaller number of sticking nucleation sites than the STS436L because of higher high-temperature hardness, thereby leading to a smaller amount of the sticking. When the test temperature was 1070 .deg. C, the sticking hardly occurred in both stainless steels as Fe-Cr oxide layers were formed on the surface of the rolled materials. These findings suggested that the improvement of high-temperature properties of stainless steels and the appropriate rolling conditions for readily forming oxide layers on the rolled material surface were required in order to prevent or minimize the sticking

  1. Sticking Phenomenon Occurring during Hot Rolling of Ferritic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Son, Chang Young; Kim, Chang Kyu; Ha, Dae Jin; Lee, Sung Hak [Pohang Univ. of Institute of Science and Technology, Pohang (Korea, Republic of); Lee, Jong Seog; Kim, Kwang Tae; Lee, Yong Deuk [POSCO Technical Research Lab., Gwangyang (Korea, Republic of)

    2007-01-15

    Sticking phenomenon occurring during hot rolling of two ferritic stainless steels, STS 430J1L and STS 436L, was investigated in this study. A hot rolling simulation test was carried out using a high-temperature wear tester capable of controlling rolling speed, load, and temperature. The simulation test results at 900 .deg. C and 1000 .deg. C revealed that the sticking process proceeded with three stages, i.e., nucleation, growth, and saturation, for the both stainless steels, and that STS 430J1L had a smaller number of sticking nucleation sites than the STS436L because of higher high-temperature hardness, thereby leading to a smaller amount of the sticking. When the test temperature was 1070 .deg. C, the sticking hardly occurred in both stainless steels as Fe-Cr oxide layers were formed on the surface of the rolled materials. These findings suggested that the improvement of high-temperature properties of stainless steels and the appropriate rolling conditions for readily forming oxide layers on the rolled material surface were required in order to prevent or minimize the sticking.

  2. Ferrite/pearlite microstructural and microchemical banding in hot rolled microalloyed steel

    International Nuclear Information System (INIS)

    Ferrite/pearlite banded structure is commonly observed in the hot rolled steels which can be described as a microstructure comprising of alternate layers of pro eutectoid ferrite and perlite in contrast to random distribution of these microstructural constituents. The occurrence of banded ferrite/pearlite structure has been well established in case plan carbon steels to segregation of Mn and consequently carbon during solidification. However this has not yet been reported for microalloyed steels. In this work the influence of microchemical and microstructural banding has been examined in microalloyed steel using optical. SEM and fine-probe EDS microanalysis. The compositional changes occurred in the ferrite/pearlite banded structure are explained by the diffusion of elements in the microalloyed steel. (author)

  3. Mechanical properties of high strength quenched steels with minute amounts of ferrite

    International Nuclear Information System (INIS)

    In this paper the effects of minute amounts of ferrite on mechanical properties in high strength quenched steels were studied by the sound emission method. The results show that, with the same macrohardness, a decrease of 75% of the resistance to minute amounts of the plastic deformation is as a result of 2.0% ferrite in steels, moreover, both the resistance to ambient temperature creep and the resistance to low cycle fatigue are reduced when minute amounts of ferrite exists in steels. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  4. Conversion of MX Nitrides to Modified Z-Phase in 9-12%Cr Ferritic Steels

    OpenAIRE

    Cipolla, Leonardo; Somers, Marcel A. J.; Hald, John

    2010-01-01

    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 oxidat...

  5. Fatigue Crack Growth Behavior of Gas Metal Arc Welded AISI 409 Grade Ferritic Stainless Steel Joints

    Science.gov (United States)

    Lakshminarayanan, A. K.; Shanmugam, K.; Balasubramanian, V.

    2009-10-01

    The effect of filler metals such as austenitic stainless steel, ferritic stainless steel, and duplex stainless steel on fatigue crack growth behavior of the gas metal arc welded ferritic stainless steel joints was investigated. Rolled plates of 4 mm thickness were used as the base material for preparing single ‘V’ butt welded joints. Center cracked tensile specimens were prepared to evaluate fatigue crack growth behavior. Servo hydraulic controlled fatigue testing machine with a capacity of 100 kN was used to evaluate the fatigue crack growth behavior of the welded joints. From this investigation, it was found that the joints fabricated by duplex stainless steel filler metal showed superior fatigue crack growth resistance compared to the joints fabricated by austenitic and ferritic stainless steel filler metals. Higher yield strength and relatively higher toughness may be the reasons for superior fatigue performance of the joints fabricated by duplex stainless steel filler metal.

  6. Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

    Energy Technology Data Exchange (ETDEWEB)

    Sarkari Khorrami, Mahmoud; Mostafaei, Mohammad Ali; Pouraliakbar, Hesam, E-mail: hpouraliakbar@alum.sharif.edu; Kokabi, Amir Hossein

    2014-07-01

    In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662 MPa to 910 MPa, 140 Hv to 385 Hv, and 53.6 J m{sup −3} to 79 J m{sup −3}, respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

  7. Activating Flux Design for Laser Welding of Ferritic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    马立; 胡绳荪; 胡宝; 申俊琦; 王勇慧

    2014-01-01

    The behaviors of YAG laser welding process of ferritic stainless steel with activating fluxes were investi-gated in this study. Some conventional oxides, halides and carbonates were applied in laser welding. The results showed that the effect of oxides on the penetration depth was more remarkable. Most activating fluxes improved the penetration more effectively at low power than that at high power. The uniform design was adopted to arrange the formula of multicomponent activating fluxes, showing that the optimal formula can make the penetration depth up to 2.23 times as large as that without flux, including 50%ZrO2, 12.09%CaCO3, 10.43%CaO and 27.48%MgO. Through the high-speed photographs of welding process, CaF2 can minimize the plasma volume but slightly improve the pene-tration capability.

  8. Evaluation of misindexing of EBSD patterns in a ferritic steel.

    Science.gov (United States)

    Karthikeyan, T; Dash, M K; Saroja, S; Vijayalakshmi, M

    2013-01-01

    The systematic misindexing caused by pseudo-symmetry Kikuchi diffraction patterns in automated Electron Backscatter Diffraction analysis has been studied in a 9Cr-1Mo ferritic steel. Grains with its [1 1 1] directed towards detector centre were found to be prone to misindexing, and the solutions exhibit a relative orientation of ±30° and 60° about the common [1 1 1] axis (as compared to the true orientation). Fictitious boundaries were detected within such grains, which satisfy the Σ3 or Σ13b type coincidence site lattice boundary criteria. Misindexing rate was reduced with more than six detected bands, but 30° rotated solution was comparatively more persistent, as the additional bands of (3 1 0)-type exhibited a nearly good pattern match. Increase in detector collection angle to 0.96 sr or number of detected bands to nine were found to be beneficial in preventing the misindexing problem.

  9. Mechanical behaviour of ferritic ODS steels - Temperature dependancy and anisotropy

    Science.gov (United States)

    Fournier, B.; Steckmeyer, A.; Rouffie, A.-L.; Malaplate, J.; Garnier, J.; Ratti, M.; Wident, P.; Ziolek, L.; Tournie, I.; Rabeau, V.; Gentzbittel, J. M.; Kruml, T.; Kubena, I.

    2012-11-01

    Ferritic 14%Cr and 18%Cr ODS steels produced at CEA in round bars or plates were tested mechanically. The present paper reports results obtained in tension, impact, fatigue, creep and toughness tests. These tests were carried out at various temperatures and in different directions. These materials show a pronounced anisotropy at all tested temperatures. No matter the loading, the transversal direction is always found to be far less resistant than the longitudinal one. This anisotropy is mainly observed in terms of damage mechanisms, with intergranular fracture preferentially occurring along the extrusion direction. This intergranular fracture mode leads to very low and anisotropic toughness values and to the absence of tertiairy creep stage, pointing out the unstable nature of fracture, even at high temperature. The unrealistically high values of the Norton exponent measured in creep suggests the existence of a threshold stress, which is consistent with the mainly kinematic nature of the stress as revealed by fatigue tests.

  10. Forming limit and fracture mechanism of ferritic stainless steel sheets

    International Nuclear Information System (INIS)

    Research highlights: → Forming limit curves of two ferritic stainless steel sheets were well predicted. → Failure occurs by necking in uniaxial and plane strain tension for both materials. → Failure occurs by shearing in balanced biaxial tension for both materials. → Strain rate sensitivity does not affect the limit strains a lot for both materials. → Strain rate sensitivity likely influences the failure mode for both materials. - Abstract: In this work, the forming limit curves (FLCs) of two ferritic stainless steel sheets, AISI409L and AISI430, were predicted with the Marciniak-Kuczynski (MK) and Bressan-William-Hill (BWH) models, combined with the Yld2000-2d yield function and the Swift hardening law. Uniaxial tension, disk compression and hydraulic bulge tests were performed to determine the yield loci and hardening curves of both materials. Meanwhile, the strain rate sensitivity (SRS) coefficient was measured through uniaxial tension tests carried out at different strain rates. Out-of-plane stretching tests were conducted in sheet specimens to obtain the surface limit strains under different linear strain paths. Micrographs of the specimens fractured in different stress states were obtained by optical and scanning electron microscopy. The overall results show that the BWH model can predict the FLC better than the MK model, and that the SRS does not have much effect on the limit strains for both materials. The predicted FLCs and micrograph analysis both indicate that failure occurs by surface localized necking in uniaxial and plane strain tension states, whereas it occurs by localized shearing in the through thickness direction in balanced biaxial tension state.

  11. Microstructure and toughness of Cr-W and Cr-V ferritic steels

    International Nuclear Information System (INIS)

    In order to obtain an optimum alloy composition of reduced-activation Cr-W-V ferritic steels, the microstructural evolution during thermal aging at 823-973 K and its effect on the toughness were investigated for simple Cr-W and Cr-V steels by means of transmission electron microscopy and Charpy impact testing. The microstructural evolution of the Cr-W steels was similar to that of the conventional Cr-Mo steels. Carbides precipitated in the martensite and the intermetallic compound Fe2W precipitated in the δ-ferrite of the Cr-W steels. On the other hand, only carbides precipitated in both the martensite and the δ-ferrite of the Cr-V steels. The effect of Cr, W and V on the thermal embrittlement is discussed by taking account of the precipitation behavior. (orig.)

  12. Low Cost Ferritic Stainless Steel in Dye Sensitized Solar Cells with Cobalt Complex Electrolyte

    OpenAIRE

    Miettunen, Kati; Jouttijärvi, Sami; Jiang, Roger; Saukkonen, Tapio; Romu, Jyrki; Halme, Janne; Lund, Peter

    2014-01-01

    Cheap ferritic stainless steel is applied here as the counter electrode substrate in dye sensitized solar cells with cobalt complex electrolyte. A 5.0% efficiency was reached with these type of cells which is more than 2.5 times higher compared to previously reported devices with metal counter electrode and cobalt complex electrolyte. The electrochemical impedance spectra analysis showed that the best cells with the ferritic steel counter electrode had as low charge transfer resistance (3.6 Ω...

  13. A Comparison of Creep Rupture Strength of Ferritic/Austenitic Dissimilar Weld Joints of Different Grades of Cr-Mo Ferritic Steels

    Science.gov (United States)

    Laha, K.; Chandravathi, K. S.; Parameswaran, P.; Goyal, Sunil; Mathew, M. D.

    2012-04-01

    Evaluations of creep rupture properties of dissimilar weld joints of 2.25Cr-1Mo, 9Cr-1Mo, and 9Cr-1MoVNb steels with Alloy 800 at 823 K were carried out. The joints were fabricated by a fusion welding process employing an INCONEL 182 weld electrode. All the joints displayed lower creep rupture strength than their respective ferritic steel base metals, and the strength reduction was greater in the 2.25Cr-1Mo steel joint and less in the 9Cr-1Mo steel joint. Failure location in the joints was found to shift from the ferritic steel base metal to the intercritical region of the heat-affected zone (HAZ) of the ferritic steel (type IV cracking) with the decrease in stress. At still lower stresses, the failure in the joints occurred at the ferritic/austenitic weld interface. The stress-life variation of the joints showed two-slope behavior and the slope change coincided with the occurrence of ferritic/austenitic weld interface cracking. Preferential creep cavitation in the soft intercritical HAZ induced type IV failure, whereas creep cavitation at the interfacial particles induced ferritic/austenitic weld interface cracking. Micromechanisms of the type IV failure and the ferritic/austenitic interface cracking in the dissimilar weld joint of the ferritic steels and relative cracking susceptibility of the joints are discussed based on microstructural investigation, mechanical testing, and finite element analysis (FEA) of the stress state across the joint.

  14. MODELING OF FERRITE GRAIN GROWTH OF LOW CARBON STEELS DURING HOT ROLLING

    Institute of Scientific and Technical Information of China (English)

    Y.T. Zhang; D.Z. Li; Y.Y. Li

    2002-01-01

    For most commercial steels the prediction of the final properties depends on accuratelycalculating the room temperature ferrite grain size. A grain growth model is proposedfor low carbon steels Q235B during hot rolling. By using this model, the initial ferritegrain size after continuous cooling and ferrite grain growing in coiling procedure canbe predicted. Finally, in-plant trials were performed in the hot strip mill of Ansteel.The calculated final ferrite grain sizes are in good agreement with the experimentalones. It is helpful both for simulation of microstructure evolution and prediction ofmechanical properties.

  15. Characteristics of Retained Austenite in TRIP Steels with Bainitie Ferrite Matrix

    Institute of Scientific and Technical Information of China (English)

    ZHANG Mingya; ZHU Fuxian; DUAN Zhengtao; MA Shieheng

    2011-01-01

    Heat treatment process for producing cold rolled transformation induced plasticity-aided (TRIP-aided) steels with bainitic ferrite matrix was adopted.Characteristics of retained austenite (RA) in such TRIP steels were investigated.SEM and OM determination results showed that the stable austenite retained at room temperature were mainly located between laths and some of them inside the coarse ferrite.The grains were uniformly distributed in heat treated steel matrix and the regularly dispersed RA represented to be triangular morphology.XRD analysis indicated that RA content in matrix was not less than 10%,and TEM testified that RA inside the matrix were formed at the prior austenite boundaries and represented to be single or twin crystals.The ductile fracture originated from the boundaries of martensite islands from RA and ferrite.The cracks propagated along grain boundaries and some passed through the large ferrite grains and induced transgranular fracture.

  16. Modelling of Nb influence on phase transformation behaviours from austenite to ferrite in low carbon steels

    Science.gov (United States)

    Wang, L.; Parker, S. V.; Rose, A. J.; West, G. D.; Thomson, R. C.

    2016-03-01

    In this paper, a new model has been developed to predict the phase transformation behaviours from austenite to ferrite in Nb-containing low carbon steels. The new model is based on some previous work and incorporates the effects of Nb on phase transformation behaviours, in order to make it applicable for Nb-containing steels. Dissolved Nb atoms segregated at prior austenite grain boundaries increase the critical energy for ferrite nucleation, and thus the ferrite nucleation rate is decreased. Dissolved Nb atoms also apply a solute drag effect to the moving transformation interface, and the ferrite grain growth rate is also decreased. The overall transformation kinetics is then calculated according to the classic Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. The new model predictions are quite consistent with experimental results for various steels during isothermal transformations or continuous cooling.

  17. Irradiation response of ODS ferritic steels to high-energy Ne ions at HIRFL

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.H., E-mail: c.h.zhang@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Yang, Y.T.; Song, Y. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Chen, J. [Paul Scherrer Institut, Villigen PSI (Switzerland); Zhang, L.Q. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Jang, J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kimura, A. [Institute of Advanced Energy, Kyoto University, Kyoto (Japan)

    2014-12-15

    Two kinds of ODS high-Cr ferritic steels (commercial MA956 and an Al-free 16Cr–0.1Ti ODS ferritic steel) and one conventional ferritic/martensitic steel (T122) were irradiated at about 440 °C with high-energy {sup 20}Ne-ions in HIRFL. Successively increasing doses from 350 to 900 appm of Ne concentration, corresponding to atomic displacement levels from 0.7 to 1.8 dpa, were approached. A nearly uniform distribution of Ne concentration and atomic displacement damage was produced through the thickness of 60 μm of the specimens by using an energy degrader. Mechanical properties of the specimens were tested with the small-ball punch technique. The test at room temperature shows a less significant ductility loss in the ODS ferritic steel MA956 than in the T122 irradiated to the same dose of 350 appm Ne/0.7 dpa. The test at 500 °C shows that the Al-free 16Cr–0.1Ti ODS ferritic steel does not exhibit observable loss of ductility even to the highest dose level (900 appm Ne/1.8 dpa). An investigation with transmission electron microscopy (TEM) shows that voids with a diameter up to 70 nm were formed at grain boundaries in the conventional ferritic/martensitic steel T122 while only smaller bubbles were formed at the oxides/substrate interfaces in the ODS ferritic steel MA956. Mechanisms underlying the difference of irradiation response of the steels are discussed.

  18. Electrochemical and passivation behavior investigation of ferritic stainless steel in simulated concrete pore media.

    Science.gov (United States)

    Luo, Hong; Su, Huaizhi; Dong, Chaofang; Xiao, Kui; Li, Xiaogang

    2015-12-01

    The applications of stainless steel are one of the most reliable solutions in concrete structures to reduce chloride-induced corrosion problems and increase the structures service life, however, due to high prices of nickel, especially in many civil engineering projects, the austenitic stainless steel is replaced by the ferritic stainless steels. Compared with austenite stainless steel, the ferritic stainless steel is known to be extremely resistant of stress corrosion cracking and other properties. The good corrosion resistance of the stainless steel is due to the formation of passive film. While, there is little literature about the electrochemical and passive behavior of ferritic stainless steel in the concrete environments. So, here, we present the several corrosion testing methods, such as the potentiodynamic measurements, EIS and Mott-Schottky approach, and the surface analysis methods like XPS and AES to display the passivation behavior of 430 ferritic stainless steel in alkaline solution with the presence of chloride ions. These research results illustrated a simple and facile approach for studying the electrochemical and passivation behavior of stainless steel in the concrete pore environments. PMID:26501086

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-06-01

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

  20. Electrochemical and passivation behavior investigation of ferritic stainless steel in simulated concrete pore media.

    Science.gov (United States)

    Luo, Hong; Su, Huaizhi; Dong, Chaofang; Xiao, Kui; Li, Xiaogang

    2015-12-01

    The applications of stainless steel are one of the most reliable solutions in concrete structures to reduce chloride-induced corrosion problems and increase the structures service life, however, due to high prices of nickel, especially in many civil engineering projects, the austenitic stainless steel is replaced by the ferritic stainless steels. Compared with austenite stainless steel, the ferritic stainless steel is known to be extremely resistant of stress corrosion cracking and other properties. The good corrosion resistance of the stainless steel is due to the formation of passive film. While, there is little literature about the electrochemical and passive behavior of ferritic stainless steel in the concrete environments. So, here, we present the several corrosion testing methods, such as the potentiodynamic measurements, EIS and Mott-Schottky approach, and the surface analysis methods like XPS and AES to display the passivation behavior of 430 ferritic stainless steel in alkaline solution with the presence of chloride ions. These research results illustrated a simple and facile approach for studying the electrochemical and passivation behavior of stainless steel in the concrete pore environments.

  1. In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

    KAUST Repository

    Itty, Pierre-Adrien

    2014-06-01

    In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover. © 2014 Elsevier Ltd.

  2. Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA Low-Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    CAO Jian-chun; LIU Qing-you; YONG Qi-long; SUN Xin-jun

    2007-01-01

    Using thermomechanical simulation experiment, the kinetics of the isothermal transformation of austenite to ferrite in two HSLA low-carbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation. The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism, wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation, whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs, wherein, the nucleation rate of ferrite in the initial stage of transformation is low, and in the second stage,the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete. Using carbon extraction replica TEM, niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite. The mechanism of the effect of niobium on the isothermal transformation was discussed.

  3. ROLE OF STRUCTURE IS IN THE PROCESS OF FERRITIC-PEARLITIC STEEL EROSION

    Directory of Open Access Journals (Sweden)

    O. A. Kuzin

    2010-09-01

    Full Text Available The results of study of influence of structure on mechanical properties and behavior of ferrite-perlite steels under the action of contact loads are presented. It is shown that the formation of the widmanstatten pattern has a negative impact on the performance of steels under static loads but a positive effect on their durability.

  4. CYCLIC RECRYSTALLIZATION OF FERRITE IN HOT-ROLLED LOW-CARBON SHEET STEEL WITH STRUCTURETEXTURAL HETEROGENEITY

    Directory of Open Access Journals (Sweden)

    A. M. Nesterenko

    2009-01-01

    Full Text Available It is determined that in the process of soaking at subcritical temperature 680 °C in hot-rolled rolling of low-carbon steel 08 ps recrystallization is developed with heterogeneous fu ll repeat change of the steel ferrite change by its section.

  5. Effect of tin addition on the microstructure and properties of ferritic stainless steel

    Institute of Scientific and Technical Information of China (English)

    Yang Li; Ji-peng Han; Zhou-hua Jiang; Pan He

    2015-01-01

    This article reports the effects of Sn on the inclusions as well as the mechanical properties and hot workability of ferritic stainless steel. Precipitation phases and inclusions in Sn-bearing ferritic stainless steel were observed, and the relationship between the workability and the microstructure of the steel was established. Energy-dispersive X-ray spectroscopic analysis of the steel reveals that an almost pure Sn phase forms and MnS–Sn compound inclusions appear in the steel with a higher Sn content. Little Sn segregation was observed in grain boundaries and in the areas around sulfide inclusions;however, the presence of Sn does not adversely affect the workability of the steel con-taining 0.4wt%Sn. When the Sn content is 0.1wt%–0.4wt%, Sn improves the tensile strength and the plastic strain ratio and also improves the plasticity with increasing temperature. A mechanism of improving the workability of ferritic stainless steel induced by Sn addition was discussed:the presence of Sn lowers the defect concentration in the ultra-pure ferritic lattice and the good distribution of tin in the lattice overcomes the problem of hot brittleness that occurs in low-carbon steel as a result of Sn segregation.

  6. Diffusion of Nickel into Ferritic Steel Interconnects of Solid Oxide Fuel/Electrolysis Stacks

    DEFF Research Database (Denmark)

    Molin, Sebastian; Chen, Ming; Bowen, Jacob R.;

    2013-01-01

    a limited number of studies have been devoted to the phenomenon. Here, diffusion of Ni into ferritic Crofer 22 APU steel is studied in a wet hydrogen atmosphere after 250 hours of exposure at 800 °C using Ni-plated (~ 10 micron thick coatings) sheet steel samples as a model system. Even after...

  7. Thermal fatigue crack propagation behaviour of F82H ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kudo, Yusuke E-mail: kudou@fusion.naka.jaeri.go.jp; Kikuchi, Kouichi; Saito, Masakatsu

    2002-12-01

    This paper presents an issue obtained from thermal fatigue research, which attempts to examine the fusion reactor first wall by fracture mechanics. The research is organised with two different approaches: 1. Studies of the thermal fatigue crack propagation behaviour on notched 5-mm thick plate specimens of ferritic steel F82H (9Cr-1W), compared with 9Cr-1Mo ferritic steel and type 316 stainless steel; 2. Numerical simulations of the stress field caused by thermal loads including fracture mechanics. It is concluded that the stress intensity factor {delta}K{sub I} is substantial for crack growth while cyclic thermal loading.

  8. Boron effects on the ductility of a nano-cluster-strengthened ferritic steel

    International Nuclear Information System (INIS)

    Research highlights: → Cu-rich nano-particle precipitation strengthens the ferritic steels. → Boron doping suppresses brittle intergranular fracture. → Moisture-induced environmental embrittlement can be alleviated by surface coating. - Abstract: The mechanical properties of Cu-rich nano-cluster-strengthened ferritic steels with and without boron doping were investigated. Tensile tests at room temperature in air showed that the B-doped ferritic steel has similar yield strength but a larger elongation than that without boron doping after extended aging at 500 deg. C. There are three mechanisms affecting the ductility and fracture of these steels: brittle cleavage fracture, week grain boundaries, and moisture-induced hydrogen embrittlement. Our study reveals that boron strengthens the grain boundary and suppresses the intergranular fracture. Furthermore, the moisture-induced embrittlement can be alleviated by surface coating with vacuum oil.

  9. Rupture character of steels with ferrite-pearlite structure under influence of liquid metallic media

    International Nuclear Information System (INIS)

    Influence of liquid metal environment (gallium base alloy with melting point of 5 deg C) on mechanical properties and fracture mode was studied for ferritic-pearlitic steels with 0.03-0.8 % C under static and cyclic loading. Liquid metal medium was found to assist plastic deformation in a surface layer and to change fracture mode. It was revealed that the liquid of metal deteriorated steel properties in case of static loads but this effect weakened when passing from ferrite to pearlite. In ferritic steel under cycling loading the liquid metal affected so that shifted cracking resistance value to the region of lower stress intensity factors and promoted transition from intragranular fracture to intergranular one. Pearlitic steels behaved alike under cyclic loading both in liquid metal and in the air

  10. Alloying design of oxide dispersion strengthened ferritic steel for long life FBRs core materials

    Science.gov (United States)

    Ukai, S.; Harada, M.; Okada, H.; Inoue, M.; Nomura, S.; Shikakura, S.; Asabe, K.; Nishida, T.; Fujiwara, M.

    1993-09-01

    Oxide dispersion strengthened (ODS) ferritic steels with excellent swelling resistance and superior high temperature strength are prospective cladding materials for advanced fast breeder reactors. The addition of Ti in 13Cr-3W ODS ferritic steels improved the high temperature strength remarkably by the formation of uniformly distributed ultra-fine oxide particles. ODS ferritic steels have a bamboo-like grain structure and a strong deformation texture. The decrease of creep rupture strength in the bi-axial direction compared to the uni-axial direction is attributed mainly to this unique bamboo grain structure. Nearly equivalent creep rupture strength for both bi-axial and uni-axial direction was successfully attained by introducing the α to γ transformation in ODS martensitic steel.

  11. Deformation response of ferrite and martensite in a dual-phase steel

    International Nuclear Information System (INIS)

    Deformation response of ferrite and martensite in a commercially produced dual-phase sheet steel with a nominal composition of 0.15% C–1.45% Mn–0.30% Si (wt.%) was characterized by nanoindentation and uniaxial compression of focused ion beam-milled cylindrical micropillars (1–2 μm diameter). These experiments were conducted on as-received and pre-strained specimens. The average nanoindentation hardness of ferrite was found to increase from ∼2 GPa in the as-received condition to ∼3.5 GPa in the specimen that had been pre-strained to 7% plastic tensile strain. Hardness of ferrite in the as-received condition was inhomogeneous: ferrite adjacent to ferrite/martensite interface was ∼20% harder than that in the interior, a feature also captured by micropillar compression experiments. Hardness variation in ferrite was reversed in samples pre-strained to 7% strain. Martensite in the as-received condition and after 5% pre-strain exhibited large scatter in nanoindentation hardness; however, micropillar compression results on the as-received and previously deformed steel specimens demonstrated that the martensite phase in this steel was amenable to plastic deformation and rapid work hardening in the early stages of deformation. The observed microscopic deformation characteristics of the constituent phases are used to explain the macroscopic tensile deformation response of the dual-phase steel

  12. Microstructure and Mechanical Properties of a Nitride-Strengthened Reduced Activation Ferritic/Martensitic Steel

    Science.gov (United States)

    Zhou, Qiangguo; Zhang, Wenfeng; Yan, Wei; Wang, Wei; Sha, Wei; Shan, Yiyin; Yang, Ke

    2012-12-01

    Nitride-strengthened reduced activation ferritic/martensitic (RAFM) steels are developed taking advantage of the high thermal stability of nitrides. In the current study, the microstructure and mechanical properties of a nitride-strengthened RAFM steel with improved composition were investigated. Fully martensitic microstructure with fine nitrides dispersion was achieved in the steel. In all, 1.4 pct Mn is sufficient to suppress delta ferrite and assure the steel of the full martensitic microstructure. Compared to Eurofer97, the steel showed similar strength at room temperature but higher strength at 873 K (600 °C). The steel exhibited very high impact toughness and a low ductile-to-brittle transition temperature (DBTT) of 243 K (-30 °C), which could be further reduced by purification.

  13. Microstructure evolution and mechanical properties of eutectoid steel with ultrafine or fine (ferrite+cementite) structure

    International Nuclear Information System (INIS)

    Eutectoid steel with the ultrafine or fine-grained ferrite (α)+cementite (θ) particles structure was formed by hot deformation of undercooled austenite at 0.1 s−1 or 5 s−1 at 650 °C using a Gleeble 1500 hot simulator and subsequent annealing. The microstructural evolution of fine (α+θ) structure was investigated by means of a scanning electronic microscope, electron backscattered diffraction and transmission electron microscope, and the mechanical properties of fine (α+θ) steel were analyzed in comparison with that of ultrafine (α+θ) steel. The results show that only dynamic transformation of undercooled austenite into proeutectoid ferrite occurs during hot deformation at 650 °C at 5 s−1. During water quenching, lamellar pearlite with small colony sizes is formed and the average size of pearlite colonies decreases with increasing the strain. By subsequent annealing at 650 °C for 30 min, the spheroidization of lamellar pearlite takes place, resulting in the formation of fine (α+θ) structure consisting of ferrite matrix with the average size of about 4.9 μm and fine cementite particles mainly within ferrite grains. In comparison with ultrafine (α+θ) steel consisting of ferrite matrix with the average size of about 1.8 μm and relatively large cementite particles mostly located at grain boundaries, the yield strength, tensile strength, uniform elongation, total elongation and work-hardening capability of fine (α+θ) steel improve markedly

  14. Toughening mechanisms of a high-strength acicular ferrite steel heavy plate

    Science.gov (United States)

    Cao, Zhi-Qiang; Bao, Yan-Ping; Xia, Zheng-Hai; Luo, Deng; Guo, Ai-Min; Wu, Kai-Ming

    2010-10-01

    An ultra-low carbon acicular ferrite steel heavy plate was obtained with an advanced thermo-mechanical control process-relaxed precipitation controlled transformation (TMCP-RPC) at Xiangtan Steel, Valin Group. The heavy plate has a tensile strength of approximately 600 MPa with a lower yield ratio. The impact toughness of the heavy plate achieves 280 J at -40°C. The fine-grained mixed microstructures of the heavy plate mainly consist of acicular ferrite, granular bainite, and polygonal ferrite. The high strength and excellent toughness of the heavy plate are attributed to the formation of acicular ferrite microstructure. The prevention of blocks of martensite/retained austenite (M/A) and the higher cleanness are also responsible for the superior toughness.

  15. Ferritic stainless steel composite slabs : Experimental study of longitudinal shear transfer

    OpenAIRE

    Ferrer Ballester, Miquel; Marimón Carvajal, Federico; Arrayago Luquin, Itsaso; Mirambell Arrizabalaga, Enrique

    2014-01-01

    The objective of this work is to carry out the procedure described in Eurocode 4 to evaluate the longitudinal shear transfer capability of conventional steel sheeting open-rib profile with embossments, usually rolled in conventional galvanized steel, being rolled now in ferritic stainless steel 1.4003 alloy. Finally, the results of both composite floor slabs are compared. Two methodologies have been used to evaluate the longitudinal shear resistance in composite slabs, the m-k method and t...

  16. Grain size distribution after similar and dissimilar gas tungsten arc welding of a ferritic stainless steel

    OpenAIRE

    Ranjbarnodeh E.; Serajzadeh S.; Kokabi A.H.; Fischer A

    2015-01-01

    In this study, gas tungsten arc welding of ferritic stainless steel and grain size distribution in heat affected zone of the welded samples were investigated. Both similar and dissimilar arc welding operations were considered where in dissimilar welding joining of stainless steel to mild steel was examined. In the first stage, a three-dimensional model was developed to evaluate temperature field during and after arc welding while the model was performed usi...

  17. Lead-bismuth eutectic corrosion behaviors of ferritic/martensitic steels in low oxygen concentration environment

    OpenAIRE

    Liu, Jian; Shi, Quanqiang; Luan, He; Yan, Wei; Sha, Wei; Wang, Wei; Shan, Yiyin; Yang, Ke

    2015-01-01

    In order to investigate the compatibility of candidate structural materials with liquid metals, two kinds of ferritic/martensitic steels were chosen to contact with lead–bismuth eutectic in sealed quartz–glass tubes. The corrosion exposures were for 500 and 3000 h. Results showed that the oxidation layer and carbide dissolution layer on the two steels grew with contact time under oxygen unsaturated condition. Short-term corrosion behavior of a newly developed steel showed better lead–bismuth ...

  18. Microstructure, mechanical properties and corrosion behavior of laser welded dissimilar joints between ferritic stainless steel and carbon steel

    International Nuclear Information System (INIS)

    Highlights: • Laser welding of ferritic stainless steel to carbon steel joints was made. • The microstructure of this dissimilar joint is lath martensite and ferrite. • Decarburized layer and type II grain boundary was observed in joints. • The hardness distribution of two heat input joints across interface were analyzed. • Ecorr of dissimilar joint is between two base metals and joint has greatest icorr. - Abstract: The joint of dissimilar metals between ferritic stainless steel (FSS) and low carbon steel (CS) are welded by laser beam with two different welding speeds: 12 mm/s and 24 mm/s. Microstructure of dissimilar joint were investigated using optical microscope, X-ray diffraction and scanning electron microscope. The results show that the microstructure of this dissimilar joint is lath martensite and few ferrite, upper bainite and widmanstatten ferrite formed in heat-affected zone (HAZ) of CS. An increase of welding speed leads to narrower HAZ of CS and higher hardness of weld bead close to FSS side. The joints with different welding speed have similar ultimate tensile strength but superior elongation is obtained of high welding speed joint. Electrochemical corrosion test indicates the corrosion potential of dissimilar joint falls in between FSS and CS. And dissimilar joint has greatest corrosion current density which is attributed to the effect of galvanic corrosion

  19. Optimization of Ferrite Number of Solution Annealed Duplex Stainless Steel Cladding Using Integrated Artificial Neural Network: Simulated Annealing

    OpenAIRE

    V. Rathinam; T. Kannan

    2014-01-01

    Cladding is the most economical process used on the surface of low carbon structural steel to improve the corrosion resistance. The corrosion resistant property is based on the amount of ferrite present in the clad layer. Generally, the ferrite content present in the layer is expressed in terms of Ferrite Number (FN). The optimum range of ferrite number provides adequate surface properties like chloride stress corrosion cracking resistance, pitting and crevice corrosion resistance and mechani...

  20. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    OpenAIRE

    Rômulo Ribeiro Magalhães de Sousa; Francisco Odolberto de Araújo; José Alzamir Pereira da Costa; Antonio Maia de Oliveira; Mineia Sampaio Melo; Clodomiro Alves Junior

    2012-01-01

    AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN), with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  1. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Directory of Open Access Journals (Sweden)

    Rômulo Ribeiro Magalhães de Sousa

    2012-04-01

    Full Text Available AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN, with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

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

    Science.gov (United States)

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

    2015-12-01

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

  3. Effect of microstructure on the fracture toughness of ferrite-martensite-bainite steels

    International Nuclear Information System (INIS)

    The effect of microstructure on the fracture toughness of ferrite-martensite -bainite steels was investigated with Fe-0.11C-1.64Mn-0.78Si composition. One inch compact tension specimens (1T-CTSs) were machined from hot rolled plates. The microstructure of ferrite-martensite-bainite was introduced to the specimens by the heat treatment of intercritical annealing at 800deg C and isothermal holding at 350deg C. Holding at 350deg C increased volume fraction of bainite, while decreased that of martensite, and refined martensite particles. Single specimen unloading compliance method was used in fracture test to obtain J-resistance (J-R) curve and to determine the fracture toughness(JIC). Introduction of bainite to the ferrite-martensite steel improved the fracture toughness due to the deformation of bainite which relaxed the stress concentration on the interface of ferrite and martensite. Observation of fracto-graphs through the scanning electron microscope(SEM) identified the fracture mechanism of ferrite-martensite-bainite steels as dimple nucleation and crack growth by decohesion of ferrite matrix and second phase particles and by microvoid coales cence. (Author)

  4. 46 CFR 54.25-10 - Low temperature operation-ferritic steels (replaces UCS-65 through UCS-67).

    Science.gov (United States)

    2010-10-01

    ... VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1) and... 46 Shipping 2 2010-10-01 2010-10-01 false Low temperature operation-ferritic steels (replaces UCS....25-10 Low temperature operation—ferritic steels (replaces UCS-65 through UCS-67). (a) Scope. (1)...

  5. Intergranular stress corrosion cracking of welded ferritic stainless steels in high temperature aqueous environments

    Energy Technology Data Exchange (ETDEWEB)

    Fukuzuka, Toshio; Shimogori, Kazutoshi; Fujiwara, Kazuo; Tomari, Haruo (Kobe Steel Ltd. (Japan). Central Research and Development Lab.); Kanda, Masao

    1982-07-01

    In considering the application of ferritic stainless steels to heat exchanger tubing materials for moisture separator-reheaters in LWRs, the effects of environmental conditions (temperature, chloride, dissolved oxygen, pH), thermal history, and steel composition (content of C, N, Cr and Ti) on the Inter-Granular Stress Corrosion Cracking (IGSCC) in high temperature aqueous environments, were studied. The IGSCC was proved to depend on steel composition and thermal history rather than environment. From these results, a steel was designed to prevent IGSCC of the welding HAZ for 18Cr and 13Cr steels.

  6. Synthesis and Characterization of Oxide Dispersion Strengthened Ferritic Steel via a Sol-Gel Route

    Institute of Scientific and Technical Information of China (English)

    孙钦星; 张涛; 王先平; 方前锋; 胡菁; 刘长松

    2012-01-01

    Nanocrystalline oxide dispersion strengthened (ODS) ferritic steel powders with nominal composition of Fe-14Cr-3W-0.3Ti-0.4Y2O3 are synthesized using sol-gel method and hy- drogen reduction. At low reduction temperature the impurity phase of CrO is detected. At higher reduction temperature the impurity phase is Cr2O3 which eventually disappears with increasing reduction time. A pure ODS ferritic steel phase is obtained after reducing the sol-gel resultant products at 1200℃ for 3 h. The HRTEM and EDS mapping indicate that the Y2O3 particles with a size of about 15 nm are homogenously dispersed in the alloy matrix. The bulk ODS ferritic steel samples prepared from such powders exhibit good mechanical performance with an ultimate tensile stress of 960 MPa.

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

    Directory of Open Access Journals (Sweden)

    Ovri Henry

    2008-03-01

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

  8. Hydrogen-induced defects in austenite and ferrite of a duplex steel.

    Science.gov (United States)

    Głowacka, A; Swiatnicki, W A; Jezierska, E

    2006-09-01

    The influence of hydrogen on the microstructure of two types of austeno-ferritic duplex stainless steel (Cr26-Ni6 model steel and Cr22-Ni5-Mo3 commercial steel), each of them after two thermo-mechanical treatments, was investigated. The aim of this study was to reveal microstructural changes appearing during the hydrogen charging and particularly to clarify the occurrence of phase transformations induced by hydrogen. The specific microstructural changes in the ferrite (alpha) and austenite (gamma) of both types of steel were observed. A strong increase of dislocation density was noticed in the alpha phase. In the case of model steel, longer hydrogen charging times led to significant ferrite grain refinement. In the commercial steel, the strips and twin plates appeared in the ferrite after hydrogenation. The appearance of stacking faults was revealed in the gamma phase. The martensite laths appeared in austenite after longer hydrogenation times. It seems that the microstructural changes gave rise to the formation of microcracks in the alpha and gamma phases as well as on the alpha/gamma interphase boundaries. PMID:17059551

  9. Ferrite morphology and residual phases in continuously cooled low carbon steels

    International Nuclear Information System (INIS)

    Although much research has been conducted on the isothermal transformation products of medium to high carbon hardenable steels, relatively little has been reported for transformation of low carbon structural steels under continuous cooling conditions. The trend towards reduced carbon levels (less than about 0.1 wt% C) has been driven by demands for formability and weldability, challenging steel designers to maintain strength by microalloying and/or thermomechanical controlled processing. Although control of the ferritic products formed in low carbon steels after hot rolling, normalising and welding is essential in order to ensure adequate strength and toughness, understanding of the microstructures formed on continuous cooling is still limited. In addition, transformation mechanisms remain controversial because of polarisation of researchers into groups championing diffusional and displacive theories for the transformation of austenite over a wide range of cooling rates. The present review compares and draws together the main ferrite classification schemes, and discusses some critical issues on kinetics and mechanisms, in an attempt to rationalise the effects of cooling rate, prior austenite structure and composition on the resulting ferrite structure and its mechanical properties. It is concluded that with increasing cooling rate the ferritic product becomes finer, more plate-like, more dislocated, more carbon supersaturated, more likely to be formed by a displacive mechanism, harder and stronger. Other conclusions are that: (i) 'bainitic ferrite', which is a pervasive form of ferrite in continuously cooled low carbon steels, is different from the conventional upper and lower bainites observed in higher carbon steels, insofar as the co-product 'phase' is typically martensite-austenite islands rather than cementite; and (ii) low carbon bainite rather than martensite is the dominant product at typical fast cooling rates (<500K/s) associated with commercial

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

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, RL

    2005-01-31

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

  11. Ferrite and austenite phase identification in duplex stainless steel using SPM techniques

    Science.gov (United States)

    Guo, L. Q.; Lin, M. C.; Qiao, L. J.; Volinsky, Alex A.

    2013-12-01

    It can be challenging to properly identify the phases in electro-polished duplex stainless steel using optical microscopy or other characterization techniques. This letter describes magnetic force microscopy to properly identify the phases in electropolished duplex stainless steel. The results are also confirmed with the current sensing atomic force and scanning Kelvin probe force microscopy. The difference in topography heights between the ferrite and austenite phases is attributed to the different etching rates during electropolishing, although these phases have different mechanical properties. The current in the austenite is much higher compared with the ferrite, thus current sensing atomic force microscopy can also be used to properly identify the phases.

  12. Interfacial Microstructure of Diffusion Bonded Inconel 738 and Ferritic Stainless Steel Couple

    Institute of Scientific and Technical Information of China (English)

    Bulent Kurt; Mustafa Ulutan

    2009-01-01

    In this study, Inconel 738 alloy was diffusion bonded to a ferritic stainless steel. The effect of bonding temperature on the microstructural development across the joint region was investigated. Following the diffusion bonding, conventional characterization techniques such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and microhardness were used to examine the interfacial microstructure. It was seen that bonding temperature was effective on the diffusion of Ni from Inconel 738 to ferritic stainless steel that affected the microstructure of the interface. Austenite phase was formed at the interface as a result of Ni diffusion from the Inconel 738 to the interface.

  13. Effect of δ-ferrite on the low cycle fatigue behavior of 12CrMoV steel

    International Nuclear Information System (INIS)

    The 12CrMoV steel subjected to high temperature will inevitably contain some δ-ferrite. The presence of δ-ferrite in this steel has been known to lead to discontinuites in the mechanical properties because of compositional differences and lack of cohesin between δ-ferrite and tempered martensite matrix. The strain controlled fatigue test was carried out to investigate the effect of δ-ferrite on the low cycle fatigue behavior of the 12CrMoV steel at room temperature. Two different microstructures, tempered martensite with and without δ-ferrite, were developed by heat treatment schedules. The tensile properties for the two different specimen conditions were very similar. The cyclic behavior was characterized by softening and the plastic strain range vs. the number of reversals plots obeyed the Manson-Coffin relationship. The fatigue crack propagation mode was a transgranular. However, the specimen with δ-ferrite had a longer fatigue life than that without δ-ferrite. Introduction of δ-ferrite resulted in the increase of cyclic strain hardening exponent and the more plastic work required to failure. The δ-ferrite had influence on the crack path as a soft obstacle, which resulted that the crack passed around δ-ferrite. An excess energy was required to propagate the crack and led locally to a decrease in crack growth rate. Therefore, the presence of δ-ferrite in tempered martensite increased the resistance to crack propagation and resulted in the increase in fatigue life

  14. Performance Evaluation of Advanced Ferritic/Martensitic Steels for a SFR Fuel Cladding

    International Nuclear Information System (INIS)

    High-chromium(9-12 wt.%) ferritic/martensitic steels are currently being considered as candidate materials for cladding and duct applications in a Gen-IV SFR (sodium-cooled fast reactor) nuclear system because of their higher thermal conductivities and lower expansion coefficients as well as excellent irradiation resistance to void swelling when compared to austenite stainless steels. Since the operation condition in the design of Gen-IV SFR would be envisioned to be harsh from the viewpoints of temperature (≥600 .deg. C) and irradiation dose (≥200 dpa), the primary emphasis is on the fuel cladding materials, i.e. high-Cr ferritic/martensitic steels. The ferritic/martensitic steels for the fuel cladding are commonly used in a 'normalized and tempered' condition. This heat treatment involves a solutionizing treatment (austenitizing) that produces austenite and dissolves the M23C6 carbides and MX carbonitrides, followed by an air cooling that transforms the austenite to martensite. Precipitation sequence during a long-term creep exposure is strongly influenced by the distribution of those in the as heat treated condition of the steels. Their creep strength has been improved by their martensitic lath structure, the precipitation strengthening effects of M23C6 carbides and MX carbonitrides and the solid solution strengthening effects of Mo and W in the matrix. Especially, the precipitation strengthening effect of MX is important because its coarsening rate is small and a fine particle size is maintained for a long-term creep exposure. Z-phase formation from MX-type precipitates has been proposed as a degradation mechanism for a long-term creep regime. The ferritic/martensitic steels should need to improve their performance to be utilized in the high burn-up fuel cladding. For this purpose, KAERI has been developing advanced ferritic/martensitic steels since 2007. This study includes some performance evaluation results of the mechanical and microstructural

  15. Ferritic steels for sodium-cooled fast reactors: Design principles and challenges

    Science.gov (United States)

    Raj, Baldev; Vijayalakshmi, M.

    2010-09-01

    An overview of the current status of development of ferritic steels for emerging fast reactor technologies is presented in this paper. The creep-resistant 9-12Cr ferritic/martensitic steels are classically known for steam generator applications. The excellent void swelling resistance of ferritic steels enabled the identification of their potential for core component applications of fast reactors. Since then, an extensive knowledge base has been generated by identifying the empirical correlations between chemistry of the steels, heat treatment, structure, and properties, in addition to their in-reactor behavior. A few concerns have also been identified which pertain to high-temperature irradiation creep, embrittlement, Type IV cracking in creep-loaded weldments, and hard zone formation in dissimilar joints. The origin of these problems and the methodologies to overcome the limitations are highlighted. Finally, the suitability of the ferritic steels is re-evaluated in the emerging scenario of the fast reactor technology, with a target of achieving better breeding ratio and improved thermal efficiency.

  16. Corrosion resistance of modern austenitic-ferritic (duplex) stainless steel. Corrosion of special types. (Review)

    International Nuclear Information System (INIS)

    Recent data on resistance of modern corrosion-resistant austenitic-ferritic steels to different types of corrosion are generalized. It is shown that these steels are characterized by high resistance to general corrosion in acid, alkali, chloride and other solutions, are not inclined to intercrystalline, pitting and crevice corrosion and are noted for high resistance to corrosion cracking and corrosion fatigue. All this is combined with technological and economical effectiveness. It is advisible to use these steels instead of highly-alloyed and expensive steels and alloys in chemical, power and other industries. 59 refs.; 2 tabs

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

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

  18. Void formation and microstructural development in oxide dispersion strengthened ferritic steels during electron-irradiation

    Science.gov (United States)

    Saito, J.; Suda, T.; Yamashita, S.; Ohnuki, S.; Takahashi, H.; Akasaka, N.; Nishida, M.; Ukai, S.

    1998-10-01

    ODS ferritic steels (13Cr-0.5Ti-0.2Y 2O 3) were prepared by the mechanical alloying method followed by the hot extrusion and several heat treatments including recrystallization. ODS steels with different heat treatment and a ferritic/martensitic (F/M) steel for the reference were irradiated to 12 dpa at 670-770 K in HVEM. After recrystallization, the dislocation density decreased with increasing grain size, however, the oxide particles did not show any obvious change in the size and the number density. During the electron-irradiation the microstructure was relatively stable, i.e. oxide particles showed good stability and the dislocation density remained almost constant. A limited void formation was observed in the specimens, and the suppressive effect due to dislocations with high number density was confirmed. From these results, the behavior of microstructure and the limited void formation in ODS steels have been discussed.

  19. Effect of the delta ferrite solidification morphology of austenitic steels weld metal on the joint properties

    International Nuclear Information System (INIS)

    The properties of austenitic stainless steel weld metals are largely influenced by the appearance in the microstructure of delta ferrite of a given morphology. The susceptibility to hot cracks and low temperature toughness are deeply conditioned by the mixed complex austenitic-ferritic structures which depending on the steel chemical composition and on the cooling rate may be developed. The latest research on this issue points out the importance of the sodification mode as regards to the influence in the appearance of delta ferrite of a certain morphology. In fact, it is very important to understand the solidification sequences, the primary solidification modes which are possible and the subsequent solid state transformations to correlate the structural elements of the weld metal with the parameters of the welding process on the one had, and the weld joint properties on the other. (Author) 19 refs

  20. Radiation-induced Ostwald ripening in oxide dispersion strengthened ferritic steels irradiated at high ion dose

    OpenAIRE

    Lescoat, Marie-Laure; Chen, Y.; Marquis E., A.; Bordas, Eric; Trocellier, Patrick; Serruys, Yves; Gentils, Aurélie; Kaitasov, Odile; De Carlan, Yann; Legris, Alexandre

    2014-01-01

    Oxide dispersion strengthened (ODS) ferritic steels are considered promising candidates as cladding tubes for Generation IV nuclear reactors. In such reactors, irradiation damage can reach more than 150 dpa at temperatures ranging from 400 to 650 degrees C. Thus nanopartide stability has to be guaranteed in order to ensure that these materials possess excellent creep properties. Using Fe ions, ODS steels were irradiated at 500 degrees C up to 150 dpa. At this temperature the nano-oxide popula...

  1. Effect of Mn Addition on Microstructural Modification and Cracking Behavior of Ferritic Light-Weight Steels

    Science.gov (United States)

    Sohn, Seok Su; Lee, Byeong-Joo; Lee, Sunghak; Kwak, Jai-Hyun

    2014-11-01

    In the present study, effects of Mn addition on cracking phenomenon occurring during cold rolling of ferritic light-weight steels were clarified in relation to microstructural modification involving κ-carbide, austenite, and martensite. Four steels were fabricated by varying Mn contents of 3 to 12 wt pct, and edge areas of steel sheets containing 6 to 9 wt pct Mn were cracked during the cold rolling. The steels were basically composed of ferrite and austenite in a band shape, but a considerable amount of κ-carbide or martensite existed in the steels containing 3 to 6 wt pct Mn. Microstructural observation of the deformed region of fractured tensile specimens revealed that cracks which were initiated at ferrite/martensite interfacial κ-carbides readily propagated along ferrite/martensite interfaces or into martensite areas in the steel containing 6 wt pct Mn, thereby leading to the center or edge cracking during the cold rolling. In the steel containing 9 wt pct Mn, edge cracks were found in the final stage of cold rolling because of the formation of martensite by the strain-induced austenite to martensite transformation, whereas they were hardly formed in the steel containing 12 wt pct Mn. To prevent or minimize the cracking, it was recommended that the formation of martensite during the cooling from the hot rolling temperature or during the cold rolling should be suppressed, which could be achieved by the enhancement of thermal or mechanical stability of austenite with decreasing austenite grain size or increasing contents of austenite stabilizers.

  2. Experimental study on ferritic stainless steel simply supported and continuous beams

    OpenAIRE

    Arrayago Luquin, Itsaso; Real Saladrigas, Esther

    2015-01-01

    Development of efficient design guidance for stainless steel structures is key for the increased use of this corrosion-resistant material by considering both nonlinear behaviour and strain hardening into resistance prediction expressions, together with the moment redistribution in indeterminate structures. With the aim of analysing the bending moment redistribution capacity of ferritic stainless steel beams, a comprehensive experimental programme on continuous beams is presented. These tests ...

  3. Tests on ferritic stainless steel simply supported and continuous SHS and RHS beams

    OpenAIRE

    Arrayago Luquin, Itsaso; Real Saladrigas, Esther; Mirambell Arrizabalaga, Enrique

    2015-01-01

    Development of efficient design guidance for stainless steel structures is key for the spreading of this corrosion-resistant material by considering both nonlinear behavior and strain hardening into predicting expressions, together with allowing the consideration of moment redistribution in indeterminate structures. With the aim of analyzing the bending moment redistribution capacity in ferritic stainless steel beams (RHS and SHS), an experimental programme is presented. The tests contribute ...

  4. Multiscale Modeling of the Deformation of Advanced Ferritic Steels for Generation IV Nuclear Energy

    Energy Technology Data Exchange (ETDEWEB)

    Nasr M. Ghoniem; Nick Kioussis

    2009-04-18

    The objective of this project is to use the multi-scale modeling of materials (MMM) approach to develop an improved understanding of the effects of neutron irradiation on the mechanical properties of high-temperature structural materials that are being developed or proposed for Gen IV applications. In particular, the research focuses on advanced ferritic/ martensitic steels to enable operation up to 650-700°C, compared to the current 550°C limit on high-temperature steels.

  5. Microstructure And Mechanical Properties Of Crofer 22 APU Ferritic Stainless Steel

    OpenAIRE

    Stygar M.; Durda E.

    2015-01-01

    The objective of this work was to expand the knowledge on mechanical properties of the oxidized Crofer 22 APU Ferritic Stainless Steel. To examine adhesion of oxide scale formed on steel the scratch test was performed. Scratch test as an appropriate method for qualitative evaluation of the film adhesion to substrate has been used in many studies. Scratch properties were investigated before and after oxidation at 800°C for 500 hours in laboratory air.

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

    OpenAIRE

    Ovri Henry; Kamma Celestine Monde

    2008-01-01

    The influence of starting point microstructures on the transformation mechanisms and mechanical properties of a micro alloyed steel after annealing in the alpha + gamma region have been investigated. Three different microstructures: austenite, pearlite in a ferrite matrix and martensite were used as starting point microstructures for the production of dual (alpha + ) phase structures in the test steel. Photomicrographs obtained from metallographic examination of the heat treated samples were ...

  7. The welding of austenitic-ferritic Mo-alloyed Cr-Ni-Steel

    International Nuclear Information System (INIS)

    This paper provides general information and guidance on the welding of austenitic-ferritic Mo-alloyed Cr-Ni stainless steel. Information is given on the various chemical compositions and on resistance to corrosion and on the mechanical and physical properties of commercially available steels. The effect of welding on the base metal and the selection of welding processes and welding consumables are described

  8. Microstructure And Mechanical Properties Of Crofer 22 APU Ferritic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Stygar M.

    2015-06-01

    Full Text Available The objective of this work was to expand the knowledge on mechanical properties of the oxidized Crofer 22 APU Ferritic Stainless Steel. To examine adhesion of oxide scale formed on steel the scratch test was performed. Scratch test as an appropriate method for qualitative evaluation of the film adhesion to substrate has been used in many studies. Scratch properties were investigated before and after oxidation at 800°C for 500 hours in laboratory air.

  9. Influence of flowing sodium on the creep properties of ferritic steel R8 (EM 12)

    International Nuclear Information System (INIS)

    Uniaxial creep rupture tests have been performed on the ferritic steel R8 (type EM12) both in vacuum and in flowing sodium. The effect of sodium exposure on the creep parameters is discussed in terms of the structural and chemical changes observed. The role played by non-metallic and metallic impurities is treated in more detail. (orig.)

  10. 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...

  11. Outgassing characteristics of F82H ferritic steel as a low activation material for fusion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Odaka, Kenji; Satou, Osamu [Hitachi Ltd., Tsuchiura, Ibaraki (Japan). Mechanical Engineering Research Lab.; Ootsuka, Michio; Abe, Tetsuya; Hara, Shigemitsu; Takatsu, Hideyuki; Enoeda, Mikio

    1997-09-01

    Outgassing characteristics of F82H ferritic steel as a low activation material for the blanket of fusion device were investigated. A test chamber was constructed by welding F82H ferritic steel plates. The inner surface of the chamber was buffed and electropolished. The test chamber was degassed by the prebaking at temperature of 350degC for 20 h in vacuum. Then outgassing rates of the test chamber were measured by the throughput method as a function of pumping time for the cases that the test chamber was baked and not baked. The typical outgassing rate after baking at 250degC for 24 h was 3 x 10{sup -9} Pa{center_dot}ms{sup -1} and it seems that this value is sufficiently small to produce pressures at least as low as 10{sup -9} Pa in the vacuum chamber made of F82H ferritic steel. In the pump-down of the test chamber without baking after exposure to air, the outgassing rate decreases with pumping time and reached 1 x 10{sup -7} Pa{center_dot}ms{sup -1} at t = 10{sup 5} s. The activation energy of hydrogen in bulk diffusion in the F82H ferritic steel was measured and found to be 7 kcal/mol. (author)

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    The influence of the hardness of martensite and ferrite phases in dual phase steel on void formation has been investigated by in situ tensile loading in a scanning electron microscope. Microstructural observations have shown that most voids form in martensite by evolving four steps: plastic defor...

  13. Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects

    DEFF Research Database (Denmark)

    Chen, Ming; Molin, Sebastian; Zhang, L.;

    2015-01-01

    Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell (SOFC) or electrolysis cell (SOEC) stacks. During stack production and operation, nickel from the Ni/YSZ fuel electrode or from the Ni contact component diffuses into the IC plate, causing transformation of...

  14. A Model for Ferrite/Pearlite Band Formation and Prevention in Steels

    NARCIS (Netherlands)

    Rivera-Diaz-Del-Castillo, P.E.J.; Sietsma, J.; Van der Zwaag, S.

    2004-01-01

    A model for predicting the conditions under which ferrite/pearlite band formation occurs, and therefore the conditions in which it can be avoided in steels, has been developed. The model requires as input the alloy composition and microchemical segregation wavelength, and provides in turn the homoge

  15. Nondestructive evaluation for remanent life of aged 12Cr ferrite heat resisting steel by reversible permeability

    International Nuclear Information System (INIS)

    We present a magnetic and nondestructive method to evaluate the remanent life of advanced ferritic steel using the value of reversible permeability. The method to measure reversible permeability is based on the theory that the value of reversible permeability is the same differential of the hysteresis loop. The measurement principle is based on the foundation of harmonics voltage induced in a sensing coil using a lock-in amplifier tuned to the frequency of the exciting one. Results obtained for reversible permeability, Vickers hardness, and tensile strength on the aged samples show that the peak interval of reversible permeability, Vickers hardness and tensile strength decrease as aging time increases. We could estimate the remanent life of advanced ferritic steel by using the relationship between the peak interval of reversible permeability and the Larson–Miller parameter, non-destructively. - Highlights: ► Magnetic, nondestructive evaluation method of remanent life of 12Cr ferritic steel is presented. ► Peak interval of reversible permeability decreases with the increase of aging time. ► Mechanical properties decrease with the increase of aging time. ► Magnetic and mechanical properties are decreased with increase of Larson–Miller parameter. ► Reversible permeability is nondestructively used to estimate remanent life of 12Cr ferrite steel.

  16. Characteristics of microstructural evolution during deformation-enhanced ferrite transformation in Nb-microalloyed HSLA steel

    Institute of Scientific and Technical Information of China (English)

    Guoan Chen; Wangyue Yang; Shouzhen Guo; Zuqing Sun

    2007-01-01

    Microstructure evolution during deformation of undercooled austenite at 760 ℃ was investigated in Nb-microalloyed steel by using SEM (scanning electron microscope),TEM (transmission electron microscope),and EBSD (electron backscattered diffraction).It is indicated that during deformation-enhanced ferrite transformation (DEFT) in Nb-microalloyed steel,the incubation period is prolonged,and the higher strain is needed to accomplish ferrite transformation.Therefore,the transformation kinetics curves move to high strain parallelly; and the transformation kinetics curves of Nb-microalloyed steel can be divided into three stages.At the first stage,the solute drag effect of Nb and the consumption of strain energy for the dynamic precipitation of Nb(CN) led to a long incubation period,and at the second stage,ferrite transformation was accelerated significantly and fine Nb(CN) precipitates restrict the grain growth of ferrite effectively.The results also showed that DEFT in Nb-microalloyed steel is still a nucleation dominated process,and during the microstructure evolution the interchange of and texture was obtained.

  17. Characterization of microstructural and mechanical properties of a reduced activation ferritic oxide dispersion strengthened steel

    Science.gov (United States)

    Eiselt, Ch. Ch.; Klimenkov, M.; Lindau, R.; Möslang, A.

    2011-09-01

    For specific blanket and divertor applications in future fusion power reactors a replacement of presently considered Reduced Activation Ferritic Martensitic (RAFM) steels as structural material by suitable oxide dispersion strengthened (ODS) ferritic martensitic steels would allow a substantial increase of the operating temperature from ˜823 K to about 923 K. Temperatures above 973 K in the He cooled modular divertor concept necessitate the use of Reduced Activation Ferritic (RAF)-ODS-steels, which are not limited by a phase transition. The development concentrates on the ferritic ODS-steel Fe-13Cr-1W-0.3Ti-0.3Y 2O 3. The microstructures of a mechanically alloyed powder particle are observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ageing experiments for 1000 h and 3000 h at 1123.5 K and 1223.5 K of compacted Fe-13Cr-1W-0.3Ti-0.3Y 2O 3 were executed. The impact especially on the oxide particles in terms of segregation and decomposition effects were monitored by electron energy loss spectroscopy (EELS). Long term vacuum creep experiments have been performed with rolled Fe-13Cr-1W-0.3Ti-0.3Y 2O 3 at 923.5 K and 1023.5 K, which will be compared to reference alloys.

  18. Influence of delta ferrite on mechanical and creep properties of steel P92

    Energy Technology Data Exchange (ETDEWEB)

    Mohyla, Petr [VSB - Technical Univ. of Ostrava (Czech Republic). Faculty of Mechanical Engineering; Kubon, Zdenek [Material and Metallurgical Research Ltd., Ostrava (Czech Republic)

    2010-07-01

    This article presents some new results obtained during research of chromium modified steel P92. This steel is considered the best modified 9-12% Cr steel for the construction of modern power plants with ultra-super-critical steam parameters. High creep rupture strength of steel P92 is characterized by its chemical composition and by microstructure as well. Optimal microstructure of steel P92 is ideally composed of homogeneous martensite and fine dispersion of secondary particles. During the research program one P92 heat with an occurrence of about 20% delta ferrite was produced. The article describes the microstructure of the heat in various modes of heat treatment, as well as the results of mechanical properties tests at room temperature and also creep test results. The results are confronted with properties of other heats that have no delta ferrite. The relevance is on the significant difference while comparing of creep test results. The comparison of results brings conclusions, defining influence of delta ferrite on mechanical and creep properties of P92 steel. (orig.)

  19. The relationship between microstructure and mechanical properties of ferritic chromium steel weldments

    Energy Technology Data Exchange (ETDEWEB)

    Mayr, Peter; Cerjak, Horst [Graz Univ. of Technology (Austria); Toda, Yoshiaki; Hara, Toru; Abe, Fujio [National Institute for Materials Science (Japan)

    2008-07-01

    Welding as the major joining and repair technology for steels in thermal power plants has a significant influence on the steels microstructure and, therefore, on its properties. Heat-resistant martensitic 9-12% chromium steels show an affinity to the retention of delta ferrite in the heat-affected zone of their weldments. This is related to their high level of ferrite stabilizing alloying elements such as Cr, W or Mo. Retained delta ferrite in martensitic steel grades has a significant negative influence on creep strength, fatigue strength, toughness and oxidation resistance. In the long-term range of creep exposure, many weldments of martensitic heatresistant steels fail by Type IV cracking in the fine-grained region of the heat-affected zone. In this work, the formation of the heat-affected zone microstructures in martensitic chromium steels is studied by in-situ X-ray diffraction using synchrotron radiation, optical microscopy as well as most advanced electron microscopical methods. The observed microstructure is directly linked to the mechanical properties, i.e. ductility, toughness and creep strength. Characteristic failure modes are discussed in detail. (orig.)

  20. Mechanisms of short crack propagation in austenitic–ferritic duplex steel

    Energy Technology Data Exchange (ETDEWEB)

    Scharnweber, Michael, E-mail: michael.scharnweber@mailbox.tu-dresden.de; Tirschler, Wolfgang; Oertel, Carl-Georg; Skrotzki, Werner

    2014-02-10

    For applications requiring both high strength and high corrosion resistance, austenitic–ferritic duplex steels are often the material of choice. In this study, cyclic deformation experiments were performed on the austenitic–ferritic duplex stainless steel 1.4462. By measuring the crack opening and crack sliding displacement in situ in a scanning electron microscope, the characteristics of the different crack propagation mechanisms in the two phases are determined. In the ferritic phase, two different appearances of short cracks can be observed, one exhibiting a very smooth and the other one a rather rough surface crack path. Electron backscatter diffraction measurements on the crack-containing grains in addition with high resolution imaging of the topography of the crack flanks reveal that contrary to common assumptions in the literature, short cracks in ferrite do not propagate via single slip. Instead, two different slip systems with an identical slip direction, but different slip planes, are activated. In this context, the specific appearance of different crack paths can be explained with the orientation of the respective grains. Furthermore, a model for discontinuous crack propagation especially of rough cracks in ferrite is developed. Finally, a correlation between the crack propagation rate and the plastic deformation of the crack tip is revealed and the possibility of determining the barrier effect of grain and phase boundaries via the measurement of the plastic deformation of the crack tip is investigated.

  1. Influence of delta ferrite on corrosion susceptibility of AISI 304 austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Lawrence O. Osoba

    2016-12-01

    Full Text Available In the current study, the influence of delta (δ ferrite on the corrosion susceptibility of AISI 304 austenitic stainless steel was evaluated in 1Molar concentration of sulphuric acid (H2SO4 and 1Molar concentration of sodium chloride (NaCl. The study was performed at ambient temperature using electrochemical technique—Tafel plots to evaluate the corrosive tendencies of the austenitic stainless steel sample. The as-received (stainless steel specimen and 60% cold-worked (stainless steel specimens were isothermally annealed at 1,100°C for 2 h and 1 h, respectively, and quenched in water. The results obtained show that the heat-treated specimen and the 60% cold-worked plus heat-treated specimen exhibited higher corrosion susceptibility than the as-received specimen, which invariably contained the highest fraction of δ ferrite particles. The finding shows that the presence of δ ferrite, in which chromium (Cr, the main corrosion inhibitor segregates, does not degrade and or reduces the resistance to aqueous corrosion of the austenitic stainless steel material.

  2. The role of ferrite in Type 316H austenitic stainless steels on the susceptibility to creep cavitation

    OpenAIRE

    Warren, A. D.; Griffiths, Ian J; Harniman, Robert L.; Flewitt, Peter E J; Scott, Thomas Bligh

    2015-01-01

    An ex-service Type 316H stainless steel which was subsequently aged at 500°C for ~22×103h was found to contain approximately 2% mixed (δ and α) ferrite distributed in localised regions of the microstructure. Preferred creep cavitation at boundaries was associated with these ferrite regions. Creep cavities associated with the austenite-austenite-ferrite boundary junctions, showed a lenticular morphology while austenite-austenite grain boundary creep cavities had a more spherical morphology. De...

  3. Influence of Ferrite Content on Fatigue Strength of Quenched and Tempered 42CrMoS4 Steel

    OpenAIRE

    Hanno, Mithaq Elias

    2012-01-01

    Specimens of steel 42CrMoS4 were quenched from the austenite (γ) and the ferrite (α) + austenite + cementite phase fields to produce fully martensitic matrices with 0 – 14 % ferrite dispersed in the matrix. After tempering at 300°C or 600°C mechanical and fatigue properties were determined. As expected yield strength, tensile strength and hardness decreased with increased tempering temperature and ferrite content. Quite unexpected, the fatigue properties were mildly affected. A small amount o...

  4. INVESTIGATION ON THE ASSESSMENT OF THE ANEALING EVALUATION OF THE 430E FERRITIC STAINLESS STEEL

    Directory of Open Access Journals (Sweden)

    Alessandra Cunha Ferreira

    2014-10-01

    Full Text Available Ferritic stainless steels may require good stamping properties. In order to achieve the best performance it is necessary to know its texture behavior during hot and cold processing. The present work, investigated the microstructural evolution of niobium-stabilized ferritic stainless annealed steel after 80% thickness reduction. Samples were taken from work hardened condition and isochronous annealed at the temperature range of 400°C to 1000°C. The recrystallized volume fraction has been reported as the softened fraction measured by Vickers microhardness in each temperature. Data analysis was also supported electron backscatter diffraction (EBSD. Results show that the crystallization begins at 700°C for a soaking time of 900s. At about 750°C the steel is fully recrystallized and having grain size of 8,5 µm.

  5. Effects of mechanical force on grain structures of friction stir welded oxide dispersion strengthened ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Han, Wentuo, E-mail: hanwentuo@hotmail.com [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Tsuda, Naoto [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Serizawa, Hisashi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Chen, Dongsheng [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Je, Hwanil [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Fujii, Hidetoshi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Ha, Yoosung [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Morisada, Yoshiaki [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Noto, Hiroyuki [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2014-12-15

    The weldability of oxide dispersion strengthened (ODS) ferritic steels is a critical obstructive in the development and use of these steels. Friction stir welding has been considered to be a promising way to solve this problem. The main purpose of this work was to reveal the effects of mechanical force on grain structures of friction stir welded ODS ferritic steel. The grain appearances and the misorientation angles of grain boundaries in different welded zones were investigated by the electron backscatter diffraction (EBSD). Results showed that the mechanical force imposed by the stir tool can activate and promote the recrystallization characterized by the transformation of boundaries from LABs to HABs, and contribute to the grain refinement. The type of recrystallization in the stir zone can be classified as the continuous dynamic recrystallization (CDRX)

  6. Effects of chromium content and sodium velocity on the compatibility of high-Cr ferritic steels in a sodium environment

    International Nuclear Information System (INIS)

    To obtain fundamental data on the compatibility of high-chromium ferritic steels in sodium, high-purity Fe-0.1C-1Mo-5, 9 or 13Cr ferritic steels were prepared by vacuum melting. Test specimens of these steels which were normalized and tempered and a reference type 316 stainless steel (316 ss) were exposed to two sodium-velocity regions for periods up to 10.8 Ms in a sodium loop system which had a direct resistance main heater and was made of SUS 316. The test temperature, the maximum temperature, of the loop system in this work was 873 K, the oxygen content of sodium was 1 - 2 ppm, and the sodium velocities were about 4.0 and 0.02 m/s. The specimens exposed to the high sodium-velocity region revealed that corrosion loss at a zero downstream position of the three kinds of ferritic steels was smaller than that of the reference 316 ss ; about one fifth for the 5 and 9 %Cr steels and one half for the 13 %Cr steel. The surface analysis showed deposition of Ni that dissolved at upstream for all the ferritic steels, deposition of Cr for the 5 %Cr steel, and selective dissolution of Cr for the 9 and 13 %Cr steels. The ferritic steels without Ni and with less amounts of Cr than the reference 316 ss would result in their smaller corrosion loss than the 316 ss. Transfer of carbon, nitrogen and oxygen was not remarkable, except the carburization of the 5 %Cr steel. The specimens of the three kinds of ferritic steels which were exposed to the low sodium-velocity region revealed much smaller corrosion loss than that in the high velocity region, deposition of both Ni and Cr, and no transfer of carbon, nitrogen and oxygen except for slight carburization of the 13 %Cr steel. (author)

  7. Structure and properties of hot rolled corrosion-resistant ferritic sheet steel

    International Nuclear Information System (INIS)

    Steels K18, Kh18T, Kh25 and Kh25T are investigated with the aim to reveal and optimize the processing parameters determining the structure formation and providing the needed resistance to brittle fracture in ferritic stainless steels. It is stated that the temperature and the deformation degree during final hot rolling passes play a decisive role. A decrease of rolling temperature below 800 deg C and an increase of degree of reduction result in the formation of recrystallized structure in a sheet central zone. This structure ensures sufficient plasticity and toughness, makes further processing easier and enhances mechanical properties of steels

  8. Reduced activation ferritic steel R and D in US/Japan collaborative research

    International Nuclear Information System (INIS)

    Material performance of reduced activation ferritic steels (RAFS) and their response to neutron irradiation, which have been investigated by utilizing fission reactors under the US/Japan collaborative research program (JUPITER), are summarized. Rather high resistance to neutron irradiation and helium was recognized for 9Cr-2W RAFS; irradiation hardening and helium embrittlement of RAFS were evaluated to be much less than for other candidate materials. Alloy design of high-temperature steels and the development of oxide dispersion-strengthened steels have been progressing. (author)

  9. The effect of porosity on the austenite to ferrite transformation in powder metallurgy steels

    International Nuclear Information System (INIS)

    Research highlights: → Presence of porosity in samples reduces overall stability of austenite phase. → Nucleation rate of ferrite increases with increase in porosity in the samples. → Measurements showed reduction in incubation time with increasing porosity. → Avrami exponent, n, found to be independent of temperature and pore fraction. → Avrami constant, b(T), found to be dependent on porosity. - Abstract: The effect of porosity on the kinetics of the austenite to ferrite isothermal transformation in powder metallurgy steels was characterized using high-speed quench dilatometery. The measurements reveal that the presence of porosity in these steels reduces the stability of austenite and hence shortens the incubation time of the transformation. An Avrami-type equation was fitted to the measured data in order to quantify the effect of porosity on the Avrami constants. In addition, samples with varying levels of porosity were interruptedly quenched after holding them at 650 deg. C for 900 s. Quantitative microscopic measurements performed on these samples showed an increase in the number and a decrease in the average diameter of the ferrite grains with increasing porosity. It is hypothesized that pores in powder metallurgy steels increase the rate of nucleation of ferrite from austenite by providing high diffusivity paths for carbon atoms that help accelerate their partitioning during the transformation.

  10. Nature of anisotropy of impact toughness of structural steels with ferrite-pearlite structure

    Science.gov (United States)

    Goritskii, V. M.; Shneyderov, G. R.; Lushkin, M. A.

    2013-10-01

    The anisotropy of the impact toughness of low-alloy steels of various compositions and purities with a ferrite-pearlite structure has been investigated using samples of type 11 according to the Russian Standard GOST 9454-78. It has been established that the anisotropy coefficient of the impact toughness depends on the anisotropy coefficient of the work of crack propagation and is independent of the degree of striation of the ferrite-pearlite structure and the work for nucleation of the ductile crack.

  11. Decomposition Kinetics of Ferrite in Isothermally Aged SAF 2507-Type Duplex Stainless Steel

    Science.gov (United States)

    Berecz, Tibor; Fazakas, Éva; Mészáros, István; Sajó, István

    2015-12-01

    Decomposition of the ferritic phase is studied in isothermally aged SAF 2507 superduplex stainless steel (SDSS) by means of different examination methods. The ferritic phase ( δ) undergoes an eutectoid transformation into secondary austenite ( γ 2) and σ-phase between 650 and 1000 °C. Samples were treated at 900 °C because the incubation time of this transformation is the shortest at this temperature. In order to follow the microstructural changes, x-ray diffraction analysis (XRD), automated electron backscatter diffraction (EBSD), applied magnetic investigation [vibrating sample magnetometer (VSM)], micro-hardness tests, and differential thermal analysis (DTA) were used. The results of XRD and EBSD methods for phase quantification showed nearly the same amounts for all three phases. The results of applied magnetic investigation for the fraction of ferritic phase were also in good agreement with the corresponding results of XRD and EBSD methods. Decomposition of ferrite is similarly well-traceable on EBSD phase maps where the coherent ferritic areas gradually broke into pieces with increasing time of heat treatment. According to the EBSD measurements the σ-phase grains appeared and started to grow after 2 min aging time in the ferritic-austenitic matrix, usually on the boundaries of ferritic and austenitic grains. After 15 min treating time, the microstructure consisted of mainly σ- and austenitic (primary and secondary) phases with negligible amount of ferrite. Chemical composition of the σ-phase was measured by energy-dispersive x-ray spectroscopy (EDS) at different aging times. Activation energies of σ-phase precipitation and α'-phase formation were determined by the Kissinger plot, through DTA measurements; they are 243 and 261 kJ/mol, respectively. Using the results of phase quantifications, the Johnson-Mehl-Avrami equation was fitted.

  12. SPEED DEPENDENCE OF ACOUSTIC VIBRATION PROPAGATION FROM THE FERRITIC GRAIN SIZE IN LOW-CARBON STEEL

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2015-08-01

    Full Text Available Purpose. It is determining the nature of the ferrite grain size influence of low-carbon alloy steel on the speed propagation of acoustic vibrations. Methodology. The material for the research served a steel sheet of thickness 1.4 mm. Steel type H18T1 had a content of chemical elements within grade composition: 0, 12 % C, 17, 5 % Cr, 1 % Mn, 1, 1 % Ni, 0, 85 % Si, 0, 9 % Ti. The specified steel belongs to the semiferritic class of the accepted classification. The structural state of the metal for the study was obtained by cold plastic deformation by rolling at a reduction in the size range of 20-30 % and subsequent recrystallization annealing at 740 – 750 ° C. Different degrees of cold plastic deformation was obtained by pre-selection of the initial strip thickness so that after a desired amount of rolling reduction receives the same final thickness. The microstructure was observed under a light microscope, the ferrite grain size was determined using a quantitative metallographic technique. The using of X-ray structural analysis techniques allowed determining the level of second-order distortion of the crystal latitude of the ferrite. The speed propagation of acoustic vibrations was measured using a special device such as an ISP-12 with a working frequency of pulses 1.024 kHz. As the characteristic of strength used the hardness was evaluated by the Brinell’s method. Findings. With increasing of ferrite grain size the hardness of the steel is reduced. In the case of constant structural state of metal, reducing the size of the ferrite grains is accompanied by a natural increasing of the phase distortion. The dependence of the speed propagation of acoustic vibrations up and down the rolling direction of the ferrite grain size remained unchanged and reports directly proportional correlation. Originality. On the basis of studies to determine the direct impact of the proportional nature of the ferrite grain size on the rate of propagation of sound

  13. Application of thermoelectricity to NDE of thermally aged cast duplex stainless steels and neutron irradiated ferritic steels

    International Nuclear Information System (INIS)

    The thermoelectric power (TEP) of an alloy depends mainly on its temperature, its chemical composition and its atomic arrangement. The TEP measurement technique is used in order to study and follow two degradation phenomena affecting some components of the primary loop of Pressurized Water Reactors (PWR). The first degradation phenomenon is the thermal aging of cast duplex stainless steel components. The de-mixing of the ferritic Fe-Cr-Ni slid solution is responsible for the decreasing of the mechanical characteristics. Laboratory studies have shown the sensitivity of TEP to the de-mixing phenomenon. TEP increases linearly with the ferrite content and with and Arrhenius-type aging parameter depending on time, temperature and activation energy. TEP is also correlated to mechanic characteristics. The second degradation phenomenon is the aging of ferritic steels due to neutron irradiation at about 290 deg C. In this case, the degradation mechanism is the formation of clusters of solute atoms and/or copper rich precipitates that causes the hardening of the material. As a first approach, a study of binary Fe-Cu alloys irradiated by electrons at 288 deg C has revealed the possibility of following the copper depletion of the ferritic matrix. Moreover, the recovery of the mechanical properties of the alloy by annealing can be monitored. Finally, a correlation between Vickers hardness and TEP has been established. (author)

  14. Passivation and Corrosion Behavior of Modified Ferritic-Pearlitic Railway Axle Steels

    Science.gov (United States)

    Moon, A. P.; Sangal, S.; Srivastav, Simant; Gajbhiye, N. S.; Mondal, K.

    2015-01-01

    Electrochemical polarization behavior of two newly developed ferritic-pearlitic railway axle steels (MS3 and MS6) and the standard Indian conventional axle steel has been studied in sodium borate buffer solution of pH 8.4 with and without the presence of NaCl. The polarization behavior of both the new axle steels shows close resemblance, whereas, different polarization behavior has been observed for the conventional axle steel. Electrochemical impedance spectroscopy measurements have clearly reflected significantly improved passivation behavior for the newly developed steels compared to that of the conventional axle steel. NaCl salt fog exposure tests have also shown superior corrosion resistance of the newly developed axle steels as compared to the conventional axle steel. Higher surface roughness on the corroded conventional axle steel has also been observed compared to the smoother surface in case of the new axle steels. Higher corrosion resistance of the new axle steels has been attributed to their finer microstructure and strongly adherent protective rusts.

  15. Influence of smelting processes on precipitation behaviors and mechanical properties of low activation ferrite steels

    International Nuclear Information System (INIS)

    Research highlights: → Creep properties could be improved dramatically by control of smelting process. → VIM + ESR smelting process could improve the W macrosegregation. → W could accelerate the transition of M7C3 to M23C6 in RAFM steel. → The synergetic effect of carbides and tungsten depletion of solid solution lead to the decrease in creep resistance. - Abstract: In this paper, the influence of smelting processes on precipitation behaviors and mechanical properties of CLF-1 (China low activation ferrite) steel was investigated. Mechanical properties of CLF-1 steels melted by vacuum induction melting (VIM, CS25 steel) and vacuum induction melting followed by consumable electrode remelting (VIM + ESR, CS350 steel) had been studied. The results indicated that the steels showed similar values of hardness and tensile strength, however, creep properties of CLF-1 steel were obviously improved by VIM + ESR process. M23C6 and M7C3 Carbides were precipitated in the CS25 steel, and M23C6 carbides were precipitated in CS350 steel after high-temperature tempering at 1013 K for 90 min. Creep properties of CS25 steel were shown to be dramatically deteriorated by the existence of rod M7C3 precipitates, which was due to W macrosegregation in the CS25 steel melted by VIM. M7C3 was replaced by M23C6 after ageing at 823 K for 5000 h.

  16. Development and characterization of advanced 9Cr ferritic/martensitic steels for fission and fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Saroja, S., E-mail: saroja@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India); Dasgupta, A.; Divakar, R.; Raju, S.; Mohandas, E.; Vijayalakshmi, M. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India); Bhanu Sankara Rao, K. [School of Engineering Sciences, University of Hyderabad, Hyderabad (India); Raj, Baldev [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India)

    2011-02-15

    This paper presents the results on the physical metallurgy studies in 9Cr Oxide Dispersion Strengthened (ODS) and Reduced Activation Ferritic/Martensitic (RAFM) steels. Yttria strengthened ODS alloy was synthesized through several stages, like mechanical milling of alloy powders and yttria, canning and consolidation by hot extrusion. During characterization of the ODS alloy, it was observed that yttria particles possessed an affinity for Ti, a small amount of which was also helpful in refining the dispersoid particles containing mixed Y and Ti oxides. The particle size and their distribution in the ferrite matrix, were studied using Analytical and High Resolution Electron Microscopy at various stages. The results showed a distribution of Y{sub 2}O{sub 3} particles predominantly in the size range of 5-20 nm. A Reduced Activation Ferritic/Martensitic steel has also been developed with the replacement of Mo and Nb by W and Ta with strict control on the tramp and trace elements (Mo, Nb, B, Cu, Ni, Al, Co, Ti). The transformation temperatures (A{sub c1}, A{sub c3} and M{sub s}) for this steel have been determined and the transformation behavior of the high temperature austenite phase has been studied. The complete phase domain diagram has been generated which is required for optimization of the processing and fabrication schedules for the steel.

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

    Directory of Open Access Journals (Sweden)

    O. I. Yaskiv

    2014-01-01

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

  18. Grain size distribution after similar and dissimilar gas tungsten arc welding of a ferritic stainless steel

    Directory of Open Access Journals (Sweden)

    Ranjbarnodeh E.

    2015-01-01

    Full Text Available In this study, gas tungsten arc welding of ferritic stainless steel and grain size distribution in heat affected zone of the welded samples were investigated. Both similar and dissimilar arc welding operations were considered where in dissimilar welding joining of stainless steel to mild steel was examined. In the first stage, a three-dimensional model was developed to evaluate temperature field during and after arc welding while the model was performed using finite element software, ANSYS. Then, the effects of welding heat input and dissimilarity of the joint on the weld pool shape and grain growth in HAZ of stainless steel was investigated by means of model predictions and experimental observations. The results show that the similar joint produces wider HAZ and considerably larger grain size structure while in the dissimilar welds, the low carbon part acts as an effective heat sink and prevents the grain growth in the stainless steel side as well reduces the welding maximum temperature.

  19. Effects of nickel and cobalt addition on creep strength and microstructure of the precipitation-strengthened 15Cr ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Shibuya, Masachika; Toda, Yoshiaki; Sawada, Kota; Kushima, Hideaki; Kimura, Kazuhiro [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan)

    2010-07-01

    Creep strength of 15Cr ferritic steel with ferrite matrix was increased by precipitation strengthening of intermetallic compounds. It was higher than those of 9-12Cr ferritic steels with a tempered martensitic microstructure strengthened by carbide and carbonitride. Addition of nickel was confirmed to improve Charpy impact toughness of the 15Cr steels, however, creep strength was slightly reduced by the addition of nickel. Microstructure of the 15Cr steel changes from ferrite single phase to dual phases of ferrite and martensite with the addition of nickel which is an austenite stabilizing element. The 15Cr steels investigated in the previous study, contain 3mass% of cobalt which is also an austenite stabilizing element, therefore, the influence of nickel and cobalt combination on mechanical properties and microstructure of the 15Cr-1Mo-6W-V-Nb steel is investigated in this study. Creep strength, Charpy impact toughness and microstructure of the steel were strongly influenced by the composition of nickel and cobalt. Design guideline of the 15Cr steel is discussed with respect to a role of microstructure and combination of nickel and cobalt addition. (orig.)

  20. Mechanical Properties and Retained Austenite Transformation Mechanism of TRIP-Aided Polygonal Ferrite Matrix Seamless Steel Tube

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ming-ya; ZHU Fu-xian; ZHENG Dong-sheng

    2011-01-01

    Through the comparison of microstructure for polygonal ferrite (PF) matrix transformation induced plasticity (TRIP) seamless steel tube at different positions before and after tensile rupture, the transformation behavior of retained austenite (RA) was studied. The results showed that there were no yield points in tensile process and the splendid elongation and tensile strength were contributed by the uniform ferrite/bainite grains and the transformation of RA. The stability of RA was to some extent in inverse proportion with the ability of transformation induced plas ticity. The coarse retained austenite located in ferrite and ferrite/bainite laths were all transformed into martensite during the tensile process.

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

    Science.gov (United States)

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

    2003-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-12-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2013-01-01

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

  4. Processing of a new high strength high toughness steel with duplex microstructure (Ferrite + Austenite)

    International Nuclear Information System (INIS)

    Highlights: ► This new steel has exceptional combination of high strength and fracture toughness. ► Austempering treatment resulted in a very fine scale bainitic ferrite microstructure. ► As the austempering temperature increases yield strength and toughness decreases. ► Maximum fracture toughness of 105 MPa √m is obtained after austempering at 371 °C. ► A relationship between fracture toughness and the parameter σy(XγCγ)1/2 was observed. - Abstract: In this investigation a new third generation advanced high strength steel (AHSS) has been developed. This steel was synthesized by austempering of a low carbon and low alloy steel with high silicon content. The influence of austempering temperature on the microstructure and the mechanical properties including the fracture toughness of this steel was also examined. Compact tension and cylindrical tensile specimens were prepared from a low carbon low alloy steel and were initially austenitized at 927 °C for 2 h and then austempered in the temperature range between 371 °C and 399 °C to produce different microstructures. The microstructures were characterized by X-ray diffraction, scanning electron microscopy and optical metallography. Test results show that the austempering heat treatment has resulted in a microstructure consisting of very fine scale bainitic ferrite and austenite. A combination of very high tensile strength of 1388 MPa and fracture toughness of 105 MPa √m was obtained after austempering at 371 °C

  5. Effect of Structural Heterogeneity on In Situ Deformation of Dissimilar Weld Between Ferritic and Austenitic Steel

    Science.gov (United States)

    Ghosh, M.; Santosh, R.; Das, S. K.; Das, G.; Mahato, B.; Korody, J.; Kumar, S.; Singh, P. K.

    2015-08-01

    Low-alloy steel and 304LN austenitic stainless steel were welded using two types of buttering material, namely 309L stainless steel and IN 182. Weld metals were 308L stainless steel and IN 182, respectively, for two different joints. Cross-sectional microstructure of welded assemblies was investigated. Microhardness profile was determined perpendicular to fusion boundary. In situ tensile test was performed in scanning electron microscope keeping low-alloy steel-buttering material interface at the center of gage length. Adjacent to fusion boundary, low-alloy steel exhibited carbon-depleted region and coarsening of matrix grains. Between coarse grain and base material structure, low-alloy steel contained fine grain ferrite-pearlite aggregate. Adjacent to fusion boundary, buttering material consisted of Type-I and Type-II boundaries. Within buttering material close to fusion boundary, thin cluster of martensite was formed. Fusion boundary between buttering material-weld metal and weld metal-304LN stainless steel revealed unmixed zone. All joints failed within buttering material during in situ tensile testing. The fracture location was different for various joints with respect to fusion boundary, depending on variation in local microstructure. Highest bond strength with adequate ductility was obtained for the joint produced with 309L stainless steel-buttering material. High strength of this weld might be attributed to better extent of solid solution strengthening by alloying elements, diffused from low-alloy steel to buttering material.

  6. The influence of delta (a) ferrite on the irradiation effects in type-304 stainless steel weldment

    International Nuclear Information System (INIS)

    Differences in the high energy ion induced defects microstructure of BCC a-ferrite and FCC austenite matrix, and the effects of a-ferrite on the Vickers micro-hardness increase after irradiation were investigated for Type 304 stainless steel weldments containing two different a-ferrite contents: ferrite number(FN) 5.5 and 8.5, respectively. Specimens were irradiated to 1.5 dpa by 8 MeV Fe+4 ions using a Tandem Vande-Graft accelerator (flux : 4.3 x 1010 ion/cm2. sec, fluence : 0.83 x 1015 ion/cm2) at room temperature. TRIM 95 results showed that a peak damage appeared at 1.5 μm in depth with 0.7 μm full width at half maximum (FWHM), and these results could have been confirmed by TEM on irradiation induced defects (IID) distribution. Clear differences in the size and number of IID in the form of black dots (size: 5-10 nm) and loops were observed between the austenitic matrix and a-ferrite, where the size of IID was far larger in FCC matrix than BCC a-ferrite. Vickers micro-hardness (Hv) test results showed that a -ferrite has increased about five times higher than austenitic matrix after irradiation. This observation was used to explain the higher Vickers micro-hardness increase due to irradiation in the high FN weldment than the lower FN weldment, i.e., 44% increase for 8.5 FN to 36% increase for 5.5 FN after irradiation

  7. Adsorption of Pb(2+) from aqueous solution using spinel ferrite prepared from steel pickling sludge.

    Science.gov (United States)

    Fang, Binbin; Yan, Yubo; Yang, Yang; Wang, Fenglian; Chu, Zhen; Sun, Xiuyun; Li, Jiansheng; Wang, Lianjun

    2016-01-01

    In this paper, spinel ferrite with high crystallinity and high saturation magnetization was successfully prepared from steel pickling sludge by adding iron source and precipitator in the hydrothermal condition. The obtained spinel ferrite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM), and Zeta potential methods and investigated as an adsorbent for removal of Pb(2+) from aqueous solution. Batch experiments were performed by varying the pH values, contact time, temperature and initial metal concentration. The result of pH impact showed that the adsorption of Pb(2+) was a pH dependent process, and the pH 5.8 ± 0.2 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies revealed that Pb(2+) adsorption onto spinel ferrite followed a pseudo-second order model, and the Langmuir isotherm model provided the perfect fit to the equilibrium experimental data. At different temperatures, the maximum Pb(2+) adsorption capacities calculated from the Langmuir equation were in the range of 126.5-175.4 mg/g, which can be in competition with other adsorbents. The thermodynamic results showed that the spinel ferrite could spontaneously and endothermically adsorb Pb(2+) from aqueous solution. The regeneration studies showed that spinel ferrite could be used five times (removal efficiency (%) >90%) by desorption with HNO3 reagent.

  8. Adsorption of Pb(2+) from aqueous solution using spinel ferrite prepared from steel pickling sludge.

    Science.gov (United States)

    Fang, Binbin; Yan, Yubo; Yang, Yang; Wang, Fenglian; Chu, Zhen; Sun, Xiuyun; Li, Jiansheng; Wang, Lianjun

    2016-01-01

    In this paper, spinel ferrite with high crystallinity and high saturation magnetization was successfully prepared from steel pickling sludge by adding iron source and precipitator in the hydrothermal condition. The obtained spinel ferrite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM), and Zeta potential methods and investigated as an adsorbent for removal of Pb(2+) from aqueous solution. Batch experiments were performed by varying the pH values, contact time, temperature and initial metal concentration. The result of pH impact showed that the adsorption of Pb(2+) was a pH dependent process, and the pH 5.8 ± 0.2 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies revealed that Pb(2+) adsorption onto spinel ferrite followed a pseudo-second order model, and the Langmuir isotherm model provided the perfect fit to the equilibrium experimental data. At different temperatures, the maximum Pb(2+) adsorption capacities calculated from the Langmuir equation were in the range of 126.5-175.4 mg/g, which can be in competition with other adsorbents. The thermodynamic results showed that the spinel ferrite could spontaneously and endothermically adsorb Pb(2+) from aqueous solution. The regeneration studies showed that spinel ferrite could be used five times (removal efficiency (%) >90%) by desorption with HNO3 reagent. PMID:26942534

  9. Ferrite Measurement in Austenitic and Duplex Stainless Steel Castings - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Zhou, G.; Ruprecht, W.

    1999-08-01

    The ability to determine ferrite rapidly, accurately and directly on a finished casting, in the solution annealed condition, can enhance the acceptance, save on manufacturing costs and ultimately improve service performance of duplex stainless steel cast products. If the suitability of a non-destructive ferrite determination methodology can be demonstrated for standard industrial measurement instruments, the production of cast secondary standards for calibration of these instruments is a necessity. With these concepts in mind, a series of experiments were carried out to demonstrate, in a non-destructive manner, the proper methodology for determining ferrite content. The literature was reviewed, with regard to measurement techniques and vagaries, an industrial ferrite measurement round-robin was conducted, the effects of casting surface finish, preparation of the casting surface for accurate measurement and the evaluation of suitable means for the production of cast secondary standards for calibration were systematically investigated. The data obtained from this research program provide recommendations to ensure accurate, repeatable, and reproducible ferrite measurement and qualifies the Feritscope for field use on production castings.

  10. Ferrite Measurement in Austenitic and Duplex Stainless Steel Castings - Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Zhou, G.; Ruprecht, W.

    1999-08-01

    The ability to determine ferrite rapidly, accurately and directly on a finished casting, in the solution annealed condition, can enhance the acceptance, save on manufacturing costs and ultimately improve service performance of duplex stainless steel cast products. If the suitability of a non-destructive ferrite determination methodology can be demonstrated for standard industrial measurement instruments, the production of cast secondary standards for calibration of these instruments is a necessity. With these concepts in mind, a series of experiments were carried out to demonstrate, in a non-destructive manner, the proper methodology for determining ferrite content. The literature was reviewed, with regard to measurement techniques and vagaries, an industrial ferrite measurement round-robin was conducted, the effects of casting surface finish, preparation of the casting surface for accurate measurement and the evaluation of suitable means for the production of cast secondary standards for calibration were systematically investigated. The data obtained from this research program provides recommendations to insure accurate, repeatable and reproducible ferrite measurement and qualifies the Feritscope for field use on production castings.

  11. XRD and TEM study of bainitic ferrite plate thickness in nanostructured, carbide free bainitic steels

    International Nuclear Information System (INIS)

    It is well documented that much of the strength and hardness of nanostructured, carbide free bainitic steels come from the very small thickness of bainitic ferrite plates. In the current work, the Williamson–Hall method has been used to determine the bainitic ferrite plate thickness. The fitting of X-ray peaks to various functions showed good coefficient of determination values for Gaussian function compared to the Cauchy and Pseudo-Voigt functions. The thickness of bainitic ferrite plates was measured by distinguishing the contribution of very small plates on peak broadening from the lattice microstrain and instrumental effects. The results showed that by decreasing the transformation temperature the bainitic ferrite plate thickness decreases. The determined thicknesses were compared with that of measured from transmission electron microscope micrographs. There is a good qualitative and quantitative agreement between the thicknesses measured using both methods. - Highlights: • A Williamson–Hall technique is proposed for bainitic ferrite thickness measurement. • The technique relies on full width at half maximum of XRD peaks. • The measured sizes were compared with that of determined from TEM micrographs. • There is a good qualitative and quantitative agreement between both methods. • Austenite strength and nucleation driving force lead to microstructural refinement

  12. XRD and TEM study of bainitic ferrite plate thickness in nanostructured, carbide free bainitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Yoozbashi, M.N., E-mail: n_yoozbashi@sut.ac.ir [University of Applied Science and Technology, Tabriz (Iran, Islamic Republic of); Yazdani, S., E-mail: yazdani@sut.ac.ir [Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of)

    2015-06-15

    It is well documented that much of the strength and hardness of nanostructured, carbide free bainitic steels come from the very small thickness of bainitic ferrite plates. In the current work, the Williamson–Hall method has been used to determine the bainitic ferrite plate thickness. The fitting of X-ray peaks to various functions showed good coefficient of determination values for Gaussian function compared to the Cauchy and Pseudo-Voigt functions. The thickness of bainitic ferrite plates was measured by distinguishing the contribution of very small plates on peak broadening from the lattice microstrain and instrumental effects. The results showed that by decreasing the transformation temperature the bainitic ferrite plate thickness decreases. The determined thicknesses were compared with that of measured from transmission electron microscope micrographs. There is a good qualitative and quantitative agreement between the thicknesses measured using both methods. - Highlights: • A Williamson–Hall technique is proposed for bainitic ferrite thickness measurement. • The technique relies on full width at half maximum of XRD peaks. • The measured sizes were compared with that of determined from TEM micrographs. • There is a good qualitative and quantitative agreement between both methods. • Austenite strength and nucleation driving force lead to microstructural refinement.

  13. The law of structure formation in sheet stainless steels of the ferrite class

    International Nuclear Information System (INIS)

    The effect of metallurgical redistribution on the structure in the stainless steels of the ferrite class is studied. The regularities of the solid solution state change in dependence on the sheet rolling temperature-deformation conditions are established. It is shown, that the rolling, produced from the stainless steels of the ferrite class, is delivered for hot rolling in the cold-hardened state when there is heavy supersaturation of the solid solution with the carbon and nitrogen atoms. The conclusion is made, that for improving the structure and properties of the cold-rolled sheet it is advisable to subject the rolling to the special recrystallization annealing for separating the carbon and nitrogen atoms in the secondary phase composition

  14. Effect of Autogenous Arc Welding Processes on Tensile and Impact Properties of Ferritic Stainless Steel Joints

    Institute of Scientific and Technical Information of China (English)

    A K Lakshminarayanan; K Shanmugam; V Balasubramanian

    2009-01-01

    The effect of autogeneous arc welding processes on tensile and impact properties of ferritic stainless steel conformed to AISI 409M grade is studied.Rolled plates of 4 mm thickness have been used as the base material for preparing single pass butt welded jointa.Tensile and impact properties,microhardness,microstructure,and fracture surface morphology of continuous current gas tungsten arc welding (CCGTAW),pulsed current gas tungsten arc welding (PCGTAW),and plasma arc welding (PAW) joints are evaluated and the results are compared.It is found that the PAW joints of ferritic stainless steel show superior tensile and impact properties when compared with CCGTAW and PCGTAW joints,and this is mainly due to lower heat input,finer fusion zone grain diameter,and higher fusion zone hardness.

  15. The origin of transformation textures in steel weld metals containing acicular ferrite

    Science.gov (United States)

    Kluken, A. O.; Grong, Ø.; Hjelen, J.

    1991-03-01

    The present investigation is concerned with basic studies of the development of transformation textures in steel weld metals, using the electron backscattering pattern (EBSP) technique. It is shown that the acicular ferrite (AF) plates exhibit an orientation relationship with both the austenite and the prior delta ferrite columnar grains in which they grow. The observed orientation relationship lies within the Bain orientation region and can be described by three texture components, i.e., a component and two complementary components. Each of these texture components is orientated approximately parallel with the original cell/dendrite growth direction. Measurements of the spatial misorientation between neighboring plates confirm that the morphology of AF in low-alloy steel weld metals bears a close resemblance to upper bainite.

  16. Prevision of in-service aging of molded austenitic-ferritic stainless steels components

    International Nuclear Information System (INIS)

    After having recalled the service conditions of the nuclear PWR boilers, the austenitic-ferritic molded stainless steels and their uses in the primary coolant circuit are described. The main consequences of the thermal aging on the rupture mechanisms and the mechanical properties are recalled too. Then are described the laboratory studies carried out in France and abroad which have allowed the development of an extensive knowledge of the aging reaction kinetics and then of embrittlement anticipation formulae. Measures and sampling carried out on down-rated components or even on in service components are used to verify the quality of the in-service aging anticipation. At last are identified the subjects on which it will be important to advance to improve our knowledge of the behaviour of the austenitic-ferritic stainless steels components. (O.M.)

  17. Numerical simulation of hydrogen-assisted crack initiation in austenitic-ferritic duplex steels

    International Nuclear Information System (INIS)

    Duplex stainless steels have been used for a long time in the offshore industry, since they have higher strength than conventional austenitic stainless steels and they exhibit a better ductility as well as an improved corrosion resistance in harsh environments compared to ferritic stainless steels. However, despite these good properties the literature shows some failure cases of duplex stainless steels in which hydrogen plays a crucial role for the cause of the damage. Numerical simulations can give a significant contribution in clarifying the damage mechanisms. Because they help to interpret experimental results as well as help to transfer results from laboratory tests to component tests and vice versa. So far, most numerical simulations of hydrogen-assisted material damage in duplex stainless steels were performed at the macroscopic scale. However, duplex stainless steels consist of approximately equal portions of austenite and δ-ferrite. Both phases have different mechanical properties as well as hydrogen transport properties. Thus, the sensitivity for hydrogen-assisted damage is different in both phases, too. Therefore, the objective of this research was to develop a numerical model of a duplex stainless steel microstructure enabling simulation of hydrogen transport, mechanical stresses and strains as well as crack initiation and propagation in both phases. Additionally, modern X-ray diffraction experiments were used in order to evaluate the influence of hydrogen on the phase specific mechanical properties. For the numerical simulation of the hydrogen transport it was shown, that hydrogen diffusion strongly depends on the alignment of austenite and δ-ferrite in the duplex stainless steel microstructure. Also, it was proven that the hydrogen transport is mainly realized by the ferritic phase and hydrogen is trapped in the austenitic phase. The numerical analysis of phase specific mechanical stresses and strains revealed that if the duplex stainless steel is

  18. Effect of delta-ferrite on the mechanical properties of CF8M stainless steel castings at 4 K

    International Nuclear Information System (INIS)

    A series of five CF8M stainless steel castings, with varying delta-ferrite contents, has been tensile and fracture toughness tested at 4 K. Tensile tests were conducted in the low strain region to establish the initial strain hardening behavior for comparison with two phase deformation theory. It was found that the tensile behavior of the duplex austenite/delta-ferrite structure fits very well with the two phase deformation theory proposed by Ashby. The initial strain hardening rate is determined by the mean-free-path between delta-ferrite particles. Fracture toughness results at 4 K show a decrease in fracture toughness with increasing delta-ferrite content up to approximately 15%; at this point a continuous delta-ferrite crack path is established, and the fracture toughness remains constant with increasing delta-ferrite

  19. DIFFUSIONAL PROPERTIES OF INTERPHASE BOUNDARIES IN TWO-PHASE FERRITIC-AUSTENITIC STEEL

    OpenAIRE

    Światnicki, W.; Świderski, J.; Grabski, M.

    1990-01-01

    Thermal stability of trapped lattice dislocations in ferritic austenitic steel have been studied in order to determine the diffusional properties of internal interfaces. It was found that interphase boundaries with low diffusivity are characterised by the ordered semicoherent structure, formed in Kurdjumov-Sachs or Nishiyama-Wassermann orientation relationship. The fraction of these "special" interfaces varies considerably with the thermomechanical treatment employed as it acts on the process...

  20. Effects of LCF Loadings on the HCF Life of Notched Specimens in Ferritic-Bainitic Steel

    OpenAIRE

    Bidouard, Hadrien; PALIN-LUC, Thierry; Saintier, Nicolas; Dumas, Christian; EL DSOKI, Chalid; KAUFMANN, Heinz; SONSINO, Cetin Morris

    2009-01-01

    Fatigue tests were performed on ferritic bainitic steel notched specimens (Kt = 2.5) under load controlled constant amplitude loading. These tests show that under constant amplitude tension compression loading, periodical overloads application have a detrimental effect on the fatigue crack initiation strength for fully reversed load ratio (R σ = — 1), while they have no influence under pulsating loading (R σ = 0). A finite element analysis shows that in the fully reversed tension (R σ = — ...

  1. Recrystallization of niobium stabilized ferritic stainless steel during hot rolling simulation by torsion tests

    OpenAIRE

    Flávia Vieira Braga; Diana Pérez Escobar; Thompson Junior Ávila Reis; Nilton José Lucinda de Oliveira; Margareth Spangler Andrade

    2016-01-01

    The aim of this study was to investigate the effect of finishing hot rolling temperature in promoting interpass recrystallization on a Nb-stabilized AISI 430 ferritic stainless steel. Torsion tests were performed in order to simulate the Steckel mill rolling process by varying the temperature ranges of the finishing passes. Interrupted torsion test were also performed and interpass recrystallization was evaluated via optical microscopy and electron backscatter diffraction (EBSD). As a result ...

  2. Intergranular segregation of Cr in Ti-stabilized low-Cr ferritic stainless steel

    International Nuclear Information System (INIS)

    The precipitation and segregation phenomenon in a type 409L Ti-stabilized 11 wt.% Cr ferritic stainless steel has been investigated using transmission electron microscopy and a laser-assisted three-dimensional atom probe. In solution-treated and aged specimens, a strong segregation and consequent depletion of Cr was observed, as well as segregation of C and Ti atoms along the grain boundary. The reason for the Cr segregation and the way to avoid such segregation is discussed.

  3. SAW surfacing of low-alloyed steel with super-ferrite additional material

    OpenAIRE

    Klimpel, A; T. Kik; J. Górka; A. Czupryński; P. Sitarz

    2009-01-01

    Purpose: of these researches was to investigate influence of heat input in SAW surfacing of low-alloyed steel with super-ferrite filler material on quality of deposits.Design/methodology/approach: the quality of single and multilayer, stringer beads was assessed by metallographic examinations, stresses measurements and hardness tests.Findings: due to the fact that it was used at automated surfacing stand, the analysis of properties of the deposits was performed for single and multilayer, str...

  4. Ferritic Steel Interconnectors and Their Interactions with Ni Base Anodes in Solid Oxide Fuel Cells (SOFC)

    OpenAIRE

    Froitzheim, J.

    2008-01-01

    In recent years high Cr ferritic steels such as Crofer 22 APU became the most widespread construction materials for solid oxide fuel cell (SOFC) interconnects mainly due to low cost and the ease of fabrication compared to ceramic materials. It was shown that optimum properties with respect to oxide scale growth and adherence could only be obtained by very low, carefully controlled concentrations of minor alloying additions such as Al and Si. This required sophisticated alloy manufacturing met...

  5. Corrosion stability of ferritic stainless steels for solid oxide electrolyser cell interconnects

    DEFF Research Database (Denmark)

    Palcut, Marián; Mikkelsen, Lars; Neufeld, Kai;

    2010-01-01

    Long-term oxidation behaviour of eight ferritic steels with 20–29 wt.% chromium (F 20 T, TUS 220 M, AL 453, Crofer 22 APU, Crofer 22 H, Sanergy HT, E-Brite and AL 29-4C) has been studied. The samples were cut into square coupons, ground and annealed for 140–1000 h at 1173 K in flowing, wet hydrogen...

  6. Dilution and Ferrite Number Prediction in Pulsed Current Cladding of Super-Duplex Stainless Steel Using RSM

    Science.gov (United States)

    Eghlimi, Abbas; Shamanian, Morteza; Raeissi, Keyvan

    2013-12-01

    Super-duplex stainless steels have an excellent combination of mechanical properties and corrosion resistance at relatively low temperatures and can be used as a coating to improve the corrosion and wear resistance of low carbon and low alloy steels. Such coatings can be produced using weld cladding. In this study, pulsed current gas tungsten arc cladding process was utilized to deposit super-duplex stainless steel on high strength low alloy steel substrates. In such claddings, it is essential to understand how the dilution affects the composition and ferrite number of super-duplex stainless steel layer in order to be able to estimate its corrosion resistance and mechanical properties. In the current study, the effect of pulsed current gas tungsten arc cladding process parameters on the dilution and ferrite number of super-duplex stainless steel clad layer was investigated by applying response surface methodology. The validity of the proposed models was investigated by using quadratic regression models and analysis of variance. The results showed an inverse relationship between dilution and ferrite number. They also showed that increasing the heat input decreases the ferrite number. The proposed mathematical models are useful for predicting and controlling the ferrite number within an acceptable range for super-duplex stainless steel cladding.

  7. Current status and recent research achievements in ferritic/martensitic steels

    International Nuclear Information System (INIS)

    When the austenitic stainless steel 316L(N) was selected for ITER, it was well known that it would not be suitable for DEMO and fusion reactors due to its irradiation swelling at high doses. A parallel programme to ITER collaboration already had been put in place, under an IEA fusion materials implementing agreement for the development of a low activation ferritic/martensitic steel, known for their excellent high dose irradiation swelling resistance. After extensive screening tests on different compositions of Fe–Cr alloys, the chromium range was narrowed to 7–9% and the first RAFM was industrially produced in Japan (F82H: Fe–8%Cr–2%W–TaV). All IEA partners tested this steel and contributed to its maturity. In parallel several other RAFM steels were produced in other countries. From those experiences and also for improving neutron efficiency and corrosion resistance, European Union opted for a higher chromium lower tungsten grade, Fe–9%Cr–1%W–TaV steel (Eurofer), and in 1997 ordered the first industrial heats. Other industrial heats have been produced since and characterised in different states, including irradiated up to 80 dpa. China, India, Russia, Korea and US have also produced their grades of RAFM steels, contributing to overall maturity of these steels. This paper reviews the work done on RAFM steels by the fusion materials community over the past 30 years, in particular on the Eurofer steel and its design code qualification for RCC-MRx

  8. Simplified Thermodynamic Model for Pro-Eutectoid Ferrite Formation in Multicomponent Structural Steel

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    By introducing a parameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system, and referring to the thermodynamic model for Fe-C binary system, a simplified thermodynamic model for pro-eutectoid ferrite formation in Fe-ΣXi-C multicomponent structural steels (Xi=Mn, Si, Mo, Cr, Ni or Ti, etc) was suggested. The comparison of the calculated Ae3 temperatures with the measured data of steels 42 shows that the relative standard deviation and root-mean-square (RMS) error between them are only 0.71 % and 8.92 K, respectively. However, the deviations between the same measured data and the values calculated from the superelement model are as high as 1.86 % and 23.83 K, respectively. It can be concluded that the simplified thermodynamic model for pro-eutectoid ferrite formation in multicomponent structural steels is acceptable and the calculated Ae3 temperatures are in good agreement with the experimental data.

  9. Hybrid (plasma + gas tungsten arc) weldability of modified 12% Cr ferritic stainless steel

    International Nuclear Information System (INIS)

    This paper deals with the hybrid (plasma + gas tungsten arc) welding properties of 12 mm thick modified 12% Cr ferritic stainless steel complying with EN 1.4003 and UNS S41003 steels with a carbon content of 0.01% to improve the weldability. The root passes of the butt welds were produced with plasma arc welding (PAW) without filler metal while gas tungsten arc welding (GTAW) was used to accomplish filler passes with 309 and 316 austenitic stainless steel type of consumables, respectively. The joints were subjected to tensile and bend tests as well as Charpy impact toughness testing at -20 oC, 0 oC and 20 oC. Examinations were carried out in terms of metallography, chemical analysis of the weld metal, ferrite content, grain size and hardness analyses. Although 309 consumables provided higher mean weld metal toughness values compared to 316 (90 J vs. 75 J), 316 type of consumables provided better mean HAZ toughness data for the joints (45 J vs. 20 J) at -20 oC. Toughness properties of the welds correspond with those of microstructural features including grain size and ferrite content.

  10. The influence of Cr content on the mechanical properties of ODS ferritic steels

    Science.gov (United States)

    Li, Shaofu; Zhou, Zhangjian; Jang, Jinsung; Wang, Man; Hu, Helong; Sun, Hongying; Zou, Lei; Zhang, Guangming; Zhang, Liwei

    2014-12-01

    The present investigation aimed at researching the mechanical properties of the oxide dispersion strengthened (ODS) ferritic steels with different Cr content, which were fabricated through a consolidation of mechanical alloyed (MA) powders of 0.35 wt.% nano Y2O3 dispersed Fe-12.0Cr-0.5Ti-1.0W (alloy A), Fe-16.0Cr-0.5Ti-1.0W (alloy B), and Fe-18.0Cr-0.5Ti-1.0W (alloy C) alloys (all in wt.%) by hot isostatic pressing (HIP) with 100 MPa pressure at 1150 °C for 3 h. The mechanical properties, including the tensile strength, hardness, and impact fracture toughness were tested by universal testers, while Young's modulus was determined by ultrasonic wave non-destructive tester. It was found that the relationship between Cr content and the strength of ODS ferritic steels was not a proportional relationship. However, too high a Cr content will cause the precipitation of Cr-enriched segregation phase, which is detrimental to the ductility of ODS ferritic steels.

  11. Computer Simulation of Ferrite Transformation during Hot Working of Low Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Yunbo XU; Yongmei YU; Xianghua LIU; Guodong WANG

    2004-01-01

    On the basis of transformation kinetics and thermodynamics, the austenite-ferrite transformation start temperature during deformation was predicted for several grades of low-carbon steels under different processing conditions. Results indicate that Ar3d temperature mostly depended on alloying composition and processing parameters. Ar3d increased as strain rate or strain increased for the same steel grade. In view of enhancement of deformation on transformation,the basic kinetics model was established to simulate deformation induced transformation behavior, using which the influence of the deformation stored energy and effective deformation ledge on the nucleation and growth can be considered. The simulated results are in good agreement with experiment results.

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

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-03-01

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

  13. Microstructure and mechanical properties of an oxide dispersion strengthened ferritic steel by a new fabrication route

    International Nuclear Information System (INIS)

    A reduced activation oxide dispersion strengthened (ODS) ferritic steel with nominal composition of Fe-12Cr-2.5W-0.25Ti-0.2V-0.4Y2O3 (designated 12Cr-ODS) was produced by using EDTA-citrate complex method to synthesize and add Y2O3 particles to an argon atomized steel powder, followed by hot isostatic pressing at 1160 deg. C for 3 h under the pressure of 130 MPa, forging at 1150 deg. C, and heat treatment at 1050 deg. C for 2 h. The microstructure, tensile, and Charpy impact properties of the 12Cr-ODS steel were investigated. Transmission electron microscopy studies indicate that the 12Cr-ODS steel exhibits the characteristic ferritic structure containing few dislocations. Tensile characterization has shown that the 12Cr-ODS steel has superior tensile strength accompanied by good elongation at room temperature and 550 deg. C. The material exhibits very attractive Charpy impact properties with upper shelf energy of 22 J and a ductile-to-brittle transition temperature (DBTT) of about -15 deg. C. The formation of small, equiaxed grains and fine dispersion of oxide particles are the main reasons for the good compromise between tensile strength and impact properties.

  14. Ultimate strength of single shear bolted connections with cold-formed ferritic stainless steel

    Institute of Scientific and Technical Information of China (English)

    Jin-seong LIM; Tae-soo KIM; Seung-hun KIM

    2013-01-01

    This paper is focused on the structural behavior of the single shear bolted connections with thin-walled ferritic stainless steel.The purpose of this study is to investigate the ultimate behaviors,such as ultimate strength and fracture mode of the single shear bolted connections of thin-walled ferritic stainless steel (low cost steel) rather than austenitic stainless steel (high cost steel).Bolt arrangement and end distance parallel to the direction of applied load are considered as main variables of the test specimens for bolted connections.Specimens have a constant dimension of edge distance perpendicular to the loading direction,bolt diameter,pitch,and gauge.A monotonic tensile test for specimens has been carried out and some bolted connections with long end distance showed curling (out of plane deformation) occurrence which led to strength reduction.The ultimate behaviors such as fracture mode,ultimate strength are compared with those predicted by current design codes.Further,conditions of curling occurrence and the strength reduction due to curling are investigated and modified strength equations are suggested considering the curling effect.

  15. Effect of initial microstructures on the properties of Ferrite-Martensite Dual-Phase pipeline steels with Strain-Based design

    Directory of Open Access Journals (Sweden)

    Yueyue Hu

    2012-04-01

    Full Text Available This study aims to investigate the effect of initial microstructures on the properties of ferrite-martensite dual-phase pipeline steels with strain-based design. For this purpose, the as-received acicular ferrite steels were first austenitized at 920 ºC for 15 minutes followed by air cooling and water quenching to produce ferrite-pearlite and ferrite-martensite microstructure, respectively. Subsequently, the steels with ferrite-pearlite, ferrite-martensite and as-received acicular ferrite microstructure were intercritically annealed at 820 ºC for 10 minutes followed by water quenching to produce three different ferrite-martensite dual-phase microstructures. Tensile tests, Vickers hardness and Charpy impact tests were carried out to investigate the mechanical properties. Scanning electron microscope was used to analyze the microstructures and tensile fractographs. The results showed that all the tensile specimens of these three different ferrite-martensite dual-phase steels fractured in ductile mode, however, their microstructures and mechanical properties varied significantly. By contrast, the ferrite-martensite dual-phase steel derived from acicular ferrite initial microstructure had optimal combination of the strength, toughness and deformability, which provided a good candidate for the pipeline steels with strain-based design used in severe geological environments.

  16. Microstructure and properties of pipeline steel with a ferrite/martensite dual-phase microstructure

    International Nuclear Information System (INIS)

    In order to satisfy the transportation of the crude oil and gas in severe environmental conditions, a ferrite/martensite dual-phase pipeline steel has been developed. After a forming process and double submerged arc welding, the microstructure of the base metal, heat affected zone and weld metal was characterized using scanning electron microscopy and transmission electron microscopy. The pipe showed good deformability and an excellent combination of high strength and toughness, which is suitable for a pipeline subjected to the progressive and abrupt ground movement. The base metal having a ferrite/martensite dual-phase microstructure exhibited excellent mechanical properties in terms of uniform elongation of 7.5%, yield ratio of 0.78, strain hardening exponent of 0.145, an impact energy of 286 J at - 10 deg. C and a shear area of 98% at 0 deg. C in the drop weight tear test. The tensile strength and impact energy of the weld metal didn't significantly reduce, because of the intragranularly nucleated acicular ferrites microstructure, leading to high strength and toughness in weld metal. The heat affected zone contained complete quenching zone and incomplete quenching zone, which exhibited excellent low temperature toughness of 239 J at - 10 deg. C. - Research Highlights: →The pipe with ferrite/martensite microstructure shows high deformability. →The base metal of the pipe consists of ferrite and martensite. →Heat affected zone shows excellent low temperature toughness. →Weld metal mainly consists of intragranularly nucleated acicular ferrites. →Weld metal shows excellent low temperature toughness and high strength.

  17. In-service inspection method for low-finned ferritic stainless steel tubes for new heat exchanger

    International Nuclear Information System (INIS)

    Conventional inner eddy current test cannot obtain sufficient evaluation for low finned ferritic stainless steel tube inspection. The authors tried various methods and developed special partial saturation eddy current method. This paper summarizes typical experimental results of fundamental studies and trials, and introduces developed ECT data acquisition and evaluation system. Moisture Separator Heater (MSH) used in ABWR (Advanced Boiling Water Reactor) plant is a new type heat exchanger to increase plant thermal efficiency. There are four single tubesheet heaters in a MSH vessel. Each heater has hundreds of low finned tubes made of ferritic stainless steel. In nuclear power plants, non-magnetic materials (austenitic stainless steel, titanium, aluminum brass, etc.,) are mainly used as heat exchanger tubes such as the tubes of feedwater heater, condenser, evaporator and so on. Conventional ECT (Eddy Current Test) method are easily applied for the inspection of these heat exchanger tubes. In recent years, the authors started using ferritic stainless steel tube for new heat exchangers such as MSH because of its superior heat transfer efficiency. However, high permeability of ferritic stainless steel prevents the inspection of these tubes using conventional ECT method. To inspect MSH tubes periodically is important to confirm and maintain reliability of MSH. They tried applying various inspection methods and have developed special ECT method for low finned ferritic stainless steel tubes

  18. Development oxide dispersion strengthened ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, D.K.; Froes, F.H.; Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-04-01

    Uniaxial tension creep response is reported for an oxide dispersion strengthened (ODS) steel, Fe-13.5Cr-2W-0.5Ti-0.25 Y{sub 2}O{sub 3} (in weight percent) manufactured using the mechanical alloying process. Acceptable creep response is obtained at 900{degrees}C.

  19. Effects of austenite grain size and cooling rate on Widmanstaetten ferrite formation in low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Bodnar, R.L.; Hansen, S.S. (Bethlehem Steel Corp., PA (United States). Hot Rolled Products Div.)

    1994-04-01

    Deformation dilatometry is used to simulate the hot rolling of 0.20 pct C-1.10 pct Mn steels over a product thickness range of 6 to 170 mm. In addition to a base steel, steels with additions of 0.02 pct Ti, 0.06 pct V, or 0.02 pct Nb are included in the study. The transformation behavior of each steel is explored for three different austenite grain sizes, nominally 30, 55, and 100 [mu]m. In general, the volume fraction of Widmanstaetten ferrite increases in all four steels with increasing austenite grain size and cooling rate, with austenite grain size having the more significant effect. The Nb steel has the lowest transformation temperature range and the greatest propensity for Widmanstaetten ferrite formation, while the amount of Widmanstaetten ferrite is minimized in the Ti steel (as a result of intragranular nucleation of polygonal ferrite on coarse TiN particles). The data emphasize the importance of a refined austenite grain size in minimizing the formation of a coarse Widmanstaetten structure. With a sufficiently fine prior austenite grain size (e.g., [le]30 [mu]m), significant amounts of Widmanstaetten structure can be avoided, even in a Nb-alloyed steel.

  20. 46 CFR 54.25-20 - Low temperature operation-ferritic steels with properties enhanced by heat treatment (modifies...

    Science.gov (United States)

    2010-10-01

    ... section VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1... 46 Shipping 2 2010-10-01 2010-10-01 false Low temperature operation-ferritic steels with... VESSELS Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-20 Low temperature...

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

    NARCIS (Netherlands)

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

    2003-01-01

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

  2. Influence of delta ferrite and dendritic carbides on the impact and tensile properties of a martensitic chromium steel

    International Nuclear Information System (INIS)

    Martensitic chrome steels with a high content of chromium incline to form delta ferrite frequently accompanied by massive dendritic carbide precipitations. Both phases mostly influence the mechanical properties of this steel in countercurrent manner. The relatively soft delta ferrite causes an increase of ductility and toughness, whilst the brittle dendritic carbides decreases both. Both phases mostly decrease the strength of the steel. One or the other influence will be dominant in dependence of the quantitative relation of the two phases. This is the cause for very different statements in the literature. The dendritic carbides should be avoided using a cooling rate of more than 103 K/min after the austenitization, because this phase mostly impairs the mechanical properties of the steel. However, the delta ferrite without dendritic carbides can be tolerated mostly. (orig.)

  3. Characterization of ferritic G. M. A. weld deposits in 9% Ni steel for cryogenic applications

    Energy Technology Data Exchange (ETDEWEB)

    Mahin, K.W.

    1980-04-01

    Low temperature containment vessels of 9% Ni are normally fabricated using the shielded metal arc (S.M.A.W.) or the gas metal arc (G.M.A.W.) welding processes. Available filler metals compatible with these processes are highly alloyed austenitics, whose strength levels undermatch those of the base plate. A more efficient weld joint would be a low alloy ferritic deposit. Although acceptable matching ferritic gas tungsten arc weld (G.T.A.W.) wires have been developed, similar progress has not been made in the area of ferritic G.M.A. weld wires. Most of the prior work in this area has focused on correlating composition with mechanical properties, without a corresponding evaluation of resultant microstructure. The study presented focused on establishing correlations between chemistry, microstructure and mechanical properties for four different ferritic G.M.A. weld deposits in 9% Ni steel, with the purpose of developing a better understanding of the factors controlling the 77K (-196/sup 0/C) toughness behavior of these weld metals. Microstructural characterization was carried out using standard optical and scanning electron microscopes, as well as a variety of advanced analytical techniques, including transmission electron microscopy (T.E.M.), scanning T.E.M., Moessbauer spectroscopy and Auger electron spectroscopy.

  4. Effects of radiation on spinodal decomposition of ferrite in duplex stainless steel

    International Nuclear Information System (INIS)

    Duplex stainless steel specimens embrittled by temperature-accelerated thermal aging at 400 °C for 40,000 h were irradiated at 300 °C to 1 dpa with 6.4 MeV Fe3+ ions to study the effects of radiation on spinodal decomposition of ferrite. The microstructural change was examined by atom probe tomography, and the hardness change was measured with an ultra-micro hardness tester. Hardening of the ferrite in thermal aged specimens was reduced by irradiation, whereas the ferrite of the unaged specimen was hardened by it. The spinodal decomposition of the ferrite into Fe-rich α phase and Cr-rich α′ phase, and G-phase precipitation occurred after the thermal aging. Fluctuation of the Cr concentration based on the formation of Cr-rich α′ phase decrease by irradiation. This suggested that irradiation caused the disappearance of spinodal decomposition. The decrease in spinodal decomposition correlated with a decrease in hardness

  5. Influence of delta ferrite content and welding variables on notch toughness of austenitic stainless steel weldments

    International Nuclear Information System (INIS)

    Two series of austenitic stainless steel weld deposits are evaluated to explore the separate contributions of delta ferrite content and welding variables to apparent notch toughness. Charpy-V and Dynamic Tear test determinations are used for weld deposit comparisons. The investigation represents the first part of a two part study of variable weld notch toughness in preirradiation and postirradiation conditions for the temperature range 750F (240C) to 11000F (5930C). Weld Series 1, represented by four 21/2-in. thick AISI Type 308 weld deposits (shielded metal arc) exhibited delta ferrite contents ranging from ferrite number 5.2 to 19.0. Variations in delta ferrite content within this range did not appear to be a major factor in observed toughness trends. Weld Series 2, formed of six 1-in. thick AISI Type 316 weld deposits (submerged arc), indicated that welding parameters and minor differences in flux lot formulations can contribute to variable notch toughness. Initial radiation tests demonstrate that a fluence of 8 to 9 x 1019 n/cm2 greater than 0.1 MeV at 500 to 5500F (260 to 2880C) can produce large reductions in Charpy-V notch ductility for Types 308 and 316 weld deposits

  6. Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

    International Nuclear Information System (INIS)

    We systematically investigate stress–strain behavior of ferrite and bainite with nano-sized vanadium carbides in low carbon steels; the ferrite samples were obtained through austenite/ferrite transformation accompanied with interphase precipitation and the bainite samples were via austenite/bainite transformation with subsequent aging. The stress–strain curves of both samples share several common features, i.e. high yield stress, relatively low work hardening and sufficient tensile elongation. Strengthening contributions from solute atoms, grain boundaries, dislocations and precipitates are calculated based on the structural parameters, and the calculation result is compared with the experimentally-obtained yield stress. The contributions from solute atoms and grain boundaries are simply additive, whereas those from dislocations and precipitates should be treated by taking the square root of the sum of the squares of two values. Nano-sized carbides may act as sites for dislocation multiplication in the early stage of deformation, while they may enhance dislocation annihilation in the later stage of deformation. Such enhanced dynamic recovery might be the reason for a relatively large elongation in both ferrite and bainite samples

  7. Identification of Age, Temperature and Radiation Effect on Ferritic Steel Microstructure Based on Artificial Intelligence

    International Nuclear Information System (INIS)

    In the construction of nuclear installation, it is important to know the material condition used on it. Considering mechanical properties of these materials, there are some material change affected by ageing, temperature and radiation. For some years, austenitic stainless steel are used as a fuel cladding in fast breeder reactor. However this material will not sufficiently competitive from economic point of view for the next year. Experiment result on ferritic steel gave information of stronger structural properties compared to austenitic stainless steel. Modeling and simulation will support further identification of this material changing caused by such effects. Pattern recognition of these changes base on artificial intelligence is expected to support the research and development activities on nuclear structure materials. Material structure pattern of these materials, observed by SEM, are converted using image processing system. Its characteristic is then analyzed with principal component using perception method, which usually used on identifying and learning neural network system based on artificial intelligence. Specific design and input are needed to identify the change of material structure pattern before and after any applied effect. In this paper, simulation of changing identification on three types ferritic steel F17(17 Cr), EM 12 (9 CR-2 MoNbV), and EMI 0 (9 Cr-I Mo) were done. The microstructure data before and after effect are taken from some references. The whole pattern recognition process are done using MATLAB software package. (author)

  8. Stress and adhesion of chromia-rich scales on ferritic stainless steels in relation with spallation

    Directory of Open Access Journals (Sweden)

    A. Galerie

    2004-03-01

    Full Text Available The relation between chromia scale spallation during oxidation or cooling down of ferritic stainless steels is generally discussed in terms of mechanical stresses induced by volume changes or differential thermal expansion. In the present paper, growth and thermal stress measurements in scales grown on different ferritic steel grades have shown that the main stress accumulation occurs during isothermal scale growth and that thermal stresses are of minor importance. However, when spallation occurs, it is always during cooling down. Steel-oxide interface undulation seems to play a major role at this stage, thus relating spallation to the metal mechanical properties, thickness and surface preparation. A major influence on spallation of the minor stabilizing elements of the steels was observed which could not be related to any difference in stress state. Therefore, an original inverted blister test was developed to derive quantitative values of the metal-oxide adhesion energy. These values clearly confirmed that this parameter was influenced by scale thickness and by minor additions, titanium greatly increasing adhesion whereas niobium decreased it.

  9. Report on thermal aging effects on tensile properties of ferritic-martensitic steels.

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Soppet, W.K.; Rink, D.L.; Listwan, J.T.; Natesan, K. (Nuclear Engineering Division)

    2012-05-10

    This report provides an update on the evaluation of thermal-aging induced degradation of tensile properties of advanced ferritic-martensitic steels. The report is the first deliverable (level 3) in FY11 (M3A11AN04030103), under the Work Package A-11AN040301, 'Advanced Alloy Testing' performed by Argonne National Laboratory, as part of Advanced Structural Materials Program for the Advanced Reactor Concepts. This work package supports the advanced structural materials development by providing tensile data on aged alloys and a mechanistic model, validated by experiments, with a predictive capability on long-term performance. The scope of work is to evaluate the effect of thermal aging on the tensile properties of advanced alloys such as ferritic-martensitic steels, mod.9Cr-1Mo, NF616, and advanced austenitic stainless steel, HT-UPS. The aging experiments have been conducted over a temperature of 550-750 C for various time periods to simulate the microstructural changes in the alloys as a function of time at temperature. In addition, a mechanistic model based on thermodynamics and kinetics has been used to address the changes in microstructure of the alloys as a function of time and temperature, which is developed in the companion work package at ANL. The focus of this project is advanced alloy testing and understanding the effects of long-term thermal aging on the tensile properties. Advanced materials examined in this project include ferritic-martensitic steels mod.9Cr-1Mo and NF616, and austenitic steel, HT-UPS. The report summarizes the tensile testing results of thermally-aged mod.9Cr-1Mo, NF616 H1 and NF616 H2 ferritic-martensitic steels. NF616 H1 and NF616 H2 experienced different thermal-mechanical treatments before thermal aging experiments. NF616 H1 was normalized and tempered, and NF616 H2 was normalized and tempered and cold-rolled. By examining these two heats, we evaluated the effects of thermal-mechanical treatments on material microstructures

  10. Effects of Widmanstaetten ferrite on the mechanical properties of a 0. 2 pct C-0. 7 pct Mn steel

    Energy Technology Data Exchange (ETDEWEB)

    Bodnar, R.L.; Hansen, S.S. (Bethlehem Steel Corp., PA (United States). Hot Rolled Products Div.)

    1994-04-01

    Laboratory melted and rolled C-Mn steel plates were austenitized at either 925 C or 1,150 C to produce nominal austenite grain sizes of 60 and 200 [mu]m, respectively. The plates were then cooled at rates in the range of about 2 C/min to 400 C/min to produce mixed polygonal ferrite/Widmanstaetten ferrite/pearlite microstructures. The percentage of Widmanstaetten structure (a Widmanstaetten ferrite/pearlite aggregate) increases with increasing prior austenite grain size and cooling rate. Both yield strength and impact toughness increase with decreasing austenite grain size and increasing cooling rate. This simultaneous improvement in strength and toughness is attributed to overall refinement of both the polygonal ferrite and Widmanstaetten structure. Both yield and tensile strength increase with an increase in the volume fraction of Widmanstaetten ferrite and a reduction in ferrite grain size-ID contrast, the toughness level achieved in these polygonal ferrite/Widmanstaetten ferrite/pearlite microstructures depends largely on the ferrite grain size; the finer the grain size, the better the toughness.

  11. Microstructure evolution and mechanical properties of a hot-rolled directly quenched and partitioned steel containing proeutectoid ferrite

    International Nuclear Information System (INIS)

    A low carbon V microalloyed steel was treated by hot-rolling direct quenching and partitioning (HDQ and P) processes. The microstructures were characterized by polygonal proeutectoid ferrite and lath martensite accompanying with both blocky and film-like retained austenite. This kind of HDQ and P steel possesses a lower yield ratio and similar tensile strength and elongation when compared with the existing HDQ and P steel without ferrite. Partitioning processes with different time were designed to optimize the characteristics of the retained austenite and to control its stability. The microstructure–properties relationship, the stability of the retained austenite, and the transformation-induced plasticity (TRIP) behavior were investigated by comparing the microstructures and mechanical properties of the HDQ and P sheets with those of the TRIP sheets. The results show that the introduction of proeutectoid ferrite can ensure the low yield strengths of the materials and simultaneously intensify the inhomogeneous distributions of carbon and silicon in the untransformed austenite. The particular element distributions result in a considerable amount of large blocky retained austenite locating on the ferrite/martensite boundaries or in some regions surrounded by ferrite. The high tensile strength of the HDQ and P steel can be attributed to the major martensitic structure, the V-bearing precipitates in ferrite and the TRIP effect of the retained austenite. The outstanding combination of strength, yield ratio and ductility, which synthesizes the advantages of dual-phase (DP) steel, TRIP steel and Q and P steel, indicates that the HDQ and P steel has a great potential for practical application

  12. Microstructure evolution and mechanical properties of a hot-rolled directly quenched and partitioned steel containing proeutectoid ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yunbo; Tan, Xiaodong, E-mail: tanxiaodong163@163.com; Yang, Xiaolong; Hu, Zhiping; Peng, Fei; Wu, Di; Wang, Guodong

    2014-06-01

    A low carbon V microalloyed steel was treated by hot-rolling direct quenching and partitioning (HDQ and P) processes. The microstructures were characterized by polygonal proeutectoid ferrite and lath martensite accompanying with both blocky and film-like retained austenite. This kind of HDQ and P steel possesses a lower yield ratio and similar tensile strength and elongation when compared with the existing HDQ and P steel without ferrite. Partitioning processes with different time were designed to optimize the characteristics of the retained austenite and to control its stability. The microstructure–properties relationship, the stability of the retained austenite, and the transformation-induced plasticity (TRIP) behavior were investigated by comparing the microstructures and mechanical properties of the HDQ and P sheets with those of the TRIP sheets. The results show that the introduction of proeutectoid ferrite can ensure the low yield strengths of the materials and simultaneously intensify the inhomogeneous distributions of carbon and silicon in the untransformed austenite. The particular element distributions result in a considerable amount of large blocky retained austenite locating on the ferrite/martensite boundaries or in some regions surrounded by ferrite. The high tensile strength of the HDQ and P steel can be attributed to the major martensitic structure, the V-bearing precipitates in ferrite and the TRIP effect of the retained austenite. The outstanding combination of strength, yield ratio and ductility, which synthesizes the advantages of dual-phase (DP) steel, TRIP steel and Q and P steel, indicates that the HDQ and P steel has a great potential for practical application.

  13. Wrought Cr--W--V bainitic/ferritic steel compositions

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, Ronald L.; Maziasz, Philip J.; Sikka, Vinod Kumar; Santella, Michael L.; Babu, Sudarsanam Suresh; Jawad, Maan H.

    2006-07-11

    A high-strength, high-toughness steel alloy includes, generally, about 2.5% to about 4% chromium, about 1.5% to about 3.5% tungsten, about 0.1% to about 0.5% vanadium, and about 0.05% to 0.25% carbon with the balance iron, wherein the percentages are by total weight of the composition, wherein the alloy is heated to an austenitizing temperature and then cooled to produce an austenite transformation product.

  14. Corrosion of an austenite and ferrite stainless steel weld

    OpenAIRE

    BRANIMIR N. GRGUR; VLADANA N. RAJAKOVIĆ-OGNJANOVIĆ

    2011-01-01

    Dissimilar metal connections are prone to frequent failures. These failures are attributed to the difference in the mechanical properties across the weld, the coefficients of thermal expansion of the two types of steels and the resulting creep at the interface. For the weld analyzed in this research, it was shown that corrosion measurements can be used for a proper evaluation of the quality of weld material and for the prediction of whether or not the material, after the applied welding proce...

  15. Friction Characteristics of Nitrided Layers on AISI 430 Ferritic Stainless Steel Obtained by Various Nitriding Processes

    Directory of Open Access Journals (Sweden)

    Hakan AYDIN

    2013-03-01

    Full Text Available The influence of plasma, gas and salt-bath nitriding techniques on the friction coefficient of AISI 430 ferritic stainless steel was studied in this paper. Samples were plasma nitrided in 80 % N2 + 20 % H2 atmosphere at 450 °C and 520 °C for 8 h at a pressure of 2 mbar, gas nitrided in NH3 and CO2 atmosphere at 570 °C for 13 h and salt-bath nitrided in a cyanide-cyanate salt-bath at 570 °C for 1.5 h. Characterisation of nitrided layers on the ferritic stainless steel was carried out by means of microstructure, microhardness, surface roughness and friction coefficient measurements. Friction characteristics of the nitrided layers on the 430 steel were investigated using a ball-on-disc friction-wear tester with a WC-Co ball as the counter-body under dry sliding conditions. Analysis of wear tracks was carried out by scanning electron microscopy. Maximum hardness and maximum case depth were achieved on the plasma nitrided sample at 520 ºC for 8 h. The plasma and salt-bath nitriding techniques significantly decreased the average surface roughness of the 430 ferritic stainless steel. The friction test results showed that the salt-bath nitrided layer had better friction-reducing ability than the other nitrided layers under dry sliding conditions. Furthermore, the friction characteristic of the plasma nitrided layer at 520 ºC was better than that of the plasma nitrided layer at 450 °C.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3819

  16. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    Science.gov (United States)

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth.

  17. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    Science.gov (United States)

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. PMID:25126753

  18. Effect of the radiation in the reference temperature T0 in ferritic steel

    International Nuclear Information System (INIS)

    The present work studies the effect that produces the irradiation in ferritic steels (AISI 8620) on the reference temperature (T0) that characterizes the tenacity to the fractures (KJC) of these materials obtaining this way a characteristic curve (Master Curve) of this steel. The approach of the 'Master curve' is based on the Astm E-1921. Following this standard the methodology of a sub size settled down in Charpy type test tubes. Due to this type of steels is used mainly in pressure vessels of the reactor in Nuclear Power plants, the fracture tenacity gives the rule at the moment for the verification of structural integrity of the pressure vessel of the reactor. (Author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

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

  20. Nitriding treatment of reduced activation ferritic steel as functional layer for liquid breeder blanket

    International Nuclear Information System (INIS)

    The development of functional layers such as a tritium permeation barrier and an anti-corrosion layer is the essential technology for the development of a molten salt type self cooled fusion blanket. In the present study, the characteristics of a nitriding treatment on a reduced activation ferritic steel, JLF-1 (Fe-9Cr-2W-0.1C) as the functional layer were investigated. The steel surface was nitrided by an ion nitriding treatment or a radical nitriding treatment. The nitridation characteristic of the steel surface was made clear based on the thermodynamic stability. The thermal diffusivity, the hydrogen permeability and the chemical stability in the molten salt Flinak were investigated. The results indicated that the nitriding treatment can improve the compatibility in the Flinak without the decrease of the thermal diffusivity, though there was little improvement as the hydrogen permeation barrier. (author)

  1. Quantitative prediction of deformed austenite and transformed ferrite texture in hot-rolled steel sheet

    Science.gov (United States)

    Tanaka, Y.; Tomida, T.; Mohles, V.

    2015-04-01

    A model to quantitatively predict ferrite (α) textures in hot-rolled steel sheets has been developed. In this model, the crystal plasticity model, called “Grain Interaction model (GIA)”, and the transformation texture model, called “Double K-S relation (DKS)”, are linked together. The deformed austenite (γ) texture is predicted by GIA with taking not only the standard {111} slip system but also non-octahedral slip systems into account. Then the transformed a texture is calculated by DKS, in which a nucleated α prefers to have orientation relationship near the Kurdjumov-Sachs relation with both of two neighboring γ grains. For validation, single pass hot-rolling tests on a C-Si-Mn steel were carried out. The comparison between the predicted and the experimental textures shows that the linked model (GIA & DKS) can lead to a remarkable reproduction of the texture of hot-rolled steel sheets.

  2. Influence of ferrite decomposition mechanisms on the corrosion resistance of an aged duplex stainless steel

    International Nuclear Information System (INIS)

    The effect of long term aging of a duplex stainless steel type X6 CrNiMoCu25-6 on pitting and intergranular corrosion was investigated by various electrochemical methods including cyclic potentiodynamic tests, potentio-kinetic tests and DL-EPR (Double Loop Electrochemical Potentio-kinetic Reactivation) tests. It was established that the spinodal decomposition of ferrite (α' + G) after aging at 400 C during 1000 h leads to localized chromium depletion (wavelength 20 nm) without any detrimental effect on the pitting and intergranular resistance of this steel in synthetic sea water, compared to the annealed steel. However, aging at 500 C for 1000 h generates carbides and intermetallic phases by nucleation and growth producing larger chromium depleted areas, which results in lower pitting and intergranular corrosion resistance in synthetic sea water. (authors)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-01

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

  4. Effect of niobium clustering and precipitation on strength of an NbTi-microalloyed ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kostryzhev, A.G., E-mail: kostryzhev@yahoo.com [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2500 (Australia); Al Shahrani, A. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2500 (Australia); Zhu, C.; Cairney, J.M.; Ringer, S.P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Killmore, C.R. [BlueScope Steel Limited, Five Islands Road, Port Kembla, NSW 2505 (Australia); Pereloma, E.V. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2500 (Australia); UOW Electron Microscopy Centre, University of Wollongong, NSW 2519 (Australia)

    2014-06-01

    The microstructure–property relationship of an NbTi-microalloyed ferritic steel was studied as a function of thermo-mechanical schedule using a Gleeble 3500 simulator, optical and scanning electron microscope, and atom probe tomography. Contributions to the yield stress from grain size, solid solution, work hardening, particle and cluster strengthening were calculated using the established equations and the measured microstructural parameters. With a decrease in the austenite deformation temperature the yield stress decreased, following a decrease in the number density of >20 nm Nb-rich particles and ≈5 nm Nb-C clusters, although the grain refinement contribution increased. To achieve the maximum cluster/precipitation strengthening in ferrite, the austenite deformation should be carried out in the recrystallisation temperature region where there is a limited tendency for strain-induced precipitation. Based on the analysis of cluster strengthening increment, it could be suggested that the mechanism of dislocation–cluster interaction is closer to shearing than looping.

  5. Effect of Coiling Temperature on the Evolution of Texture in Ferritic Rolled Ti-IF Steel

    Institute of Scientific and Technical Information of China (English)

    Zhaodong WANG; Yanhui GUO; Wenying XUE; Xianghua LIU; Guodong WANG

    2007-01-01

    The effect of coiling temperatures on the evolution of texture in Ti-IF steel during ferritic hot rolling, cold rolling and annealing was studied. It was found that texture evolution at high temperature coiling is absolutely different from that at low temperature one. The hot band texture includes a strong α-fiber as well as a weak γ-fiber after ferritic hot rolling and Iow temperature coiling. Both of them intensify after cold rolling and a γ-fiber with peak at {111}<112> is the main texture of annealed samples. However, the main component of the hot band texture after high temperature coiling is γ-fiber. After cold rolling, the intensity of γ texture reduces; α fiber (except {111}<110> component) intensifies and a strong and well-proportioned γ-fiber forms in the annealed samples.

  6. Effect of niobium clustering and precipitation on strength of an NbTi-microalloyed ferritic steel

    International Nuclear Information System (INIS)

    The microstructure–property relationship of an NbTi-microalloyed ferritic steel was studied as a function of thermo-mechanical schedule using a Gleeble 3500 simulator, optical and scanning electron microscope, and atom probe tomography. Contributions to the yield stress from grain size, solid solution, work hardening, particle and cluster strengthening were calculated using the established equations and the measured microstructural parameters. With a decrease in the austenite deformation temperature the yield stress decreased, following a decrease in the number density of >20 nm Nb-rich particles and ≈5 nm Nb-C clusters, although the grain refinement contribution increased. To achieve the maximum cluster/precipitation strengthening in ferrite, the austenite deformation should be carried out in the recrystallisation temperature region where there is a limited tendency for strain-induced precipitation. Based on the analysis of cluster strengthening increment, it could be suggested that the mechanism of dislocation–cluster interaction is closer to shearing than looping

  7. Irradiation-induced precipitation modelling of ferritic steels

    Science.gov (United States)

    Yin, You Fa; Faulkner, Roy G.; Lu, Zheng

    2009-06-01

    In high strength low alloy (HSLA) steels typically used in reactor pressure vessels (RPV), irradiation-induced microstructure changes affect the performance of the components. One such change is precipitation hardening due to the formation of solute clusters and/or precipitates which form as a result of irradiation-enhanced solute diffusion and thermodynamic stability changes. The other is irradiation-enhanced tempering which is a result of carbide coarsening due to irradiation-enhanced carbon diffusion. Both effects have been studied using a recently developed Monte Carlo based precipitation kinetics simulation technique and modelling results are compared with experimental measurements. Good agreements have been achieved.

  8. Irradiation-induced precipitation modelling of ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Y.F. [Department of Materials, Loughborough University, Ashby Road, Loughborough University, Leicestershire LE11 3TU (United Kingdom)], E-mail: y.yin@lboro.ac.uk; Faulkner, Roy G.; Zheng Lu [Department of Materials, Loughborough University, Ashby Road, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

    2009-05-31

    In high strength low alloy (HSLA) steels typically used in reactor pressure vessels (RPV), irradiation-induced microstructure changes affect the performance of the components. One such change is precipitation hardening due to the formation of solute clusters and/or precipitates which form as a result of irradiation-enhanced solute diffusion and thermodynamic stability changes. The other is irradiation-enhanced tempering which is a result of carbide coarsening due to irradiation-enhanced carbon diffusion. Both effects have been studied using a recently developed Monte Carlo based precipitation kinetics simulation technique and modelling results are compared with experimental measurements. Good agreements have been achieved.

  9. Beneficial influence of an intercritically rolled recovered ferritic matrix on the mechanical properties of TRIP-assisted multiphase steels

    OpenAIRE

    Godet, S.; Jacques, Pascal

    2015-01-01

    The present study deals with the microstucture and mechanical properties of intercritically rolled TRIP-assisted multiphase steels. It is shown that the occurrence of the TRIP effect in a recovered ferritic matrix brings about an improved strength-ductility balance with respect to a fully recrystallised ferrite matrix. On the other hand, the intercritical deformation does not influence the austenite transformation rate during straining at room temperature. The improvement of the mechanical pr...

  10. Effect of heat treatment and irradiation temperature on impact behavior of irradiated reduced-activation ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

    Charpy tests were conducted on eight normalized-and-tempered reduced-activation ferritic steels irradiated in two different normalized conditions. Irradiation was conducted in the Fast Flux Test Facility at 393 C to {approx}14 dpa on steels with 2.25, 5, 9, and 12% Cr (0.1% C) with varying amounts of W, V, and Ta. The different normalization treatments involved changing the cooling rate after austenitization. The faster cooling rate produced 100% bainite in the 2.25 Cr steels, compared to duplex structures of bainite and polygonal ferrite for the slower cooling rate. For both cooling rates, martensite formed in the 5 and 9% Cr steels, and martensite with {approx}25% {delta}-ferrite formed in the 12% Cr steel. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT) and a decrease in the upper-shelf energy. The difference in microstructure in the low-chromium steels due to the different heat treatments had little effect on properties. For the high-chromium martensitic steels, only the 5 Cr steel was affected by heat treatment. When the results at 393 C were compared with previous results at 365 C, all but a 5 Cr and a 9 Cr steel showed the expected decrease in the shift in DBTT with increasing temperature.

  11. Modelling of creep damage development in ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sandstroem, R. [Swedish Institute for Metals Research, Stockholm (Sweden)

    1998-12-31

    The physical creep damage, which is observed in fossil-fired power plants, is mainly due to the formation of cavities and their interaction. It has previously been demonstrated that both the nucleation and growth of creep cavities can be described by power functions in strain for low alloy and 12 % CrMoV creep resistant steels. It possible to show that the physical creep damage is proportional to the product of the number of cavities and their area. Hence, the physical creep damage can also be expressed in terms of the creep strain. In the presentation this physical creep damage is connected to the empirical creep damage classes (1-5). A creep strain-time function, which is known to be applicable to low alloy and 12 % CrMoV creep resistant steels, is used to describe tertiary creep. With this creep strain - time model the residual lifetime can be predicted from the observed damage. For a given damage class the remaining life is directly proportional to the service time. An expression for the time to the next inspection is proposed. This expression is a function of fraction of the total allowed damage, which is consumed till the next inspection. (orig.) 10 refs.

  12. Lattice strain measurements using synchrotron diffraction to calibrate a micromechanical modeling in a ferrite-cementite steel

    Energy Technology Data Exchange (ETDEWEB)

    Taupin, V.; Pesci, R. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Berbenni, S., E-mail: stephane.berbenni@univ-lorraine.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Berveiller, S.; Ouahab, R. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Bouaziz, O. [Arcelor Research, Arcelor Mittal, Maizieres-les-Metz 57210 (France)

    2013-01-20

    In situ tensile tests were performed at room temperature on a ferrite-cementite steel specifically designed for this study. The evolution of the average stress in ferrite during loading was analyzed by X-ray diffraction. Lattice strain measurements were performed with synchrotron ring diffraction in both ferrite and cementite. These in situ tests were complemented by macroscopic tensile and reversible tensile-compression tests to study the Bauschinger effect. In order to reproduce stresses in ferrite and cementite particles, a recently developed micromechanical Internal Length Mean Field (ILMF) model based on a generalized self-consistent scheme is applied. In this designed ferrite-cementite steel, the third 'phase' of the model represents finite intermediate 'layers' in ferrite due to large geometrically necessary dislocation (GND) densities around cementite particles. The assumed constant thickness of the layers is calibrated thanks to the obtained experimental data. The ILMF model is validated by realistic estimates of the Bauschinger stress and the large difference between mean stresses in ferrite and in cementite phases. This difference cannot be reproduced by classic two-phase homogenization schemes without intermediate GND layers.

  13. Stress-Strain Rate Relations in Ultra High Carbon Steels Deformed in the Ferrite Range of Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Syn, C K; Lesuer, D R; Sherby, O D; Taleff, E M

    2003-02-20

    The stress-strain rate relations in ultrahigh carbon steels (UHCSs) have been analyzed at high temperatures in the ferrite range where dislocation slip is the principal deformation mechanism. Specifically, the present investigation centers on the factors influencing the strength of UHCS in the ferrite range of 500 to 700 C and in the strain rate range of 10{sup -3} to 10{sup 3} s{sup -1}. These steels contain iron carbide as a second phase either in the form of spheroidite or pearlite and vary in the grain size according to the processing history. The new variables that need to be taken into account are the effect of ferromagnetism and its change with temperature on the creep strength of the ferritic UHCSs. Recent studies have shown that ferromagnetism strongly influences the lattice and dislocation pipe diffusion coefficient and the elastic modulus of iron in the ferrite range of temperature. These variables are shown to influence the creep strength of ferrite-base steels and explain the high activation energies that are observed in many of the ferritic UHCSs.

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

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

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

  15. Relation among rolling parameters, microstructures and mechanical properties in an acicular ferrite pipeline steel

    International Nuclear Information System (INIS)

    The correlation among thermo-mechanical controlled processing (TMCP) parameters, microstructures and mechanical properties of an acicular ferrite (AF) pipeline steel was investigated in this study. The steel was hot rolled by four different kinds of TMCP to obtain different AF microstructures, and the corresponding mechanical properties were analyzed. Electron backscatter diffraction (EBSD) analysis was conducted to determine the effective grain size (EGS) in the steel. It was found that the EGS in the steel reduced obviously with decrease of the finish rolling temperature (FRT), but little changed with the cooling rate (CR) and the simulated coiling temperature (SCT). Additionally, the fraction of low angle grain boundaries (LAGBs) increased with increasing CR in the experimental range. It was shown that yield strength of the steel was enhanced by the increased CR and SCT, and reduced FRT, which were corresponding with the increases of LAGB fraction and precipitated carbonitrides as well as the decrease of EGS, respectively. Charpy impact results showed that the low temperature toughness of the steel with FRT about 40 oC above Ar3 tended to be the best, which was in good accordance with the highest fraction of high angle grain boundaries (HAGBs), but seemed not to be related with the EGS.

  16. Microstructure characterization and tensile properties of 18Cr–4Al-oxide dispersion strengthened ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shaofu; Zhou, Zhangjian, E-mail: zhouzhj@mater.ustb.edu.cn; Li, Ming; Wang, Man; Zhang, Guangming

    2015-11-05

    A microstructural characterization was performed on an 18Cr–4Al oxide dispersion strengthened (ODS) ferritic steel using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the secondary phases in the 18Cr–4Al-ODS ferritic steel can be roughly divided into three categories according to their size-level: (1) micron-sized intermetallic σ and YAl phases; (2) submicron-sized precipitates consisting of TiN and AlN precipitates; (3) nano-sized Al{sub 2}O{sub 3} and Y–Ti–O/Y–Al–O complex oxide particles with diameters in a broad size range from several to dozens of nanometers. In addition, tensile testing results revealed that the 18Cr–4Al-ODS sample exhibited better tensile strength and ductility as compared with another commercial ODS steel with similar composition. - Graphical abstract: TEM BF micrographs of carbon extraction replicas of the as-heat treated 18Cr–4Al-ODS sample. - Highlights: • Various types of secondary phase precipitates were identified. • Two kinds of nano-sized particles (Y–Ti–O/Y–Al–O) were found in matrix. • Nano-sized oxide particles uniformly dispersed in matrix. • Correlation between secondary phases and tensile properties was discussed.

  17. Microstructure examination of Fe–14Cr ODS ferritic steels produced through different processing routes

    Energy Technology Data Exchange (ETDEWEB)

    Oksiuta, Z., E-mail: z.oksiuta@pb.edu.pl [Bialystok University of Technology, Mechanical Department (Poland); Hosemann, P. [University of California Berkeley, Nuclear Engineering, 4169 Etcheverry Hall, Berkeley, CA 94720 (United States); Vogel, S.C. [Los Alamos Neutron Science Center, Los Alamos National Laboratory, PO Box 1663, NM (United States); Baluc, N. [Ecole Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, Villigen PSI 5232 (Switzerland)

    2014-08-01

    Various thermo-mechanical treatments were applied to refine and homogenise grain size and improve mechanical properties of hot-isostatically pressed (HIP) 14%Cr ODS ferritic steel. The grain size was reduced, improving mechanical properties, tensile strength and Charpy impact, however bimodal-like distribution was also observed. As a result, larger, frequently elongated grains with size above 1 μm and refined, equiaxed grains with a diameter ranging from 250 to 500 nm. Neutron diffraction measurements revealed that for HIP followed by hydrostatic extrusion material the strongest fiber texture was observed oriented parallel to the extrusion direction. In comparison with hot rolling and hot pressing methods, this material exhibited promising mechanical properties: the ultimate tensile strength of 1350 MPa, yield strength of 1280 MPa, total elongation of 21.7% and Charpy impact energy of 5.8 J. Inferior Charpy impact energy of ∼3.0 J was measured for HIP and hot rolled material, emphasising that parameters of this manufacturing process still have to be optimised. As an alternative manufacturing route, due to the uniform microstructure and simplicity of the process, hot pressing might be a promising method for production of smaller parts of ODS ferritic steels. Besides, the ductile-to-brittle transition temperature of all thermo-mechanically treated materials, in comparison with as-HIPped ODS steel, was improved by more than 50%, the transition temperature ranging from 50 to 70 °C (323 and 343 K) remains still unsatisfactory.

  18. Microstructure examination of Fe-14Cr ODS ferritic steels produced through different processing routes

    Science.gov (United States)

    Oksiuta, Z.; Hosemann, P.; Vogel, S. C.; Baluc, N.

    2014-08-01

    Various thermo-mechanical treatments were applied to refine and homogenise grain size and improve mechanical properties of hot-isostatically pressed (HIP) 14%Cr ODS ferritic steel. The grain size was reduced, improving mechanical properties, tensile strength and Charpy impact, however bimodal-like distribution was also observed. As a result, larger, frequently elongated grains with size above 1 μm and refined, equiaxed grains with a diameter ranging from 250 to 500 nm. Neutron diffraction measurements revealed that for HIP followed by hydrostatic extrusion material the strongest fiber texture was observed oriented parallel to the extrusion direction. In comparison with hot rolling and hot pressing methods, this material exhibited promising mechanical properties: the ultimate tensile strength of 1350 MPa, yield strength of 1280 MPa, total elongation of 21.7% and Charpy impact energy of 5.8 J. Inferior Charpy impact energy of ∼3.0 J was measured for HIP and hot rolled material, emphasising that parameters of this manufacturing process still have to be optimised. As an alternative manufacturing route, due to the uniform microstructure and simplicity of the process, hot pressing might be a promising method for production of smaller parts of ODS ferritic steels. Besides, the ductile-to-brittle transition temperature of all thermo-mechanically treated materials, in comparison with as-HIPped ODS steel, was improved by more than 50%, the transition temperature ranging from 50 to 70 °C (323 and 343 K) remains still unsatisfactory.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-15

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

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

    Science.gov (United States)

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

    2016-09-01

    International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M23C6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ∼500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods. Preliminary experimental results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. The strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9-20Cr oxide dispersion-strengthened ferritic alloys.

  1. Grain boundary diffusion of Fe in ultrafine-grained nanocluster-strengthened ferritic steel

    International Nuclear Information System (INIS)

    Grain boundary diffusion of Fe in nanocluster-strengthened ferritic steel (Fe-14Cr-3W-0.4Ti-0.25Y2O3 in wt.%) has been investigated. The steel was produced by mechanical alloying followed by hot extrusion. The final grain size was ∼200 nm. The diffusivity of Fe was measured within the temperature range 423-820 K. The grain boundary penetration at lower temperatures revealed a specific time dependence, which indicates a residual interconnected porosity in the ferritic steel. In order to quantify the percolating porosity, conventional radiotracer (59Fe) diffusion measurements were combined with a study of room temperature penetration of liquid 110mAg solution to distinguish between solid-state diffusion along boundaries and penetration along the surface of interconnected cavities. The presence of porosity affected the diffusion process, introducing a hierarchy of internal interfaces. The grain boundary diffusion coefficient and the diffusivity along internal surfaces were determined in the so-called type C-C, C-B and B-B kinetic regimes of interface diffusion in a hierarchical microstructure. Using the residual activity method and a 65Zn tracer, the volume fraction of the percolating porosity was estimated to be 0.6%.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-15

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

  3. Development of oxide dispersion strengthened ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.; Gelles, D.S.

    1996-04-01

    Seven ODS steels, Fe(5-13.5)Cr-2W-0.5Ti-0.25 Y{sub 2}O{sub 3} (in weight percent) were manufactured using the mechanical alloying process. Only the composition Fe-13.5Cr3W-0.5Ti-0.25Y{sub 2}O{sub 3} showed no austenite formation at any temperature using differential thermal analysis and hence was selected as an experimental alloy for the present investigation. Milled powders were consolidated by hot isostatic pressing and hot swaging. Electron microscopy studies indicated high material homogeneity. The hardness of the as-swaged specimen was 65 R{sub c}. Annealing of the as-swaged material at 800, 900, 1000, 1100, and 1200{degrees}C showed a minor decrease in the hardness.

  4. Optimization of Ferrite Number of Solution Annealed Duplex Stainless Steel Cladding Using Integrated Artificial Neural Network: Simulated Annealing

    Directory of Open Access Journals (Sweden)

    V. Rathinam

    2014-05-01

    Full Text Available Cladding is the most economical process used on the surface of low carbon structural steel to improve the corrosion resistance. The corrosion resistant property is based on the amount of ferrite present in the clad layer. Generally, the ferrite content present in the layer is expressed in terms of Ferrite Number (FN. The optimum range of ferrite number provides adequate surface properties like chloride stress corrosion cracking resistance, pitting and crevice corrosion resistance and mechanical properties. For achieving maximum economy and enhanced life, duplex stainless steel (E2209T1-4/1 is deposited on the surface of low carbon structural steel of IS: 2062. The problem faced in the weld cladding towards achieving the required amount of ferrite number is selection of optimum combination of input process parameters. This study concentrates on estimating FN and analysis of input process parameters on FN of heat treated duplex stainless steel cladding. To predict FN, mathematical equations were developed based on four factor five level central composite rotatable design with full replication using regression methods. Then, the developed models were embedded further into integrated ANN-SA to estimate FN. From the results, the integrated ANN-SA is capable of giving maximum FN at optimum process parameters compared to that of experimental, regression and ANN modeling.

  5. PREDICTION OF CARBON CONCENTRATION AND FERRITE VOLUME FRACTION OF HOT-ROLLED STEEL STRIP DURING LAMINAR COOLING

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A phase transformation model was presented for predicting the phase fraction transformed and the carbon concentration in austenite for austenite to ferrite transformation during laminar cooling on run-out table in hot rolling strip mill. In this model, the parameter k in Avrami equation was developed for carbon steels. The wide range of chemical composition, the primary austenite grain size, and the retained strain were taken into account. It can be used to predict the ferrite volume fraction and the carbon concentration in austenite of hot-rolled steel strip during laminar cooling on run-out table. The coiling temperature controlling model was also presented to calculate the temperature of steel strip. The transformation kinetics of austenite to ferrite and the evolution of carbon concentration in austenite at different temperatures during cooling were investigated in the hot rolled Q235B strip for thickness of 9.35, 6.4, and 3.2mm. The ferrite volume fraction along the length of the strip was also calculated. The calculated ferrite volume fraction was compared with the log data from hot strip mill and the calculated results were in agreement with the experimental ones. The present study is a part of the prediction of the mechanical properties of hot-rolled steel strip, and it has already been used on-line and off-line in the hot strip mill.

  6. Experimental study and modelling of the high temperature mechanical behavior of oxide dispersion strengthened ferritic steels

    International Nuclear Information System (INIS)

    The strength of metals, and therefore their maximum operating temperature, can be improved by oxide dispersion strengthening (ODS). Numerous research studies are carried out at the French Atomic Energy Commission (CEA) in order to develop a cladding tube material for Gen IV nuclear power reactors. Oxide dispersion strengthened steels appear to be the most promising candidates for such application, which demands a minimum operating temperature of 650 C. The present dissertation intends to improve the understanding of the mechanical properties of ODS steels, in terms of creep lifetime and mechanical anisotropy. The methodology of this work includes mechanical tests between room temperature and 900 C as well as macroscopic and polycrystalline modelling. These tests are carried out on a Fe-14Cr1W0,26Ti + 0,3 Y2O3 ODS ferritic steel processed at CEA by mechanical alloying and hot extrusion. The as-received material is a bar with a circular section. The mechanical tests reveal the high mechanical strength of this steel at high temperature. A strong influence of the strain rate on the ductility and the mechanical strength is also observed. A macroscopic mechanical model has been developed on the basis of some experimental statements such as the high kinematic contribution to the flow stress. This model has a strong ability to reproduce the mechanical behaviour of the studied material. Two different polycrystalline models have also been developed in order to reproduce the mechanical anisotropy of the material. They are based on its specific grain morphology and crystallographic texture. The discrepancy between the predictions of both models and experimental results reveal the necessity to formulate alternate assumptions on the deformation mechanisms of ODS ferritic steels. (author)

  7. Recrystallization and texture in a ferritic stainless steel: An EBSD study

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, C.W. [Department of Metals and Materials Engineering, University of British Columbia, Vancouver BC V6T 1Z4 (Canada); Robaut, F.; Maniguet, L. [CMTC-INPG, St. Martin d' Heres (France); Mithieux, J.D.; Schmitt, J.H. [CRI R and D Groupe Arcelor, Isbergues (France); Brechet, Y. [LTPCM-INPG, St. Martin d' Heres (France)

    2003-08-01

    The recrystallization behavior of laboratory-processed AISI409 ferritic stainless steel sheet has been studied with a focus on texture inhomogeneity and ''sluggish'' recrystallization kinetics, mainly using EBSD in the scanning electron microscope. Pronounced texture gradients were observed in some grain orientations and correlated to the deformation-induced substructure. The strong pinning of some boundaries has been linked not only to textural effects, but also to the precipitation of fine titanium carbonitrides. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  8. Recrystallization of niobium stabilized ferritic stainless steel during hot rolling simulation by torsion tests

    Directory of Open Access Journals (Sweden)

    Flávia Vieira Braga

    2016-01-01

    Full Text Available The aim of this study was to investigate the effect of finishing hot rolling temperature in promoting interpass recrystallization on a Nb-stabilized AISI 430 ferritic stainless steel. Torsion tests were performed in order to simulate the Steckel mill rolling process by varying the temperature ranges of the finishing passes. Interrupted torsion test were also performed and interpass recrystallization was evaluated via optical microscopy and electron backscatter diffraction (EBSD. As a result of this work, it has been established, within the restrictions of a Steckel mill rolling schedule, which thermomechanical conditions mostly favor SRX.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

  10. Effect of niobium on corrosion resistance to sulfuric acid of 430 ferritic stainless steel

    OpenAIRE

    Neusa Alonso-Falleiros; Stephan Wolynec

    1998-01-01

    The influence of niobium on corrosion resistance to 0.5M H2SO4 of 17% Cr ferritic stainless steels, to which it was added in amounts larger than that necessary to stabilize the interstitial elements, was investigated. Their performance was compared to that of other two Fe-17%Cr alloys, one without additions and another containing 0.93% molybdenum. Through weight and electrochemical measurements and through morphologic examination of corroded surface it was found that the corrosion of these al...

  11. Role of ferrite and phosphorus plus sulphur in the crack sensitivity of autogenously welded type 309 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, Jr., F. J.

    1976-07-01

    A study on autogenous welding of Type 309 thin stainless steel sheet was made after experiencing cracking difficulties on several commercial heats. A relationship exists between the sum of the phosphorus plus sulfur, the ferrite control of the weld metal, and the crack sensitivity of autogenously made welds. A new simple weld test for thin-gage sheet is utilized for studying the susceptibility to cracking. A chemistry modification is suggested to alleviate possible weld cracking when autogenously welding this grade. The principles of crack sensitivity prediction could apply to other austenitic stainless steel types where chemistry limits are such that ferrite is possible.

  12. Two methods for processing an ultrafine ferritic grain size in steels and the thermal stability of the structure

    OpenAIRE

    Pan, L

    2004-01-01

    Abstract In this thesis, methods to process ultrafine ferritic (UFF) structures in steels, i.e. grain sizes below about 3 μm have been investigated. It is shown here, in accordance with the results in the literature, that a steel with a UFF grain size can be obtained by two methods, more or less convenient to mass production: deformation-induced ferrite transformation from fine-grained austenite (the DIF route) and the static recrystallization of various heavily cold-worked initial microst...

  13. The recent development of fabrication of ODS ferritic steels for supercritical water-cooled reactors core application

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Z.; Li, M.; Liao, L.; Liu, X.; He, P.; Xu, Y.; Chen, W.; Ge, C. [Univ. of Science and Technology Beijing, School of Materials Science and Engineering, Beijing (China)

    2010-07-01

    Development of cladding materials which can work at high temperature is crucial to realize highly efficient and high-burnup operation of Generation IV nuclear energy systems. Oxide dispersion strengthened (ODS) ferritic steel is one of the most promising cladding materials for advanced nuclear reactors, such as supercritical water-cooled reactor. ODS ferritic steels with Cr content of 12, 14 and 18% were designed and fabricated in China through the mechanical alloying (MA) route. The process parameters were discussed and optimized. Mechanical properties were measured at room temperature and high temperature. (author)

  14. Microstructures and Toughness of Weld Metal of Ultrafine Grained Ferritic Steel by Laser Welding

    Institute of Scientific and Technical Information of China (English)

    Xudong ZHANG; Wuzhu CHEN; Cheng WANG; Lin ZHAO; Yun PENG; Zhiling TIAN

    2004-01-01

    3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120~480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists inheat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.

  15. Reliability of welded austenitic stainless steel containing base metal delta ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Shalaby, Hamdy M. [Kuwait Institute for Scientific Research (Kuwait)

    2004-07-01

    The paper presents the results of a failure case study carried out on welded 304L stainless steel (SS) pipeline of waste gas header (WGH). The environment inside the WGH was mainly wet steam with hydrocarbons, H{sub 2}S, oxygen, CO{sub 2}, organic acids, and organic chlorides. The outside pipe wall temperature was 91-97 deg C. The failure of the pipe was at the heat-affected zone (HAZ). The study was made on four welded pipeline samples, three of which were in service. The pipe samples were welded using three different techniques that included autogenous gas tungsten arc, shielded metal arc, and flux core arc. The investigation revealed that cracking at HAZ was due to base metal delta ferrite decay accompanied with sigma phase formation due to high heat input during welding. However, the morphology and orientation of the cracks suggested that stress-rupture and stress corrosion cracking had occurred. The presence of base metal delta ferrite made all used welding procedures un-successful. The study concluded that utilization of delta ferrite free austenitic SS should eliminate the problem. (author)

  16. Technical Letter Report on the Cracking of Irradiated Cast Stainless Steels with Low Ferrite Content

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y. [Argonne National Lab. (ANL), Argonne, IL (United States); Alexandreanu, B. [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, K. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2014-11-01

    Crack growth rate and fracture toughness J-R curve tests were performed on CF-3 and CF-8 cast austenite stainless steels (CASS) with 13-14% of ferrite. The tests were conducted at ~320°C in either high-purity water with low dissolved oxygen or in simulated PWR water. The cyclic crack growth rates of CF-8 were higher than that of CF-3, and the differences between the aged and unaged specimens were small. No elevated SCC susceptibility was observed among these samples, and the SCC CGRs of these materials were comparable to those of CASS alloys with >23% ferrite. The fracture toughness values of unirradiated CF-3 were similar between unaged and aged specimens, and neutron irradiation decreased the fracture toughness significantly. The fracture toughness of CF-8 was reduced after thermal aging, and declined further after irradiation. It appears that while lowering ferrite content may help reduce the tendency of thermal aging embrittlement, it is not very effective to mitigate irradiation-induced embrittlement. Under a combined condition of thermal aging and irradiation, neutron irradiation plays a dominant role in causing embrittlement in CASS alloys.

  17. SAW surfacing of low-alloyed steel with super-ferrite additional material

    Directory of Open Access Journals (Sweden)

    A. Klimpel

    2009-10-01

    Full Text Available Purpose: of these researches was to investigate influence of heat input in SAW surfacing of low-alloyed steel with super-ferrite filler material on quality of deposits.Design/methodology/approach: the quality of single and multilayer, stringer beads was assessed by metallographic examinations, stresses measurements and hardness tests.Findings: due to the fact that it was used at automated surfacing stand, the analysis of properties of the deposits was performed for single and multilayer, stringer beads.Research limitations/implications: for complete information about tested deposits it is needed to compare deposits properties with other technologies of super-ferrite deposits surfacing.Practical implications: results of this paper is an optimal range of parameters for surfacing of single and multilayer, stringer beads of super-ferrite layers.Originality/value: the researches (macro- and micro-observations, hardness tests, stresses distribution tests were provided for surfacing of single and multilayer, stringer beads, and the results were compared. The influence of heat input on layers properties and theirs structure was defined.

  18. Technical Letter Report on the Cracking of Irradiated Cast Stainless Steels with Low Ferrite Content

    International Nuclear Information System (INIS)

    Crack growth rate and fracture toughness J-R curve tests were performed on CF-3 and CF-8 cast austenite stainless steels (CASS) with 13-14% of ferrite. The tests were conducted at ~320°C in either high-purity water with low dissolved oxygen or in simulated PWR water. The cyclic crack growth rates of CF-8 were higher than that of CF-3, and the differences between the aged and unaged specimens were small. No elevated SCC susceptibility was observed among these samples, and the SCC CGRs of these materials were comparable to those of CASS alloys with >23% ferrite. The fracture toughness values of unirradiated CF-3 were similar between unaged and aged specimens, and neutron irradiation decreased the fracture toughness significantly. The fracture toughness of CF-8 was reduced after thermal aging, and declined further after irradiation. It appears that while lowering ferrite content may help reduce the tendency of thermal aging embrittlement, it is not very effective to mitigate irradiation-induced embrittlement. Under a combined condition of thermal aging and irradiation, neutron irradiation plays a dominant role in causing embrittlement in CASS alloys.

  19. Fracture behavior of ferrite-free stainless steel welds in liquid helium

    International Nuclear Information System (INIS)

    Most research to date concerning the cryogenic toughness of stainless steel weldments has concentrated on the effects of delta-ferrite content and nitrogen concentration. It has been shown that an increase in either of these leads to reduced cryogenic toughness. This paper reports that a wide variation in fracture toughness occurs in 316L weldments that contain no delta ferrite and only small differences in nitrogen concentration. Therefore, welding parameters and minor compositional variability must also have significant influences. Optical microscopy revealed a strong correlation between cryogenic fracture toughness and fusion-zone grain width, which is controlled by welding parameters and weld-metal composition. An increase in grain size reduces the toughness. Microfissuring, which is a problem in low-ferrite welds, did not have an effect on the measured fracture toughness, but in one cast it severely reduced the tensile ductility. Fatigue crack growth rate tests showed little variation in the fatigue properties of 316L weldments, regardless of the variations in other properties

  20. Type IV Cracking Susceptibility in Weld Joints of Different Grades of Cr-Mo Ferritic Steel

    Science.gov (United States)

    Laha, K.; Chandravathi, K. S.; Parameswaran, P.; Bhanu Sankara Rao, K.

    2009-02-01

    Relative type-IV cracking susceptibility in 2.25Cr-1Mo, 9Cr-1Mo, and 9Cr-1MoVNb ferritic steel weld joint has been assessed. The type-IV cracking was manifested as preferential accumulation of creep deformation and cavitation in the relatively soft intercritical region of heat affected zone of the weld joint. The type-IV cracking susceptibility has been defined as the reduction in creep-rupture strength of weld joint compared to its base metal. The 2.25Cr-1Mo steel exhibited more susceptibility to type-IV cracking at relatively lower temperatures; whereas, at higher temperatures, 9Cr-1MoVNb steel was more susceptible. The relative susceptibility to type-IV cracking in the weld joint of the Cr-Mo steels has been rationalized on the basis of creep-strengthening mechanisms operating in the steels and their venerability to change on intercritical heating during weld thermal cycle, subsequent postweld heat treatment, and creep exposure.

  1. Effects of alloying elements on sticking occurring during hot rolling of ferritic stainless steels

    International Nuclear Information System (INIS)

    In this study, effects of alloying elements on the sticking occurring during hot rolling of five kinds of ferritic STS430J1L stainless steels were investigated by analyzing high-temperature hardness and oxidation behavior of the rolled steels. Hot-rolling simulation tests were conducted by a high-temperature wear tester which could simulate actual hot rolling. The simulation test results revealed that the sticking process proceeded with three stages, i.e., nucleation, growth, and saturation. Since the hardness continuously decreased as the test temperature increased, whereas the formation of Fe-Cr oxides in the rolled steel surface region increased, the sticking of five stainless steels was evaluated by considering both the high-temperature hardness and oxidation effects. The addition of Zr, Cu, or Si had a beneficial effect on the sticking resistance, while the Ni addition did not show any difference in the sticking. Particularly in the case of the Si addition, Si oxides formed first in the initial stage of high-temperature oxidation, worked as initiation sites for Fe-Cr oxides, accelerated the formation of Fe-Cr oxides, and thus raised the sticking resistance by about 10 times in comparison with the steel without Si content

  2. On the corrosion behavior of a ferritic 18 Cr-2 Mo-steel

    International Nuclear Information System (INIS)

    The investigations carried out with 18Cr-2Mo steel were aimed at its behaviour under pitting corrosion, crevice corrosion and stress corrosion cracking conditions. This was done in autoclave laboratory experiments and under experimental heat exchanger conditions in Rhine river water with a chloride content of max. 400 ppm. The test temperatures were 80, 100 and 1300C. Model heat exchangers were fabricated and operated to investigate the influence of filler materials and weld joints between the ferritic 18Cr-2Mo steel and a standard austenitic steel. The possibilities of fabricating tube sheers by applying a weld overaly and using explosive bonding were explored. 18Cr-2Mo steel has been shown to be suited for applications in cooling water which a chloride content of 400 ppm. No stress corrosion cracking occurs under such conditions. Tubes with a wall thickness up to 3 mm have sufficient toughness. Tube sheets can be made of boiler plate protected by an explosive cladding or a weld overlay of 18Cr-2Mo. A combination of Type 321 or 304 L and 18Cr-2Mo is possible. Provided 18Cr-2Mo is sufficiently resistant to the product to be cooled, it is an alternative to austenitic CrNi-(Mo) steels (e.g. AISI 304) when stress corrosion cracking is likely to occur. (orig.)

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

    Science.gov (United States)

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

    2013-01-01

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

  4. European development of ferritic-martensitic steels for fast reactor wrapper applications

    International Nuclear Information System (INIS)

    9-12%Cr ferritic-martensitic stainless steels are under development in Europe for fast reactor sub-assembly wrapper applications. Within this class of alloys, attention is focussed on three key specifications, viz. FV448 and DIN 1.4914 (both 10-12%CrMoVNb steels) and EM10 (an 8-10%Cr-0.15%C steel), which can be optimized to give acceptably low ductile-brittle transition characteristics. The results of studies on these steels, and earlier choices, covering heat treatment and compositional optimization, evolution of wrapper fabrication routes, pre and post-irradiation mechanical property and fracture toughness behaviour, microstructural stability, void swelling and in-reactor creep characteristics are reviewed. The retention of high void swelling to displacement doses in excess of 100 dpa in reactor irradiations reaffirms the selection of 9-12%Cr steels for on-going wrapper development. Moreover, irradiation-induced changes in mechanical properties (e.g. in-reactor creep and impact behaviour), measured to intermediate doses, do not give cause for concern; however, additional data to higher doses and at the lower irradiation temperatures of 3700-4000C are needed in order to fully endorse these alloys for high burnup applications in advanced reactor systems

  5. Oxide dispersion strengthened ferritic steels: a basic research joint program in France

    Science.gov (United States)

    Boutard, J.-L.; Badjeck, V.; Barguet, L.; Barouh, C.; Bhattacharya, A.; Colignon, Y.; Hatzoglou, C.; Loyer-Prost, M.; Rouffié, A. L.; Sallez, N.; Salmon-Legagneur, H.; Schuler, T.

    2014-12-01

    AREVA, CEA, CNRS, EDF and Mécachrome are funding a joint program of basic research on Oxide Dispersion Strengthened Steels (ODISSEE), in support to the development of oxide dispersion strengthened 9-14% Cr ferritic-martensitic steels for the fuel element cladding of future Sodium-cooled fast neutron reactors. The selected objectives and the results obtained so far will be presented concerning (i) physical-chemical characterisation of the nano-clusters as a function of ball-milling process, metallurgical conditions and irradiation, (ii) meso-scale understanding of failure mechanisms under dynamic loading and creep, and, (iii) kinetic modelling of nano-clusters nucleation and α/α‧ unmixing.

  6. Radiation-induced Ostwald ripening in oxide dispersion strengthened ferritic steels irradiated at high ion dose

    International Nuclear Information System (INIS)

    Oxide dispersion strengthened (ODS) ferritic steels are considered promising candidates as cladding tubes for Generation IV nuclear reactors. In such reactors, irradiation damage can reach more than 150 dpa at temperatures ranging from 400 to 650 °C. Thus nanoparticle stability has to be guaranteed in order to ensure that these materials possess excellent creep properties. Using Fe ions, ODS steels were irradiated at 500 °C up to 150 dpa. At this temperature the nano-oxide population evolution under irradiation is similar to that observed after annealing at high temperature. It consists of a slight increase in the particle size and a slight decrease in the density, which can be both explained by an Ostwald ripening mechanism. Conversely, irradiations performed at room temperature using Au ions lead to a complete dissolution of the oxide particles, in agreement with the estimation of ballistic vs. radiation enhanced diffusion effects

  7. Surface modification of ferritic steels using MEVVA and duoplasmatron ion sources.

    Science.gov (United States)

    Kulevoy, Timur V; Chalyhk, Boris B; Fedin, Petr A; Sitnikov, Alexey L; Kozlov, Alexander V; Kuibeda, Rostislav P; Andrianov, Stanislav L; Orlov, Nikolay N; Kravchuk, Konstantin S; Rogozhkin, Sergey V; Useinov, Alexey S; Oks, Efim M; Bogachev, Alexey A; Nikitin, Alexander A; Iskandarov, Nasib A; Golubev, Alexander A

    2016-02-01

    Metal Vapor Vacuum Arc (MEVVA) ion source (IS) is a unique tool for production of high intensity metal ion beam that can be used for material surface modification. From the other hand, the duoplasmatron ion source provides the high intensity gas ion beams. The MEVVA and duoplasmatron IS developed in Institute for Theoretical and Experimental Physics were used for the reactor steel surface modification experiments. Response of ferritic-martensitic steel specimens on titanium and nitrogen ions implantation and consequent vacuum annealing was investigated. Increase in microhardness of near surface region of irradiated specimens was observed. Local chemical analysis shows atom mixing and redistribution in the implanted layer followed with formation of ultrafine precipitates after annealing.

  8. Surface modification of ferritic steels using MEVVA and duoplasmatron ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Kulevoy, Timur V., E-mail: kulevoy@itep.ru; Orlov, Nikolay N.; Rogozhkin, Sergey V.; Bogachev, Alexey A.; Nikitin, Alexander A.; Iskandarov, Nasib A.; Golubev, Alexander A. [State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics of National Research Centre “Kurchatov Institute,” Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Chalyhk, Boris B.; Fedin, Petr A.; Sitnikov, Alexey L.; Kozlov, Alexander V.; Kuibeda, Rostislav P.; Andrianov, Stanislav L. [State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics of National Research Centre “Kurchatov Institute,” Moscow (Russian Federation); Kravchuk, Konstantin S.; Useinov, Alexey S. [Technological Institute for Superhard and Novel Carbon Materials, Moscow (Russian Federation); Oks, Efim M. [Institute of High Current Electronics SB RAS, Tomsk (Russian Federation); Tomsk State University of Control System and Radioelectronics, Tomsk (Russian Federation)

    2016-02-15

    Metal Vapor Vacuum Arc (MEVVA) ion source (IS) is a unique tool for production of high intensity metal ion beam that can be used for material surface modification. From the other hand, the duoplasmatron ion source provides the high intensity gas ion beams. The MEVVA and duoplasmatron IS developed in Institute for Theoretical and Experimental Physics were used for the reactor steel surface modification experiments. Response of ferritic-martensitic steel specimens on titanium and nitrogen ions implantation and consequent vacuum annealing was investigated. Increase in microhardness of near surface region of irradiated specimens was observed. Local chemical analysis shows atom mixing and redistribution in the implanted layer followed with formation of ultrafine precipitates after annealing.

  9. Microstructural characterization and formation mechanism of abnormal segregation band of hot rolled ferrite/pearlite steel

    International Nuclear Information System (INIS)

    In order to further reveal the microstructural characterization and formation mechanism of abnormal segregation band of hot rolled ferrite/pearlite steel, the microstructure of this type steel was intensively studied with Scanning Auger Microprobe (SAM), etc. The results show that severe C–Mn segregation exists in the abnormal segregation band region at the center of hot rolled ferrite/pearlite steel, which results from the Mn segregation during solidification process of the continuous casting slab. The C–Mn segregation causes relative displacement of pearlite transformation curve and bainite transformation curve of C curve in the corresponding region, leading to bay-like shaped C curve. The bay-like shaped C curve creates conditions for the transformation from supercooling austenite to bainite at relatively lower cooling rate in this region. The Fe–Mn–C Atomic Segregation Zone (FASZ) caused by C–Mn segregation can powerfully retard the atomic motion, and increase the lattice reconstruction resistance of austenite transformation. These two factors provide thermodynamic and kinetic conditions for the bainite transformation, and result in the emergence of granular bainitic abnormal segregation band at the center of steel plate, which leads to lower plasticity and toughness of this region, and induces the layered fracture. - Highlights: • Scanning Auger Microprobe (SAM) is applied in the fracture analysis. • The abnormal segregation band region appears obvious C–Mn segregation. • The C–Mn segregation leads to bay-like shaped C curve. • The C–Mn segregation leads to Fe–Mn–C Atomic Segregation Zone

  10. The role of interstitial nitrogen in the precipitation hardening reactions in high-chromium ferritic steels

    International Nuclear Information System (INIS)

    The effects of exposure to temperatures in the range 475 - 800 C on the hardness and associated microstructure of high chromium ferritic steels has been investigated. Low-carbon 26Cr-1Mo steels containing 0,02 - 0,04% nitrogen were found to constitute an age hardening system when quenched from a temperature of nitrogen solubility and exposed at temperatures in the range 600 - 700 C. TEM observations on thin foils revealed that hardening was associated with the formation of a high density of Cr-N zones. Ageing at 475 C and 550 C produced hardening due to the formation of chromium-rich ferrite phases α' as result of the miscibility gap in the Fe-Cr phase diagram. However the presence of interstitial nitrogen in solution in the steel considerably reduced the rate of hardening, especially at 475 C. This type of decomposition occurs by a mechanism of nucleation and growth, forming zones similar to those formed during an ageing at 600 C. When depleted of interstitial nitrogen, the specimens aged at 475 C underwent spinodal decomposition. Thus nitrogen in solid solution was found to have a significant effect on the 475 C hardening reaction. Precision X-ray diffraction measurements revealed the presence of secondary diffraction peaks associated with the Bragg peaks, which confirmed the formation of Cr-rich phases during ageing at 475 C. The calculated associated lattice parameter measurements allowed estimates of the compositions of the decomposition phases to be made. These were calculated to be about 6-18% Cr in the Fe-rich and 60-80% Cr in the Cr-rich phases of the 26Cr-1Mo steel

  11. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Minsu; Cho, Wontae; Park, Jihye; Jung, Jae-Gil; Lee, Young-Kook, E-mail: yklee@yonsei.ac.kr

    2014-08-15

    The variation of the C concentration in proeutectoid ferrite (α{sub PF}) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (T{sub m}) of α{sub PF} to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of α{sub PF}. The C concentration in α{sub PF} at T{sub m} in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of α{sub PF} with isothermal holding time at 775 °C in S20C steel revealed C enrichment in α{sub PF} at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in α{sub PF} during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring α{sub PF} as well as pearlitic ferrite. The supersaturated C concentration in α{sub PF} is reduced during the long-range diffusive transformation of α{sub PF} to γ. However, some of the excess C atoms still remain in α{sub PF} until α{sub PF} starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ.

  12. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    International Nuclear Information System (INIS)

    The variation of the C concentration in proeutectoid ferrite (αPF) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (Tm) of αPF to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of αPF. The C concentration in αPF at Tm in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of αPF with isothermal holding time at 775 °C in S20C steel revealed C enrichment in αPF at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in αPF during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring αPF as well as pearlitic ferrite. The supersaturated C concentration in αPF is reduced during the long-range diffusive transformation of αPF to γ. However, some of the excess C atoms still remain in αPF until αPF starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ

  13. Microstructural characterization and formation mechanism of abnormal segregation band of hot rolled ferrite/pearlite steel

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Rui [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Engineering Research Center of Large Size Alloy Structural Steel Bars of Shandong Province, Jinan 250061 (China); School of Materials Science and Engineering, Shandong University of Technology, Zibo 255049 (China); Li, Shengli, E-mail: lishengli@sdu.edu.cn [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Engineering Research Center of Large Size Alloy Structural Steel Bars of Shandong Province, Jinan 250061 (China); Zhu, Xinde [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Ao, Qing [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Engineering Research Center of Large Size Alloy Structural Steel Bars of Shandong Province, Jinan 250061 (China)

    2015-10-15

    In order to further reveal the microstructural characterization and formation mechanism of abnormal segregation band of hot rolled ferrite/pearlite steel, the microstructure of this type steel was intensively studied with Scanning Auger Microprobe (SAM), etc. The results show that severe C–Mn segregation exists in the abnormal segregation band region at the center of hot rolled ferrite/pearlite steel, which results from the Mn segregation during solidification process of the continuous casting slab. The C–Mn segregation causes relative displacement of pearlite transformation curve and bainite transformation curve of C curve in the corresponding region, leading to bay-like shaped C curve. The bay-like shaped C curve creates conditions for the transformation from supercooling austenite to bainite at relatively lower cooling rate in this region. The Fe–Mn–C Atomic Segregation Zone (FASZ) caused by C–Mn segregation can powerfully retard the atomic motion, and increase the lattice reconstruction resistance of austenite transformation. These two factors provide thermodynamic and kinetic conditions for the bainite transformation, and result in the emergence of granular bainitic abnormal segregation band at the center of steel plate, which leads to lower plasticity and toughness of this region, and induces the layered fracture. - Highlights: • Scanning Auger Microprobe (SAM) is applied in the fracture analysis. • The abnormal segregation band region appears obvious C–Mn segregation. • The C–Mn segregation leads to bay-like shaped C curve. • The C–Mn segregation leads to Fe–Mn–C Atomic Segregation Zone.

  14. Further application of the cleavage fracture stress model for estimating the T0 of highly embrittled ferritic steels

    International Nuclear Information System (INIS)

    The semi-empirical cleavage fracture stress model (CFS), based on the microscopic cleavage fracture stress, sf, for estimating the ASTM E1921 reference temperature (T0) of ferritic steels from instrumented impact testing of unprecracked Charpy V-notch specimens is further confirmed by test results for additional steels, including steels highly embrittled by thermal aging or irradiation. In addition to the ferrite-pearlite, bainitic or tempered martensitic steels (which was examined earlier), acicular or polygonal ferrite, precipitation-strengthened or additional simulated heat affected zone steels are also evaluated. The upper limit for the applicability of the present CFS model seems to be T41J ∝160 to 170 C or T0 or TQcfs (T0 estimate from the present CFS model) ∝100 to 120 C. This is not a clear-cut boundary, but indicative of an area of caution where generation and evaluation of further data are required. However, the present work demonstrates the applicability of the present CFS model even to substantially embrittled steels. The earlier doubts expressed about TQcfs becoming unduly non-conservative for highly embrittled steels has not been fully substantiated and partly arises from the necessity of modifications in the T0 evaluation itself at high degrees of embrittlement suggested in the literature.

  15. Further application of the cleavage fracture stress model for estimating the T{sub 0} of highly embrittled ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sreenivasan, P.R.

    2016-02-15

    The semi-empirical cleavage fracture stress model (CFS), based on the microscopic cleavage fracture stress, s{sub f}, for estimating the ASTM E1921 reference temperature (T{sub 0}) of ferritic steels from instrumented impact testing of unprecracked Charpy V-notch specimens is further confirmed by test results for additional steels, including steels highly embrittled by thermal aging or irradiation. In addition to the ferrite-pearlite, bainitic or tempered martensitic steels (which was examined earlier), acicular or polygonal ferrite, precipitation-strengthened or additional simulated heat affected zone steels are also evaluated. The upper limit for the applicability of the present CFS model seems to be T{sub 41J} ∝160 to 170 C or T{sub 0} or T{sub Qcfs} (T{sub 0} estimate from the present CFS model) ∝100 to 120 C. This is not a clear-cut boundary, but indicative of an area of caution where generation and evaluation of further data are required. However, the present work demonstrates the applicability of the present CFS model even to substantially embrittled steels. The earlier doubts expressed about T{sub Qcfs} becoming unduly non-conservative for highly embrittled steels has not been fully substantiated and partly arises from the necessity of modifications in the T{sub 0} evaluation itself at high degrees of embrittlement suggested in the literature.

  16. Standard test method for determination of reference temperature, to, for ferritic steels in the transition range

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This test method covers the determination of a reference temperature, To, which characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at elastic, or elastic-plastic KJc instabilities, or both. The specific types of ferritic steels (3.2.1) covered are those with yield strengths ranging from 275 to 825 MPa (40 to 120 ksi) and weld metals, after stress-relief annealing, that have 10 % or less strength mismatch relative to that of the base metal. 1.2 The specimens covered are fatigue precracked single-edge notched bend bars, SE(B), and standard or disk-shaped compact tension specimens, C(T) or DC(T). A range of specimen sizes with proportional dimensions is recommended. The dimension on which the proportionality is based is specimen thickness. 1.3 Median KJc values tend to vary with the specimen type at a given test temperature, presumably due to constraint differences among the allowable test specimens in 1.2. The degree of KJc variability among specimen types i...

  17. Investigation of microstructure and thermal stability of pulsed plasma processed chromium ferritic-martensitic steels

    Science.gov (United States)

    Emelyanova, O.; Dzhumaev, P.; Yakushin, V.; Polsky, V.

    2016-04-01

    This paper presents results of the microstructural evolution and thermal stability of the promising Russian ferritic-martensitic steels (EP 823, EP 900, EK 181 and ChS 139) for the nuclear and fusion application after surface modification by high temperature pulsed plasma flows (HTPPF) treatment. Investigations of microstructure, topography and elemental content changes associated with irradiation by nitrogen plasma with energy density 19-28 J/ cm2 and pulse duration 20 μs were carried out. Changes in microstructure and elemental content occurring in the modified surface layer were characterized by means of scanning electron microscopy (SEM) and X-ray microanalysis (EDS and WDS). It was shown that independently of initial microstructure and phase composition, HTPPF treatment of ferritic- martensitic steels leads to formation of ultrafine homogeneous structure in the near surface layers with typical grain size ∼100 nm. Results of microstructure investigations after annealing during 1 hour demonstrates significant thermal stability of nanostructure formed by HTPPF treatment.

  18. Interaction of carbon-vacancy complex with minor alloying elements of ferritic steels

    Science.gov (United States)

    Bakaev, A.; Terentyev, D.; He, X.; Zhurkin, E. E.; Van Neck, D.

    2014-08-01

    Interstitial carbon, dissolved in bcc matrix of ferritic steels, plays an important role in the evolution of radiation-induced microstructure since it exhibits strong interaction with vacancies. Frequent formation and break-up of carbon-vacancy pairs, occurring in the course of irradiation, affect both kinetics of the accumulation of point defect clusters and carbon spatial distribution. The interaction of typical alloying elements (Mn, Ni, Cu, Si, Cr and P) in ferritic steels used as structural materials in nuclear reactors with a carbon-vacancy complex is analyzed using ab initio techniques. It is found that all the considered solutes form stable triple clusters resulting in the increase of the total binding energy by 0.2-0.3 eV. As a result of the formation of energetically favourable solute-carbon-vacancy triplets, the dissociation energy for vacancy/carbon emission is also increased by ∼0.2-0.3 eV, suggesting that the solutes enhance thermal stability of carbon-vacancy complex. Association of carbon-vacancy pairs with multiple solute clusters is found to be favorable for Ni, Cu and P. The energetic stability of solute(s)-carbon-vacancy complexes was rationalized on the basis of pairwise interaction data and by analyzing the variation of local magnetic moments on atoms constituting the clusters.

  19. Behaviour of ferritic stainless steels subjected to dry biogas atmospheres at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Promdirek, P. [SIMaP, Grenoble INP/CNRS/UJF, BP 75, 38402 Saint Martin d' Heres cedex (France); Materials and Production Technology Engineering, King Mongkut' s University of Technology North Bangkok, 1518 Pibulsongkram road, Bangsue, Bangkok, 10800 (Thailand); Department of Metallurgical Engineering, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok, 10330 (Thailand); Lothongkhum, G. [Department of Metallurgical Engineering, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok, 10330 (Thailand); Chandra-ambhorn, S. [Materials and Production Technology Engineering, King Mongkut' s University of Technology North Bangkok, 1518 Pibulsongkram road, Bangsue, Bangkok, 10800 (Thailand); Wouters, Y.; Galerie, A. [SIMaP, Grenoble INP/CNRS/UJF, BP 75, 38402 Saint Martin d' Heres cedex (France)

    2011-07-15

    The objective of this study is to understand the high temperature corrosion behaviour of the ferritic stainless steel type AISI 441 (18CrTiNb), a candidate for SOFC interconnectors, under dry synthetic fermentation biogas (CH{sub 4} + CO{sub 2} mixtures), possibly used at the anode side of the cell. Thermodynamic analysis showed that, in such mixtures, the partial pressure of oxygen lies in the range of 10{sup -23} to 10{sup -20} bar for temperature between 700 and 900 C and that the formation of solid carbon may take place in several conditions. XRD results confirmed the formation of Cr{sub 2}O{sub 3} and Mn-Cr spinel, with a mixture of internal carbides. In this temperature range, kinetic experiments showed linear mass change. Comparing with the linear rate constants of 441 oxidised in pure CO{sub 2}, corrosion in biogas was larger and increased with increasing the methane content in the biogas. The surface morphology of the corroded specimens showed a dense oxide scale at temperatures less than 800 C, serving as an efficient barrier to carbon penetration. However, when the temperature reaches 900 C, cracks and pores appear in the oxide scale, carbon can precipitate and diffuse easier than at 800 C and may lead to internal carbide formation. In such biogas atmospheres, 800 C seems the maximum operating temperature of devices containing this ferritic stainless steel. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Strength and infrared assessment of spot-welded sheets on ferrite steel

    International Nuclear Information System (INIS)

    Highlights: • The spot welding of the ferrite steel was analyzed. • The mechanical properties were described in terms of peak load. • The fusion zone size is the most important controlling factor of spot weld peak load. • The failure mechanism was studied with the aid of thermography. - Abstract: This paper addresses the mechanical properties of ferrite steel resistance spot welds during quasi-static tensile test. The mechanical properties are described in terms of peak load. It was shown that the fusion zone size is the most important. The fusion zone size can control the solidification of the grain which controlling factor of spot weld peak load. The dendritic grain and equiaxial axial grains occurred in the microstructures of the welded specimens joined at various welding currents and electrode forces. The failure mechanism of resistance spot welds during tensile test was studied with the aid of thermography. The thermography gives visible data of temperature changes on the surface of specimen. In light of the failure mechanism, the simple model is proposed to ensure pull out failure mode

  1. Interaction of carbon–vacancy complex with minor alloying elements of ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Bakaev, A., E-mail: abakaev@sckcen.be [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol B2400 (Belgium); Center for Molecular Modeling, Department of Physics and Astronomy, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium); Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya Str., 195251 St. Petersburg (Russian Federation); Terentyev, D. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol B2400 (Belgium); He, X. [China Institute of Atomic Energy, P.O. Box 275-51, 102413 Beijing (China); Zhurkin, E.E. [Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya Str., 195251 St. Petersburg (Russian Federation); Van Neck, D. [Center for Molecular Modeling, Department of Physics and Astronomy, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium)

    2014-08-01

    Interstitial carbon, dissolved in bcc matrix of ferritic steels, plays an important role in the evolution of radiation-induced microstructure since it exhibits strong interaction with vacancies. Frequent formation and break-up of carbon–vacancy pairs, occurring in the course of irradiation, affect both kinetics of the accumulation of point defect clusters and carbon spatial distribution. The interaction of typical alloying elements (Mn, Ni, Cu, Si, Cr and P) in ferritic steels used as structural materials in nuclear reactors with a carbon–vacancy complex is analyzed using ab initio techniques. It is found that all the considered solutes form stable triple clusters resulting in the increase of the total binding energy by 0.2–0.3 eV. As a result of the formation of energetically favourable solute–carbon–vacancy triplets, the dissociation energy for vacancy/carbon emission is also increased by ∼0.2–0.3 eV, suggesting that the solutes enhance thermal stability of carbon–vacancy complex. Association of carbon–vacancy pairs with multiple solute clusters is found to be favorable for Ni, Cu and P. The energetic stability of solute(s)–carbon–vacancy complexes was rationalized on the basis of pairwise interaction data and by analyzing the variation of local magnetic moments on atoms constituting the clusters.

  2. Radiological assessment of the limits and potential of reduced activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, Hiroyasu, E-mail: tanigawa.hiroyasu@jaea.go.jp; Someya, Yoji; Sakasegawa, Hideo; Hirose, Takanori; Ochiai, Kentaro

    2014-10-15

    Highlights: • Ni is the major contamination element that should be removed to reduce the activation levels. • The amount of 14C transmuted from N must be reduced to achieve the shallow land burial limit. • About 100 ppm N will remain in the EAF melted steel, and Ni contamination occurs during the melting process. • Using Al for deoxidation of the RAFM steel has no significant impact on the activation levels. • The impact of the minor elements such as Ag is negligible compared to that of Ni and N. - Abstract: Reduced activation ferritic/martensitic (RAFM) steels have been developed as the structural material for the fusion demonstration reactor, DEMO. These steels contain elements that produce radioactive isotopes and decay to low levels in timeframe required by the waste management scenario. Developments within the past quarter-century suggest a practical limit to the removal of undesired impurities such as Co, Cu, Ni, Mo and Nb. The concentrations of elements essential for the mechanical properties of RAFM steels, such as Al and N, required a compromise between the waste disposal scenario and performance demand. The limits and potential of RAFM steel pertaining to reducing the activation levels after service are discussed based on the actual achievements of F82H, Japanese RAFM steel, and numerical analyses of the activity. It was found that in order to achieve the shallow land burial limits 100 years after a reactor shutdown, Ni is the most significant impurity that must be removed (Mo in the case of the first wall). Limiting N below concentrations of 100 ppm will not be possible for a large scale melt, but concentrations of Al up to the maximum amount that has been achieved present no problems.

  3. Analysis of ferrite grain growth mechanisms during {gamma}-{alpha} transformation in a niobium alloyed steel using EBSD

    Energy Technology Data Exchange (ETDEWEB)

    Novillo, E. [CEIT and TECNUN, P Manuel de Lardizabal 15, 20018 Donostia-San Sebastian (Spain); Hernandez, D. [CEIT and TECNUN, P Manuel de Lardizabal 15, 20018 Donostia-San Sebastian (Spain); Gutierrez, I. [CEIT and TECNUN, P Manuel de Lardizabal 15, 20018 Donostia-San Sebastian (Spain)]. E-mail: igutierrez@ceit.es; Lopez, B. [CEIT and TECNUN, P Manuel de Lardizabal 15, 20018 Donostia-San Sebastian (Spain)

    2004-11-15

    The austenite to ferrite phase transformation was studied in a C-Mn-Nb steel after different hot deformation schedules, leading to deformed and recrystallized austenite. The mechanisms of nucleation and growth of ferrite grains were investigated by means of the electron back scattered diffraction (EBSD) technique. The ferrite microstructures were characterised in terms of the misorientation angles between ferrite grains and the deviations from an ideal Kurdjumov-Sachs orientation relationship with the austenite. The results show that the grain refinement produced by the accumulation of the deformation in the austenite is limited to a certain extent by the ferrite grain coarsening taking place behind the transformation front. Both coalescence and normal grain growth have been observed to contribute to this coarsening. Coalescence is enhanced as a result of the variant selection taking place in transformation from a recrystallized austenite. The accumulation of the deformation in the austenite results in ferrite-ferrite boundaries of higher misorientation, causing coalescence in this case to be less favoured, as compared with normal grain growth.

  4. Influence of ion-irradiation on hardness change in type 304 stainless steel weldment containing delta(δ) ferrite

    International Nuclear Information System (INIS)

    Differences of high energy-ion induced microstructure of bcc δ-ferrite and fcc austenite matrix, and the effects of δ-ferrite on the Vickers micro-hardness (Hv) after irradiation were investigated for Type 304 stainless steel weldments containing two different δ-ferrite contents: ferrite number (FN) 5.5 and 8.5, respectively. Specimens were irradiated to 1.5 dpa with 8 MeV Fe+4 ions using a Tandem Vande-Graff accelerator (flux: 4.3 x 1010 ion/cm2·s, fluence: 0.83 x 1015 ion/cm2) at below 60 degC. Calculations TRIM 95 showed that a peak damage appeared at 1.5 μm in depth with 0.7 μm full width at half maximum (FWHM). These results on irradiation-induced defects (IIDs) distribution were confirmed by TEM. Clear differences for the size and number density of IIDs as black dots (size: 5-10 nm) and loops observed in both the austenitic matrix and δ-ferrite, where the size of IIDs was far larger in the fcc matrix than the bcc δ-ferrite. Hv test results showed that the irradiation hardening of δ-ferrite was about 1.5 times larger than the austenitic matrix. From microstructural observation the increase of the higher Vickers micro-hardness was explained. (author)

  5. Investigation on the Behavior of Austenite and Ferrite Phases at Stagnation Region in the Turning of Duplex Stainless Steel Alloys

    Science.gov (United States)

    Nomani, J.; Pramanik, A.; Hilditch, T.; Littlefair, G.

    2016-06-01

    This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite.

  6. Optimisation of a Nanostructured ODS Ferritic Steel Fabrication towards Improvement of its Plasticity

    International Nuclear Information System (INIS)

    Full text: In order to increase the operation temperature of the high-chromium reduced activation steels foreseen in applications of fusion reactors, ferritic steels containing 12 to 14% Cr in weight and reinforced with a dispersion of nano-oxides are being under development. The nano-oxides are incorporated into the matrix by adding Y2O3 or Fe-Y intermetallic particles to the initial steel powder, and by performing an intensive ball milling. In order to produce an ODS-steel with better mechanical properties, two specific actions of the production route were considered in this work to minimize the air contamination and porosity. The first one consists in using a higher purity pre-alloyed steel powder instead of mixture of elemental powders. The second one is to perform an additional densification after the hot-isostatic pressing (HIP) by hot cross rolling (HCR) the consolidated HIPed ingot. The steel powders batches were produced by ball milling of either elemental or pre-alloyed powders with Y2O3 or Fe2Y reinforcement particles in attritor, applying a hydrogen milling atmosphere at a controlled pressure and subsequent hot isostatic pressing. The influence of the type of substrate powders on the mechanical properties was studied for the ODS steels after HIP and after a thermal-mechanical treatment. HCR were applied at a temperature of 800 deg C. Optical microscope observations revealed a refinement of the microstructure with smaller porosity. Transmission electron microscope observations of the HCR ODS steel samples microstructures showed mainly recovered grains but also a slight coarsening of the finest oxides particles compared with the steel after HIP. Grains elongation in the rolling plane or in the normal plane was not observed. Hot cross-rolling resulted in an increase of ultimate tensile strength and a significant decrease of the ductile to brittle transition temperature (DBTT). While a lower DBTT has been found for the ODS steels on which HCR was applied

  7. Concurrent microstructural evolution of ferrite and austenite in a duplex stainless steel processed by high-pressure torsion

    International Nuclear Information System (INIS)

    A duplex stainless steel with approximately equal volume fractions of ferrite and austenite was processed by high-pressure torsion. Nano-indentation, electron backscatter diffraction and transmission electron microscopy were used to investigate the hardness and microstructure evolutions of the steel. Despite the different strain-hardening rates of individual ferrite and austenite, the microstructures of the two phases evolved concurrently in such a way that the neighbouring two phases always maintained similar hardness. While the plastic deformation and grain refinement of ferrite occurred mainly via dislocation activities, the plastic deformation and grain refinement process of austenite were more complicated and included deformation twinning and de-twinning in coarse grains, grain refinement by twinning and dislocation–twin interactions, de-twinning in ultrafine grains and twin boundary subdivision

  8. On the fatigue behaviour of electron beam and gas tungsten arc weldments of 409M grade ferritic stainless steel

    International Nuclear Information System (INIS)

    Highlights: ► Fatigue behaviour of EBW and GTAW joints of ferritic stainless steel is reported. ► Effect of the microstructure, tensile properties and residual stresses are discussed. ► EBW joint showed superior fatigue performance compared to GTAW joint. ► Fine dual phase microstructure acted beneficially in retarding the crack growth. -- Abstract: Fatigue life and fatigue crack growth behaviour of the electron beam welded AISI 409M ferritic stainless steel joints in comparison with the gas tungsten arc welded joint and the base metal was studied. It is found that the joint fabricated by the electron beam welding process exhibited superior fatigue performance than that of the gas tungsten arc welded joint. Formation of a dual phase lath ferrite with fine martensitic microstructure, superior tensile properties and favourable residual stress field are the main reasons for the enhanced fatigue life and fatigue crack resistance of the electron beam welded joint.

  9. Experimental and Numerical Study on the Effect of ZDDP Films on Sticking During Hot Rolling of Ferritic Stainless Steel Strip

    Science.gov (United States)

    Hao, Liang; Jiang, Zhengyi; Wei, Dongbin; Gong, Dianyao; Cheng, Xiawei; Zhao, Jingwei; Luo, Suzhen; Jiang, Laizhu

    2016-10-01

    The aim of this study is to investigate the effect of zinc dialkyl dithio phosphate (ZDDP) films on sticking during hot rolling of a ferritic stainless steel strip. The surface characterization and crack propagation of the oxide scale are very important for understanding the mechanism of the sticking. The high-temperature oxidation of one typical ferritic stainless was conducted at 1373 K (1100 °C) for understanding its microstructure and surface morphology. Hot-rolling tests of a ferritic stainless steel strip show that no obvious cracks among the oxide scale were observed with the application of ZDDP. A finite element method model was constructed with taking into consideration different crack size ratios among the oxide scale, surface profile, and ZDDP films. The simulation results show that the width of the crack tends to be reduced with the introduction of ZDDP films, which is beneficial for improving sticking.

  10. The development of carbides in the phase boundary between delta ferrite and martensite in 9-14% chromium steels

    International Nuclear Information System (INIS)

    Materials with a sufficient toughness have to be used for safety-relevant components. In martensitic 12% chromium steels delta ferrite may occur, at higher contents (>0,5%) the fracture toughness of the material may be reduced considerably. This means that the DBTT (ductile to brittle transition temperature) is shifted towards higher temperatures during impact tests. In two-phase steels consisting of delta-ferrite and martensite, this behavior of brittle fracture is found to be caused by the massive dendritic carbide surrounding the delta-ferrite. The generation of this carbide is described by means of CCT diagrams (continuous cooling transformation diagrams). Carbide formation depends on both the chromium content and the cooling velocity. (orig.)

  11. TEM Study of the Orientation Relationship Between Cementite and Ferrite in a Bainitic Low Carbon High Strength Low Alloy Steel

    OpenAIRE

    Illescas Fernandez, Silvia; Brown, A P; He, K.; Fernández, Javier; Guilemany Casadamon, Josep Maria

    2005-01-01

    Two different bainitic structures are observed in a steel depending on the sample heat treatment. The different types of bainitic structures exhibit different orientation relationships between cementite and the ferrite matrix. Upper bainite presents a Pitsch orientation relationship and lower bainite presents a Bagaryatski orientation relationship. Different heat treatments of low carbon HSLA steel samples have been studied using TEM in order to find the orientation relationshi...

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

    Science.gov (United States)

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

    2015-10-01

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

  13. Microstructural characterizations of 14Cr ODS ferritic steels subjected to hot torsion

    Energy Technology Data Exchange (ETDEWEB)

    Karch, A., E-mail: abdellatif.karch@gmail.com [CEA, DEN, Service de Recherches Métallurgiques Appliquées, 91191 Gif-sur-Yvette (France); Centre de mise en forme des matériaux (CEMEF), Mines Paris-tech, CNRS UMR 7635, BP 207, 1 rue Claude Daunesse, 06904 Sophia Antipolis Cedex (France); Sornin, D.; Barcelo, F.; Bosonnet, S.; Carlan, Y. de [CEA, DEN, Service de Recherches Métallurgiques Appliquées, 91191 Gif-sur-Yvette (France); Logé, R. [Laboratory of Thermomechanical Metallurgy – PX Group Chair, Ecole Polytechnique Fédérale de Lausanne (EPFL), Rue de la Maladière 71b – CP 526, CH-2002 Neuchâtel (Switzerland)

    2015-04-15

    Oxide dispersion strengthened (ODS) steels are very promising materials for nuclear applications. In this paper, the hot working behavior of ODS ferritic steels, consolidated by hot extrusion, is studied through torsion tests. Three ODS steels are produced acting on both the quantity of Ti and Y{sub 2}O{sub 3} added to the matrix (wt% Fe–14Cr–1W), and the density and size of the nanoparticles. A temperature range of 1000–1200 °C and strain rates from 5 ⋅ 10{sup −2} to 5 s{sup −1} are considered. The microstructures of deformed samples are examined by Electron Back-Scatter Diffraction and X-ray diffraction techniques. It is observed that hot plastic strain leads to an early damage with nucleation and growth of cavities along grain boundaries. Except for the damage, very few microstructural and textural evolutions are noticed. The three tested ODS steels exhibit almost the same behavior under hot torsion straining, regardless of the precipitation state. Overall, the experimental results are interpreted through a mechanism of strain accommodation at grain boundaries, with low dislocation activity in the bulk of the grains.

  14. Texture evolution in Nb-containing ferritic stainless steels during secondary recrystallization

    International Nuclear Information System (INIS)

    The texture evolution of three ferritic stainless steels (FSSs) with small additions of niobium after annealing at 1523 K for 2 h to promote secondary recrystallization (SR) was investigated. The 4-mm sheets containing 16 wt.% Cr and distinct niobium contents (0.31, 0.37 and 0.56 wt.%) were obtained by hot rolling. Carbon and nitrogen contents for the two first steels are 0.02 wt.% C and 0.02 wt.% N. The third steel (0.56 wt.% Nb) contains 0.03 wt.% C and 0.03 wt.% N. The crystallographic textures were determined by conventional X-ray diffraction (XRD). The microstructure was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show that hot band sheets display partial recrystallization. The Goss grains from primary recrystallization are found predominantly close to the surface. Pancake-like recovered grains displaying pronounced (0 0 1) and α-fiber texture components are present at the center layer. Grains displaying abnormal growth are noticeable in the three samples after SR annealing. The texture of the hot bands was evaluated with respect to the composition and through-thickness effects. The results were compared to other FSSs and bcc materials such as low-carbon and silicon steels

  15. Texture evolution in Nb-containing ferritic stainless steels during secondary recrystallization

    Energy Technology Data Exchange (ETDEWEB)

    Siqueira, R.P. [Departamento de Engenharia de Materiais, Escola de Engenharia de Lorena (EEL), USP, P.O. Box 116, Lorena, SP 12600-970 (Brazil); Sandim, H.R.Z. [Departamento de Engenharia de Materiais, Escola de Engenharia de Lorena (EEL), USP, P.O. Box 116, Lorena, SP 12600-970 (Brazil)], E-mail: hsandim@demar.eel.usp.br; Oliveira, T.R. [Centro de Pesquisa da ArcelorMittal Inox Brasil, Praca 1o de Maio, 9, Timoteo, MG 12228-904 (Brazil)

    2008-12-15

    The texture evolution of three ferritic stainless steels (FSSs) with small additions of niobium after annealing at 1523 K for 2 h to promote secondary recrystallization (SR) was investigated. The 4-mm sheets containing 16 wt.% Cr and distinct niobium contents (0.31, 0.37 and 0.56 wt.%) were obtained by hot rolling. Carbon and nitrogen contents for the two first steels are 0.02 wt.% C and 0.02 wt.% N. The third steel (0.56 wt.% Nb) contains 0.03 wt.% C and 0.03 wt.% N. The crystallographic textures were determined by conventional X-ray diffraction (XRD). The microstructure was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show that hot band sheets display partial recrystallization. The Goss grains from primary recrystallization are found predominantly close to the surface. Pancake-like recovered grains displaying pronounced (0 0 1)<0 1 1> and {alpha}-fiber texture components are present at the center layer. Grains displaying abnormal growth are noticeable in the three samples after SR annealing. The texture of the hot bands was evaluated with respect to the composition and through-thickness effects. The results were compared to other FSSs and bcc materials such as low-carbon and silicon steels.

  16. Mechanism study of sticking occurring during hot rolling of ferritic stainless steel

    International Nuclear Information System (INIS)

    Mechanisms of sticking phenomena occurring during hot rolling of a modified STS 430J1L ferritic stainless steel have been investigated in this study by using a pilot-plant-scale rolling machine. As the rolling pass proceeds, the Fe-Cr oxide layer formed in a reheating furnace is destroyed, and the destroyed oxides penetrate into the rolled steel to form a thin oxide layer on the surface region. The sticking does not occur on the surface region containing oxides, whereas it occurs on the surface region without oxides by the separation of the rolled steel at high temperatures. This indicates that the resistance to sticking increases by the increase in the surface hardness when a considerable amount of oxides are formed on the surface region, and that the sticking can be evaluated by the volume fraction and distribution of oxides formed on the surface region. The lubrication and the increase of the rolling speed and rolling temperature beneficially affect to the resistance to sticking because they accelerate the formation of oxides on the steel surface region. In order to prevent or minimize the sticking, thus, it is suggested to increase the thickness of the oxide layer formed in the reheating furnace and to homogeneously distribute oxides along the surface region by controlling the hot-rolling process

  17. Constitutive modeling of the mechanical behavior of high strength ferritic steels for static and dynamic applications

    Science.gov (United States)

    Abed, Farid H.

    2010-11-01

    A constitutive relation is presented in this paper to describe the plastic behavior of ferritic steel over a broad range of temperatures and strain rates. The thermo-mechanical behavior of high strength low alloy (HSLA-65) and DH-63 naval structural steels is considered in this study at strains over 40%. The temperatures and strain rates are considered in the range where dynamic strain aging is not effective. The concept of thermal activation analysis as well as the dislocation interaction mechanism is used in developing the flow model for both the isothermal and adiabatic viscoplastic deformation. The flow stresses of the two steels are very sensitive to temperature and strain rate, the yield stresses increase with decreasing temperatures and increasing strain rates. That is, the thermal flow stress is mainly captured by the yield stresses while the hardening stresses are totally pertained to the athermal component of the flow stress. The proposed constitutive model predicts results that compare very well with the measured ones at initial temperature range of 77 K to 1000 K and strain rates between 0.001 s-1 and 8500 s-1 for both steels.

  18. HRTEM Study of the Role of Nanoparticles in ODS Ferritic Steel

    Energy Technology Data Exchange (ETDEWEB)

    Hsiung, L; Tumey, S; Fluss, M; Serruys, Y; Willaime, F

    2011-08-30

    Structures of nanoparticles and their role in dual-ion irradiated Fe-16Cr-4.5Al-0.3Ti-2W-0.37Y{sub 2}O{sub 3} (K3) ODS ferritic steel produced by mechanical alloying (MA) were studied using high-resolution transmission electron microscopy (HRTEM) techniques. The observation of Y{sub 4}Al{sub 2}O{sub 9} complex-oxide nanoparticles in the ODS steel imply that decomposition of Y{sub 2}O{sub 3} in association with internal oxidation of Al occurred during mechanical alloying. HRTEM observations of crystalline and partially crystalline nanoparticles larger than {approx}2 nm and amorphous cluster-domains smaller than {approx}2 nm provide an insight into the formation mechanism of nanoparticles/clusters in MA/ODS steels, which we believe involves solid-state amorphization and re-crystallization. The role of nanoparticles/clusters in suppressing radiation-induced swelling is revealed through TEM examinations of cavity distributions in (Fe + He) dual-ion irradiated K3-ODS steel. HRTEM observations of helium-filled cavities (helium bubbles) preferably trapped at nanoparticle/clusters in dual-ion irradiated K3-ODS are presented.

  19. Effect of solute atoms on thermal fatigue properties in ferritic stainless steels

    International Nuclear Information System (INIS)

    The hardening ability of some substitutional solute atoms was investigated and compared. It was theoretically shown that solute atoms have the effect to enhance the necking resistance during creep deformation at high temperatures and can improve the thermal fatigue property of the steels. Molybdenum which is known to have large solid solution hardening ability improves the thermal fatigue property by the solid solution hardening itself, plus the enhanced necking resistance through increase in strain rate exponent. Aluminum which is known to improve the oxidation resistance of the ferritic stainless steels has a sufficient solid solution hardening ability. Thermal fatigue life of the steel was improved by a small amount of Al addition. It can be ascribed to the solid solution hardening ability of Al plus the enhanced necking resistance through increase in strain rate exponent due to Al addition. The addition of the appropriate amount of Si would make the effect of solute Al more efficient by improving the oxidation resistance of the steel

  20. Diffusion Bonding Beryllium to Reduced Activation Ferritic Martensitic Steel: Development of Processes and Techniques

    Science.gov (United States)

    Hunt, Ryan Matthew

    Only a few materials are suitable to act as armor layers against the thermal and particle loads produced by magnetically confined fusion. These candidates include beryllium, tungsten, and carbon fiber composites. The armor layers must be joined to the plasma facing components with high strength bonds that can withstand the thermal stresses resulting from differential thermal expansion. While specific joints have been developed for use in ITER (an experimental reactor in France), including beryllium to CuCrZr as well as tungsten to stainless steel interfaces, joints specific to commercially relevant fusion reactors are not as well established. Commercial first wall components will likely be constructed front Reduced Activation Ferritic Martensitic (RAFM) steel, which will need to be coating with one of the three candidate materials. Of the candidates, beryllium is particularly difficult to bond, because it reacts during bonding with most elements to form brittle intermetallic compounds. This brittleness is unacceptable, as it can lead to interface crack propagation and delamination of the armor layer. I have attempted to overcome the brittle behavior of beryllium bonds by developing a diffusion bonding process of beryllium to RAFM steel that achieves a higher degree of ductility. This process utilized two bonding aids to achieve a robust bond: a. copper interlayer to add ductility to the joint, and a titanium interlayer to prevent beryllium from forming unwanted Be-Cu intermetallics. In addition, I conducted a series of numerical simulations to predict the effect of these bonding aids on the residual stress in the interface. Lastly, I fabricated and characterized beryllium to ferritic steel diffusion bonds using various bonding parameters and bonding aids. Through the above research, I developed a process to diffusion bond beryllium to ferritic steel with a 150 M Pa tensile strength and 168 M Pa shear strength. This strength was achieved using a Hot Isostatic

  1. Research and Development of Reduced Activation Ferritic/Martensitic Steel CLF-1 in SWIP

    International Nuclear Information System (INIS)

    Full text: Because of the good industrial bases and the superior resistance for irradiation, reduced activation ferritic/martensitic (RAFM) steel is recognized as the primary structural material for ITER test blanket modules (TBM) and a DEMOnstration reactor. In China, one of the basic options of the blanket module concept to be tested in ITER is helium cooled solid breeder (HCSB) with the RAFM steel as the reference structural material. To provide material and property database for the design and fabrication of the ITER HCSB TBM, a new type of RAFM steel CLF-1 was developed and characterized by South Western Institute of Physics in China. In this paper, recent progress in SWIP research on RAFM steel CLF-1 R and D is reviewed with a focus on ITER-TBM design and fabrication. A new heat of 350 kg of CLF-1 steel was produced recently and different product forms (plates, rods and welding wires) were manufactured. Recent advances in the fields of steel development, mainly on the melting and processing techniques, composition optimization and thermo-mechanical treatment were addressed. The properties database and technical information required for blanket design and fabrication were derived. From the tensile and creep properties test, the design allowable stresses are derived. From the Charpy impact test, ductile to brittle transition temperature (DBTT) are evaluated. From the physical properties databases, density, modulus of elasticity, thermal conductivity, thermal diffusivity, specific heat, linear expansion coefficients are derived. The effect of thermal ageing on the microstructure and properties was investigated to study the stability under high temperature for long periods of time. In addition, the efforts to characterize the weldability of CLF-1 using tungsten-inert-gas (TIG) method for the fabrication of TBM were also introduced. (author)

  2. Surface and electrochemical characterization of nano zinc ferrite coating on carbon steel

    International Nuclear Information System (INIS)

    The structural materials in nuclear power reactors are mainly iron and nickel based alloys. Operation of these nuclear reactors at high temperatures and high pressures for a longer duration leads to the formation of various oxides due to the corrosion of the structural materials and the nature of these oxides depend on the chemical environment prevailed. Since the corrosion process is electrochemical in nature, the interface formed between the alloys and oxides play a crucial role in deciding the overall corrosion resistance of the structural materials. Therefore, modifying these oxides to nano size would improve the adherence and protectiveness of the interfacial film. In this context, the chemical synthesis of zinc ferrite (ZnFe2O4) was carried out by precipitation method using zinc sulphate and iron ammonium sulphate. The synthesized ferrite powder was confirmed by Raman Spectroscopy. X-Ray Diffraction studies showed that the intensity and the ‘d’ values of the observed diffraction peaks perfectly match with the single-crystalline cubic spinel form of zinc ferrite having lattice constant a=8.436 Å. The 10 mm diameter ferrite targets were prepared using synthesized ZnFe2O4 powder by sintering at 1000°C for 24 hours. Thin film of ZnFe2O4 was deposited on Carbon Steel specimens using pulsed laser deposition technique. Characterization of this deposited ferrite was carried out by Raman spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy and Secondary Electron Microscopy. Raman data of coated ZnFe2O4 matched with the standard ZnFe2O4 oxide. X-ray diffraction pattern indicated that the sample was in single phase with an average grain size 30 nm. XPS data indicated the formation of ZnFe2O4. Scanning electron microscopy technique was used to analyze the surface film morphology. The mechanism of corrosion resistance/improvement in the deposited layer was studied by electrochemical techniques and the results are presented in detail in this paper

  3. Transformation of austenite to duplex austenite-ferrite assembly in annealed stainless steel 316L consolidated by laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Saeidi, K.; Gao, X. [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden); Lofaj, F. [Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, Košice (Slovakia); Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 916 24 Trnava (Slovakia); Kvetková, L. [Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, Košice (Slovakia); Shen, Z.J. [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden)

    2015-06-05

    Highlights: • Mechanical properties, phase and microstructure stability of laser melted steel was studied. • Duplex austenite-ferrite assembly with improved mechanical properties was formed. • Dissolution of Mo in the steel matrix resulted in ferrite stabilization and stress relief. • Enhanced mechanical properties were achieved compared to conventionally casted and annealed steel. - Abstract: Laser melting (LM), with a focused Nd:YAG laser beam, was used to form solid bodies from 316L austenite stainless steel powder and the laser melted samples were heat treated at various temperatures. The phase changes in heat treated samples were characterized using X-ray diffraction (XRD). Samples heat treated at 800 °C and 900 °C remained single austenite while in samples heat treated at 1100 °C and 1400 °C a dual austenite-ferrite phase assembly was formed. The ferrite formation was further verified by electron back scattering diffraction (EBSD) and selective area diffraction (SAD). Microstructural changes were studied by scanning and transmission electron microscopy (SEM, TEM). In samples heat treated up to 900 °C, coalescence of the cellular-sub grains was noticed, whereas in sample heat treated at and above 1100 °C the formation of ferrite phase was observed. The correlation between the microstructure/phase assembly and the measured strength/microhardness were investigated, which indicated that the tensile strength of the laser melted material was significantly higher than that of the conventional 316L steel even after heat treatment whereas caution has to be taken when laser melted material will be exposed to an application temperature above 900 °C.

  4. Transformation of austenite to duplex austenite-ferrite assembly in annealed stainless steel 316L consolidated by laser melting

    International Nuclear Information System (INIS)

    Highlights: • Mechanical properties, phase and microstructure stability of laser melted steel was studied. • Duplex austenite-ferrite assembly with improved mechanical properties was formed. • Dissolution of Mo in the steel matrix resulted in ferrite stabilization and stress relief. • Enhanced mechanical properties were achieved compared to conventionally casted and annealed steel. - Abstract: Laser melting (LM), with a focused Nd:YAG laser beam, was used to form solid bodies from 316L austenite stainless steel powder and the laser melted samples were heat treated at various temperatures. The phase changes in heat treated samples were characterized using X-ray diffraction (XRD). Samples heat treated at 800 °C and 900 °C remained single austenite while in samples heat treated at 1100 °C and 1400 °C a dual austenite-ferrite phase assembly was formed. The ferrite formation was further verified by electron back scattering diffraction (EBSD) and selective area diffraction (SAD). Microstructural changes were studied by scanning and transmission electron microscopy (SEM, TEM). In samples heat treated up to 900 °C, coalescence of the cellular-sub grains was noticed, whereas in sample heat treated at and above 1100 °C the formation of ferrite phase was observed. The correlation between the microstructure/phase assembly and the measured strength/microhardness were investigated, which indicated that the tensile strength of the laser melted material was significantly higher than that of the conventional 316L steel even after heat treatment whereas caution has to be taken when laser melted material will be exposed to an application temperature above 900 °C

  5. Effect of Co deposition on oxidation behavior and electrical properties of ferritic steel for solid oxide fuel cell interconnects

    Energy Technology Data Exchange (ETDEWEB)

    Kruk, A.; Adamczyk, A.; Gil, A. [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059 Krakow (Poland); Kąc, S. [AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science, al. Mickiewicza 30, 30-059 Krakow (Poland); Dąbek, J.; Ziąbka, M. [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059 Krakow (Poland); Brylewski, T., E-mail: brylew@agh.edu.pl [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059 Krakow (Poland)

    2015-09-01

    In this work, a Co layer deposited on DIN 50049 steel by means of pulsed laser deposition was applied for the protection of solid oxide fuel cell (SOFC) interconnects operating on the cathode side. The coated and uncoated steel samples were oxidized in air at 1073 K for 500 h, and their microstructures as well as electrical resistances were evaluated using X-ray diffraction, atomic force microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and the 2-probe 4-point direct current method. It was demonstrated that the Co coating had reduced the oxidation rate of the steel by nearly a half. The area-specific resistance value of the coated steel was 5 × 10{sup −6} Ω·m{sup 2}, which was significantly lower than that of bare steel after 350 h of oxidation at 1073 K. Cr vaporization tests showed that the Co coating was efficient at blocking the outward diffusion of Cr. The obtained results prove that steel coated with a thin film of cobalt was suitable for use as metallic interconnect material in SOFCs operating at intermediate temperatures. - Highlights: • Co layer was deposited on ferritic steel by means of pulsed laser deposition. • Coated and bare ferritic steel samples were exposed to air at 1073 K for 500 h. • Scale growth rate on bare steel is higher than that on coated steel. • Electrical resistance for oxidized coated steel was lower than for bare steel. • Co-coated steel effectively reduced the formation of volatile Cr species.

  6. Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel%Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    A K Lakshminarayanan; V Balasubramanian

    2012-01-01

    The microstructure analysis and mechanical properties evaluation of laser beam welded AISI 409M ferritic stainless steel joints are investigated. Single pass autogeneous welds free of volumetric defects were produced at a welding speed of 3 000 mm/min. The joints were subjected to optical microscope, scanning electron fractographe, microhardness, transverse and longitudinal tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the base metal were changed into dendritic grains as a result of rapid solidification of laser beam welds. Tensile testing indicates overmatching of the weld metal is relative to the base metal. The joints also exhibited acceptable impact toughness and bend strength properties.

  7. Effects of δ-ferrite and welding structure on high-cycle fatigue properties of austenitic stainless steels weld metals

    International Nuclear Information System (INIS)

    We studied the effects of δ-ferrite and welding structure on high-cycle fatigue properties for austenitic stainless steel weld metals at cryogenic temperatures. SUS304L and SUS316L weld metals contained 0% δ-ferrite (0% material) and 10% δ-ferrite (10% material) were prepared. High-cycle fatigue tests were carried out at 293, 77 and 4 K. The S-N curves of those weld metals shifted towards higher stress levels, i.e., the longer life side, with decreasing test temperature. The ratios of 106-cycles fatigue strength (FS) to tensile strength (TS) of 0% material decreased from 0.8 to 0.45 and those of 10% material decreased between 0.35 to 0.65 with decreasing test temperature. Fatigue crack initiation sites of SUS304L 10% material were almost at blowholes, and those of SUS316L 10% material were at weld pass interface boundaries. On the other hand, those of 0% materials were considered to be due to the interface of the solidification structure. Although δ-ferrite reduces toughness at cryogenic temperatures in austenitic stainless steel weld metals, the effects of δ-ferrite on high-cycle fatigue properties are not significant

  8. Modification in the Microstructure of Mod. 9Cr-1Mo Ferritic Martensitic Steel Exposed to Sodium

    Science.gov (United States)

    Prasanthi, T. N.; Sudha, Cheruvathur; Paul, V. Thomas; Bharasi, N. Sivai; Saroja, S.; Vijayalakshmi, M.

    2014-09-01

    Mod. 9Cr-1Mo is used as the structural material in the steam generator circuit of liquid metal-cooled fast breeder reactors. Microstructural modifications on the surface of this steel are investigated after exposing to flowing sodium at a temperature of 798 K (525 °C) for 16000 hours. Sodium exposure results in the carburization of the ferritic steel up to a depth of ~218 µm from the surface. Electron microprobe analysis revealed the existence of two separate zones with appreciable difference in microchemistry within the carburized layer. Differences in the type, morphology, volume fraction, and microchemistry of the carbides present in the two zones are investigated using analytical transmission electron microscopy. Formation of separate zones within the carburized layer is understood as a combined effect of leaching, diffusion of the alloying elements, and thermal aging. Chromium concentration on the surface in the α-phase suggested possible degradation in the corrosion resistance of the steel. Further, concentration-dependent diffusivities for carbon are determined in the base material and carburized zones using Hall's and den Broeder's methods, respectively. These are given as inputs for simulating the concentration profiles for carbon using numerical computation technique based on finite difference method. Predicted thickness of the carburized zone agrees reasonably well with that of experiment.

  9. Corrosion and radiation response of advanced ferritic-martensitic steels for Generation IV application

    International Nuclear Information System (INIS)

    For many Generation IV systems, ferritic-martensitic steels are considered candidates for core internals, cladding, or pressure vessels. The radiation response to proton and heavy ion irradiation and the corrosion response in supercritical water and lead-bismuth eutectic of two advanced steels, specifically HCM12A (Grade 122) and a 9Cr Oxide Dispersion Strengthened (ODS) steel are reported in this work. The HCM12A appears to harden in a similar manner to T91. In the 9Cr ODS alloy, the oxides particles shrink slightly under high heavy ion irradiation, but this loss in size is accompanied by an increase in density such that any loss of hardening appears to be negligible. When exposed to SCW, the 9Cr ODs alloy has a thinner and less porous oxide than HCM12A. Although the inner oxide layers of HCM12A exposed in SCW and LBE have some similarity, the outer magnetite layer has smaller and equiaxed grains when exposed to LBE as opposed to the large columnar grains when exposed in SCW. (author)

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

    Directory of Open Access Journals (Sweden)

    Choudhary R.K.

    2014-01-01

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

  11. Fracture behavior evaluations for ferritic steel piping with circumferential double flaws on the inner surface

    International Nuclear Information System (INIS)

    Methods for assessing the structural integrity of nuclear components having some flaws are provided in the Rules on Fitness-for-Service for Nuclear Power Plants of the JSME code (JSME FFS code). Although the JSME FFS code provides such methods for piping with a single flaw, it does not describe any method for fracture assessment of piping with multiple flaws including flaw coalescence criteria. Some investigations on the fracture behavior of mainly austenitic stainless steel piping with multiple flaws, whose fracture mode is plastic collapse, have recently been reported and fracture assessment methods have been proposed. In the present study, fracture tests and analyses of carbon steel piping with a single and two circumferential flaw(s) on the inner surface were conducted to investigate a method for fracture assessment of ferritic steel piping with multiple flaws. It was found that fracture assessment based on the twice elastic slope method and the plastic collapse mechanism gave inadequate results for a large single flaw. Including this case, two kinds of elastic–plastic fracture assessment method, one using the Z-factor in the JSME FFS code and the other by ductile instability analysis, gave conservative estimates of fracture strength even when the structural factor SF was not considered (i.e. SF = 1)

  12. Effect of silicon on the microstructure and mechanical properties of reduced activation ferritic/martensitic steel

    Science.gov (United States)

    Chen, Shenghu; Rong, Lijian

    2015-04-01

    The effect of Si in the range of 0.05-0.77 wt.% on the microstructure, tensile properties and impact toughness of reduced activation ferritic/martensitic (RAFM) steels has been investigated. An increase in Si content affected the prior austenite grain size resulting in an increase in the tensile strength at room temperature. The tensile strength of steels tested above 773 K did not change significantly with the addition of Si, which was due to the diminished carbide hardening effect and boundary strengthening effect. Detailed fractographic analysis revealed that tear fractures occurred in the samples tensile tested at room temperature, while cup and cone fractures were found in samples tensile tested at temperatures above 773 K, which were induced by the easing of dislocation pile-ups. The ductile-to-brittle transition temperature (DBTT) decreased when the Si content increased to 0.22 wt.%. However, the DBTT increased when the Si content reached 0.77 wt.% and this was due to the precipitation of Laves phase. The RAFM steel with approximately 0.22 wt.% Si content was found to possess an optimized combination of microstructure, tensile properties and impact toughness.

  13. Radiation damage in ferritic/martensitic steels for fusion reactors: a simulation point of view

    Science.gov (United States)

    Schäublin, R.; Baluc, N.

    2007-12-01

    Low activation ferritic/martensitic steels are good candidates for the future fusion reactors, for, relative to austenitic steels, their lower damage accumulation and moderate swelling under irradiation by the 14 MeV neutrons produced by the fusion reaction. Irradiation of these steels, e.g. EUROFER97, is known to produce hardening, loss of ductility, shift in ductile to brittle transition temperature and a reduction of fracture toughness and creep resistance starting at the lowest doses. Helium, produced by transmutation by the 14 MeV neutrons, is known to impact mechanical properties, but its effect at the microstructure level is still unclear. The mechanisms underlying the degradation of mechanical properties are not well understood, despite numerous studies on the evolution of the microstructure under irradiation. This impedes our ability to predict materials' behaviour at higher doses for use in the future fusion reactors. Simulations of these effects are now essential. An overview is presented on molecular dynamics simulations of the primary state of damage in iron and of the mobility of a dislocation, vector of plasticity, in the presence of a defect.

  14. Aluminum clad ferritic stainless steel foil for metallic catalytic converter substrate applications

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.S.; Pandey, A.; Jha, B.

    1996-09-01

    A roll bonding process was developed to produce Al clad ferritic stainless steel foil for the metallic catalytic converter substrate application. Clad foils with different chemistry were produced and their properties were evaluated. Heat treatment conditions for the homogenization of clad foils were identified. This article includes results from oxidation tests and mechanical tests on as-rolled and heat treated clad foil. Results from commercial ingot metallurgy foil were also included for comparison. The oxidation weight gain study indicates that the Al content in the foils is directly related to the usable life of the foil. However, rare earth addition is necessary to improve the oxidation resistance of this material for the high temperature applications by slowing down the weight gain kinetics and thus extend the usable life of foils. The heat treated clad foil also exhibit excellent tensile ductility when compared to the ingot metallurgy foil.

  15. Plastic deformation-induced phosphorus segregation to ferrite grain boundaries in an interstitial free steel

    International Nuclear Information System (INIS)

    Research highlights: → Plastic deformation causes non-equilibrium grain boundary phosphorus segregation. → Deformation induced segregation increases with increasing deformation rate. → Non-equilibrium segregation is induced by supersaturated vacancy-phosphorus complex. → Model predictions show a reasonable agreement with the observations. - Abstract: Grain boundary concentration of phosphorus in an interstitial free steel is observed by virtue of Auger electron spectroscopy after the alloy is plastically deformed to different strains under different strain rates at a high temperature in the ferrite region. The results reveal that phosphorus segregates at grain boundaries during plastic deformation. The segregation increases with increasing deformation until reaching a steady value, and at the same deformation amount it increases with increasing strain rate. Model predictions are made, which shows a reasonable agreement between the predictions and the observations.

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

    Directory of Open Access Journals (Sweden)

    Juntao Yuan

    2014-04-01

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

  17. The correlation between yielding behavior and precipitation in ultra purified ferritic stainless steels

    International Nuclear Information System (INIS)

    Cold rolled sheets of a ultra purified ferritic stainless steel were annealed either by being slowly cooled from 950 deg. C or being rapidly cooled to room temperature from the intermediate holding at 750 deg. C. The former exhibited substantial Lueders elongation during tensile testing, while the later showed continuous yielding behavior. In the slowly cooled sheet, both Nb(C, N) and (Fe, Cr)2Nb have been formed, and no (Fe, Cr)2Nb could be observed in the rapidly cooled sheet. The fast growth of (Fe, Cr)2Nb is believed to have caused local depletion of Nb atoms around fine NbC particles, resulting in their dissolution and having carbon atoms released for the formation of the Cottrell atmosphere. These results have been confirmed by the internal friction measurements and thermodynamic calculations.

  18. Effect of niobium on corrosion resistance to sulfuric acid of 430 ferritic stainless steel

    Directory of Open Access Journals (Sweden)

    Neusa Alonso-Falleiros

    1998-10-01

    Full Text Available The influence of niobium on corrosion resistance to 0.5M H2SO4 of 17% Cr ferritic stainless steels, to which it was added in amounts larger than that necessary to stabilize the interstitial elements, was investigated. Their performance was compared to that of other two Fe-17%Cr alloys, one without additions and another containing 0.93% molybdenum. Through weight and electrochemical measurements and through morphologic examination of corroded surface it was found that the corrosion of these alloys, with the exception of that containing molybdenum, proceeds in two different steps. In the first step (up to about 60 min the corrosion rate practically does not change with time, the lower rates being displayed by alloys containing larger amounts of Nb. In the second stage the corrosion rate increases with time. The corrosion rate of Mo containing alloy is constant for all times.

  19. Thermo-mechanical fatigue behavior of reduced activation ferrite/martensite stainless steels

    International Nuclear Information System (INIS)

    The thermo-mechanical cycling fatigue (TMCF) behavior of reduced activation ferrite/martensite stainless steels is examined. The test rig consists of a stiff load frame, which is directly heated by the digitally controlled ohmic heating device. Cylindrical specimens are used with a wall thickness of 0.4 mm. Variable strain rates are applied at TMCF test mode, due to the constant heating rate of 5.8 K/s and variable temperature changes. TMCF results of as received EUROFER 97 in the temperature range between 100 and 500-600 deg. C show a reduction in life time (a factor of 2) compared to F82H mod. and OPTIFER IV. TMCF-experiments with hold times of 100 and 1000 s show dramatic reduction in life time for all three materials

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-07-01

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

  1. Characterization and Modeling of Grain Boundary Chemistry Evolution in Ferritic Steels under Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Marquis, Emmanuelle [Univ. of Michigan, Ann Arbor, MI (United States); Wirth, Brian [Univ. of Tennessee, Knoxville, TN (United States); Was, Gary [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-03-28

    Ferritic/martensitic (FM) steels such as HT-9, T-91 and NF12 with chromium concentrations in the range of 9-12 at.% Cr and high Cr ferritic steels (oxide dispersion strengthened steels with 12-18% Cr) are receiving increasing attention for advanced nuclear applications, e.g. cladding and duct materials for sodium fast reactors, pressure vessels in Generation IV reactors and first wall structures in fusion reactors, thanks to their advantages over austenitic alloys. Predicting the behavior of these alloys under radiation is an essential step towards the use of these alloys. Several radiation-induced phenomena need to be taken into account, including phase separation, solute clustering, and radiation-induced segregation or depletion (RIS) to point defect sinks. RIS at grain boundaries has raised significant interest because of its role in irradiation assisted stress corrosion cracking (IASCC) and corrosion of structural materials. Numerous observations of RIS have been reported on austenitic stainless steels where it is generally found that Cr depletes at grain boundaries, consistently with Cr atoms being oversized in the fcc Fe matrix. While FM and ferritic steels are also subject to RIS at grain boundaries, unlike austenitic steels, the behavior of Cr is less clear with significant scatter and no clear dependency on irradiation condition or alloy type. In addition to the lack of conclusive experimental evidence regarding RIS in F-M alloys, there have been relatively few efforts at modeling RIS behavior in these alloys. The need for predictability of materials behavior and mitigation routes for IASCC requires elucidating the origin of the variable Cr behavior. A systematic detailed high-resolution structural and chemical characterization approach was applied to ion-implanted and neutron-irradiated model Fe-Cr alloys containing from 3 to 18 at.% Cr. Atom probe tomography analyses of the microstructures revealed slight Cr clustering and segregation to dislocations and

  2. Long term high temperature oxidation characteristics of La and Cu alloyed ferritic stainless steels for solid oxide fuel cell interconnects

    Science.gov (United States)

    Swaminathan, Srinivasan; Lee, Young-Su; Kim, Dong-Ik

    2016-09-01

    To ensure the best performance of solid oxide fuel cell metallic interconnects, the Fe-22 wt.% Cr ferritic stainless steels with various La contents (0.006-0.6 wt.%) and Cu addition (1.57 wt.%), are developed. Long-term isothermal oxidation behavior of these steels is investigated in air at 800 °C, for 2700 h. Chemistry, morphology, and microstructure of the thermally grown oxide scale are examined using XPS, SEM-EDX, and XRD techniques. Broadly, all the steels show a double layer consisting of an inner Cr2O3 and outer (Mn, Cr)3O4. Distinctly, in the La-added steels, binary oxides of Cr, Mn and Ti are found at the oxide scale surface together with (Mn, Cr)3O4. Furthermore, all La-varied steels possess the metallic Fe protrusions along with discontinuous (Mn, Cr)3O4 spinel zones at the oxide scale/metal interface and isolated precipitates of Ti-oxides in the underlying matrix. Increase of La content to 0.6 wt.% is detrimental to the oxidation resistance. For the Cu-added steel, Cu is found to segregate strongly at the oxide scale/metal interface which inhibits the ingress of oxygen thereby suppressing the subscale formation of (Mn, Cr)3O4. Thus, Cu addition to the Fe-22Cr ferritic stainless steels benefits the oxidation resistance.

  3. Effect of Hot Coiling Under Accelerated Cooling on Development of Non-equiaxed Ferrite in Low Carbon Steel

    Science.gov (United States)

    Lanjewar, H. A.; Tripathi, Pranavkumar

    2016-06-01

    Strengthening mechanisms dominant in non-equiaxed ferrite structures are not so familiar and well measured. In present study, non-equiaxed ferritic structures were generated and perceived to be strengthened by grain/crystal refinement, presence of varying substructures, solid solution strengthening, and textural hardening. A Nb-V microalloyed steel was modeled under various accelerated cooling and coiling temperature conditions in a thermo-mechanical simulator. Decrease in coiling temperature in conjunction with accelerated cooling resulted in non-equiaxed ferrite structures with array of phase morphologies. Intermediate transformation conditions produced increase in strength concurrent with observed smallness in crystallite size and high amount of microstrain in the matrix phase indicative of high dislocation densities and crystal imperfections. Increase in strength is partially attributed to solid solution and texture hardening owing to increase in (111) pole intensity in structure.

  4. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gazder, Azdiar A., E-mail: azdiar@uow.edu.au [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Al-Harbi, Fayez; Spanke, Hendrik Th. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Mitchell, David R.G. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Pereloma, Elena V. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia)

    2014-12-15

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. - Highlights: • Multi-condition segmentation of austenite, martensite, polygonal ferrite and ferrite in bainite. • Ferrites in granular bainite and bainitic ferrite segmented by variation in relative carbon counts. • Carbon partitioning during growth explains variation in carbon content of ferrites in bainites. • Developed EBSD image processing tools can be applied to the microstructures of a variety of alloys. • EBSD-based segmentation procedure verified by correlative TEM results.

  5. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy

    International Nuclear Information System (INIS)

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. - Highlights: • Multi-condition segmentation of austenite, martensite, polygonal ferrite and ferrite in bainite. • Ferrites in granular bainite and bainitic ferrite segmented by variation in relative carbon counts. • Carbon partitioning during growth explains variation in carbon content of ferrites in bainites. • Developed EBSD image processing tools can be applied to the microstructures of a variety of alloys. • EBSD-based segmentation procedure verified by correlative TEM results

  6. Microalloyed V-Nb-Ti and V steels Pt. 1 - stereological study of ferrite-pearlite microstructure and its relationship to toughness

    Energy Technology Data Exchange (ETDEWEB)

    Tanniru, M.; Shanmugam, S.; Misra, R.D.K.; Panda, D.; Jansto, S.

    2005-02-15

    Stereological analysis was applied to quantify the ferrite-pearlite microstructure and relate it to the toughness of similar strength V-Nb-Ti and V microalloyed steels. The V-Nb-Ti and the V steel were characterised by average yield strengths of {approx} 375 and 363 MPa, respectively and an elongation of {approx} 20%. The relationship between the microstructure and toughness was investigated in terms of stereological parameters, namely: (a) mean intercept length of polygonal ferrite and its distribution, (b) mean intercept length of pearlite colonies and their distribution, (c) ferrite grain boundary surface area per unit volume, (d) total grain boundary surface area per unit volume, (e) contiguity ratio of ferrite grains and pearlite colonies, and (f) pearlite interlamellar spacing and its distribution. Stereological analysis of core and flange sections of beams of both steels indicated that the core and flange sections of V steel are characterised by a marginally finer ferrite grain size and narrower grain size distribution, higher contiguity ratio of ferrite grains, finer pearlite interlamellar spacing and its distribution, and more uniform distribution of pearlite colony size, in comparison with respective core and flange sections of the V-Nb-Ti steel. These characteristics influence the toughness of the investigated steels. (author)

  7. Mechanical and microstructural behaviour of isothermally and thermally fatigued ferritic/martensitic steels

    International Nuclear Information System (INIS)

    Isothermal low cycle fatigue (LCF) and thermal low cycle fatigue results in the temperature range between room temperature and 823 K of the quenched and tempered reduced activation ferritic/martensitic steels F82H mod. and EUROFER 97 are reported. Under these test conditions both steels show, after the first few cycles and for both types of tests, a pronounced cyclic softening up to failure. The softening during LCF tests described by a simple empirical relationship is dependent on temperature but independent of the total strain amplitude of the tests. From the analysis of the hysteresis loops and corroborated by electron microscopy observations it can be concluded that the cyclic softening is produced by the softening observed in the internal stress as a consequence of the evolution of the microstructure. During cycling, the martensitic lath structure with high dislocation density and carbides along the lath interfaces evolves to a softer dislocation subgrain structure. This conclusion could be correlated with transmission electron microscopy observations

  8. Microstructural changes induced near crack tip during corrosion fatigue tests in austenitic-ferritic steel.

    Science.gov (United States)

    Gołebiowski, B; Swiatnicki, W A; Gaspérini, M

    2010-03-01

    Microstructural changes occurring during fatigue tests of austenitic-ferritic duplex stainless steel (DSS) in air and in hydrogen-generating environment have been investigated. Hydrogen charging of steel samples during fatigue crack growth (FCG) tests was performed by cathodic polarization of specimens in 0.1M H(2)SO(4) aqueous solution. Microstructural investigations of specimens after FCG tests were carried out using transmission electron microscopy to reveal the density and arrangement of dislocations formed near crack tip. To determine the way of crack propagation in the microstructure, electron backscatter diffraction investigations were performed on fatigue-tested samples in both kinds of environment. To reveal hydrogen-induced phase transformations the atomic force microscopy was used. The above investigations allowed us to define the character of fatigue crack propagation and microstructural changes near the crack tip. It was found that crack propagation after fatigue tests in air is accompanied with plastic deformation; a high density of dislocations is observed at large distance from the crack. After fatigue tests performed during hydrogen charging the deformed zone containing high density of dislocations is narrow compared to that after fatigue tests in air. It means that hydrogenation leads to brittle character of fatigue crack propagation. In air, fatigue cracks propagate mostly transgranularly, whereas in hydrogen-generating environment the cracks have mixed transgranular/interfacial character. PMID:20500395

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-09-01

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

  10. Boron effects on creep rupture strength of W containing advanced ferritic creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Mito, N.; Hasegawa, Y. [Tohoku Univ., Sendai (Japan)

    2010-07-01

    The creep strength in ferritic creep resistant steels is increased by boron addition. However, the strengthening mechanisms have not yet been studied. This study clarifies the strengthening mechanism of 9% chromium steels with 10{proportional_to}100ppm boron and 0.5{proportional_to}2.0mass% tungsten in the laboratory. The strengthening effect of simultaneous addition of boron and tungsten was analyzed by hardenability, room-temperature strength and creep tests at 650 C. Changes in the microstructure as a result of the addition of boron and tungsten were also examined by optical microscope and transmission electron microscope (TEM). In addition, Alpha-ray Track Etching (ATE) method was used to detect the boron distribution and analyze the mechanisms change in the mechanical properties. Boron addition did not affect room-temperature strength, however, simultaneous addition of boron and tungsten increased room-temperature and high-temperature strength. According to ATE analysis, boron exists at the grain boundary. Therefore, synergistic effects of boron and tungsten on the creep strength suggest the tungsten precipitates stabilization by boron at the grain boundary. (orig.)

  11. Influence of combined thermomechanical treatment on impurity segregation in ferritic-martensitic and austenitic stainless steels

    Science.gov (United States)

    Ilyin, A. M.; Neustroev, V. S.; Shamardin, V. K.; Shestakov, V. P.; Tazhibaeva, I. L.; Krivchenkoa, V. A.

    2000-12-01

    In this study 13Cr2MoVNb ferritic-martensitic steel (FMS) and 16Cr15Ni3MoNb austenitic stainless steel (ASS) tensile specimens were subjected to standard heat treatments and divided into two groups. Specimens in group 1 (FMS only) were aged at 400°C in a stress free and in an elastically stressed state with a tensile load (100 MPa) then doped with hydrogen in an electrolytic cell. Specimens in group 2 were subjected to cold work (up to 10%) and exposed to short-time heating at 500° for 0.5 h. All specimens were fractured at room temperature in an Auger spectrometer and Auger analysis of the fracture surfaces was performed in situ after fracturing. A noticeable increase of N and P segregation levels and a widening of the depth distribution on the grain boundary facets were observed in the FMS after aging in the stressed state. Cold-worked FMS and ASS showed a ductile dimple mode of fracture, but relatively high levels of S, P and N were observed on the dimple surfaces. We consider the origin of such effects in terms of the stressed state and plastic-deformation-enhanced segregation.

  12. Steam oxidation behavior of high strength newly developed ferritic/martensitic steels at 650 C

    Energy Technology Data Exchange (ETDEWEB)

    Agueero, Alina; Gonzalez, Vanessa; Gutierrez, Marcos [Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz (Spain); Mayr, Peter [Massachusetts Inst. of Tech., Cambridge (United States). Dept. of Materials Science and Engineering; Spiradek-Hahn, Krystina [Austrian Institute of Technology GmbH (AIT), Seibersdorf (Austria)

    2010-07-01

    The efficiency of thermal power plants is currently limited by the strength and the oxidation resistance of the commercially available ferritic steels. The higher operating pressures and temperatures, essential to increase efficiency, impose important requirements on the materials from both the mechanical and chemical stability perspective. For instance, a creep rupture strength of 100 MPa after 100.000 hours at 650 C has been defined as the target for new steel development. Moreover, steam oxidation resistance is required as otherwise, at temperatures higher than 600 C, the resulting thick oxide scales will spall, causing blockage on bends as well as overheating of heat exchangers due to a thermal insulation effect, erosion of down-stream components and loss of cross-section in critical components such as blades. It has been shown that in general, a Cr wt. % higher than 9 is required for acceptable oxidation rates at 650 C, but such high Cr content results in a reduction of the creep strength. As an exception, several 9 wt. % steels developed by Abe which also containing Si and Mn, exhibit resistance to steam oxidation but only after having been subjected to a pre-oxidation heat treatment at 650 C for many hours. Substantial efforts are being carried out in Europe, North America and Japan attempting to design and produce steels with these properties. The steam oxidation behavior of high strength new alloys, such as CB2 and FT7 steels developed within the frame of European COST Actions 522 and 536, as well as of a NIMS developed B containing 9Cr3W3CoVNb (NPM) martensitic steel, was studied by exposing these materials to pure flowing steam in the laboratory for periods of time in excess of 10,000 h at 650 C. CB2 and FT7 have similar creep strength to P92 whereas NPM reaches 21,000 h at 100 MPa exceeding by far that of P92 according to the ECCC values. (orig.)

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

    International Nuclear Information System (INIS)

    Full text of publication follows: Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems as it has been developed based on massive industrial experience of ferritic/martensitic steel replacing Mo and Nb of high chromium heat resistant martensitic steels (such as modified 9Cr-1Mo) with W and Ta, respectively. As one of RAFMS, F82H, which has been developed and studied in Japan, is designed with emphasis on high temperature property and weldablility, and was provided and evaluated in various countries as a part of the collaboration of IEA fusion materials development. Although F82H is the well perceived RAFM as ITER Test Blanket Module (TBM) structural material, the weldability was proved though TIG, EB and YAG laser weld tests using only 15 and 25 mm thickness plate. In order to reduce the welding distortion, the residual stress and the area of the heat affected zone, it is necessary to decrease the total heat input under the welding. Recently, as a result of R and D efforts about the sources of laser beam, a high-power fiber laser beam has been developed as one of the desirable heat sources for high-speed and deep-penetration welding. Since the power density of the fiber laser beam is very large, it is possible to increase the welding speed more than 10 m/min. So, in this study, the weldability of 1.5 mm thickness F82H plate and pipe was examined by using a ultra power density fiber laser, in order to reveal the excellent weldability of F82H. As a basic study of the butt welding between 1.5 mm plate and 1.5 mm thickness pipe with 11 mm outer diameter, the focus position, the beam position and the laser power were varied using 25 mm square plate and 25 mm length pipe. Then, by using the fiber laser with 1.1 MW/mm2 peak power density under the appropriate welding condition obtained from the basic study, a full penetrated weld bead with narrow width was formed in the butt welding

  14. Gas porosity evolution and ion-implanted helium behavior in reactor ferritic/martensitic and austenitic steels

    International Nuclear Information System (INIS)

    The peculiarities of gas porosity formation and helium retention and release in reactor ferritic/martensitic EP-450 and EP-450-ODS and austenitic ChS-68 steels are investigated by transmission electron microscopy and helium thermal desorption spectrometry (HTDS). The samples were irradiated by 40 keV He+ ions up to a fluence of 5 · 1020 m−2 at 293 and 923 K. An nonuniform distribution of helium bubbles and high-level gas swelling in ferritic/martensitic steels were found at high-temperature helium implantation. The same irradiation conditions result in formation of uniformly distributed helium bubbles and low-level swelling in ChS-68 steel. Temperature range of helium release from EP-450-ODS steel was considerably wider in comparison to HTDS-spectra of the EP-450 steel. A considerable quantity of helium is released from ODS steel in the high-temperature range after the main peak of the HTDS-spectrum

  15. Oxidation behavior of ferritic/martensitic steels in stagnant liquid LBE saturated by oxygen at 600 °C

    Science.gov (United States)

    Shi, Quanqiang; Liu, Jian; Luan, He; Yang, Zhenguo; Wang, Wei; Yan, Wei; Shan, Yiyin; Yang, Ke

    2015-02-01

    Ferritic/martensitic (F/M) steels are primary candidates for application as cladding and structural materials in the Generation IV Nuclear Reactor, especially accelerator driven sub-critical system (ADS). The compatibility of F/M steels with liquid lead-bismuth eutectic (LBE) is a critical issue for development of ADS using liquid LBE as the coolant. In this work, the corrosion tests of two F/M steels, including a novel 9-12 Cr modified F/M steel named SIMP steel and a commercial T91 steel, were conducted in the static oxygen-saturated liquid LBE at 600 °C up to 1000 h, the microstructure of the oxide scale formed on these two steels was analyzed, the relationship between the microstructure and the oxidation behavior was studied, and the reason why the SIMP steel showed better oxidation resistance compared to T91 steel was analyzed. The results of this study confirmed that the oxidation behavior of the F/M steels in liquid metals is influenced by their alloying elements and microstructures.

  16. Effect of nano-sized precipitates on the crystallography of ferrite in high-strength strip steel

    Institute of Scientific and Technical Information of China (English)

    Jing-jing Yang; Run Wu; Wen Liang; Meng-xia Tang

    2014-01-01

    For strip steel with the thickness of 1.6 mm, the yield and tensile strengths as high as 760 and 850 MPa, respectively, were achieved using the compact strip production technology. Precipitates in the steel were characterized by scanning and transmission electron microscopy to elucidate the strengthening mechanism. In addition, intragranular misorientation, Kernel average misorientation, and stored energy were measured using electron backscatter diffraction for crystallographic analysis of ferrite grains containing precipitates and their neighbors without precipitates. It is found that precipitates in specimens primarily consist of TiC and Ti4C2S2. Ferrite grains containing pre-cipitates exhibit the high Taylor factor as well as the crystallographic orientations with{012},{011},{112}, or{221}plane parallel to the rolling plane. Compared with the intragranular orientation of adjoining grains, the intragranular misorientation of grains containing precipi-tates fluctuates more frequently and more mildly as a function of distance. Moreover, the precipitates can induce ferrite grains to store a rela-tively large amount of energy. These results suggest that a correlation exists between precipitation in ferrite grains and grain crystallographic properties.

  17. Effect of nano-sized precipitates on the crystallography of ferrite in high-strength strip steel

    Science.gov (United States)

    Yang, Jing-jing; Wu, Run; Liang, Wen; Tang, Meng-xia

    2014-05-01

    For strip steel with the thickness of 1.6 mm, the yield and tensile strengths as high as 760 and 850 MPa, respectively, were achieved using the compact strip production technology. Precipitates in the steel were characterized by scanning and transmission electron microscopy to elucidate the strengthening mechanism. In addition, intragranular misorientation, Kernel average misorientation, and stored energy were measured using electron backscatter diffraction for crystallographic analysis of ferrite grains containing precipitates and their neighbors without precipitates. It is found that precipitates in specimens primarily consist of TiC and Ti4C2S2. Ferrite grains containing precipitates exhibit the high Taylor factor as well as the crystallographic orientations with {012}, {011}, {112}, or {221} plane parallel to the rolling plane. Compared with the intragranular orientation of adjoining grains, the intragranular misorientation of grains containing precipitates fluctuates more frequently and more mildly as a function of distance. Moreover, the precipitates can induce ferrite grains to store a relatively large amount of energy. These results suggest that a correlation exists between precipitation in ferrite grains and grain crystallographic properties.

  18. Multi-stage Modeling of Lüders Elongation and Work-Hardening Behaviors of Ferrite Steels Under Tension

    Science.gov (United States)

    Zhang, Zhongyang; Liao, Yiliang

    2016-04-01

    For structural and engineering steels, accurate modeling of stress-strain relation of ferrite phase is of particular importance, since the modeling results could benefit new material system design and process-microstructure-property analysis. Several modeling efforts have been made to achieve this target. However, few efforts have been put on the Lüders elongation behavior of ferrite. As a result, the modeling results from proposed models do not match well with experimental data, particularly at a relatively low-strain range. Furthermore, without the consideration of yield point elongation due to the formation of Lüders bands, additional calibration parameters are required to capture the stress level of stress-strain curves. In this work, a multi-stage model is developed to predict the stress-strain relation of ferrite phase steel under room temperature tension. This model is capable of capturing the grain size effect on both Lüders elongation and work-hardening behaviors of ferrite. The modeling results are extensively validated by experimental data.

  19. Formation and coalescence of strain localized regions in ferrite phase of DP600 steels under uniaxial tensile deformation

    Energy Technology Data Exchange (ETDEWEB)

    Alaie, A., E-mail: amir_alaie@yahoo.com [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Kadkhodapour, J. [Department of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of); Institute for Materials Testing, Materials Science and Strength of Materials (IMWF), University of Stuttgart, Stuttgart (Germany); Ziaei Rad, S. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Asadi Asadabad, M. [Materials Research School, Isfahan (Iran, Islamic Republic of); Schmauder, S. [Institute for Materials Testing, Materials Science and Strength of Materials (IMWF), University of Stuttgart, Stuttgart (Germany)

    2015-01-19

    In this study the key factors in the creation and coalescence of strain localization regions in dual-phase steels were investigated. An in-situ tensile setup was used to follow the microscopic deformation of ferrite phase inside the microstructure of DP600 steel. The test was continued until the specimen was very close to final failure. The captured scanning electron microscopy (SEM) micrographs enabled us to directly observe the evolution of deformation bands as a contour of strain distribution in the ferrite matrix. The image processing method was used to quantify the ferrite microscopic strains; the obtained strain maps were superimposed onto the SEM micrographs. The results revealed important deformational characteristics of the microstructure at the microscopic level. It was observed that despite the formation of slip bands inside the large grains during the early stages of deformation, the large ferrite grains did not contribute to the formation of high-strain bands until the final stages of severe necking. The behavior of voids and initial defects inside the localization bands was also studied. In the final stages of deformation, cracks were observed to preferentially propagate in the direction of local deformation bands and to coalescence with each other to form the final failure lines in the microstructure. It was observed that in the final stages of deformation, the defects or voids outside the deformation bands do not contribute to the final failure mechanisms and could be considered to be of minor importance.

  20. Formation and coalescence of strain localized regions in ferrite phase of DP600 steels under uniaxial tensile deformation

    International Nuclear Information System (INIS)

    In this study the key factors in the creation and coalescence of strain localization regions in dual-phase steels were investigated. An in-situ tensile setup was used to follow the microscopic deformation of ferrite phase inside the microstructure of DP600 steel. The test was continued until the specimen was very close to final failure. The captured scanning electron microscopy (SEM) micrographs enabled us to directly observe the evolution of deformation bands as a contour of strain distribution in the ferrite matrix. The image processing method was used to quantify the ferrite microscopic strains; the obtained strain maps were superimposed onto the SEM micrographs. The results revealed important deformational characteristics of the microstructure at the microscopic level. It was observed that despite the formation of slip bands inside the large grains during the early stages of deformation, the large ferrite grains did not contribute to the formation of high-strain bands until the final stages of severe necking. The behavior of voids and initial defects inside the localization bands was also studied. In the final stages of deformation, cracks were observed to preferentially propagate in the direction of local deformation bands and to coalescence with each other to form the final failure lines in the microstructure. It was observed that in the final stages of deformation, the defects or voids outside the deformation bands do not contribute to the final failure mechanisms and could be considered to be of minor importance

  1. Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

    Science.gov (United States)

    Verma, Jagesvar; Taiwade, Ravindra V.

    2016-09-01

    This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

  2. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    International Nuclear Information System (INIS)

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested

  3. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    Energy Technology Data Exchange (ETDEWEB)

    Debehets, Jolien, E-mail: jolien.debehets@mtm.kuleuven.be [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Tacq, Jeroen [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Favache, Audrey; Jacques, Pascal [Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2 L5.02.02, 1348 Louvain-la-Neuve (Belgium); Seo, Jin Won; Verlinden, Bert; Seefeldt, Marc [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium)

    2014-10-20

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested.

  4. Thermal treatments effect on the austenite-ferrite equilibrium in a duplex stainless steel weld beads; Effet des traitements thermiques sur l equilibre austenite - ferrite dans un cordon de soudure en acier inoxydable duplex

    Energy Technology Data Exchange (ETDEWEB)

    Belkessa, Brahim; Badji, Riad; Bettahar, Kheireddine; Maza, Halim [Division de la Metallurgie et Mecanique. Centre de Recherche Scientifique et Technique en Soudage et Controle. B.P 64, Route de Dely Ibrahim, Cheraga, Alger (Algeria)

    2006-07-01

    Heat treatments in the temperature range between 800 to 1200 C, with a keeping at high temperature of 60 min, followed by a water quenching at 20 C, have been carried out on austeno-ferritic stainless steel welds (of type SAF 2205-UNS S31803). The heat treatments carried out at temperatures below 1000 C have modified the structure of the duplex stainless steel 2205 in inducing the formation of precipitates, identified by X-ray diffraction as being the intermetallic compound {sigma} and the chromium carbides M{sub 23}C{sub 6}. The treatments applied to temperatures superior to 1000 C shift the {delta}-{gamma} equilibrium towards the {delta} phase. Indeed, the increase of the ferrite rate with the treatment temperature is approximately linear. The ferrite rates are higher in the heat-affected zone, which has been submitted to a ferritizing due to the welding thermal effects. (O.M.)

  5. Effect of mechanical alloying atmosphere on the microstructure and Charpy impact properties of an ODS ferritic steel

    International Nuclear Information System (INIS)

    Two types of oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-14Cr-2W-0.3Ti-0.3Y2O3 (in weight percent), have been produced by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y2O3 particles either in argon atmosphere or in hydrogen atmosphere, degassing at various temperatures, and compacting the mechanically alloyed powders by hot isostatic pressing. It was found in particular that mechanical alloying in hydrogen yields a significant reduction in oxygen content in the materials, a lower dislocation density, and a strong improvement in the fast fracture properties of the ODS ferritic steels, as measured by Charpy impact tests.

  6. An integrated computer model with applications for austenite-to-ferrite transformation during hot deformation of Nb-microalloyed steels

    Science.gov (United States)

    Majta, Janusz; Pietrzyk, Maciej; Zurek, Anna K.; Cola, Mark; Hochanadel, Pat

    2002-05-01

    This work presents an austenite decomposition model, based on the thermodynamics of the system and diffusion-controlled nucleation theory, to predict the evolution of microstructure during hot working of niobium-microalloyed steels. The differences in microstructural development of hotdeformed microalloyed steel in the single-phase austenite and two-phase (austenite + ferrite) regions have been effectively described using an integrated computer modeling process. The complete model presented here takes into account the kinetics of recrystallization, recrystallized austenite grain size, precipitation, phase transformation, and the resulting ferrite structure. After considering existing austenite decomposition models, we decided that the method adopted in the present work relies on isothermal transformation kinetics and the principle-of-additivity rule. The thermomechanical part of the modeling process was carried out using the finite-element method. Experimental results at different temperatures, strain rates, and strain levels were obtained using a Gleeble thermomechanical simulator. A comparison of results of the model with experiments shows good agreement.

  7. Pros and cons of nickel- and boron-doping to study helium effects in ferritic/martensitic steels

    Science.gov (United States)

    Hashimoto, N.; Klueh, R. L.; Shiba, K.

    2002-12-01

    In the absence of a 14 MeV neutron source, the effect of helium on structural materials for fusion must be simulated using fission reactors. Helium effects in ferritic/martensitic steels have been studied by adding nickel and boron and irradiating in a mixed-spectrum reactor. Although the nickel- and boron-doping techniques have limitations and difficulties to estimate helium effects on the ferritic/martensitic steels, past irradiation experiments using these techniques have demonstrated similar effects on the swelling and Charpy impact properties that are indicative of a helium effect. Although both techniques have disadvantages, it should be possible to plan experiments using the nickel- and boron-doping techniques to develop an understanding of the effects of helium on mechanical properties.

  8. Cyclic plasticity of an austenitic-ferritic stainless steel under biaxial non proportional loading

    International Nuclear Information System (INIS)

    Austenitic-ferritic stainless steels are supplied since about 30 years only, so they are yet not well-known. Their behaviour in cyclic plasticity was studied under uniaxial loading but not under multiaxial loading, whereas only a thorough knowledge of the phenomena influencing the mechanical behaviour of a material enables to simulate and predict accurately its behaviour in a structure. This work aims to study and model the behaviour of a duplex stainless steel under cyclic biaxial loading. A three step method was adopted. A set of tension-torsion tests on tubular specimen was first defined. We studied the equivalence between loading directions, and then the influence of loading path and loading history on the stress response of the material. Results showed that duplex stainless steel shows an extra-hardening under non proportional loading and that its behaviour depends on previous loading. Then, in order to analyse the results obtained during this first experimental stage, the yield surface was measured at different times during cyclic loading of the same kind. A very small plastic strain offset (2*10-5) was used in order not to disturb the yield surface measured. The alteration of isotropic and kinematic hardening variables were deduced from these measures. Finally, three phenomenological constitutive laws were identified with the experimental set. We focused our interest on the simulation of stabilized stress levels and on the simulation of the cyclic hardening/softening behaviour. The comparison between experimental and numerical results enabled the testing of the relevance of these models. (authors)

  9. Effect of water depth on the underwater wet welding of ferritic steels using austenitic Ni-based alloy electrodes.

    OpenAIRE

    Sheakley, Brian J.

    2000-01-01

    Underwater welding using shielded metal arc welding (SMAW) on US naval Vessels is very attractive because of the ability to effect repairs without costly dry dock expenses. In the past the primary problems with underwater wet weldments on steels utilizing SMAW with ferritic electrodes, were underbead cracking in the heat affected zone (HAZ), slag inclusions, oxide inclusions, and porosity. To avoid underbead cracking three weld samples were made using an austenitic nickel weld metal with an O...

  10. Analysis of stress-induced Burgers vector anisotropy in pressurized tube specimens of irradiated ferritic-martensitic steel: JLF-1

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States); Shibayama, T. [Univ. of Hokkaido, Oarai, Ibaraki (Japan). Inst. for Materials Research

    1998-09-01

    A procedure for determining the Burgers vector anisotropy in irradiated ferritic steels allowing identification of all a<100> and all a/2<111> dislocations in a region of interest is applied to a pressurized tube specimen of JLF-1 irradiated at 430 C to 14.3 {times} 10{sup 22} n/cm{sup 2} (E > 0.1 MeV) or 61 dpa. Analysis of micrographs indicates large anisotropy in Burgers vector populations develop during irradiation creep.

  11. The Influence of Shielding Gas and Heat Input on the Mechanical Properties of Laser Welds in Ferritic Stainless Steel

    Science.gov (United States)

    Keskitalo, M.; Sundqvist, J.; Mäntyjärvi, K.; Powell, J.; Kaplan, A. F. H.

    Laser welding of ferritic steel in normal atmosphere gives rise to weld embrittlement and poor formability. This paper demonstrates that the addition of an argon gas shield to the welding process results in tough, formable welds. Post weld heat treatment and microscopic analysis has suggested that the poor ductility of welds produced without a gas shield is, to some extent, the result of the presence of oxides in the weld metal.

  12. Effect of Austenization Temperature on the Microstructure and Strength of 9% and 12% Cr Ferritic-Martensitic Steels

    Energy Technology Data Exchange (ETDEWEB)

    Terry C. Totemeier

    2004-10-01

    The effect of reduced-temperature austenization on the microstructure and strength of two ferritic-martensitic steels was studied. Prototypic 9% and 12% Cr steels, grade 91 (9Cr-1MoVNb) and type 422 stainless (12Cr-1MoVW), respectively, were austenized at 925°C and 1050°C and tempered at 760°C. The reduced austenization temperature was intended to simulate potential inadequate austenization during field construction of large structures and also the thermal cycle experienced in the Type IV region of weld heat affected zones (HAZ). The microstructure, tensile behavior, and creep strength were characterized for both steels treated at each condition. The reduced austenization temperature resulted in general coarsening of carbides in both steels and polygonization of the tempered martensite structure in type 422. For this steel, a marked reduction in microhardness was observed, while there was little change in microhardness for grade 91. Slight reductions in tensile strength were observed for both steels at room temperature and elevated temperatures of 450 and 550°C. The strength reduction was greater for type 422 than for grade 91. At 650°C the tensile strength reduction was minimal for both steels. Marked reductions in creep rupture lives were observed for both steels at 650°C; the reductions were less at 600°C and minimal at 550°C. Overall, the higher Cr content steel was observed to be more sensitive to variations in heat treatment conditions.

  13. Effect of martensite morphology and volume fraction on strain hardening and fracture behavior of martensite–ferrite dual phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiecen [State Key Laboratory of Rolling and Automation, Northeastern University, 3-11 Wenhua Road, Shenyang 110819 (China); Di, Hongshuang, E-mail: dhshuang@mail.neu.edu.cn [State Key Laboratory of Rolling and Automation, Northeastern University, 3-11 Wenhua Road, Shenyang 110819 (China); Deng, Yonggang [State Key Laboratory of Rolling and Automation, Northeastern University, 3-11 Wenhua Road, Shenyang 110819 (China); Misra, R.D.K. [Department of Metallurgical and Materials Engineering and Center for Structural and Functional Materials Research and Innovation, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States)

    2015-03-11

    Two different morphologies of martensite in dual phase (DP) steel were obtained using two different processing routes. In one case, intermediate quenching (IQ) was adapted, where DP steel was water-quenched to obtain martensite phase, followed by inter-critical annealing. In the second case, the steel was cold rolled, followed by inter-critical annealing (CR-IA). For IQ and CR-IA steels, the inter-critical temperatures varied from 750 °C to 850 °C to obtain different volume fractions of martensite. An understanding of structure–property was obtained using a combination of scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile tests. It was observed that fibrous martensite presented in IQ samples, gradually transformed to blocky martensite with increase in inter-critical temperature, resembling the CR-IA steels. The fibrous martensite encouraged martensite cracking, however, the martensite cracking was dramatically decreased in the IQ samples with increase in martensite fraction. The strain hardening behavior studied using the differential C–J model indicated multistage depending on the fraction of martensite. The low volume fraction of martensite in the DP steel provided high ductility–toughness combination and improved strain hardening ability due to the presence of soft ferrite phase in DP steel. Fibrous martensite in DP steel resulted in less strain hardening than blocky martensite, prior to exceeding a threshold volume fraction. The threshold value was significantly smaller for DP steel with blocky martensite.

  14. Effect of martensite morphology and volume fraction on strain hardening and fracture behavior of martensite–ferrite dual phase steel

    International Nuclear Information System (INIS)

    Two different morphologies of martensite in dual phase (DP) steel were obtained using two different processing routes. In one case, intermediate quenching (IQ) was adapted, where DP steel was water-quenched to obtain martensite phase, followed by inter-critical annealing. In the second case, the steel was cold rolled, followed by inter-critical annealing (CR-IA). For IQ and CR-IA steels, the inter-critical temperatures varied from 750 °C to 850 °C to obtain different volume fractions of martensite. An understanding of structure–property was obtained using a combination of scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile tests. It was observed that fibrous martensite presented in IQ samples, gradually transformed to blocky martensite with increase in inter-critical temperature, resembling the CR-IA steels. The fibrous martensite encouraged martensite cracking, however, the martensite cracking was dramatically decreased in the IQ samples with increase in martensite fraction. The strain hardening behavior studied using the differential C–J model indicated multistage depending on the fraction of martensite. The low volume fraction of martensite in the DP steel provided high ductility–toughness combination and improved strain hardening ability due to the presence of soft ferrite phase in DP steel. Fibrous martensite in DP steel resulted in less strain hardening than blocky martensite, prior to exceeding a threshold volume fraction. The threshold value was significantly smaller for DP steel with blocky martensite

  15. Microstructure and mechanical properties of friction stir welded 18Cr–2Mo ferritic stainless steel thick plate

    International Nuclear Information System (INIS)

    Highlights: • We focus on friction stir welding of 18Cr–2Mo ferritic stainless steel thick plate. • We produce high-quality joints with special tool and optimised welding parameters. • We compare microstructure and mechanical properties of steel and joint. • Friction stir welding is a method that can maintain the properties of joint. - Abstract: In this study, microstructure and mechanical properties of a friction stir welded 18Cr–2Mo ferritic stainless steel thick plate were investigated. The 5.4 mm thick plates with excellent properties were welded at a constant rotational speed and a changeable welding speed using a composite tool featuring a chosen volume fraction of cubic boron nitride (cBN) in a W–Re matrix. The high-quality welds were successfully produced with optimised welding parameters, and studied by means of optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and standard hardness and impact toughness testing. The results show that microstructure and mechanical properties of the joints are affected greatly, which is mainly related to the remarkably fine-grained microstructure of equiaxed ferrite that is observed in the friction stir welded joint. Meanwhile, the ratios of low-angle grain boundary in the stir zone regions significantly increase, and the texture turns strong. Compared with the base material, mechanical properties of the joint are maintained in a comparatively high level

  16. The segregation behavior of manganese and silicon at the coherent interfaces of copper precipitates in ferritic steels

    International Nuclear Information System (INIS)

    We have performed first-principles calculations to study the segregation behavior of Mn and Si at the interfaces of Cu precipitates in ferritic steels. We find that both the segregation energies of substitutional Mn and Si at the interfaces of the Cu precipitates are negligible. However, the energetics indicate that the self-interstitial dumbbells containing Mn or Si (Mn@SI or Si@SI) at the coherent interface of Fe/Cu is more favorable than the Mn@SI or Si@SI embodied in pure Fe or Cu phases, respectively. The relative stability of the substitutional defects, Mn@SI, Si@SI, and pure Fe self-interstitial (SI) dumbbells can well account for the difference in segregation behavior of Mn and Si at Cu precipitates in the ferritic steels under the condition of irradiation and thermal aging. Furthermore, we find that both the Mn@SI and Si@SI segregation result an embrittlement trend on the interfaces of Cu precipitates in ferritic steels

  17. Generalization of the existing relations between microstructure and yield stress from ferrite-pearlite to high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Iza-Mendia, A., E-mail: aiza@ceit.es [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain); Gutierrez, I. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain)

    2013-01-20

    A series of available equations allows the yield and the tensile strength of low carbon ferrite-pearlite microstructures to be expressed as a function of the optical grain size, steel composition and interstitials in solution. Over the years, as the complexity of steel microstructures has increased, some additional terms have been added to account for precipitation and forest dislocation contributions. In theory, this opens the door for an extension of these equations to bainitic microstructures. Nevertheless, there is a series of difficulties that needs to be overcome in order to improve prediction accuracy. In the present work, different microstructures (ferrite-pearlite, bainite, quenched, and quenched and tempered) were produced and tension tested in a C-Mn-Nb steel. Optical microscopy and EBSD (Electron Back Scattered Diffraction) were applied and the results were compared as a function of the tolerance angle. Based on this work, an adaptation to Pickering's equation is proposed, including its extension to other microstructures rather than ferrite-pearlite.

  18. Parametric study of irradiation effects on the ductile damage and flow stress behavior in ferritic-martensitic steels

    Science.gov (United States)

    Chakraborty, Pritam; Biner, S. Bulent

    2015-10-01

    Ferritic-martensitic steels are currently being considered as structural materials in fusion and Gen-IV nuclear reactors. These materials are expected to experience high dose radiation, which can increase their ductile to brittle transition temperature and susceptibility to failure during operation. Hence, to estimate the safe operational life of the reactors, precise evaluation of the ductile to brittle transition temperatures of ferritic-martensitic steels is necessary. Owing to the scarcity of irradiated samples, particularly at high dose levels, micro-mechanistic models are being employed to predict the shifts in the ductile to brittle transition temperatures. These models consider the ductile damage evolution, in the form of nucleation, growth and coalescence of voids; and the brittle fracture, in the form of probabilistic cleavage initiation, to estimate the influence of irradiation on the ductile to brittle transition temperature. However, the assessment of irradiation dependent material parameters is challenging and influences the accuracy of these models. In the present study, the effects of irradiation on the overall flow stress and ductile damage behavior of two ferritic-martensitic steels is parametrically investigated. The results indicate that the ductile damage model parameters are mostly insensitive to irradiation levels at higher dose levels though the resulting flow stress behavior varies significantly.

  19. Development of ultrafine ferritic sheaves/plates in SAE 52100 steel for enhancement of strength by controlled thermomechanical processing

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, J. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, W.B. 721 302 (India); Scientific Services and Research and Development, Tata Steel, Jamshedpur 831 001, Jharkhand (India); Manna, I., E-mail: imanna@metal.iitkgp.ernet.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, W.B. 721 302 (India); Central Glass and Ceramic Research Institute (CGCRI), Council of Scientific and Industrial Research (CSIR), 196 Raja S C Mullick Road, Jadavpur, Kolkata 700032 (India)

    2012-06-30

    Highlights: Black-Right-Pointing-Pointer Ultrafine bainite + martensite duplex microstructure developed in SAE 52100 steel. Black-Right-Pointing-Pointer Thermomechanical processing modifies size + morphology of bainitic ferrite. Black-Right-Pointing-Pointer Processing involves hot deformation prior to/during/after austenitizing. Black-Right-Pointing-Pointer Significant improvement in mechanical strength achieved. Black-Right-Pointing-Pointer Similar study on high carbon, low alloy steel not reported in the literature. - Abstract: The present study attempts to tailor the size, morphology and distribution of the ferrite needles/sheaves by thermomechanical processing and develop an ultrafine ferrite + martensite duplex microstructure for enhancement of strength and toughness in SAE 52100 steel. The thermo-mechanical routine included 5% hot deformation before, during or after austenitizing at 950 Degree-Sign C for 15 min followed by austempering at 270 Degree-Sign C for 30 min and subsequent water quenching to room temperature. Optical/electron microscopy along with X-ray diffraction was used to quantitatively monitor the size, morphology and distribution of the phase or phase aggregate. Significant improvement in nanohardness, wear resistance and elastic modulus and was observed in samples subjected to thermomechanical processing, as compared to that following the same austenitizing and austempering routine without hot deformation at any stage. However, improvement in the bulk mechanical property due to the present thermo-mechanical is lower than that obtained in our earlier study comprising cold deformation prior to austenitizing and austempering.

  20. Development of ultrafine ferritic sheaves/plates in SAE 52100 steel for enhancement of strength by controlled thermomechanical processing

    International Nuclear Information System (INIS)

    Highlights: ► Ultrafine bainite + martensite duplex microstructure developed in SAE 52100 steel. ► Thermomechanical processing modifies size + morphology of bainitic ferrite. ► Processing involves hot deformation prior to/during/after austenitizing. ► Significant improvement in mechanical strength achieved. ► Similar study on high carbon, low alloy steel not reported in the literature. - Abstract: The present study attempts to tailor the size, morphology and distribution of the ferrite needles/sheaves by thermomechanical processing and develop an ultrafine ferrite + martensite duplex microstructure for enhancement of strength and toughness in SAE 52100 steel. The thermo-mechanical routine included 5% hot deformation before, during or after austenitizing at 950 °C for 15 min followed by austempering at 270 °C for 30 min and subsequent water quenching to room temperature. Optical/electron microscopy along with X-ray diffraction was used to quantitatively monitor the size, morphology and distribution of the phase or phase aggregate. Significant improvement in nanohardness, wear resistance and elastic modulus and was observed in samples subjected to thermomechanical processing, as compared to that following the same austenitizing and austempering routine without hot deformation at any stage. However, improvement in the bulk mechanical property due to the present thermo-mechanical is lower than that obtained in our earlier study comprising cold deformation prior to austenitizing and austempering.

  1. Microstructural Variations Across a Dissimilar 316L Austenitic: 9Cr Reduced Activation Ferritic Martensitic Steel Weld Joint

    Science.gov (United States)

    Thomas Paul, V.; Karthikeyan, T.; Dasgupta, Arup; Sudha, C.; Hajra, R. N.; Albert, S. K.; Saroja, S.; Jayakumar, T.

    2016-03-01

    This paper discuss the microstructural variations across a dissimilar weld joint between SS316 and 9Cr-RAFM steel and its modifications on post weld heat treatments (PWHT). Detailed characterization showed a mixed microstructure of austenite and martensite in the weld which is in agreement with the phases predicted using Schaeffler diagram based on composition measurements. The presence of very low volume fraction of δ-ferrite in SS316L has been identified employing state of the art electron back-scattered diffraction technique. PWHT of the ferritic steel did not reduce the hardness in the weld metal. Thermal exposure at 973 K (700 °C) showed a progressive reduction in hardness of weld joint with duration of treatment except in austenitic base metal. However, diffusion annealing at 1073 K (800 °C) for 100 hours resulted in an unexpected increase in hardness of weld metal, which is a manifestation of the dilution effects and enrichment of Ni on the transformation characteristics of the weld zone. Migration of carbon from ferritic steel aided the precipitation of fine carbides in the austenitic base metal on annealing at 973 K (700 °C); but enhanced diffusion at 1073 K (880 °C) resulted in coarsening of carbides and thereby reduction of hardness.

  2. Fractographic examination of reduced activation ferritic/martensitic steel charpy specimens irradiated to 30 dpa at 370{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S.; Hamilton, M.L. [Pacific Northwest National Lab., Richland, WA (United States); Schubert, L.E. [Univ. of Missouri, Rolla, MO (United States)

    1996-10-01

    Fractographic examinations are reported for a series of reduced activation ferritic/Martensitic steel Charpy impact specimens tested following irradiation to 30 dpa at 370{degrees}C in FFTF. One-third size specimens of six low activation steels developed for potential application as structural materials in fusion reactors were examined. A shift in brittle fracture appearance from cleavage to grain boundary failure was noted with increasing manganese content. The results are interpreted in light of transmutation induced composition changes in a fusion environment.

  3. Effects of Annealing Treatment Prior to Cold Rolling on Delayed Fracture Properties in Ferrite-Austenite Duplex Lightweight Steels

    Science.gov (United States)

    Sohn, Seok Su; Song, Hyejin; Kim, Jung Gi; Kwak, Jai-Hyun; Kim, Hyoung Seop; Lee, Sunghak

    2016-02-01

    Tensile properties of recently developed automotive high-strength steels containing about 10 wt pct of Mn and Al are superior to other conventional steels, but the active commercialization has been postponed because they are often subjected to cracking during formation or to the delayed fracture after formation. Here, the delayed fracture behavior of a ferrite-austenite duplex lightweight steel whose microstructure was modified by a batch annealing treatment at 1023 K (750 °C) prior to cold rolling was examined by HCl immersion tests of cup specimens, and was compared with that of an unmodified steel. After the batch annealing, band structures were almost decomposed as strong textures of {100} α-fibers and {111} γ-fibers were considerably dissolved, while ferrite grains were refined. The steel cup specimen having this modified microstructure was not cracked when immersed in an HCl solution for 18 days, whereas the specimen having unmodified microstructure underwent the delayed fracture within 1 day. This time delayed fracture was more critically affected by difference in deformation characteristics such as martensitic transformation and deformation inhomogeneity induced from concentration of residual stress or plastic strain, rather than the difference in initial microstructures. The present work gives a promise for automotive applications requiring excellent mechanical and delayed fracture properties as well as reduced specific weight.

  4. Effect of the damage by radiation on the reference temperature T0 of ferritic steel

    International Nuclear Information System (INIS)

    Presently work studies the effect that produces the irradiation in ferritic steels, on the reference temperature T0 (intrinsic characteristic of the fracture tenacity in the area of ductile-fragile transition), applying the approach of the Master curve that is based on the norm Astm E-1921. For it it was elaborated a methodology and procedure for test tubes type Charpy according to the standard before mentioned. Due to the ferritic steels are used mainly in pressure vessels to the reactor (RPV) of nuclear power plants; in the samples it was simulated the effect of the damage for irradiation through a thermal treatment that induced the precipitation of the carbides and sulfurs in the limits of grain (one of the modifications suffered in the irradiated materials); it was made a comparison later with material samples in initial state (without thermal treatment), used as witness sample, by means of assays of fracture mechanics, specifically flexion in three points; this way with it to observe the effect of the damage for irradiation in the reference temperature (T0). This temperature (T0) it is a very important parameter in the mechanical property of the material called fracture tenacity; which at the moment gives the rule for the verification of structural integrity of the RPV. As a result of this it was observed an increase in the reference temperature in the material in fragilezed state with respect to the initial state of 31.75 C. They were carried out metallographic analysis and fractographs of the assayed surface finding carbide inclusions and sulfurs that in theory of the Master Curve they are initiators of cracks and of a possible catastrophic flaw of the material. At the moment the Division of Scientific Investigation of the ININ is carrying out activities in the Nucleo electric Central of Laguna Verde (CNLV) related with the program of surveillance of the materials of the vessel of the unit 2, as well as projects of structural integrity financed by the

  5. Evaluation of Charpy impact properties and fracture toughness for irradiated ferritic steels (4)

    International Nuclear Information System (INIS)

    In order to evaluate the radiation-induced shift of fracture toughness from Charpy impact test results for miniaturized specimens, all of the Charpy impact data on high-strength ferritic steels developed by JNC were examined on the basis of the recent progress on the Charpy impact and fracture toughness test methods. Main results obtained are as follows. 1. The radiation-induced shift of fracture toughness is characterized by the shift of the reference fracture toughness temperature, ΔT100, where T100 is the temperature at which the fracture toughness value is 100MPa√ m. ΔT100 is approximately equal to the radiation-induced shift of Charpy DBTT at 41J (ΔT41). Therefore, ΔT100 can be estimated by determining ΔT41 from miniaturized Charpy specimen data. 2. The value of T41 for miniaturized specimens, T41M, can be determined as the test temperature where the absorbed energy is equal to 41/αx[(Bb)3/2F/(Bb)3/2M]. Here, B is the specimen thickness, b is the ligament size and αx[(Bb)3/2F/(Bb)3/2M] is the normalization factor to get the upper shelf energy of full size specimens, USEF, from the mini-size USEM. The values of α is larger than 0.65, depending on the USE of the material. It is also shown that the fracture volume of (Bb)3/2 is more valid than that of Bb2. 3. The following relationship appears to hold between T41F and T41M. T41F - T41M=M=98 - 15.1xln(Bb)3/2, where M is the specimen size correction factor. M also depends on notch geometry and its dependence becomes large with decreasing specimen size. This indicates that the value of T41F can be estimated from T41M by choosing suitable notch geometry. 4. The radiation-induced shift of T41F, ΔT41F, is approximately equal to ΔT41M. This indicates that the estimate of ΔT100 can be made from ΔT41M. 5. For all of the miniaturized Charpy specimen data on high-strength ferritic steels that were irradiated in JOYO and tested at Tohoku University, the values of USEF, T41F, ΔT41F and ΔT100 were successfully

  6. Fracture mechanisms in dual phase steels based on the acicular ferrite + martensite/austenite microstructure

    Science.gov (United States)

    Poruks, Peter

    The fracture mechanisms of low carbon microalloyed plate steels based on the acicular ferrite + marten site/austenite microstructure (AF + M/A) are investigated. The final microstructure consists of a dispersed phase of submicron equi-axed martensite particles with a bainitic ferrite matrix. A series of plates with M/A volume fractions of 0.076--0.179 are studied. Brittle fracture is investigated by Instrumented Charpy impact testing of samples at -196°C and subsequent metallography. The M/A particles are identified as the crack nucleation sites and the cleavage fracture stress calculated to be 2400 MPa in a complete AF microstrucuture. This value is significantly larger than in steels that contain significant proportions of conventional bainite. Standard Charpy and Instrumented Charpy impact testing is conducted through a temperature range from -80 to + 22°C to study ductile fracture behaviour. The total absorbed energy is separated into energies of crack nucleation and of crack propagation. It is found that the energy of crack nucleation is weakly dependent on the volume fraction of M/A and completely independent of temperature over the range studied. The crack propagation energy varies significantly with both variables, decreasing with increased volume fraction of M/A and with decreasing temperature. The peak load in the instrumented Charpy data is used to calculate the dynamic fracture toughness, KId, which is found to be 105--120 MPa-m1/2. The void nucleation and void growth stages of ductile fracture are studied by metallographic examination of tensile bars. The sites of void nucleation are identified as inclusions and M/A particles. Voids nucleate at the M/A particles by decohesion of the particle-matrix interface. A constant void nucleation strain of epsilon = 0.90 +/- 0.05 is measured for all of the samples independent of the volume fraction of M/A. A stress-based criterion is used to predict void nucleation and the interface strength is determined to be

  7. Effects of Mn addition on microstructures and mechanical properties of 10Cr ODS ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Hyun Ju; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    Ferritic/martensitic (FM) steels are very attractive for the structural materials of fast fission reactors such as a sodium cooled fast reactor (SFR) owing to their excellent irradiation resistance to a void swelling, but are known to reveal an abrupt loss of their creep and tensile strengths at temperatures above 600 .deg. C. Accordingly, high temperature strength should be considerably improved for an application of the FM steel to the structural materials of SFR. Oxide dispersion strengthened (ODS) FM steels are considered to be promising candidate materials for high- temperature components operating in severe environments such as nuclear fusion and fission systems due to their excellent high temperature strength and radiation resistance stemming from the addition of extremely thermally stable oxide particles dispersed in the ferritic/martensitic matrix.. To develop an advanced ODS steel for core structural materials for next generation nuclear reactor system applications, it is important to optimize its compositions to improve the high temperature strength and radiation resistance. This study investigates effects of Mn addition on microstructures and mechanical properties of 10Cr ODS FM steel. For this, two 10 Cr ODS FM steels were prepared by mechanical alloying (MA), hot isostatic pressing (HIP), and hot rolling process. Tensile tests were carried out at room temperature and 700 .deg. C to evaluate the influences of the Mn element on the mechanical properties. The microstructures were observed using SEM, electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). In the present study, the effects of Mn addition on the microstructure and mechanical properties of ODS FM steels were investigated. The ODS FM steels were manufactured by the MA, HIP and hot-rolling processes.

  8. The effect of surface treatment on the oxidation of ferritic stainless steels used for solid oxide fuel cell interconnects

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, L.; Ivey, D.G. [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta (Canada); Benhaddad, S.; Wood, A. [Versa Power Systems, Calgary, Alberta (Canada)

    2008-09-15

    Ferritic stainless steels are candidate interconnect materials for solid oxide fuel cells (SOFC); however, the oxidation resistance of commercial stainless steels within the operating temperature range of 700-800 C is not adequate. A relatively thick, poorly conducting oxide layer forms on the surface of the stainless steel interconnect, decreasing cell performance. One way of modifying the oxidation behaviour of an alloy is through surface treatment. The aim of this work is to perform a systematic study of the effect of surface treatment (sandblasting and cold rolling) on the oxidation behaviour of three different ferritic stainless steels at 800 C in air. Oxidized specimens are characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, specimens oxidized under the same conditions for 15 min are examined using secondary ion mass spectrometry (SIMS) depth profiling and X-ray photoelectron spectroscopy (XPS) depth profiling. For all three steels, the as-is (undeformed) specimens have a lower mass gain than the deformed specimens. The steel with the highest Cr content has significantly higher mass gains than the other two steels, which have similar mass gains. X-ray diffraction and electron microscopy results indicate that the oxide scale formed on all the specimens consists of an inner layer of chromia and an outer spinel layer. The relative amounts of the two oxide phases present depends on both the steel and treatment condition. The presence of insulating oxides at the metal/oxide interface is detected with both surface science techniques and electron microscopy. (author)

  9. Charpy V-notch properties and microstructures of narrow gap ferritic welds of a quenched and tempered steel plate

    Energy Technology Data Exchange (ETDEWEB)

    Powell, G.L.F.; Herfurth, G. [Commonwealth Scientific and Industrial Research Organization, Woodville (Australia)

    1998-11-01

    Multipass welds of quenched and tempered 50-mm-thick steel plate have been deposited by a single wire narrow gap process using both gas metal arc welding (GMAW) and submerged arc welding (SAW). Of the five welds, two reported much lower Charpy V-notch (CVN) values when tested at {minus} 20 C. The CVN toughness did not correlate with either the welding process or whether the power source was pulsed or nonpulsed. The only difference in the ferritic microstructure between the two welds of low Charpy values and the three of high values was the percentage of acicular ferrite. There was no effect of the percentage of as-deposited reheated zones intersected by the Charpy notch or the microhardness of the intercellular-dendritic regions. In all welds, austenite was the microconstituent between the ferrite laths. The percentage of acicular ferrite correlated with the presence of MnO, TiO{sub 2}, {gamma} Al{sub 2}O{sub 3}, or MnO. Al{sub 2}O{sub 3} as the predominant crystalline compound in the oxide inclusions. In turn, the crystalline compound depended on the aluminum-to-titanium ratio in both the weld deposits and the oxide inclusions. In addition to the presence of less acicular ferrite, the two welds that showed lower Charpy values also reported more oxide inclusions greater than 1 {micro}m in diameter. The combination of more oxide inclusions greater than 1 {micro}m and less acicular ferrite is considered to be the explanation for the lower Charpy values.

  10. Microstructure and tensile properties of oxide strengthened ferritic steel fabricated using as-milled powders with dissolved oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Liqing [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Liu, Zuming, E-mail: csulzm@gmail.com [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Guo, Wei; Chen, Shiqi; Duan, Qinglong; Zhou, Canxu [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Soo, Mun Teng [School of Mechanical and Mining Engineering, University of Queensland, Brisbane, QLD 4067 (Australia)

    2015-06-15

    Highlights: • The work proved the “O-Vacancies Pairs Mechanism” and applied it in experimental. • Hard and soft microstructures’ separation during hot processing was identified. • Precipitate type particles were excellent in strengthening metal–matrix composites. • Bimodal distribution of oxides exhibited two strengthening mechanisms. - Abstract: Pre-alloyed ferritic powders were milled for 10 h in the air atmosphere to introduce O atoms into the steel matrix. Then the milled powders which contained dissolved O were used to fabricate ferritic steels by hot processing. The precipitation of oxide, microstructural evolution and tensile properties of ferritic steels were studied. Results show that about 1.4 wt.% of oxygen was introduced into powders, and the powder surface has a higher O content (about 2–4 wt.%) than the inner region (about 1 wt.%). During hot processing Cr{sub 2}O{sub 3} and Y{sub 2}TiO{sub 5} were precipitated as the main second-phases. Surface regions of powders in which Cr{sub 2}O{sub 3} largely precipitated were elongated, cracked then gathered, and dispersed in the steel matrix along the hot working direction. Tensile results show that the ultimate tensile strength of as-prepared steel in room temperature was 1601 MPa and was still high (1335 MPa) at 550 °C. The excellent tensile strength under 550 °C can be ascribed to the reinforcement of high content of oxide particles in the matrix. The tensile strength suffered a great reduction at temperatures between 550 °C and 650 °C, but it decreased slower at higher tensile temperatures.

  11. Compatibility of graphite with a martensitic-ferritic steel, an austenitic stainless steel and a Ni-base alloy up to 1250 C

    International Nuclear Information System (INIS)

    To study the chemical interactions between graphite and a martensitic-ferritic steel (1.4914), an austenitic stainless steel (1.4919; AISI 316), and a Ni-base alloy (Hastelloy X) isothermal reaction experiments were performed in the temperature range between 900 and 1250 C. At higher temperatures a rapid and complete liquefaction of the components occurred as a result of eutectic interactions. The chemical interactions are diffusion-controlled processes and can be described by parabolic rate laws. The reaction behavior of the two steels is very similar. The chemical interactions of the steels with graphite are much faster above 1100 C than those for the Ni-base alloy. Below 1000 C the effect is opposite. (orig.)

  12. Microstructure and mechanical properties in the weld heat affected zone of 9Cr-2W-VTa reduced activation ferritic/martensitic steel for fusion

    International Nuclear Information System (INIS)

    Reduced activation ferritic/martensitic (RAFM) steel demonstrated excellent resistance to the neutron irradiation and mechanical properties. The investigation of weldability in company with the development of RAFM steel is essential for construction of the fusion reactor. Generally, the superior mechanical properties of the RAFM steel can be upset during welding process due to microstructural change by rapid heating and cooling in the weld heat affected zone (HAZ). The phase transformation and mechanical properties in the weld HAZ of RAFM steel were investigated. The base steel consisted of tempered martensite and two carbides. During rapid welding thermal cycle, the microstructure of the base steel was transformed into martensite and δ-ferrite. In addition, the volume fraction of δ-ferrite and grain size increased with increase in the peak temperature and heat input. The strength of the HAZs was higher than that of the base steel due to the formation of martensite, whereas the impact properties of the HAZs deteriorated as compared with the base steel due to the formation of δ-ferrite. The PWHT improved the impact properties of the HAZs, resulting from the formation of tempered martensite

  13. Microstructure and mechanical properties in the weld heat affected zone of 9Cr-2W-VTa reduced activation ferritic/martensitic steel for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Joonoh; Lee, Changhoon; Lee, Taeho; Jang, Minho; Park, Mingu [Korea Institute of Materials Science, Changwon (Korea, Republic of); Kim, Hyoung Chan [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    Reduced activation ferritic/martensitic (RAFM) steel demonstrated excellent resistance to the neutron irradiation and mechanical properties. The investigation of weldability in company with the development of RAFM steel is essential for construction of the fusion reactor. Generally, the superior mechanical properties of the RAFM steel can be upset during welding process due to microstructural change by rapid heating and cooling in the weld heat affected zone (HAZ). The phase transformation and mechanical properties in the weld HAZ of RAFM steel were investigated. The base steel consisted of tempered martensite and two carbides. During rapid welding thermal cycle, the microstructure of the base steel was transformed into martensite and δ-ferrite. In addition, the volume fraction of δ-ferrite and grain size increased with increase in the peak temperature and heat input. The strength of the HAZs was higher than that of the base steel due to the formation of martensite, whereas the impact properties of the HAZs deteriorated as compared with the base steel due to the formation of δ-ferrite. The PWHT improved the impact properties of the HAZs, resulting from the formation of tempered martensite.

  14. Computer simulation of the effect of copper on defect production and damage evolution in ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Perlado, J M; Marian, J; Lodi, D; Diaz de la Rubia, T

    1999-11-28

    It has long been noticed that the effect of Cu solute atoms is important for the microstructural evolution of ferritic pressure vessel steels under neutron irradiation conditions. Despite the low concentration of Cu in steel, Cu precipitates form inside the a-Fe surrounding matrix and by impeding free dislocation motion considerably contribute to the hardening of the material. It has been suggested that Cu-rich clusters and combined Cu solute atoms-defect clusters that may act as initiating structures of further precipitates nucleate during annealing of displacement cascades. In order to assess the importance of the different mechanisms taking place during collision events in the formation and later evolution of these structures, a detailed Molecular Dynamics (MD) analysis of displacement cascades in a Fe-1.3% at. Cu binary alloy has been carried out. Cascade energies ranging from 1 to 20 keV have been simulated at temperatures of 100 and 600 K using the MDCASK code, in which the Ackland-Finnis-Sinclair many-body interatomic potential has been implemented. The behavior of metastable Cu self-interstitial atoms (SIAs) in the form of mixed Fe-Cu features is studied as well as their impact on the resulting defect structures. It is observed that above 300 K generated Cu SIAs undergo recombination with no substantial effect on the after-cascade microstructure while at 100 K Cu SIAs remain sessile and exhibit a considerable binding to interstitial and vacancy clusters, Finally, the effect that the production of vacancies via collision cascades may have on the self-diffusion of Cu solute atoms is quantitatively addressed by means of determining diffusion coefficients for Cu atoms under different microstructural conditions.

  15. Development of dissimilar welding technique between PNC-FMS wrapper tube and SUS316 steel. 1. Investigation of δ ferrite formation and evaluation of Charpy impact property

    International Nuclear Information System (INIS)

    Ferritic/Martensitic steel (PNC-FMS) with superior resistance to swelling is being developed as wrapper tube for the long-life core of large-scale fast breeder reactor. If the δ ferrite phase would be formed at heat affected zone (HAZ) in welding between PNC-FMS wrapper tube and SUS316 steel, and thus toughness degradation would be suspected due to δ ferrite formation. In this study, the formation of the δ ferrite in applying TIG welding and EB welding are investigated using base metal of 3 types, which are Nieq max./Creq min., Nieq min./Creq max. and the center of chemical composition in the specification. The effect of the amount of the δ ferrite formation and characteristics of toughness change with thermal aging were evaluated. The results are summarized as follows. 1. The δ ferrite generation can be suppressed in the combination of welding process and chemical composition. (1) In case of specification center, the δ ferrite formation can be suppressed about 1% by EB welding. (2) In case of Nieq max./Creq min. in the specification, the δ ferrite formation can be perfectly suppressed even in TIG welding or EB welding. 2. The relationship between δ ferrite content and Charpy impact value was investigated using 3 types of chemical composition in the specification. (1) Ductile Brittle Transition Temperature (DBTT) increased, when δ ferrite content increases. (2) DBTT shift by aging is within about 23degC. (3) DBTT is influenced by grain size and it is lower as the fine grain (grain no.11). (4) Upper Shelf Energy (USE) is not dependent on the δ ferrite content. (author)

  16. Helium Retention and Desorption Behaviour of Reduced Activation Ferritic/Martenstic Steel

    Science.gov (United States)

    Wang, Pinghuai; Nobuta, Yuji; Hino, Tomoaki; Yamauchi, Yuji; Chen, Jiming; Xu, Zengyu; Li, Xiongwei; Liu, Shi

    2009-04-01

    The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwestern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites.

  17. Using nonlinear ultrasound measurements to track thermal aging in modified 9%Cr ferritic martensitic steel

    Science.gov (United States)

    Marino, Daniel; Kim, Jin-Yeon; Jacobs, Laurence J.; Ruiz, Alberto; Joo, Young-Sang

    2015-03-01

    This study investigates early thermal aging in 9%Cr ferritic martensitic (FM) steel, which is caused by the formation of second phases during high temperature exposure. This study employs a recently developed nonlinear ultrasonic technique to explore the sensitivity of the nonlinearity parameter. Experimental results show that the nonlinearity parameter is sensitive to certain changes in material's properties such as thermal embrittlement and hardness changes; therefore, it can be used as an indicator of the thermal damage. The specimens investigated are heat treated for different holding times ranging from 200h to 3000h at 650°C. Nonlinear ultrasonic experiments are conducted for each specimen using a wedge transducer to generate and an air-coupled transducer to detect Raleigh surface waves. The amplitudes of the first and second order harmonics are measured at different propagation distances and these amplitudes are used to obtain the relative nonlinearity parameter for each specimen with a different holding time. The nonlinear ultrasonic results are compared with independent mechanical measurements and metallographic images. This research proposes the nonlinear ultrasonic technique as a nondestructive evaluation tool not only to detect thermal damage in early stages, and also to qualitatively assess the stage of thermal damage.

  18. Helium Retention and Desorption Behaviour of Reduced Activation Ferritic/Martenstic Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Pinghuai; NOBUTA Yuji; HINO Tomoaki; YAMAUCHI Yuji; CHEN Zilning; XU Zengyu; LI Xiongwei; LIU Shi

    2009-01-01

    The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwest-ern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites.

  19. Experimental analysis of dissimilar metal weld joint: Ferritic to austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Rathod, Dinesh W., E-mail: dineshvrathod@gmail.com [Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi 110016 (India); Pandey, Sunil [Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi 110016 (India); Singh, P.K. [Bhabha Atomic Research Centre, Mumbai 400085 (India); Prasad, Rajesh [Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2015-07-15

    The dissimilar metal weld (DMW) joint between SA508Gr.3Cl.1 ferritic steel and SS304LN using Inconel 82/182 consumables was required in the nuclear power plants. The joint integrity assessment of these welds requires mechanical and metallurgical properties evaluation in weldment regions. The joint was subjected to 100% radiography test and bend test and transverse tensile test. Welding and testing were carried out as per the requirements of ASME Sec-IX and acceptance criteria as per ASME Sec-III. The transverse tensile test results indicated the failure from the weld metal although it satisfies the minimum strength requirement of the ASME requirements; therefore, the DMW joint was analyzed in detail. Straight bead deposition technique, fine slag inclusion, less reliable radiograph technique, plastic instability stress, yield strength ratio and metallurgical deteriorations have been contributed to failure of the DMW joint from the weld region. In the present work, the factors contributing to the fracture from weld metal have been discussed and analyzed.

  20. Refinement of ferrite grain size during hot direct rolling of hsla steel

    International Nuclear Information System (INIS)

    Steel ingots containing 0.04 wt % Nb and varying contents of carbon were made in laboratory, that simulated thin slab casting. Mn and Si content were kept constant at 1.35 % and 0.25 % respectively. After each casting the mould assembly was transferred to the rolling mill and the temperature of the ingot was monitored. Each ingot was rolled to 4mm thickness in three passes. The first pass of 43% reduction for all the ingots were given at 1140 degree C. The second pass (reduction, 35 %) for all the ingots were given at 1040 degree C. However the temperature for third pass (reduction, 30 %) was varied to retain more strain in the austenite prior to transformation. It was shown that third pass at lower temperature i.e. 810 degree C in the austenite range yields a ferrite grains size of 2-3 micrometer. A yield strength of 465 Mpa and tensile strength of 530 Mpa can also be achieved in these plates. (author)

  1. Comparison of resistance to corrosion on haz of a ferritic stainless steel by different surface finishings

    Directory of Open Access Journals (Sweden)

    Juvenilson Costa Damascena

    2015-10-01

    Full Text Available Certain techniques, comprising machining and GTAW dressing, have been used in the weld bead edge (region of the welded joint between the weld metal and the base metal to increase the fillet radius of the region by reducing the stress concentrator factor, decreasing roughness, and increasing the life of weldings. Moreover, TIG Dressing may also provide a smooth change in the radius of the curvature and change the average grain size and promote a microstructural variation through the reflow of this region. Current study analyzes the effect of surface finish of the Heat Affected Zone (HAZ on resistance to corrosion of welded joints of simple deposition under plate by using machining techniques with sandpaper of different particle sizes and GTAW Dressing, comparing the effect of the two techniques in the resistance to corrosion in environments with chloride ions. ACE P410D ferritic stainless steel was employed as base metal and austenitic wire 308L for welding. Results showed that the condition sweetened with GTAW Dressing with pure argon at current 100A generated the lowest mass loss among the conditions under analysis.

  2. Influence of stress on creep deformation properties of 9-12Cr ferritic creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, K.; Sawada, K.; Kushima, H. [National Institute for Materials Science (Japan)

    2008-07-01

    Creep deformation property of 9-12Cr ferritic creep resistant steels was investigated. With decrease in stress, a magnitude of creep strain at the onset of accelerating creep stage decreased from about 2% in the short-term to less than 1% in the longterm. A time to 1% total strain was observed in the transient creep stage in the short term regime, however, it shifted to the accelerating creep stage in the long-term regime. Life fraction of the times to 1% creep strain and 1% total strain tended to increase with decrease in stress. Difference in stress dependence of the minimum creep rate was observed in the high- and low-stress regimes with a boundary condition of 50% of 0.2% offset yield stress. Stress dependence of the minimum creep rate in the high stress regime was equivalent to a strain rate dependence of the flow stress evaluated by tensile test, and a magnitude of stress exponent, n, in the high stress regime decreased with increase in temperature from 20 at 550 C to 10 at 700 C. On the other hand, n value in the low stress regime was about 5, and creep deformation in the low stress regime was considered to be controlled by dislocation climb. Creep rupture life was accurately predicted by a region splitting method by considering a change in stress dependence of creep deformation. (orig.)

  3. Thermo-mechanical fatigue properties of a ferritic stainless steel for solid oxide fuel cell interconnect

    Science.gov (United States)

    Chiu, Yung-Tang; Lin, Chih-Kuang

    2012-12-01

    Thermo-mechanical fatigue (TMF) behavior of a newly developed ferritic stainless steel (Crofer 22 H) for planar solid oxide fuel cell (pSOFC) interconnect is investigated. TMF tests under various combinations of cyclic mechanical and thermal loadings are conducted in air at a temperature range of 25oC-800 °C. Experimental results show the number of cycles to failure for non-hold-time TMF loading is decreased with an increase in the minimum stress applied at 800 °C. There is very little effect of maximum stress applied at 25 °C on the number of cycles to failure. The non-hold-time TMF life is dominated by a fatigue mechanism involving cyclic high-temperature softening plastic deformation. A hold-time of 100 h for the minimum stress applied at 800 °C causes a significant drop of number of cycles to failure due to a synergistic action of fatigue and creep. Creep and creep-fatigue interaction mechanisms are the two primary contributors to the hold-time TMF damage. The creep damage ratio in the hold-time TMF damage is increased with a decrease in applied stress at 800 °C and an increase in number of cycles to failure.

  4. Elevated-temperature tensile and creep properties of several ferritic stainless steels

    Science.gov (United States)

    Whittenberger, J. D.

    1977-01-01

    The elevated-temperature mechanical properties of several ferritic stainless steels were determined. The alloys evaluated included Armco 18SR, GE 1541, and NASA-18T-A. Tensile and creep strength properties at 1073 and 1273 K and residual room temperature tensile properties after creep testing were measured. In addition, 1273 K tensile and creep tests and residual property testing were conducted with Armco 18SR and GE 1541 which were exposed for 200 hours to a severe oxidizing environment in automotive thermal reactors. Aside from the residual tensile properties for Armco 18SR, prior exposure did not affect the mechanical properties of either alloy. The 1273 K creep strength parallel to the sheet-rolling direction was similar for all three alloys. At 1073 K, NASA-18T-A had better creep strength than either Armco 18SR or GE 1541. NASA-18T-A possesses better residual properties after creep testing than either Armco 18SR or Ge 1541.

  5. Study on the activated laser welding of ferritic stainless steel with rare earth elements yttrium

    Science.gov (United States)

    Wang, Yonghui; Hu, Shengsun; Shen, Junqi

    2015-10-01

    The ferritic stainless steel SUS430 was used in this work. Based on a multi-component activating flux, composed of 50% ZrO2, 12.09 % CaCO3, 10.43 % CaO, and 27.49 % MgO, a series of modified activating fluxes with 0.5%, 1%, 2%, 5%, 10%, 15%, and 20% of rare earth (RE) element yttrium (Y) respectively were produced, and their effects on the weld penetration (WP) and corrosion resistant (CR) property were studied. Results showed that RE element Y hardly had any effects on increasing the WP. In the FeCl3 spot corrosion experiment, the corrosion rates of almost all the samples cut from welded joints turned out to be greater than the parent metal (23.51 g/m2 h). However, there was an exception that the corrosion rate of the sample with 5% Y was only 21.96 g/m2 h, which was even better than parent metal. The further Energy Dispersive Spectrometer (EDS) test showed the existence of elements Zr, Ca, O, and Y in the molten slag near the weld seam while none of them were found in the weld metal, indicating the direct transition of element from activating fluxes to the welding seam did not exist. It was known that certain composition of activating fluxes effectively restrain the loss of Cr element in the process of laser welding, and as a result, the CR of welded joints was improved.

  6. Incidence of mechanical alloying contamination on oxides and carbides formation in ODS ferritic steels

    International Nuclear Information System (INIS)

    Ferritic ODS steels containing 14 or 18 wt.% Cr are produced by mechanical alloying (MA), hot consolidation and cold working. This study focuses on the evolution of interstitials such as oxygen, nitrogen and carbon at each stage of the fabrication route by comparing two MA methods: attrition milling or ball milling. The milling time required to obtain a homogenous distribution of yttrium at the micron scale in the ground powders is relatively short by using an attritor. But, in this case the carbon and nitrogen contamination is more pronounced considering powders which have reached a similar metastable stationary state. The presence of oxygen in excess results in the formation of large micron-sized oxides after extrusion. Most of them are identified as titanium-based or silicon oxides by EDS analysis. For attrition milling, a high density of aligned Ti(C,N) compounds and some FeCrW carbides (M23C6 type) mainly distributed at the grain boundaries are identified, correlated with the higher carbon contamination

  7. A closer look at the fracture toughness of ferritic/martensitic steels

    Science.gov (United States)

    Lucon, Enrico

    2007-08-01

    SCK·CEN has characterized the mechanical properties of several ferritic/martensitic steels, both unirradiated and irradiated. Fracture toughness has been evaluated using Charpy impact and fracture mechanics tests. Two safety-related features have emerged: (a) the applicability of the master curve approach (ASTM E1921-05) appears questionable; and (b) irradiation embrittlement is systematically larger when quantified in terms of quasi-static fracture toughness than when measured from Charpy tests. Both issues are examined in detail and possible interpretations are proposed; potential improvements given by the application of more advanced fracture toughness analysis methodologies are discussed. In order to clarify whether the Charpy/fracture toughness difference in embrittlement is due to loading rate effects, dynamic toughness tests have been performed in the unirradiated condition and for two irradiation doses (0.3 and 1.6 dpa). The corresponding dynamic T0 shifts have been compared with the shifts of Charpy and master curve quasi-static transition temperatures. Other possible contributions are examined and discussed.

  8. Impact property degradation of ferritic/martensitic steels after the fast reactor irradiation 'ARBOR 1'

    International Nuclear Information System (INIS)

    In an energy generating fusion reactor, structural materials will be exposed to very high levels of irradiation damage of about 100 dpa. These damage conditions can be realized - in reasonable times - only in fast reactors. For this purpose a cooperation between Forschungszentrum Karlsruhe and State Scientific Centre of Russian Federation Research Institute of Atomic Reactors had been implemented. The irradiation project is named 'ARBOR 1' (Latin for tree). Impact, tensile and low cycle fatigue specimens of reduced activation ferritic/martensitic steels, e.g. EUROFER 97, F82H mod., OPTIFER IVc, EUROFER 97 with different boron contents and ODS-EUROFER 97 have been irradiated in a fast neutron flux of 1.8 x 1015 n/cm2 s (>0.1 MeV) at a temperature oC up to ∼30 dpa. In the post irradiation impact tests a dramatic increase in the ductile to brittle transition temperature as an effect of irradiation has been detected

  9. Modelling of the evolution of micro-grain misorientations during creep of tempered martensite ferritic steels

    International Nuclear Information System (INIS)

    Tempered martensite ferritic steels are prone to low-angle boundary (LAB) vanishing and micro-grain size increase during creep deformation. A physically based model of LAB vanishing during creep deformation is presented. The LABs are modelled by simple dislocation arrays following the Read and Shockley model. Depending on the activated slip systems, mobile edge/screw dislocations annihilate with LAB parallel dislocations of opposite sign. The LAB misorientation frequency evolution versus creep strain can be analytically computed. The material parameters are the fractions of edge/screw dislocations in the LABs and the critical edge/screw dislocation annihilation distances. Different LAB misorientation frequencies obtained by electron backscatter diffraction (EBSD) and available in the literature are used as input data of the simulations. The computed LAB misorientation frequencies are then compared with the experimental frequencies obtained at different creep strains. If the material parameters belong to physical ranges, their influence on the predictions remain rather weak. The model generally permits a reasonable prediction of misorientation and micro-grain size evolutions during creep. Finally, the effects of precipitate evolution, climb and internal stresses are discussed.

  10. A reassessment of the effects of helium on Charpy impact properties of ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S.; Hamilton, M.L. [Pacific Northwest National Lab., Richland, WA (United States); Hankin, G.L. [Loughborough Univ. (United Kingdom)

    1998-03-01

    To test the effect of helium on Charpy impact properties of ferritic/martensitic steels, two approaches are reviewed: quantification of results of tests performed on specimens irradiated in reactors with very different neutron spectra, and isotopic tailoring experiments. Data analysis can show that if the differences in reactor response are indeed due to helium effects, then irradiation in a fusion machine at 400 C to 100 dpa and 1000 appm He will result in a ductile to brittle transition temperature shift of over 500 C. However, the response as a function of dose and helium level is unlikely to be simply due to helium based on physical reasoning. Shear punch tests and microstructural examinations also support this conclusion based on irradiated samples of a series of alloys made by adding various isotopes of nickel in order to vary the production of helium during irradiation in HFIR. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys. However, helium itself, up to 75 appm at over 7 dpa appears to have little effect on the mechanical properties of the alloys. This behavior is instead understood to result from complex precipitation response. The database for effects of helium on embrittlement based on nickel additions is therefore probably misleading and experiments should be redesigned to avoid nickel precipitation.

  11. Effect of Process Parameters on Microstructure and Hardness of Oxide Dispersion Strengthened 18Cr Ferritic Steel

    Science.gov (United States)

    Nagini, M.; Vijay, R.; Rajulapati, Koteswararao V.; Rao, K. Bhanu Sankara; Ramakrishna, M.; Reddy, A. V.; Sundararajan, G.

    2016-06-01

    Pre-alloyed ferritic 18Cr steel (Fe-18Cr-2.3W-0.3Ti) powder was milled with and without nano-yttria in high-energy ball mill for varying times until steady-state is reached. The milled powders were consolidated by upset forging followed by hot extrusion. Microstructural changes were examined at all stages of processing (milling, upset forging, and extrusion). In milled powders, crystallite size decreases and hardness increases with increasing milling time reaching a steady-state beyond 5 hours. The size of Y2O3 particles in powders decreases with milling time and under steady-state milling conditions; the particles either dissolve in matrix or form atomic clusters. Upset forged sample consists of unrecrystallized grain structure with few pockets of fine recrystallized grains and dispersoids of 2 to 4 nm. In extruded and annealed rods, the particles are of cuboidal Y2Ti2O7 at all sizes and their size decreased from 15 nm to 5 nm along with significant increase in number density. The oxide particles in ODS6 are of cuboidal Y2Ti2O7 with diamond cubic crystal structure (Fd bar{3} m) having a lattice parameter of 10.1 Å and are semicoherent with the matrix. The hardness values of extruded and annealed samples predicted by linear summation model compare well with measured values.

  12. Development of high strength ferritic steel for interconnect application in SOFCs

    Science.gov (United States)

    Froitzheim, J.; Meier, G. H.; Niewolak, L.; Ennis, P. J.; Hattendorf, H.; Singheiser, L.; Quadakkers, W. J.

    High-Cr ferritic model steels containing various additions of the refractory elements Nb and/or W were studied with respect to oxidation behaviour (hot) tensile properties, creep behaviour and high-temperature electrical conductivity of the surface oxide scales. Whereas W additions of around 2 wt.% had hardly any effect on the oxidation rates at 800 and 900 °C, Nb additions of 1% led to a substantially enhanced growth rate of the protective surface oxide scale. It was found that this adverse effect can be alleviated by suitable Si additions. This is related to the incorporation of Si and Nb into Laves phase precipitates which also contribute to increased creep and hot tensile strength. The dispersion of Laves phase precipitates was greatly refined by combined additions of Nb and W. The high-temperature electrical conductivity of the surface oxide scales was similar to that of the Nb/W-free alloys. Thus the combined additions of Nb, W and Si resulted in an alloy with oxidation resistance, ASR contribution and thermal expansion comparable to the commercial alloy Crofer 22 APU, but with creep strength far greater than that of Crofer 22 APU.

  13. Effect of acicular ferrite on banded structures in low-carbon microalloyed steel

    Institute of Scientific and Technical Information of China (English)

    Lei Shi; Ze-sheng Yan; Yong-chang Liu; Xu Yang; Cheng Zhang; Hui-jun Li

    2014-01-01

    The effect of acicular ferrite (AF) on banded structures in low-carbon microalloyed steel with Mn segregation during both iso-thermal transformation and continuous cooling processes was studied by dilatometry and microscopic observation. With respect to the iso-thermal transformation process, the specimen isothermed at 550°C consisted of AF in Mn-poor bands and martensite in Mn-rich bands, whereas the specimen isothermed at 450°C exhibited two different morphologies of AF that appeared as bands. At a continuous cooling rate in the range of 4 to 50°C/s, a mixture of AF and martensite formed in both segregated bands, and the volume fraction of martensite in Mn-rich bands was always higher than that in Mn-poor bands. An increased cooling rate resulted in a decrease in the difference of martensite volume fraction between Mn-rich and Mn-poor bands and thereby leaded to less distinct microstructural banding. The results show that Mn segregation and cooling rate strongly affect the formation of AF-containing banded structures. The formation mechanism of microstructural banding was also discussed.

  14. Joining of tungsten to ferritic/martensitic steels by hot isostatic pressing

    International Nuclear Information System (INIS)

    Tungsten (W) was joined to ferritic/martensitic steels (FMSs) by hot isostatic pressing (HIP) with interlayers consisting of Ti or Cr coatings and inserted Ti and Cu films. The effects of interlayer type and post-HIP heat treatment (PHHT) on the joining properties of W/FMS were investigated by evaluating the joining strength and analyzing the interface microstructure. The W/FMS joint specimens with the inserted Ti films showed a higher shear strength than those with Cu films, irrespective of the coating layer type. The complicated interface microstructure with many diffusion layers in the W/FMS joint led to a decrease in the joining strength. The effect of PHHT was different depending on the interlayer type employed in the HIP joining. PHHT was beneficial especially for the HIP joined W/FMS with Ti(2 μm)/Ti(50 μm) interlayers when it was properly performed to avoid a split at the interface in an edge of the HIP joined block

  15. Microstructural characterization of weld joints of 9Cr reduced activation ferritic martensitic steel fabricated by different joining methods

    Energy Technology Data Exchange (ETDEWEB)

    Thomas Paul, V.; Saroja, S.; Albert, S.K.; Jayakumar, T.; Rajendra Kumar, E., E-mail: vtp@igcar.gov.in

    2014-10-15

    This paper presents a detailed electron microscopy study on the microstructure of various regions of weldment fabricated by three welding methods namely tungsten inert gas welding, electron beam welding and laser beam welding in an indigenously developed 9Cr reduced activation ferritic/martensitic steel. Electron back scatter diffraction studies showed a random micro-texture in all the three welds. Microstructural changes during thermal exposures were studied and corroborated with hardness and optimized conditions for the post weld heat treatment have been identified for this steel. Hollomon–Jaffe parameter has been used to estimate the extent of tempering. The activation energy for the tempering process has been evaluated and found to be corresponding to interstitial diffusion of carbon in ferrite matrix. The type and microchemistry of secondary phases in different regions of the weldment have been identified by analytical transmission electron microscopy. - Highlights: • Comparison of microstructural parameters in TIG, electron beam and laser welds of RAFM steel • EBSD studies to illustrate the absence of preferred orientation and identification of prior austenite grain size using phase identification map • Optimization of PWHT conditions for indigenous RAFM steel • Study of kinetics of tempering and estimation of apparent activation energy of the process.

  16. PERFORMANCE IMPROVEMENT OF CREEP-RESISTANT FERRITIC STEEL WELDMENTS THROUGH THERMO-MECHANICAL TREATMENT AND ALLOY DESIGN

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Yukinori [ORNL; Babu, Prof. Sudarsanam Suresh [University of Tennessee, Knoxville (UTK); Shassere, Benjamin [ORNL; Yu, Xinghua [ORNL

    2016-01-01

    Two different approaches have been proposed for improvement of cross-weld creep properties of the high temperature ferrous structural materials for fossil-fired energy applications. The traditional creep strength-enhanced ferritic (CSEF) steel weldments suffer from Type IV failures which occur at the fine-grained heat affected zone (FGHAZ). In order to minimize the premature failure at FGHAZ in the existing CSEF steels, such as modified 9Cr-1Mo ferritic-martensitic steels (Grade 91), a thermo-mechanical treatment consisting of aus-forging/rolling and subsequent aus-aging is proposed which promotes the formation of stable MX carbonitrides prior to martensitic transformation. Such MX remains undissolved during welding process, even in FGHAZ, which successfully improves the cross-weld creep properties. Another approach is to develop a new fully ferrtic, creep-resistant FeCrAl alloy which is essentially free from Type IV failure issues. Fe-30Cr-3Al base alloys with minor alloying additions were developed which achieved a combination of good oxidation/corrosion resistance and improved tensile and creep performance comparable or superior to Grade 92 steel.

  17. Microstructure and mechanical property of in-situ nano-particle strengthened ferritic steel by novel internal oxidation

    International Nuclear Information System (INIS)

    A novel route of fabricating nano-particles strengthened ferrite steel was investigated in this study. Rather than by externally adding nano-oxide powders, we adopted the endogenous method of controlling oxide reaction and solute concentration distribution in the process of deoxidization to obtain a high density of in-situ nano-oxide particles homogeneously dispersed in the ferrite matrix in melt. The microstructure and tensile properties of these materials had been investigated to clarify the interrelation between the composition, microstructure and mechanical properties. Transmission electron microscopy (TEM) analysis indicated that these nano-particles were titanium oxides, which have a positive effect on optimizing inclusions and refining grains. Tensile tests revealed that these titanium oxide particles play an important role in increasing the yield strength. The steel has yield strength of 711 MPa, approximately three times higher than that of conventional plain carbon structural steels, and its ultimate tensile strength reaches 810 MPa with an elongation-to-failure value of 22%. Precipitation hardening and grain refinement hardening are the dominant factors responsible for yield strength increasing in this steel

  18. Thermodynamic calculations and experiments on inclusions to be nucleation sites for intragranular ferrite in Si-Mn-Ti deoxidized steel

    Institute of Scientific and Technical Information of China (English)

    Xiaojun Zhuo; Xinhua Wang; Wan jun Wang; Lee HaeGeon

    2007-01-01

    Microstructures and inclusions in the Si-Mn-Ti deoxidized steels after cooling in the furnace were investigated.The composition and morphology of the inclusions were analyzed using a field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray spectrometry (EDS).The kind and composition of the inclusions calculated from the thermodynamic database were in good agreement with the experimental results.There were two main kinds of inclusions formed in the Si-Mn-Ti deoxidized steels.One kind of inclusion was the manganese titanium oxide (Mn-Ti oxide).Another kind of inclusion was the MnS inclusion with segregation points containing Ti and N.According to the thermodynamic calculation,those segregation points were TiN precipitates.The formation of intragranular ferrite (IGF) microstructures refined the grain size during the austenite-ferrite transformation.The mechanisms of IGF formation were discussed.Mn-Ti oxide inclusions with Mn-depleted zone (MDZ) were effective to be nucleation sites for IGF formation,because the MDZ increased the austenite-ferrite transformation temperature.TiN had the low misfit ratio with IGF,so the TiN precipitated on the MnS surface also promoted the formation of IGF because of decreasing interfacial energies.

  19. Experimental Investigation on the Performance of Armour Grade Q&T Steel Joints Fabricated by Flux Cored Arc Welding with Low Hydrogen Ferritic Consumables

    Institute of Scientific and Technical Information of China (English)

    G. Magudeeswaran; V. Balasubramanian; G. Madhusudhan Reddy; G. Gopalakrishnan

    2009-01-01

    Quenched and Tempered (Q&T) steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking (HIC) and softening in the heat affected zone (HAZ) after welding. The use of austenitic stainless steel (ASS) consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic (LHF) steel consumables can also be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q&T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely (i) austenitic stainless steel and (ii) low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding (FCAW) process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone (CGHAZ) is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.

  20. Study on microstructures and tensile properties with addition of V and Sc in ODS ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Hyun Ju; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    High temperature strength should be considerably improved for an application of the FM steel to the structural materials of SFR. Oxide dispersion strengthened (ODS) FM steels are considered to be promising candidate materials for high- temperature components operating in severe environments such as nuclear fusion and fission systems due to their excellent high temperature strength and radiation resistance stemming from the addition of extremely thermally stable oxide particles dispersed in the ferritic/martensitic matrix. To develop an advanced ODS steel for core structural materials for next generation nuclear reactor system applications, it is important to optimize its compositions to improve the high temperature strength and radiation resistance. This study investigates effects of addition of V and Sc on microstructures and mechanical properties of 10Cr ODS FM steel. For this, three kinds of 10 Cr ODS FM steels were prepared by mechanical alloying (MA), hot isostatic pressing (HIP), and hot rolling process. Tensile tests were carried out at room temperature and 700 .deg. C to evaluate the influences of V and Sc elements on the mechanical properties. The microstructures were observed using SEM, electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). This study investigated the effects of addition of V and Sc on the microstructure and tensile properties of ODS FM steels. The ODS FM steels were fabricated by the MA, HIP and hot-rolling processes.

  1. Sigma-phase formation in high chromium ferritic steels at 650 °C

    Energy Technology Data Exchange (ETDEWEB)

    Niewolak, L., E-mail: l.niewolak@fz-juelich.de [Forschungszentrum Jülich, IEF-2, 52428 Jülich (Germany); Garcia-Fresnillo, L.; Meier, G.H. [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA (United States); Quadakkers, W.J. [Forschungszentrum Jülich, IEF-2, 52428 Jülich (Germany)

    2015-07-25

    Highlights: • Formation of σ-FeCr phase at 650 °C in alloys Fe–30%Cr–2%(Mn,Mo,W) was investigated. • Formation of σ-FeCr phase was accelerated by interdiffusion with Ni-coating. • Mechanism of heterogeneous nucleation of σ-FeCr at BCC/FCC interface was discussed. • Mechanisms of homogenous and heterogeneous nucleation were discussed. • Improvement of isothermal section of Fe–Cr–Ni phase diagram at 650 °C was proposed. - Abstract: A binary Fe–30 wt.%Cr alloy and corresponding ternary alloys containing manganese, molybdenum or tungsten were studied with respect to σ-phase formation at 650 °C. Although even after 3000 h exposure complete equilibration was not attained, the presence of tungsten and especially molybdenum was found to promote σ-phase formation. More extensive σ-phase formation was observed in the tungsten and especially in the molybdenum-containing alloys than in the binary and manganese-containing alloy. Apparently the bulk free energy decrease driving the nucleation of σ-phase is substantially larger when tungsten or molybdenum are present in the alloy. The presence of a nickel layer, to simulate the contact between ferritic steel interconnects and nickel mesh in a Solid Oxide Fuel Cell (SOFC) results in the formation of an austenitic zone and in accelerated formation of a σ-phase rich layer at the ferrite/austenite interface, due to interdiffusion processes. This interface acts as a highly efficient heterogeneity for the nucleation of σ-phase. The nucleation is enhanced by an increased Cr/Fe-ratio at that interface. Several possible modes for the growth of the σ layer were identified but the available experimental data were not sufficient to distinguish among these. The σ-rich layer, which appears to act as an interdiffusion barrier, is thicker in the case of the binary Fe–Cr and the Fe–Cr–Mn alloy than for the molybdenum- or tungsten-rich alloys. The results show that the stability range of σ-phase is larger

  2. Ultra-fine ferrite grain refinement by static re-crystallization of hot rolled vanadium micro-alloyed steels

    International Nuclear Information System (INIS)

    The phenomenon of ultrafine-grain refinement of ferrite during transformational grain refinement (TGR) followed by static re-crystallization of vanadium micro-alloyed steels was studied. A substantial grain refinement (2.8 mu m) was attained during TGR process by rolling at 900 deg. C. Cold rolling with 70% of reduction introduced strain, utilized for re-crystallization during annealing at different temperatures. Electron Backscattered Diffraction (EBSD) technique was employed to quantify the low angle grain boundaries (LAGB) and high angle grain boundaries (HAGB) spacings and results were correlated with hardness drops during annealing process. At higher annealing times and temperatures the vanadium precipitates restricted the process of grain growth probably due to effective dispersion strengthening. The abnormal grain growth during annealing, predicted previously for niobium steels, found absent in the present vanadium microalloyed steels. (author)

  3. TEM observation and fracture morphology in the CGHAZ of a new 0Cr18Mo2Ti ferritic stainless steel

    Indian Academy of Sciences (India)

    Li Yajiang; Zhang Yonglan; Sun Bin; Wang Juan

    2002-10-01

    Microstructure, precipitates and fracture morphology in the coarse grained heat-affected zone (CGHAZ) of a new high-purity 0Cr18Mo2Ti ferritic stainless steel were studied by means of optical metallography, SEM, TEM, X-ray diffractometer, etc. Experimental results indicated that grain coarsening resulted in brittle fracture in the CGHAZ of 0Cr18Mo2Ti steel. The reduction of impact toughness in the CGHAZ due to change of cooling rate can be attributed to the increase of nitrides (TiN, Cr2N, etc). These nitrides in the CGHAZ promote initiation and propagation of brittle cracks. The precipitated Cr2N nitrides in the grain boundaries decrease impact toughness in the CGHAZ of 0Cr18Mo2Ti steel by promoting crack initiation. In practical applications, the welding heat input () should be as low as possible to prevent toughness reduction in the CGHAZ.

  4. Microstructure and mechanical properties of heat-resistant 12% Cr ferritic-martensitic steel EK-181 after thermomechanical treatment

    Science.gov (United States)

    Polekhina, N. A.; Litovchenko, I. Yu.; Tyumentsev, A. N.; Astafurova, E. G.; Chernov, V. M.; Leontyeva-Smirnova, M. V.

    2015-10-01

    The effect of high-temperature thermomechanical treatment (TMT) with the deformation in the austenitic region on the features of microstructure, phase transformations and mechanical properties of low-activation 12% Cr ferritic-martensitic steel EK-181 is investigated. It is established, that directly after thermomechanical treatment (without tempering) the sizes and density of V(CN) particles are comparable with those after a traditional heat treatment (air quenching and tempering at 720°C, 3 h), where these particles are formed only during tempering. It causes the increasing of the yield strength of the steel up to ≈1450 MPa at room temperature and up to ≈430 MPa at the test temperature T = 650°C. The potential of microstructure modification by this treatment aimed at improving heat resistance of steel is discussed.

  5. Study of MHD Corrosion and Transport of Corrosion Products of Ferritic/Martensitic Steels in the Flowing PbLi and its Application to Fusion Blanket

    OpenAIRE

    Saeidi, Sheida

    2014-01-01

    Two important components of a liquid breeder blanket of a fusion power reactor are the liquid breeder/coolant and the steel structure that the liquid is enclosed in. One candidate combination for such components is Lead-Lithium (PbLi) eutectic alloy and advanced Reduced Activation Ferritic/Martensitic (RAFM) steel. Implementation of RAFM steel and PbLi in blanket applications still requires material compatibility studies as many questions related to physical/chemical interactions in the RAFM...

  6. Load partitioning between ferrite/martensite and dispersed nanoparticles of a 9Cr ferritic/martensitic (F/M) ODS steel at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guangming; Mo, Kun; Miao, Yinbin; Liu, Xiang; Almer, Jonathan; Zhou, Zhangjian; Stubbins, James F.

    2015-06-18

    In this study, a high-energy synchrotron radiation X-ray technique was used to investigate the tensile deformation processes of a 9Cr-ODS ferritic/martensitic (F/M) steel at different temperatures. Two minor phases within the 9Cr-ODS F/M steel matrix were identified as Y2Ti2O7 and TiN by the high-energy X-ray diffraction, and confirmed by the analysis using energy dispersive X-ray spectroscopy (EDS) of scanning transmission electron microscope (STEM). The lattice strains of the matrix and particles were measured through the entire tensile deformation process. During the tensile tests, the lattice strains of the ferrite/martensite and the particles (TiN and Y2Ti2O7) showed a strong temperature dependence, decreasing with increasing temperature. Analysis of the internal stress at three temperatures showed that the load partitioning between the ferrite/martensite and the particles (TiN and Y2Ti2O7) was initiated during sample yielding and reached to a peak during sample necking. At three studied temperatures, the internal stress of minor phases (Y2Ti2O7 and TiN) was about 2 times that of F/M matrix at yielding position, while the internal stress of Y2Ti2O7 and TiN reached about 4.5-6 times and 3-3.5 times that of the F/M matrix at necking position, respectively. It indicates that the strengthening of the matrix is due to minor phases (Y2Ti2O7 and TiN), especially Y2Ti2O7 particles. Although the internal stresses of all phases decreased with increasing temperature from RT to 600 degrees C, the ratio of internal stresses of each phase at necking position stayed in a stable range (internal stresses of Y2Ti2O7 and TiN were about 4.5-6 times and 3-3.5 times of that of F/M matrix, respectively). The difference between internal stress of the F/M matrix and the applied stress at 600 degrees C is slightly lower than those at RI and 300 degrees C, indicating that the nanoparticles still have good strengthening effect at 600 degrees C. (C) 2015 Elsevier B.V. All rights reserved.

  7. Formation of Delta Ferrite in 9 Wt Pct Cr Steel Investigated by In-Situ X-Ray Diffraction Using Synchrotron Radiation

    Science.gov (United States)

    Mayr, P.; Palmer, T. A.; Elmer, J. W.; Specht, E. D.; Allen, S. M.

    2010-10-01

    In-situ X-ray diffraction (XRD) measurements using high energy synchrotron radiation were performed to monitor in real time the formation of delta ferrite in a martensitic 9 wt pct chromium steel under simulated weld thermal cycles. Volume fractions of martensite, austenite, and delta ferrite were measured as a function of temperature at a 10 K/s heating rate to 1573 K (1300 °C) and subsequent cooling. At the peak temperature, the delta ferrite concentration rose to 19 pct, of which 17 pct transformed back to austenite on subsequent cooling.

  8. Electron work functions of ferrite and austenite phases in a duplex stainless steel and their adhesive forces with AFM silicon probe.

    Science.gov (United States)

    Guo, Liqiu; Hua, Guomin; Yang, Binjie; Lu, Hao; Qiao, Lijie; Yan, Xianguo; Li, Dongyang

    2016-01-01

    Local electron work function, adhesive force, modulus and deformation of ferrite and austenite phases in a duplex stainless steel were analyzed by scanning force microscopy. It is demonstrated that the austenite has a higher electron work function than the ferrite, corresponding to higher modulus, smaller deformation and larger adhesive force. Relevant first-principles calculations were conducted to elucidate the mechanism behind. It is demonstrated that the difference in the properties between austenite and ferrite is intrinsically related to their electron work functions. PMID:26868719

  9. Steam oxidation scale growth and thermal insulation effect on creep life of creep strength enhanced ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Masuyama, Fujimitsu; Tokunaga, Tatsuya [Kyushu Inst. of Technology (Japan). Graduate School of Engineering; Takao, Mikito [Kyushu Inst. of Technology (Japan). Graduate School of Engineering; JFE Steel Corporation (Japan); Arakawa, Katsutoshi [Kyushu Inst. of Technology (Japan). Graduate School of Engineering; Kobe Steel Ltd. (Japan)

    2010-07-01

    Creep strength enhanced ferritic steels, such as T91 and T23 are extensively used worldwide for superheater and reheater tubes, not only in advanced power plants but also in plants with conventional steam conditions. However when these steel tubes are used at higher metal temperature, steam oxidation problems are recently experienced resulting in turbine side erosion, and overheating of tubes leading to creep rupture due to scale blockage in tube bends or scale insulation effect due to thick scale, and separation and exfoliation of the scale. In the present study, steam oxidation growth tests of T91, T92, T23 and T22 were conducted to develop steam oxidation growth rate and scale behavior. Then using the steam oxidation growth data measured the metal temperature changes with scale growth were calculated considering the insulation effect of steam oxidation scale. Consequently the creep lives affected by steam oxidation scale growth were predicted as a function of time and temperature increase for creep strength enhanced ferritic steels. (orig.)

  10. Annealing of a ferritic stainless steel 409 stabilized with titanium and zirconium additions

    Directory of Open Access Journals (Sweden)

    Zambrano, P.

    2011-02-01

    Full Text Available A ferritic stainless steel 409 stabilized with titanium and zirconium was subject to thermomechanical processing. It was heated at 1210 °C for one hour, followed by a 75 % hot reduction in three passes, this rolling schedule ended at 980 °C. Samples were cooled to 600 °C by water spraying followed by air-cooling. The alloy was pickled, and was reduced 80 % by cold rolling. The alloy was annealed at different temperatures for 105 s. Additional annealing treatments were carried out at temperatures of 800, 850 and 900 °C for different times. Mechanical testing and texture were made to corroborate the degree of annealing and formability. Mechanical properties and Texture analyses showed that the alloy annealed at 850 °C for 14 min was both completely recrystallized and a very good formability.

    Un acero inoxidable ferrítico 409 estabilizado con titanio y zirconio fue sujeto a procesos termomecánicos. El acero fue calentado a 1210 ºC durante una hora, seguido por un laminado en caliente del 75 % en tres pases, el proceso terminó a los 980 ºC. Las muestras fueron enfriadas hasta 600 ºC por agua atomizada seguido de enfriamiento al aire. La aleación fue decapada y laminada en frío un 80 %. Posteriormente de desarrollaron tratamientos térmicos de recocido a diferentes temperaturas por un tiempo de 105 s. Adicionalmente se desarrollaron tratamientos de recocido a temperaturas de 800, 850 y 900 ºC a diferentes tiempos. Pruebas mecánicas y textura fueron realizadas para corroborar el grado de recocido y su formalidad. El análisis de las propiedades mecánicas y la Textura mostraron que la aleación recocida a 850 ºC por 14 min (840 s fue completamente recristalizada obteniendo la mejor formabilidad.

  11. Corrosion test of the ferritic-martensitic steel (Gr. 91) in molten Pb.Li

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yang Il; Park, Jeong Yong; Choi, Byoung Kwon; Jeong, Yong Hwan; Lee, Dong Won [Nuclea Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cho, Seung Yon [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    Design concepts for tritium breeding blankets for DEMO and/or fusion power plants are going to be tested by using various types of TBMs (test blanket modules) in ITER. Two TBM systems are proposed by Korea, i.e. a helium-cooled solid breeder (HCSB) blanket and a helium-cooled molten lithium (HCML) blanket, among several candidates. Both the TBMs consist of a ferritic-martensitic steel (FMS) as a structural material. In particular, FMS contacts with flowing molten metals (Pb.Li or Li) during the operation in the case of HCML blanket. Since FMS is corrosive in a Pb.Li solution, the compatibility of structural materials with breeder materials should be investigated. The compatibility of EUROFER with Pb.Li was tested at temperatures up to 550 .deg. C with PbLi flowing at up to 0.22 m/s for 5000 h in Europe. China performed corrosion tests of CLAM in experimental loops, such as the thermal convection Pb.Li loop (DRAGON I) at 450.500 .deg. C, the high-temperature thermal convection Pb.Li loop (DRAGON II) with up to 700 .deg. C. Japan also tested JLF alloys in the Li loop operated at up to 700 .deg. C. However, Korea does not have any developed FMS nor an experience of the corrosion test of FMS in a Pb.Li loop. The current study may be a first step to the compatibility test of TBM, although the test includes only a static Pb.Li melt

  12. Isothermal and thermomechanical fatigue studies on a modified 9Cr-1Mo ferritic martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Nagesha, A., E-mail: nagesh@igcar.gov.in [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Kannan, R. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Sastry, G.V.S. [Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Sandhya, R. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Singh, Vakil [Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Bhanu Sankara Rao, K. [School of Engineering Sciences and Technology, Central University, Hyderabad (India); Mathew, M.D. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2012-09-30

    In-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) tests were carried out on a modified 9Cr-1Mo ferritic martensitic steel under a mechanical strain control mode employing a strain amplitude of {+-}0.4%. Different temperature ranges in the interval, 573-923 K were employed for the tests which were carried out using a constant strain rate of 1.2 Multiplication-Sign 10{sup -4} s{sup -1}. Isothermal low cycle fatigue tests were also performed concurrently at the maximum temperatures (T{sub max}) of TMF tests on similar specimens and employing the same strain amplitude and strain rate. The life variation was seen to follow the sequence: IF < OP TMF < IP TMF. However, the difference in lives narrowed down with an increase in the T{sub max} of TMF/test temperature of IF cycling. The cyclic stress response behaviour of the alloy was characterized by a continuous softening under all testing conditions. The lower lives observed under OP TMF in comparison with IP cycling was attributed to a combined influence of oxide cracking and a higher tensile hysteresis loop energy in the former. Cyclic life under IP TMF was observed to reduce more drastically compared to OP cycling with increase in T{sub max}, owing to the increasing prominence of dynamic recovery effects coupled with creep deformation. Transmission electron microscopy (TEM) investigations revealed that IF cycling at the T{sub max} resulted in a significantly greater substructural recovery compared to that produced by TMF cycling as a consequence of which, the former led to lower lives compared to both the IP and OP TMF. Dynamic strain ageing (DSA) associated with serrated flow was observed as the deformation temperature under TMF cycling traversed the regime of 300-400 Degree-Sign C.

  13. Gap Analysis of Material Properties Data for Ferritic/Martensitic HT-9 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Neil R. [Los Alamos National Laboratory; Serrano De Caro, Magdalena [Los Alamos National Laboratory; Rodriguez, Edward A. [Global Nuclear Network Analysis, LLC

    2012-08-28

    The US Department of Energy (DOE), Office of Nuclear Energy (NE), is supporting the development of an ASME Code Case for adoption of 12Cr-1Mo-VW ferritic/martensitic (F/M) steel, commonly known as HT-9, primarily for use in elevated temperature design of liquid-metal fast reactors (LMFR) and components. In 2011, Los Alamos National Laboratory (LANL) nuclear engineering staff began assisting in the development of a small modular reactor (SMR) design concept, previously known as the Hyperion Module, now called the Gen4 Module. LANL staff immediately proposed HT-9 for the reactor vessel and components, as well as fuel clad and ducting, due to its superior thermal qualities. Although the ASME material Code Case, for adoption of HT-9 as an approved elevated temperature material for LMFR service, is the ultimate goal of this project, there are several key deliverables that must first be successfully accomplished. The most important key deliverable is the research, accumulation, and documentation of specific material parameters; physical, mechanical, and environmental, which becomes the basis for an ASME Code Case. Time-independent tensile and ductility data and time-dependent creep and creep-rupture behavior are some of the material properties required for a successful ASME Code case. Although this report provides a cursory review of the available data, a much more comprehensive study of open-source data would be necessary. This report serves three purposes: (a) provides a list of already existing material data information that could ultimately be made available to the ASME Code, (b) determines the HT-9 material properties data missing from available sources that would be required and (c) estimates the necessary material testing required to close the gap. Ultimately, the gap analysis demonstrates that certain material properties testing will be required to fulfill the necessary information package for an ASME Code Case.

  14. Effects of processing optimisation on microstructure, texture, grain boundary and mechanical properties of Fe–17Cr ferritic stainless steel thick plates

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jian, E-mail: jh595@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Li, Huijun; Zhu, Zhixiong [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Jiang, Laizhu; Xu, Haigang; Ma, Li [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China)

    2014-10-20

    The relationships between microstructure, texture, grain boundary and tensile strength, Charpy impact toughness of (Nb+Ti+V) stabilised Fe–17Cr ferritic stainless steel thick plates were investigated by means of optical microscopy, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, tensile and Charpy impact testing. The results show that for Fe–17Cr ferritic stainless steel thick plate, the addition of warm rolling procedure leads to refinement of grain size, modification of texture, and then optimisation of grain boundary, including grain boundary character distribution and grain boundary connectivity. Meanwhile, the mechanical testing results indicate that optimal transformation that warm rolling procedure brings to Fe–17Cr ferritic steel thick plate is beneficial to its mechanical properties.

  15. Phase transformation and impact properties in the experimentally simulated weld heat-affected zone of a reduced activation ferritic/martensitic steel

    International Nuclear Information System (INIS)

    In this work, the phase transformation and impact properties in the weld heat-affected zone (HAZ) of a reduced activation ferritic/martensitic (RAFM) steel are investigated. The HAZs were experimentally simulated using a Gleeble simulator. The base steel consisted of tempered martensite through normalizing at 1000 °C and tempering at 750 °C, while the HAZs consisted of martensite, δ-ferrite and a small volume of autotempered martensite. The impact properties using a Charpy V-notch impact test revealed that the HAZs showed poor impact properties due to the formation of martensite and δ-ferrite as compared with the base steel. In addition, the impact properties of the HAZs further deteriorated with an increase in the δ-ferrite fraction caused by increasing the peak temperature. The impact properties of the HAZs could be improved through the formation of tempered martensite after post weld heat treatment (PWHT), but they remained lower than that of the base steel because the δ-ferrite remained in the tempered HAZs

  16. Phase transformation and impact properties in the experimentally simulated weld heat-affected zone of a reduced activation ferritic/martensitic steel

    Science.gov (United States)

    Moon, Joonoh; Lee, Chang-Hoon; Lee, Tae-Ho; Jang, Min-Ho; Park, Min-Gu; Han, Heung Nam

    2014-12-01

    In this work, the phase transformation and impact properties in the weld heat-affected zone (HAZ) of a reduced activation ferritic/martensitic (RAFM) steel are investigated. The HAZs were experimentally simulated using a Gleeble simulator. The base steel consisted of tempered martensite through normalizing at 1000 °C and tempering at 750 °C, while the HAZs consisted of martensite, δ-ferrite and a small volume of autotempered martensite. The impact properties using a Charpy V-notch impact test revealed that the HAZs showed poor impact properties due to the formation of martensite and δ-ferrite as compared with the base steel. In addition, the impact properties of the HAZs further deteriorated with an increase in the δ-ferrite fraction caused by increasing the peak temperature. The impact properties of the HAZs could be improved through the formation of tempered martensite after post weld heat treatment (PWHT), but they remained lower than that of the base steel because the δ-ferrite remained in the tempered HAZs.

  17. Theoretical modelling of iron nitriding coupled with a nanocrystallisation treatment. Application to numerical predictions for ferritic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Panicaud, B., E-mail: benoit.panicaud@utt.fr [ICD-LASMIS, Universite de Technologie de Troyes (UTT), UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); Chemkhi, M.; Roos, A.; Retraint, D. [ICD-LASMIS, Universite de Technologie de Troyes (UTT), UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France)

    2012-06-15

    This paper analyses a recently developed duplex process combining nitriding with nanocrystallisation. A model is proposed to show how nitrogen diffusion mechanisms are modified within ferritic steels due to the nanostructure near the top surface. This model is based on micro-mechanical and micro-physical approaches, and also on the thermodynamics of irreversible processes. It takes into account size effects influencing the nitrogen diffusion, including mechanical stresses at the different length scales. Several models are investigated and numerical applications are performed. The results are compared to literature in order to demonstrate the generality of the present methodology.

  18. Evaluation of the material in creep-exposed critical 12Cr-1Mo-V ferritic steel components of the pressure section of power plant steam boilers

    International Nuclear Information System (INIS)

    Metallographic examinations were carried out on ferritic 12Cr-1Mo-V steel with tempered martensite structure after 68,000 - 145,000 hr service in creep conditions. Structural evolution related to the form of martensite, carbide precipitation and internal damage due to long-term action of thermally activated processes was discussed. A generalised scheme of structural evolution and progress of the internal damage was developed in correlation with the life exhaustion ratio. Principles of the classification for ferritic 12Cr-1Mo-V steel after long-term-service were proposed together with the method for evolution of the state of the material for the industrial practice. (author)

  19. Improvement of mechanical properties in a forging microalloyed steel throughout the control of the anisothermal decomposition of austenite into acicular ferrite

    International Nuclear Information System (INIS)

    The aim of this work is to study the anisothermal decomposition of austenite at two different austenisation conditions in a medium carbon microalloyed steel. In this sense, continuous cooling transformation diagrams (CCT) have been obtained for both austenisation conditions to determine the continuous cooling that allows the formation of a microstructure mainly formed of acicular ferrite the best mechanical properties. The knowledge of the anisothermal decomposition of austenite in this steel has allowed to propose continuous cooling cycles for industrial application. That produce high volume fraction of acicular ferrite. (Author) 17 refs

  20. Effect of Processing Condition on Texture and Drawability of a Ferritic Rolled and Annealed Interstitial-Free Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Zhao-dong; GUO Yan-hui; ZHAO Zhong; LIU Xiang-hua; WANG Guo-dong

    2006-01-01

    The processing conditions of the texture formation and deep drawability of a Ti-IF steel strip hot-rolled in ferritic region and subsequently annealed were investigated. The r-value increases with the decrease of reheating temperature, and finish rolling temperature and the increase of reductions in ferritic region. For lubricated ferritic rolling and annealing, the r-value is raised up to 1.75, and elongation rate is over 50% at the finish rolling temperature of 650 ℃, which is suitable for DDQ grade products. However, the r-value is below 1.0 in the case of unlubricated rolling. The X-ray diffraction was used to analyze the textural characteristic of samples. For samples subjected to lubricated rolling and annealing, the strong {111}∥ND recrystallization texture is distributed homogeneously along the thickness direction, and the intensity of {110} recrystallization texture is very low even in surface. However, for unlubricated samples, the {111} texture is distributed inhomogeneously and is weak along the thickness direction, and {110}∥ND recrystallization texture is strong, which deteriorates the formability.

  1. EBSD as a tool to identify and quantify bainite and ferrite in low-alloyed Al-TRIP steels.

    Science.gov (United States)

    Zaefferer, S; Romano, P; Friedel, F

    2008-06-01

    Bainite is thought to play an important role for the chemical and mechanical stabilization of metastable austenite in low-alloyed TRIP steels. Therefore, in order to understand and improve the material properties, it is important to locate and quantify the bainitic phase. To this aim, electron backscatter diffraction-based orientation microscopy has been employed. The main difficulty herewith is to distinguish bainitic ferrite from ferrite because both have bcc crystal structure. The most important difference between them is the occurrence of transformation induced geometrically necessary dislocations in the bainitic phase. To determine the areas with larger geometrically necessary dislocation density, the following orientation microscopy maps were explored: pattern quality maps, grain reference orientation deviation maps and kernel average misorientation maps. We show that only the latter allow a reliable separation of the bainitic and ferritic phase. The kernel average misorientation threshold value that separates both constituents is determined by an algorithm that searches for the smoothness of the boundaries between them. PMID:18503676

  2. Evolution of the mechanical properties and microstructure of ferritic-martensitic steels irradiated in the BOR-60 reactor

    Science.gov (United States)

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

    2002-12-01

    The effect of neutron irradiation on mechanical properties of low-activation ferritic-martensitic (FM) steels 0.1C-9Cr-1W, V, Ta, B and 0.1C-12Cr-2W, V, Ti, B is studied under tension at temperatures of 330-540 °C and doses of 50 dpa. Steel 0.1C-13Cr-Mo, V, Nb, B was chosen for comparison. At irradiation temperatures of 330-340 °C, the radiation hardening of steel with 9%Cr achieves saturation at a dose of 10 dpa. In this case as compared to steels with 12%Cr, the fracture surface is characterized as ductile without cleavage traces. At irradiation temperatures higher than 420 °C, there is no difference in the behavior of the materials under investigation. The data on radiation creep obtained by direct measurement and from the profilometry data satisfy a model ɛ¯/ σ¯=B 0+D Ṡ, when B0 and D have the values typical for steels of FM type.

  3. Impact Strength of Austenitic and Ferritic-Austenitic Cr-Ni Stainless Cast Steel in -40 and +20°C Temperature

    Directory of Open Access Journals (Sweden)

    Kalandyk B.

    2014-10-01

    Full Text Available Studies described in this paper relate to common grades of cast corrosion resistant Cr-Ni steel with different matrix. The test materials were subjected to heat treatment, which consisted in the solution annealing at 1060°C followed by cooling in water. The conducted investigations, besides the microstructural characteristics of selected cast steel grades, included the evaluation of hardness, toughness (at a temperature of -40 and +20oC and type of fracture obtained after breaking the specimens on a Charpy impact testing machine. Based on the results of the measured volume fraction of ferrite, it has been found that the content of this phase in cast austenitic steel is 1.9%, while in the two-phase ferritic-austenitic grades it ranges from 50 to 58%. It has been demonstrated that within the scope of conducted studies, the cast steel of an austenitic structure is characterised by higher impact strength than the two-phase ferritic-austenitic (F-A grade. The changing appearance of the fractures of the specimens reflected the impact strength values obtained in the tested materials. Fractures of the cast austenitic Cr-Ni steel obtained in these studies were of a ductile character, while fractures of the cast ferritic-austenitic grade were mostly of a mixed character with the predominance of brittle phase and well visible cleavage planes.

  4. Development and Production of Ultra Purity Ferritic Stainless Steel%超纯铁素体不锈钢研制和生产

    Institute of Scientific and Technical Information of China (English)

    魏明; 吴殿杰; 张佳秋

    2012-01-01

    Due to extremely 16w carbon and nitrogen content, the ultra purity ferritic stainless steel has more preferable corrosion resistance, toughness and weldability than the ordinary ferritic stainless steel and martensite stainless steel. The range of applications and development tendency for ultra purity ferritic stainless steel were presented. The casting process of the ultra purity ferritic stainless steel castings was described, and the market forecasting and economic benefit was analyzed.%超纯铁素体不锈钢因碳、氮含量极低,较普通铁素体不锈钢以及马氏体不锈钢拥有更优越的耐腐蚀性、韧性及焊接性。介绍了超纯铁素体不锈钢的应用范围和发展趋势,阐述了超纯铁素体不锈钢铸件的生产工艺,并对其进行了市场预测和经济效益分析。

  5. Production and preliminary characterization of ferritic-martensitic steel T91 cladding tubes for LBE or Pb cooled nuclear systems

    Science.gov (United States)

    Van den Bosch, J.; Almazouzi, A.; Mueller, G.; Rusanov, A.

    2011-08-01

    Thin wall tubes with suitable dimensions for possible future use as nuclear fuel cladding based on ferritic-martensitic steel T91 have been produced. Several rolling routes for thin wall tube rolling have been successfully explored to produce T91 tubes of 8.5 mm OD and 0.5 mm wall thickness as well as 6.5 mm OD and 0.5 mm wall thickness. The results show that the cold rolled Т91 steel thin walled tubes remain ductile and the material easily carries fractional strains. Finally the microstructure of the resulting tubes was examined and preliminary burst and tensile tests were performed showing properties comparable to those of T91 plate material.

  6. Measurement of internal stresses in a welded assembly made of 20 MND 53 ferritic steel. Stress relaxation

    International Nuclear Information System (INIS)

    An assembly consisting of two flanged plates welded end to end was realized, the plates being made of 20 MND 53 ferritic steel. This grade of steel is used to fabricate PWR reactor vessels. At each important stage in the realization of the assembly, internal stresses were measured by X-ray diffraction techniques. These measurements showed that the finished realization manifested compression stresses in the main parts of its structure and large amplitude tensile stresses in the central weld seam. A heat treatment was performed (6150C - 17 hours). Stresses levels almost every where in the assembly dropped to practically zero. Although stress relaxation kinetics are probably slower in voluminous parts, this result and most of the results published in literature on this subject, indicate that such treatment notably diminishes internal welding stress even in thick parts

  7. Numerical evaluation of the weldability of the low alloy ferritic steels T/P23 and T/P24

    Directory of Open Access Journals (Sweden)

    Carlos Roberto Xavier

    2011-03-01

    Full Text Available A model based on transport equations was numerically implemented by the finite volume method (FVM in a computational code in order to simulate the influence of the heat input, base metal thickness and preheating temperature on the thermal evolution and the cooling rate during the welding of the low alloy ferritic steels T/P23 and T/P24. As a consequence, it was possible to evaluate qualitatively the microstructure at the heat affected zone (HAZ of these steels when a single weld bead was deposited on their surface and calculate the maximum hardness reached at this region. Goldakfs double-ellipsoid heat source model for power density distribution was utilized in order to obtain a good estimate of the cooling rate and dimensions of the fusion zone (FZ. The results are discussed in light of previous work and good agreement between experimental and simulated results was verified.

  8. Standard test method for conducting drop-weight test to determine nil-ductility transition temperature of ferritic steels

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 This test method covers the determination of the nil-ductility transition (NDT) temperature of ferritic steels, 5/8 in. (15.9 mm) and thicker. 1.2 This test method may be used whenever the inquiry, contract, order, or specification states that the steels are subject to fracture toughness requirements as determined by the drop-weight test. 1.3 The values stated in inch-pound units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  9. HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Wei [ORNL; Chen, Gaoqiang [ORNL; Chen, Jian [ORNL; Yu, Xinghua [ORNL; Frederick, David Alan [ORNL; Feng, Zhili [ORNL

    2015-01-01

    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  10. Characterization of perovskite film prepared by pulsed laser deposition on ferritic stainless steel using microscopic and optical methods

    Science.gov (United States)

    Durda, E.; Jaglarz, J.; Kąc, S.; Przybylski, K.; El Kouari, Y.

    2016-06-01

    The perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF48) film was deposited on Crofer 22 APU ferritic stainless steel by pulsed laser deposition (PLD). Morphological studies of the sample were performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Information about film thickness and surface topography of the film and the steel substrate were obtained using following optical methods: spectroscopic ellipsometry (SE), bidirectional reflection distribution function (BRDF) and total integrated reflectometry (TIS). In particular, the BRDF study, being complementary to atomic force microscopy, yielded information about surface topography. Using the previously mentioned methods, the following statistic surface parameters were determined: root-mean square (rms) roughness and autocorrelation length by determining the power spectral density (PSD) function of surface irregularities.

  11. Factors Affecting the Inclusion Potency for Acicular Ferrite Nucleation in High-Strength Steel Welds

    Science.gov (United States)

    Kang, Yongjoon; Jeong, Seonghoon; Kang, Joo-Hee; Lee, Changhee

    2016-06-01

    Factors affecting the inclusion potency for acicular ferrite nucleation in high-strength weld metals were investigated and the contribution of each factor was qualitatively evaluated. Two kinds of weld metals with different hardenabilities were prepared, in both, MnTi2O4-rich spinel formed as the predominant inclusion phase. To evaluate the factors determining the inclusion potency, the inclusion characteristics of size, phase distribution in the multiphase inclusion, orientation relationship with ferrite, and Mn distribution near the inclusion were analyzed. Three factors affecting the ferrite nucleation potency of inclusions were evaluated: the Baker-Nutting (B-N) orientation relationship between ferrite and the inclusion; the formation of an Mn-depleted zone (MDZ) near the inclusion; and the strain energy around the inclusion. Among these, the first two factors were found to be the most important. In addition, it was concluded that the increased chemical driving force brought about by the formation of an MDZ contributed more to the formation of acicular ferrite in higher-strength weld metals, because the B-N orientation relationship between ferrite and the inclusion was less likely to form as the transformation temperature decreased.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-12-31

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

  13. Recent activities on the compatibility of the ferritic steel wall with the plasma in the JFT-2M tokamak

    Science.gov (United States)

    Tsuzuki, K.; Sato, M.; Kawashima, H.; Isei, N.; Kimura, H.; Ogawa, H.; Miyachi, K.; Yamamoto, M.; Shibata, T.

    2002-12-01

    The compatibility of the low activation ferritic steel with a fusion plasma has been investigated in the JFT-2M tokamak. The program consists of three stages. In the first stage, the reduction of fast ion losses was well demonstrated by ferritic steel plates (FPs) outside the vacuum vessel (VV). In the second stage, 20% of the inner surface of the VV was covered by the FPs. The plasma control, stability, and impurity release were preliminary investigated. No deteriorative effect on the plasma was observed at least in the following conditions: partial covering of 20% and the normalized beta value less than 2.8. First boronization was applied to JFT-2M leading to a remarkable decrease of the oxygen impurity. After the boronization, plasmas with the highest normalized beta in JFT-2M were obtained. Thus encouraging results were gained for this stage. In the third stage, the VV was fully covered by FPs, where the ripple reduction and the plasma stability will be investigated as a full scale testing.

  14. Thermally grown oxide films and corrosion performance of ferritic stainless steels under simulated exhaust gas condensate conditions

    International Nuclear Information System (INIS)

    Highlights: • Five ferritic stainless steels with dissimilar composition included. • Thermal oxide films and performance under exhaust gas condensate conditions studied. • Oxide films grown at 300 and 600 °C show differences in structure and properties. • Performance of alloys with >11.5 wt.% Cr is related to elements Ti, Si, Nb and Mo. • Compositional optimization requires knowledge on several linked processes. - Abstract: Five ferritic stainless steels are characterized in terms of thermally grown oxide films and corrosion performance under simulated exhaust gas condensate conditions. Oxide films developed at 300 °C show only little variation in microstructure and properties between the alloys, whereas those evolved at 600 °C exhibit clear differences. Especially in alloys with >11.5 wt.% chromium, the presence and distribution of such alloying elements as titanium, silicon, niobium and molybdenum are crucial for the film properties and the overall corrosion performance. The results may be exploited in the compositional optimization of the alloys for the cold-end components of automotive exhaust system

  15. Evaluation of Charpy impact properties and fracture toughness for irradiated ferritic steels (3)

    International Nuclear Information System (INIS)

    Four kinds of ferritic steels, 61FK, 61FS, ASTM A213T9 (F9S) and NSCR9, were irradiated in SMIR-10 at 823 K to (3.2-9.0)x1026 n/m2 (E > 0.1 MeV) and subjected to instrumented Charpy impact tests. The absorbed energy, dynamic yield and maximum loads, brittle fracture load and the deflection to brittle fracture were measured as a function of test temperature and the ductile-to-brittle transition temperature (DBTT) and the upper shelf energy (USE) were evaluated. For the test, Charpy V-notch specimens, JIS-4, were used which had the dimensions of 10x2x55 mm and the V-notch geometry of notch root radius of 0.25 mm, notch of 2 mm and notch angle of 45 degrees. Main results obtained are as follows. 1) The DBTT was less dependent on neutron dose. The DBTT for the higher dose of (8.8-9.0)-1026 n/m2 increased in the order of 61FK, NSCR9, 61FS and F9S. 2) As the neutron dose increased, the USE decreased for 61FK, while it stayed almost constant for 61GS and increased for F9S. The USE for the higher dose decreased in the order of 61FK, NSCR9, 61FS and F9S, which was the same as the increasing order of DBTT. 3) The DBTT shifts, ΔDBTT, due to irradiation with the higher dose level increased in the order of 61FK, 61FS and NSCR9, except for F9S, where the DBTT in the unirradiated state is not available. 4) The change in USE, ΔUSE, due to irradiation with the higher dose increased in the order of 61FS, 61FK and NSCR9, except for F9S. 5) Comparison of the present results with the previous ones irradiated at 723K in SMIR-10 showed that 823K irradiation caused considerably larger embrittlement than 723K irradiation, especially for F9S and 61FK. (author)

  16. Studies on oxidation and deuterium permeation behavior of a low temperature α-Al2O3-forming Fesbnd Crsbnd Al ferritic steel

    Science.gov (United States)

    Xu, Yu-Ping; Zhao, Si-Xiang; Liu, Feng; Li, Xiao-Chun; Zhao, Ming-Zhong; Wang, Jing; Lu, Tao; Hong, Suk-Ho; Zhou, Hai-Shan; Luo, Guang-Nan

    2016-08-01

    To evaluate the capability of Fesbnd Crsbnd Al ferritic steels as tritium permeation barrier in fusion systems, the oxidation behavior together with the permeation behavior of a Fesbnd Crsbnd Al steel was investigated. Gas driven permeation experiments were performed. The permeability of the oxidized Fesbnd Crsbnd Al steel was obtained and a reduced activation ferritic/martensitic steel CLF-1 was used as a comparison. In order to characterize the oxide layer, SEM, XPS, TEM, HRTEM were used. Al2O3 was detected in the oxide film by XPS, and HRTEM showed that Al2O3 in the α phase was found. The formation of α-Al2O3 layer at a relatively low temperature may result from the formation of Cr2O3 nuclei.

  17. Oxidation behavior of ferritic-martensitic and ODS steels in supercritical water

    Science.gov (United States)

    Bischoff, Jeremy

    water corroded much faster than those in steam (1.5 to 2 times faster). Additionally, during these corrosion tests a marker experiment was performed with the deposition of micrometric palladium markers on the surface of some samples prior to oxidation. The markers were found at the outer-inner layer interface, consistent with a corrosion mechanism of outward migration of iron to form the outer layer and inward migration of oxygen to form the inner layer. The discrepancy between the SCW and steam environments suggests that the outward migration of iron may be the rate-limiting step. A detailed study of the oxide advancement was performed using the TEM by analyzing the inner and diffusion layer structure. Energy-filtered TEM images were acquired to analyze the micrometric and nanometric distribution of elements in these layers. Such images from the inner layer revealed the presence of localized chromium enrichment regions associated with the presence of pores. Additionally, an iron-chromium nanometric segregation was observed and may be associated with the mixture of Fe3O4 and FeCr2O4. In the diffusion layer, small nanometric chromium-rich oxide particles were seen within metal grains. The (Fe,Cr)3O4 spinel oxide has an inverse spinel structure as Fe3O4 but becomes normal spinel as FeCr 2O4, thus the structure changes depending on the chromium content. Additionally, the spinel structure was analyzed using the ligand theory and showed that chromium does not migrate and that the main diffusing species is the Fe2+ ion. Calculations of the amount of iron leaving the inner layer showed that this amount accounted for the amount of iron necessary to form the outer layer, thus no dissolution of oxide in SCW is observed. Additionally, the differences in oxidation behavior in steam and SCW suggest that the rate-limiting step for the corrosion of ferritic-martensitic steels is the iron outward migration. The iron migration is driven by the gradient in the Fe2+/Fe 3+ ratio and is

  18. Effect of joining temperature on the microstructure and strength of tungsten/ferritic steel joints diffusion bonded with a nickel interlayer

    OpenAIRE

    Zhong, Zhihong; Jung, Hun-chea; Hinoki, Tatsuya; KOHYAMA, Akira

    2010-01-01

    A diffusion bonding process, for joining of tungsten to ferritic steel using nickel as an interlayer, was developed for nuclear component application. The effect of joining temperature on the microstructure and tensile strength of the joint was investigated in this work. Metallographic analysis revealed that a good bonding was obtained at both the tungsten/nickel and nickel/steel interfaces, and the diffusion products were identified in the diffusion zone. Nano-indentation test across the joi...

  19. Investigations on Laser Beam Welding Dissimilar Material Combinations of Austenitic High Manganese (FeMn) and Ferrite Steels

    Science.gov (United States)

    Behm, Velten; Höfemann, Matthias; Hatscher, Ansgar; Springer, André; Kaierle, Stefan; Hein, David; Otto, Manuel; Overmeyer, Ludger

    For the past few years the customer's demand for more fuel efficient and at the same time safer vehicles has steadily increased. Consequently, light weight design has become one of the main interests in engineering. With regard to sheet metal components, a new class of high manganese steels, based on the TWIP (twinning induced plasticity) effect, provides the opportunity of shaping light weight designedthin and complex sheet metal geometries with advanced crash performance. In terms of weldability, due to their thermo-physical properties (high content of C, Mn, Al, Si), FeMn steels have to be handled differently in comparison to conventional steel grades. Particularly dissimilar material combinations of FeMn and ferrite steels are in the center of interest for industrial applications. This study reveals that metallurgical properties of dissimilar welding seams can be influenced considerably by laser beam welding, resulting in a change of the mechanical properties of the seam which is practicable without using filler material as described in (Flügge et al., 2011).

  20. Investigation of iron-chromium-niobium-titanium ferritic stainless steel for solid oxide fuel cell interconnect applications

    Science.gov (United States)

    Yang, Zhenguo; Xia, Guan-Guang; Wang, Chong-Min; Nie, Zimin; Templeton, Joshua; Stevenson, Jeffry W.; Singh, Prabhakar

    As part of an effort to develop cost-effective ferritic stainless steel-based interconnects for solid oxide fuel cell (SOFC) stacks, both bare AISI441 and AISI441 coated with (Mn,Co) 3O 4 protection layers were studied in terms of its metallurgical characteristics, oxidation behavior, and electrical performance. The addition of minor alloying elements, in particular Nb, led to formation of Laves phases both inside grains and along grain boundaries. In particular, the Laves phase which precipitated out along grain boundaries during exposure at intermediate SOFC operating temperatures was found to be rich in both Nb and Si. The capture of Si in the Laves phase minimized the Si activity in the alloy matrix and prevented formation of an insulating silica layer at the scale/metal interface, resulting in a reduction in area-specific electrical resistance (ASR). However, the relatively high oxidation rate of the steel, which leads to increasing ASR over time, and the need to prevent volatilization of chromium from the steel necessitates the application of a conductive protection layer on the steel. In particular, the application of a Mn 1.5Co 1.5O 4 spinel protection layer substantially improved the electrical performance of the 441 by reducing the oxidation rate.

  1. Study of the first stages of oxidation of a ferritic-martensitic steel Fe-12Cr in CO2

    International Nuclear Information System (INIS)

    In the framework of the development of Sodium Fast Reactors in France, supercritical carbon dioxide integrated in the Brayton cycle is proposed as new cycle energy conversion system to replace current steam generators. Ferritic-Martensitic steels with 9-12 wt% Cr are good candidates for heat exchanger application because they have good mechanical properties up to a temperature of 600 C, a high thermal conductivity, a low coefficient of thermal expansion and a lower cost than that of austenitic steels. However, it has been found that these steels present a high parabolic oxide growth rate and a strong carburization in the temperature and pressure conditions of the SC-CO2 cycle (550 C, 250 bar). This study aims to investigate the influence of different parameters (impurities present in CO2, thermal ramp rate and surface state) on the oxidation mechanism of a Fe-12 Cr steel in CO2 at 550 C. It has been shown that depending on these parameters, a thin protective oxide scale without any strong carburization can be obtained. A model is proposed to explain the experimental results. (author)

  2. Microstructural evolution of ferritic-martensitic steels under heavy ion irradiation

    Science.gov (United States)

    Topbasi, Cem

    Ferritic-martensitic steels are primary candidate materials for fuel cladding and internal applications in the Sodium Fast Reactor, as well as first-wall and blanket materials in future fusion concepts because of their favorable mechanical properties and resistance to radiation damage. Since microstructure evolution under irradiation is amongst the key issues for these materials in these applications, developing a fundamental understanding of the irradiation-induced microstructure in these alloys is crucial in modeling and designing new alloys with improved properties. The goal of this project was to investigate the evolution of microstructure of two commercial ferritic-martensitic steels, NF616 and HCM12A, under heavy ion irradiation at a broad temperature range. An in situ heavy ion irradiation technique was used to create irradiation damage in the alloy; while it was being examined in a transmission electron microscope. Electron-transparent samples of NF616 and HCM12A were irradiated in situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with 1 MeV Kr ions to ˜10 dpa at temperatures ranging from 20 to 773 K. The microstructure evolution of NF616 and HCM12A was followed in situ by systematically recording micrographs and diffraction patterns as well as capturing videos during irradiation. In these irradiations, there was a period during which no changes are visible in the microstructure. After a threshold dose (˜0.1 dpa between 20 and 573 K, and ˜2.5 dpa at 673 K) black dots started to become visible under the ion beam. These black dots appeared suddenly (from one frame to the next) and are thought to be small defect clusters (2-5 nm in diameter), possibly small dislocation loops with Burgers vectors of either ½ or . The overall density of these defect clusters increased with dose and saturated around 6 dpa. At saturation, a steady-state is reached in which defects are eliminated and created at the same rates so that the

  3. An Investigation of the Massive Transformation from Ferrite to Austenite in Laser-Welded Mo-Bearing Stainless Steels

    Science.gov (United States)

    Perricone, M. J.; Dupont, J. N.; Anderson, T. D.; Robino, C. V.; Michael, J. R.

    2011-03-01

    A series of 31 Mo-bearing stainless steel compositions with Mo contents ranging from 0 to 10 wt pct and exhibiting primary δ-ferrite solidification were analyzed over a range of laser welding conditions to evaluate the effect of composition and cooling rate on the solid-state transformation to γ-austenite. Alloys exhibiting this microstructural development sequence are of particular interest to the welding community because of their reduced susceptibility to solidification cracking and the potential reduction of microsegregation (which can affect corrosion resistance), all while harnessing the high toughness of γ-austenite. Alloys were created using the arc button melting process, and laser welds were prepared on each alloy at constant power and travel speeds ranging from 4.2 to 42 mm/s. The cooling rates of these processes were estimated to range from 10 K (°C)/s for arc buttons to 105 K (°C)/s for the fastest laser welds. No shift in solidification mode from primary δ-ferrite to primary γ-austenite was observed in the range of compositions or welding conditions studied. Metastable microstructural features were observed in many laser weld fusion zones, as well as a massive transformation from δ-ferrite to γ-austenite. Evidence of epitaxial massive growth without nucleation was also found when intercellular γ-austenite was already present from a solidification reaction. The resulting single-phase γ-austenite in both cases exhibited a homogenous distribution of Mo, Cr, Ni, and Fe at nominal levels.

  4. Improvement of mechanical properties in a dual-phase ferrite–martensite AISI4140 steel under tough-strong ferrite formation

    International Nuclear Information System (INIS)

    Highlights: • The dual phase microstructure consists of ferrite and martensite microphases. • The ferrite morphology and hardness are variable in the DP microstructures. • Tough-strong continuous grain boundary ferrite has been formed. - Abstract: This paper has been concerned to investigate in details the mechanical properties of AISI4140 heat treatable steel under ferrite–martensite dual-phase (DP) microstructures in conjunction with that of conventional quench-tempered (CQT) full martensitic condition. For this purpose, a wide variety of ferrite–martensite DP samples containing different volume fractions of ferrite and martensite microphases have been developed using step quenching heat treatment processes at 600 °C for 20–55 s holding times with the subsequent hot oil quenching after being austenitized at 860 °C for 60 min in the same situation as to the CQT condition. The finalized tempering heat treatment has been carried out at 600 °C for 30 min for both of direct quenched full martensitic and DP samples in order to optimize the strength–ductility combination. Light and electron microscopes have been used in conjunction with mechanical tests to assess the structure–property relationships in the DP and CQT heat treated samples. The experimental results indicate that the DP microstructures consisting about 7% volume fraction of fine grain boundary ferrite in the vicinity of martensite are associated with excellent mechanical properties in comparison to that of CQT condition. These observations are rationalized in terms of higher carbon concentration of the remaining metastable austenite leading to the harder martensite formation on the subsequent hot oil quenching, and so developing much harder ferrite grains as a consequence of more constraints induced in the ferrite grains during martensitic phase transformation in the remaining austenite adjacent to the ferrite area. The higher martensite volume fraction in the vicinity of thin continuous

  5. Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Rieken, Joel [Iowa State Univ., Ames, IA (United States)

    2011-12-13

    Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

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

    Science.gov (United States)

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

    2016-10-01

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

  7. End Closure Joining of Ferritic-Martensitic and Oxide-Dispersion Strengthened Steel Cladding Tubes by Magnetic Pulse Welding

    Science.gov (United States)

    Lee, Jung-Gu; Park, Jin-Ju; Lee, Min-Ku; Rhee, Chang-Kyu; Kim, Tae-Kyu; Spirin, Alexey; Krutikov, Vasiliy; Paranin, Sergey

    2015-07-01

    The magnetic pulse welding (MPW) technique was employed for the end closure joining of fuel pin cladding tubes made of ferritic-martensitic (FM) steel and oxide-dispersion strengthened (ODS) steel. The technique is a solid-state impact joining process based on the electromagnetic force, similar to explosive welding. For a given set of optimal process parameters, e.g., the end-plug geometry, the rigid metallurgical bonding between the tube and end plug was obtained by high-velocity impact collision accompanied with surface jetting. The joint region showed a typical wavy morphology with a narrow grain boundary-like bonding interface. There was no evidence of even local melting, and only the limited grain refinement was observed in the vicinity of the bonding interface without destructing the original reinforcement microstructure of the FM-ODS steel, i.e., a fine grain structure with oxide dispersion. No leaks were detected during helium leakage test, and moreover, the rupture occurred in the cladding tube section without leaving any joint damage during internal pressure burst test. All of the results proved the integrity and durability of the MPWed joints and signified the great potential of this method of end closure joining for advanced fast reactor fuel pin fabrication.

  8. Dynamic finite element modeling of the effects of size on the upper shelf energy of ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sidener, S.E.; Kumar, A.S.; Schubert, L.E.; Hamilton, M.L.; Rosinski, S.T.

    1996-04-01

    Both the fusion and light water reactor program require the use of the subsize specimens to obtain sufficient irradiation data on neutron-induced embrittlement of ferritic steels. While the development of fusion-relevant size effects correlations can proceed analytically, it is more cost-effective at this time to use data currently being obtained on embrittlement of pressure vessel steels to test and expand the correlations developed earlier using fusion relevant steels. Dynamic finite elements modeling of the fracture behavior of fatigue-precracked Charpy Specimens was performed to determine the effect of single variable changes in ligament size, width, span, and thickness on the upper shelf energy. A method based on tensile fracture strain was used for modeling crack initiation and propagation. It was found that the upper shelf energy of precracked specimens (USE{sub p}) is proportional to b{sup n}, where b is ligament size and n varies from about 1.6 for subsize to 1.9 for full size specimens. The USE{sub p} was found to be proportional to width according to W{sup 25}. The dependence on thickness was found to be linear for all cases studied. Some of the data from the FEM analysis were compared with experimental data and were found to be in reasonable agreement.

  9. Irradiation creep in austenitic and ferritic steels irradiated in a tailored neutron spectrum to induce fusion reactor levels of helium

    Energy Technology Data Exchange (ETDEWEB)

    Grossbeck, M.L.; Gibson, L.T. [Oak Ridge National Laboratory, TN (United States); Jitsukawa, S.

    1996-04-01

    Six austenitic stainless steels and two ferritic alloys were irradiated sequentially in two research reactors where the neutron spectrum was tailored to produce a He production rate typical of a fusion device. Irradiation began in the Oak Ridge Research Reactor where an atomic displacement level of 7.4 dpa was achieved and was then transferred to the High Flux Isotope Reactor for the remainder of the irradiation to a total displacement level of 19 dpa. Temperatures of 60 and 330{degree}C are reported on. At 330{degree}C irradiation creep was found to be linear in stress and fluence with rates in the range of 1.7 - 5.5 x 10{sup -4}% MPa{sup -1} dpa{sup -1}. Annealed and cold-worked materials exhibited similar creep rates. There is some indication that austenitic alloys with TiC or TiO precipitates had a slightly higher irradiation creep rate than those without. The ferritic alloys HT-9 and Fe-16Cr had irradiatoin creep rates about 0.5 x 10{sup -4}% MPa{sup -1} dpa{sup -1}. No meaningful data could be obtained from the tubes irradiated at 60{degree}C because of damage to the tubes.

  10. Applications of niobium microalloyed ferrite pearlite steels to line pipe and plate

    International Nuclear Information System (INIS)

    A variety of advanced controlled rolling techniques have been developed to improve toughness, strength and weldability of niobium-steels. To achieve optimum properties, control of prior stage rolling conditions and accelerated cooling are needed. In low carbon steel, the addition of niobium results in a greater increase in tensile strength than that of vanadium without a loss of toughness. At the same strength level, niobium-steel has less susceptibility to weld cracking and good toughness in the HAZ of its weldments than similar vanadium steels. Separation and formability of niobium steels are also discussed

  11. In situ TEM study of the effect of M/A films at grain boundaries on crack propagation in an ultra-fine acicular ferrite pipeline steel

    International Nuclear Information System (INIS)

    Microstructural refinement of structural materials generally improves their tensile properties but deteriorates their fatigue properties. However, pipeline steels with ultra-fine acicular ferrite (UFAF) possess not only high strength and toughness, but also a low fatigue-crack-growth rate (FCGR) and long fatigue-propagation life. In this paper, the micro-fracture mechanisms of an UFAF pipeline steel are investigated by in situ tensile testing in a transmission electron microscope. The results indicate that a grain-boundary-film structure composed of martensite/austenite could significantly influence the crack propagating behavior in the UFAF steel, consequently lowering the FCGR by enhancing roughness-induced crack closure during cyclic loading

  12. Influence of the finish rolling temperatures on the microstructure and texture evolution in the ferritic stainless steels

    Institute of Scientific and Technical Information of China (English)

    Fei GAO; Zhen yu LIU; Haitao LIU; Guodong WANG

    2011-01-01

    The influence of the finish rolling temperature on the microstructure and texture evolution of Nb and B micro-alloyed ultra purified Cr17 ferritic stainless steels was investigated.The hot rolled bands were produced by conventional rolling process and the finish rolling at relatively low temperatures or “warm rolling”.The microstructure was observed by optical microscopy,scanning electron microscopy and transmission electron microscopy,and X-ray diffraction was used to characterize the texture evolution processes.The results showed that as compared to conventional hot rolling process,the warm rolling has led to the refined and homogeneous microstruc ture and uniform recrystallization texture along γ-fiber in final sheets,indicating that the finish rolling at relatively low temperatures can be the effective way to improve significantly the formability of final sheets.

  13. Patent Analysis of Ferritic/Martensitic Steels for the Fuel Cladding in Sodium-cooled Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jong Hyuk; Kim, Sung Ho; Kim, Tae Kyu; Kim, Woo Gon; Jang, Jin Sung; Kim, Dae Whan; Han, Chang Hee; Lee, Chan Bock

    2007-09-15

    The Korean, Japanese, U.S. and European patents related to the ferritic/martensitic steels were systematically surveyed to evaluate their patent status, which would be applicable to the fuel cladding materials for the Sodium-cooled Fast Reactor (SFR). From the surveys, totally 38 patents were finally selected for the quantitative and qualitative analysis. Among them, 28 patents (74%) were processed by Japanese companies and Sumitomo Metal industries Ltd. was top-ranked in the number (9) of priority patents. On the basis of these surveys, most patents could be applicable to the fuel cladding materials for SFR and, especially, some useful patents as the cladding were registered by the Russian and the Korean.

  14. Effect of molybdenum content on creep-rupture strength and toughness of 9 % chromium ferritic heat resisting steels containing V and Nb

    International Nuclear Information System (INIS)

    The effect of molybdenum content on creep-rupture properties and room-temperature toughness of high chromium ferritic heat resisting steels was investigated. Molybdenum content was varied from 1 to 2 wt%. In order to obtain 9Cr-Mo-V-Nb ferritic steels with both high creep-rupture strength and superior toughness, the amount of delta ferrite was controlled below 25 %, and the optimum tempering condition and mechanical properties after simulated welding have been investigated. The influence of molybdenum content on creep-rupture strength and Charpy absorbed energy was investigated with respect to the ratio of delta ferrite to tempered martensite, the precipitates, and the microstructures. Charpy absorbed energy of the 0.05C-9Cr-1Mo-0.15V-0.05Nb steel tempered at 800deg C and then heated at 600∼650deg C for 104 h was as high as 20∼30 kgf-m. By contrast, Charpy absorbed energy of 0.05C-9Cr-2Mo-0.15V-0.05Nb steel was reduced to about 4kgf-m after heating at 600∼650deg C for 104 h. It is considered that the steel of 1Mo shows superior toughness because of its low carbon content and a single phase of martensite. It was concluded that combination of superior creep-rupture strength and toughness can be obtained by optimum heat treatment for the 9Cr-1Mo-V-Nb steel containing 0.05 wt%C. (author)

  15. HOT ROLLING OF A FERRITIC STAINLESS STEEL IN A STECKEL MILL: THERMOMECHANICAL AND MICROSTRUCTURAL CARACTERIZATION AND MATHEMATICAL MODELLING OF THE EVOLUTION OF RECRYSTALLIZED VOLUME FRACTION OF FERRITE

    OpenAIRE

    Willy Schuwarten Júnior; Ronaldo Antônio Neves Marques Barbosa

    2013-01-01

    A thermomechanical and a microstructure caracterization and a mathematical model of the evolution of the recrystallized volume fraction of ferrite in hot rolling in a Steckel mill have been carried out here. The proposed model is able to reasonably predict the observed in hot rolling, that is, there is 100% recrystallization of ferrite after roughing and partial recrystallization only after finishing

  16. HOT ROLLING OF A FERRITIC STAINLESS STEEL IN A STECKEL MILL: THERMOMECHANICAL AND MICROSTRUCTURAL CARACTERIZATION AND MATHEMATICAL MODELLING OF THE EVOLUTION OF RECRYSTALLIZED VOLUME FRACTION OF FERRITE

    Directory of Open Access Journals (Sweden)

    Willy Schuwarten Júnior

    2013-10-01

    Full Text Available A thermomechanical and a microstructure caracterization and a mathematical model of the evolution of the recrystallized volume fraction of ferrite in hot rolling in a Steckel mill have been carried out here. The proposed model is able to reasonably predict the observed in hot rolling, that is, there is 100% recrystallization of ferrite after roughing and partial recrystallization only after finishing

  17. Production and qualification for fusion applications, a steel of low activity ferritic-martensitic ASTURFER; Produccion y cualificacion, para aplicaciones de fusion, de un acero de baja actividad ferritico-martensitico, ASTURFER

    Energy Technology Data Exchange (ETDEWEB)

    Moran, A.; Belzunce, J.; Artimez, J. M.

    2011-07-01

    This article details the work carried out in the design and development pilot plant scale of a steel ferritic-martensitic of reduced activity, Asturfer, with a chemical composition and metallurgical properties similar to steel Eurofer. We describe the different stages of steel production and the results of the characterizations made in the context of an extensive test program.

  18. Effects of V-notch dimensions on charpy impact test results for differently sized miniature specimens of ferritic steel

    International Nuclear Information System (INIS)

    In order to develop the small specimen technology in Charpy impact testing, the effects of V-notch dimensions on the test results were investigated for miniaturized specimens of a ferritic steel, Japanese Ferrite/Martensite Dual Phase Steel (JFMS). The miniaturized Charpy specimens had four different square cross-sections of 3.3, 2, 1.5 and 1 mm, and each of them had a variety of V-notch dimensions (notch depth, notch root radius and notch angle). All of the specimens were subjected to Charpy impact tests between 93 and 373 K using a specially instrumented impact machine. The fracture surfaces of all tested specimens were examined by scanning electron microscopy. The main results obtained are as follows: (1) The ductile-to-brittle transition temperature (DBTT) varied noticeably depending upon the notch dimensions, some of the DBTTs exceeding that of the full size specimens. (2) The DBTTs for the miniaturized specimens were uniquely defined by the elastic stress concentration factor, Kt, leading to an important aspect that the DBTT for the full size specimens can be directly obtained from the DBTT of the miniaturized specimens with a V-notch giving a suitable value of Kt. (3) The upper shelf energy (USE) was dependent only on notch depth or ligament size, indicating that the notch geometry was practically unimportant. When all of the measured USEs were normalized by Bb2 or (Bb)3/2 (B is the specimen thickness, b the ligament size), the normalized USEs of the miniaturized specimens agreed with that of the full size specimens within the range of ±15% except for one specimen whose notch root radius was as large as 0.25 mm. (4) The observed characteristics of fracture surface were essentially the same as those of the full size specimens. The measurement of lateral expansion, or ductility, was more useful in estimating the impact property of JFMS than that of fracture appearance (fibrous fracture). (author)

  19. Heat input effect on the microstructural transformation and mechanical properties in GTAW welds of a 409L ferritic stainless steel

    Directory of Open Access Journals (Sweden)

    Delgado, Jorge A.

    2016-06-01

    Full Text Available Welds without filler metal and welds using a conventional austenitic stainless steel filler metal (ER308L were performed to join a ferritic stainless steel with Gas Tungsten Arc Welding process (GTAW. Welding parameters were adjusted to obtain three different heat input values. Microstructure reveals the presence of coarse ferritic matrix and martensite laths in the Heat Affected Zone (HAZ. Dilution between filler and base metal was correlated with the presence of austenite, martensite and ferrite in the weld metal. Weld thermal cycles were measured to correlate the microstructural transformation in the HAZ. Microhardness measurements (maps and profiles allow to identify the different zones of the welded joints (weld metal, HAZ, and base metal. Comparing the base metal with the weld metal and the HAZ, a hardness increment (~172 HV0.5 to ~350 HV0.5 and ~310 HV0.5, respectively was observed, which has been attributed to the martensite formation. Tensile strength of the welded joints without filler metal increased moderately with respect to base metal. In contrast, ductility was approximately 25% higher than base metal, which provided a toughness improvement of the welded joints.Se llevaron a cabo soldaduras sin material de aporte y empleando un electrodo convencional (ER308L para unir un acero inoxidable ferrítico, empleando el proceso de soldadura de arco con electrodo de tungsteno (GTAW. Los parámetros de soldadura fueron ajustados para obtener tres valores diferentes de calor de aporte. La microestructura revela la presencia de una matriz ferrítica gruesa y placas de martensita en la Zona Afectada por el Calor (ZAC. La dilución entre el metal base y de aporte fue correlacionada con la presencia de austenita, martensita y ferrita en el metal de soldadura. Los ciclos térmicos de la soldadura fueron medidos para correlacionar la transformación microestrutural en la ZAC. Mediciones de microdureza (mapas y perfiles, permitieron identificar las

  20. Effect of Dissolved and Precipitated Niobium in Microalloyed Steel on Deformation Induced Ferrite Transformation (DIFT)

    Institute of Scientific and Technical Information of China (English)

    LIU Qing-you; DENG Su-huai; SUN Xin-jun; DONG Han; WENG Yu-qing

    2009-01-01

    Hot deformation processing was designed to study the effects of niobium (Nb) on DIFT. A prestrain of 0. 51 at 880 ℃ for different isothermal time was used for adjusting the deformed austenite constitution and Nb existing state, followed by a secondary heavy deformation at 780℃ for inducing the ferrite transformation. The volume fraction and grain size of deformation induced ferrite (DIF) obtained at different isothermal time between double hits were investigated. It was found that Nb dissolved in austenite is adverse to DIFT; however, the precipitation of Nb is beneficial to DIFT. As Nb plays the role in the conventional TMCP, Nb retards the recrystallization of deformed austenite and enhances the deformation stored energy in the multipass deformation, and in result, Nb promotes DIFT.

  1. Interaction of bending and axial load for ferritic stainless steel RHS columns

    OpenAIRE

    Arrayago Luquin, Itsaso; Picci, F; Mirambell Arrizabalaga, Enrique; Real Saladrigas, Esther

    2015-01-01

    Stainless steels are ideal for sustainable structural performances due to their excellent corrosion resistance, appropriate mechanical properties, aesthetic appearance and easy maintenance. However, the nonlinear behaviour and strain-hardening effects characterizing these materials make them different from carbon steel and some specific guidance is necessary. Although some investigations regarding the behaviour of stainless steel beam-columns subjected to combined compression and bending mome...

  2. Search for morphological parameters influential for prediction of the mechanical characteristics of an austeno-ferritic duplex stainless steel

    International Nuclear Information System (INIS)

    Duplex stainless steels are commonly used (among others in nuclear industry) for their good properties. However these steels may 'age' in service condition at high temperatures. As their mechanical properties (Charpy impact toughness, resistance to ductile tearing) are often very scattered and tend to decrease after ageing, it has become essential to predict them with high precision. For this, we propose to explain a part of the scattering of the mechanical properties with measurable parameters in relation with the particularly complicated two-phase morphology. The two-phase and bi-percolated morphology of the ferrite and austenite phases is first characterised from the observation of 2D images and from the reconstitution of a 3D image. At the same time we precise the genesis of the formation's mechanisms of the structure (germination and growth of the austenitic phase in the solidified ferri tic one) in relation with the literature. The morphological characteristics so observed corresponding with classical notions of mathematical morphology, - size, covariance, connexity -, we use morphological operators to measure morphological variables by image analysis. We establish then a link between toughness and a parameter measuring fineness of the morphology. The lack of data for very aged steels prevent us from proposing a model of toughness which could take this parameter into consideration at these ageing states, for which it is properly the more crucial to obtain specially precise predictions. A mathematical mo del of the 3D structure of the steel is finally proposed. We choose an homogeneous Markov chain of 3D spatial processes, whose evolution in time mimes the solidification. The morphology of the microstructure is so summarised with 8 parameters. This model is liable to be coupled with a model of toughness, for which it would so enlarge the possibilities of prediction. It could also be used to simulate subsequently the damage and the rupture of two

  3. Development of 15CrODS ferritic steels for over 1273 K service

    International Nuclear Information System (INIS)

    The 15 wt% CrODS steels (15CrODS steels) were manufactured as the high-temperature fusion reactor materials and their tensile properties at 1273 K were correlated with the oxide dispersion strengthening before and after aging. Fine dispersion of the oxide particles at initial condition in 15CrODS steels gives significantly higher strength compared with commercial MA956. The strength decrease in 15CrODS steels after aging at 1473 K for 100 h is attributed to coarsening of oxide particles, thus weakening of dispersion strength

  4. The influence of martensite, bainite and ferrite on the as-quenched constitutive response of simultaneously quenched and deformed boron steel – Experiments and model

    International Nuclear Information System (INIS)

    Highlights: • Gleeble tests were conducted to quench and simultaneously deform boron steel. • Different as-quenched vol. fractions of martensite, bainite and ferrite were observed. • Low to int. strain rate tensile tests were conducted on the as-quenched materials. • The presence of ferrite improved the uniform elongation, hardening rate and toughness. • A rate sensitive const. model was developed for varying vol fract. mart/bain/ferrite. - Abstract: This paper examines the relationship between as-formed microstructure and mechanical properties of a hot stamped boron steel used in automotive structural applications. Boron steel sheet metal blanks were austenized and quenched at cooling rates of 30 °C/s, 15 °C/s and 10 °C/s within a Gleeble thermal–mechanical simulator. For each cooling rate condition, the blanks were simultaneously deformed at temperatures of 600 °C and 800 °C. A strain of approximately 0.20 was imposed in the middle of the blanks, from which miniature tensile specimens were extracted. Depending on the cooling rate and deformation temperature imposed on the specimens, some of the as-quenched microstructures consisted of predominantly martensite and bainite, while others consisted of martensite, bainite and ferrite. Optical and SEM metallographraphic techniques were used to quantify the area fractions of the phases present and quasi-static (0.003 s−1) uniaxial tests were conducted on the miniature tensile specimens. The results revealed that an area fraction of ferrite greater than 6% led to an increased uniform elongation and an increase in n-value without affecting the strength of the material for equivalent hardness levels. This finding resulted in improved energy absorption due to the presence of ferrite and showed that a material with a predominantly bainitic microstructure containing 16% ferrite (with 257 HV) resulted in a 28% increase in energy absorption when compared to a material condition that was fully bainitic with a

  5. Elevated temperature tensile properties of P9 steel towards ferritic steel wrapper development for sodium cooled fast reactors

    Science.gov (United States)

    Choudhary, B. K.; Mathew, M. D.; Isaac Samuel, E.; Christopher, J.; Jayakumar, T.

    2013-11-01

    Tensile deformation and fracture behaviour of the three developmental heats of P9 steel for wrapper applications containing varying silicon in the range 0.24-0.60% have been examined in the temperature range 300-873 K. Yield and ultimate tensile strengths in all the three heats exhibited gradual decrease with increase in temperature from room to intermediate temperatures followed by rapid decrease at high temperatures. A gradual decrease in ductility to a minimum at intermediate temperatures followed by an increase at high temperatures has been observed. The fracture mode remained transgranular ductile. The steel displayed signatures of dynamic strain ageing at intermediate temperatures and dominance of recovery at high temperatures. No significant difference in the strength and ductility values was observed for varying silicon in the range 0.24-0.60% in P9 steel. P9 steel for wrapper application displayed strength and ductility values comparable to those reported in the literature.

  6. Precipitation and impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel during isothermal aging

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jian, E-mail: jh595@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Li, Huijun [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Barbaro, Frank [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); CBMM Technology Suisse, 14, Rue du Rhone, Geneve 1204 (Switzerland); Jiang, Laizhu [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China); Zhu, Zhixiong [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Xu, Haigang; Ma, Li [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China)

    2014-08-26

    The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe{sub 2}Nb (Laves phase) and Cr{sub 23}C{sub 6} formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe{sub 2}Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe{sub 2}Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe{sub 2}Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe{sub 2}Nb particles.

  7. Texture development study during the primary recrystallization of ferritic steels by using X ray and electron backscattering diffraction

    International Nuclear Information System (INIS)

    X ray and electron backscattering diffraction, in distinct levels, were applied to evaluate microstructural changes in two low carbon ferritic steels (2 per cent Si and ABNT 1006), observing the texture development in cold lamination step (skin-pass) and in the subsequent annealing at 760 deg C. In these two steels, results showed that after the skin-pass and annealing in the conditions of the present work, the observed phenomenon is the primary recrystallization. By applying skin-pass dislocations were introduced mostly in low Taylor factor grains as they are prone to be more deformed. Nucleation and grain growth were observed in high density dislocation cell regions. Silicon presence delayed the recovery favoring the sub-boundaries increase. It was not observed the abnormal grain growth, even in the presence of Gross grains. CSL boundaries did not guarantee the grains growth. Growing nuclei gave rise to grains with distinct orientations, showing that the grain growth was not dependent on the previous presence of grains with the developed orientation. This fact demonstrates that the abnormal grain growth is not necessarily related to the Gross grains. (author)

  8. Effect of thermo-mechanical treatments on the microstructure and mechanical properties of an ODS ferritic steel

    International Nuclear Information System (INIS)

    The Fe-14Cr-2W-0.3Ti-0.3Y2O3 oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel was fabricated by mechanical alloying of a pre-alloyed, gas atomised powder with yttria nano-particles, followed by hot isostatic pressing and thermo-mechanical treatments (TMTs). Two kinds of TMT were applied: (i) hot pressing, or (ii) hot rolling, both followed by annealing in vacuum at 850 deg. C. The use of a thermo-mechanical treatment was found to yield strong improvement in the microstructure and mechanical properties of the ODS RAF steel. In particular, hot pressing leads to microstructure refinement, equiaxed grains without texture, and an improvement in Charpy impact properties, especially in terms of the upper shelf energy (about 4.5 J). Hot rolling leads to elongated grains in the rolling direction, with a grain size ratio of 6:1, higher tensile strength and reasonable ductility up to 750 deg. C, and better Charpy impact properties, especially in terms of the ductile-to-brittle transition temperature (about 55 deg. C).

  9. Precipitation and impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel during isothermal aging

    International Nuclear Information System (INIS)

    The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe2Nb (Laves phase) and Cr23C6 formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe2Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe2Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe2Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe2Nb particles

  10. Mechanisms of inclusion evolution and intra-granular acicular ferrite formation in steels containing rare earth elements

    Institute of Scientific and Technical Information of China (English)

    Xiaoxuan DENG; Min JIANG; Xinhua WANG

    2012-01-01

    Inclusion characteristic and microstructure of rare earth (RE) elements containing steel were evaluated with scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS),element-mapping,optical microscopy (OM),and automated feature analysis (AFA) option equipped with ASPEX PSEM.Factsage was used tocalculate the equilibrium inclusion composition.Based on the calculation,an inclusion evolution mechanism was proposed.Furthermore,line scanning analysis was used to elucidate the intra-granular acicular ferrite (IAF) nucleation mechanism.The result showed that two different inclusions exist in sample steel:(Mn-Al-Si-Ti-La-Ce-O)+MnS complex inclusion and isolated MnS inclusion.Almost all nucleation sites for IAF are complex inclusions,while single MnS inclusion cannot induce IAF.A possible formation mechanism of complex inclusion is proposed based on calculated results using Factsage,which agrees well with experimental results.A Mn-depletion zone (MDZ) which exists adjacent to the (Mn-A1-Si-Ti-La-Ce-O) +-MnS complex inclusion can account for the IAF formation.However,the low volume fraction (1.49× 10-7)of effective inclusion may result in onlv 10% (volume fraction) IAF.

  11. The effect of Alloying elements on pitting resistance of ferritic and austenitic stainless steels in terms of pitting resistance equivalents (PRE)

    International Nuclear Information System (INIS)

    The alloying elements, such as Cr, Mo, and N of stainless steels play important roles in their resistances to pitting corrosion. The pitting resistances of stainless steels ha e long been characterized in terms of electrochemical parameters such as pitting potentials. however, in order to better understand the resistances to pitting of stainless steels, Pit Propagation Rate (PPR) and Critical Pitting Temperature (CPT) tests were carried out in deaerated 0.1N H2SO4 + 0.1N NaCl solution. The effect of Cr, Mo, and N alloying elements on the pitting corrosion resistances of both ferritic Fe-Cr, Fe-Cr-Mo stainless steels and austenitic stainless steels was examined by performing polarization, PPR, and CPT tests. The comparison between test results was made in terms of the Pitting Resistance Equivalent (PRE). Results showed that PRE values are the good parameters representing the extents of pitting corrosion resistance on a single scale regardless of both kinds of alloying elements and types of ferritic or austenitic stainless steels

  12. Microstructural Characteristics of Plasma Nitrided Layer on Hot-Rolled 304 Stainless Steel with a Small Amount of α-Ferrite

    Science.gov (United States)

    Xu, Xiaolei; Yu, Zhiwei; Cui, Liying; Niu, Xinjun; Cai, Tao

    2016-02-01

    The hot-rolled 304 stainless steel with γ-austenite and approximately 5 pct α-ferrite elongated along the rolling direction was plasma-nitrided at a low temperature of 693 K (420 °C). X-ray diffraction results revealed that the nitrided layer was mainly composed of the supersaturated solid solution of nitrogen in austenite ( γ N). Transmission electron microscopy (TEM) observations showed that the microstructure of the γ N phase exhibited "fracture factor contrast" reflective of the occurrence of fine pre-precipitations in γ N by the continuous precipitation. The occurrence of a diffuse scattering effect on the electron diffraction spots of γ N indicated that the pre-precipitation took place in γ N in the form of strongly bonded Cr-N clusters or pairs due to a strong attractive interaction of nitrogen with chromium. Scanning electron microscopy and TEM observations indicated that the discontinuous precipitation initiated from the γ/ α interfaces and grew from the austenite boundaries into austenite grains to form a lamellar structure consisting of CrN and ferrite. The orientation relationship between CrN and ferrite corresponded to a Baker-Nutting relationship: (100)CrN//(100) α ; [011]CrN//[001] α . A zigzag boundary line following the banded structure of alternating γ-austenite and elongated α-ferrite was presented between the nitrided layer and the substrate to form a continuous varying layer thickness, which resulted from the difference in diffusivities of nitrogen in α-ferrite and γ-austenite, along the γ/ α interfaces and through the lattice. Microstructural features similar to the γ N were also revealed in the ferrite of the nitrided layer by TEM. It was not excluded that a supersaturated solid solution of nitrogen in ferrite ( α N) formed in the nitrided layer.

  13. Experimental study on Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the ferrite region

    Institute of Scientific and Technical Information of China (English)

    Ji-ping Chen; Yong-lin Kang; Ying-min Hao; Guang-ming Liu; Ai-ming Xiong

    2009-01-01

    A Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the fer- rite region with lubrication was experimentally studied. Subsequent cold rolling and continuous annealing processes were also con-ducted. The results show that microstructures of ultra-low carbon bake hardening hot strips at room temperature are basically irregu-lar polygonal ferrites. The yield strength, ultimate tensile strength, n value, and r value of the No.2 specimen hot-rolled in the ferrite region with lubrication are 243 MPa, 364 MPa, 0.29, and 1.74, respectively, which are similar to those of the No.1 specimen hot-rolled in the conventional austenite region. The elongation rate and bake hardening value of No.2 specimen are 51% and 49.4 MPa, respectively, which are greater than those of No. 1 specimen. The No.2 specimen hot-rolled in the ferrite region with lubrication exhibits good mechanical properties and relatively excellent baking hardening performance. Therefore, the hot rolling experiment of Ti+Nb bearing ultra-low carbon bake hardening steel in the ferrite region with lubrication is feasible and can be considered in the fu-ture industrial trial production.

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

    International Nuclear Information System (INIS)

    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 500C 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 4000C, after which the shift drops rapidly to zero at about 4500C. The DBTT of the 12Cr-1MoVW steel shows a maximum increase at an irradiation temperature of about 4000C and less of an increase at either higher or lower irradiation temperatures

  15. Formation mechanism of {l_brace}111{r_brace} recrystallization texture in ferritic steels; Ferrite ko no {l_brace}111{r_brace} saikessho shugo shoshiki seisei kiko no ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Muraki, M.; Toge, T.; Sakata, K.; Obara, T. [Kawasaki Steel Corp., Tokyo (Japan); Furubayashi, E. [Waseda University, Tokyo (Japan). School of Science and Engineering

    1999-10-01

    Recrystallized ND//<111> texture is obtained from cold rolled ND//<111> matrix even in single crystals where no grain boundary exists. These ND//<111> recrystallized grains are analyzed to emerge by <112> rotation from cold rolled ND//<111> matrix. This rotation is related to (110)<111> slip systems operated during cold rolling. Recrystallized orientations from cold rolled (111)<110> single crystal are 18 degrees rotated around these <112> axes and deviate from ND//<111> by 6 degrees. Since this deviation is not recognizable in polycrystalline material owing to its symmetry, ND//<111> recrystallized texture in cold rolled commercial ferritic steels such as IF steels or electrical steels, may also be explained by the same <112> rotation, not by conventional ND//<111> rotation. (author)

  16. Effect of Welding Processes on Tensile and Impact Properties, Hardness and Microstructure of AISI 409M Ferritic Stainless Joints Fabricated by Duplex Stainless Steel Filler Metal

    Institute of Scientific and Technical Information of China (English)

    A K Lakshminarayanan; K Shanmugam; V Balasubramanian

    2009-01-01

    The effect of welding processes such as shielded metal arc welding, gas metal arc welding and gas tungsten arc welding on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade is studied. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure and fracture surface morphology of the welded joints have been evaluated and the results are compared. From this investigatio.n, it is found that gas tungsten arc welded joints of ferritic stainless steel have superior tensile and impact properties compared with shielded metal are and gas metal arc welded joints and this is mainly due to the presence of finer grains in fusion zone and heat affected zone.

  17. Combination of helical ferritic-steel inserts and flux-tube-expansion divertor for the heat control in tokamak DEMO reactor

    Energy Technology Data Exchange (ETDEWEB)

    Takizuka, T., E-mail: takizuka.tomonori@gmail.com [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Tokunaga, S.; Hoshino, K. [Japan Atomic Energy Agency, 2-166, Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan); Shimizu, K. [Japan Atomic Energy Agency, 801-1, Mukoyama, Naka 311-0193 (Japan); Asakura, N. [Japan Atomic Energy Agency, 2-166, Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan)

    2015-08-15

    Edge localized modes (ELMs) in the H-mode operation of tokamak reactors may be suppressed/mitigated by the resonant magnetic perturbation (RMP), but RMP coils are considered incompatible with DEMO reactors under the strong neutron flux. We propose an innovative concept of the RMP without installing coils but inserting ferritic steels of the helical configuration. Helically perturbed field is naturally formed in the axisymmetric toroidal field through the helical ferritic steel inserts (FSIs). When ELMs are avoided, large stationary heat load on divertor plates can be reduced by adopting a flux-tube-expansion (FTE) divertor like an X divertor. Separatrix shape and divertor-plate inclination are similar to those of a simple long-leg divertor configuration. Combination of the helical FSIs and the FTE divertor is a suitable method for the heat control to avoid transient ELM heat pulse and to reduce stationary divertor heat load in a tokamak DEMO reactor.

  18. Microstructure and mechanical behavior of neutron irradiated ultrafine grained ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad Alsabbagh; Apu Sarkar; Brandon Miller; Jatuporn Burns; Leah Squires; Douglas Porter; James I. Cole; K. L. Murty

    2014-10-01

    Neutron irradiation effects on ultra-fine grain (UFG) low carbon steel prepared by equal channel angular pressing (ECAP) has been examined. Counterpart samples with conventional grain (CG) sizes have been irradiated alongside with the UFG ones for comparison. Samples were irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) to 1.24 dpa. Atom probe tomography revealed manganese, silicon-enriched clusters in both ECAP and CG steel after neutron irradiation. X-ray quantitative analysis showed that dislocation density in CG increased after irradiation. However, no significant change was observed in UFG steel revealing better radiation tolerance.

  19. Numerical simulation of hydrogen-assisted crack initiation in austenitic-ferritic duplex steels; Numerische Simulation der wasserstoffunterstuetzten Rissbildung in austentisch-ferritischen Duplexstaehlen

    Energy Technology Data Exchange (ETDEWEB)

    Mente, Tobias

    2015-07-01

    Duplex stainless steels have been used for a long time in the offshore industry, since they have higher strength than conventional austenitic stainless steels and they exhibit a better ductility as well as an improved corrosion resistance in harsh environments compared to ferritic stainless steels. However, despite these good properties the literature shows some failure cases of duplex stainless steels in which hydrogen plays a crucial role for the cause of the damage. Numerical simulations can give a significant contribution in clarifying the damage mechanisms. Because they help to interpret experimental results as well as help to transfer results from laboratory tests to component tests and vice versa. So far, most numerical simulations of hydrogen-assisted material damage in duplex stainless steels were performed at the macroscopic scale. However, duplex stainless steels consist of approximately equal portions of austenite and δ-ferrite. Both phases have different mechanical properties as well as hydrogen transport properties. Thus, the sensitivity for hydrogen-assisted damage is different in both phases, too. Therefore, the objective of this research was to develop a numerical model of a duplex stainless steel microstructure enabling simulation of hydrogen transport, mechanical stresses and strains as well as crack initiation and propagation in both phases. Additionally, modern X-ray diffraction experiments were used in order to evaluate the influence of hydrogen on the phase specific mechanical properties. For the numerical simulation of the hydrogen transport it was shown, that hydrogen diffusion strongly depends on the alignment of austenite and δ-ferrite in the duplex stainless steel microstructure. Also, it was proven that the hydrogen transport is mainly realized by the ferritic phase and hydrogen is trapped in the austenitic phase. The numerical analysis of phase specific mechanical stresses and strains revealed that if the duplex stainless steel is

  20. Microstructural Characteristic of Dissimilar Welded Components (AISI 430 Ferritic-AISI 304 Austenitic Stainless Steels) by CO2 Laser Beam Welding (LBW)

    OpenAIRE

    CALIGULU, Ugur; Dikbas, Halil; Taskin, Mustafa

    2012-01-01

    In this study, microstructural characteristic of dissimilar welded components (AISI 430 ferritic-AISI 304 austenitic stainless steels) by CO2 laser beam welding (LBW) was investigated. Laser beam welding experiments were carried out under argon and helium atmospheres at 2000 and 2500 W heat inputs and 100-200-300 cm/min. welding speeds. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy, SEM, EDS and XRD analysis. The tensile strengt...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

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

  2. Experimental study on ferritic stainless steel RHS and SHS cross-sectional resistance under combined loading

    OpenAIRE

    Arrayago Luquin, Itsaso; Real Saladrigas, Esther

    2015-01-01

    The excellent corrosion resistance presented by all stainless steel grades, together with their appropriate mechanical properties, aesthetic appearance and easy maintenance , make s these metallic alloys perfect for sustainable structural performances. However, their nonlinear stress - strain behaviour together with the ir strong strain hardening features, make s them different from carbon steel and makes the development of some specific guidance necessary . Although the compressive and flexu...

  3. Tensile and charpy impact properties of irradiated reduced-activation ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-10-01

    Tensile tests were conducted on eight reduced-activation Cr-W steels after irradiation to 15-17 and 26-29 dpa, and Charpy impact tests were conducted on the steels irradiated to 26-29 dpa. Irradiation was in the Fast Flux Test Facility at 365{degrees}C on steels containing 2.25-12% Cr, varying amounts of W, V, and Ta, and 0.1%C. Previously, tensile specimens were irradiated to 6-8 dpa and Charpy specimens to 6-8, 15-17, and 20-24 dpa. Tensile and Charpy specimens were also thermally aged to 20000 h at 365{degrees}C. Thermal aging had little effect on the tensile behavior or the ductile-brittle transition temperature (DBTT), but several steels showed a slight increase in the upper-shelf energy (USE). After {approx}7 dpa, the strength of the steels increased and then remained relatively unchanged through 26-29 dpa (i.e., the strength saturated with fluence). Post-irradiation Charpy impact tests after 26-29 dpa showed that the loss of impact toughness, as measured by an increase in DBTT and a decrease in the USE, remained relatively unchanged from the values after 20-24 dpa, which had been relatively unchanged from the earlier irradiations. As before, the two 9Cr steels were the most irradiation resistant.

  4. Microstructure and mechanical behavior of neutron irradiated ultrafine grained ferritic steel

    International Nuclear Information System (INIS)

    Neutron irradiation effects on ultra-fine grain (UFG) low carbon steel prepared by equal channel angular pressing (ECAP) have been examined. Counterpart samples with conventional grain (CG) sizes have been irradiated alongside with the UFG ones for comparison. Samples were irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) to 1.37 dpa. Atom probe tomography revealed manganese and silicon-enriched clusters in both UFG and CG steel after neutron irradiation. Mechanical properties were characterized using microhardness and tensile tests, and irradiation of UFG carbon steel revealed minute radiation effects in contrast to the distinct radiation hardening and reduction of ductility in its CG counterpart. After irradiation, micro hardness indicated increases of around 9% for UFG versus 62% for CG steel. Similarly, tensile strength revealed increases of 8% and 94% respectively for UFG and CG steels while corresponding decreases in ductility were 56% versus 82%. X-ray quantitative analysis showed that dislocation density in CG increased after irradiation while no significant change was observed in UFG steel, revealing better radiation tolerance. Quantitative correlations between experimental results and modeling were demonstrated based on irradiation induced precipitate strengthening and dislocation forest hardening mechanisms

  5. Microstructure and mechanical behavior of neutron irradiated ultrafine grained ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Alsabbagh, Ahmad, E-mail: ahalsabb@ncsu.edu [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Sarkar, Apu [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Miller, Brandon [ATR National Scientific User Facility, Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Burns, Jatuporn [Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Squires, Leah; Porter, Douglas; Cole, James I. [ATR National Scientific User Facility, Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Murty, K.L. [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States)

    2014-10-06

    Neutron irradiation effects on ultra-fine grain (UFG) low carbon steel prepared by equal channel angular pressing (ECAP) have been examined. Counterpart samples with conventional grain (CG) sizes have been irradiated alongside with the UFG ones for comparison. Samples were irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) to 1.37 dpa. Atom probe tomography revealed manganese and silicon-enriched clusters in both UFG and CG steel after neutron irradiation. Mechanical properties were characterized using microhardness and tensile tests, and irradiation of UFG carbon steel revealed minute radiation effects in contrast to the distinct radiation hardening and reduction of ductility in its CG counterpart. After irradiation, micro hardness indicated increases of around 9% for UFG versus 62% for CG steel. Similarly, tensile strength revealed increases of 8% and 94% respectively for UFG and CG steels while corresponding decreases in ductility were 56% versus 82%. X-ray quantitative analysis showed that dislocation density in CG increased after irradiation while no significant change was observed in UFG steel, revealing better radiation tolerance. Quantitative correlations between experimental results and modeling were demonstrated based on irradiation induced precipitate strengthening and dislocation forest hardening mechanisms.

  6. Development of A New Class of Fe-3Cr-W(V)Ferritic Steels for Industrial Process Applications

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.J.; Jawad, M.H. (Nooter Corp.)

    2005-06-15

    The project, 'Development of a New Class of Fe-Cr-W(V) Ferritic Steels for Industrial Process Applications', was a Cooperative Research and Development Agreement (CRADA) between Oak Ridge National Laboratory (ORNL) and Nooter Corporation. This project dealt with improving the materials performance and fabrication for the hydrotreating reactor vessels, heat recovery systems, and other components for the petroleum and chemical industries. The petroleum and chemical industries use reactor vessels that can approach the ship weights of approximately 300 tons with vessel wall thicknesses of 3 to 8 in. These vessels are typically fabricated from Fe-Cr-Mo steels with chromium ranging from 1.25 to 12% and molybdenum from 1 to 2%. Steels in this composition have great advantages of high thermal conductivity, low thermal expansion, low cost, and properties obtainable by heat treatment. With all of the advantages of Fe-Cr-Mo steels, several issues are faced in design and fabrication of vessels and related components. These issues include the following: (1) low strength properties of current alloys require thicker sections; (2) increased thickness causes heat-treatment issues related to nonuniformity across the thickness and thus not achieving the optimum properties; (3) fracture toughness (ductile-to-brittle transition ) is a critical safety issue for these vessels, and it is affected in thick sections due to nonuniformity of microstructure; (4) PWHT needed after welding and makes fabrication more time-consuming with increased cost; and (5) PWHT needed after welding also limits any modifications of the large vessels in service. The goal of this project was to reduce the weight of large-pressure vessel components (ranging from 100 to 300 tons) by approximately 25% and reduce fabrication cost and improve in-service modification feasibility through development of Fe-3Cr-W(V) steels with combination of nearly a 50% higher strength, a lower DBTT and a higher upper

  7. Analysis of Brittleness for Ferritic Stainless Steel 430 As-cast%430铁素体不锈钢铸件脆性分析

    Institute of Scientific and Technical Information of China (English)

    周灿旭; 师红旗; 陈育贵; 丁毅

    2009-01-01

    对430铸造铁素体不锈钢的脆性进行了分析,采用金相显微组织分析、力学性能测试、冲击断口宏观和SEM等技术手段探讨了430不锈钢发生脆化的原因.结果表明:430铸造铁素体不锈钢的脆性主要是由铸造过程中马氏体的生成引起的,通过700℃热处理水冷可以显著提高430铸造铁索体不锈钢的韧性,并同时改善其抗拉强度和塑性.%The brittleness of ferritic stainless steel 430 as-east was analyzed by metaUographic microscope, mechanical properties test, macroscope ffactography and SEM. The results show that the brittleness of ferritic stainless steel 430 as-cast is caused by martensite. The toughness of 430 ferritic stainless steel increases obviously through 700 ℃ heat treatment, while the tensile strength and ductility properties also improves.

  8. Influence of cubic texture intensity of hot rolled ferritic non-oriented electrical steels on the microstructure and texture in the final processed material

    Science.gov (United States)

    Stöcker, A.; Schneider, J.; Scholze, T.; Franke, A.; Hermann, H.; Kawalla, R.

    2015-04-01

    The magnetic properties of non-oriented electrical steels are determined by the microstructure and texture of the material. Besides optimum grain size (microstructure) for low values of specific magnetic losses, a high intensity of θ-fibre texture and low intensity of γ-fibre and α-fibre texture is desirable. Each of the processing steps influences the intensity of the θ-fibre in the final processed material. In this paper the interplay of the various processing steps on the intensity of the θ-fibre is regarded for ferritic Iron-Silicon steels with 2.4 wt.% Si and 3.0 wt.% Si.

  9. Mechanical properties and microstructure of three Russian ferritic/martensitic steels irradiated in BN-350 reactor to 50 dpa at 490 oC

    International Nuclear Information System (INIS)

    Ferritic/martensitic (F/M) steels are being considered for application in fusion reactors, intense neutron sources, and accelerator-driven systems. While EP-450 is traditionally used with sodium coolants in Russia, EP-823 and EI-852 steels with higher silicon levels have been developed for reactor facilities using lead-bismuth coolant. To determine the influence of silicon additions on short-term mechanical properties and microstructure, ring specimens cut from cladding tubes of these three steels were irradiated in sodium at 490 oC in the BN-350 reactor to 50 dpa. Post-irradiation tensile testing and microstructural examination show that EI-852 steel (1.9 wt% Si) undergoes severe irradiation embrittlement. Microstructural investigation showed that the formation of near-continuous χ-phase precipitates on grain boundaries is the main cause of the embrittlement

  10. Control of substrate oxidation in MOD ceramic coating on low-activation ferritic steel with reduced-pressure atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Teruya, E-mail: teru@nifs.ac.jp; Muroga, Takeo

    2014-12-15

    Highlights: • A Cr{sub 2}O{sub 3} layer was produced on a ferritic steel substrate with a reduced-pressure. • The Cr{sub 2}O{sub 3} layer prevents further substrate oxidation in following coating process. • The Cr{sub 2}O{sub 3} layer has a function as a hydrogen permeation barrier. • A smooth MOD Er{sub 2}O{sub 3} coating was successfully made on the Cr{sub 2}O{sub 3} layer by dip coating. • The Cr{sub 2}O{sub 3} layer would enhance flexibility in MOD coating process and performances. - Abstract: An Er{sub 2}O{sub 3} ceramic coating fabricated using the metal–organic decomposition (MOD) method on a Cr{sub 2}O{sub 3}-covered low-activation ferritic steel JLF-1 substrate was examined to improve hydrogen permeation barrier performance of the coating. The Cr{sub 2}O{sub 3} layer was obtained before coating by heat treating the substrate at 700 °C under reduced pressures of <5 × 10{sup −3} Pa and 5 Pa. The Cr{sub 2}O{sub 3} layer was significantly stable even with heat treatment at 700 °C in air. This layer prevented further production of Fe{sub 2}O{sub 3}, which has been considered to degrade coating performance. An MOD Er{sub 2}O{sub 3} coating with a smooth surface was successfully obtained on a Cr{sub 2}O{sub 3}-covered JLF-1 substrate by dip coating followed by drying and baking. Preprocessing to obtain a Cr{sub 2}O{sub 3} layer would provide flexibility in the coating process for blanket components and ducts. Moreover, the Cr{sub 2}O{sub 3} layer suppressed hydrogen permeation through the JLF-1 substrate. While further optimization of the coating fabrication process is required, it would be possible to suppress hydrogen permeation significantly by multilayers of Cr{sub 2}O{sub 3} and MOD oxide ceramic.

  11. Influence of heat treatment conditions on microstructures and mechanical properties of ferritic-martensitic ODS steel

    International Nuclear Information System (INIS)

    To develop an advanced ODS steel for core structural materials for next generation nuclear reactor system applications, it is important to optimize its heat treatment conditions to improve the high temperature strength and radiation resistance. This study investigates effects of heat treatment conditions on microstructures and mechanical properties of FM ODS steel. For this, 10Cr -1Mo FM ODS steel was prepared by mechanical alloying (MA), hot isostatic pressing (HIP), and hot extrusion process. Hardness measurements were carried out after heat treatments to evaluate the influences of heat treatments on the mechanical properties. The microstructures were observed using SEM, electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). This study investigated the effects of heat treatment conditions on microstructures and mechanical properties of FM ODS steel. The FM ODS steels were fabricated by the MA, HIP and hot-extrusion processes. The optimized heat treatment condition for 10Cr-1Mo FM ODS was determined to enhance the mechanical property

  12. Conversion of MX Nitrides to Modified Z-Phase in 9-12%Cr Ferritic Steels

    DEFF Research Database (Denmark)

    Cipolla, Leonardo

    for Z-phase formation, this explains why 12%Cr steels (i.e. P122, VM12, NF12) suffer from fast and abundant Z-phase precipitation, while 9%Cr steels (i.e. Grades 91, 92, 911) do not. In this thesis the role of vanadium and niobium nitrides in the formation of Z-phase in 9-12%Cr steels is investigated......-phase. The second model alloy, 12CrVN, was selected to investigate the transformation of pure V-nitride into V-based Z-phase, CrVN, and through comparison to understand the effect of Nb. Thus, without the disturbing interferences of carbides and intermetallic phases (i.e. M23C6, NbC, Fe2(Mo,W)) it was possible...

  13. Summary Report of Summer Work: High Purity Single Crystal Growth & Microstructure of Ferritic-Martensitic Steels

    Energy Technology Data Exchange (ETDEWEB)

    Pestovich, Kimberly Shay [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-18

    Harnessing the power of the nuclear sciences for national security and to benefit others is one of Los Alamos National Laboratory’s missions. MST-8 focuses on manipulating and studying how the structure, processing, properties, and performance of materials interact at the atomic level under nuclear conditions. Within this group, single crystal scintillators contribute to the safety and reliability of weapons, provide global security safeguards, and build on scientific principles that carry over to medical fields for cancer detection. Improved cladding materials made of ferritic-martensitic alloys support the mission of DOE-NE’s Fuel Cycle Research and Development program to close the nuclear fuel cycle, aiming to solve nuclear waste management challenges and thereby increase the performance and safety of current and future reactors.

  14. Grain boundary sliding at high temperature deformation in cold-rolled ODS ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sugino, Yoshito, E-mail: y-sugino@eng.hokudai.ac.jp [Materials Science and Engineering, Graduate School of Engineering, Hokkaido University, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Ukai, Shigeharu [Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Leng, Bin [Materials Science and Engineering, Graduate School of Engineering, Hokkaido University, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Oono, Naoko; Hayashi, Shigenari [Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13, W-8, Kita-ku, Sapporo 060-8628 (Japan); Kaito, Takeji; Ohtsuka, Satoshi [Advanced Nuclear System R and D Directorate, Japan Atomic Energy Agency (JAEA), 4002, Narita, Oarai, Ibaraki 311-1393 (Japan)

    2014-09-15

    A tensile test was performed at a loading direction perpendicular to elongated cold-rolled grains, and it confirmed the step of the scratched lines across the grain boundaries on the specimen surface, providing evidence for grain boundary sliding in oxide dispersion strengthened (ODS) steels. Dynamic recovery within the grains was also observed, and a simple model was constructed that consisted of grain boundary sliding and mismatch accommodation induced by vacancy flow. It was confirmed that such grain boundary sliding was suppressed in ODS steel relative to iron as a result of the pinning of the dislocation movement by the dispersed oxide particles.

  15. Dynamic tensile tests on ferritic and austenitic steels with improved testing and measuring technique

    OpenAIRE

    Kussmaul, K.; Schuele, M.

    1994-01-01

    For analysing dynamically loaded structures by means of the finite element method a dynamic constitutive material model is necessary to obtain reliable results. For this purpose dynamic tensile tests were performed with the fine grained steel 20 MnMoNi 5 5 (A 508 Cl. 3) and the austenitic steel X 6 CrNi 18 11 at different velocities. Smooth round bar specimens of different geometries were used. Displacement at the lower end of the specimen as well as force and strain were measured. The whole ...

  16. Incubation time of isothermally transformed allotriomorphic ferrite in medium carbon steels

    OpenAIRE

    Capdevila, Carlos; García de Andrés, Carlos; García Caballero, Francisca

    2001-01-01

    The authors acknowledge financial support from the Spanish Comisio´n Interministerial de Ciencia y Tecnologı´a (CICYT) (project-PETRI 95-0089-OP). GSB Acero S.A. and CEIT are thanked for providing the steel and their collaboration in this project

  17. Isothermal allotriomorphic ferrite formation kinetics in a medium carbon vanadium-titanium microalloyed steel

    OpenAIRE

    Capdevila, Carlos; García Caballero, Francisca; García de Andrés, Carlos

    2001-01-01

    The authors acknowledge financial support from the Spanish Comisio´n Interministerial de Ciencia y Tecnologı´a (CICYT) (project-PETRI 95-0089-OP). GSB Acero S.A and CEIT are thanked for providing the steel and their collaboration in this project

  18. Low cycle fatigue behavior of a ferritic reactor pressure vessel steel

    International Nuclear Information System (INIS)

    The cyclic stress–strain response and the low cycle fatigue (LCF) behavior of 20MnMoNi55 pressure vessel steel were studied. Tensile strength and LCF properties were examined at room temperature (RT) using specimens cut from rolling direction of a rolled block. The fully reversed strain-controlled LCF tests were conducted at a constant total strain rate with different axial strain amplitude levels. The cyclic strain–stress relationships and the strain–life relationships were obtained through the test results, and related LCF parameters of the steel were calculated. The studied steel exhibits cyclic softening behavior. Furthermore, analysis of stabilized hysteresis loops showed that the steel exhibits non-Masing behavior. Complementary scanning electron microscopy examinations were also carried out on fracture surfaces to reveal dominant damage mechanisms during crack initiation, propagation and fracture. Multiple crack initiation sites were observed on the fracture surface. The investigated LCF behavior can provide reference for pressure vessel life assessment and fracture mechanisms analysis

  19. Evaluation of microstructure and creep damage in high-Cr ferritic steel welds

    Institute of Scientific and Technical Information of China (English)

    Masaaki TABUCHI; Hiromichi HONGO

    2011-01-01

    11Cr-0.4Mo-2W-CuVNb steel (ASME Gr.122) is used for boiler components in ultrasupercritical (USC) thermal power plants. The creep strength of high-Cr steel welds decreases due to the formation of Type Ⅳ creep damage in the heat-affected zone (HAZ) during long-term use at high temperatures. In the present study, the processes and mechanisms of Type Ⅳ creep damage were elucidated by investigating the long-term creep strength, microstructure and damage behavior of Gr.122 steel welds.Creep tests using thick welded joints were interrupted at several time steps, and the initiation, evolution and distribution of creep damage were measured. It was found that the formation and growth of creep damage was suppressed during the steadystate stage; creep voids formed at 0.5 of life, and coalesced to form a crack after 0.9of life. Type Ⅳ creep damage was mostly observed in the area about 30% below the surface of the plate. Differences in creep damage behavior between Gr.122 and Gr.91 steel welds were examined. Experimental creep damage distribution was compared with computed versions using the finite element method and damage mechanics.

  20. Low cycle fatigue behavior of a ferritic reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Apu, E-mail: asarkar@barc.gov.in; Kumawat, Bhupendra K.; Chakravartty, J.K.

    2015-07-15

    The cyclic stress–strain response and the low cycle fatigue (LCF) behavior of 20MnMoNi55 pressure vessel steel were studied. Tensile strength and LCF properties were examined at room temperature (RT) using specimens cut from rolling direction of a rolled block. The fully reversed strain-controlled LCF tests were conducted at a constant total strain rate with different axial strain amplitude levels. The cyclic strain–stress relationships and the strain–life relationships were obtained through the test results, and related LCF parameters of the steel were calculated. The studied steel exhibits cyclic softening behavior. Furthermore, analysis of stabilized hysteresis loops showed that the steel exhibits non-Masing behavior. Complementary scanning electron microscopy examinations were also carried out on fracture surfaces to reveal dominant damage mechanisms during crack initiation, propagation and fracture. Multiple crack initiation sites were observed on the fracture surface. The investigated LCF behavior can provide reference for pressure vessel life assessment and fracture mechanisms analysis.