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Sample records for aged duplex stainless

  1. Thermal ageing of duplex stainless steels

    International Nuclear Information System (INIS)

    The evolution of the mechanical properties of Mobearing anf Mo-free cast duplex stainless steels, induced by long term ageing in the range 300-400 deg C, has been studied in relation with the evolution of their microstructure. The unmixing of the ferritic Fe-Cr-Ni, solid solution by three-dimensional (sponge-like) spinodal decomposition and the precipitation of intermetallic G-phase particles are the main characteristics of this microstructural evolution

  2. Thermal aging of cast duplex stainless steels

    International Nuclear Information System (INIS)

    Cast duplex stainless steels of CR8M and CF8 are used in major components because of their superior characteristics, such as corrosion resistance, weldability and so on. But, these stainless steels are known to have tendency of thermal aging embrittlement after long term service. Therefore, mechanical properties have been investigated using Charpy impact specimens and fracture toughness specimens aged at 300∼400 C up to 40,000 hours. As the results, effects of thermal aging on mechanical properties of these stainless steels were identified and a good relationship between Charpy impact energy and fracture toughness was obtained. In addition, prediction method for Charpy absorbed energy and fracture toughness was established

  3. Characterization of thermal aging of duplex stainless steel by SQUID

    International Nuclear Information System (INIS)

    Thermal aging is a growing concern for long-term-aged duplex stainless steel piping in nuclear power plants. Superconducting QUantum Interference Device (SQUID) was used for the detection of thermal aging of SUS329 rolled duplex stainless steel and SCS16 cast duplex stainless steel. It was found that the SQUID output signal pattern in the presence of AC magnetic field applied to the specimen was sensitive to the changes in electromagnetic properties due to thermal aging

  4. Evaluation of the thermal ageing of duplex stainless steels

    International Nuclear Information System (INIS)

    Three methods have been investigated to follow up the thermal ageing of duplex stainless steels: microhardness tests, instrumented ultramicrohardness tests and Small Angle Neutron Scattering (SANS) techniques. The values measured with these methods have been correlated with pertinent parameters of the metallurgical ageing phenomenon determined by Atom-Probe. These methods seem to be sensitive and reproducible enough to detect and follow up the ageing of duplex stainless steels. They can be applied on small samples (chips) drawn from in-service components. (authors). 10 refs., 9 figs., 3 tabs

  5. Long term thermal aging of cast duplex stainless steels

    International Nuclear Information System (INIS)

    Cast duplex stainless steels of CF8M and CF8 are used in major components because of their superior characteristics, such as corrosion resistance, weldability and so on. But, these stainless steels are known to have tendency of thermal aging embrittlement after long term service. Therefore, mechanical properties and metallurgical structure were investigated using materials aged at 290--400 C up to 30,000 hours. As the results show, effects of thermal aging on mechanical properties and metallurgical behavior were identified. In addition, prediction method for Charpy absorbed energy and fracture toughness was established. The following results have been obtained: (1) it was recognized that Charpy absorbed energy and fracture toughness tend to decrease and the tensile strength tend to increase with the increasing aging time; (2) it was confirmed that thermal aging embrittlement was caused by the phase separation in ferrite from the test results of APFIM; (3) in the degradation prediction model development the prediction model was applied to the material test data, including materials aged for 30,000 hours. As the results, the degradation prediction formulas for CVRT, CVHT, JIC and J6 were obtained. The toughness of cast duplex stainless steels during service could be estimated from chemical composition using this method

  6. Long term thermal aging of cast duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Isao; Koyama, Masakuni [Japan Power Engineering and Inspection Corp., Tokyo (Japan); Kawaguchi, Seiichi [Mitsubishi Heavy Industries, Ltd., Takasago (Japan); Mimaki, Hidehito [Mitsubishi Heavy Industries, Ltd., Kobe (Japan); Akiyama, Mamoru; Mishima, Yoshitsugu [Univ. of Tokyo (Japan); Okubo, Tadatsune [Sophia Univ., Tokyo (Japan); Mager, T.R.

    1996-09-01

    Cast duplex stainless steels of CF8M and CF8 are used in major components because of their superior characteristics, such as corrosion resistance, weldability and so on. But, these stainless steels are known to have tendency of thermal aging embrittlement after long term service. Therefore, mechanical properties and metallurgical structure were investigated using materials aged at 290--400 C up to 30,000 hours. As the results show, effects of thermal aging on mechanical properties and metallurgical behavior were identified. In addition, prediction method for Charpy absorbed energy and fracture toughness was established. The following results have been obtained: (1) it was recognized that Charpy absorbed energy and fracture toughness tend to decrease and the tensile strength tend to increase with the increasing aging time; (2) it was confirmed that thermal aging embrittlement was caused by the phase separation in ferrite from the test results of APFIM; (3) in the degradation prediction model development the prediction model was applied to the material test data, including materials aged for 30,000 hours. As the results, the degradation prediction formulas for CVRT, CVHT, J{sub IC} and J{sub 6} were obtained. The toughness of cast duplex stainless steels during service could be estimated from chemical composition using this method.

  7. Thermal Aging Phenomena in Cast Duplex Stainless Steels

    Science.gov (United States)

    Byun, T. S.; Yang, Y.; Overman, N. R.; Busby, J. T.

    2016-02-01

    Cast stainless steels (CASSs) have been extensively used for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. The thermal embrittlement of CASS components is one of the most serious concerns related to the extended-term operation of nuclear power plants. Many past researches have concluded that the formation of Cr-rich α'-phase by Spinodal decomposition of δ-ferrite phase is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of the formation of cleavage at ferrite and its propagation via separation of ferrite-austenite interphase. This article intends to provide an introductory overview on the thermal aging phenomena in LWR-relevant conditions. Firstly, the thermal aging effect on toughness is discussed in terms of the cause of embrittlement and influential parameters. An approximate analysis of thermal reaction using Arrhenius equation was carried out to scope the aging temperatures for the accelerated aging experiments to simulate the 60 and 80 years of services. Further, an equilibrium precipitation calculation was performed for model CASS alloys using the CALPHAD program, and the results are used to describe the precipitation behaviors in duplex stainless steels. These results are also to be used to guide an on-going research aiming to provide knowledge-based conclusive prediction for the integrity of the CASS components of LWR power plants during the service life extended up to and beyond 60 years.

  8. Thermal Aging Phenomena in Cast Duplex Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang; Yang, Ying; Overman, Nicole R.; Busby, Jeremy T.

    2016-02-28

    Cast stainless steels (CASSs) have been extensively used for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. The thermal embrittlement of CASS components is one of the most serious concerns related to the extended-term operation of nuclear power plants. Many past researches have concluded that the formation of Cr–rich α'-phase by Spinodal decomposition of δ-ferrite phase is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of the formation of cleavage at ferrite and its propagation via separation of ferrite-austenite interphase. This article intends to provide an introductory overview on the thermal aging phenomena in LWR relevant conditions. Firstly, the thermal aging effect on toughness is discussed in terms of the cause of embrittlement and influential parameters. An approximate analysis of thermal reaction using Arrhenius equation was carried out to scope the aging temperatures for the accelerated aging experiments to simulate the 60 and 80 years of services. Further, equilibrium precipitation calculation was performed for model CASS alloys using the CALPHAD program and the results are used to describe the precipitation behaviors in duplex stainless steels. These results are also to be used to guide an on-going research aiming to provide knowledge-based conclusive prediction for the integrity of the CASS components of LWR power plants during the service life extended up to and beyond 60 years.

  9. Aging of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. The existing data are evaluated to determine the expected embrittlement of cast components during the operating lifetime of reactors and to define the objectives and scope of the investigation. This presentation describes the status of the program. Data for the metallurgical characterization of the various cast stainless steels used in the investigation are presented. Charpy impact tests on short-term aged material indicate that CF-3 stainless steels are less susceptible to embrittlement than CF-8 or CF-8M stainless steels. Microstructural characterization of cast stainless steels that were obtained from Georg Fischer Co. and aged for up to 70,000 h at 300, 350, and 4000C reveals the formation of four different types of precipitates that are not α'. Embrittlement of the ferrite phase is primarily due to pinning of the dislocations by two of these precipitates, designated as Type M and Type X. The ferrite phase is embrittled after approx. 8 y at 3000C and shows cleavage fracture. Examination of the fracture surfaces of the impact-test specimens indicates that the toughness of the long-term aged material is determined by the austenite phase. 8 figures, 3 tables

  10. Aging of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels operating conditions. The existing data are evaluated to determine the expected embrittlement of cast components during the operating lifetime of reactors and to define the objectives and scope of the investigation. This presentation describes the status of the program. Data for the metallurgical characterization of the various cast stainless steels used in the investigation are presented. Charpy impact tests on short-term aged material indicate that CF-3 stainless steels are less susceptible to embrittlement than CF-8 or CF-8M stainless steels. Microstructural characterization of cast stainless steels that were obtained from Georg Fischer Co. and aged for up to 70 000 h at 300, 350 and 4000C reveals the formation of four different types of precipitates that are not α'. Embrittlement of the ferrite phase is primarily due to pinning of the dislocations by two of these precipitates, designated as Type M and Type X. The ferrite phase is embrittled after proportional 8 y at 3000C and shows cleavage fracture. Examination of the fracture surfaces of the impact test specimens indicates that the toughness of the long-term aged material is determined by the austenitic phase. (orig./HP)

  11. Investigation on thermally aged cast duplex stainless steel piping

    International Nuclear Information System (INIS)

    In order to evaluate integrity of PWR primary coolant pipes, four-point bending test of cast duplex stainless steel pipe specimen had been conducted for seven years until March 2006. Materials testing of tensile properties and fracture toughness, and elastic-plastic analysis of crack growth of test pipe specimen were also performed. Simplified prediction curves of stress vs. strain and fracture toughness (J kJ/m2) of cast stainless steel were prepared for parameters of ferrite number, thermal aging temperature and period. Four-point bending test of pipe specimen with initial inner crack measured load vs. displacement and crack growth curve and showed fracture behavior. Plastic collapse occurred before thermal aging, and ductile crack growth due to thermal aging and tearing instability followed. Ductile crack growth behavior of thermally aged specimen was tested. Numerical analysis of test pipe specimen was performed to simulate ductile crack growth behavior based on obtained stress vs. strain curve and compared with J (kJ/m2) vs. crack depth (mm) curve in good conformity. Numerical analysis of full size pipe based on validated method of test specimen analysis was performed to establish database of J (kJ/m2) for evaluation of thermally aged cast stainless steel piping (T. Tanaka)

  12. Moessbauer measurements of microstructural change in aged duplex stainless steel

    International Nuclear Information System (INIS)

    A duplex stainless steel (ASME SA351 CF8M) has usually been manufactured by a continuous casting technique. It consists of a paramagnetic austenite phase and a ferromagnetic ferrite phase. It has been known that the ferrite phase decomposition occurs in this steel after aging between 300 and 450 C. As a result of phase decomposition, a Fe-rich phase and a Cr-rich phase are produced in the ferrite phase. It is difficult to detect the phase decomposition even by not only optical microscopy but also transmission electron microscopy, since the decomposed structure is very fine. However, Moessbauer measurements that can detect the magnetic hyperfine field of magnetic substance may detect the microstructural change. An averaged magnetic hyperfine field increases in the ferrite phase, due to the production of the Fe-rich phase which has high magnetic hyperfine field. Therefore, the authors investigated the phase decomposition of the duplex stainless steel caused by aging, utilization Moessbauer spectroscopy which has capability of detecting this structural change in the atomic level quantitatively. The authors also investigated the potential of backscattering Moessbauer method for NDE technique

  13. Study on thermal aging mechanism of cast duplex stainless steel

    International Nuclear Information System (INIS)

    Cast duplex stainless steel is used for reactor coolant piping in pressurized water reactors. However, its toughness is reduced by aging after long time operation. R and D on non-destructive techniques for evaluating the level of aging during in-service inspections has been carried out. A practical technique to evaluate accuracy has not, however, been developed yet. This is because the relationship between microstructural changes and mechanical property changes has not been clearly identified. The aim of this study is to clarify the relationship between the microstructural and mechanical property changes due to aging by examining the process of generation of precipitates. The specimens used in this study were SCS 14 A centrifuged cast stainless steel with three different ferrite content types of 8, 15 and 23%. They were aged at temperatures of 350degC and 400degC for up to 10,000 hours. The mechanical properties were investigated with Charpy impact testing and Vickers hardness testing, and microstructural changes studied with a transmission electron microscope, atom probe analysis and Moessbauer spectroscopy. As a result, the Charpy impact value of the specimen with larger ferrite content decreased the most. The hardness of the austenite phase remained almost unchanged while the hardness of the ferrite phase significantly increased. The ferrite hardness increase and the phase decomposition rate were almost the same among the three specimens with different ferrite contents. G phase precipitation was observed for the ferrite materials of 15% and 23% after the long period of thermal aging. In conclusion, the thermal aging degradation can be evaluated by detecting the ferrite phase decomposition rate, the ferrite content and the G phase precipitation. (author)

  14. Evaluation of thermal aging embrittlement of duplex stainless steels by electrochemical method

    International Nuclear Information System (INIS)

    Cast duplex stainless steels composed of austenite and ferrite phases have several superior properties due to the presence of ferrite phase, and are used for fabricating important components whose integrity is vital for the safe operation of certain nuclear power plant systems. It has been known, however, that these materials suffer a loss of toughness when exposed to the operating temperature of nuclear power reactors over a long period, and that the embrittlement of the ferrite phase due to spinodal decomposition (SD) is the main cause of thermal aging embrittlement of duplex stainless steels. The purpose of the present study is to develop an electrochemical method by which thermal aging embrittlement of duplex stainless steels can be evaluated nondestructively. By polarization experiments in H2SO4 solution containing 0.005M KSCN, the embrittlement of ferrite phase, the main cause of thermal aging embrittlement of duplex stainless steels, was detected and the correlation between microhardness and electrochemical property changes was obtained

  15. The influence of aging on the intergranular corrosion of 22 chromium-5 nickel duplex stainless steel

    International Nuclear Information System (INIS)

    Duplex stainless steels are widely used in severe corrosion environments because of their good corrosion performance. This paper deals with the influence of aging treatments on the intergranular corrosion (IGC) resistance of a commercial duplex stainless steel, SAF 2205. Duplex stainless steel was given aging treatments in the range 773-1173 K for time periods ranging from 6 min to 100 h. Optical microscopy and XRD was carried out on the aged stainless steels for the microstructural study. The aged samples were evaluated for the IGC susceptibility with the ASTM standard practices. Potentiodynamic cyclic polarization studies were also carried out to investigate the influence of aging treatments on the passivity breakdown. The results indicate that the sigma phase gets precipitated and is responsible for grain boundary attack. (author)

  16. Z factors for aged cast duplex stainless steel pipes and welds

    International Nuclear Information System (INIS)

    This paper provides the Z factors of aged cast duplex stainless steel pipes and their welds with circumferential through-wall crack obtained form the Japanese material data. Z factors are used for elastic-plastic evaluation in ASME Code Section XI. Stress-strain curve and J-resistance curve taken from the base metal of cast duplex stainless steel with ferrite contents of about 23.5% and its adjoining welds of TIG (Tungsten Inert Gas), SMAW (Shielded Metal Arc Welding), and SAW (Submerged Arc Welding) were used. These material were aged for 20000 to 40000 hours at 400 degrees C. The calculated Z factors were formulated in using the approximation with a linear equation of logarithm to the base ten. The proposed Z factors were compared with the Z factors in ASME Code Section XI. In the case of TIG and SMAW, the proposed Z factors give almost the same as the Z factors in ASME Code Section XI. In the case of SAW and cast stainless steel, the proposed Z factors were higher than the Z factors in ASME Code Section XI. Besides, In order to verify the availability of proposed Z factors, the critical bending moments by Z factors were compared with experimental data of aged cast duplex stainless steel pipes. The proposed Z factor for SAW and aged cast duplex stainless steel would be applied to estimate the failure moment of aged cast duplex stainless steel pipes. (author)

  17. Embrittlement and life prediction of aged duplex stainless steel

    International Nuclear Information System (INIS)

    The stainless steel, for which the durability for long term in high temperature corrosive environment is demanded, is a complex plural alloy. Cr heightens the oxidation resistance, Ni improves the ductility and impact characteristics, Si improves the fluidity of the melted alloy and heightens the resistance to stress corrosion cracking, and Mo suppresses the pitting due to chlorine ions. These alloy elements are in the state of nonequilibrium solid solution in Fe base at practical temperature, and cause aging phenomena such as segregation, concentration abnormality and precipitation during the use for long term. The characteristics of stainless steel deteriorate due to this. Two-phase stainless cast steel, the example of the embrittlement of the material for an actual machine, the accelerated test of embrittlement, the activation energy for embrittlement, and as the mechanism of aging embrittlement, the spinodal decomposition of ferrite, the precipitation of G phase and the precipitation of carbides and nitrides are described. Also in the welded parts of austenitic stainless steel, delta-ferrite is formed during cooling, therefore, the condition is nearly same as two-phase stainless steel, and the embrittlement due to long term aging occurs. (K.I.)

  18. Non-destructive evaluation of thermal aging of duplex stainless steel using ultrasonic waves

    International Nuclear Information System (INIS)

    Duplex stainless steel is frequently used under severe environment due to its excellent material strength, toughness and superior corrosion resistance. However, it is known that material deterioration referred to as thermal aging occurs when this material is exposed to high temperatures for a long time. As a result, the material toughness is deteriorated and its mechanical properties are degraded. In this study, to evaluate the degrees of the deteriorated toughness of duplex stainless steel non-destructively, we investigated relation between material structure, mechanical properties and velocity of ultrasonic wave in the material. Based on the result, we have verified the practical applicability of the non-destructive evaluation of thermal aging of duplex stainless steel by ultrasonic velocity measurement. (author)

  19. Non-destructive evaluation of thermal aging of cast duplex stainless steel

    International Nuclear Information System (INIS)

    Cast duplex stainless steel is frequently used in main coolant pipes and reactor coolant pump casings of nuclear power plants due to its excellent material strength, toughness and superior corrosion resistance. However, it is known that material deterioration referred to as thermal aging occurs when this material is exposed to high temperature over 300degC for a long time. As a result, the material toughness decreases. Therefore in managing the components made of the cast duplex stainless steel, it is necessary to evaluate non-destructively the change in the mechanical property caused by thermal aging. In this study, to develop a non-destructive technique for evaluating the deterioration of toughness in cast duplex stainless steel caused by thermal aging, we compared 5 kinds of evaluation techniques, ultrasonic sound velocity measurement, thermoelectric power measurement, resistivity measurement, SQUID (Superconducting Quantum Interference Device) measurement and positron annihilation line-shape analysis for detecting ability of thermal aging. As a result, the thermoelectric power measurement is the most effective technique for evaluating thermal aging of duplex stainless steel because of the closest correlation between non-destructive parameter and toughness and because of low deviation of measured values. (author)

  20. Hardening of aged duplex stainless steels by spinodal decomposition.

    Science.gov (United States)

    Danoix, F; Auger, P; Blavette, D

    2004-06-01

    Mechanical properties, such as hardness and impact toughness, of ferrite-containing stainless steels are greatly affected by long-term aging at intermediate temperatures. It is known that the alpha-alpha' spinodal decomposition occurring in the iron-chromium-based ferrite is responsible for this aging susceptibility. This decomposition can be characterized unambiguously by atom probe analysis, allowing comparison both with the existing theories of spinodal decomposition and the evolution of some mechanical properties. It is then possible to predict the evolution of hardness of industrial components during service, based on the detailed knowledge of the involved aging process. PMID:15233853

  1. Phase transformations in ferrite phase of a duplex stainless steel aged at 500 degree C

    International Nuclear Information System (INIS)

    Due to their high strength, high corrosion resistance, and good properties of castings, duplex stainless steels are widely used in the recirculation system of nuclear power plants. Although the presence of ferrite phase increases the strength and the resistance to SCC, the ferrite phase also brings about thermal aging embrittlement known as ''475 C embrittlement''. The room temperature impact strength can decrease by 80% after aging for 8 years at a temperature as low as 300 C. Much research has been performed on the low temperature embrittlement of duplex stainless steels. It is generally acknowledged that the spinodal decomposition in ferrite phase and precipitation of some other carbides or nickel silicide are responsible for the degradation in mechanical properties of duplex stainless steels at low temperatures. The extent of the degradation was found to be strongly dependent on the composition in ferrite, which is closely related to the change of microstructure. Thus, the exact evolution of phase transformation in ferrite has also drawn a large audience. In this study, using electron microscopy, the authors investigated the phase evolution of ferrite phase in duplex stainless steel, aged at 500 C. up to 10,000 hours

  2. Non-destructive evaluation of thermal aging of cast duplex stainless steel

    International Nuclear Information System (INIS)

    Cast duplex stainless steel is frequently used in main coolant pipes and reactor coolant pump casings in nuclear power plants because of its excellent material strength, toughness and superior corrosion resistance. It is known, however, that thermal aging occurs when this material is exposed to temperatures over 300degC for extended periods of time. As a result, the material toughness decreases. It is necessary therefore to evaluate changes in the mechanical properties of this material caused by thermal aging using non-destructive methods for the maintenance and management of components made of cast duplex stainless steel. In order to develop a non-destructive technique for evaluating the toughness reduction of cast duplex stainless steel due to thermal aging, five types of non-destructive techniques were compared. These include ultrasonic sound velocity measurement, the thermoelectric power measurement the electric resistance method, the SQUID (Superconducting Quantum Interface Device) method, and the positron annihilation method. The thermal aging detectability of each technique was compared and examined in experiments using specimens on which accelerated thermal aging had been carried out. It was concluded that the thermoelectric power measurement was the most effective technique for evaluating thermal aging because the correlation coefficient between the non-destructive evaluation parameters and the mechanical properties of aged materials was high and the dispersion of measurements was small. (author)

  3. Non-destructive evaluation of thermal aging of cast duplex stainless steel using thermoelectric power measurement

    International Nuclear Information System (INIS)

    Cast duplex stainless steel is frequently used in main coolant pipes of PWR (Pressurized water reactor) type nuclear power plants because of its excellent material strength, toughness and superior corrosion resistance. However, it is known that material deterioration referred to as thermal aging occurs when this material is exposed to temperatures over 300degC. As a result, the material toughness decreases. Therefore, in managing the components made of cast duplex stainless steel, it is necessary to evaluate non-destructively such deterioration. In this study, measurement of thermoelectric power, which is sensitive to micro-structural change in materials, was used for the evaluation of thermal aging. First, we investigated change in mechanical properties (hardness, tensile stress and notch toughness) due to thermal aging in cast duplex stainless steel. Secondly we measured thermoelectric power (TEP) and investigated change in TEP de to thermal aging and the effect of temperature of a specimen on TEP.Then the TEP was compared with the mechanical properties. As a result, TEP increases with aging time and the tendency becomes more remarkable as ferrite content increases. The increase in TEP of a specimen with 21.3% ferrite due to thermal aging (400degC-10000 h) is 0.61 μV/degC. The TEP slightly decreases with temperature of the specimen at a rate of about -0.009 μV/degC2. Finally we found good correlation between the TEP and ductile-brittle transition temperature, the TEP and notch toughness at 325degC. The correlation coefficients are respectively 0.886∼0.957 and -0.890∼ -0.978. Therefore, by using TEP measurement, material deterioration of cast duplex stainless steel due to thermal aging can be evaluated. (author)

  4. Analysis of phase separation by thermal aging in duplex stainless steels by magnetic methods

    International Nuclear Information System (INIS)

    The phase separation in ferrite phase of duplex stainless steel is the primary cause of thermal aging embrittlement of the LWR primary pressure boundary components. In this study the phase separation of simulated duplex stainless steel was detected by Mossbauer spectroscopy and magnetic property analysis by VSM (Vibrating Specimen Magnetometer). The simulated duplex stainless steels, Fe-Cr binary, Fe-Cr-Ni Temary, and Fe-Cr-Ni-Si quaternary alloys, were aged at 370 and 400 deg C up to 5,340 hours. It was observed from Mossbauer spectra analysis that internal magnetic field increases with aging time and from VSM that the specific saturation magnetization and Curie temperature increase with aging time. These results are indicative that phase separation into Fe-rich region and Cr-rich region is caused by thermal aging in the temperature range of 370 - 400 deg C. In cases specimens containing Ni, the increase of specific saturation magnetization is much higher. This implies that Ni seems to promote Fe-Cr interdiffusion, which accelerates the phase separation into Fe-rich α phase and Cr-rich α' phase. (author)

  5. Sigma phase morphologies in cast and aged super duplex stainless steel

    International Nuclear Information System (INIS)

    Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature. These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material's impact strength. The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 deg. C and 980 deg. C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 deg. C and block-shaped when heat treated at 980 deg. C.

  6. Evaluation of thermal aging embrittlement of duplex stainless steels by electrochemical method

    International Nuclear Information System (INIS)

    Electrochemical methods were employed as nondestructive means of evaluation of thermal aging embrittlement of cast duplex stainless steels. Potentiodynamic polarization experiments for duplex stainless steels of CF8 grade and Fe30Cr5Ni alloy steels aged at 370 .deg. C and 400 .deg. C for up to 7,000h were conducted in four different electrolytic solutions to detect degradation caused by spinodal decomposition in the ferrite phase. Microhardness measurements were also made to study correlation with results from electrochemical experiments. In polarization experiments conducted in 5wt% CH3COOH solution, the anodic peak current density ipeak increased, depending on aging time. Preferential dissolution of either the ferrite or the austenite phase, however, could not be determined by scanning electron microscope of the specimens after polarization experiments to the potential Epeak at which the peak current density ipeak occurred. Changes of the peak current density ipeak corresponding to the formation of Cr-depleted zone due to carbide precipitation at α/γ boundaries, could be observed by polarization experiments conducted in the mixture of 0.5M H2SO4 and 0.01M KSCN. In polarization experiments for duplex stainless steel specimens conducted in the mixture of 0.05M H2SO4 and 0.01M KSCN and the mixture of H2SO4 and 0.005M KSCN, two current density peak, ipeak1 and ipeak2, appeared. ipeak1 was attributed to preferential dissolution of the ferrite phase and decreased by aging, while ipeak2 was caused by preferential dissolution of the austenite phase and was regardless of aging conditions. Scanning electron microscope and atomic force microscope observations indicated that the decrease of ferrite dissolution in aged specimens was the cause for the decrease of ipeak1. This appeared to be attributed to spinodal decomposition occurring in the ferrite phase that is the main cause of thermal aging embrittlement, from the consideration of results on polarization experiments

  7. Aging embrittlement and lattice image analysis in a Fe-Cr-Ni duplex stainless steel aged at 400 C

    International Nuclear Information System (INIS)

    Aging embrittlement, normally observed in ferritic stainless steels, was found in a Fe-Cr-Ni duplex stainless steel thermally aged at 400 C for a long time. The ferrite content and composition of the duplex stainless steel was changed by varying the solution annealing temperature in order to investigate the effect of ferrite phase on the aging embrittlement. The material was aged at 400 C up to 10 000 h. Aging embrittlement was characterized by microhardness and other mechanical tests. The results show that the aging embrittlement of the duplex stainless steel was attributed to the degradation in ferrite phase. Microstructural studies in the ferrite phase indicated that spinodal decomposition and G-phase precipitation led to the degradation. High resolution electron microscopy (HREM) was utilized to analyze the lattice images of G-phase and ferrite matrix. The extent of embrittlement was found to be strongly dependent on the ferrite content and the composition in ferrite. The Ni content in ferrite seems to play an important role in aging embrittlement by promoting G-phase precipitation. As Ni content increased in the ferrite, the degradation of the material aged at 400 C became more severe. ((orig.))

  8. Effects of prior solution treatment on thermal aging behavior of duplex stainless steels

    International Nuclear Information System (INIS)

    The influence of solution temperature on thermal aging behavior was studied in duplex stainless steels. With increasing solution temperature, the ferrite contents remarkably increase, Cr and Ni elements redistribute. During thermal aging, the impact properties of higher solution temperature treated materials suffer a serious degradation, which is not only related with ferrite content but also the alloy compositions in ferrite. Enrichment of Ni in ferrite can accelerate the spinodal decomposition kinetics. Thermal aging-inducing strain fields in ferrite cause the embrittlement of DSS

  9. Study and prediction model on low temperature aging embrittlement in duplex stainless steels

    International Nuclear Information System (INIS)

    Within the framework of a general study on low temperature (280-400 degree centigree) aging embrittlement in duplex stainless steels, a relationship has been obtained between aging, measured from ferrite hardness evolution, and bulk materials embrittlement, determined from fracture toughness and fracture impact tests. The existing correlation between the increase in ferrite hardness and its percentage presence in the fracture path supports this relationship and results in the development of a prediction design model which provides the fracture resistance curves, for any aging level, based on the chemical composition and the steel's properties in an unaged state. (Author)

  10. Effect of thermal aging conditions on the corrosion properties and hardness of a duplex stainless steel

    OpenAIRE

    José Eduardo May; Carlos Alberto Caldas de Souza; Pedro Augusto de Paula Nascente; Paulo Soares; Carlos Mauricio Lepienski; Sebastião Elias Kuri

    2010-01-01

    The corrosion properties of a 22.5 wt. (%) Cr duplex stainless steel were investigated after long-term aging of 3000, 5000 and 7000 hours at 300 and 400 ºC. The corrosion resistance was measured based on mass loss in a FeCl3 10 wt. (%) solution and electrochemical measurements in a 0.1 M H2SO4 solution. The results indicate that the corrosion resistance decreased steadily up to 5000 hours of aging. However, the samples subjected to 7000 hours of aging showed better corrosion resistance than t...

  11. Effect of Aging Time on the Resistance to Localized Corrosion of the Hyper Duplex Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Soon Hyeok; Kim, Soon Tae; Lee, In Sung; Park, Yong Soo [Yonsei University, Seoul (Korea, Republic of); Kim, Ji Soo; Kim, Kwang Tae [POSCO Technology Research Laboratories, Pohang (Korea, Republic of)

    2010-10-15

    To elucidate the effect of aging time on resistance to localized corrosion of hyper duplex stainless steel, a double-loop electrochemical potentiokinetic reactivation test a potentiodynamic anodic polarization test, a scanning electron microscope-energy dispersive spectroscope analysis, and a thermodynamic calculation were conducted. With an increase in aging time, sigma phases are precipitated much more than chi phases due to the meta-stable chi phase acting as a transition phase. As aging time at 850 .deg. C increases, the corrosion resistance decreases owing to an increase in Cr, Mo and W depleted areas adjacent to the intermetallic phases such as sigma phases and chi phases.

  12. Effects of prior solution treatment on thermal aging behavior of duplex stainless steels

    Science.gov (United States)

    Li, Shilei; Wang, Yanli; Zhang, Hailong; Li, Shuxiao; Wang, Genqi; Wang, Xitao

    2013-10-01

    The influence of solution temperature on thermal aging behavior was studied in duplex stainless steels. With increasing solution temperature, the ferrite contents remarkably increase, Cr and Ni elements redistribute. During thermal aging, the impact properties of higher solution temperature treated materials suffer a serious degradation, which is not only related with ferrite content but also the alloy compositions in ferrite. Enrichment of Ni in ferrite can accelerate the spinodal decomposition kinetics. Thermal aging-inducing strain fields in ferrite cause the embrittlement of DSS.

  13. Microstructures of cast-duplex stainless steel after long-term aging

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Chopra, O.K.

    1985-10-01

    Microstructures of cast-duplex stainless steels subjected to long-term aging either in the laboratory or during in-reactor service have been characterized and compared by TEM, SEM, and optical microscopy. The microstructural characteristics have been correlated with the impact failure behavior of the material. G-phase, ', and an unidentified Type X precipitate were responsible for the ferrite-phase embrittlement. Precipitation of M23C6 carbides on austenite-ferrite boundaries further degraded the reactor-aged material.

  14. Influence of Thermal Aging on Primary Water Stress Corrosion Cracking of Cast Duplex Stainless Steels

    International Nuclear Information System (INIS)

    In order to evaluate the SCC (stress corrosion cracking) susceptibility of cast duplex stainless steels which are used for the main coolant piping material of pressurized water reactors (PWRs), the slow strain rate test (SSRT) and the constant load test (CLT) were performed in simulated PWR primary water at 360 C. The main coolant piping materials contain ferrite phase with ranging from 8 to 23 % and its mechanical properties are affected by long time thermal aging. The 23% ferrite material was prepared for test as the maximum ferrite content of main coolant pipes in Japanese PWRs. The brittle fracture in the non-aged materials after SSRT is mainly caused by quasi-cleavage fracture in austenitic phase. On the other hand, a mixture of quasi-cleavage fracture in austenite and ferrite phases was observed on long time aged material. Also on CLT, (2 times σy), after 3,000 hours exposure, microcracks were observed on the surface of non-aged and aged for 10,000 hours at 400 C materials. The crack initiation site of CLT is similar to that of SSRT. The SCC susceptibility of the materials increases with aging time. It is suggested that the ferrite hardening with aging affect SCC susceptibility of cast duplex stainless steels. (authors)

  15. Local Approach to Fracture of an Aged Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Alfredo Hazarabedian

    2002-06-01

    Full Text Available The local approach to fracture (LAF is a methodology aimed to calculate macroscopic fracture properties of a body, from the knowledge of the local stress - strain field at the fracture site, and the modeling of the acting fracture mechanisms. In the present work, this method was applied to a CF8M steel, aged 30000h at 325 °C, in order to elucidate if LAF could be able to describe the measured fracture toughness data. We have simulated the elastoplastic behavior using the Gurson model and the general methodology of Joly. The required parameters were obtained from the stress strain curve and from the damage progression study by quantitative metallography. We extended the validity of that methodology for a material aged in a more realistic condition, i.e. at a relatively lower temperature and for a longer time. The model was found satisfactory because it was able to describe the experimental distribution of the fracture probability vs. fracture strain of notched axisymmetric specimens, without any parameter fitting. The model also predicted the lower bound of the experimental distribution of the crack resistance at 0.2 mm of crack extension (J02.

  16. Secondary Hardening Behavior in Super Duplex Stainless Steels during LCF in Dynamic Strain Ageing Regime

    OpenAIRE

    Chai, Guocai; Andersson, Marcus

    2013-01-01

    Cyclic deformation behaviors in five modified duplex stainless steel S32705 grades have been studied at 20 °C, 200 °C, 250° and 350 °C. The influence of temperature and nitrogen concentration on the occurrence of the second hardening phenomenon, in the stress response curve was focused. An increase in nitrogen concentration can have a positive effect on dynamic strain ageing by increasing the first hardening and also the second hardening behavior during cyclic deformation. Furthermore, an inc...

  17. Microstructural Evolution in 2101 Lean Duplex Stainless Steel During Low- and Intermediate-Temperature Aging.

    Science.gov (United States)

    Maetz, Jean-Yves; Cazottes, Sophie; Verdu, Catherine; Danoix, Frédéric; Kléber, Xavier

    2016-04-01

    The microstructural evolution of a 2101 lean duplex stainless steel (DSS) during isothermal aging from room temperature to 470 °C was investigated using thermoelectric power (TEP) measurements to follow the kinetics, atom probe tomography, and transmission electron microscopy. Despite the low Ni, Cr, and Mo contents, the lean DSS was sensitive to α-α' phase separation and Ni-Mn-Si-Al-Cu clustering at intermediate temperatures. The time-temperature pairs characteristic of the early stages of ferrite decomposition were determined from the TEP kinetics. Considering their composition and locations, the clusters are most likely G phase precursors. PMID:26940550

  18. Effect of thermal aging on the fatigue crack growth behavior of cast duplex stainless steels

    Science.gov (United States)

    Lü, Xu-ming; Li, Shi-lei; Zhang, Hai-long; Wang, Yan-li; Wang, Xi-tao

    2015-11-01

    The effect of thermal aging on the fatigue crack growth (FCG) behavior of Z3CN20?09M cast duplex stainless steel with low ferrite content was investigated in this study. The crack surfaces and crack growth paths were analyzed to clarify the FCG mechanisms. The microstructure and micromechanical properties before and after thermal aging were also studied. Spinodal decomposition in the aged ferrite phase led to an increase in the hardness and a decrease in the plastic deformation capacity, whereas the hardness and plastic deformation capacity of the austenite phase were almost unchanged after thermal aging. The aged material exhibited a better FCG resistance than the unaged material in the near-threshold regime because of the increased roughness-induced crack closure associated with the tortuous crack path and rougher fracture surface; however, the tendency was reversed in the Paris regime because of the cleavage fracture in the aged ferrite phases.

  19. Study of the fatigue behaviour and damage of a aged duplex stainless steel

    International Nuclear Information System (INIS)

    Cast duplex stainless steels are commonly used in components of pressurized water reactors primary circuit. When submitted to in-service temperatures embrittlement occurs because of the nucleation and growth of a harder phase in the ferrite by spinodal composition. Macrostructure of this steel (ferritic primary grain size is about 4-5 mm) and embrittlement of ferrite due to aging lead to a very high scattering of mechanical properties for monotonous loadings. We showed that, in spite of this macrostructure, the cyclic behaviour of aged duplex stainless steels fits usual Manson-Coffin law while initial hardening is followed by softening, in part because of the demodulation of the composition. The fatigue crack propagation rate of material follows a Paris law. While crack initiation mainly appears next to the millimetric cast defects, fatigue crack propagation remains a continuous mechanism. Ferritic and austenitic elements break successively (ferrite first breaks by cleavage, then austenite breaks by ductile fatigue). In spite of the fact that the aged ferrite is embrittled, cleavage microcracks, for load levels examined, seldom appear in ferrite at the crack tip and on both sides of the main crack. Effects of cast defects and crystallographic ferrite orientation were also studied. Propagation fatigue crack behaviour was modeled assuming that the crack tip material behaves as if it was submitted to low cycle fatigue loadings. If we consider a homogeneous material, results are in good agreement with experiments. (authors)

  20. Evaluation of thermal aging embrittlement in CF8 duplex stainless steel by small punch test

    International Nuclear Information System (INIS)

    Small punch test was performed on CF8 duplex stainless steel aged at 370 and 400 deg. C for up to 5000 h to characterize thermal aging embrittlement. At room temperature, the small punch (SP) load-displacement curve was similar in shape to those of ferritic steels and exhibited a good reproducibility in spite of ferrite-austenite structure. As the test temperature was lowered to a certain temperature depending on the degree of aging, the SP load showed a sudden drop followed by curve serration before the SP specimen fractured, resulting from the cracking of ferrite phase. While the aging heat treatment led to a slight increase of the yield strength, the transition appearing in the SP energy versus temperature curves shifted to higher temperature due to the hardening of ferrite phase. Additionally, phase boundary separation was an important factor in the degradation of the steel aged at 400 deg. C

  1. Effect of thermal aging conditions on the corrosion properties and hardness of a duplex stainless steel

    Directory of Open Access Journals (Sweden)

    José Eduardo May

    2010-12-01

    Full Text Available The corrosion properties of a 22.5 wt. (% Cr duplex stainless steel were investigated after long-term aging of 3000, 5000 and 7000 hours at 300 and 400 ºC. The corrosion resistance was measured based on mass loss in a FeCl3 10 wt. (% solution and electrochemical measurements in a 0.1 M H2SO4 solution. The results indicate that the corrosion resistance decreased steadily up to 5000 hours of aging. However, the samples subjected to 7000 hours of aging showed better corrosion resistance than those aged for 3000 and 5000 hours. This effect is attributed to the phase transformation that occurs during aging, a finding which was confirmed by hardness, transmission electron microscopy and X-ray photoelectron spectroscopy measurements.

  2. Thermal-aging evaluation of on site aged cast duplex stainless steel

    International Nuclear Information System (INIS)

    Cast duplex stainless steel was widely used for main coolant pipe in pressurized water reactors, they can suffer a loss of toughness after long-term thermal-aging. To evaluate mechanical properties of such as thermal-aged materials was investigated in laboratory using accelerated aged materials. In addition, to investigate the degradation mechanism, micro-structural behaviors were also investigated. According to such as laboratory data, main cause of degradation of these materials was considered ferrite hardening by spinodal decomposition and G-phase precipitation in the ferrite phase. In this study, thermal-aging evaluation has been performed using service aged elbow pipe in PWR plant, aged at 320℃ for 196,500h. Thermal-aging were evaluated using atom-probe analysis, scanning transmission electron microscope, and micro-Vickers hardness measurement. And then those parameters were compared accelerated thermal-aged materials. As a result, micro Vickers hardness of ferrite in service material (SCS14A), HV(0.025) was 616-630. Since micro Vickers hardness of un-aged ferrite phase is about HV(0.025)=300 in commercial SCS14A, the increasing of ferrite hardness during aging was 300. Cr-rich and Fe-rich regions were observed in the ferrite phase using Atom-probe analysis. In addition, Ni, Si and Mo clustering were also observed in the ferrite phase. So the ferrite phase was hardened caused by these micro-structural changes. Micro Vickers hardness of austenite phase, HV (0.025) was 155-180. Since micro Vickers hardness of un-aged austenite phase is about HV (0.025)=180-200, and no micro-structural change was observed in the austenite phase, so no change was observed in the austenite phase during aging. To compare the micro Vickers hardness of ferrite in service and accelerated materials using activation energy, Q=100kJ/mol, the ferrite hardness of in service material was very low rather than predictive line. This seems the activation energy was too conservative. (author)

  3. Spinodal decomposition of austenite in long-term-aged duplex stainless steel

    International Nuclear Information System (INIS)

    Spinodal decomposition of austenite phase in the cast duplex stainless steels CF-8 and -8M grades has been observed after long- term thermal aging at 400 and 350/degree/C for 30,000 h (3.4 yr). At 320/degree/C, the reaction was observed only at the limited region near the austenite grain boundaries. Ni segregation and ''worm-holes'' corresponding to the spatial microchemical fluctuations have been confirmed. The decomposition was observed only for heats containing relatively high overall Ni content (9.6--12.0 wt %) but not in low-Ni (8.0--9.4 wt %) heats. In some specimens showing a relatively advanced stage of decomposition, localized regions of austenite with a Vickers hardness of 340--430 were observed. However, the effect of austenite decomposition on the overall material toughness appears secondary for aging up to 3--5 yr in comparison with the effect of the faster spinodal decomposition in ferrite phase. The observation of the thermally driven spinodal decomposition of the austenite phase in cast duplex stainless steels validates the proposition that a miscibility gap occurs in Fe-Ni and ancillary systems. 16 refs., 7 figs., 1 tab

  4. 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)

  5. Large-scale tests on aged cast duplex stainless steel elbows: results and lessons drawn

    International Nuclear Information System (INIS)

    Some components of the primary loop of French PWRs are made of cast duplex stainless steels. This kind of steel may age even at relatively low temperatures (in the temperature range of PWR service conditions), depending on the material composition. An important consequence of this aging process is the decrease in the ductility and fracture toughness of the material. It is feared that an embrittlement, associated with the occurrence of casting defects, may increase the risk of failure. Therefore, an extensive programme has been launched by EDF in co-operation with Framatome, in order to determine acceptability criteria for operating cast stainless steel components. This paper presents the main characteristics and results of the aged cast elbow experiments. These elbows contained ( analytical ) machined notches (semi-elliptical surface defect or through-wall defect) and were tested under in-plane bending, with or without internal pressure. During the tests, the defects initiated and grew subsequently by ductile tearing. The tests were interrupted when a significant amount (about 10 mm) of crack growth was reached. For each test, a detailed fracture mechanics analysis, based on finite element calculations, was performed. These calculations accurately simulated the overall behaviour of the tested structure, gave in each case a good prediction of the crack initiation load and conservatively predicted the load associated to the final crack size. These tests and their detailed analyses contribute to validate and justify the methodology used in the integrity assessment of in-service cast stainless steel components. (author)

  6. Long-term aging embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    The primary objectives of this program are to investigate the significance of in-service embrittlement of cast duplex stainless steels in light water reactor (LWR) systems and to evaluate possible remedies for the embrittlement problem in existing and future plants. The scope of the investigation includes three goals: (1) develop a methodology and correlations for predicting the toughness loss suffered by cast stainless steel components during normal and extended life of LWRs, (2) validate the simulation of in-reactor degradation by accelerated aging, and (3) establish the effects of key compositional and metallurgical variables on the kinetics and extent of embrittlement. The emphasis during the current year was on developing a procedure and correlations for predicting fracture toughness J-R curves of aged cast stainless steels from known material information. The present analysis has focused on developing correlations for the fracture properties in terms of material information that can be determined from the certified material test record (CMTR) and on ensuring that the correlations are adequately conservative for structurally weak materials

  7. The lean duplex stainless steel welded joint after isothermal aging heat treatment

    Directory of Open Access Journals (Sweden)

    Z. Brytan

    2013-03-01

    Full Text Available Purpose: The purpose of this paper is the microstructural evaluation of the lean duplex stainless steel UNS S32101 (EN 1.4162 welded joints after isothermal aging heat treatment at 650°C. The scanning electron microscopy (SEM and electron backscatter diffraction (EBSD was applied in the microstructural analysis.Design/methodology/approach: The welding joints were produced using the metal active gas (MAG method where the filler metal was in wire form grade Avesta LDX 2101. During the process a shielding gas mixture of Ar + 2.5% CO2 was applied and as a forming gas pure technical argon was used.Findings: The welded joint in the as-welded condition shows Cr2N nitride precipitation in the HAZ, while isothermal aging at 650°C for 15 min causes further precipitation of nitrides, both in the parent metal, as well as in the HAZ and the weld area. Increasing the aging time at this temperature to 90 min causes the formation of numerous nitrides at the grain boundaries of austenite and ferrite and nitride precipitation inside ferritic grains in each zone of the welded joint.Research limitations/implications: The electron backscatter diffraction of particular zones of the welded joints considered only austenite and ferrite and their character was evaluated, while small precipitates like chromium nitrides were omitted in this study and will be evaluated in the further work.Originality/value: Sometimes the production cycle involves the heat treatment of welded components made of lean duplex stainless steel. In such situations the additional heating of the welds and heat affected zone can produce carbides, nitrides or sigma phase precipitation - the extent of which depends on the temperature and time of heat treatment. These issues are widely reported in relation to the base material but not when considering welded joints, which may behave differently

  8. Investigation of thermal aging damage mechanism of the Cast Duplex Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhaoxi, E-mail: wangzx03@mails.tsinghua.edu.c [Applied Mechanics Laboratory, Tsinghua University, Beijing 100084 (China); Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Xue Fei; Guo Wenhai [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Shi Huiji [Applied Mechanics Laboratory, Tsinghua University, Beijing 100084 (China); Zhang Guodong [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); School of Mechanical and Power Engineering, Nanjing University of Technology, Nanjing 210009 (China); Shu Guogang [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China)

    2010-10-15

    Besides the macro-mechanical properties for thermal aging effect published in 'Thermal aging effect on Z3CN20.09M Cast Duplex Stainless Steel' (Nuclear Engineering and Design 239(2009) 2217-2223), the thermal aging damage mechanism is investigated in this paper through nano-indentation tests and micro-structures evolution examination. Numerical simulations were carried out with GTN continuum damage model to investigate the different crack propagation process for aging. The nano-indentation hardness values increase with aging time for both phases while the hardness values of the ferrite phase are much higher and increase much more. The nano-indentation energy indicating the toughness decreases for both phases with aging time. TEM results show that the Cr-enriched {alpha}' phase precipitates in the ferrite phase which is considered as the critical reason making the dislocation slip difficult and causing the increase of the strength and reduction of the toughness. The crack initiates from the ferrite phase instead of the austenite phase from the SEM observation and FEA simulation results, which reflects the change of the fracture mechanism for thermal aging.

  9. Estimation of Charpy notch toughness for thermal aging specimens of cast duplex stainless steel using thermalelectric power measurement

    International Nuclear Information System (INIS)

    The material properties of cast duplex stainless steel, which is used for main coolant pipes of PWR (pressurized water reactor) type nuclear power plants, change due to thermal aging. Therefore it is advisable to evaluate these changes of material properties non-destructively for maintenance of the plant component. In order to establish a non-destructive evaluation procedure for the degree of thermal aging of cast duplex stainless steel, thermoelectric power (TEP) measurements were carried out with a newly made TEP meter for thermal aging specimens, with different ferrite contents, aging temperatures and aging periods. Then the relationship between TEP and notch toughness obtained by Charpy impact test was investigated. As the results: (1) TEP increases due to thermal aging. The higher ferrite content, the higher TEP. The higher aging temperature, the more rapidly TEP increases. (2) Because of the decrease of Charpy notch toughness and the increase of TEP due to the fluctuation of Cr concentration caused by the phase separation of the ferrite phase, TEP increases by thermal aging as the Charpy notch toughness decreases. (3) Regardless of the aging temperature, the specimens with the same ferrite content have the same relationship between Charpy notch toughness and TEP. (4) It is possible to estimate Charpy notch toughness with an error of 100 J/cm2 by TEP in the beginning of aging. Therefore, it can be concluded that we can estimate Charpy notch toughness for cast duplex stainless steel by TEP depending on the ferrite content regardless of the aging temperature. (author)

  10. Long term aging of duplex stainless steels. Relationship between toughness properties and metallurgical parameters

    International Nuclear Information System (INIS)

    The long term thermal aging behaviour of a whole series of Molybdenum-bearing and Molybdenum-free heats of cast duplex stainless steels has been studied between 300 and 400 deg C. It has been characterized mainly through the evolution of hardness, microhardness of the ferrite, impact Charpy toughness, Charpy-V notch transitions curves and in some cases in term of resistance to ductile tearing with the aim of establishing predictive knowledge from which the behaviour of real components can be assessed. The large data base collected in this extended programme has allowed to show the influence of metallurgical parameters (in particular ferrite, Cr, Ni, Mo contents, ferrite morphology or final solution heat treatment) on mechanical properties in unaged conditions and after aging. For given Cr and ferrite content, Mo-free heats (having also lower nickel content) age considerably less than Mo-bearing heats at 350 deg C, but tend towards the same behaviour at 400 deg C. The analysis of aging kinetics (from the evolution of impact toughness) for Mo-bearing heats (most sensitive to aging) allowed to deduce a set of apparent activation energies which decrease with increasing aging temperature. With this time-temperature equivalence parameter, extrapolations and predictive toughness curves can be given

  11. Mechanical property and microstructural change by thermal aging of SCS14A cast duplex stainless steel

    International Nuclear Information System (INIS)

    The aging behavior, especially saturation, of JIS SCS14A cast duplex stainless steels was investigated on the basis of the mechanical properties and microstructural changes during accelerated aging at 350 oC and 400 oC. The aging behavior of the materials mainly proceeds via two stages. During the first stage, the generation and concentration of the iron-rich and chromium-enriched phase in ferrite occurs by phase decomposition. The first stage corresponds to aging times of up to 3000 h at 400 oC. During the first stage, the ferrite hardness achieved is approximately 600 VHN, and the Charpy impact energy is almost saturated. During the second stage, the precipitated chromium-enriched phase aggregates and coarsens, and the G phase precipitation also occurs. The second stage corresponds to the aging times range of 3000-30 000 h at 400 oC. During the second stage, the ferrite hardness achieved is about 800 VHN; however, further hardening exceeding 600 VHN does not influence the Charpy impact energy

  12. Effect of Aging Treatment on Impact Toughness and Corrosion Resistance of Super Duplex Stainless Steel

    Science.gov (United States)

    Kim, Jae-Hwan; Oh, Eun-Ji; Lee, Byung-Chan; Kang, Chang-Yong

    2016-01-01

    The effect of aging time on impact toughness and corrosion resistance of 25%Cr-7%Ni-2%Mo-4%W-0.2%N super duplex stainless steel from the viewpoint of intermetallic secondary phase variation was investigated with scanning electron microscopic observation with energy-dispersive x-ray spectroscopic analysis and transmission electron microscopy. The results clarified that R-phase is precipitated not only at the interface of ferrite and austenite but inside the ferrite at an initial stage of aging and then transformed into σ-phase from an aging time of 1 h, while the ferrite phase decomposed into γ2 and σ-phase with increase of aging time. This variation of the phases led to decrease of its impact toughness, and specifically, the R-phase was proved to be predominant in the degradation of the impact toughness at the initial stage of the aging. Additionally, these secondary phases led to deterioration of corrosion resistance because of Cr depletion.

  13. Effect of the manufacturing process on the thermal aging of PWR duplex stainless steel components

    International Nuclear Information System (INIS)

    Some components of the primary loop of Pressurized Water Reactors (pump casings, some elbows, pipes, fittings and valves) are made of cast duplex stainless steels. The manufacturing process of these components has been carefully studied. The manufacturing process consists of a solidification stage followed by heat treatments to homogenize the material (by dissolving the embrittling phases precipitated at the end of the solidification) and set the ferrite content. Apart from the chemical composition, the main manufacturing parameters identified were: the solidification speed depending on foundry practice; the homogenizing heat treatment temperature; the homogenizing heat treatment holding time, the quenching rate after the homogenizing heat treatment. A program of simulation in laboratory of the effect of each of these parameters on the thermal aging has been initiated. This program, run on industrial products cast for studies, completes the aging surveillance programme on test ingots (cast at the same time as components). The metallurgical and mechanical characteristics of the materials (as-quenched and after aging up to 10 000 h at 350 deg C) have been studied. The main results of this parametric study are as follows: the solidification speed affects the morphology of the ferrite-austenite microstructure and the characteristics of the toughness transition curve; the homogenizing heat treatment temperature especially affect the ferrite content of the material and the chemical composition of each phase; the homogenizing heat treatment holding time and the quenching rate affects the beginning of the decomposition of the ferrite and consequently the whole kinetics of aging and embrittlement. (author)

  14. Detection and evaluation of material degradation of thermally aged duplex stainless steels: electrochemical polarization test and AFM surface analysis

    International Nuclear Information System (INIS)

    Thermal aging embrittlement of cast duplex stainless steels was evaluated by Charpy impact test and microhardness measurement. Also, for the purpose of the non-destructive evaluation of thermal aging embrittlement in cast duplex stainless steels, electrochemical polarization measurements for service exposed and laboratory aged materials were carried out in 0.1 M nitric acid solution and the depth of dissolution during the polarization measurement was measured with an atomic force microscope (AFM). In the polarization curves, the peak current densities of all specimens tested were appeared in the negative range of current and aged materials showed larger peak values than unaged ones. In the dissolved depth of austenite phase, no trend can be seen with aging time but those of ferrite phase were increased according to aging time, which has the same tendency as the polarization results. A good correlation between the dissolved depth measured by the AFM and the changes in mechanical properties of materials and, based on these results, an evaluation method for thermal aging embrittlement of duplex stainless steels was suggested. (orig.)

  15. Temper embrittlement of cast duplex stainless steels after long-term aging

    International Nuclear Information System (INIS)

    Microstructural changes and fracture behavior in cast CF8M duplex stainless steel after aging at 300 to 450degC for 300 to 10000 h have been investigated. Both, optical microscopical and transmission electron microscopical analyses, hardness and ferrite content measurements have been carried out in this study. Strengthening and overaging phenomena of the ferrite phase have been identified by hardness measurements. Spinodal decomposition and heterogeneous precipitation of G-phase were found to be responsible for strengthening of the ferrite phase after aging with a temper parameter P in the range ca. 1.8 to 4.0. Homogeneous precipitation of noncoherent α'- and G-phases in ferrite, identified by both optical and transmission electron microscopical analyses for aging with P > 4.0 at 450degC, is associated with overaging phenomena. Three different fracture modes, dimples, cleavage and α/γ grain boundary separation, have been observed for Charpy V-notch and CT test specimens fractured at +20degC. (author)

  16. Precipitation and Phase Transformations in 2101 Lean Duplex Stainless Steel During Isothermal Aging

    Science.gov (United States)

    Maetz, Jean-Yves; Cazottes, Sophie; Verdu, Catherine; Kleber, Xavier

    2016-01-01

    The effect of isothermal aging at 963 K (690 °C) on the microstructure of a 2101 lean duplex stainless steel, with the composition Fe-21.5Cr-5Mn-1.6Ni-0.22N-0.3Mo, was investigated using a multi-technique and multi-scale approach. The kinetics of phase transformation and precipitation was followed from a few minutes to thousands of hours using thermoelectric power measurements; based on these results, certain aging states were selected for electron microscopy characterization. Scanning electron microscopy, electron back-scattered diffraction, and transmission electron microscopy were used to quantitatively describe the microstructural evolution through crystallographic analysis, chemical analysis, and volume fraction measurements from the macroscopic scale down to the nanometric scale. During aging, the precipitation of M23C6 carbides, Cr2N nitrides, and σ phase as well as the transformation of ferrite into austenite and austenite into martensite was observed. These complex microstructural changes are controlled by Cr volume diffusion. The precipitation and phase transformation mechanisms are described.

  17. Accelerated aging embrittlement of cast duplex stainless steel: Activation energy for extrapolation

    International Nuclear Information System (INIS)

    Cast duplex stainless steels, used extensively in LWR systems for primary pressure boundary components such as primary coolant pipes, valves, and pumps, are susceptible to thermal aging embrittlement at reactor operating or higher temperatures. Since a realistic aging embrittlement for end-of-life or life-extension conditions (i.e., 32--50 yr of aging at 280--320 degree C) cannot be produced, it is customary to simulate the metallurgical structure by accelerated aging at ∼400 degree C. Over the past several years, extensive data on accelerated aging have been reported from a number of laboratories. The most important information from these studies is the activation energy, namely, the temperature dependence of the aging kinetics between 280 and 400 degree C, which is used to extrapolate the aging characteristics to reactor operating conditions. The activation energies (in the range of 18--50 kcal/mole) are, in general, sensitive to material grade, chemical composition, and fabrication process, and a few empirical correlations, obtained as a function of bulk chemical composition, have been reported. In this paper, a mechanistic understanding of the activation energy is described on the basis of the results of microstructural characterization of various heats of CF-3, -8, and -8M grades that were used in aging studies at different laboratories. The primary mechanism of aging embrittlement at temperatures between 280 and 400 degree C is the spinodal decomposition of the ferrite phase, and M23C6 carbide precipitation on the ferrite/austenite boundaries is the secondary mechanism for high-carbon CF-8 grade. 20 refs., 10 figs., 3 tabs

  18. Experimental and computational study on microstructural evolution in 2205 duplex stainless steel during high temperature aging

    Energy Technology Data Exchange (ETDEWEB)

    He Yanlin, E-mail: ylhe@staff.shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China); Zhu Naqiong; Lu Xiaogang; Li Lin [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)

    2010-12-15

    Research highlights: {yields} {sigma} is the first phase to appear at higher temperature because of rapid growth rate. {yields} Thermodynamic driving force for {chi} phase is always larger than that for {sigma} phase. {yields} The kinetic calculation on the migration of {gamma}/{alpha} interface during aging is present. - Abstract: 2205 duplex stainless steel (DSS) aged at temperatures between 700 deg. C and 1050 deg. C for different time intervals (5 min, 0.5 h, 1 h, 2 h) is studied. The evolution of secondary phases and the matrix with variation of aging time and temperature are measured by means of optical metallography (OM), SEM and EDS and BSE. The impact toughness, which reflects the effects of secondary phases, is also measured. It is shown that {sigma} is the dominant secondary phase in the matrix. The {sigma} phase precipitates at the austenite/ferrite boundaries or within ferritic grains, with the volume percent increasing with aging time and maximizing at 850 deg. C. Aided by Thermo-Calc software, the thermodynamic driving forces for {chi} phase and {sigma} phase are calculated. Although the driving force for {chi} phase is larger than that for {sigma} phase between 700 deg. C and 900 deg. C, {sigma} phase appears before {chi} phase because of its rapid growth rate at higher aging temperatures. According to the OM analysis and thermodynamic calculations, 2205 DSS at aging temperatures above 1000 deg. C is composed of ferrite and austenite, its volume fraction of ferrite increases with the increase of aging temperature. Moreover, the kinetic calculation on the migration of austenite/ferrite interface after different aging time is present. The thermodynamic and kinetic calculation results on the microstructural evolution of 2205 DSS are in good agreement with the experimental results.

  19. Experimental and computational study on microstructural evolution in 2205 duplex stainless steel during high temperature aging

    International Nuclear Information System (INIS)

    Research highlights: → σ is the first phase to appear at higher temperature because of rapid growth rate. → Thermodynamic driving force for χ phase is always larger than that for σ phase. → The kinetic calculation on the migration of γ/α interface during aging is present. - Abstract: 2205 duplex stainless steel (DSS) aged at temperatures between 700 deg. C and 1050 deg. C for different time intervals (5 min, 0.5 h, 1 h, 2 h) is studied. The evolution of secondary phases and the matrix with variation of aging time and temperature are measured by means of optical metallography (OM), SEM and EDS and BSE. The impact toughness, which reflects the effects of secondary phases, is also measured. It is shown that σ is the dominant secondary phase in the matrix. The σ phase precipitates at the austenite/ferrite boundaries or within ferritic grains, with the volume percent increasing with aging time and maximizing at 850 deg. C. Aided by Thermo-Calc software, the thermodynamic driving forces for χ phase and σ phase are calculated. Although the driving force for χ phase is larger than that for σ phase between 700 deg. C and 900 deg. C, σ phase appears before χ phase because of its rapid growth rate at higher aging temperatures. According to the OM analysis and thermodynamic calculations, 2205 DSS at aging temperatures above 1000 deg. C is composed of ferrite and austenite, its volume fraction of ferrite increases with the increase of aging temperature. Moreover, the kinetic calculation on the migration of austenite/ferrite interface after different aging time is present. The thermodynamic and kinetic calculation results on the microstructural evolution of 2205 DSS are in good agreement with the experimental results.

  20. A study on NDE method of thermal aging of cast duplex stainless steels

    International Nuclear Information System (INIS)

    To maintain the integrity of applications of the duplex stainless steels currently in service, a study was conducted to develop a method to nondestructively estimate their Charpy-impact energy at room temperature. It was found that hardness of the ferrite phase is a reliable indicator of the process of embrittlement during long-term heating of duplex stainless steels. However, further information on the ferrite phase and the austenite phase is required for the estimation of Charpy-impact energy. An equation composed of the hardness values of ferrite and austenite phases, the ferrite content and the average spacing of ferrite phase islands was presented as a method applicable to the nondestructive estimation of Charpy-impact energy at room temperature. (orig.)

  1. Kinetics and mechanism of thermal aging embrittlement of duplex stainless steels

    International Nuclear Information System (INIS)

    Microstructural characteristics of long-term-aged cast duplex stainless steel specimens from eight laboratory heats and an actual component from a commercial boiling water reactor have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle neutron scattering (SANS), and atom probe field ion microscopy (APFIM) techniques. Three precipitate phases, i.e., Cr-rich α' and the Ni- and Si-rich G phase, and γ2 austenite, have been identified in the ferrite matrix of the aged specimens. For CF-8 grade materials, M23C6 carbides were identified on the austenite-ferrite boundaries as well as in the ferrite matrix for aging at ≥ 4500C. It has been shown that Si, C, and Mo contents are important factors that influence the kinetics of the G-phase precipitation. However, TEM and APFIM analyses indicate that the embrittlement for ≤4000C aging is primarily associated with Fe and Cr segregation in ferrite by spinodal decomposition. For extended aging, e.g., 6 to 8 years at 350 to 4000C, large platelike α' formed by nucleation and growth from the structure produced by the spinodal decomposition. The Cr content appears to play an important role either to promote the platelike α' (high Cr content) or to suppress the α' in favor of γ2 precipitation (low Cr). Approximate TTT diagrams for the spinodal, α', G, γ2, and the in-ferrite M23C6 have been constructed for 250 to 4500C aging. Microstructural modifications associated with a 5500C reannealing and a subsequent toughness restoration are also discussed. It is shown that the toughness restoration is associated primarily with the dissolution of the Cr-rich region in ferrite

  2. Atomic scale observation of phase transformation in long term thermally aged duplex stainless steels

    International Nuclear Information System (INIS)

    Embrittlement study of duplex stainless steels is a very important in order to predict the lifetime of primary circuits of nuclear power plant. Ferrite steels aged over 20 years, on-site, in laboratory and at different temperatures was analyzed by tomographic probe atom to assess the trend of aging of these materials with very long times. A more prospective work was also carried out, the aim was to model the decomposition of ferrite from austenitic-ferritic steels. The simulation of the decomposition of these steels are very complex, we initiated preliminary work in modelling the Fe-Cr alloys, because the decomposition of Fe and Cr in these steels is the main cause of their fragility. To validate the parameters used in simulation, an experimental study of the decomposition of an alloy Fe-20% at. Cr aged at 500 C was performed. This experimental study has shown that a non-classical germination (NCG) is involved in this alloy. The performed simulations on the same alloy at the same temperature, did not reproduce the progressive enrichment of precipitated phase a' (characteristic of NCG). The study of steels, aged over 20 years, has confirmed that the steel aged in laboratory are representative to steel aged in site ( T ≤350 C). Moreover, it has been shown that the G-phase (intermetallic precipitation at the interface a/a' phases) does not influence the embrittlement of the ferrite and the difference of thermo-mechanical treatment is not determinant of the variance decomposition observed in these steels. (author)

  3. Effect of long-term thermal aging on the mechanical properties of casting duplex stainless steels

    International Nuclear Information System (INIS)

    Highlights: ► The micro-hardness change tendency of ferrite and austenite by aging was studied. ► Embrittlement behavior of Z3CN20-09M CDSSs by aging was investigated by SP test. ► The crack propagation energy Wt − Wiu slightly changes with the thermal aging time. ► Spinodal decomposition and spinodally coarsening take place in ferrite by aging. ► Z3CN20-09M CDSSs become embrittlement after long-term thermal aging treatment. - Abstract: Casting duplex stainless steels (CDSSs) used for pressurized water reactor (PWR) pipes are susceptible to thermal aging brittleness during long-term service at its working temperature from 288 °C to 327 °C. In order to investigate its thermal aging behavior, Z3CN20-09M CDSSs have been thermally aged at 400 °C up to 15,000 h. The micro-hardness of austenite and ferrite phases, conventional tensile properties, impact properties and SPT properties at different aging duration have been measured. The results show that the micro-hardness in ferrite gradually increases with increase of long thermal aging time, while the effect of the long aging time on the micro-hardness in austenite is negligible. The tensile strength and yield strength progressively and slightly increase with the long aging time, respectively. The impact property test confirms that there is the same change tendency as the percentage of elongation which decreases with the long aging time. The changes of SPT ultimate strength, SPT yield strength and SPT specific fracture energy by aging individually show that there is an almost same tendency as the tensile strength, the yield strength and the percentage of elongation with the thermal aging time. All above the mechanical properties changes of Z3CN20-09M CDSSs are associated with the changes of the dislocation configurations in austenite, the precipitation of G-phase on the dislocation line and in ferrite phase, the spinodal decomposition and the coarsening of the spinodally decomposed structure in ferrite

  4. A study of fracture of cast duplex stainless steels embrittled by aging at 400 C

    International Nuclear Information System (INIS)

    This work deals in particular with the fracture at 20 C of a cast duplex stainless steel ZCND19-10M containing 20% of ferrite and aged at 400 C during 700 h in order to obtain a fracture criterion of a volume element, in the framework of the local approach to fracture. With tensile tests on axisymmetric coped test pieces it is possible to study the effect of the stresses triaxiality on ductility. The fracture mechanisms are studied on metallographic sections and of fracture surface analyses. Cleavage cracks are initiated in ferrite and end in austenite. They grow up by blunting in austenite, and then form a macro-crack by coalescence. These cleavage cracks are clustered together. A crystallographic study shows that they appear in austenite grains which deform with simple slide, the incompatibility stress between the two phases being higher in this case. At a superior scale, the mechanical analysis of the crack growth conditions, shows that it is controlled by the plastic deformation. Moreover, cracks appear progressively when the deformation increases. A Gurson porous material behaviour model has been used to simulate the ductile fracture of this material. With random selection of grains strongly damaged (crack clusters) in coped specimens and of finite element calculations of these same specimens, it has been shown that ductility is controlled by cluster fracture and that its great dispersion can be correctly reproduced. (O.M.)

  5. Effect of Preaging Deformation on Aging Characteristics of 2507 Super Duplex Stainless Steel

    Science.gov (United States)

    Mishra, M. K.; Rao, A. G.; Sarkar, R.; Kashyap, B. P.; Prabhu, N.

    2016-02-01

    In the present study, precipitation of sigma (σ) phase was investigated over the temperature range of 700-850 °C in undeformed and deformed (60% cold rolling) samples of 2507 super duplex stainless steel. The fraction of sigma phase formed as a result of the transformation α → σ + γ2 increases with increasing time and temperature. The increase in sigma phase leads to increase in yield strength and decrease in ductility. Preaging deformation leads to accelerated precipitation of sigma phase. The activation energy for sigma phase precipitation in deformed sample is found to be lower than that in undeformed sample.

  6. Aging evaluation of duplex cast stainless steel using ball indentation test

    International Nuclear Information System (INIS)

    Cast Stainless Steel(CSS) is thermally aged by a long term exposure in the range of nuclear power plant operating temperature. The thermal aging is a cause of concern for the continued safe and reliable operation of CSS nuclear components. Therefore, an assessment of degradation in material properties of these components has been importantly considered. In this study the ball indentation tests were performed on four cast stainless steels aged at 400 .deg. C for 3600 hours, to investigate the applicability of ball indentation test to the assessment of aging degradation of cast stainless steels. Thus, the reliability of ball indentation test for aged CSS was analyzed by evaluating the scattering of data tested from each material and by comparing tensile properties obtained from ball indentation test and standard tensile test. Also, the tensile properties of aged CSS obtained from ball indentation test were compared with those predicted by the evaluation procedure developed on the basis of material database for aged CSS

  7. Influence of thermal aging on the reactivity of duplex stainless steel surfaces

    Science.gov (United States)

    Amadou, T.; Rhouma, A. Ben; Sidhom, H.; Braham, C.; Ledion, J.

    2000-08-01

    The annealing of large cast pieces in duplex stainless steel (SS) and the different heat cycles resulting from repairs involve significant structural changes characterized by carbide and intermetallic phase precipitation. This yields to lower local corrosion resistance in sea water due to changes in the local content of alloying elements. The precipitation of chromium carbide affects the resistance to the intergranular corrosion and the repassivation behavior. The eutectoidal decomposition of ferritic phase into regenerated austenite and in sigma phase ( α → γ r + σ) results in weakening the resistance to pit nucleation in synthetic sea water. In contrast, such precipitation will not have any significant effect when the treatment temperature is high enough to involve a rapid rehomogenization of depleted zones and ensure a self-healing.

  8. Quantification of Damage Progression in a Thermally Aged Duplex Stainless Steel

    OpenAIRE

    Hazarabedian A.; Marini B.

    2002-01-01

    Ferrite of austeno-ferritic stainless steels maintained for a long time at temperatures in the range of 270 °C to 400 °C is embrittled like the known 475 °C embrittlement of ferritic stainless steels. Deformation and damage micromechanisms of a material must be known in order to apply the "local approach to fracture" (LAF) methodology. In this work we test a previous model of damage nucleation and evolution, extending its validity to low temperature - long term aging. We have determined crack...

  9. Microstructural changes and fracture behavior of CF8M duplex stainless steels after long-term aging

    International Nuclear Information System (INIS)

    Microstructural changes and fracture behavior in cast CF8M duplex stainless steel after aging at 300-450 C for 300-10000 h have been investigated. Both, optical microscopical and transmission electron microscopical analyses, hardness and ferrite content measurements have been carried out in this study. Strengthening and aging phenomena of the ferrite phase have been identified by hardness measurements. Spinodal decomposition and heterogeneous precipitation of G-phase were found to be responsible for strengthening of the ferrite phase after aging with a temper parameter [P=log(t)+0.4343 Q/R(1/673.2-1/4)] (see Appendix A) in the range ca. 1.8-4.5. Three different fracture modes, dimples, cleavage and α/γ grain boundary separation, have been observed for Charpy V-notch and CT test specimens fractured at 20 C. (orig.)

  10. Evaluation of localized corrosion in duplex stainless steel aged at 850 deg. C with critical pitting temperature measurement

    Energy Technology Data Exchange (ETDEWEB)

    Deng Bo [Department of Material Science, Fudan University, Han Dan Road 220, Shanghai 200433 (China); Wang Zhiyu [Institute of Stainless Steel, Baosteel Co., LTD., Shanghai 201900 (China); Jiang Yiming; Wang Hao; Gao Juan [Department of Material Science, Fudan University, Han Dan Road 220, Shanghai 200433 (China); Li Jin [Department of Material Science, Fudan University, Han Dan Road 220, Shanghai 200433 (China)], E-mail: jinli@fudan.edu.cn

    2009-04-01

    Effect of aging at 850 deg. C on pitting corrosion of UNS S31803 duplex stainless steel was examined in chloride solution by potentiostatic critical pitting temperature (CPT) measurements. The quantitative metallography coupled with X-ray diffraction technique was employed to follow the microstructure evolution. Moreover, the initiation and propagation of pitting corrosion had been imaged in relation to microstructure variations using scanning electron microscopy (SEM). The results demonstrated that the corrosion behavior is strongly dependent on the microstructure, namely the presence of sigma phase. A deterioration of pitting corrosion resistance is found after aging 4 min, resulting in a drop in CPT. In particular, the metastable current transients during CPT test can clearly reflect the initiation of pitting process. Pitting nucleates preferentially in the austenite phase for the solution-annealed specimen, while the initiation of pitting corrosion takes place around sigma phase, in the newly formed secondary austenite for the aged specimen.

  11. Quantification of Damage Progression in a Thermally Aged Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    A. Hazarabedian

    2002-06-01

    Full Text Available Ferrite of austeno-ferritic stainless steels maintained for a long time at temperatures in the range of 270 °C to 400 °C is embrittled like the known 475 °C embrittlement of ferritic stainless steels. Deformation and damage micromechanisms of a material must be known in order to apply the "local approach to fracture" (LAF methodology. In this work we test a previous model of damage nucleation and evolution, extending its validity to low temperature - long term aging. We have determined cracking damage evolution by taking replicas of planar tensile specimens during uniaxial traction tests. Voronoï (Dirichlet tessellation quantitative metallography was applied to characterize and quantify non-uniform damaging. Clustering criteria allowed the determination of the size, density and internal damaging rate of damage clusters.

  12. Thermal ageing of cast duplex stainless steel primary components. Overview of the research program conducted by EDF

    Energy Technology Data Exchange (ETDEWEB)

    Massoud, J.P.; Jayet-Gendrot, S.; Le Delliou, P.; Semete, P. [Electricite de France (EDF), 77 - Moret sur Loing (France). Direction des Etudes et Recherches; Churier-Bossenec, H.; Ignaccolo, S. [Electricite de France (EDF), 69 - Villeurbanne (France). Direction de l`Equipment, SEPTEN; Bezdikian, G. [Electricite De France (EDF), 92 - Paris la Defense (France)

    1997-04-01

    The integrity assessment of cast duplex stainless steel components from the primary circuit of the PWR units relies on several research and development studies: the ageing surveillance programme on test ingots (cast at the same time as components) and on special products cast for studies has enabled us to develop prediction formulas of end-of-life toughness properties applicable to every component; tests on large-sized elbows containing analytical notches have shown their satisfactory behaviour even in severe situations (low toughness an high loadings); the development of a numerical tool (called ASCOUF) aimed to easily perform 3-D calculations; tests on mock-ups containing casting defects have shown that the resistance of shrinkage cavities to fatigue and to ductile tearing is much higher than the resistance of the envelope notches that are considered in mechanical analyses. The research program aiming at investigating the above issues is overviewed. (author) 8 refs.

  13. Study of phase transformation and mechanical properties evolution of duplex stainless steels after long term thermal ageing (>20 years)

    International Nuclear Information System (INIS)

    The ferrite of thermally aged CF3M duplex stainless steels has been studied at the atomic scale. Accelerated ageing of ingots has been performed at 350 deg. C in laboratory up to 200,000 h (>20 years). Spatial and chemical evolution of the microstructure of the ferrite has been characterised by 3D atom probe. In addition, micro-hardness has been performed on the same samples. The results obtained have been compared to the microstructural and mechanical characteristics of ferrite of the same ingots aged at 325 deg. C (close to service temperature) and to the ferrite of an elbow steel aged on-site. This work has shown that: (i) accelerated ageing at 350 deg. C anticipates the on-site ageing at 323 deg. C, (ii) the linear relationship found between micro-hardness measurements and the variation V (defined as the integral of the difference between the Cr frequency distribution of the aged sample and the corresponding binomial distribution characteristic of a random solution with the same concentration) is still valid after 200,000 h of ageing at 350 deg. C, (iii) the activation energy is the same for both spinodal decomposition and G-phase precipitation and finally (iv) the coarsening of G-phase particles has no influence on the relationship between ferrite micro-hardness and the V parameter.

  14. Probing the duplex stainless steel phases via magnetic force microscopy

    Science.gov (United States)

    Gheno, S. M.; Santos, F. S.; Kuri, S. E.

    2008-03-01

    Duplex stainless steels are austenitic-ferritic alloys used in many applications, thanks to their excellent mechanical properties and high corrosion resistance. In this work, chemical analyses, x-ray diffraction, and magnetic force microscopy (MFM) were employed to characterize the solution annealed and aged duplex stainless steel. The samples exhibited no changes in lattice parameters and the MFM technique proved successful in clearly imaging the magnetic domain structure of the ferrite phase.

  15. Investigation of selective corrosion resistance of aged lean duplex stainless steel 2101 by non-destructive electrochemical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Gao Juan; Jiang Yiming; Deng Bo [Department of Materials Science, Fudan University, Han Dan Road 220, Shanghai 200433 (China); Zhang Wei [Baosteel Research Institute, Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China); Zhong Cheng [Department of Materials Science, Fudan University, Han Dan Road 220, Shanghai 200433 (China); Li Jin [Department of Materials Science, Fudan University, Han Dan Road 220, Shanghai 200433 (China)], E-mail: jinli@fudan.edu.cn

    2009-10-01

    Lean duplex stainless steel 2101 (LDX2101) shows wide application potential due to its better corrosion performance and lower cost than traditional 304 austenite steel. This paper investigates the effects of thermal aging treatments at 700 deg. C for various aging times up to 100 h on the selective corrosion resistance of LDX2101 by two non-destructive electrochemical measurements: double-loop electrochemical potentiokinetic reactivation (DL-EPR) and electrochemical impedance spectroscopy (EIS). The evolution of microstructure was examined by optical microscopy, SEM microscopy and X-ray diffraction techniques (XRD). The results showed that the two applied electrochemical measurements agreed very well. Both methods were able to reveal the relationship between microstructure and selective corrosion resistance, which was related to the formation of chromium- and molybdenum-depleted zones around the precipitates, especially the {sigma} phase, during aging. Nevertheless, more information could be obtained using EIS methods, including the interfacial charge transfer reaction and the corrosion product adsorption process. The results suggest that the susceptibility of the aged alloy to selective corrosion is presumably codetermined by the formation of chromium- and molybdenum-depleted areas, as well as by the replenishment of them, in these areas from the bulk during aging.

  16. Investigation of selective corrosion resistance of aged lean duplex stainless steel 2101 by non-destructive electrochemical techniques

    International Nuclear Information System (INIS)

    Lean duplex stainless steel 2101 (LDX2101) shows wide application potential due to its better corrosion performance and lower cost than traditional 304 austenite steel. This paper investigates the effects of thermal aging treatments at 700 deg. C for various aging times up to 100 h on the selective corrosion resistance of LDX2101 by two non-destructive electrochemical measurements: double-loop electrochemical potentiokinetic reactivation (DL-EPR) and electrochemical impedance spectroscopy (EIS). The evolution of microstructure was examined by optical microscopy, SEM microscopy and X-ray diffraction techniques (XRD). The results showed that the two applied electrochemical measurements agreed very well. Both methods were able to reveal the relationship between microstructure and selective corrosion resistance, which was related to the formation of chromium- and molybdenum-depleted zones around the precipitates, especially the σ phase, during aging. Nevertheless, more information could be obtained using EIS methods, including the interfacial charge transfer reaction and the corrosion product adsorption process. The results suggest that the susceptibility of the aged alloy to selective corrosion is presumably codetermined by the formation of chromium- and molybdenum-depleted areas, as well as by the replenishment of them, in these areas from the bulk during aging.

  17. Atomic scale study of phase transformation in long term thermally aged duplex stainless steels: relation between microstructure and properties

    International Nuclear Information System (INIS)

    In this paper, the ferrite of thermally aged CF3M duplex stainless steels is studied at the atomic scale. Accelerated ageing was performed at 350 C. Ingots of CF3M steel were aged in laboratory at 350 C up to 200 000 h (> 20 years). Spatial and chemical evolution of the microstructure of ferrite, characterised by 3D atom probe and micro-hardness values were compared to microstructural and mechanical characteristics of ferrite of the same ingots aged at 325 C (service temperature) and to ferrite of actual steel aged on site. This work has shown that: -) Accelerating the ageing at 350 C anticipates the on-site ageing at 323 C; -) The linear relation between micro-hardness and variation V is still valid after 200.000 h of ageing at 350 C (this corresponds to an equivalent ageing time of 190 years at 323 C); -) Activation energy is the same for both spinodal decomposition and G-phase precipitation: a value of 243 kJ/mol has been obtained; -) Time evolution of the wave length of the α/α' decomposition still follows a law proportional to t0.16 after 200.000 h of ageing (no increase of the effective time exponent is observed); -) After 30.000 h of ageing, coarsening of G-phase particles starts, the equilibrium volume fraction of G-phase is estimated to 8.5% and no modification of the time evolution of the radius of precipitates is observed; -) G-phase particles have no direct influence on the evolution of the ferrite micro-hardness. This does not exclude indirect effect due to synergetic precipitation of G-phase which leads to the decrease of the amount of Ni in ferrite matrix. Later could slower kinetics and then explain the absence of increase in the time exponent. (authors)

  18. Kinetics and mechanism of thermal aging embrittlement of duplex stainless steels

    International Nuclear Information System (INIS)

    Microstructural characteristics of long-term-aged cast stainless steel specimens from six laboratory heats and an actual component from a commercial boiling water reactor have been investigated by transmission electron microscopy (TEM), small angle neutron scattering (SANS), and atom probe field ion microscopy (APFIM) techniques. Three precipitate phases, i.e., Cr-rich α', Ni- and Si-rich G phase, and γ/sub 2/ austenite, have been identified in the ferrite of the aged specimens. For CF-8 grade materials, M/sub 23/C/sub 6/ carbides were identified on the austenite-ferrite boundaries as well as in the ferrite after aging at ≥4500C. It has been shown that the Si, C, and Mo contents influence the kinetics of the G-phase precipitation. However, TEM and APFIM analyses show that the embrittlement during aging at ≤4000C is primarily associated with Fe and Cr segregation in ferrite by spinodal decomposition. Both C and Ni, available in the ferrite matrix, appear to accelerate the spinodal decomposition. For extended aging, e.g., 6-8 yr at 350-4000C, large platelike α' formed by nucleation and growth from the structure produced by the spinodal decomposition. The Cr content appears to play an important role either to promote the platelike α' (high Cr content) or to suppress the α' in favor of γ/sub 2/ precipitation (low Cr). Approximate TTT diagrams for the spinodal decomposition of ferrite and the nucleation and growth of α', G, γ/sub 2/, and M/sub 23/C/sub 6/ in the ferrite have been constructed for 250-4500C aging. Microstructural modifications associated with a 5500C reannealing and a subsequent toughness restoration are also discussed. The toughness restoration is associated primarily with the dissolution of the Cr-rich region in ferrite

  19. 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)

  20. Microstructural study of thermally aged duplex stainless steel deformation and fracture modes

    International Nuclear Information System (INIS)

    The aim of this work is to study the micro mechanisms of deformation and rupture of an austeno ferritic stainless steel (Z 3 CND 22-10 M) with 33 % of ferrite. It is studied after ageing 1 000 h at 400 deg. C and 8 000 h at 350 deg. C and compared to the 'as received' state. During ageing the ferritic phase undergoes microstructural evolutions which affects its properties. The two ageing treatments lead to roughly the same level of embrittlement. Microstructural characterisation shows that both phases percolate and exhibit orientation relationships close to Kurdjumov-Sachs ones. Mechanical properties of the steel were characterised for different ageing treatments at room temperature and at 320 deg. C. The interface is particularly strong and ensures the load transfer to ferrite even if this phase contains cleavage cracks. Moreover the interface does not oppose slip transmission which is instead controlled by localised glide in the ferritic phase. If activated slip systems of austenite are common with ferrite, slip transmission from austenite to ferrite indeed occurs through the=e interface. If they are not common, dislocations cross-slip back into the austenite. At 320 deg. C cross-slip occurs even far from the interface. Damage starts by nucleation in ferrite of cleavage cracks which propagate between austenite islands. Crack propagation is controlled by stretching of austenite ligaments. The material breaks by ductile tearing of austenite islands when the crack eventually percolates in the ferritic phase. The ductility of the material can be correctly describer using a simple model that takes into account the tearing-off the ductile-phase. (author)

  1. 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.

  2. Change in thermoelectric power of cast duplex stainless steel due to fluctuation of Cr concentration in ferrite phase caused by thermal aging

    International Nuclear Information System (INIS)

    Cast duplex stainless steel is frequently used in main coolant pipes of PWR (Pressurized water reactor) type nuclear power plants because of its excellent material strength, toughness and superior corrosion resistance. However, it is known that Cr concentration fluctuation in ferrite phase occurs due to thermal aging when this material is exposed to temperature over 300degC. As a result, the toughness decreases. In previous studies, it has been shown that thermoelectric power (TEP) is an effective parameter in non-destructive evaluation for thermal aging of cast duplex stainless steel. In this study, mechanisms of increase in TEP due to Cr concentration fluctuation caused by thermal aging were investigated. Referring to Cr concentration fluctuation in ferrite phase of thermal aged cast duplex stainless steel measured by 3D-atom prove, Fe-Cr-Ni alloys with different Cr concentrations, which represented local area Cr fluctuated, were prepared. Then, TEP, electrical conductivity and thermal conductivity of the alloys were measured, and the relationships between these values and Cr concentration were determined. Using the relationships and the Cr concentration fluctuations, TEP of thermal aged cast duplex steel were composed in the case when each Cr-fluctuated area acted in series connection and in parallel connection. Then, the changes in TEP due to thermal aging were simulated, and compared with that in experimentally measured TEP. As a result, recurrence curves of Cr concentration to TEP, electrical conductivity and thermal conductivity were downward convex parabolas. Therefore, it was found that, by means of creation of high and low Cr area in ferrite phase due to thermal aging, TEP, electrical conductivity and thermal conductivity of the whole material increased. When each Cr fluctuated area acted in parallel connections, increase in TEP due to thermal aging became larger and the change in the composed TEP came close to that in the experimentally measured TEP

  3. Microstructural Characterization and the Effect of Phase Transformations on Toughness of the UNS S31803 Duplex Stainless Steel Aged Treated at 850 °C

    Directory of Open Access Journals (Sweden)

    Igor Zucato

    2002-09-01

    Full Text Available Duplex stainless steels, with ferritic-austenitic microstructure, have excellent mechanical properties and corrosion resistance. However, when duplex stainless steels are exposed to temperatures between 600 and 1000 °C, some phase transformations can occur such as chromium nitrides precipitation, chromium carbides precipitation and the sigma phase formation. The formation of such compounds leads to loss in both corrosion resistance and fracture toughness. The negative effects of the formation of chromium nitrides, carbides and the sigma phase are due to the chromium depletion in the matrix. The phase transformations cited above occur initially at ferritic-austenitic interfaces and at the grain boundaries. The aim of this work is to identify and characterize the phase transformations, which occur when aging heat treatments are carried out at temperatures at which the kinetics is the fastest for the reactions mentioned. At first, the samples were annealed at 1100 °C for 40 min. The aging heat treatments were then carried out at 850 °C for 6, 40 e 600 min. Microstructural characterization was done by using optical microscopy with different etchings, in order to identify each phase formed in the duplex stainless steel during aging heat treatments. The toughness was also evaluated by using Charpy impact test. Impact tests show that loss of toughness was related to phase transformations.

  4. Effect of ageing on phase evolution and mechanical properties of a high tungsten super-duplex stainless steel

    International Nuclear Information System (INIS)

    Highlights: ► Secondary phases precipitate in a high tungsten SDSS aged between 700 and 900 °C. ► The volume fraction of the sigma phase increases as the holding time increases. ► The evolution of the sigma phase agrees with Johnson–Mehl–Avrami kinetic model. ► The secondary phases enhance the Young's modulus, hardness and strength. ► The ductility decreased significantly with increasing amount of sigma phase. - Abstract: The effect of ageing temperature and holding time on the precipitation of secondary phases and the mechanical properties of a 25Cr–6.7Ni–0.32N–3.0Mo–2.5W super duplex stainless steel is examined. The ageing temperature was varied from 600 to 900 °C and the holding time was varied from 1 to 240 min. Two types of Cr and Mo enriched intermetallic phases, sigma (σ) and chi (χ), were found to precipitate preferentially at the ferrite/austenite interface and within the ferrite grain. The precipitation of the χ-phase occurred preferentially before the σ-phase. The concentration of these secondary phases, which was quantified by a combination of microscopy and image analysis, increases with increasing ageing temperature and holding time, leading to significant reduction in the uniform strain and enhancement of the modulus, hardness and yield and tensile strengths. The measured concentration of the precipitated sigma phase is in agreement with the prediction by the Johnson–Mehl–Avrami kinetic model.

  5. Hot workability of duplex stainless steels

    OpenAIRE

    Martin, Guilhem

    2011-01-01

    The Duplex Stainless Steels (DSS) are defined as a family of stainless steels consisting of a two-phase microstructure involving δ-ferrite and γ-austenite. Exceptional combinations of strength and toughness together with good corrosion resistance under critical working conditions designate DSS a suitable alternative to conventional austenitic stainless steels. Unfortunately, the relatively poor hot workability of these alloys makes the industrial processing of flat products particularly criti...

  6. Duplex stainless steels for osteosynthesis devices.

    Science.gov (United States)

    Cigada, A; Rondelli, G; Vicentini, B; Giacomazzi, M; Roos, A

    1989-09-01

    The austenitic stainless steels used today for the manufacture of osteosynthesis devices are sensitive to crevice corrosion. In this study the corrosion properties of some duplex stainless steels were evaluated and compared to traditional austenitic stainless steels. According to our results the following ranking was established: 23Cr-4Ni less than AISI 316L less than ASTM F138 less than 22Cr-5Ni-3Mo less than 27Cr-31Ni-3.5Mo less than 25Cr-7Ni-4Mo-N. In particular the results showed that the high-performance 25Cr-7Ni-4Mo-N duplex stainless steel, with high molybdenum and nitrogen contents, can be considered not susceptible to crevice corrosion in the human body. The duplex stainless steels have also better mechanical properties at the same degree of cold working compared with austenitic stainless steels. Hence the 25Cr-7Ni-4Mo-N duplex stainless steel can be considered a convenient substitute of ASTM F138 for orthopedic and osteosynthesis devices. PMID:2777835

  7. Corrosion behavior of 2205 duplex stainless steel.

    Science.gov (United States)

    Platt, J A; Guzman, A; Zuccari, A; Thornburg, D W; Rhodes, B F; Oshida, Y; Moore, B K

    1997-07-01

    The corrosion of 2205 duplex stainless steel was compared with that of AISI type 316L stainless steel. The 2205 stainless steel is a potential orthodontic bracket material with low nickel content (4 to 6 wt%), whereas the 316L stainless steel (nickel content: 10 to 14 wt%) is a currently used bracket material. Both stainless steels were subjected to electrochemical and immersion (crevice) corrosion tests in 37 degrees C, 0.9 wt% sodium chloride solution. Electrochemical testing indicates that 2205 has a longer passivation range than 316L. The corrosion rate of 2205 was 0.416 MPY (milli-inch per year), whereas 316L exhibited 0.647 MPY. When 2205 was coupled to 316L with equal surface area ratio, the corrosion rate of 2205 reduced to 0.260 MPY, indicating that 316L stainless steel behaved like a sacrificial anode. When 316L is coupled with NiTi, TMA, or stainless steel arch wire and was subjected to the immersion corrosion test, it was found that 316L suffered from crevice corrosion. On the other hand, 2205 stainless steel did not show any localized crevice corrosion, although the surface of 2205 was covered with corrosion products, formed when coupled to NiTi and stainless steel wires. This study indicates that considering corrosion resistance, 2205 duplex stainless steel is an improved alternative to 316L for orthodontic bracket fabrication when used in conjunction with titanium, its alloys, or stainless steel arch wires. PMID:9228844

  8. Measuring secondary phases in duplex stainless steels

    Science.gov (United States)

    Calliari, I.; Brunelli, K.; Dabalà, M.; Ramous, E.

    2009-01-01

    The use of duplex stainless steels is limited by their susceptibility to the formation of dangerous intermetallic phases resulting in detrimental effects on impact toughness and corrosion resistance. This precipitation and the quantitative determinations of the phases have received considerable attention and different precipitation sequences (σ phase, χ phase, and carbides) have been suggested. This study investigates the phase transformation during continuous cooling and isothermal treatments in commercial duplex stainless steel grades and the effects on alloy properties, and compares the most common techniques of analysis.

  9. Fracture toughness properties of duplex stainless steels

    OpenAIRE

    Sieurin, Henrik

    2006-01-01

    Good toughness properties in base and weld material enable the use of duplex stainless steels (DSS) in critical applications. DSS offer high strength compared to common austenitic stainless steels. The high strength can be utilized to reduce the wall thickness and accordingly accomplish reduction of cost, welding time and transportation weight, contributing to ecological and energy savings. Although DSS have been used successfully in many applications the last decades, the full utilisation in...

  10. A Duplex Stainless Steel for Chloride Environments

    Science.gov (United States)

    Sridhar, N.; Kolts, J.; Flasche, L. H.

    1985-03-01

    This paper examines the effects of microstructural changes on the corrosion, stress corrosion cracking and corrosion fatigue resistance of a duplex stainless steel to chloride environments. The microstructural changes can be precipitation of phases such as sigma and carbides, or changes in the distribution of austenite and ferrite. The former can be important in hot forming operations while the latter is important in welding. The methods of minimizing these deleterious effects can sometimes be different from those used for austenitic stainless steel.

  11. Initial oxidation of duplex stainless steel 2205

    Energy Technology Data Exchange (ETDEWEB)

    Donik, E.; Kocijan, A.; Jenko, M. [Institute of metals and technology, Ljubljana (Slovenia)

    2009-07-01

    Due to superior mechanical and corrosion properties of duplex stainless steels which result in weight reduction of the constructions, thus contributing to the decreases in total costs and also due to the large and versatile usage of the alloy, duplex stainless steel is gradually displacing stainless steels of the AISI 300 series. Pickling of duplex stainless steel has proven to be much more difficult than that of standard austenitic grade (AISI 300 series). There is no complete agreement in the literature on scale (high temperature oxidation) dissolution mechanism in neutral pickling solutions. During annealing, duplex stainless steel is heated in annealing furnace up to 1050 C and is kept at this temperature for some time to soften the metal in order to release the work hardening induced by hot and cold rolling. The elimination of surface defects by forming the oxide scale is required to improve the corrosion resistance. Three different techniques were used to produce thin oxide layers on polished and sputter cleaned duplex stainless steel samples. They were exposed to 10{sup -5} mb pure oxygen inside the vacuum chamber, exposed to ambient conditions for 24 hours and plasma oxidized. Oxide layers thus produced were analysed using XPS depth profiling for determination of the oxide layer's composition with depth. It was found that all techniques produce oxide layer with different traces of metallic components and with chromium oxide maximum concentration shifted towards the oxide layer - bulk metal interface. Depletion of Cr in bulk immediately below the interface was also observed. Simplified ARXPS procedure was used to corroborate thickness estimates for thinnest oxide layers. (authors)

  12. Initial oxidation of duplex stainless steel 2205

    International Nuclear Information System (INIS)

    Due to superior mechanical and corrosion properties of duplex stainless steels which result in weight reduction of the constructions, thus contributing to the decreases in total costs and also due to the large and versatile usage of the alloy, duplex stainless steel is gradually displacing stainless steels of the AISI 300 series. Pickling of duplex stainless steel has proven to be much more difficult than that of standard austenitic grade (AISI 300 series). There is no complete agreement in the literature on scale (high temperature oxidation) dissolution mechanism in neutral pickling solutions. During annealing, duplex stainless steel is heated in annealing furnace up to 1050 C and is kept at this temperature for some time to soften the metal in order to release the work hardening induced by hot and cold rolling. The elimination of surface defects by forming the oxide scale is required to improve the corrosion resistance. Three different techniques were used to produce thin oxide layers on polished and sputter cleaned duplex stainless steel samples. They were exposed to 10-5 mb pure oxygen inside the vacuum chamber, exposed to ambient conditions for 24 hours and plasma oxidized. Oxide layers thus produced were analysed using XPS depth profiling for determination of the oxide layer's composition with depth. It was found that all techniques produce oxide layer with different traces of metallic components and with chromium oxide maximum concentration shifted towards the oxide layer - bulk metal interface. Depletion of Cr in bulk immediately below the interface was also observed. Simplified ARXPS procedure was used to corroborate thickness estimates for thinnest oxide layers. (authors)

  13. Influence of thermal aging on primary water stress corrosion cracking of cast duplex stainless steel (second report). Consideration on fractography after slow strain rate technique

    International Nuclear Information System (INIS)

    In order to evaluate the stress corrosion cracking (SCC) susceptibility of cast duplex stainless steel which is used for the main coolant pipe of pressurized water reactors (PWRs), the slow strain rate technique (SSRT) and the constant load test (CLT) of the materials were performed in simulated primary water at 360degC. The cast duplex stainless steel contains ferrite phase with ranging from 8 to 23% and its mechanical properties are affected by long time thermal aging. Therefore, we paid attention to the influence of its ferrite content and thermal aging on the SCC susceptibility of this unaged and aged stainless steel and prepared three kinds of specimen with different ferrite contents (23%, 15% and 8%). The brittle fracture of the unaged specimens after SSRT mainly consists of quasi-cleavage fracture in austenitic phase. After aging, it changes to a mixture of quasi-cleavage fracture in both austenitic and ferritic phases. Microcracks were observed on the unaged specimen surfaces and aged ones for 10,000 hours at 400degC after about 10,000 hours of the CLT under the load condition of 1.2∼2.0 times of yield strength. The crack initiation sites of CLT specimens are similar to SSRT fracture surfaces. The SCC susceptibility of this 23% ferrite material increases with aging time at 400degC. The SCC susceptibility of 15% and 23% ferrite materials are higher than that of 8% ferrite material with aging condition for 30,000h at 400degC. (author)

  14. Microstructural Characterization and the Effect of Phase Transformations on Toughness of the UNS S31803 Duplex Stainless Steel Aged Treated at 850 °C

    OpenAIRE

    Igor Zucato; Margarete C. Moreira; Izabel F. Machado; Susana M. Giampietri Lebrão

    2002-01-01

    Duplex stainless steels, with ferritic-austenitic microstructure, have excellent mechanical properties and corrosion resistance. However, when duplex stainless steels are exposed to temperatures between 600 and 1000 °C, some phase transformations can occur such as chromium nitrides precipitation, chromium carbides precipitation and the sigma phase formation. The formation of such compounds leads to loss in both corrosion resistance and fracture toughness. The negative effects of the formation...

  15. G-phase precipitation in duplex stainless steels after long-term thermal aging: A high-resolution transmission electron microscopy study

    Science.gov (United States)

    Li, Shilei; Wang, Yanli; Wang, Xitao; Xue, Fei

    2014-09-01

    High-resolution transmission electron microscopy was used to investigate the G-phase precipitation behavior in duplex stainless steels long-term thermally aged at 300-450 °C. Rising temperature can accelerate thermal aging kinetics and shorten the incubation period of G-phase. G-phase adopts a cube-on-cube orientation relationship with the ferrite matrix. Transformation from ferritic cluster to G-phase can be accomplished through smaller atomic position readjustments. After aging at 400 °C for 20,000 h, G-phase grows up to 4-5 nm and the interface between G-phase and the ferrite matrix still maintains semi-coherent. Disarrangement of crystal planes causes misfit dislocations and strain fields around G-phase.

  16. G-phase precipitation in duplex stainless steels after long-term thermal aging: A high-resolution transmission electron microscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shilei [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Yanli [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Xitao, E-mail: xtwang@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083 (China); Xue, Fei [China Guangdong Nuclear Power Group, Shenzhen 518028 (China)

    2014-09-15

    High-resolution transmission electron microscopy was used to investigate the G-phase precipitation behavior in duplex stainless steels long-term thermally aged at 300–450 °C. Rising temperature can accelerate thermal aging kinetics and shorten the incubation period of G-phase. G-phase adopts a cube-on-cube orientation relationship with the ferrite matrix. Transformation from ferritic cluster to G-phase can be accomplished through smaller atomic position readjustments. After aging at 400 °C for 20,000 h, G-phase grows up to 4–5 nm and the interface between G-phase and the ferrite matrix still maintains semi-coherent. Disarrangement of crystal planes causes misfit dislocations and strain fields around G-phase.

  17. Cyclic deformation of duplex stainless steels

    OpenAIRE

    Mateo García, Antonio Manuel; Gironés, Ana

    2011-01-01

    Duplex stainless steels configure a family of metallic alloys that combined elevated mechanical properties with improved corrosion resistance when compared to standard austenitic grades. This excellent combination of properties leads to their use under many different applications, particularly in the fields of chemical, petrochemical, pulp and paper industries. Moreover, these applications usually involve cyclic loading, and consequently the study of fatigue properties has a great significanc...

  18. Properties of thermally embrittled cast duplex stainless steel

    International Nuclear Information System (INIS)

    The authors describe cast duplex stainless steel, grade CF-3, used in nuclear pump applications, thermally aged at 4000C to induce an embrittling phase transformation, thereby simulating long term exposures at 2800C (5360F). The mechanical properties of as-cast material and the thermally aged materials were subsequently investigated. Fracture roughness, Charpy V-Notch (CVN), tensile, precracked CVN, nil-ductility transition temperature, and hardness tests were performed on these materials. Tests were run as a function of temperature and loading rate. The as-cast structure of this duplex stainless steel is extremely tough, but thermal aging causes a decrease in upper shelf fracture toughness parameters and absorbed Charpy energy, and a marked increase in transition temperature. However, even the most severely aged material (14406 hr/4000C) appears to possess excellent upper shelf values, although the transition temperature shift is to a relatively high temperature. A conclusion is that cast duplex stainless steel is sufficiently tough, even in the aged condition, to resist crack initiation and propagation under expected nuclear pump service conditions

  19. Crack propagation during fatigue in cast duplex stainless steels: influence of the microstructure, of the aging and of the test temperature

    International Nuclear Information System (INIS)

    Duplex stainless steels are used as cast components in nuclear power plants. At the service temperature of about 320 C, the ferrite phase is thermally aged and embrittled. This induces a significant decrease in fracture properties of these materials. The aim of this work consists in studying Fatigue Crack Growth Rates (FCGR) and Fatigue Crack Growth Mechanisms (FCGM) as a function of thermal ageing and test temperature (20 C/320 C). Two cast duplex stainless steels (30% ferrite) are tested. In order to better understand the influence of the crystallographic orientation of the phases on the FCGM, the solidification structure of the material is studied by Electron Back-Scatter Diffraction (EBSD) and by Unidirectional Solidification Quenching. Fatigue crack growth tests are also performed in equiaxed and basaltic structures. Microstructure, fatigue crack growth mechanical properties and mechanisms are thus studied in relation to each other. In the studied range of delta K, the crack propagates without any preferential path by successive ruptures of phase laths. The macroscopic crack propagation plane, as determined by EBSD, depends on the crystallographic orientation of the ferrite grain. So, according to the solidification structure, secondary cracks can appear, which in turn influences the FCGR. Fatigue crack closure, which has to be determined to estimate the intrinsic FCGR, decreases with increasing ageing. This can be explained by a decrease in the kinematic cyclic hardening. The Paris exponent as determined from intrinsic FCGR increases with ageing. Intrinsic FCGR can then be separated in two ranges: one with lower FCGR in aged materials than in un-aged and one with the reversed tendency. (author)

  20. Welding of duplex and super-duplex stainless steels

    International Nuclear Information System (INIS)

    After a recall of the commercial designation of duplex or super-duplex steels (22-27% Cr, 4-8% Ni, 0.1-0.3% N with or without Mo (1.5-4%)) and of some metallurgical properties (phase diagrams, microstructure, ferrite determination, heat treatment and aging), welding technologies are synthetically presented (advantages-disadvantages of each process, metals filler, parameters of the welding processes, heat treatments after welding, cleaning, passivation, properties (mechanical, corrosion resistance) of the welded pieces). (A.B.). 28 refs. 5 figs., 15 tabs., 1 annexe

  1. Development of oxide dispersion strengthened 2205 duplex stainless steel composite

    OpenAIRE

    Oladayo OLANIRAN; Peter Apata OLUBAMBI; Benjamin Omotayo ADEWUYI; Joseph Ajibade OMOTOYINBO; Ayodeji Ebenezar AFOLABI; Davies FOLORUNSO; Adekunle ADEGBOLA; Emanuel IGBAFEN

    2015-01-01

    Composites of duplex stainless steel were produced by oxide dispersion strengthening with comparatively improved mechanical properties by hot press sintering of partially stabilized Zirconia (PSZ, 3% yttria, mole fraction) dispersion in 2205 duplex stainless steels. Ceramic oxide was added as reinforcement, while chromium (Cr) and Nickel (Ni) were incorporated to maintain the austenitic/ferritic phase balance of the duplex stainless steel. The powders and sintered were characterized in detail...

  2. M23C6 carbides and Cr2N nitrides in aged duplex stainless steel: A SEM, TEM and FIB tomography investigation.

    Science.gov (United States)

    Maetz, J-Y; Douillard, T; Cazottes, S; Verdu, C; Kléber, X

    2016-05-01

    The precipitation evolution during ageing of a 2101 lean duplex stainless steel was investigated, revealing that the precipitate type and morphology depends on the nature of the grain boundary. Triangular M23C6 carbides precipitate only at γ/δ interfaces and rod-like Cr2N nitrides precipitate at both γ/δ and δ/δ interfaces. After 15min of ageing, the M23C6 size no longer evolves, whereas that of the Cr2N continues to evolve. For Cr2N, the morphology is maintained at γ/δ interfaces, whereas percolation occurs to form a continuous layer at δ/δ interfaces. By combining 2D and 3D characterisation at the nanoscale using transmission electron microscopy (TEM) and focused ion beam (FIB) tomography, a complete description of the precipitation evolution was obtained, including the composition, crystallographic structure, orientation relationship with the matrix phases, location, morphology, size and volume fraction. PMID:26925831

  3. Corrosion behavior of sensitized duplex stainless steel.

    Science.gov (United States)

    Torres, F J; Panyayong, W; Rogers, W; Velasquez-Plata, D; Oshida, Y; Moore, B K

    1998-01-01

    The present work investigates the corrosion behavior of 2205 duplex stainless steel in 0.9% NaCl solution after various heat-treatments, and compares it to that of 316L austenitic stainless steel. Both stainless steels were heat-treated at 500, 650, and 800 degrees C in air for 1 h, followed by furnace cooling. Each heat-treated sample was examined for their microstructures and Vickers micro-hardness, and subjected to the X-ray diffraction for the phase identification. Using potentiostatic polarization method, each heat-treated sample was corrosion-tested in 37 degrees C 0.9% NaCl solution to estimate its corrosion rate. It was found that simulated sensitization showed an adverse influence on both steels, indicating that corrosion rates increased by increasing the sensitization temperatures. PMID:9713683

  4. Crack bridging in stress corrosion cracking of duplex stainless steels

    International Nuclear Information System (INIS)

    Wedge open loaded (WOL) specimens of age hardened Zeron 100 duplex stainless steel were tested in 3.5 wt % NaCl solution with cathodic polarizes applied at-900m V/SCE to investigate stress corrosion cracking mechanism in duplex stainless steel. The interaction between microstructure and mechanism of stress corrosion cracking was studied. Fracture mechanism was studied by using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The material was found cracked by ferrite cleavage, austenite tearing and austenite dissolution by environment. The ferrite cleavage took place along [100] planes and [112] twin habit planes. The austenite grains appear to act as crack bridging and crack arrester and failed by tearing and stress corrosion cracking. (author)

  5. Examination of applicability of thermoelectric power measurement for thermal aging evaluation of cast duplex stainless steel to real components in nuclear power plants

    International Nuclear Information System (INIS)

    It is known the mechanical properties of cast duplex stainless steel, which is used for main coolant pipes of pressurized water reactor type nuclear power plants, change due to thermal aging. Non-destructive evaluation method for thermal aging using thermoelectric power measurement has been studied in INSS. And it has been found that there was some relation between mechanical properties and thermoelectric power in the case of accelerated aging sample and change in thermoelectric power was caused by change in microstructure due to thermal aging. In this study, n-site measurement of thermoelectric power of a main coolant pipe with the measurement device which has been used in a laboratory was carried out. As a result, thermoelectric power of the main coolant pipe was almost measured within the range from -2.2 to -2μ V/degC, and that was corresponding to the relation of accelerated aging samples between thermoelectric power and the product of ferrite content and aging parameter considering the standard error. Moreover, applying the measured thermoelectric power to the relation of accelerated aging samples between thermoelectric power and impact value, change in the impact value of the pipe seemed to be corresponding to about 40% of the maximum change assumed by thermal aging. (author)

  6. Fatigue properties of duplex stainless steel

    OpenAIRE

    Turrel, Benjamin; Luna Garcia, Jordi; Andraschko, Stephan

    2009-01-01

    PFC presentat a Oslo University College The aim of the project is to study fatigue properties of duplex stainless steel used for a bridge. The samples had to be tested and the results have to be compared with the theory, studied before. Six specimens have been broken by tensile fatigue testing machine in order to get more knowledge about the lifetime and the behavior under dynamic stress and not only for welded parts. Out of this new knowledge a new fatigue curve for this ma...

  7. Hydrogen Embrittlement Susceptibility of Super Duplex Stainless Steels

    OpenAIRE

    Alsarraf, Jalal

    2010-01-01

    This thesis describes the metallurgical and environmental factors that influence hydrogen embrittlement of super duplex stainless steels and presents a model to predict the rate at which embrittlement occurs. Super duplex stainless steel has an austenite and ferrite microstructure with an average fraction of each phase of approximately 50%. An investigation was carried out on the metallurgical and environmental factors that influence hydrogen embrittlement of super duplex st...

  8. Development of a lean duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Liljas, M.; Johansson, P.; Liu Hui-Ping; Olsson, C.O.A. [Avesta Research Centre, Avesta (Sweden). Outokumpu Stainless

    2008-06-15

    The classic series of duplex stainless steels shows very high corrosion resistance and can be used for very demanding applications. A new lean duplex steel, LDX 2101 {sup registered} (EN 1.4162, UNS S32101), has been developed with corrosion resistance on a par with standard austenitic grades. Application areas include: structural components, chemical industry, tanks and containers. The steel was designed to have equal amounts of ferrite and austenite in annealed condition and with an austenite that is stable against strain-induced martensite. Thanks to its high nitrogen content, the steel has a fast austenite reformation when subjected to thermal cycling, e.g. welding. Unlike conventional duplex grades, the formation of intermetallic phase is very sluggish, although precipitation of nitrides and carbides has a certain impact on material properties after exposure in the temperature range 600 to 800 C. The precipitation behaviour after different isothermal treatments is described and its influence on different product properties is shown. A good agreement was found between impact toughness and corrosion resistance for a wide range of thermal treatments. (orig.)

  9. THE ATOM PROBE ANALYSIS OF A CAST DUPLEX STAINLESS STEEL

    OpenAIRE

    Godfrey, T.; G. Smith

    1986-01-01

    Atom probe analysis is reported of a low Mo CF8 duplex stainless steel aged for 105,000h at 280°C, 3,000h or 70,000h at 300°C, or 3,000h at 400°C. Definite evidence for a spinodal reaction in the α phase has been found at all the temperatures studied. This reaction process is most regular and pronounced in the material aged at 400°C but is detectable after the other heat treatments. No evidence of G-phase precipitation is apparent from the FIM micrographs, but statistical analysis of the atom...

  10. On phase equilibria in duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Wessman, S. [Swerea KIMAB AB, Stockholm (Sweden); Pettersson, R. [Outokumpu Stainless AB, Avesta Research Centre, Avesta (Sweden); Hertzman, S. [Outokumpu Stainless Research Foundation, Stockholm (Sweden)

    2010-05-15

    The equilibrium conditions of four duplex stainless steels; Fe-23Cr-4.5Ni-0.1N, Fe-22Cr-5.5Ni-3Mo-0.17N, Fe-25Cr-7Ni-4Mo-0.27N and Fe-25Cr-7Ni-4Mo-1W-1.5Cu-0.27N were studied in the temperature region from 700 to 1000 C. Phase compositions were determined with SEM EDS and the phase fractions using image analysis on backscattered SEM images. The results showed that below 1000 C the steels develop an inverse duplex structure with austenite and sigma phase, of which the former is the matrix phase. With decreasing temperature, the microstructure will be more and more complex and finely dispersed. The ferrite is, for the higher alloyed steels, only stable above 1000 C and at lower temperatures disappears in favour of intermetallic phases. The major intermetallic phase is sigma phase with small amounts of chi phase, the latter primarily in high Mo and W grades. Nitrides, not a focus in this investigation, were present as rounded particles and acicular precipitates at lower temperatures. The results were compared to theoretical predictions using the TCFE5 and TCFE6 databases. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Kinetics of G-phase precipitation and spinodal decomposition in very long aged ferrite of a Mo-free duplex stainless steel

    Science.gov (United States)

    Pareige, C.; Emo, J.; Saillet, S.; Domain, C.; Pareige, P.

    2015-10-01

    Evolution of spinodal decomposition and G-phase precipitation in ferrite of a thermally aged Mo-free duplex stainless steel was studied by Atom Probe Tomography (APT). Kinetics was compared to kinetics observed in ferrite of some Mo-bearing steels aged in similar conditions. This paper shows that formation of the G-phase particles proceeds via at least a two-step mechanism: enrichment of α/α‧ inter-domains by G-former elements followed by formation of G-phase particles. As expected, G-phase precipitation is much less intense in the Mo-free steel than in Mo-bearing steels. The kinetic synergy observed in Mo-bearing steels between spinodal decomposition and G-phase precipitation is shown to also exist in Mo-free steel. Spinodal decomposition is less developed in the ferrite of the Mo-free steel investigated than in Mo-bearing steels: both the amplitude of the decomposition and the effective time exponent of the wavelength (0.06 versus 0.16) are much lower for the Mo-free steel. Neither the temperature of homogenisation nor quench effects or Ni and Mo contents could successfully explain the low time exponent of the spinodal decomposition observed in the Mo-free steel. The diffusion mechanisms could be at the origin of the different time exponents (diffusion along α/α‧ interfaces or diffusion of small clusters).

  12. Development of oxide dispersion strengthened 2205 duplex stainless steel composite

    Directory of Open Access Journals (Sweden)

    Oladayo OLANIRAN

    2015-05-01

    Full Text Available Composites of duplex stainless steel were produced by oxide dispersion strengthening with comparatively improved mechanical properties by hot press sintering of partially stabilized Zirconia (PSZ, 3% yttria, mole fraction dispersion in 2205 duplex stainless steels. Ceramic oxide was added as reinforcement, while chromium (Cr and Nickel (Ni were incorporated to maintain the austenitic/ferritic phase balance of the duplex stainless steel. The powders and sintered were characterized in detail using scanning electron microscopy (SEM and X-ray diffraction (XRD. The microstructural evolution and phase formation during oxide dispersion strengthening of duplex stainless steel composites were investigated. The influence of composition variation of the reinforcements on the microstructural and corrosion behaviour in simulated mine water of the composites were investigated. In this manuscript, it was established that composition has great influence on the structure/properties relationship of the composites developed.

  13. Estimation of revealing methods of microstructure in duplex stainless steels

    International Nuclear Information System (INIS)

    Revealing of microstructure in duplex stainless steels by conventional chemical or electrochemical etching methods is relatively difficult as opposed to carbon steels. There are a many etching methods for duplex stainless steels, however electrolytic etching is really the best way to go. Electrochemical etching assures very good distinction of ferrite, austenite and secondary phases also etching of grain boundaries and twins, simultaneously warranting repeatability of process' circumstances. However, literature data do not deliver enough explicit parameters and conditions of electrolytic etching process, what in consequence can lead to indirect phenomenon during the process, such as pitting or etching twins. In frames of this work we have tested different methods of electrolytic etching of duplex stainless steel 1.4462-X2CrNiMoN 22.5.3 according to EURONORM (UNS S3108). This article has in view discussing of controversial matter of argument relating to revealing microstructure in duplex stainless steels on the ground of conducted investigations. (author)

  14. Corrosion resistance properties of sintered duplex stainless steel

    OpenAIRE

    L.A. Dobrzański; Z. Brytan; M. Actis Grande; M. Rosso

    2006-01-01

    Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the ...

  15. EXPERIMENTAL RESEARCH OF THE DUPLEX STAINLESS STEEL WELDS IN SHIPBUILDING

    OpenAIRE

    Juraga, Ivan; Stojanović, Ivan; Ljubenkov, Boris

    2014-01-01

    Duplex stainless steel is used in shipbuilding increasingly because of its good mechanical properties and marked corrosion resistance. This steel has a two phase structure (austenite-ferrite) which is sensitive on heat input during welding because of the possible ferritisation appearance, that is, increase in ferrite content in the area of heat effected zone (HAZ) which can lead to loss of mechanical and corrosion properties. Work with duplex stainless steel requires special attention in ever...

  16. Properties of duplex stainless steels made by powder metallurgy

    OpenAIRE

    M. Rosso; M. Actis Grande; Z. Brytan; L.A. Dobrzański

    2007-01-01

    Purpose: of this paper was to examine the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been sintered in a vacuu...

  17. Effects of low temperature aging on the mechanical properties and corrosion resistance of duplex and lean duplex stainless steels UNS S32205 and UNS S32304 Efeitos de envelhecimentos em baixas temperaturas nas propriedades mecânicas e resistência à corrosão dos aços duplex e lean duplex UNS S32205 e UNS S32304

    OpenAIRE

    Francis Gabriel Wasserman; Sergio Souto Maior Tavares; Juan Manuel Pardal; Fernando Benedicto Mainier; Ricardo Augusto Faria; Cristiana dos Santos Nunes

    2013-01-01

    Duplex stainless steels (DSS) with austenite-ferrite microstructure are high strength and corrosion resistant steels frequently used as pipes and accessories in chemical/petrochemical on/and off-shore industries. Low temperature heat treatments (400-475ºC) may increase the hardness and wear resistance of duplex steels, due to a spinodal decomposition reaction of the ferrite, whose small particles α' precipitate in the matrix. In this work, several heat treatments at 400ºC and 475ºC with ...

  18. EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

    OpenAIRE

    Prabhu Paulraj; Rajnish Garg

    2015-01-01

    Duplex Stainless Steels (DSS) and Super Duplex Stainless Steel (SDSS) have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic pha...

  19. Phase Transformations in Cast Duplex Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Yoon-Jun Kim

    2004-12-19

    Duplex stainless steels (DSS) constitute both ferrite and austenite as a matrix. Such a microstructure confers a high corrosion resistance with favorable mechanical properties. However, intermetallic phases such as {sigma} and {chi} can also form during casting or high-temperature processing and can degrade the properties of the DSS. This research was initiated to develop time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams of two types of cast duplex stainless steels, CD3MN (Fe-22Cr-5Ni-Mo-N) and CD3MWCuN (Fe-25Cr-7Ni-Mo-W-Cu-N), in order to understand the time and temperature ranges for intermetallic phase formation. The alloys were heat treated isothermally or under controlled cooling conditions and then characterized using conventional metallographic methods that included tint etching, and also using electron microscopy (SEM, TEM) and wavelength dispersive spectroscopy (WDS). The kinetics of intermetallic-phase ({sigma} + {chi}) formation were analyzed using the Johnson-Mehl-Avrami (MA) equation in the case of isothermal transformations and a modified form of this equation in the case of continuous cooling transformations. The rate of intermetallic-phase formation was found to be much faster in CD3MWCuN than CD3MN due mainly to differences in the major alloying contents such as Cr, Ni and Mo. To examine in more detail the effects of these elements of the phase stabilities; a series of eight steel castings was designed with the Cr, Ni and Mo contents systematically varied with respect to the nominal composition of CD3MN. The effects of varying the contents of alloying additions on the formation of intermetallic phases were also studied computationally using the commercial thermodynamic software package, Thermo-Calc. In general, {sigma} was stabilized with increasing Cr addition and {chi} by increasing Mo addition. However, a delicate balance among Ni and other minor elements such as N and Si also exists. Phase equilibria in

  20. Phase transformations in cast duplex stainless steels

    Science.gov (United States)

    Kim, Yoon-Jun

    Duplex stainless steels (DSS) constitute both ferrite and austenite as a matrix. Such a microstructure confers a high corrosion resistance with favorable mechanical properties. However, intermetallic phases such as sigma (sigma) and chi (chi) can also form during casting or high-temperature processing and can degrade the properties of the DSS. This research was initiated to develop time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams of two types of cast duplex stainless steels, CD3MN (Fe-22Cr-5Ni-Mo-N) and CD3MWCuN (Fe-25Cr-7Ni-Mo-W-Cu-N), in order to understand the time and temperature ranges for intermetallic phase formation. The alloys were heat treated isothermally or under controlled cooling conditions and then characterized using conventional metallographic methods that included tint etching, and also using electron microscopy (SEM, TEM) and wavelength dispersive spectroscopy (WDS). The kinetics of intermetallic-phase (sigma + chi) formation were analyzed using the Johnson-Mehl-Avrami (JMA) equation in the case of isothermal transformations and a modified form of this equation in the case of continuous cooling transformations. The rate of intermetallic-phase formation was found to be much faster in CD3MWCuN than CD3MN due mainly to differences in the major alloying contents such as Cr, Ni and Mo. To examine in more detail the effects of these elements of the phase stabilities, a series of eight steel castings was designed with the Cr, Ni and Mo contents systematically varied with respect to the nominal composition of CD3MN. The effects of varying the contents of alloying additions on the formation of intermetallic phases were also studied computationally using the commercial thermodynamic software package, Thermo-Calc. In general, a was stabilized with increasing Cr addition and chi by increasing Mo addition. However, a delicate balance among Ni and other minor elements such as N and Si also exists. Phase equilibria in

  1. In vivo behavior of a high performance duplex stainless steel.

    Science.gov (United States)

    Cigada, A; De Santis, G; Gatti, A M; Roos, A; Zaffe, D

    1993-01-01

    An in vivo investigation of a new high molybdenum and nitrogen duplex stainless steel (25Cr--7Ni--4Mo--0.3N) has been performed. Cylindrical pins and specially developed devices, to test in static conditions the in vivo localized corrosion resistance, made of this new duplex steel and of a common austenitic stainless steel were implanted in rabbit's femurs for 6 and 12 months. After sacrifice, SEM observations and EDS microanalyses to detect metallic ion release were carried out on the femur sections surrounding the pins. Morphologic observations with stereoscope and SEM were performed on the metallic surfaces of the special devices in order to detect the presence of localized corrosion. Both ion release and localized corrosion were observed for the specimens made of austenitic stainless steel, but not for those made of 25Cr--7Ni--4Mo--0.3N duplex stainless steel. PMID:10148344

  2. Effect of microstructure on impact toughness of duplex and superduplex stainless steels

    Directory of Open Access Journals (Sweden)

    S. Topolska

    2009-10-01

    Full Text Available Purpose: of this paper is to study the effect of heat treatments and resulting changes in microstructure on mechanical properties, mainly impact toughness, of commercial 2205 duplex stainless steel and higher alloy superduplex 2507 grade.Design/methodology/approach: Both steels were submitted to ageing treatments in the temperature range of 500-900 °C with exposure time periods 6 minutes, 1 hour and 10 hours. Light microscope examinations, hardness measurements and impact toughness tests were performed in order to reveal microstructure and changes in mechanical properties.Findings: Obtained results confirm that high temperature service of duplex stainless steels should be avoided. Precipitations of secondary phases (mainly σ phase strongly deteriorate mechanical properties of steels but some amounts of these phases could be acceptable in the microstructure depending upon the application of the steel.Research limitations/implications: Presence of secondary phases in duplex stainless steel microstructure can be very harmful for its corrosion resistance. This phenomenon is not considered in this study.Practical implications: The accidents during exploitation and errors in processing of duplex stainless steels can result in undesired temperature growth over 500°C. Such events brings question whether the steel can be still exploited or not. The aim of present study is to reveal the effect of thermal cycles on structural changes and mechanical properties of duplex stainless steel and establish the highest acceptable time-temperature conditions for safe operation of the steel.Originality/value: Information available in literature does not clearly indicate what amount of secondary phases existing in duplex stainless steel microstructure can be acceptable. The current study shows that duplex 2205 steel affected by thermal cycles and containing about 10% of sigma phase still exhibit acceptable mechanical properties.

  3. Internal variable approach to superplastic deformation of duplex stainless steel

    International Nuclear Information System (INIS)

    An internal variable theory has been used in this study to investigate quantitatively the major deformation mechanism of a duplex stainless steel. The flow curves obtained from load relaxation tests were found separable into two parts, viz. Grain Matrix Deformation (GMD) curve and Grain/Phase Boundary Sliding (G/PBS) curve as was predicted by the internal variable theory. The major deformation mechanism of duplex stainless steel at high temperature is found to be a Dynamic Recrystallization (DRX) at an early stage of deformation, but grain/phase boundary sliding becomes the major deformation mechanism at the late stage of deformation. Additionally, χ phase precipitated first by replacing Mo with W in duplex stainless steels appears to improve the superplastic deformation characteristics when it exists below a critical level

  4. Corrosion induced by cathodic hydrogen in 2205 duplex stainless steel

    Science.gov (United States)

    Michalska, J.

    2011-05-01

    In this work new results about the influence of cathodic hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel are described. The results were discussed by taking into account hydrogen charged samples and without hydrogen. The corrosion resistance to pitting was qualified with the polarization curves. The conclusion is that, hydrogen deteriorated the passive film stability and corrosion resistance to pitting of 2205 duplex stainless steel. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen action was dependent on the hydrogen charging conditions.

  5. Corrosion induced by cathodic hydrogen in 2205 duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Michalska, J, E-mail: joanna.k.michalska@polsl.pl [Department of Materials Science, Silesian University of Technology, Krasinskiego 8, 40-019 Katowice (Poland)

    2011-05-15

    In this work new results about the influence of cathodic hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel are described. The results were discussed by taking into account hydrogen charged samples and without hydrogen. The corrosion resistance to pitting was qualified with the polarization curves. The conclusion is that, hydrogen deteriorated the passive film stability and corrosion resistance to pitting of 2205 duplex stainless steel. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen action was dependent on the hydrogen charging conditions.

  6. Optimal Use of Duplex Stainless Steel in Storage Tanks

    OpenAIRE

    Talus, Eva

    2013-01-01

    The aim of this work is to get a better understanding of how optimal weight savings of the cylindrical shell plates in storage tanks can be reached using higher strength duplex material. The design criteria will be based on the requirements given by the American Petroleum Institute standards API 650 for welded storage tanks and API 12B for bolted storage tanks. The expected result is that use of duplex stainless steel instead of austenitic stainless steel can reduce the weight of the material...

  7. Investigation of corrosion resistance property of cold deformed (bended) duplex and super duplex stainless steel tubes

    OpenAIRE

    Dotel, Utsav Raj

    2014-01-01

    Cold deformation (bending) of stainless steel tubes is one of the efficient and cost effective methods to gain the required shapes of the tube that can be useful for different practical applications. Different mechanical properties can change after the plastic deformation of the material. The purpose of this study is to investigate the corrosion (basically pitting) resistant property of cold deformed Duplex and Super Duplex materials namely UNS S32205 and UNS S32750 respectively. The bended t...

  8. Corrosion behavior of duplex stainless steel in sulphuric acid

    International Nuclear Information System (INIS)

    Duplex stainless steels are alloyed and processed to develop microstructure of roughly equal amounts of ferrite and austenite. Duplex stainless steel constitute a new class of materials because they have balanced amounts of ferrite and austenite. Since they have high content of chromium and molybdenum present, thus they have good corrosion resistance. Their corrosion resistance is double to that of annealed austenitic stainless steels with regard to pitting, crevice corrosion, sulphide stress corrosion, and chloride stress corrosion environments. The corrosion behavior of duplex stainless steel in various concentrations of sulphuric acid was studied. The reactions were carried out by placing the steel specimen in a beaker containing a known concentration of sulphuric acid at room temperature for a definite period. Pits were initiated in duplex stainless steel specimen and the propagation of pits depends upon the concentration of the acid solution in which the sample is in contact. The weight loss for definite period of time were measured and corrosion rates were calculated in millimetres per year. The corrosion rates increases with an increase in acid concentration at room temperature. A comparison of the results obtained from various concentrations of sulphuric acid with the same concentrations of nitric acid is also discussed. (author)

  9. The role of duplex stainless steels for downhole tubulars

    International Nuclear Information System (INIS)

    In sour conditions there is an increasing trend to turn to corrosion resistant alloys for downhole tubulars. The most commonly used CRA tubular is 13Cr, and there are thousands of feet in service. However, there are limits to the use of 13Cr, ie., the risk of sulphide stress corrosion cracking at high H2S levels, and the possibility of pitting or high corrosion rates in waters with high chloride contents. Where the service conditions are felt to be too severe for 13Cr alloys it has been traditional to switch to nickel base alloys such as alloys 825 and C-276 (UNS N08825 and N10276). The alloys are much more expensive than 13Cr, and in recent years the duplex stainless steels have been selected as alloys with superior corrosion and SSCC resistance compared with 13Cr, and having lower cost than nickel alloys. Originally the 22Cr duplex alloy (UNS 31803) was used, but more recently the 25Cr super duplex alloys (UNS S32760 and S32750) have become more available. The present paper reviews the data available for 13Cr and the limits of applicability. Data is also presented for laboratory tests for both the 22Cr and 25Cr super duplex alloys. There is extensive service experience with both 22Cr and 25Cr super duplex in the North Sea, covering both downhole tubulars, manifold and post wellhead equipment. Data is presented showing some of the sour condition being experienced in the North Sea by super duplex alloys. These results show that there is a substantial gap between the limits of use for 13Cr and the 25Cr super duplex stainless steel alloys. This means that in many sour environments super duplex stainless steel provides a cost effective alternative to nickel-base alloys

  10. Properties of duplex stainless steels made by powder metallurgy

    Directory of Open Access Journals (Sweden)

    M. Rosso

    2007-04-01

    Full Text Available Purpose: of this paper was to examine the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering: rapid cooling have been applied in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy. Mechanical properties such as tensile strength, impact energy, hardness and wear rate were evaluated.Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good mechanical properties which depends on austenite/ferrite ratio in the microstructure and elements partitioning between phases. The additions of alloying elements powders (promoting formation ferritic and austenitic phase to master alloy powder, makes possible the formation of structure and properties of sintered duplex stainless steels. Sintered duplex steels obtained starting from austenitic and ferritic powders with admixture of elemental powders achieve lower mechanical properties when compared to composition obtained by mixing ferritic and austenitic powder in equal amounts.Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for mechanical properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates.Originality/value: The use of elemental powders added to a stainless steel base showed its potentialities, in terms of fair compressibility and final

  11. Ferrite stability in duplex austenitic stainless steel welds

    International Nuclear Information System (INIS)

    The presence of ferrite in austenitic stainless steel welds is known to be beneficial in avoiding hot cracking problems. In particular, the primary delta ferrite mode of solidification is important. For alloy compositions in which primary ferrite forms, it has been shown that up to approximately 40% ferrite may exist in the as-solidified structures. With further cooling, the ferrite becomes unstable, transforming to austenite. However, under typical welding conditions, the cooling rate is sufficiently high to suppress the complete transformation of ferrite and some residual ferrite is retained. For example, for Type 308 austenitic stainless steel filler metal, gas-tungsten arc welds contain 6 to 10% ferrite, although under equilibrium conditions at elevated temperatures, this same alloy can be homogenized into a fully austenitic structure. Thus, it is clear the retained ferrite in such duplex structure welds is unstable and transforms during elevated temperature applications. The stability of ferrite was investigated by measuring its composition after several different thermal treatments. The composition was measured by means of analytical electron microscopy of thinned foils, and only the major constituents, iron, chromium, and nickel, were analyzed. The composition of ferrite was measured as a function of aging time and temperature. It was found that, during aging, the ferrite composition changes and approaches a metastable equilibrium limit before eventually transforming to sigma phase or austenite. This limiting composition was determined as a function of temperature

  12. Thermal fatigue of austenitic and duplex stainless steels

    OpenAIRE

    Virkkunen, Iikka

    2001-01-01

    Thermal fatigue behavior of AISI 304L, AISI 316, AISI 321, and AISI 347 austenitic stainless steels as well as 3RE60 and ACX-100 duplex stainless steels was studied. Test samples were subjected to cyclic thermal transients in the temperature range 20 - 600°C. The resulting thermal strains were analyzed with measurements and numerical calculations. The evolution of thermal fatigue damage was monitored with periodic residual stress measurements and replica-assisted microscopy. The elastic strai...

  13. Study of the fatigue behaviour and damage of a aged duplex stainless steel; Etude du comportement et de l'endommagement en fatigue d'un acier inoxydable austeno-ferritique moule vieilli

    Energy Technology Data Exchange (ETDEWEB)

    Le Roux, J.Ch

    2000-07-01

    Cast duplex stainless steels are commonly used in components of pressurized water reactors primary circuit. When submitted to in-service temperatures embrittlement occurs because of the nucleation and growth of a harder phase in the ferrite by spinodal composition. Macrostructure of this steel (ferritic primary grain size is about 4-5 mm) and embrittlement of ferrite due to aging lead to a very high scattering of mechanical properties for monotonous loadings. We showed that, in spite of this macrostructure, the cyclic behaviour of aged duplex stainless steels fits usual Manson-Coffin law while initial hardening is followed by softening, in part because of the demodulation of the composition. The fatigue crack propagation rate of material follows a Paris law. While crack initiation mainly appears next to the millimetric cast defects, fatigue crack propagation remains a continuous mechanism. Ferritic and austenitic elements break successively (ferrite first breaks by cleavage, then austenite breaks by ductile fatigue). In spite of the fact that the aged ferrite is embrittled, cleavage microcracks, for load levels examined, seldom appear in ferrite at the crack tip and on both sides of the main crack. Effects of cast defects and crystallographic ferrite orientation were also studied. Propagation fatigue crack behaviour was modeled assuming that the crack tip material behaves as if it was submitted to low cycle fatigue loadings. If we consider a homogeneous material, results are in good agreement with experiments. (authors)

  14. Hydrogen embrittlement of super duplex stainless steel in acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Elhoud, A.M.; Renton, N.C.; Deans, W.F. [University of Aberdeen, School of Engineering, Aberdeen, AB24 3UE (United Kingdom)

    2010-06-15

    Super duplex stainless steel (SDSS) is a good choice of material when resistance to harsh environments is needed. Despite the material's excellent corrosion resistance and high strength, a number of in-service failures have been recorded. The root cause of these failures was environmentally induced cracking initiated at manufacturing and in-service metallurgical defects. In this study the hydrogen embrittlement of pre-strained super duplex stainless steel specimens was investigated after 48 h cathodic charging in 0.1 M H{sub 2}SO{sub 4}. The metallurgical changes that resulted from four levels of cold work (4, 8, 12, and 16% plastic strain) were considered and their effect on the embrittlement of the SDSS alloy was investigated. After hydrogen charging, the specimens were pulled immediately to failure and the mechanical properties evaluated. The obtaining fracture morphology was investigated using low and high magnification microscopy. Experimental results indicated that charging the super duplex stainless steel alloy with hydrogen caused varying degrees of embrittlement depending on cold work level. Increasing cold work resulted in a reduction of the elongation to failure. Microscopic investigation confirmed the significant effect of cold work on the hydrogen embrittlement susceptibility of the super duplex stainless steel alloy investigated. (author)

  15. Cavitation Erosion of Sensitized UNS S31803 Duplex Stainless Steels

    Science.gov (United States)

    Mitelea, Ion; Micu, Lavinia Mădălina; Bordeaşu, Ilare; Crăciunescu, Corneliu Marius

    2016-05-01

    During processing or use, duplex steels can be subjected to heating at high temperatures that can affect their behavior. This work aims to correlate the influence of the sensitization treatment on the ultrasonic cavitation erosion behavior of a UNS S31803 (X2CrNiMoN22-5-3) duplex stainless steel. Duplex stainless steels, formed as a result of rapid cooling after solution annealing, are sensitized at temperatures of 475 and 850 °C, respectively, leading to hardening and embrittlement due to the spinodal decomposition of the ferrite and the precipitation of secondary phases. The ultrasonic cavitation erosion experiments showed that the sensitization at 850 °C reduced the mean depth of erosion by about 11% and the mean depth of erosion rate by 28%. By contrast, the sensitization at 475 °C deteriorates the cavitation erosion resistance, increasing the erosion parameters by up to 22%, compared to the solution annealed state.

  16. Cavitation Erosion of Sensitized UNS S31803 Duplex Stainless Steels

    Science.gov (United States)

    Mitelea, Ion; Micu, Lavinia Mădălina; Bordeaşu, Ilare; Crăciunescu, Corneliu Marius

    2016-04-01

    During processing or use, duplex steels can be subjected to heating at high temperatures that can affect their behavior. This work aims to correlate the influence of the sensitization treatment on the ultrasonic cavitation erosion behavior of a UNS S31803 (X2CrNiMoN22-5-3) duplex stainless steel. Duplex stainless steels, formed as a result of rapid cooling after solution annealing, are sensitized at temperatures of 475 and 850 °C, respectively, leading to hardening and embrittlement due to the spinodal decomposition of the ferrite and the precipitation of secondary phases. The ultrasonic cavitation erosion experiments showed that the sensitization at 850 °C reduced the mean depth of erosion by about 11% and the mean depth of erosion rate by 28%. By contrast, the sensitization at 475 °C deteriorates the cavitation erosion resistance, increasing the erosion parameters by up to 22%, compared to the solution annealed state.

  17. Aging degradation of cast stainless steel

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast-duplex stainless steels under light-water reactor operating conditions. Data from room-temperature Charpy-impact tests for several heats of cast stainless steel aged up to 10,000 h at 350, 400, and 4500C are presented and compared with results from other studies. Microstructures of cast-duplex stainless steels subjected to long-term aging either in the laboratory or in reactor service have been characterized. The results indicate that at least two processes contribute to the low-temperature embrittleent of duplex stainless steels, viz., weakening of the ferrite/austenite phase boundary by carbide precipitation and embrittlement of ferrite matrix by the formation of additional phases such as G-phase, Type X, or the α' phase. Carbide precipitation has a significant effect on the onset of embrittlement of CF-8 and -8M grades of stainless steels aged at 400 or 4500C. The existing correlations do not accurately represent the embrittlement behavior over the temperature range 300 to 4500C. 18 refs., 13 figs

  18. Aging degradation of cast stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Chung, H.M.

    1985-10-01

    A program is being conducted to investigate the significance of in-service embrittlement of cast-duplex stainless steels under light-water reactor operating conditions. Data from room-temperature Charpy-impact tests for several heats of cast stainless steel aged up to 10,000 h at 350, 400, and 450/sup 0/C are presented and compared with results from other studies. Microstructures of cast-duplex stainless steels subjected to long-term aging either in the laboratory or in reactor service have been characterized. The results indicate that at least two processes contribute to the low-temperature embrittleent of duplex stainless steels, viz., weakening of the ferrite/austenite phase boundary by carbide precipitation and embrittlement of ferrite matrix by the formation of additional phases such as G-phase, Type X, or the ..cap alpha..' phase. Carbide precipitation has a significant effect on the onset of embrittlement of CF-8 and -8M grades of stainless steels aged at 400 or 450/sup 0/C. The existing correlations do not accurately represent the embrittlement behavior over the temperature range 300 to 450/sup 0/C. 18 refs., 13 figs.

  19. Optimisation of welding procedures for duplex and superduplex stainless steels

    International Nuclear Information System (INIS)

    Austenitic stainless steels are increasingly being replaced by duplex grades that can offer similar corrosion resistance with far higher strength. This increased strength makes it possible to reduce material consumption whilst also decreasing transport and construction costs. Although established welding methods used for austenitic steels can be used for duplex steels, modification of the procedures can lead to improved results. This paper reviews the welding of duplex stainless steel and examines precautions that may be required. The advantages and disadvantages of different welding methods are highlighted and some high productivity solutions are presented. The application of a more efficient process with a high deposition rate (e.g. flux- cored arc welding) can decrease labour costs. Further close control of heat input and interpass temperature can result in more favourable microstructures and final properties. Although welding adversely affects the corrosion resistance of austenitic and duplex stainless steels, particularly the pitting resistance, relative to the parent material, this problem can be minimised by proper backing gas protection and subsequent pickling.

  20. Influence of additional elements on thermoelectric power of cast duplex stainless steel

    International Nuclear Information System (INIS)

    The mechanical properties of cast duplex stainless steel, which is used for main coolant pipes of pressurized water reactor type nuclear power plants, change due to thermal aging. Therefore it is advisable to evaluate these changes non-destructively for the maintenance of the plant components. In previous studies, it has been shown that thermoelectric power (TEP) measurement is an effective method for evaluating thermal aging of cast duplex stainless steel, and the change in TEP calculated from a model which simulates Cr concentration fluctuation was qualitatively corresponding to the change in measured TEP. But the TEP calculated from this model is different from the measured TEP. One of the reasons for this difference is considered to be the influence of other elements added in cast duplex stainless steel. In this study, the influence of C, Si, Mn, and Mo contained in stainless steel on TEP was investigated experimentally from the measurement results of Fe-Cr-Ni ternary alloys and Fe-Cr-Ni alloys containing one element of C, Si, Mn, and Mo. It was found that the addition of C, Si, and Mn changed TEP in a negative direction and addition of Mo changed TEP in a positive direction. In addition, calculated TEP of stainless steel from its chemical composition and the influence of C, Si, Mn and Mo based on the measurement results of model alloys became close to measured TEP. (author)

  1. Duplex stainless steel—Microstructure and properties

    Science.gov (United States)

    Debold, Terry A.

    1989-03-01

    Literature describing the microstructure of austenitic-ferritic stainless steels is reviewed, including phases which can be deleterious, such as σ and ά. The mechanical properties and corrosion resistance of Carpenter Technology's 7-Mo PLUSsr stainless (UNS S32950) demonstrate the resistance of this material to the formation of these phases and their deleterious effects. This material was evaluated in the annealed and welded conditions and after extended thermal treatments to simulate boiler and pressure vessel service.

  2. Effect of ultrafine grain on tensile behaviour and corrosion resistance of the duplex stainless steel.

    Science.gov (United States)

    Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Limin, Dong

    2016-05-01

    The ultrafine grained 2205 duplex stainless steel was obtained by cold rolling and annealing. The tensile properties were investigated at room temperature. Comparing with coarse grained stainless steel, ultrafine grained sample showed higher strength and plasticity. In addition, grain size changed deformation orientation. The strain induced α'-martensite was observed in coarse grained 2205 duplex stainless steel with large strain. However, the grain refinement inhibited the transformation of α'-martensite;nevertheless, more deformation twins improved the strength and plasticity of ultrafine grained 2205 duplex stainless steel. In addition, the grain refinement improved corrosion resistance of the 2205 duplex stainless steel in sodium chloride solution. PMID:26952459

  3. Fracture mechanics analysis of cast duplex stainless steel elbows containing a surface crack

    International Nuclear Information System (INIS)

    EDF, in cooperation with the French Atomic Energy Commission (CEA) and Framatome, has conducted a research program on the fracture behaviour of aged cast duplex stainless steel elbows. The main task of this program consisted in testing two large diameter (580 mm O.D.) aged cast elbows under in-plane closure bending at 320 deg C. After a short presentation of the experimental results, the ductile fracture analyses performed are presented. (author)

  4. Kinetics of sigma phase formation in a Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Rodrigo Magnabosco

    2009-09-01

    Full Text Available This work determines the kinetics of sigma phase formation in UNS S31803 Duplex Stainless Steel (DSS, describing the phase transformations that occur in isothermal aging between 700 and 900 ºC for time periods up to 1032 hours, allowing the determination of the Time-Temperature-Precipitation (TTP diagram for sigma phase and proposing a model to predict the kinetics of sigma phase formation using a Johnson-Mehl-Avrami (JMA type expression. The higher kinetics of sigma phase formation occurs at 850 ºC. However, isothermal aging between 700 and 900 ºC for time periods up to 1032 hours are not sufficient to the establishment of thermodynamic equilibrium. Activation energy for both nucleation and growth of sigma phase is determined (185 kJ.mol-1 and its value is equivalent to the activation energy for Cr diffusion in ferrite, indicating that diffusion of Cr is probably the major thermally activated process involved in sigma phase formation. The determined JMA type expression presents good fit with experimental data between 700 and 850 ºC.

  5. Phase Separation in Lean-Grade Duplex Stainless Steel 2101

    Science.gov (United States)

    Garfinkel, David A.; Poplawsky, Jonathan D.; Guo, Wei; Young, George A.; Tucker, Julie D.

    2015-08-01

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C to 538°C. New lean-grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 h). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α' separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205, were used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard-grade DSS alloy 2205 but inferior to the lean-grade alloy 2003 in mechanical testing. APT data demonstrate that the degree of α-α' separation found in alloy 2101 closely resembles that of 2205 and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, although precipitates were not as abundant as was observed in 2205.

  6. Effects of low temperature aging on the mechanical properties and corrosion resistance of duplex and lean duplex stainless steels UNS S32205 and UNS S32304 Efeitos de envelhecimentos em baixas temperaturas nas propriedades mecânicas e resistência à corrosão dos aços duplex e lean duplex UNS S32205 e UNS S32304

    Directory of Open Access Journals (Sweden)

    Francis Gabriel Wasserman

    2013-06-01

    Full Text Available Duplex stainless steels (DSS with austenite-ferrite microstructure are high strength and corrosion resistant steels frequently used as pipes and accessories in chemical/petrochemical on/and off-shore industries. Low temperature heat treatments (400-475ºC may increase the hardness and wear resistance of duplex steels, due to a spinodal decomposition reaction of the ferrite, whose small particles α' precipitate in the matrix. In this work, several heat treatments at 400ºC and 475ºC with short duration (Os aços inoxidáveis duplex (AID com microestrutura austeno-ferrítica são aços de alta resistência mecânica, sendo utilizados em tubos e componentes nas indústrias química e petroquímica. Tratamentos térmicos em baixas temperaturas (400-475ºC podem aumentar a dureza e a resistência ao desgaste, devido à reação de decomposição espinoidal da ferrita, quando finas partículas de α' se precipitam na matriz. Nesse trabalho, diversos tratamentos térmicos de curta duração a 400ºC e 475ºC foram realizados nos aços UNS S32304 e UNS S32205. A cinética de precipitação foi estudada por meio de medidas de dureza. Ensaios de tração foram realizados em algumas condições para se avaliar o efeito do envelhecimento na ductilidade dos dois aços. O endurecimento do aço UNS S32205 é mais pronunciado do que o do aço UNS S32304, embora ambos os aços apresentem um ganho considerável de resistência com tratamentos térmicos de curta duração. Amostras de aço duplex tratadas a 475ºC por 4 h e 8 h não apresentaram qualquer prejuízo na resistência à corrosão nos ensaios de polarização cíclica e temperatura crítica de pites em meio contendo NaCl.

  7. Hyperbaric welding of duplex stainless steel pipelines offshore.

    OpenAIRE

    Farrell, J.

    1996-01-01

    Three duplex stainless steels (Avesta 2205, Sandvik SAF2507 and Zeron 100) were successfully welded automatically at a range of pressures from 1 to 32bar. The gas tungsten arc (GTA) welding process was chosen as it allows a high degree of control to be exercised during welding. Initial autogenous bead on plate welds established the effects of pressure on the welding process and allowed the process parameters to be determined for subsequent experiments. Analysis of the eff...

  8. Modeling and optimization of turning duplex stainless steels

    OpenAIRE

    Ali, Rastee Dalshad

    2015-01-01

    In the present dissertation, machining investigations into duplex stainless steels are performed under different and systematically well-structured modeling and optimization frameworks. Focusing on the main objective of finding optimum machining process parameters and com-prehensively applying the statistical design of experiments to design the experiments, the study tackles the challenge of integrating modeling and optimization algorithms using six different approaches. Firstly, sets of non-...

  9. Residual stresses and fatigue in a duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, Johan

    1999-05-01

    Duplex stainless steels, consisting of approximately equal amounts of austenite and ferrite, often combine the best features of austenitic and ferritic stainless steels. They generally have good mechanical properties, including high strength and ductility, and the corrosion resistance is often better than conventional austenitic grades. This has lead to a growing use of duplex stainless steels as a material in mechanically loaded constructions. However, detailed knowledge regarding its mechanical properties and deformation mechanisms are still lacking. In this thesis special emphasis has been placed on the residual stresses and their influence on mechanical behaviour of duplex stainless steels. Due to the difference in coefficient of thermal expansion between the two phases, tensile microstresses are found in the austenitic phase and balancing compressive microstresses in the ferritic phase. The first part of this thesis is a literature survey, which will give an introduction to duplex stainless steels and review the fatigue properties of duplex stainless steels and the influence of residual stresses in two-phase material. The second part concerns the evolution of the residual stress state during uniaxial loading. Initial residual stresses were found to be almost two times higher in the transverse direction compared to the rolling direction. During loading the absolute value of the microstresses increased in the macroscopic elastic regime but started to decrease with increasing load in the macroscopic plastic regime. A significant increase of the microstresses was also found to occur during unloading. Finite element simulations also show stress variation within one phase and a strong influence of both the elastic and plastic anisotropy of the individual phases on the simulated stress state. In the third part, the load sharing between the phases during cyclic loading is studied. X-ray diffraction stress analysis and transmission electron microscopy show that even if

  10. Residual stresses and fatigue in a duplex stainless steel

    International Nuclear Information System (INIS)

    Duplex stainless steels, consisting of approximately equal amounts of austenite and ferrite, often combine the best features of austenitic and ferritic stainless steels. They generally have good mechanical properties, including high strength and ductility, and the corrosion resistance is often better than conventional austenitic grades. This has lead to a growing use of duplex stainless steels as a material in mechanically loaded constructions. However, detailed knowledge regarding its mechanical properties and deformation mechanisms are still lacking. In this thesis special emphasis has been placed on the residual stresses and their influence on mechanical behaviour of duplex stainless steels. Due to the difference in coefficient of thermal expansion between the two phases, tensile microstresses are found in the austenitic phase and balancing compressive microstresses in the ferritic phase. The first part of this thesis is a literature survey, which will give an introduction to duplex stainless steels and review the fatigue properties of duplex stainless steels and the influence of residual stresses in two-phase material. The second part concerns the evolution of the residual stress state during uniaxial loading. Initial residual stresses were found to be almost two times higher in the transverse direction compared to the rolling direction. During loading the absolute value of the microstresses increased in the macroscopic elastic regime but started to decrease with increasing load in the macroscopic plastic regime. A significant increase of the microstresses was also found to occur during unloading. Finite element simulations also show stress variation within one phase and a strong influence of both the elastic and plastic anisotropy of the individual phases on the simulated stress state. In the third part, the load sharing between the phases during cyclic loading is studied. X-ray diffraction stress analysis and transmission electron microscopy show that even if

  11. Passivation of duplex stainless steel in solutions simulating chloride-contaminated concrete

    OpenAIRE

    Takenouti, H.; Soriano, L; Palacín, S.; Gutiérrez, A.; Velasco, F.; Blanco, G; Bautista, A.

    2007-01-01

    Most studies published to date on the corrosion behaviour of stainless reinforcing steel are based on austenitic steel. The market presence of corrugated duplex steel is growing, however. The present study compared passivity in 2205 type duplex and 304 type austenitic stainless steel. Polarization tests in chloride-containing Ca(OH)2 solutions confirmed the exceptional performance of duplex steels. X-ray photoelectronic spectroscopy (XPS) showed that the passive layer generated on duplex stai...

  12. Behaviour and design of cold-formed lean duplex stainless steel members

    OpenAIRE

    Huang, Yun'er; 黃韵兒

    2013-01-01

    Cold-formed stainless steel sections have been increasingly used in architectural and structural applications. Yet the high price of stainless steel limits the application to construction projects. The lean duplex stainless steel (EN 1.4162) offers an opportunity for stainless steels to be used more widely due to its competitive in price, good mechanical properties and corrosion resistance. The lean duplex stainless steel is a relatively new material, and research on this material is limited....

  13. EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

    Directory of Open Access Journals (Sweden)

    Prabhu Paulraj

    2015-08-01

    Full Text Available Duplex Stainless Steels (DSS and Super Duplex Stainless Steel (SDSS have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic phases and their effects on corrosion and mechanical properties. First the effect of various alloying elements on DSS and SDSS has been discussed followed by formation of various intermetallic phases. The intermetallic phases affect impact toughness and corrosion resistance significantly. Their deleterious effect on weldments has also been reviewed.

  14. Influence of the Quenching Rate on the Spinodal Decomposition in a Duplex Stainless Steel

    OpenAIRE

    Hedin, M.; J. Massoud; Danoix, F.

    1996-01-01

    Cast duplex stainless steels are known to be susceptible to embrittlement after long term ageing at intermediate temperatures (300-400°C). This embrittlement is related to the spinodal decomposition that occurs in the ferrite phase. Steels of equivalent composition after undergoing the seemingly same heat treatment exhibit different microstructural and mechanical evolutions. One of the assumptions which explains this is based on the influence of the quenching rate. For this purpose, a set of ...

  15. 475 °C Embrittlement in a duplex stainless steel UNS S31803

    OpenAIRE

    S.S.M. Tavares; R.F. de Noronha; M. R. da Silva; Neto, J.M.; Pairis, S.

    2001-01-01

    The susceptibility of a duplex stainless steel UNS S31803 to thermal embrittlement at 475 °C was evaluated by means of mechanical tests (impact energy and hardness), magnetic measurements (hysteresis and thermomagnetic analysis) and scanning electron microscopy. The results show that the material undergoes severe embrittlement and hardening in the first 100 h. The corrosion resistance of the ferrite phase in a 10%HNO3 + 0.05%HF solution deteriorated after 500 h of ageing. The Curie temperatur...

  16. Effect of microstructure on impact toughness of duplex and superduplex stainless steels

    OpenAIRE

    S. Topolska; J. Łabanowski

    2009-01-01

    Purpose: of this paper is to study the effect of heat treatments and resulting changes in microstructure on mechanical properties, mainly impact toughness, of commercial 2205 duplex stainless steel and higher alloy superduplex 2507 grade.Design/methodology/approach: Both steels were submitted to ageing treatments in the temperature range of 500-900 °C with exposure time periods 6 minutes, 1 hour and 10 hours. Light microscope examinations, hardness measurements and impact toughness tests were...

  17. TEM [transmission electron microscopy], APFIM [atom-probe field ion microscopy], and SANS [small-angle neutron scattering] examination of aged duplex stainless steel components from some decommissioned reactors

    International Nuclear Information System (INIS)

    Cast stainless steels, composed of duplex phases of austenite and ferrite, are used extensively in nuclear reactors because of their superior strength, weldability, resistance to stress corrosion cracking, and soundness of casting. For example, cast stainless steels are used for primary coiling pipes of pressurized water reactors (PWRs), and valves and pump casings of PWRs and boiling water reactors (BWRs), the structural integrity of which is vital for safe operation of the reactors. In the present investigation, microstructural characteristics of several long-term-aged field components from two decommissioned reactors have been examined by transmission electron microscopy (TEM), atom-probe field ion microscopy (APFIM), and small-angle neutron scattering (SANS) techniques to establish the embrittlement mechanisms for the reactor-aged material. The results have then been compared to those of the laboratory-aged specimens obtained for the temperature range between 300 and 450 degree C. The chemical compositions and ferrite contents of the reactor components are listed. KRB BWR (located in Gundremmingen, Federal Republic of Germany) had been in service for ∼12 yr, and the Shippingport PWR (near Pittsburgh, Pennsylvania) had operated for ∼22 yr

  18. Magnetic characterisation of duplex stainless steel

    Science.gov (United States)

    Mészáros, I.

    2006-02-01

    Heat treatment-induced microstructural processes were studied by different non-destructive magnetic and mechanical material testing methods in the present work. A commercial SAF 2507 type superduplex stainless steel was investigated. This alloy contains about 40% metastable ferrite which can decompose to a sigma phase and secondary austenite due to heat treatment. All the mechanical, corrosion resistance and magnetic properties are strongly influenced by this microstructural changes. This study had two aims: to understand better the kinetics of the ferrite decomposition process and to study the application possibilities of the applied magnetic measurements. This paper presents an application possibility of the nonlinear harmonics analysis measurement and demonstrates the possibility to find a quantitative correlation between measured harmonics and mechanical properties obtained from destructive tests.

  19. Corrosion resistance properties of sintered duplex stainless steel

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2006-09-01

    Full Text Available Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245 °C/min and slow cooling of 5 °C/min in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy and EDS chemical analysis of microstructure components. Corrosion properties have been studied through electrochemical methods in 1M NaCl water solutionFindings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good corrosion properties which depends on austenite/ferrite ratio in the microstructure and elements partitioning between phases. Corrosion resistance of sintered stainless steels is strictly connected with the density and the pore morphology present in the microstructure too. The highest resistance to pitting corrosion in 1M NaCl solution was achieved for composition with approximate balance of ferrite and austenite in the microstructure.Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for corrosion properties and microstructures, nevertheless further tests should be carried out in

  20. Weld oxide formation on lean duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Westin, E.M. [Outokumpu Stainless, Avesta Research Centre, P.O. Box 74, SE-774 22 Avesta (Sweden)], E-mail: elin.westin@outokumpu.com; Olsson, C.-O.A. [Outokumpu Stainless, Avesta Research Centre, P.O. Box 74, SE-774 22 Avesta (Sweden); Hertzman, S. [Outokumpu Stainless Research Foundation, Brinellvaegen 23, SE-100 44 Stockholm (Sweden)

    2008-09-15

    Weld oxides have a strong influence on corrosion resistance, but have hitherto only been studied to a limited extent for duplex stainless steels. X-ray photoelectron spectroscopy (XPS) has here been used to study heat tint formed on gas tungsten arc (GTA) welds on the commercial duplex grades LDX 2101 (EN 1.4162/UNS S32101) and 2304 (EN 1.4362/UNS S32304) welded with and without nitrogen additions to the shielding gas. The process of heat tint formation is discussed in terms of transport phenomena to explain the effect of atmosphere, temperature and composition. The oxides formed were found to be enriched in manganese and corrosion testing shows that nitrogen has a strong influence on the weld oxide. A mechanism is proposed including evaporation from the weld pool and subsequent redeposition.

  1. Weld oxide formation on lean duplex stainless steel

    International Nuclear Information System (INIS)

    Weld oxides have a strong influence on corrosion resistance, but have hitherto only been studied to a limited extent for duplex stainless steels. X-ray photoelectron spectroscopy (XPS) has here been used to study heat tint formed on gas tungsten arc (GTA) welds on the commercial duplex grades LDX 2101 (EN 1.4162/UNS S32101) and 2304 (EN 1.4362/UNS S32304) welded with and without nitrogen additions to the shielding gas. The process of heat tint formation is discussed in terms of transport phenomena to explain the effect of atmosphere, temperature and composition. The oxides formed were found to be enriched in manganese and corrosion testing shows that nitrogen has a strong influence on the weld oxide. A mechanism is proposed including evaporation from the weld pool and subsequent redeposition

  2. Weld failure analysis of 2205 duplex stainless steel nozzle

    Directory of Open Access Journals (Sweden)

    Jingqiang Yang

    2014-10-01

    Full Text Available Failure analyses of weld joint between the nozzle and the head of the reactor made of 2205 duplex stainless steel was performed by optical microscopy (OM and scanning electron microscopy (SEM. Cracks were found in HAZ of the weld. The depth of the cracks is equal to the thickness of the inner weld. Localized uneven distribution of ferrite/austenite with 80–90% ferrite in weld is found. Results show that the cracks occurred along columnar granular with cleavage fracture. Poor weld process probably results in these cracks.

  3. Weld failure analysis of 2205 duplex stainless steel nozzle

    OpenAIRE

    Jingqiang Yang; Qiongqi Wang; Zhongkun Wei; Kaishu Guan

    2014-01-01

    Failure analyses of weld joint between the nozzle and the head of the reactor made of 2205 duplex stainless steel was performed by optical microscopy (OM) and scanning electron microscopy (SEM). Cracks were found in HAZ of the weld. The depth of the cracks is equal to the thickness of the inner weld. Localized uneven distribution of ferrite/austenite with 80–90% ferrite in weld is found. Results show that the cracks occurred along columnar granular with cleavage fracture. Poor weld process pr...

  4. Behavior of duplex stainless steel casting defects under mechanical loadings

    International Nuclear Information System (INIS)

    Several components in the primary circuit of pressurized water reactors are made of cast duplex stainless steels. This material contains small casting defects, mainly shrinkage cavities, due to the manufacturing process. In safety analyses, the structural integrity of the components is studied under the most severe assumptions: presence of a large defect, accidental loadings and end-of-life material properties accounting for its thermal aging embrittlement at the service temperature. The casting defects are idealized as semi-circular surface cracks or notches that have envelope dimensions. In order to assess the real severity of the casting defects under mechanical loadings, an experimental program was carried out. It consisted of testing, under both cyclic and monotonic solicitations, three-point bend specimens containing either a natural defect (in the form of a localized cluster of cavities) or a machined notch having the dimensions of the cluster's envelope. The results show that shrinkage cavities are far less harmful than envelope notches thanks to the metal bridges between cavities. Under fatigue loadings, the generalized initiation of a cluster of cavities (defined when the cluster becomes a crack of the same global size) is reached for a number of cycles that is much higher than the one leading to the initiation of a notch. In the case of monotonic loadings, specimens with casting defects offer a very high resistance to ductile tearing. The tests are analyzed in order to develop a method that takes into account the behavior of casting defects in a more realistic fashion than by an envelope crack. Various approaches are investigated, including the search of equivalent defects or of criteria based on continuum mechanics concepts, and compared with literature data. This study shows the conservatism of current safety analyses in modeling casting defects by envelope semi-elliptical cracks and contributes to the development of alternative approaches. (orig.)

  5. Toughness and other mechanical properties of the duplex stainless steel 2205

    International Nuclear Information System (INIS)

    The use and range of potential applications of duplex stainless steel continuously increase. An overview of the mechanical properties of duplex stainless steel 2205 is presented with focus on toughness properties. Impact and fracture toughness as well as strength results from the European research project, EcoPress, are presented. (orig.)

  6. Modern high strength QT, TM and duplex-stainless steels

    International Nuclear Information System (INIS)

    Pressure vessels are commonly manufactured with normalised steel grades with a yield strength up to 355 MPa or with austenitic stainless steels when corrosion as to be considered. From three decades, modern steels with higher mechanical properties - up to yield strength of 960 Mpa - are available and largely used for other applications where weight saving is of major importance as per off-shore, bridges, cranes, shipbuilding, line pipes.. The paper presents these modern steel's families - TMCP (Thermo Mechanically Controlled Process), QT (Quenched and Tempered) and Duplex (austeno-ferritic) stainless - in comparison with the normalised and austenitic steel grades. The following aspects are presented: the main mechanical properties (tensile and Charpy) as per the requirements of the standards for pressure equipment; some examples of use of these modern steels in the industry are given; the limitations of the forming conditions are considered; the weldability aspects and welds properties are developed; the interest of the PWHT (Post Weld Heat Treatment) is discussed. (orig.)

  7. Thermal treatment effects on laser surface remelting duplex stainless steel

    Science.gov (United States)

    do Nascimento, Alex M.; Ierardi, Maria Clara F.; Aparecida Pinto, M.; Tavares, Sérgio S. M.

    2008-10-01

    In this paper the microstructural changes and effects on corrosion resistance of duplex stainless steels UNS S32304 and UNS S32205, commonly used by the petroleum industry, were studied, following the execution of laser surface remelting (LSM) and post-thermal treatments (TT). In this way, data was obtained, which could then be compared with the starting condition of the alloys. In order to analyze the corrosion behaviour of the alloys in the as-received conditions, treated with laser and after post-thermal treatments, cyclic polarization tests were carried out. A solution of 3.5% NaCl (artificial sea water) was used, as duplex stainless steels are regularly used by the petroleum industry in offshore locations. The results obtained showed that when laser surface treated, due to rapid resolidification, the alloys became almost ferritic, and since the level of nitrogen in the composition of both alloys is superior to their solubility limit in ferrite, a precipitation of Cr2N (chromium nitrides) occurred in the ferritic matrix, causing loss of corrosion resistance, thus resulting in an increase in surface hardness. However, after the post-thermal treatment the alloys corrosion resistance was restored to values close to those of the as-received condition.

  8. The influence of sintering time on the properties of PM duplex stainless steel

    OpenAIRE

    Z. Brytan; L.A. Dobrzański; M. Actis Grande; M. Rosso

    2009-01-01

    Purpose: The purpose of this paper is to analyse the effect of sintering time on the pore morphology, microstructural changes, tensile properties and corrosion resistance of vacuum sintered duplex stainless steel.Design/methodology/approach: In presented study PM duplex stainless steels were obtained through mixing base ferritic stainless steel powder with controlled addition of elemental alloying powders and then sintered in a vacuum furnace with argon backfilling at 1250°C for different tim...

  9. Corrosion Behavior of Austenitic and Duplex Stainless Steels in Lithium Bromide

    OpenAIRE

    Ayo Samuel AFOLABI; Alaneme, K.K.; Samson Oluwaseyi BADA

    2009-01-01

    The corrosion behavior of austenitic and duplex stainless steels in various concentrations of lithium, bromide solution was investigated by using the conventional weight loss measurement method. The results obtained show that corrosion of these steels occurred due to the aggressive bromide ion in the medium. Duplex stainless steel shows a greater resistance to corrosion than austenitic stainless steel in the medium. This was attributed to equal volume proportion of ferrite and austenite in th...

  10. Experimental Study of the Thermal Diffusivity and Heat Capacity Concerning Some Duplex Stainless Steel

    OpenAIRE

    Riad Harwill Abdul Abas; Nabil Kadhim Taieh

    2015-01-01

    In the present work, thermal diffusivity and heat capacity measurements have been investigated in temperature range between RT and 1473 K for different duplex stainless steel supplied by Outokumpu Stainless AB, Sweden. The purpose of this study is to get a reliable thermophysical data of these alloys and to study the effect of microstructure on the thermal diffusivity and heat capacity value. Results show the ferrite content in the duplex stainless steel increased with temperature at equilibr...

  11. Innovative PM duplex stainless steels obtained basing on the Schaeffler diagram

    OpenAIRE

    L.A. Dobrzański; Z. Brytan; M. Actis Grande; Rosso, M.

    2008-01-01

    Purpose: The purpose of this paper was to describe the sintered duplex stainless steels manufactured in sinterhardeningprocess and its usability in field of stainless steels and moreover using computer software to calculatethe powder mix composition.Design/methodology/approach: In presented paper duplex stainless steels were obtained through powdermetallurgy starting from austenitic or ferritic base powders by controlled addition of alloying elements powder. In thestudies besides the preparat...

  12. Microstructural study of thermally aged duplex stainless steel deformation and fracture modes; Etude microstructurale des modes de deformation et de rupture d`un acier austenoferritique vieilli thermiquement

    Energy Technology Data Exchange (ETDEWEB)

    Verhaeghe, B. [Institut national polytechnique, 38 - Grenoble (France)

    1996-12-31

    The aim of this work is to study the micro mechanisms of deformation and rupture of an austeno ferritic stainless steel (Z 3 CND 22-10 M) with 33 % of ferrite. It is studied after ageing 1 000 h at 400 deg. C and 8 000 h at 350 deg. C and compared to the `as received` state. During ageing the ferritic phase undergoes microstructural evolutions which affects its properties. The two ageing treatments lead to roughly the same level of embrittlement. Microstructural characterisation shows that both phases percolate and exhibit orientation relationships close to Kurdjumov-Sachs ones. Mechanical properties of the steel were characterised for different ageing treatments at room temperature and at 320 deg. C. The interface is particularly strong and ensures the load transfer to ferrite even if this phase contains cleavage cracks. Moreover the interface does not oppose slip transmission which is instead controlled by localised glide in the ferritic phase. If activated slip systems of austenite are common with ferrite, slip transmission from austenite to ferrite indeed occurs through the=e interface. If they are not common, dislocations cross-slip back into the austenite. At 320 deg. C cross-slip occurs even far from the interface. Damage starts by nucleation in ferrite of cleavage cracks which propagate between austenite islands. Crack propagation is controlled by stretching of austenite ligaments. The material breaks by ductile tearing of austenite islands when the crack eventually percolates in the ferritic phase. The ductility of the material can be correctly describer using a simple model that takes into account the tearing-off the ductile-phase. (author). 153 refs.

  13. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on long-term thermal embrittlement of cast duplex stainless steels in LWR systems during the six months from October 1991 to March 1992. Charpy-impact, tensile, and fracture toughness J-R curve data are presented for several heats of cast stainless steel that were aged 10,000-58,000 h at 290, 320, and 350 degree C. The results indicate that thermal aging decreases the fracture toughness of cast stainless steels. In general, CF-3 steels are the least sensitive to thermal aging and CF-8M steels are the most sensitive. The values of fracture toughness JIC and tearing modulus for CF-8M steels can be as low as ∼90 kJ/m2 and ∼60, respectively. The fracture toughness data are consistent with the Charpy-impact results, i.e. unaged and aged steels that show low impact energy also exhibit lower fracture toughness. All steels reach a minimum saturation fracture toughness after thermal aging; the time to reach saturation depends on the aging temperature. The results also indicate that low-strength cast stainless steels are generally insensitive to thermal aging

  14. Corrosion Behavior of Austenitic and Duplex Stainless Steels in Lithium Bromide

    Directory of Open Access Journals (Sweden)

    Ayo Samuel AFOLABI

    2009-07-01

    Full Text Available The corrosion behavior of austenitic and duplex stainless steels in various concentrations of lithium, bromide solution was investigated by using the conventional weight loss measurement method. The results obtained show that corrosion of these steels occurred due to the aggressive bromide ion in the medium. Duplex stainless steel shows a greater resistance to corrosion than austenitic stainless steel in the medium. This was attributed to equal volume proportion of ferrite and austenite in the structure of duplex stainless steel coupled with higher content of chromium in its composition. Both steels produced electrochemical noise at increased concentrations of lithium bromide due to continuous film breakdown and repair caused by reduction in medium concentration by the alkaline corrosion product while surface passivity observed in duplex stainless steel is attributed to film stability on this steel.

  15. Phase transformations evaluation on a UNS S31803 duplex stainless steel based on nondestructive testing

    Energy Technology Data Exchange (ETDEWEB)

    Macedo Silva, Edgard de, E-mail: edgard@cefetpb.edu.br [Centro federal de Educacao Tecnologica da Paraiba (CEFET PB), Area da Industria, Avenida 1o de Maio, 720 - 58015-430 - Joao Pessoa/PB (Brazil); Costa de Albuquerque, Victor Hugo, E-mail: victor.albuquerque@fe.up.pt [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Cidade Universitaria, S/N - 58059-900 - Joao Pessoa/PB (Brazil); Pereira Leite, Josinaldo, E-mail: josinaldo@ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Cidade Universitaria, S/N - 58059-900 - Joao Pessoa/PB (Brazil); Gomes Varela, Antonio Carlos, E-mail: varela@cefetpb.edu.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Cidade Universitaria, S/N - 58059-900 - Joao Pessoa/PB (Brazil); Pinho de Moura, Elineudo, E-mail: elineudo@pq.cnpq.br [Universidade Federal do Ceara (UFC), Departamento de Engenharia Metalurgica e de Materiais, Campus do Pici, Bloco 715, 60455-760 - Fortaleza/CE (Brazil); Tavares, Joao Manuel R.S., E-mail: tavares@fe.up.pt [Faculdade de Engenharia da Universidade do Porto (FEUP), Departamento de Engenharia Mecanica e Gestao Industrial (DEMEGI)/Instituto de Engenharia Mecanica e Gestao Industrial - INEGI, Rua Dr. Roberto Frias, s/n, 4200-465 Porto (Portugal)

    2009-08-15

    Duplex stainless steel presents special mechanical properties such as, for example, mechanical and corrosion strength, becoming competitive in relation to the other types of stainless steel. One of the great problems of duplex stainless steel microstructural changes study is related to embrittlement above 300 deg. C, with the precipitation of the {alpha}' phase occurring over the ferritic microstructure. Aiming to characterise embrittlement of duplex stainless steel, hardening kinetics, from 425 to 475 deg. C, was analysed through the speed of sound, Charpy impact energy, X-ray diffraction, hardness and microscopy parameters. The presence of two hardening stages, detected through the speed of sound, was observed, one being of brittle characteristic and the other ductile. Moreover, the speed of sound showed a direct correlation with the material's hardness. Thus, it is concluded that the speed of sound is a promising nondestructive parameter to follow-up embrittlement in duplex stainless steel.

  16. Phase transformations evaluation on a UNS S31803 duplex stainless steel based on nondestructive testing

    International Nuclear Information System (INIS)

    Duplex stainless steel presents special mechanical properties such as, for example, mechanical and corrosion strength, becoming competitive in relation to the other types of stainless steel. One of the great problems of duplex stainless steel microstructural changes study is related to embrittlement above 300 deg. C, with the precipitation of the α' phase occurring over the ferritic microstructure. Aiming to characterise embrittlement of duplex stainless steel, hardening kinetics, from 425 to 475 deg. C, was analysed through the speed of sound, Charpy impact energy, X-ray diffraction, hardness and microscopy parameters. The presence of two hardening stages, detected through the speed of sound, was observed, one being of brittle characteristic and the other ductile. Moreover, the speed of sound showed a direct correlation with the material's hardness. Thus, it is concluded that the speed of sound is a promising nondestructive parameter to follow-up embrittlement in duplex stainless steel.

  17. XPS study of duplex stainless steel oxidized by oxygen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Donik, Crtomir [Institute of Metals and Technology, Lepi pot 11, SI-1000 Ljubljana (Slovenia)], E-mail: crtomir.donik@imt.si; Kocijan, Aleksandra [Institute of Metals and Technology, Lepi pot 11, SI-1000 Ljubljana (Slovenia); Grant, John T. [Research Institute, University of Dayton, 300 College Park, Dayton OH 45469-0051 (United States); Jenko, Monika [Institute of Metals and Technology, Lepi pot 11, SI-1000 Ljubljana (Slovenia); Drenik, Aleksander [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Pihlar, Boris [Faculty of Chemistry and Chemical Technology, Askerceva 5, SI-1000 Ljubljana (Slovenia)

    2009-04-15

    Surface oxidation of the duplex stainless steel DSS alloy 2205 was studied by X-ray photoelectron spectroscopy (XPS) and SEM imaging. The experiments were performed on the alloy after controlled oxidation with oxygen atoms created in an inductively coupled plasma. Experiments were performed at temperatures from room temperature up to 700 deg. C. Compositions of the modified oxidized surfaces were obtained from XPS survey scans, and the chemistries of selected elements from higher energy resolution scans of appropriate peaks. The morphologies of the surfaces were obtained using field emission scanning electron microscopy at different magnifications, up to 10,000x. Different Fe/Cr/Mn oxidized layers and different oxide thicknesses were observed and correlated with temperature.

  18. Electromagnetic non-destructive technique for duplex stainless steel characterization

    Science.gov (United States)

    Rocha, João Vicente; Camerini, Cesar; Pereira, Gabriela

    2016-02-01

    Duplex stainless steel (DSS) is a two-phase (ferrite and austenite) material, which exhibits an attractive combination of mechanical properties and high corrosion resistance, being commonly employed for equipment of petrochemical plants, refining units and oil & gas platforms. The best properties of DSS are achieved when the phases are in equal proportions. However, exposition to high temperatures (e.g. welding process) may entail undesired consequences, such as deleterious phases precipitation (e.g. sigma, chi) and different proportion of the original phases, impairing dramatically the mechanical and corrosion properties of the material. A detailed study of the magnetic behavior of DSS microstructure with different ferrite austenite ratios and deleterious phases content was accomplished. The non destructive method evaluates the electromagnetic properties changes in the material and is capable to identify the presence of deleterious phases into DSS microstructure.

  19. Hydrogen effects in duplex stainless steel welded joints - electrochemical studies

    Science.gov (United States)

    Michalska, J.; Łabanowski, J.; Ćwiek, J.

    2012-05-01

    In this work results on the influence of hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel (DSS) welded joints are described. The results were discussed by taking into account three different areas on the welded joint: weld metal (WM), heat-affected zone (HAZ) and parent metal. The corrosion resistance was qualified with the polarization curves registered in a synthetic sea water. The conclusion is that, hydrogen may seriously deteriorate the passive film stability and corrosion resistance to pitting of 2205 DSS welded joints. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen degradation was dependent on the hydrogen charging conditions. WM region has been revealed as the most sensitive to hydrogen action.

  20. Optimization of welding variables for duplex stainless steel by GTAW and SMAW

    International Nuclear Information System (INIS)

    The main problems faced during the welding of duplex stainless steels are cleanliness and slag inclusions. In the present work the methods to eliminate these problems were studied during the welding of duplex stainless steel by Gas Tungsten Arc Welding (GTAW) and Shielded Metal Arc Welding (SMAW). Since the duplex stainless steel is an expensive material, the initial experiments for optimization of welding variables were. carried out on low carbon steel (CS) plates with duplex consumables. Welding of butt groove joints on CS plates was carried with various sets of welding variables i.e. current, voltage and arc energy using duplex consumables. The. radiographic inspection, micro-structural observations and hardness testing of the welds suggested the welding variables that will produce a sound weld on CS plate. These optimized variables were then used for the welding of edge groove joint and T -joint on duplex stainless steel by GTAW and SMAW processes. The hardness and micro-structural study of the joints produced on duplex stainless steel by GTAW and SMAW with duplex consumables were also studied. No slag inclusions and porosity were observed in the microstructure of these weldments and their properties were found similar to the parent metal. (author)

  1. Tensile properties of duplex UNS S32205 and lean duplex UNS S32304 steels and the influence of short duration 475 ºC aging

    Directory of Open Access Journals (Sweden)

    Sérgio Souto Maior Tavares

    2012-12-01

    Full Text Available Duplex stainless steels are high strength and corrosion resistant steels extensively used in the petrochemical and chemical industries. The aging at 475 ºC for long periods of time provokes embrittlement and deterioration of corrosion resistance. However, short duration aging at 475 ºC may be used as heat treatment to improve mechanical resistance with small decrease in the other properties. In this work the flow stress curves of lean duplex UNS S32304 and duplex UNS S32205 steels were modeled with Hollomon's equation and work hardening exponents (n were determined. The analyses were conducted in specimens annealed and heat treated at 475 ºC for short periods of time. The aging at 475 ºC for 4 hours, 8 hours and 12 hours promoted significant hardening with small decrease of ductility. The work hardening exponents of both steels were compared, being higher in the duplex steel than in the lean duplex grade.

  2. Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

    Science.gov (United States)

    Rahmani, Mehdi; Eghlimi, Abbas; Shamanian, Morteza

    2014-10-01

    To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

  3. Tensile properties of duplex UNS S32205 and lean duplex UNS S32304 steels and the influence of short duration 475 ºC aging

    OpenAIRE

    Sérgio Souto Maior Tavares; Juan Manuel Pardal; Hamilton Ferreira Gomes de Abreu; Cristiana dos Santos Nunes; Manoel Ribeiro da Silva

    2012-01-01

    Duplex stainless steels are high strength and corrosion resistant steels extensively used in the petrochemical and chemical industries. The aging at 475 ºC for long periods of time provokes embrittlement and deterioration of corrosion resistance. However, short duration aging at 475 ºC may be used as heat treatment to improve mechanical resistance with small decrease in the other properties. In this work the flow stress curves of lean duplex UNS S32304 and duplex UNS S32205 steels were modele...

  4. Alpha prime effect on mechanical properties and corrosion resistance of UR 52N+ duplex stainless steel; Efeito da fase alfa linha nas propriedadesmecanicas e de resistencia a corrosao do aco inoxidavel duplex UR 52N+

    Energy Technology Data Exchange (ETDEWEB)

    Fontes, Talita Filier

    2009-07-01

    Alpha prime phase leads to decreased corrosion resistance and mechanical properties losses of duplex stainless steels. In this work mechanical and electrochemical tests were performed in duplex stainless steel UR 52N+ aged at 475 degree C for various periods in order to determine the sensibility of these tests to alpha prime presence. Hardness tests showed a gradual increase in its values; on the other hand, impact tests revealed that the material aged for 12h losses about 80% of energy absorption capacity of the solution annealed sample. Notwithstanding cyclic polarization tests showed that significant changes are only noted for aging times greater than 96h. (author)

  5. Microstructure and properties of welds in the lean duplex stainless steel LDX 2101

    OpenAIRE

    Westin, Elin M.

    2010-01-01

    Duplex stainless steels can be very attractive alternatives to austenitic grades due to their almost double strength at equal pitting corrosion resistance. When welding, the duplex alloys normally require addition of filler metal, while the commodity austenitic grades can often be welded autogenously. Over-alloyed consumables are used to counteract segregation of important alloying elements and to balance the two phases, ferrite and austenite, in the duplex weld metal. This work focuses on th...

  6. Characterization of duplex stainless steel weld metals obtained by hybrid plasma-gas metal arc welding

    OpenAIRE

    Koray Yurtisik; Suha Tirkes; Igor Dykhno; C. Hakan Gur; Riza Gurbuz

    2013-01-01

    Despite its high efficiency, autogenous keyhole welding is not well-accepted for duplex stainless steels because it causes excessive ferrite in as-welded duplex microstructure, which leads to a degradation in toughness and corrosion properties of the material. Combining the deep penetration characteristics of plasma arc welding in keyhole mode and metal deposition capability of gas metal arc welding, hybrid plasma - gas metal arc welding process has considered for providing a proper duplex mi...

  7. Influence of microstructure and environment on the fatigue behaviour of duplex stainless steels alloyed with nitrogen

    International Nuclear Information System (INIS)

    The favourable effect of nitrogen on the mechanical properties and the resistance to corrosion, now recognised for the austenitic stainless steels, aroused the interest for the development of dual - phase stainless steels constituted by austenite and ferrite (also labelled duplex steels) with high nitrogen content of which the interest lies in the lowest quantities of expensive alloying elements. The main purpose of this work is the study of the low cycle fatigue (LCF) behaviour of new grades of duplex steels and the determination of the microstructural scale conferring the best properties. LCF tests carried out in air on two duplex steels, with 0.24 wt% and 0.4 wt% of nitrogen and phase proportions of 50%α/50%γ and 30%α/70%γ respectively, led to the conclusion of a dependence of materials behaviour as a function of the strain level. The observations of samples by scanning electron microscopy showed that, for the lowest amplitudes, the plastic deformation is essentially accommodate by the austenite. Beyond a certain deformation, both phases alternatively accommodate this plastic deformation. In the presence of corrosive media, a general decrease of material fatigue lives has been noticed, except for the 0.4 wt% nitrogen containing steel which is less sensible. In the same way, an ageing treatment at 475 C for 200 hours lowers considerably the fatigue lives of the 0.24 wt% nitrogen steel while the resistance of the 0.4% nitrogen alloy is nearly unchanged. Whatever the conditions, the reductions of fatigue lives were systematically attributed to the ferritic phase behaviour. Then, elaborating these grades of duplex steels with 0.4 wt% of nitrogen favours a structure with 70% of austenite and leads to a very interesting fatigue behaviour. (O.M.)

  8. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on long-term embrittlement of cast duplex stainless steels in LWR systems during the six months from April to September 1987. Microstructural studies were conducted to investigate the kinetics of spinodal decomposition and G-phase and γ2 precipitation of CF-8 and CF-8M grades of cast stainless steel. The results indicate that the presence of Mo in CF-8M steel accelerates spinodal decomposition as well as G-phase and γ2 precipitation. Examination of the long-term-aged CF-8M steels also revealed a ''spinodal-like'' decomposition of the austenite caused by segregation of Fe and Ni in the matrix. Preliminary results indicate that local regions of austenite are significantly hardened by the decomposition. Charpy-impact, tensile, and J-R curve data are presented for several heats of cast stainless steels aged at temperatures between 320 and 450 degree C for times up to 10,000 h. The results indicate that concentrations of carbon and nitrogen in the steel and the ferrite content and spacing are important parameters in controlling low-temperature embrittlement. The existing correlations for estimating the extent and kinetics of embrittlement do not accurately represent the properties of different grades and compositions of cast stainless steel after thermal aging. 36 refs., 24 figs., 5 tabs

  9. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on longterm thermal embrittlement of cast duplex stainless steels in LWR systems during the six months from April--September 1992. A procedure and correlations are presented for predicting Charpy-impact energy, tensile flow stress, fracture toughness J-R curve, tearing modulus, and JIC of aged cast stainless steels from known material information. The ''saturation'' impact strength and fracture toughness of a specific cast stainless steel, i.e., the minimum value that would be achieved for the material after long-term service, is estimated from the chemical composition of the steel. Mechanical properties as a function of time and temperature of reactor service are estimated from impact energy and flow stress of the unaged material and the kinetics of embrittlement, which are also determined from chemical composition. The JIC values are determined from the estimated J-R curve and flow stress. Examples of estimating mechanical properties of cast stainless steel components during reactor service are presented. A common ''lower-bound'' J-R curve for cast stainless steels of unknown chemical composition is also defined for a given grade of steel, ferrite content, and temperature

  10. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on long-term embrittlement of cast duplex stainless steels in LWR systems during the six months from April to September 1991. A procedure and correlations are presented for predicting Charpy-impact energy, tensile flow stress, fracture toughness J-R curve, and JIC of aged cast stainless steels from known material information. The ''saturation'' impact strength and fracture toughness of a specific cast stainless steel, i.e., the minimum value that would be achieved for the material after long-term service, is estimated from the chemical composition of the steel. Mechanical properties as a function of time and temperature of reactor service are estimated from impact energy and flow stress of the unaged material and the kinetics of embrittlement, which are also determined from chemical composition. The JIC values are determined from the estimated J-R curve and flow stress. Examples of estimating mechanical properties of cast stainless steel components during reactor service are presented. A common ''lower-bound'' J-R curve for cast stainless steels of unknown chemical composition is also defined for a given grade of steel, ferrite content, and temperature

  11. The fracture mechanisms in duplex stainless steels at sub-zero temperatures

    OpenAIRE

    Pilhagen, Johan

    2013-01-01

    The aim of the thesis was to study the susceptibility for brittle failures and the fracture process of duplex stainless steels at sub-zero temperatures (°C). In the first part of the thesis plates of hot-rolled duplex stainless steel with various thicknesses were used to study the influence of delamination (also known as splits) on the fracture toughness. The methods used were impact and fracture toughness testing. Light optical microscopy and scanning electron microscopy were used to investi...

  12. Effect of Deleterious Phases on Corrosion Resistance of Duplex Stainless Steel (2205)

    OpenAIRE

    AbdulKadar M. Godil; Hitesh A. Narsia; M. N. Patel; Mr. Paresh U. Haribhakti

    2013-01-01

    Duplex stainless steel is a Ferritic(BCC)-Austenitic(FCC) steel, covers the advantages of both Austenitic and Ferritic Stainless steels. They having good mechanical and corrosion resistance properties are widely used in many industries like chemical plants, refineries for critical equipments such as pressure vessels, heatexchangers, water heaters. Major problem occurs with duplex steels when they are worked or heated above about temperature of 280°C. Detrimental phases like Sigma, Chi, Laves ...

  13. Influence of sintering parameters on the properties of duplex stainless steel

    OpenAIRE

    L.A. Dobrzański; Z. Brytan; M. Actis Grande; M. Rosso

    2007-01-01

    Purpose: of this paper was to examine the influence of sintering parameters like time, temperature, atmosphereand gas pressure under cooling stage on the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powdermetallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements,such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s ...

  14. OBSERVATIONS OF STRESS CORROSION CRACKING BEHAVIOUR IN SUPER DUPLEX STAINLESS STEEL

    OpenAIRE

    Al-Rabie, Mohammed

    2011-01-01

    The new generation of highly alloyed super duplex stainless steels such as Zeron 100 are preferable materials for industrial applications demanding high strength, toughness and superior corrosion resistance, especially against stress corrosion cracking (SCC). SCC is an environmentally assisted failure mechanism that occurs due to exposure to an aggressive environment while under a tensile stress. The mechanism by which SCC of duplex stainless steel is expected to suffer depends on the combina...

  15. Corrosion resistance of sintered duplex stainless steel evaluated by electrochemical method

    OpenAIRE

    L.A. Dobrzański; Z. Brytan; M. Actis Grande; M. Rosso

    2006-01-01

    Purpose: Purpose of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements. In the studies behind the ...

  16. Influence Of Heat Treatment On Duplex Stainless Steel To Study The Material Properties

    OpenAIRE

    Jithin M; Anees Abdul Hameed; Ben Jose; Anush Jacob

    2015-01-01

    Abstract The various heat treatment processes are annealing normalizing hardening tempering spheroidising surface hardening flame and induction hardening nitriding cyaniding carbonitriding carburizing etc Heat treatment on duplex stainless steel is to improve ductility toughness strength hardness and to relieve internal stress developed in the material. Here basically the experiment of hardness test impact test wear test and compression is done to get idea about heat treated duplex stainless ...

  17. INVESTIGATIONS INTO EFFECT OF RESIDUAL STRESSES ON MECHANICAL BEHAVIOUR OF DUPLEX STAINLESS STEEL WELD JOINT

    OpenAIRE

    Jamal Jalal Dawood; Charudatta Subhash Pathak; Atul Sitarm Padalkar

    2014-01-01

    Duplex stainless steel alloy is widely used in the manufacture of pressure vessels, nuclear plant, chemical refineries and paper mill. Welding is the most preferred fabrication method in these structural applications; however during welding the work piece is subjected to thermal cycle as a result residual stresses are developed in the weld. Residual stresses have significant effect on performance of the weld joint subjected to tensile loading. In addition to this duplex stainless steel is wel...

  18. Relationship between microstructure and fracture types in a UNS S32205 duplex stainless steel

    OpenAIRE

    Maria Victoria Biezma; Carlos Berlanga; Gorka Argandona

    2013-01-01

    Duplex stainless steels are susceptible to the formation of sigma phase at high temperature which could potentially be responsible for catastrophic service failure of components. Thermal treatments were applied to duplex stainless steels in order to promote the precipitation of different fractions of sigma phase into a ferrite-austenite microstructure. Quantitative image analysis was employed to characterize the microstructure and Charpy impact tests were used in order to evaluate the mechani...

  19. The effect of σ-phase precipitation at 800°C on the corrosion resistance in sea-water of a high alloyed duplex stainless steel

    OpenAIRE

    Wilms, M.E.; Gadgil, V.J.; Krougman, J.M.; IJsseling, F.P.

    1994-01-01

    Super-duplex stainless steels are recently developed high alloyed stainless steels that combine good mechanical properties with excellent corrosion resistance. Because of a high content of chromium and molybdenum, these alloys are susceptible to σ-phase precipitation during short exposure to temperatures between 650 and 950°C. The effect of 800°C aging on σ-phase formation and on the mechanical properties of a super-duplex stainless steel have been reported previously by the authors.1 This in...

  20. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on long-term thermal embrittlement of cast duplex stainless steels in LWR systems during the six months from April to September 1989. Tensile and fracture toughness data are presented for several heats of cast stainless steel that were aged up to 30,000 h at temperatures of 290--450 degree C. The results indicate that thermal aging increases the tensile stress and decreases the fracture toughness of the materials. In general, CF-3 steels are the least sensitive to thermal aging embrittlement and CF-8M steels are the most sensitive. The increase in flow stress of fully aged cast stainless steels is ∼10% for CF-3 steels and ∼20% for CF-8 and CF-8M steels. The fracture toughness JIC and average tearing modulus for heats that are sensitive to thermal aging (e.g., CF-8M steels) are as low as ∼90 kJ/m2 and ∼60, respectively. Correlations are presented for estimating the increase in flow stress of the steels from data for the kinetics of thermal embrittlement. 33 refs., 22 figs., 5 tabs

  1. Effect of Nanosize Yittria and Tungsten Addition to Duplex Stainless Steel During High Energy Planetary Milling

    Science.gov (United States)

    Nayak, A. K.; Shashanka, R.; Chaira, D.

    2016-02-01

    In this present investigation, elemental powders of duplex stainless steel composition (Fe-18Cr-13Ni) with 1 wt. % nano yittria and tungsten were milled separately in dual drive planetary mill (DDPM) for 10 h to fabricate yittria dispersed and tungsten dispersed duplex stainless steel powders. The milled powder samples were characterized by X-Ray diffraction and scanning electron microscopy (SEM) to study the size, morphology and phase evolution during milling. The gradual transformation from ferrite to austenite is evident from XRD spectra during milling. The crystallite size and lattice strain of yittria dispersed duplex stainless steel after 10 h milling were found to be 7 nm and 1.1% respectively. The crystallite size of tungsten dispersed duplex stainless steel was 5 nm. It has been observed from SEM analysis that particles size has been reduced from 40 to 5 μm in both cases. Annealing of 10 h milled powder was performed at 750°C for 1 h under argon atmosphere to study phase transformation in both yittria and tungsten dispersed duplex stainless steel. The XRD analysis of annealed stainless steel depicts the phase transformation from α-Fe to γ-Fe with the formation of oxides of Y,Fe and Cr. The differential scanning calorimetry analysis was conducted by heating the milled powder from room temperature to 1200°C under argon atmosphere to investigate the thermal analysis of both the stainless steel powders.

  2. Aging degradation of cast stainless steel

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. Microstructures of cast materials subjected to long-term aging either in reactor service or in the laboratory have been characterized by TEM, SANS, and APFIM techniques. Two precipitate phases, i.e., the Cr-rich α' and Ni- and Si-rich G phase, have been identified in the ferrite matrix of the aged steels. The results indicate that the low-temperature embrittlement is primarily caused by α' precipitates which form by spinodal decomposition. The relative contribution of G phase to loss of toughness is now known. Microstructural data also indicate that weakening of ferrite/austenite phase boundary by carbide precipitates has a significant effect on the onset and extent of embrittlement of the high-carbon CF-8 and CF-8M grades of stainless steels, particularly after aging at 400 or 4500C. Data from Charpy-impact, tensile, and J-R curve tests for several heats of cast stainless steel aged up to 10,000 h at 350, 400, and 4500C are presented and correlated with the microstructural results. Thermal aging of the steels results in an increase in tensile strength and a decrease in impact energy, J/sub IC/, and tearing modulus. The fracture toughness results show good agreement with the Charpy-impact data. The effects of compositional and metallurgical variables on loss of toughness are discussed

  3. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on long-term embrittlement of cast duplex stainless steels in LWR systems during the six months from April 1990 to September 1990. A procedure and correlations are presented for predicting fracture toughness J-R curves and impact strength of aged cast stainless steels from known material information. Fracture toughness of a specific cast stainless steel is estimated from the extent and kinetics of thermal embrittlement. The extent of thermal embrittlement is characterized by the room-temperature ''normalized'' Charpy impact energy. A correlation for the extent of embrittlement at ''saturation,'' i.e., the minimum impact energy that would be achieved by the material after long-term aging, is given is terms of a material parameter, φ, which is determined from the chemical composition. The fracture toughness J-R curve for the material is then obtained from correlations between room-temperature Charpy-impact energy and fracture toughness parameters. Fracture toughness as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which are determined from chemical composition. A common ''lower-bound'' J-R curve for cast stainless steels with unknown chemical composition is also defined for a given material specification, ferrite content, and temperature. Examples for estimating impact strength and fracture toughness of cast stainless steel components during reactor service are described. Mechanical-property degradation suffered by cast stainless steel components from the decommissioned Shippingport reactor has been characterized. The results are used to validate the correlations and benchmark the laboratory studies. Charpy-impact, tensile, and fracture toughness data for materials from the hot-leg shutoff valve and cold-leg check valves and pump volute are presented. 37 refs., 53 figs., 9 tabs

  4. Effect of stress and strain on corrosion resistance of duplex stainless steel

    International Nuclear Information System (INIS)

    The interplay of the mechanical and electrochemical phenomena has been a subject of active research. In this paper, corrosion resistance studies about SAF2205 and SAF2507 duplex stainless steel were carried out under elastic stress applied (100 MPa, 300 MPa, 500 MPa) and pre-strain (5%, 10%, 15%) in 3.5% NaCl and 2 mol/L HCl solution. Potentiodynamic anodic polarization study revealed that corrosion resistance of SAF2205 duplex stainless steel decreases slightly with increasing of elastic stress level and noticeably with increasing of pre-strained level. Scanning electron microscopy investigation on surface of the electrochemical tested SAF2205 duplex stainless steel samples indicated that pitting is always located in austenite grains when pre-strain level is below 5% (including different elastic stress level) and located on intersection of ferrite and austenite grain when pre-strain level is above 5%. For SAF2507 duplex stainless steel, elastic stress and pre-strain have no effect on general corrosion and pitting corrosion. Based on deformation mechanism of duplex structure and the relationship of mechanical load and corrosion potential, Pitting corrosion behavior of duplex stainless steel is explained and discussed

  5. Tooling solutions for sheet metal forming and punching of lean duplex stainless steel

    DEFF Research Database (Denmark)

    Wadman, Boel; Madsen, Erik; Bay, Niels;

    2012-01-01

    .4509 and lean duplex EN1.4162 in a production designed for austenitic stainless steels, such as EN1.4301 and 1.4401. The result is a guideline that summarizes how stainless material properties may affect tool degradation, and suggests tool solutions for reduced production disturbances and tool maintenance...

  6. Fracture toughness of a welded super duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Pilhagen, Johan, E-mail: pilhagen@kth.se [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden); Sieurin, Henrik [Scania CV AB, Södertälje (Sweden); Sandström, Rolf [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden)

    2014-06-01

    Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture.

  7. Fracture toughness of a welded super duplex stainless steel

    International Nuclear Information System (INIS)

    Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture

  8. Behavior of duplex stainless steel casting defects under mechanical loadings

    International Nuclear Information System (INIS)

    Several components in the primary circuit of pressurized water reactors are made of cast duplex stainless steels. This material contains small casting defects, mainly shrinkage cavities, due to the manufacturing process. In safety analyses, the structural integrity of the components is studied. In order to assess the real severity of the casting defects under mechanical loadings, an experimental program was carried out. It consisted of testing, under both cyclic and monotonic solicitations, three-point bend specimens containing either a natural defect (in the form of a localized cluster of cavities) or a machined notch having the dimensions of the cluster's envelope. The tests are analyzed in order to develop a method that takes into account the behavior of castings defects in a more realistic fashion than by an envelope crack. Various approaches are investigated, including the search of equivalent defects or of criteria based on continuum mechanics concepts, and compared with literature data. This study shows the conservatism of current safety analyses in modelling casting defects by envelope semi-elliptical cracks and contributes to the development of alternative approaches. (author)

  9. Eddy current techniques for super duplex stainless steel characterization

    Science.gov (United States)

    Camerini, C.; Sacramento, R.; Areiza, M. C.; Rocha, A.; Santos, R.; Rebello, J. M.; Pereira, G.

    2015-08-01

    Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content.

  10. Eddy current techniques for super duplex stainless steel characterization

    International Nuclear Information System (INIS)

    Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content. - Highlights: • Sigma phase precipitation, even for low amounts, dramatically affects SDSS properties. • SDSS samples were thermally treated and carefully characterized by X-Ray Diffraction. • NDT techniques detected low amounts of sigma phase in SDSS microstructure

  11. Eddy current techniques for super duplex stainless steel characterization

    Energy Technology Data Exchange (ETDEWEB)

    Camerini, C., E-mail: cgcamerini@metalmat.ufrj.br [Laboratory of Non-Destructive Testing, Corrosion and Welding, Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (Brazil); Sacramento, R.; Areiza, M.C.; Rocha, A. [Laboratory of Non-Destructive Testing, Corrosion and Welding, Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (Brazil); Santos, R. [PETROBRAS R& D Center, Rio de Janeiro (Brazil); Rebello, J.M.; Pereira, G. [Laboratory of Non-Destructive Testing, Corrosion and Welding, Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (Brazil)

    2015-08-15

    Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content. - Highlights: • Sigma phase precipitation, even for low amounts, dramatically affects SDSS properties. • SDSS samples were thermally treated and carefully characterized by X-Ray Diffraction. • NDT techniques detected low amounts of sigma phase in SDSS microstructure.

  12. Hydrogen-enhanced cracking of 2205 duplex stainless steel welds

    International Nuclear Information System (INIS)

    Slow-displacement rate tensile tests were carried out to investigate the effect of hydrogen embrittlement on notched tensile strength (NTS) and fracture characteristics of 2205 duplex stainless steel weld. The hydrogen embrittlement susceptibility of the specimens was correlated with microstructures of the fusion zone. The results indicated that all the specimens were susceptible to gaseous hydrogen embrittlement but to different degrees. The susceptibility decreased with increasing austenite content in the weld metal. The orientation with respect to the rolling direction had a great influence on the impact toughness of the base plate. Preheating before welding or changing the plasma-assisted gas from He to N2 could raise the γ content of the fusion zone and improve the impact toughness. In case of the post-weld heat-treated weld (PW), the presence of randomly oriented acicular and blocky γ in the fusion zone led to the highest impact energy and NTS among the specimens being tested. Scanning electron microscopy (SEM) fractographs revealed that all specimens underwent a significant change in fracture mode from ductile in air to quasi-cleavage fracture in H2

  13. Hot Forging of Nitrogen Alloyed Duplex Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    P.Chandramohan; S.S. Mohamed Nazirudeen; S.S. Ramakrishnan

    2007-01-01

    Duplex stainless steels are gaining global importance because of the need for a high strength corrosion resistant material. Three compositions of this group were selected with three different nitrogen contents viz, 0.15 wt pct (alloy 1), 0.23 wt pct (alloy 2) and 0.32 wt pct (alloy 3). The steels were melted in a high frequency induction furnace and hot forged to various reductions from 16% to 62%. In this work, the effect of hot forging on the ferrite content, hardness, yield strength, impact strength and grain orientation (texture) were studied. Fracture analysis on all the forged specimens using SEM reveals that a size reduction of 48% results in maximum ductility and impact strength as well as minimal ferrite content and grain size. Thus the mechanical properties are found to have a direct correlation to ferrite content and grain size. The highest impact strength was observed in specimens with the smallest grain size, which was observed in specimens forged to 48% reduction in size.

  14. Duplex stainless steel columns and beam-columns in case of fire

    OpenAIRE

    Lopes, N.; Vila Real, P. M. M.; Simoes da Silva, L.; Franssen, Jean-Marc

    2008-01-01

    It is the purpose of this paper to evaluate the accuracy and safety of the currently prescribed design rules in Eurocode 3: Part 1.2 for the evaluation of the resistance of duplex stainless steel columns and beam-columns. This evaluation is carried out by performing numerical simulations on Class1 and Class 2 stainless steel H-columns. These numerical simulations are performed using the program SAFIR. Eurocode 3 states that stainless steel structural members, subjected to high ...

  15. 475 °C Embrittlement in a duplex stainless steel UNS S31803

    Directory of Open Access Journals (Sweden)

    S.S.M. Tavares

    2001-10-01

    Full Text Available The susceptibility of a duplex stainless steel UNS S31803 to thermal embrittlement at 475 °C was evaluated by means of mechanical tests (impact energy and hardness, magnetic measurements (hysteresis and thermomagnetic analysis and scanning electron microscopy. The results show that the material undergoes severe embrittlement and hardening in the first 100 h. The corrosion resistance of the ferrite phase in a 10%HNO3 + 0.05%HF solution deteriorated after 500 h of ageing. The Curie temperature (Tc was the most sensitive magnetic property to the microstructural changes that promote embrittlement. Tc increases with ageing time due to the progressive reduction of chromium in the Fe-rich matrix during spinodal decomposition.

  16. Fracture resistance of cracked duplex stainless steel elbows under bending with or without internal pressure

    International Nuclear Information System (INIS)

    Electricite de France (EDF), in co-operation with Framatome, has conducted a large research programme on the fracture behaviour of aged cast duplex stainless steel elbows. One important task of this programme consisted of testing three large diameter (580 mm O.D.) thermally aged cast elbows containing either one or two semi-elliptical notches on the outer surface of the flank. The first two elbow tests (called SEM1 and SEM2) were conducted under in-plane closure bending at 320 C and the third one (called SEM3) under constant internal pressure and in-plane closure bending at 60 C. Those tests were carried out with 2/3-scale models of PWR primary loop elbows. This paper presents the results of the experiments and the results of the fracture mechanics analyses, based on finite element calculations. (orig.)

  17. Innovative PM duplex stainless steels obtained basing on the Schaeffler diagram

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2008-03-01

    Full Text Available Purpose: The purpose of this paper was to describe the sintered duplex stainless steels manufactured in sinterhardeningprocess and its usability in field of stainless steels and moreover using computer software to calculatethe powder mix composition.Design/methodology/approach: In presented paper duplex stainless steels were obtained through powdermetallurgy starting from austenitic or ferritic base powders by controlled addition of alloying elements powder. In thestudies besides the preparation of powder mixes, computer software based on Schaeffler’s diagram was studied.Findings: It has been demonstrated that austenitic-ferritic microstructures with regular arrangement of both phasesand absence of precipitates can be obtained with properly designed powder mix composition and sintering cycle.Research limitations/implications: According to the alloys characteristic applied cooling rate and powder mixcomposition seems to be a good compromise to obtain balanced duplex stainless steel microstructures, neverthelessfurther tests should be carried out in order to examine different cooling rates and sintering parameters.Practical implications: Applied producing method of sintered duplex steels and used sintering cycle as wellas developed computer software to calculating powder mix composition proves his advantage in case of obtainedmicrostructures and additionally it seem to be very promising for obtaining a balanced duplex structure, alsoworking with cycles easy to be introduced in industries.Originality/value: The utilization of sinter-hardening process combined with use of elemental powders addedto a stainless steel base powder shows its advantages in terms of good microstructural homogeneity and especiallyworking with cycles possible to introduce in industrial practice.

  18. Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method

    OpenAIRE

    Mehmet Emin Arikan; Rafet Arikan; Mustafa Doruk

    2012-01-01

    Specimens taken from a hot-rolled cylindrical duplex stainless steel (DSS) bar with 22% Cr grade were solution annealed at 1050∘C and then aged at 725∘C from 100 to 31622 min for sensitization treatment. Double loop electrochemical potentiodynamic reactivation and standard weight loss immersion acid tests were conducted. The solution-annealed samples were found unsensitized. Those samples aged for 100 and 316 min were less sensitized whereas samples aged for 1000 min and especially those aged...

  19. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by super duplex filler metal

    Energy Technology Data Exchange (ETDEWEB)

    Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shamanian, Morteza [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandarian, Masoomeh [Department of Materials Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Zabolian, Azam [Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Szpunar, Jerzy A. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9 (Canada)

    2015-08-15

    In the present paper, microstructural changes across an as-welded dissimilar austenitic/duplex stainless steel couple welded by a super duplex stainless steel filler metal using gas tungsten arc welding process is characterized with optical microscopy and electron back-scattered diffraction techniques. Accordingly, variations of microstructure, texture, and grain boundary character distribution of base metals, heat affected zones, and weld metal were investigated. The results showed that the weld metal, which was composed of Widmanstätten austenite side-plates and allotriomorphic grain boundary austenite morphologies, had the weakest texture and was dominated by low angle boundaries. The welding process increased the ferrite content but decreased the texture intensity at the heat affected zone of the super duplex stainless steel base metal. In addition, through partial ferritization, it changed the morphology of elongated grains of the rolled microstructure to twinned partially transformed austenite plateaus scattered between ferrite textured colonies. However, the texture of the austenitic stainless steel heat affected zone was strengthened via encouraging recrystallization and formation of annealing twins. At both interfaces, an increase in the special character coincident site lattice boundaries of the primary phase as well as a strong texture with <100> orientation, mainly of Goss component, was observed. - Graphical abstract: Display Omitted - Highlights: • Weld metal showed local orientation at microscale but random texture at macroscale. • Intensification of <100> orientated grains was observed adjacent to the fusion lines. • The austenite texture was weaker than that of the ferrite in all duplex regions. • Welding caused twinned partially transformed austenites to form at SDSS HAZ. • At both interfaces, the ratio of special CSL boundaries of the primary phase increased.

  20. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by super duplex filler metal

    International Nuclear Information System (INIS)

    In the present paper, microstructural changes across an as-welded dissimilar austenitic/duplex stainless steel couple welded by a super duplex stainless steel filler metal using gas tungsten arc welding process is characterized with optical microscopy and electron back-scattered diffraction techniques. Accordingly, variations of microstructure, texture, and grain boundary character distribution of base metals, heat affected zones, and weld metal were investigated. The results showed that the weld metal, which was composed of Widmanstätten austenite side-plates and allotriomorphic grain boundary austenite morphologies, had the weakest texture and was dominated by low angle boundaries. The welding process increased the ferrite content but decreased the texture intensity at the heat affected zone of the super duplex stainless steel base metal. In addition, through partial ferritization, it changed the morphology of elongated grains of the rolled microstructure to twinned partially transformed austenite plateaus scattered between ferrite textured colonies. However, the texture of the austenitic stainless steel heat affected zone was strengthened via encouraging recrystallization and formation of annealing twins. At both interfaces, an increase in the special character coincident site lattice boundaries of the primary phase as well as a strong texture with <100> orientation, mainly of Goss component, was observed. - Graphical abstract: Display Omitted - Highlights: • Weld metal showed local orientation at microscale but random texture at macroscale. • Intensification of <100> orientated grains was observed adjacent to the fusion lines. • The austenite texture was weaker than that of the ferrite in all duplex regions. • Welding caused twinned partially transformed austenites to form at SDSS HAZ. • At both interfaces, the ratio of special CSL boundaries of the primary phase increased

  1. Development of nano-structured duplex and ferritic stainless steels by pulverisette planetary milling followed by pressureless sintering

    International Nuclear Information System (INIS)

    Nano-structured duplex and ferritic stainless steel powders are prepared by planetary milling of elemental Fe, Cr and Ni powder for 40 h and then consolidated by conventional pressureless sintering. The progress of milling and the continuous refinement of stainless steel powders have been confirmed by means of X-ray diffraction and scanning electron microscopy. Activation energy for the formation of duplex and ferritic stainless steels is calculated by Kissinger method using differential scanning calorimetry and is found to be 159.24 and 90.17 KJ/mol respectively. Both duplex and ferritic stainless steel powders are consolidated at 1000, 1200 and 1400 °C in argon atmosphere to study microstructure, density and hardness. Maximum sintered density of 90% and Vickers microhardness of 550 HV are achieved for duplex stainless steel sintered at 1400 °C for 1 h. Similarly, 92% sintered density and 263 HV microhardness are achieved for ferritic stainless steel sintered at 1400 °C. - Highlights: • Synthesized duplex and ferritic stainless steels by pulverisette planetary milling • Calculated activation energy for the formation of duplex and ferritic stainless steels • Studied the effect of sintering temperature on density, hardness and microstructure • Duplex stainless steel exhibits 90% sintered density and microhardness of 550 HV. • Ferritic stainless steel shows 92% sintered density and 263 HV microhardness

  2. Development of nano-structured duplex and ferritic stainless steels by pulverisette planetary milling followed by pressureless sintering

    Energy Technology Data Exchange (ETDEWEB)

    R, Shashanka, E-mail: shashankaic@gmail.com; Chaira, D., E-mail: chaira.debasis@gmail.com

    2015-01-15

    Nano-structured duplex and ferritic stainless steel powders are prepared by planetary milling of elemental Fe, Cr and Ni powder for 40 h and then consolidated by conventional pressureless sintering. The progress of milling and the continuous refinement of stainless steel powders have been confirmed by means of X-ray diffraction and scanning electron microscopy. Activation energy for the formation of duplex and ferritic stainless steels is calculated by Kissinger method using differential scanning calorimetry and is found to be 159.24 and 90.17 KJ/mol respectively. Both duplex and ferritic stainless steel powders are consolidated at 1000, 1200 and 1400 °C in argon atmosphere to study microstructure, density and hardness. Maximum sintered density of 90% and Vickers microhardness of 550 HV are achieved for duplex stainless steel sintered at 1400 °C for 1 h. Similarly, 92% sintered density and 263 HV microhardness are achieved for ferritic stainless steel sintered at 1400 °C. - Highlights: • Synthesized duplex and ferritic stainless steels by pulverisette planetary milling • Calculated activation energy for the formation of duplex and ferritic stainless steels • Studied the effect of sintering temperature on density, hardness and microstructure • Duplex stainless steel exhibits 90% sintered density and microhardness of 550 HV. • Ferritic stainless steel shows 92% sintered density and 263 HV microhardness.

  3. Influence of nitrogen on the corrosion fatigue behaviour of duplex stainless steels

    International Nuclear Information System (INIS)

    Combining a well adapted morphological texture to obtain a wavy crack propagation front with the effect of nitrogen which promotes slip reversibility in the austenitic phase, one can improve the corrosion fatigue resistance of duplex stainless steels in NaCl solutions. These structural factors allows to decrease the detrimental effect of hydrogen on the corrosion fatigue behaviour of the duplex alloys at imposed cathodic potentials. (authors). 3 figs

  4. Corrosion behaviour of new duplex stainless steel reinforcements embedded in chloride contaminated concrete

    OpenAIRE

    Medina Sanchez, Eduardo; Cobo Escamilla, Alfonso; Martínez Bastidas, David

    2011-01-01

    The use of reinforcing stainless steels (SS) in concrete have proved to be one of the most effective methods to guarantee the passivity of reinforced concrete structures exposed to chloride contaminated environment. The present research studies the corrosion behaviour of a new duplex SS reinforcements with low nickel content (LND) (more economicaly compatible) is compared with the conventional austenitic AISI 304 SS and duplex AISI 2304 SS. Corrosion behaviour of ribbed SS reinforcement...

  5. Monte Carlo simulation of spinodal decomposition in a ternary alloy within a three-phases field: comparison to phase transformation of ferrite in duplex stainless steels

    International Nuclear Information System (INIS)

    Duplex stainless steels (DSS) are largely used for industrial purposes due to their good corrosion resistance, mechanical properties and also due to their ability to be cast. They are notably used as cast elbows in primary circuits of pressurized water reactors. However these steels are subject to ageing at service temperature (285 C degrees - 323 C degrees). This work proposes to model phase transformations occurring in duplex stainless steels using atomistic kinetic Monte Carlo in a ternary model alloy. Kinetics are simulated in the three-phase field of a ternary system. Influence of the precipitation of the third phase on the kinetic of spinodal decomposition between the two other phases is studied in order to understand the synergy between spinodal decomposition and G-phase precipitation which exists in duplex stainless steels. Simulation results are compared to experimental data obtained with atom probe tomography

  6. Final Report, Volume 3, Guidance Document for the Evaluation of Cast Super Duplex Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Hariharan, Vasudevan; Lundin, Carl, W.

    2005-09-30

    Volume 3 is comprised of the Development of Qualification Standards for Cast Super Duplex Stainless Steel (A890-5A) which is equivalent to wrought 2507. The objective of this work was to determine the suitability of ASTM A923 Standard Test methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic-Ferritic Stainless Steels for 25 Cr Cast Super Duplex Stainless Steels (ASTM A890-5A). The various tests which were carried out were ASTM A923 Test Method A, B and C (Sodium Hydroxide Etch Test, Charpy Impact Test and Ferric Chloride Corrosion Test), ferrite measurement using Feritscope®, ASTM E562 Manual Point Count Method and X-Ray Diffraction, hardness measurement using Rockwell B and C and microstructural analysis using SEM and EDS.

  7. Final Report, Volume 3, Guidance Document for the Evaluation of Cast Super Duplex Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Hariharan, Vasudevan; Lundin, Carl, D.

    2005-09-30

    Volume 3 comprises of the Development of Qualification Standards for Cast Super Duplex Stainless Steel (A890-5A) which is equivalent to wrought 2507. The objective of this work was to determine the suitability of ASTM A923 Standard Test methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic-Ferritic Stainless Steels for 25 Cr Cast Super Duplex Stainless Steels (ASTM A890-5A). The various tests which were carried out were ASTM A923 Test Method A, B and C (Sodium Hydroxide Etch Test, Charpy Impact Test and Ferric Chloride Corrosion Test), ferrite measurement using Feritscope{reg_sign}, ASTM E562 Manual Point Count Method and X-Ray Diffraction, hardness measurement using Rockwell B and C and microstructural analysis using SEM and EDS.

  8. Corrosion behaviors of duplex stainless steel for wet CO/sub 2/ environment

    International Nuclear Information System (INIS)

    Twenty-two ≅ 25%Cr α-γ duplex phase stainless steels are suitable for CO/sub 2/-brine system. The pitting resistance in the ferric chloride test at 300C is improved by means of regulating alloying elements both in a pitting index and a fraction of austenite phase. Concerning the duplex stainless steel, it is preferable to include the term of nitrogen content in the expression of pitting index, e.g. P.I. = Cr + 3Mo + 16N. By the newly developed welding materials, the pitting resistance of welds could be improved. Influence of H/sub 2/S and O/sub 2/ contamination on CO/sub 2/ corrosion of duplex stainless steels are discussed

  9. Functional surfaces on duplex stainless steel by lasercladding; Funktionale Oberflaechen auf Duplex-Stahl durch Laserfeinbeschichten

    Energy Technology Data Exchange (ETDEWEB)

    Dwars, A. [KSB Aktiengesellschaft, Pegnitz (Germany); Emmel, A. [FH-Amberg, Weiden (Germany)

    2008-08-15

    The product-lubricated axial and radial bearings installed in multistage high-pressure pumps inevitably encounter severe mixed friction conditions as the pumps start and stop. This leads to extremely high tribological loads on the bearing components, compounded by the effects of a highly corrosive pumped fluid. The present paper describes a laser cladding process which produces near-net-shape coatings of new, highly corrosion and wear resistant functional layers which can be deposited directly on high-alloy stainless steels without requiring additional buffer layers and without affecting the mechanical properties and corrosion resistance of the substrate. The results cover the solidification behaviour of the coatings as well as the microstructure resulting from various heat treatment conditions. In addition, the technological properties of the coatings and the resulting composites are discussed. The coating systems are tested as to their corrosion resistance and tribological characterization in a pump-specific tribological system. (Abstract Copyright [2008], Wiley Periodicals, Inc.) [German] Waehrend der An- und Abfahrvorgaenge mehrstufiger Hochdruckpumpen durchlaufen mediumgeschmierte Axial- und Radiallager unweigerlich einen stark ausgepraegten Mischreibungsbereich. Dies fuehrt zu einer extrem hohen tribologischen Belastung der Lagerkomponenten bei gleichzeitig hoher korrosiver Belastung durch das Foerdermedium. Der vorliegende Beitrag beschreibt einen Laserbeschichtungsprozess zur Erzeugung von hoch korrosions- und verschleissfesten sowie gleichzeitig tribologisch geeigneten Funktionsschichten, die ohne zusaetzliche Pufferung direkt auf hochlegierten Duplex-Staehlen aufgebracht werden koennen, ohne die Eigenschaften des Grundmaterials zu verschlechtern. Die dargestellten Ergebnisse umfassen sowohl das Erstarrungsverhalten der erzeugten Schichten, als auch die Grenzflaechen- und Gefuegeausbildung der entstehenden Werkstoffverbunde in Abhaengigkeit der moeglichen

  10. Corrosion behaviour of corrugated lean duplex stainless steels in simulated concrete pore solutions

    International Nuclear Information System (INIS)

    Research highlights: → Two new corrugated duplex grades have been studied as cheaper alternatives to 304. → 2304 is more corrosion-resistant than the austenitic 304, but less than duplex 2205. → 2001 has similar corrosion performance than the much more expensive 304. → In 2304, ferrite preferentially corrodes in all studied aggressive pore solutions. → In 2001 duplex, austenite shows lower corrosion resistance than ferrite. - Abstract: This work studies the corrosion behaviour of two corrugated lean duplex stainless steels (SAF 2001 and 2304 grades) in eight alkaline solutions (carbonated and non-carbonated, saturated Ca(OH)2 solutions with different chloride contents). 2001 stainless steel is a new grade in market because of its composition. 2304 is a grade previously studied under different conditions. However, its use as reinforcement in concrete is new. Studies are carried out by polarization curves following scanning electronic microscopy (SEM) and optical observations. Results are compared to those of carbon steel and austenitic AISI 304 and duplex SAF 2205 under similar conditions. After corrosion tests in alkaline media with chloride, ferrite tends to corrode selectively in 2304 duplex, while austenite corrodes selectively in 2001 under the same conditions. The influence of the duplex microstructure on attack development and morphology is analyzed. The electrochemical parameters obtained from the polarization curves suggest 2001 could replace 304 keeping the structure its corrosion performance (and with clear economical advantages). 2304 shows better corrosion behaviour than the more expensive 304, but somewhat lower than the excellent behaviour shown by 2205.

  11. Fatigue crack propagation behavior and acoustic emission characteristics of the heat affected zone of super duplex stainless steel

    International Nuclear Information System (INIS)

    Because duplex stainless steel shows the good strength and corrosion resistance properties, the necessity of duplex stainless steel, which has long life in severe environments, has been increased with industrial development. The fatigue crack propagation behavior of Heat Affected Zone(HAZ) has been investigated in super duplex stainless steel. The fatigue crack propagation rate of HAZ of super duplex stainless steel was faster than that of base metal of super duplex stainless steel. We also analysed acoustic emission signals during the fatigue test with time-frequency analysis method. According to the results of time-frequency analysis, the frequency ranges of 200-400 kHz were obtained by striation and the frequency range of 500 kHz was obtained due to dimple and separate of inclusion

  12. Influence Of Heat Treatment On Duplex Stainless Steel To Study The Material Properties

    Directory of Open Access Journals (Sweden)

    Jithin M

    2015-02-01

    Full Text Available Abstract The various heat treatment processes are annealing normalizing hardening tempering spheroidising surface hardening flame and induction hardening nitriding cyaniding carbonitriding carburizing etc Heat treatment on duplex stainless steel is to improve ductility toughness strength hardness and to relieve internal stress developed in the material. Here basically the experiment of hardness test impact test wear test and compression is done to get idea about heat treated duplex stainless steel which has extensive uses in all industries and scientific research and development fields.

  13. 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.

  14. Yield stress of duplex stainless steel specimens estimated using a compound Hall–Petch equation

    OpenAIRE

    Noriaki Hirota, Fuxing Yin, Tsukasa Azuma and Tadanobu Inoue

    2010-01-01

    In this study, the 0.2% yield stress of duplex stainless steel was evaluated using a compound Hall–Petch equation. The compound Hall–Petch equation was derived from four types of duplex stainless steel, which contained 0.2–64.4 wt% δ-ferrite phase, had different chemical compositions and were annealed at different temperatures. Intragranular yield stress was measured with an ultra-microhardness tester and evaluated with the yield stress model proposed by Dao et al. Grain size, volume fraction...

  15. Mechanical properties and microstructure of a commercial grade duplex stainless steel 2205

    International Nuclear Information System (INIS)

    Duplex stainless steels typically contain 50% austenite and 50% ferrite. The two phase mixture also leads to a marked refinement in grain size of both the austenite and ferrite. This, together with the presence of ferrite, makes material about twice as strong as common austenitic steels. They contain only about half the nickel concentration of typical austenitic stainless steels; they are therefore, less expensive and less sensitive to the price of nickel. With their high chromium concentration, they have excellent pitting and crevice corrosion resistance, and to chloride stress corrosion The two phase mixture also reduces the risk of inter granular attack; for the same reason they are not prone to solidification cracking during welding. The typical duplex stainless steel contain 22-23 Cr, 4.5-6.5 Ni, and 3-3.5 Mo wt%, representing some 80% of all duplex stainless steel use. In present work a horse grade duplex stainless steel 2205 in the form of seamless pipe has been studied. Material exhibited excellent mechanical properties in as-received condition and after welding. The bend test results obtained from root and face of the welded samples gave satisfactory results. To analyse the microstructure, light optical microscope was used before and after welding. (author)

  16. Aging degradation of cast stainless steel

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. Microstructures of cast materials subjected to long-term aging either in reactor service or in the laboratory have been characterized by TEM, SANS, and APFIM techniques. Two precipitate phases, i.e., the Cr-rich α' phase and the Ni- and Si-rich G phase, have been identified in the ferrite matrix of the aged steels. The results indicate that the low-temperature embrittlement is primarily caused by α' precipitates which form by spinodal decomposition. The relative contribution of the G phase to loss of toughness is now known. Microstructural data also indicate that weakening of the ferrite/austenite phase boundary by carbide precipitates has a significant effect on the onset and extent of embrittlement of the high-carbon CF-8 and CF-8M grades of stainless steels, particularly after aging at 400 or 4500C. Data from Charpy-impact, tensile, and J-R curve tests for several heats of cast stainless steel aged up to 10,000 h at 350, 400, and 4500C are presented and correlated with the microstructural results. Thermal aging of the steels results in an increase in tensile strength and a decrease in impact energy, J/sub IC/, and tearing modulus. The fracture toughness results show good agreement with the Charpy-impact data. The effects of compositional and metallurgical variables on loss of toughness are discussed

  17. Fracture micromechanisms and residual stresses of a highly resistant duplex stainless steel

    OpenAIRE

    Valiente Cancho, Andrés; Mihaela IORDACHESCU; Ruiz Hervías, Jesús; Abreu Rodrigues, Maricely de

    2013-01-01

    The paper presents some preliminary results of an ongoing research intended to qualify a highly resistant duplex stainless steel wire as prestressing steel and, gets on insight on (he wires' fracture micromechanism and residual stresses field. SEM fractographic analysis of the stainless steel wires indicates an anisotropic fracture behavior in tension, in presence of surface flaws, attributed to the residual stresses generated through the fabrication process. The residual stresses magnitude i...

  18. Examination of inclusion size distributions in duplex stainless steel using electrolytic extraction

    OpenAIRE

    Shoja Chaeikar, Siamak

    2010-01-01

    Nowadays due to large demand for clean and defect-free steels, several techniques based on different characteristics of particles are applied to investigate the steel cleanness. Outokumpu Stainless AB in Avesta has performed extensive work in this field by applying several methods, which all of them have specific advantages and limitations. However, it is necessary to find an accurate technique to investigate real properties of inclusions in duplex stainless steels. For routine analytical met...

  19. The influence of sintering time on the properties of PM duplex stainless steel

    Directory of Open Access Journals (Sweden)

    Z. Brytan

    2009-12-01

    Full Text Available Purpose: The purpose of this paper is to analyse the effect of sintering time on the pore morphology, microstructural changes, tensile properties and corrosion resistance of vacuum sintered duplex stainless steel.Design/methodology/approach: In presented study PM duplex stainless steels were obtained through mixing base ferritic stainless steel powder with controlled addition of elemental alloying powders and then sintered in a vacuum furnace with argon backfilling at 1250°C for different time periods. Produced materials were studied by LOM/SEM metallography and the pore morphology was characterized. The mechanical properties were studied in tensile, hardness and Charpy impact tests. The corrosion resistance was evaluated by means of salt spray test and immersion in sulfuric acid.Findings: Prolongation of sintering time influenced on increase of density thus on the mechanical properties and microstructure balance.Practical implications: Mechanical properties of obtained PM duplex stainless steels are very promising, especially with the aim of extending their field of possible applications.Originality/value: The possibility of obtaining balanced austenitic-ferritic microstructure of stainless steel using elemental powders added to a stainless steel base powder. The vacuum sintering of such powder mixture results in good microstructural homogeneity.

  20. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    This progress report summarizes work performed by Argonne National Laboratory on longterm thermal embrittlement of cast duplex stainless steels in LWR systems during the six months from October 1989 to March 1990. The results from Charpy-impact tests and microhardness measurements of the ferrite phase for several heats of cast stainless steel aged up to 30,000 h at 290--400 degree C are analyzed to establish the kinetics of thermal embrittlement. Correlations are presented for predicting the extent and kinetics of thermal embrittlement of cast stainless steels from material information that can be determined from the certified material test record. The extent of embrittlement is characterized by the room-temperature ''normalized'' Charpy-impact energy. Based on the information available, two methods are presented for estimating the extent of embrittlement at ''saturation,'' i.e., the minimum impact energy that would be achieved for the material after long-term aging. The first method utilizes only the chemical composition of the steel. The second method is used when metallographic information on the ferrite morphology, i.e., measured values of ferrite content and mean ferrite spacing of the steel, is also available. The change in Charpy-impact energy as a function of time and temperature of reactor service is then estimated from the extent of embrittlement at saturation and from the correlations describing the kinetics of embrittlement, which is expressed in terms of the chemical composition and aging behavior of the steel at 400 degree C. 37 refs., 16 figs., 4 tabs

  1. Heat treatment temperature influence on ASTM A890 GR 6A super duplex stainless steel microstructure

    International Nuclear Information System (INIS)

    Duplex and super duplex stainless steels are ferrous alloys with up to 26% chromium, 8% nickel, 5% molybdenum and 0.3% nitrogen, which are largely used in applications in media containing ions from the halogen family, mainly the chloride ion (Cl-). The emergence of this material aimed at substituting Copper-Nickel alloys (Cupro-Nickel) that despite presenting good corrosion resistance, has mechanical properties quite inferior to steel properties. The metallurgy of duplex and super duplex stainless steel is complex due to high sensitiveness to sigma phase precipitation that becomes apparent, due to the temperatures they are exposed on cooling from solidification as well as from heat treatment processes. The objective of this study was to verify the influence of heat treating temperatures on the microstructure and hardness of ASTM A890/A890M Gr 6A super duplex stainless steel type. Microstructure control is of extreme importance for castings, as the chemical composition and cooling during solidification inevitably provide conditions for precipitation of sigma phase. Higher hardness in these materials is directly associated to high sigma phase concentration in the microstructure, precipitated in the ferrite/austenite interface. While heat treatment temperature during solution treatment increases, the sigma phase content in the microstructure decreases and consequently, the material hardness diminishes. When the sigma phase was completely dissolved by the heat treatment, the material hardness was influenced only due to ferrite and austenite contents in the microstructure

  2. Characterization of duplex stainless steel weld metals obtained by hybrid plasma-gas metal arc welding

    Directory of Open Access Journals (Sweden)

    Koray Yurtisik

    2013-09-01

    Full Text Available Despite its high efficiency, autogenous keyhole welding is not well-accepted for duplex stainless steels because it causes excessive ferrite in as-welded duplex microstructure, which leads to a degradation in toughness and corrosion properties of the material. Combining the deep penetration characteristics of plasma arc welding in keyhole mode and metal deposition capability of gas metal arc welding, hybrid plasma - gas metal arc welding process has considered for providing a proper duplex microstructure without compromising the welding efficiency. 11.1 mm-thick standard duplex stainless steel plates were joined in a single-pass using this novel technique. Same plates were also subjected to conventional gas metal arc and plasma arc welding processes, providing benchmarks for the investigation of the weldability of the material. In the first place, the hybrid welding process enabled us to achieve less heat input compared to gas metal arc welding. Consequently, the precipitation of secondary phases, which are known to be detrimental to the toughness and corrosion resistance of duplex stainless steels, was significantly suppressed in both fusion and heat affected zones. Secondly, contrary to other keyhole techniques, proper cooling time and weld metal chemistry were achieved during the process, facilitating sufficient reconstructive transformation of austenite in the ferrite phase.

  3. TEM study of dislocations in duplex stainless steel: Študija dislokacij v dupleksnem nerjavnem jeklu s presevno elektronsko mikroskopijo:

    OpenAIRE

    Jenko, Darja; JENKO, Monika; Mandziej, Stan T.; Šuštaršič, Borivoj; Toffolon-Masclet, Caroline

    2014-01-01

    Specimens of duplex stainless steel (DSS, the 258-alloy type) were isothermally annealed (aged) at 300 °C and 350 °C for 10000 h and 30000 h. Spinodal decomposition of the solid solution in ferrite occurs during the thermal ageing of this material with a redistribution of mainly Cr and Ni and a formation of nanocellular domains. This causes significant changes in the mechanical properties (the hardness and the tensile strength increase, while the ductility and the notch toughness decrease). T...

  4. Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method

    OpenAIRE

    ARIKAN, Mehmet Emin; DORUK, Mustafa

    2008-01-01

    Specimens taken from a hot rolled cylindrical duplex stainless steel (DSS) bar with 22% Cr and 5% Ni grade were solution annealed at 1050 °C and then sensitization heat treatments were conducted at 650 °C. A series of specimens with ageing times ranging from 100 to 31,622 min were held for sensitization treatment. The effects of isothermal ageing treatments on the microstructure and on the localized corrosion resistance of the DSS were investigated, through the double loop electrochemi...

  5. INFLUENCE OF COLD WORK ON SIGMA PHASE FORMATION IN DUPLEX STAINLESS STEEL

    Directory of Open Access Journals (Sweden)

    Rodrigo Magnabosco

    2012-09-01

    Full Text Available The formation of sigma phase in duplex stainless steels during isothermal aging is widely reported in the literature, but the influence of strain hardening prior to aging on the kinetics of formation of this phase was not a subject of systematic studies so far. The objective of this paper is to study the influence of cold work degree and aging time in aging at 650°C or 850°C of an UNS S31803 steel. Cold rolling was conducted, resulting in four sets of samples with 0%, 10%, 30% or 80% cross sectional area reduction. Those samples were submitted to isothermal aging between 10 minutes and 96 hours, followed by water quenching. Sigma phase quantification is possible after selective electrolytic etching with 10% KOH solution, and the volume fraction of ferrite is obtained with the aid of ferritscope. It is observed that increasing the strain hardening increases the possibility of heterogeneous nucleation of sigma phase within the ferrite grains, leading to increased rate of formation of sigma and consumption of ferrite with increasing aging time at both temperatures studied.

  6. Yield stress of duplex stainless steel specimens estimated using a compound Hall–Petch equation

    Directory of Open Access Journals (Sweden)

    Noriaki Hirota, Fuxing Yin, Tsukasa Azuma and Tadanobu Inoue

    2010-01-01

    Full Text Available In this study, the 0.2% yield stress of duplex stainless steel was evaluated using a compound Hall–Petch equation. The compound Hall–Petch equation was derived from four types of duplex stainless steel, which contained 0.2–64.4 wt% δ-ferrite phase, had different chemical compositions and were annealed at different temperatures. Intragranular yield stress was measured with an ultra-microhardness tester and evaluated with the yield stress model proposed by Dao et al. Grain size, volume fraction and texture were monitored by electron backscattering diffraction measurement. The kγ constant in the compound equation for duplex stainless steel agrees well with that for γ-phase SUS316L steel in the temperature range of 1323–1473 K. The derived compound Hall–Petch equation predicts that the yield stress will be in good agreement with the experimental results for the Cr, Mn, Si, Ni and N solid-solution states. We find that the intragranular yield stress of the δ-phase of duplex stainless steel is rather sensitive to the chemical composition and annealing conditions, which is attributed to the size misfit parameter.

  7. Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation

    Directory of Open Access Journals (Sweden)

    Seul-Kee Kim

    2015-09-01

    Full Text Available Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior.

  8. Investigation of Selected Surface Integrity Features of Duplex Stainless Steel (DSS) after Turning

    Czech Academy of Sciences Publication Activity Database

    Krolczyk, G.; Nieslony, P.; Legutko, S.; Hloch, Sergej; Samardžić, I.

    2015-01-01

    Roč. 54, č. 1 (2015), s. 91-94. ISSN 0543-5846 Institutional support: RVO:68145535 Keywords : duplex stainless steel * machining * turning * surface integrity * surface roughness Subject RIV: JQ - Machines ; Tools Impact factor: 0.959, year: 2014 http://hrcak.srce.hr/126702

  9. Effect of welding processes on corrosion resistance of UNS S31803 duplex stainless steel

    International Nuclear Information System (INIS)

    An attractive combination of corrosion resistance and mechanical properties in the temperature range -50 to 250 .deg. C is offered by duplex stainless steel. However, undesirable secondary precipitation phase such as σ, γ2 and Cr2N may taken place at the cooling stage from the welding processes. Therefore, this paper describes the influence of different welding procedures such as manual metal arc welding (MMA), tungsten inert gas welding (TIG) and vacuum brazing on corrosion resistance of the welded joint for UNS S31803 duplex stainless steel. Microstructure and chemical compositions of the welded joint were examined. The weight loss of specimens immersed in 6% FeCl3 solution at 47.5 .deg. C for 24-hours was determined and used to evaluate the pitting resistance of duplex stainless steel and their welds. The region of heat-affected zone of specimen obtained by the MMA is much wider than that resulted from TIG, therefore, the weight loss of welds by MMA was larger than that of weld by TIG. The weight loss of brazed specimens cooled from slow cooling rate was larger than those of specimens cooled from high cooling rate, because the precipitation of σ phase. Beside that, the weight loss of brazed specimen is greater than those of the welded specimens. The galvanic corrosion was observed in brazed duplex stainless steel joints in the chloride solution

  10. Beneficial Effect of Microalloyed Rare Earth on S Segregation in High-Purity Duplex Stainless Steel

    Science.gov (United States)

    Chen, Lei; Ma, Xiaocong; Jin, Miao; Wang, Jianfeng; Long, Hongjun; Mao, Tianqiao

    2016-01-01

    S segregation at the α/ γ interface remains in duplex stainless steel with only 10 ppm S. The interfacial brittle tearing appears during hot deformation due to S segregation. Minor rare earth additions can effectively eliminate the S contamination. In particular, RE enrichment at the α/ γ interface indicating its microalloying effect is an important cause.

  11. Yield stress of duplex stainless steel specimens estimated using a compound Hall-Petch equation

    International Nuclear Information System (INIS)

    In this study, the 0.2% yield stress of duplex stainless steel was evaluated using a compound Hall-Petch equation. The compound Hall-Petch equation was derived from four types of duplex stainless steel, which contained 0.2-64.4 wt% δ-ferrite phase, had different chemical compositions and were annealed at different temperatures. Intragranular yield stress was measured with an ultra-microhardness tester and evaluated with the yield stress model proposed by Dao et al. Grain size, volume fraction and texture were monitored by electron backscattering diffraction measurement. The kγ constant in the compound equation for duplex stainless steel agrees well with that for γ-phase SUS316L steel in the temperature range of 1323-1473 K. The derived compound Hall-Petch equation predicts that the yield stress will be in good agreement with the experimental results for the Cr, Mn, Si, Ni and N solid-solution states. We find that the intragranular yield stress of the δ-phase of duplex stainless steel is rather sensitive to the chemical composition and annealing conditions, which is attributed to the size misfit parameter.

  12. Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation

    OpenAIRE

    Seul-Kee Kim; Ki-Yeob Kang; Myung-Soo Kim; Jae-Myung Lee

    2015-01-01

    Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS) because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior.

  13. Final Report, Volume 1, Metallurgical Evaluation of Cast Duplex Stainless Steels and their Weldments

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Songqing; Lundin, Carl, W.; Batten, Greg, W.

    2005-09-30

    Duplex stainless steels (DSS) are being specified for chloride containing environments due to their enhanced pitting and stress corrosion cracking resistance. They exhibit improved corrosion performance over the austenitic stainless steels. Duplex stainless steels also offer improved strength properties and are available in various wrought and cast forms. Selected grades of duplex stainless steel castings and their welds, in comparison with their wrought counterparts, were evaluated, regarding corrosion performance and mechanical properties and weldability. Multiple heats of cast duplex stainless steel were evaluated in the as-cast, solution annealed (SA) static cast and SA centrifugal cast conditions, while their wrought counterparts were characterized in the SA condition and in the form of as-rolled plate. Welding, including extensive assessment of autogenous welds and a preliminary study of composite welds (shielded metal arc weld (SMAW)), was performed. The evaluations included critical pitting temperature (CPT) testing, intergranular corrosion (IGC) testing, ASTM A923 (Methods A, B and C), Charpy impact testing, weldability testing (ASTM A494), ferrite measurement and microstructural evaluations. In the study, the corrosion performances of DSS castings were characterized and assessed, including the wrought counterparts for comparison. The evaluation filled the pore of lack of data for cast duplex stainless steels compared to wrought materials. A database of the pitting corrosion and IGC behavior of cast and wrought materials was generated for a greater depth of understanding for the behavior of cast duplex stainless steel. In addition, improved evaluation methods for DSS castings were developed according to ASTM A923, A262, G48 and A494. The study revealed that when properly heat treated according to the specification, (1) DSS castings have equal or better pitting and intergranular corrosion resistance than their wrought counterparts; (2) Welding reduces the

  14. Final Report, Volume 1, Metallurgical Evaluation of Cast Duplex Stainless Steels and their Weldments

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Songqing; Lundin, Carl, W.; Batten, Greg, W.

    2005-09-30

    Duplex stainless steels (DSS) are being specified for chloride containing environments due to their enhanced pitting and stress corrosion cracking resistance. They exhibit improved corrosion performance over the austenitic stainless steels. Duplex stainless steels also offer improved strength properties and are available in various wrought and cast forms. Selected grades of duplex stainless steel castings and their welds, in comparison with their wrought counterparts, were evaluated, regarding corrosion performance and mechanical properties and weldability. Multiple heats of cast duplex stainless steel were evaluated in the as-cast, solution annealed (SA) static cast and SA centrifugal cast conditions, while their wrought counterparts were characterized in the SA condition and in the form of as-rolled plate. Welding, including extensive assessment of autogenous welds and a preliminary study of composite welds (shielded metal arc weld (SMAW)), was performed. The evaluations included critical pitting temperature (CPT) testing, intergranular corrosion (IGC) testing, ASTM A923 (Methods A, B and C), Charpy impact testing, weldability testing (ASTM A494), ferrite measurement and microstructural evaluations. In the study, the corrosion performances of DSS castings were characterized and assessed, including the wrought counterparts for comparison. The evaluation filled the pore of lack of data for cast duplex stainless steels compared to wrought materials. A database of the pitting corrosion and IGC behavior of cast and wrought materials was generated for a greater depth of understanding for the behavior of cast duplex stainless steel. In addition, improved evaluation methods for DSS castings were developed according to ASTM A923, A262, G48 and A494. The study revealed that when properly heat treated according to the specification, (1) DSS castings have equal or better pitting and intergranular corrosion resistance than their wrought counterparts; (2) Welding reduces the

  15. Effect of Deleterious Phases on Corrosion Resistance of Duplex Stainless Steel (2205

    Directory of Open Access Journals (Sweden)

    AbdulKadar M. Godil

    2013-07-01

    Full Text Available Duplex stainless steel is a Ferritic(BCC-Austenitic(FCC steel, covers the advantages of both Austenitic and Ferritic Stainless steels. They having good mechanical and corrosion resistance properties are widely used in many industries like chemical plants, refineries for critical equipments such as pressure vessels, heatexchangers, water heaters. Major problem occurs with duplex steels when they are worked or heated above about temperature of 280°C. Detrimental phases like Sigma, Chi, Laves and Alpha prime form when the Duplex steels are treated above this temperature and they retard the properties of Duplex stainless steels. They also cause embrittlement above temperature of 475°C called “475°C embrittlement”. During welding of duplex steels, Secondary austenite also forms, which is also one of the harmful phases in duplex steels. Among all of these phases, Sigma (σ is extremely harmful to the corrosion resistance of steel. Due to these limitations duplexgrades are not used above certain temperature ranges. In this experimental work a plate of duplex grade 2205 in hot worked condition was procured from TCR Advanced Engineering Pvt. Ltd., GIDC, Vadodara. Initially chemical composition of the plate was checked with emission spectrometer, tensile test and hardness tests werecarried out for comparing with the standard data. As there was no Sigma phase detected when tested with ASTM 930 in the received sample, Sigma phase was intentionally produced by giving heat treatment in the range of 700-850°C. Sigma phases were quantified with ASTM 930 practice A, by electrolytic etching with 40% NaOH. The effect of Sigma phase on corrosion resistance was measured by ASTM G48. The pitting corrosion resistance was evaluated in terms of average pit depth and overall corrosion rate.

  16. Electrochemical Behavior of 2205 Duplex Stainless Steel in NaCl Solution with Different Chromate Contents

    Science.gov (United States)

    Luo, H.; Dong, C. F.; Cheng, X. Q.; Xiao, K.; Li, X. G.

    2012-07-01

    The electrochemical behavior of 2205 duplex stainless steel in NaCl solution with different chromate contents were investigated by potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, and scanning electron microscope (SEM). The effect of chromate on passivity and pitting behavior of stainless steel was also studied. The results showed that pitting susceptibility as well as semiconducting properties of passive film is heavily dependent on the chromate concentration. There exists a critical chromate value (about 0.03 M in 1 M NaCl solutions) below which the pitting corrosion on the stainless steel would be inhibited and above which it would be accelerated.

  17. Duplex stainless steels. A review after DSS '07 held in Grado

    Energy Technology Data Exchange (ETDEWEB)

    Charles, J. [ARCELOR MITTAL, La Plaine Saint-Denis (France)

    2008-06-15

    Duplex stainless have always been an exiting area of interest for researchers, stainless steel producers, fabricators and end users. They present very diversified technical challenges and simultaneously attractive in-service properties at excellent cost/properties ratios, particularly in critical markets including oil and gas, chemical industry, pulp and paper industry, water systems, desalination plants, pollution control equipments, chemical tankers, etc. This explains why although they still remain a marginal production in the stainless steel business (less than 1%) dedicated international conferences have been organised since about 25 years. The purpose of this paper is to present a review of the 100 scientific contributions presented during the latest international duplex stainless steel conference witch took place in Grado, Italy, on 18-20 June 2007. The main topics concerned microstructure and mechanical properties, weldability, corrosion resistance and in-service properties. The ''standard'' duplex stainless steels, i.e. the 2304, 2205, and the family of 2507 (Cu,W,..) grades were confirmed as very valuable grades with outstanding performances proven in more than 20 years successful in-service applications. New grades including the so-called lean duplex dedicated to volume oriented markets (possible replacement of 304/316 grades) and some ''niche'' grades dedicated to very specific markets were presented. It was pointed out that the duplex grades start to be well established products particularly suitable for corrosion resistance applications. They show a two-digit yearly growth thanks to the production of new grades and production ranges (coils and bars) targeting the replacement of the more costly 300 series including 304 but also rusty carbon steel in e.g. structural application. (orig.)

  18. Hydrogen embrittlement of duplex stainless steel Z2CND2205 hydrogen charged at 200 deg C

    International Nuclear Information System (INIS)

    Ageing the duplex stainless steel below 500 deg. C, the main and usually phenomenon is the unmixing of the δ-FeCr solid solution by spinodal decomposition (or precipitation of α-Cr at higher temperatures). Various intermetallics are detected such as fine disperses (Ni, Si, Mo-rich)G-phase. At higher ageing temperatures (between 600 deg. C and 1050 deg. C), a variety of secondary phases may form, such as γ2, σ, R, χ and Π. The precipitation of carbides M23C6, M7C2 and Cr2N are also detected.This paper is devoted to study the interactions between hydrogen atoms and these phases in a 2205 duplex steel. Hydrogenation had been achieved at 200 deg. C and 1050 deg. C in a molten salts bath, during 3 hours (tempering time also) with an applied cathodic potential equal to - 1.5 V/Ag/AgCl. After hydrogen charging, samples have been out-gassed under vacuum at 600 deg. C to measure the quantity of hydrogen QH. The ageing temperature was varied between 200 deg. C. The hydrogen embrittlement factor was determined by performing 10-6 S-1 tensile tests at room temperature. The results show that the variation of U.T.S. is sensitive to the microstructure change in absence and in presence of hydrogen. The relationship between λ(U.T.S.Hyd/U.T.S.Air) and QH is linear; λ is low (i.e. high embrittlement) in presence of σ phase with low QH level, while, in presence of the other phases, even with high QH, σ is relatively high (low embrittlement). (author). 7 refs., 4 figs

  19. Influence of sigma-phase formation on the localized corrosion behavior of a duplex stainless steel

    Science.gov (United States)

    Adhe, K. M.; Kain, V.; Madangopal, K.; Gadiyar, H. S.

    1996-08-01

    Because of their austenitic-ferritic microstructures, duplex stainless steels offer a good combination of mechanical and corrosion resistance properties. However, heat treatments can lower the mechanical strength of these stainless steels as well as render them susceptible to intergranular corrosion (IGC) and pitting corrosion. In this study, a low-carbon (0.02%) duplex stainless steel is subjected to various heat treatments at 450 to 950 °C for 30 min to 10 h. The heat-treated samples then undergo ASTM IGC and pitting corrosion tests, and the results are correlated with the microstructures obtained after each heat treatment. In the absence of Cr23C6 precipitation, σ-phase precipitates render this duplex stainless steel susceptible to IGC and pitting corrosion. Even submicroscopic σ-phase precipitates are deleterious for IGC resistance. Longer-duration heat treatments (at 750 to 850 °C) induce chromium diffusion to replenish the chromium-depleted regions around the σ-phase precipitates and improve IGC resistance; pitting resistance, however, is not fully restored. Various mechanisms of σ-phase formation are discussed to show that regions adjacent to σ-phase are depleted of chromium and molybdenum. The effect of chemical composition (pitting resistance equivalent) on the pitting resistance of various stainless steels is also noted.

  20. Influence of sigma-phase formation on the localized corrosion behavior of a duplex stainless steel

    International Nuclear Information System (INIS)

    Because of their austenitic-ferritic microstructures, duplex stainless steels offer a good combination of mechanical and corrosion resistance properties. However, heat treatments can lower the mechanical strength of these stainless steels as well as render them susceptible to intergranular corrosion (IGC) and pitting corrosion. In this study, a low-carbon (0.02%) duplex stainless steel is subjected to various heat treatments at 450 to 950 C for 30 min to 10 h. The heat-treated samples than undergo ASTM IGC and pitting corrosion tests, and the results are correlated with the microstructures obtained after each heat treatment. In the absence of Cr23C6 precipitation, σ-phase precipitates render this duplex stainless steel susceptible to IGC and pitting corrosion. Even submicroscopic σ-phase precipitates are deleterious for IGC resistance. Longer-duration heat treatments (at 750 to 850 C) induce chromium diffusion to replenish the chromium-depleted regions around the σ-phase precipitates and improve IGC resistance; pitting resistance, however, is not fully restored. Various mechanisms of σ-phase formation are discussed to show that regions adjacent to σ-phase are depleted of chromium and molybdenum. The effect of chemical composition (pitting resistance equivalent) on the pitting resistance of various stainless steels is also noted

  1. Experimental Study of the Thermal Diffusivity and Heat Capacity Concerning Some Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Riad Harwill Abdul Abas

    2015-06-01

    Full Text Available In the present work, thermal diffusivity and heat capacity measurements have been investigated in temperature range between RT and 1473 K for different duplex stainless steel supplied by Outokumpu Stainless AB, Sweden. The purpose of this study is to get a reliable thermophysical data of these alloys and to study the effect of microstructure on the thermal diffusivity and heat capacity value. Results show the ferrite content in the duplex stainless steel increased with temperature at equilibrium state. On the other hand, ferrite content increased with increasing Cr/Ni ratio and there is no significant effect of ferrite content on the thermal diffusivity value at room temperature. Furthermore, the heat capacity of all samples increases with temperature from room temperature to 473 K, while it decreases with increasing temperature until 1073 K. Then it increases with temperature at higher temperature. Curie temperature and sigma phase formation temperature can be detected by heat capacity-temperature curves.

  2. Corrosion studies of austenitic and duplex stainless steels in aqueous lithium bromide solution at different temperatures

    International Nuclear Information System (INIS)

    The corrosion behavior of three stainless steels EN 14311, EN 14429 (austenitic stainless steels) and EN 14462 (duplex stainless steel) was studied in a commercial LiBr solution (850 g/l LiBr solution containing chromate as inhibitor) at different temperatures (25, 50, 75 and 85 deg C) by electrochemical methods. Open circuit potentials shifted towards more active values as temperature increased, while corrosion potentials presented the opposite tendency. The most resistant alloys to general corrosion were EN 14429 and EN 14462 because they had the lowest corrosion current for all temperatures. In all the cases corrosion current increases with temperature. Pitting corrosion resistance is improved by the EN 14462, which presented the highest pitting potential, and the lowest passivation current for the whole range of temperatures studied. The duplex alloy also presents the worst repassivation behavior (in terms of the narrowest difference between corrosion potential and pitting potential); it does not repassivate from 50 deg C

  3. Crack propagation during fatigue in cast duplex stainless steels: influence of the microstructure, of the aging and of the test temperature; Propagation de fissure par fatigue dans les aciers austeno-ferritiques moules: influence de la microstructure, du vieillissement et de la temperature d'essai

    Energy Technology Data Exchange (ETDEWEB)

    Calonne, V

    2001-07-15

    Duplex stainless steels are used as cast components in nuclear power plants. At the service temperature of about 320 C, the ferrite phase is thermally aged and embrittled. This induces a significant decrease in fracture properties of these materials. The aim of this work consists in studying Fatigue Crack Growth Rates (FCGR) and Fatigue Crack Growth Mechanisms (FCGM) as a function of thermal ageing and test temperature (20 C/320 C). Two cast duplex stainless steels (30% ferrite) are tested. In order to better understand the influence of the crystallographic orientation of the phases on the FCGM, the solidification structure of the material is studied by Electron Back-Scatter Diffraction (EBSD) and by Unidirectional Solidification Quenching. Fatigue crack growth tests are also performed in equiaxed and basaltic structures. Microstructure, fatigue crack growth mechanical properties and mechanisms are thus studied in relation to each other. In the studied range of delta K, the crack propagates without any preferential path by successive ruptures of phase laths. The macroscopic crack propagation plane, as determined by EBSD, depends on the crystallographic orientation of the ferrite grain. So, according to the solidification structure, secondary cracks can appear, which in turn influences the FCGR. Fatigue crack closure, which has to be determined to estimate the intrinsic FCGR, decreases with increasing ageing. This can be explained by a decrease in the kinematic cyclic hardening. The Paris exponent as determined from intrinsic FCGR increases with ageing. Intrinsic FCGR can then be separated in two ranges: one with lower FCGR in aged materials than in un-aged and one with the reversed tendency. (author)

  4. Transformation and Precipitation Kinetics in 30Cr10Ni Duplex Stainless Steel

    Science.gov (United States)

    Fazarinc, Matevz; Terčelj, Milan; Bombač, David; Kugler, Goran

    2010-09-01

    To improve the microstructure during casting, hot forming, and heat treatment of 30Cr10Ni duplex stainless steel, accurate data on the precipitation and transformation processes at high temperatures are needed. In this article, the precipitation and transformation processes at various aging times in the temperature range 873 K to 1573 K (600 °C to 1300 °C) were studied. The 30Cr10Ni ferrous alloy contains a relatively large amount of Cr, Ni, and C, which results in a complex microstructure. In addition to the ferrite, austenite, and sigma phase, the M23C6 and MC carbides were also observed in the microstructure. The precipitation of the sigma phase was observed after just 3 minutes of aging, and after 30 minutes of aging at approximately 1053 K (780 °C), its fraction exceeded 40 pct. An intensive austenite-to-ferrite transformation was observed above 1423 K (1150 °C). Optical microscopy, energy-dispersive X-ray spectroscopy (EDS), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD), as well as micro-indentation hardness, hardness, impact toughness, and tensile tests, were carried out to evaluate the obtained microstructures of aged samples.

  5. Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method: A Comparative Study

    OpenAIRE

    Mehmet Emin Arıkan; Rafet Arıkan; Mustafa Doruk

    2012-01-01

    In the present study as in our previous studies (Arikan and Doruk, 2008 and Arikan et al., 2012), similar specimens taken from a hot rolled cylindrical duplex stainless steel (DSS) bar with 22% Cr grade were solution annealed at 1050°C and then aged at 800∘C from 100 to 31622 min for sensitization treatment. Double loop electrochemical potentiodynamic reactivation and standard weight loss immersion acid tests were conducted. The solution annealed samples were found unsensitized. The samples a...

  6. Use of a gray level co-occurrence matrix to characterize duplex stainless steel phases microstructure

    OpenAIRE

    L. Zortea; F. R. Renzetti

    2011-01-01

    Duplex stainless steels are widely used in industry. This is due to their higher strength compared to austenitic steels and to their higher toughness than ferritic steels. They also have good weldability and high resistance to stress corrosion cracking.These steels are characterized by two-phase microstructures composed by almost the same level of ferrite and austenite.Duplex steel 2205 samples evaluated are: as received, cold rolled (33%) and heat-treated at 800°C for 10 hours.A metallograph...

  7. 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

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

    Science.gov (United States)

    Fujii, K.; Fukuya, K.

    2013-09-01

    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.

  9. Laser Shock Processing with Different Conditions of Treatment on Duplex Stainless Steel

    Science.gov (United States)

    Castañeda, E.; Rubio-Gonzalez, C.; Chavez-Chavez, A.; Gomez-Rosas, G.

    2015-06-01

    The laser shock processing (LSP) has been developed as an effective alternative to traditional methods for improvement of metallic materials properties and as surface treatment to metals. Duplex stainless steel is a material that has a microstructure formed by two phases, with approximately equal amounts of each one. This stainless steel has wide applications in different fields like shipping, petrochemical, and chemical industries. We present results of the LSP performance using two pulse density configurations of 2500 and 5000 pulses/cm2, both of them at laser irradiation of 532 and 1064 nm (keeping approximately constant power density), in order to treat in under water-jet the surface of 2205 duplex stainless steel samples without coating. A flat mirror and a converging lens is used to deliver 400 mJ/pulse, (5 ns FWHM, 1.1 mm spot diameter with 532 nm wavelength) and 850 mJ/pulse, (6 ns FWHM, 1.5 mm spot diameter with 1064 nm wavelength) laser pulse produced by 10 Hz Q-switched Nd:YAG laser. A motor-controlled x-y precision stage is used, for sweep the treated zone on sample. The use of two wavelengths with approximately the same power density is an effective way for obtaining high compressive residual stresses (~90% of the yield stress). An improvement of hardness (12-25%) at the surface of 2205 duplex stainless steel due to LSP is presented.

  10. NDE evaluation of the intergranular corrosion susceptibility of a 2205 duplex stainless steel using thermoelectric power and double loop electrochemical potentiokinetic reactivation methods

    Science.gov (United States)

    Ortiz, N.; Carreón, H.; Ruiz, A.

    2013-01-01

    There is a need for a nondestructive technique to assess rapidly and with confidence the degree of sensitization (DOS) in duplex stainless steel (DSS). In this investigation, we present the use of thermoelectric power (TEP) measurements as nondestructive method for the determination of DOS in isothermally aged 2205 DSS at 700°C for different aging times. The DOS of the aged samples was first established by performing the double loop electrochemical potentiokinetic reactivation (DL-EPR) test. The microstructural evolution was evaluated by scanning electron microscopy (SEM). Experimental results indicate that TEP coefficient is sensitive to gradual microstructural changes produced by thermal aging and can be used to monitor IGC sensitization of 2205 duplex stainless steel.

  11. CHARACTERIZATION OF MICROSTRUCTURE AND DETERMINATION OF ELASTIC PROPERTIES IN SAF 2205 DUPLEX STAINLESS STEEL USING ULTRASONIC MEASUREMENTS

    OpenAIRE

    R. Jayachitra*

    2016-01-01

    Microstructural changes in duplex stainless steel due to changes in annealing temperature are characterized by ultrasonic pulse-echo technique and optical microscopy.  Duplex stainless steel was subjected to a series of heat treatments from 1100°C to 1350°C, followed by water quenching.  The microstructure after heat treatment at 1350°C resulted in coarse grained ferrite, which favored formation of Widmanstatan austenite with fast cooling.  Micro hardness and optica...

  12. Direct observation and quantification of nanoscale spinodal decomposition in super duplex stainless steel weld metals.

    Science.gov (United States)

    Shariq, Ahmed; Hättestrand, Mats; Nilsson, Jan-Olof; Gregori, Andrea

    2009-06-01

    Three variants of super duplex stainless steel weld metals with the basic composition 29Cr-8Ni-2Mo (wt%) were investigated. The nitrogen content of the three materials was 0.22%, 0.33% and 0.37%, respectively. Isothermal heat treatments were performed at 450 degrees C for times up to 243 h. The hardness evolution of the three materials was found to vary with the overall concentration of the nitrogen. Atom probe field ion microscopy (APFIM) was used to directly detect and quantify the degree of spinodal decomposition in different material conditions. 3-DAP atomic reconstruction clearly illustrate nanoscale variation of iron rich (alpha) and chromium rich (alpha') phases. A longer ageing time produces a coarser microstructure with larger alpha and alpha' domains. Statistical evaluation of APFIM data showed that phase separation was significant already after 1 h of ageing that gradually became more pronounced. Although nanoscale concentration variation was evident, no significant influence of overall nitrogen content on the degree of spinodal decomposition was found. PMID:19504899

  13. Aging degradation of cast stainless steel: status and program

    International Nuclear Information System (INIS)

    A program has been initiated to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. The existing data are reviewed to determine the critical parameters that control the aging behavior and to define the objectives and scope of the investigation. The test matrices for microstructural studies and mechanical property measurements are presented. The initial experimental effort is focussed on characterizing the microstructure of long-term, low-temperature aged material. Specimens from three heats of cast CF-8 and CF-8M stainless steel aged for up to 70,000 h at 300, 350, and 4000C were obtained from George Fisher Ltd., of Switzerland. Initial analyses reveal the formation of three different types of precipitates which are not α'. An FCC phase, similar to the M23C6 precipitates, was present in all the long-term aged material. 15 references, 10 figures, 2 tables

  14. A study on phase stress of centrifugally cast duplex stainless steel by neutron diffraction

    International Nuclear Information System (INIS)

    With great corrosion resistance and mechanical property, ferrite-austenitic duplex stainless steel have been applied to components in corrosive environments such as sea water pumps. Due to different coefficients of thermal expansion and elastic modulus between the two phases, phase stress occurs after heat treatment or material processing such as casting, forging and machining, which may affect material properties such as fatigue strength, welding stability and so on. In this study, phase stress distribution along thickness direction of duplex stainless steel hollow cylinders fabricated by centrifugal casting was measured by pulsed neutron diffraction using time-of-flight (TOF) method. Also lattice strain and phase stress evolution were discussed by in-situ neutron diffraction measurement during tensile test. All these measurements were conducted at Japan Proton Accelerator Research Complex (J-PARC). (author)

  15. In vitro biocompatibility of duplex stainless steel with and without 0.2% niobium.

    Science.gov (United States)

    Beloti, M M; Rollo, J M D A; Itman Filho, A; Rosa, A L

    2004-01-01

    Stainless steel is frequently used as a biomaterial. Chemical composition alterations can be undertaken to improve its mechanical and biological properties. This investigation aimed to compare the biocompatibility of duplex stainless steel, with and without 0.2% niobium, with austenitic stainless steel and titanium-6-aluminium-4-vanadium (Ti6Al4V) using rat bone marrow (RBM) cell culture. Cell attachment was evaluated at 24 hr. Cell proliferation, cell viability, total protein content, and alkaline phosphatase (ALP) activity were evaluated at 7, 14 and 21 days. Bone-like nodule formation was evaluated at 21 days. Cell attachment, proliferation and viability were unaffected by the chemical composition of the stainless steels and the Ti6Al4V. Total protein content, ALP activity, and bone-like nodule formation were unaffected by the chemical composition of the stainless steels, but these parameters were greater on the Ti6Al4V than on the stainless steels. Our results demonstrated that initial cell events were unaffected by the chemical composition of the tested alloys, while events indicating osteoblast differentiation including increased ALP activity and bone-like nodule formation were favored by the Ti6Al4V. Moreover, the evaluated parameters were unaffected by the presence of niobium in the stainless steel composition. As niobium affects microstructure and, consequently, improves the mechanical properties of duplex stainless steel, it is suggested that the addition of niobium to metallic alloys could be useful in developing alloys with acceptable biocompatibility and improved mechanical features. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 162-8). PMID:20803434

  16. Long-term embrittlement of cast duplex stainless steels in LWR systems. Annual report, October 1983-September 1984

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. The existing data are evaluated to determine the expected embrittlement of cast components during the operating lifetime of reactors and to define the objectives and scope of the investigation. Data for the metallurgical characterization of the various cast stainless steels used in the investigation are presented. Charpy impact tests on short-term aged material indicate that CF-3 stainless steels are less susceptible to embrittlement than CF-8 or CF-8M stainless steels. Embrittlement of the ferrite phase is primarily due to pinning of the dislocations by two of these precipitates, designed as Type M and Type X. The ferrite phase is embrittled after approx.8 yr at 3000C and shows cleavage fracture. Examination of the fracture surfaces of the impact-test specimens indicates that the toughness of the long-term aged material is determined by the austenite phase. 5 refs., 7 figs., 6 tabs

  17. Multiobjective optimization of friction welding of UNS S32205 duplex stainless steel

    OpenAIRE

    P.M. Ajith; Birendra Kumar Barik; P. Sathiya; S. Aravindan

    2015-01-01

    The present study is to optimize the process parameters for friction welding of duplex stainless steel (DSS UNS S32205). Experiments were conducted according to central composite design. Process variables, as inputs of the neural network, included friction pressure, upsetting pressure, speed and burn-off length. Tensile strength and microhardness were selected as the outputs of the neural networks. The weld metals had higher hardness and tensile strength than the base material due to grain re...

  18. Hot ductility of austenitic and duplex stainless steels under hot rolling conditions

    OpenAIRE

    Kömi, J. (Jenni)

    2001-01-01

    Abstract The effects of restoration and certain elements, nitrogen, sulphur, calcium and Misch metal, on the hot ductility of austenitic, high-alloyed austenitic and duplex stainless steels have been investigated by means of hot rolling, hot tensile, hot bending and stress relaxation tests. The results of these different testing methods indicated that hot rolling experiments using stepped specimens is the most effective way to investigate the relationship between the s...

  19. Micro-scale strain distribution in hot-worked duplex stainless steel

    OpenAIRE

    Hernandez-Castillo, L. E.; Beynon, J. H.; Pinna, C.; van der Zwaag, S.

    2005-01-01

    A modified microgrid technique has been applied to a laboratory-made duplex stainless steel, to experimentally simulate the local state of deformation of the austenite-ferrite microstructure of low-alloy steels subject to intercritical deformation. A sample containing such a microgrid was deformed by plane strain compression at high temperature under conditions representative of hot rolling processes. The distortion of the microgrid after hot deformation revealed, in a quantifiable manner, th...

  20. Corrosion failure of duplex stainless steel equipment in a PVC plant

    Energy Technology Data Exchange (ETDEWEB)

    Davies, M.; Potgieter, G.

    2000-05-01

    After <9 months of operation in a polyvinyl chloride (PVC) manufacturing plant, alloy 2205 duplex stainless steel (UNS 31803) columns and spiral heat exchangers (HXs) were corroding and cracking. The columns were repaired and remained in service but the HXs needed to be replaced. Candidate materials for the HXs were assessed, and it was found that the super-austenitic alloys containing 6% molybdenum would be more appropriate for this application.

  1. Microbiologically Influenced Corrosion of 2707 Hyper-Duplex Stainless Steel by Marine Pseudomonas aeruginosa Biofilm

    OpenAIRE

    Huabing Li; Enze Zhou; Dawei Zhang; Dake Xu; Jin Xia; Chunguang Yang; Hao Feng; Zhouhua Jiang; Xiaogang Li; Tingyue Gu; Ke Yang

    2016-01-01

    Microbiologically Influenced Corrosion (MIC) is a serious problem in many industries because it causes huge economic losses. Due to its excellent resistance to chemical corrosion, 2707 hyper duplex stainless steel (2707 HDSS) has been used in the marine environment. However, its resistance to MIC was not experimentally proven. In this study, the MIC behavior of 2707 HDSS caused by the marine aerobe Pseudomonas aeruginosa was investigated. Electrochemical analyses demonstrated a positive shift...

  2. Corrosion Behavior of Duplex Stainless Steels in Acidic-Chloride Solutions Studied with Micrometer Resolution

    OpenAIRE

    Femenia, Marc

    2003-01-01

    The local corrosion behavior of duplex stainless steel (DSS)is affected by a wide variety of factors. Localized corrosionof DSS frequently starts at micrometer scale inclusions orprecipitates, which are often segregated in theaustenite-ferrite boundary regions. Moreover, due to thepartitioning of the key alloying elements of ferrite (Cr andMo) and austenite (N and Ni), the local interactions betweenthe phases must also be considered. The aim of this doctoral study was to increase the knowledg...

  3. Eddy Current Transducer Dedicated for Sigma Phase Evaluation in Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Grzegorz Psuj

    2012-01-01

    Full Text Available The paper describes a new transducer dedicated for evaluation of a duplex stainless steel (DSS. Different phases which exist in DSS have influence on mechanical as well as on electrical properties. Therefore, an eddy current transducer was utilized. In order to achieve high sensitivity, a differential type of the transducer was selected. The performance of the transducer was verified by utilizing the samples which had a different amount of sigma phase.

  4. Ultrasonic Characterization And Micro-Structural Studies On 2205 Duplex Stainless Steel In Thermal Variations

    OpenAIRE

    Bernice Victoria; Dr. Gene George; Kevin Ark Kumar

    2015-01-01

    Abstract Due to increasing concern on potential impact of materials on human health and environment the materials used in hygienic applications should be durable corrosion resistant clean surface etc. Type 2205 duplex stainless steel is a preferred material for use in biomedical pharmaceutical nuclear pressure vessels chemical tankers etc. it exhibits good mechanical strength and high resistance to corrosion. The strength toughness hardness of such materials are usually determined by destruct...

  5. Effect of thermal treatments on the wear behaviour of duplex stainless steels

    OpenAIRE

    Fargas Ribas, Gemma; Mestra Rodríguez, Álvaro Miguel; Anglada Gomila, Marcos Juan; Mateo García, Antonio Manuel

    2009-01-01

    Duplex stainless steel (DSS) is a family of steels characterized by two-phase microstructure with similar percentages of ferrite (α) and austenite (y).Their attractive combination of mechanical properties and corrosion resistance has increased its use in last decades in the marine and petrochemical industries. Nevertheless, an inappropriate heat treatment can induce the precipitation of secondary phases which affect directly their mechanical properties and corrosion resistance....

  6. Dislocation structures of duplex stainless steel in uniaxial and biaxial cyclic loading

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Aubin, V.; Polák, Jaroslav; Degallaix, S.

    2005-01-01

    Roč. 482, - (2005), s. 179-182. ISSN 0255-5476. [Materials Structure and Micromechanics of Fracture. Brno, 23.06.2004-25.06.2004] R&D Projects: GA AV ČR(CZ) IAA2041201; GA AV ČR(CZ) IBS2041001 Keywords : Dislocation structure * Cyclic loading * Duplex stainless steel Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.399, year: 2005

  7. Experimental Analysis by Measurement of Surface Roughness Variations in Turning Process of Duplex Stainless Steel

    OpenAIRE

    Krolczyk Grzegorz M.; Legutko Stanisław

    2014-01-01

    The objective of the investigation was to identify surface roughness after turning with wedges of coated sintered carbide. The investigation included predicting the average surface roughness in the dry machining of Duplex Stainless Steel (DSS) and the determination of load curves together with roughness profiles for various cutting conditions. The load curves and roughness profiles for various cutting wedges and variable cutting parameters were compared. It has been shown that dry cutting lea...

  8. Investigation of the physical parameters of duplex stainless steel (DSS surface integrity after turning

    Directory of Open Access Journals (Sweden)

    G. Krolczyk

    2015-01-01

    Full Text Available The article presents the influence of machining parameters on the microhardness of surface integrity (SI after turning by means of a coated sintered carbide wedge with a coating with ceramic intermediate layer. The investigation comprised the influence of cutting speed on the SI microhardness in dry machining. The material under investigation was duplex stainless steel with two-phase ferritic-austenitic structure. The results obtained allow for conclusions concerning the exploitation features of processed machine parts.

  9. Investigation of selected surface integrity features of duplex stainless steel (DSS) after turning

    OpenAIRE

    G. Krolczyk; Nieslony, P.; S. Legutko; S. Hloch; I. Samardzic

    2015-01-01

    The article presents surface roughness profiles and Abbott - Firestone curves with vertical and amplitude parameters of surface roughness after turning by means of a coated sintered carbide wedge with a coating with ceramic intermediate layer. The investigation comprised the influence of cutting speed on the selected features of surface integrity in dry machining. The material under investigation was. duplex stainless steel with two-phase ferritic-austenitic structure. The tests have been per...

  10. Eddy Current Transducer Dedicated for Sigma Phase Evaluation in Duplex Stainless Steel

    OpenAIRE

    Tomasz Chady; Grzegorz Psuj; Cesar Giron Camerini

    2012-01-01

    The paper describes a new transducer dedicated for evaluation of a duplex stainless steel (DSS). Different phases which exist in DSS have influence on mechanical as well as on electrical properties. Therefore, an eddy current transducer was utilized. In order to achieve high sensitivity, a differential type of the transducer was selected. The performance of the transducer was verified by utilizing the samples which had a different amount of sigma phase.

  11. Microhardness changes gradient of the duplex stainless steel (DSS) surface layer after dry turning

    OpenAIRE

    G. Krolczyk; Nieslony, P.; S. Legutko; A. Stoic

    2014-01-01

    The article presents the gradient of microhardness changes as a function of the distance from the material surface after turning with a wedge provided with a coating with a ceramic intermediate layer. The investigation comprised the influence of cutting speed on surface integrity microhardness in dry machining. The tested material was duplex stainless steel (DSS) with two-phase, ferritic-austenitic structure. The tests have been performed under production conditions during machining of parts ...

  12. Investigations Into Surface Integrity in the Turning Process of Duplex Stainless Steel

    OpenAIRE

    Krolczyk, Grzegorz; Legutko, Stanislaw

    2014-01-01

    The objective of the investigation was to identify surface roughness and surface topography parameters after the turning of Duplex Stainless Steel (DSS) with wedges of coated sintered carbide. The auto correlation and gradient distributions for variable cutting parameters were compared. An Infinite Focus Measurement Machine (IFM) was used for the surface texture analysis. The study was performed within a production facility during the machining of electric motor parts and deep-well pumps.

  13. Investigation of the physical parameters of duplex stainless steel (DSS) surface integrity after turning

    OpenAIRE

    G. Krolczyk; Nieslony, P.; S. Legutko; I. Samardzic

    2015-01-01

    The article presents the influence of machining parameters on the microhardness of surface integrity (SI) after turning by means of a coated sintered carbide wedge with a coating with ceramic intermediate layer. The investigation comprised the influence of cutting speed on the SI microhardness in dry machining. The material under investigation was duplex stainless steel with two-phase ferritic-austenitic structure. The results obtained allow for conclusions concerning the exploitation feature...

  14. Stress-strain Relationship of Cold-formed Lean Duplex Stainless Steel at Elevated Temperatures

    OpenAIRE

    Young, B; Huang, Y.

    2014-01-01

    A test programme to examine the material properties of a relatively new cold-formed lean duplex stainless steel at elevated temperatures is presented. A total of 80 tensile coupon tests were carried out by both steady state test method and transient state test method for temperatures ranged from 24 to 900 °C. The coupons were extracted from square and rectangular hollow sections. Material properties including thermal elongation, Young's modulus, yield strength, ultimate strength and ultimate ...

  15. Ultrasonic Characterization And Micro-Structural Studies On 2205 Duplex Stainless Steel In Thermal Variations

    Directory of Open Access Journals (Sweden)

    Bernice Victoria

    2015-08-01

    Full Text Available Abstract Due to increasing concern on potential impact of materials on human health and environment the materials used in hygienic applications should be durable corrosion resistant clean surface etc. Type 2205 duplex stainless steel is a preferred material for use in biomedical pharmaceutical nuclear pressure vessels chemical tankers etc. it exhibits good mechanical strength and high resistance to corrosion. The strength toughness hardness of such materials are usually determined by destructive tests. However continuous destructive measurements are generally difficult to perform during the productive process which creates a need for a fast and easy nondestructive method of material characterization. Microstructural changes in duplex stainless steel due to changes in annealing temperature are characterized by ultrasonic pulse echo technique and optical microscopy. Type 2205 duplex stainless steel are heat treated at 1000 deg C 1050 deg C 1100 deg C 1150 deg C and 1200 deg C for 15 min and water quenched. There is an appreciable change in the morphology of all the heat treated samples and the ultrasonic velocity is dependent on both ferrite and austenite ratio and the grain size.

  16. A hyper duplex stainless steel developed for oil and gas industry

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Guocai; Kivisaekk, Ulf; Novak, Pavel [Sandvik Materials Technology (Sweden). R and D Centre; Finzetto, Leandro [Sandvik Materials Technology, Clarks Summit, PA (United States); Tokaruk, John [Sandvik Materials Technology (Norway)

    2008-07-01

    Subsea umbilical is operating under the sea as a connection between a platform's control station and the wells on the seabed to supply necessary control and chemicals to subsea oil and gas wells. The umbilical tube materials are required to have excellent corrosion resistance and high fatigue properties. The recent development and exploration in deep waters require the umbilicals with a length longer than 2500 meters. This indicates that the present umbilical tube can be so thick that they could not bear their own weight. Some new material will be needed. Another development is that some umbilicals will be used in high temperature sea water. With this background, Sandvik SAF 3207 HD has been newly developed. This paper gives an introduction of this new material. This new duplex stainless steel grade has a PRE number close to 50, which is therefore called hyper-duplex stainless steel. Sandvik SAF 3207 HD shows a yield strength 20% higher than those of super-duplex stainless steels, high fatigue properties, a service temperature up to 90 deg C and a good weldability. The benefits with this material when it comes to building umbilicals are considerable. Thinner walls and lighter installations make it possible to reach and operate ultra-deep wells that were previously too costly or too complex to exploit. At the same time, the temperature and pressure window widens - despite the thinner walls. (author)

  17. Intergranular corrosion behaviour of powder metallurgy duplex stainless steels sintered in nitrogen

    International Nuclear Information System (INIS)

    The degree of sensitization of duplex stainless steels, steels obtained through powder metallurgy (PM) technology from austenitic AISI 316L and ferritic AISI 430L were examined by exposure methods (ASTM A 763-93, Practice W and Practice Z) and electrochemical reactivation methods (EPR and EPRDL). Three austenite/ferrite ratios of 50/50, 65/75 and 85/25 and two sintering atmospheres, nitrogen-hydrogen (95 %/ 5%) and vacuum, were chosen. The former sintering atmosphere was the focus of the work and the latter was used on comparative basis. The aim of this work is to study the influence of austenite-ferrite powders and the sintering atmosphere on the degree of sensitization. The intergranular corrosion resistance increased when the amount of austenitic powder increased. It was also seen how the nitrogen played a relevant role in the degree of sensitization. The high degree of sensitization registered for samples sintered in nitrogen prevent its use in as-sintered condition and suggests the need of post-sintered heat treatments. The beneficial effect of annealing solution heat treatment on corrosion behaviour was established and was compared with corrosion behaviour of duplex stainless steels sintered in vacuum. The results were correlated with the microstructural features. Furthermore, it was found that the electrochemical reactivation methods applied to PM duplex stainless steels were suitable to evaluate the degree of sensitization. (authors)

  18. Phase Transformations During the Low-Temperature Nitriding of AISI 2205 Duplex Stainless Steel

    Science.gov (United States)

    Yan, Jing; Gu, Tan; Qiu, Shaoyu; Wang, Jun; Xiong, Ji; Fan, Hongyuan

    2015-02-01

    Liquid nitriding of type AISI 2205 duplex stainless steel was conducted at 723 K (450 °C), using one type of novel low-temperature liquid chemical thermo-treatment. The transformation of the nitrided surface microstructure was systematically studied. Experimental results revealed that a nitrided layer formed on the sample surface with the thickness ranging from 3 to 28 μm, depending on nitriding time. After the 2205 duplex stainless steel was subjected to liquid nitriding 723 K (450 °C) for less than 8 hours, the pre-existing ferrite region on the surface transformed into the expanded austenite (S phase) by the infusion of nitrogen atoms, most of which stay in the interstitial sites. Generally, the dominant phase of the nitrided layer was the expanded austenite. When the nitriding time prolonged up to 16 hours, some pre-existing ferrite in expanded austenite was decomposed and ɛ-nitride precipitated subsequently. When the treatment time went up to 40 hours, large amount of ɛ-nitride and CrN precipitates were observed in the pre-existing ferritic region in the expanded austenite. Furthermore, many nitrides precipitated from the pre-austenite region. Acicular nitride was identified by transmission electron microscopy. The thickness of the nitrided layer increased with increasing nitriding time. The growth of the nitrided layer is mainly due to nitrogen diffusion in accordance with the expected parabolic rate law. Liquid nitriding effectively increased the surface hardness of 2205 duplex stainless steel by a factor of 3.

  19. Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method: A Comparative Study

    Directory of Open Access Journals (Sweden)

    Mehmet Emin Arıkan

    2012-01-01

    Full Text Available In the present study as in our previous studies (Arikan and Doruk, 2008 and Arikan et al., 2012, similar specimens taken from a hot rolled cylindrical duplex stainless steel (DSS bar with 22% Cr grade were solution annealed at 1050°C and then aged at 800∘C from 100 to 31622 min for sensitization treatment. Double loop electrochemical potentiodynamic reactivation and standard weight loss immersion acid tests were conducted. The solution annealed samples were found unsensitized. The samples aged for 100 min were less sensitized whereas samples aged for 316 min and more time were sensitized. The degree of sensitization (DOS can be attributed to higher contribution of chromium and molybdenum depleted areas that result from intermetallic phases. However, especially the samples aged from 3162 to 31622 min have revealed chromium replenishment. Consequently, the degree of sensitization was lowered in comparison to the results obtained in previous studies.

  20. Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method

    Directory of Open Access Journals (Sweden)

    Mehmet Emin Arıkan

    2012-01-01

    Full Text Available Specimens taken from a hot-rolled cylindrical duplex stainless steel (DSS bar with 22% Cr grade were solution annealed at 1050∘C and then aged at 725∘C from 100 to 31622 min for sensitization treatment. Double loop electrochemical potentiodynamic reactivation and standard weight loss immersion acid tests were conducted. The solution-annealed samples were found unsensitized. Those samples aged for 100 and 316 min were less sensitized whereas samples aged for 1000 min and especially those aged for 3162, 10000, and 31622 min were heavily sensitized. The degree of sensitization (DOS can be attributed to higher contribution of chromium- and molybdenum-depleted areas resulting from intermetallic phases.

  1. Effect of nitrogen content on the environmentally-assisted cracking susceptibility of duplex stainless steels

    Science.gov (United States)

    Tseng, Chuan-Ming; Tsai, Wen-Ta; Liou, Horng-Yih

    2003-01-01

    The effect of nitrogen content on the stress corrosion cracking (SCC) behavior of 22 pct Cr duplex stainless steel (DSS) in chloride solutions was investigated in this study. Slow strain rate testing (SSRT) was employed to evaluate the SCC susceptibility. The experimental results showed that the tensile strength and ductility of 22 pct Cr DSS increased with increasing amount of nitrogen (in the range of 0.103 to 0.195 wt pct). Slow strain rate testing results indicated that 22 pct Cr DSSs were resistant to SCC in 3.5 wt pct NaCl solution at 80 °C. However, environmentally assisted cracking occurred in 40 wt pct CaCl2 solution at 100 °C and in boiling 45 wt pct MgCl2 solution at 155 °C, respectively. The effects of environment and nitrogen content in DSS on the cracking susceptibility are discussed in this article. Selective dissolution of ferrite phase was found to participate in the SCC process for tests in CaCl2 solution. At temperatures above 80 °C, dynamic strain aging was found to occur in various environments at a strain beyond plastic deformation.

  2. Intragranular Chromium Nitride Precipitates in Duplex and Superduplex Stainless Steel

    OpenAIRE

    Iversen, Torunn Hjulstad

    2012-01-01

    Intragranular chromium nitrides is a phenomenon with detrimental effects on material properties in superduplex stainless steels which have not received much attention. Precipitation of nitrides occurs when the ferritic phase becomes supersaturated with nitrogen and there is insufficient time during cooling for diffusion of nitrogen into austenite. Heat treatment was carried out at between 1060◦C and 1160◦C to study the materials susceptibility to nitride precipitation with...

  3. Materials Integrity Analysis for Application of Hyper Duplex Stainless Steels to Korean Nuclear Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hyun Young; Park, Heung Bae [Korea Power Engineering Company INC, Yongin (Korea, Republic of); Park, Yong Soo; Kim, Soon Tae [Yonsei University, Seoul (Korea, Republic of); Kim, Young Sik [Andong National University, Andong (Korea, Republic of); Kim, Kwang Tae [POSCO, Pohang (Korea, Republic of); Jhang, Yoon Young [ANSCO, Daejeon (Korea, Republic of)

    2010-10-15

    Hyper duplex stainless steels have been developed in Korea for the purpose of application to the seawater system of Korean nuclear power plants. This system supplies seawater to cooling water heat exchanger tubes, related pipes and chlorine injection system. In normal operation, seawater is supplied to heat exchanger through the exit of circulating water pump headers, and the heat exchanged sea water is extracted to the discharge pipes in circulating water system connected to the circulating water discharge lines. The high flow velocity of some part of seawater system in nuclear power plants accelerates damages of components. Therefore, high strength and high corrosion resistant steels need to be applied for this environment. Hyper duplex stainless steel (27Cr-7.0Ni-2.5Mo-3.2W-0.35N) has been newly developed in Korea and is being improved for applying to nuclear power plants. In this study, the physical and mechanical properties and corrosion resistance of newly developed materials are quantitatively evaluated in comparative to commercial stainless steels in other countries. The properties of weld and HAZ (heat affected zone) are analyzed and the best compositions are suggested. The optimum conditions in welding process are derived for ensuring the volume fraction of ferrite({alpha}) and austenite({gamma}) in HAZ and controlling weld cracks. For applying these materials to the seawater heat exchanger, CCT and CPT in weldments are measured. As a result of all experiments, it was found that the newly developed hyper duplex stainless steel WREMBA has higher corrosion resistance and mechanical properties than those of super austenitic stainless steels including welded area. It is expected to be a promising material for seawater systems of Korean nuclear power plants.

  4. Materials Integrity Analysis for Application of Hyper Duplex Stainless Steels to Korean Nuclear Power Plants

    International Nuclear Information System (INIS)

    Hyper duplex stainless steels have been developed in Korea for the purpose of application to the seawater system of Korean nuclear power plants. This system supplies seawater to cooling water heat exchanger tubes, related pipes and chlorine injection system. In normal operation, seawater is supplied to heat exchanger through the exit of circulating water pump headers, and the heat exchanged sea water is extracted to the discharge pipes in circulating water system connected to the circulating water discharge lines. The high flow velocity of some part of seawater system in nuclear power plants accelerates damages of components. Therefore, high strength and high corrosion resistant steels need to be applied for this environment. Hyper duplex stainless steel (27Cr-7.0Ni-2.5Mo-3.2W-0.35N) has been newly developed in Korea and is being improved for applying to nuclear power plants. In this study, the physical and mechanical properties and corrosion resistance of newly developed materials are quantitatively evaluated in comparative to commercial stainless steels in other countries. The properties of weld and HAZ (heat affected zone) are analyzed and the best compositions are suggested. The optimum conditions in welding process are derived for ensuring the volume fraction of ferrite(α) and austenite(γ) in HAZ and controlling weld cracks. For applying these materials to the seawater heat exchanger, CCT and CPT in weldments are measured. As a result of all experiments, it was found that the newly developed hyper duplex stainless steel WREMBA has higher corrosion resistance and mechanical properties than those of super austenitic stainless steels including welded area. It is expected to be a promising material for seawater systems of Korean nuclear power plants

  5. Experimental study and Monte Carlo simulations of phase transformations in ferrite of duplex stainless steels and their model alloys

    International Nuclear Information System (INIS)

    Duplex stainless steels used in primary circuit of 2. generation nuclear power plant endure thermal ageing at service temperatures (285 C-323 C). This leads to an increase of their hardness and to a decrease of their Charpy toughness. The evolution of these properties is due to the phase transformations which occur in ferrite. Even if it is well known that the steel composition plays a role on the mechanical properties evolution (steels with low Ni and Mo contents are less sensitive to thermal ageing), the origin of this difference of behaviour has not been clearly identified yet. In this study, the kinetics of the phase transformations in the ferrite of a duplex stainless steel with low Ni and Mo contents and duplex model alloys with specific compositions have been studied by atom probe tomography.This work showed that: i) G phase precipitation is less intense and the kinetic of the spinodal decomposition is slower for this steel than for steels with higher Ni and Mo contents, ii) the synergy between spinodal decomposition and G phase precipitation is also observed in this steel, iii) the Mo does not affect the early stages of the G phase precipitation, iv) the formation mechanism of G phase precipitates is at least a two steps mechanism, v) when the number density of G phase precipitates is low, hardening is mainly controlled by the amplitude and the mean wavelength of the spinodal decomposition, vi) when the number density of G phase precipitates is high, the hardening due to G phase precipitates may not be negligible. A kinetic Monte Carlo model has been developed to explain the synergy observed experimentally between the spinodal decomposition and the G phase precipitation. This model allowed us to show that the coarsening of G phase precipitates is driven by a diffusion mechanism along a/a' interfaces, and not by a bulk diffusion mechanism. (author)

  6. Evaluation of the low corrosion resistant phase formed during the sigma phase precipitation in duplex stainless steels

    Directory of Open Access Journals (Sweden)

    Kobayashi Darlene Yuko

    1999-01-01

    Full Text Available The duplex stainless steels, having a volumetric fraction of 50% ferrite and 50% austenite, conciliate high corrosion resistance with good mechanical properties. But, in many circumstances different phase transformations may occur, such as that responsible for sigma phase precipitation, which make the steel susceptible to localized corrosion. During the sigma phase precipitation a new austenitic phase is formed with a very low corrosion resistance. In the present research the composition of this new austenitic phase was evaluated in four duplex stainless steels, with different Mo, N and Cu contents. After the solution anneal at 1050 °C, samples of these steels were aged at 850 °C during 1 h and 5 h for sigma phase precipitation. Using the ferritoscope and an image analyzer it was possible to determine the volumetric fractions of ferrite and sigma phase, respectively, while those of austenite and the new austenitic phase were determined by difference to 100% volume. Finally, by using mass balance it was possible to determine theoretically the composition of the new austenitic phase. This phase is poor in Cr and Mo free, which explains its poor corrosion resistance.

  7. Detection of secondary phases in duplex stainless steel by magnetic force microscopy and scanning Kelvin probe force microscopy

    International Nuclear Information System (INIS)

    The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a “ghosted” effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: • Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. • As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. • AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA

  8. Development of a duplex cast stainless steel for nuclear purposes

    International Nuclear Information System (INIS)

    The starting material was a Finnish austenitic-ferritic stainless steel belonging to the family of widely used CF 308 M cast steels. This original HKS steel failed in the Strauss tests, which are of primary importance for materials used in nuclear power piles. Development work on lowering the ferrite and interstitial impurity contents influenced the properties of the steel so much that it no longer failed the Strauss test nor showed any brittleness when tested after irradiation treatment. Welded samples also showed no brittleness, provided the welding was carried out using correct filler materials and suitable heat input. (author)

  9. Passivation of duplex stainless steel in solutions simulating chloride-contaminated concrete

    Directory of Open Access Journals (Sweden)

    Takenouti, H.

    2007-12-01

    Full Text Available Most studies published to date on the corrosion behaviour of stainless reinforcing steel are based on austenitic steel. The market presence of corrugated duplex steel is growing, however. The present study compared passivity in 2205 type duplex and 304 type austenitic stainless steel. Polarization tests in chloride-containing Ca(OH2 solutions confirmed the exceptional performance of duplex steels. X-ray photoelectronic spectroscopy (XPS showed that the passive layer generated on duplex stainless steel in media simulating concrete pore solutions had a higher Cr content than the layer formed on steel in contact with the air. The XPS results also revealed that in duplex steel the form adopted by the passive layer Fe oxides was Fe3O4 in the solutions simulating concrete, rather than Fe2O3, as in duplex steel exposed to air. Electrochemical impedance spectroscopy (EIS can be used to monitor the transformations taking place in the passive layer and analyze the factors involved.La mayoría de los estudios publicados hasta el momento sobre el comportamiento frente a la corrosión de armaduras de acero inoxidable se basan en aceros austeníticos. Sin embargo, la presencia en el mercado de aceros corrugados dúplex es cada vez más importante. En este trabajo se analiza la pasividad de un acero inoxidable dúplex tipo 2205 en comparación con la de un inoxidable austenítico tipo 304. Los ensayos de polarización en disoluciones de Ca(OH2 con cloruros confirman el excepcional comportamiento de los aceros dúplex. La espectroscopía fotoelectrónica de rayos X (XPS informa de que la capa pasiva generada en aceros inoxidables dúplex en medios que simulan la disolución de los poros del hormigón posee mayor contenido en óxidos de Cr que la formada en aire. También se puede deducir de los resultados de XPS que los óxidos de Fe de la capa pasiva de los aceros dúplex se encuentran en forma de Fe3O4 en las disoluciones que simulan el hormigón en vez de en

  10. Corrosion resistance of sintered duplex stainless steel evaluated by electrochemical method

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2006-04-01

    Full Text Available Purpose: Purpose of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements. In the studies behind the preparation of mixes, Schaffler’s diagram was taken into consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245°C/min and slow cooling of 5°C/min in argon atmosphere.Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good corrosion properties. Corrosion resistance of sintered stainless steels is strictly connected with the density and the pore morphology present in the microstructure too. The highest resistance to pitting corrosion was achieved for composition with approximate balance of ferrite and austenite in the microstructure.Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for corrosion properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates and sintering temperatures.Originality/value: The use of elemental powders added to a stainless steel base showed its potentialities, in terms of fair compressibility and final sintered density. In addition a good structural homogeneity and first of all corrosion resistance was achieved, also working with cycles possible for industries.

  11. Microstructural study of duplex stainless steels obtained by powder injection molding

    International Nuclear Information System (INIS)

    Highlights: • The microstructural evolution of sintered PIM duplex stainless steels was studied. • A destabilization of austenite occurs after sintering at high temperature. • Electron backscatter diffraction (EBSD) revealed a remaining of 0.5% of austenite. • Ferrite content was also determined employing a magnetic method. -- Abstract: This experimental work is focused on the study of microstructural evolution during sintering of duplex stainless steels (DSS) obtained by powder injection molding (PIM). Ferritic 430L and austenitic 316L stainless steel powders were previously premixed in a 50/50 volume ratio and afterward they were sintered in low vacuum at different temperatures for 1 h. Microstructural analysis of sintered samples was conducted by means of scanning electron microscopy (SEM) and a compositional analysis of the alloying elements along different phases was performed by energy dispersive analysis of X-rays (EDS). Phase transformations were evaluated by X-ray diffraction (XRD) experiments, and the magnetic phase content was measured with a ferritoscope. The intensity of the main austenite diffraction peak decreases as sintering temperature increases to finally disappear in the sample sintered at 1100 °C. This destabilization of the austenite is probably related to a high Nickel diffusion detected from austenite to ferrite particles. Moreover, electron backscatter diffraction (EBSD) data were collected to quantify microstructural properties. Several EBSD pattern maps were acquired in order to define the amount of austenite phase. Due to the advantages of this technique a 0.5% of austenite could be detected after sintering at 1200 °C. After sintering process, the austenite content in sintered duplex stainless steels obtained through this processing route was lower than expected. Finally, Bain mechanism was proposed as an explanation to this phase transformation takes place. EBSD technique has been proved to be the most suitable to monitor the

  12. Microstructure and mechanical properties of duplex stainless steel subjected to hydrostatic extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Maj, P., E-mail: Piotr.maj@inmat.pw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Adamczyk-Cieślak, B.; Mizera, J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Pachla, W. [High Pressure Research Center, Polish Academy of Sciences, Sokołowska 29, 01-142 Warsaw (Poland); Kurzydłowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland)

    2014-07-01

    The nanostructure and mechanical properties of ferritic-austenitic duplex stainless steel subjected to hydrostatic extrusion were examined. The refinement of the structure in the initial state and in the two deformation states (ε = 1.4 and ε = 3.8) was observed in an optical microscope (OM) and a transmission electron microscope (TEM). The results indicate that the structure evolved from microcrystalline with a grain size of about 4 μm to nanocrystalline with a grain size of about 150 nm in ferrite and 70 nm in austenite. The material was characterized mechanically by tensile tests performed in the two deformation states. The ultimate strength appeared to increase significantly compared to that in the initial deformation stages, which can be attributed to the grain refinement and plastic deformation. The heterogeneity observed in microregions results from the dual-phase structure of the steel. The results indicate that hydrostatic extrusion is a highly potential technology suitable for improving the properties of duplex steels. - Highlights: • Duplex stainless steel was hydro extruded to a total strain of 3.8 • After the last stage of deformation heterogeneous structure was obtained in the material • As a result of stresses non-diffusive transformation γ→α’ occurred in the material • Nanometric (sub)grains were obtained in the austenite regions.

  13. Microstructure and mechanical properties of duplex stainless steel subjected to hydrostatic extrusion

    International Nuclear Information System (INIS)

    The nanostructure and mechanical properties of ferritic-austenitic duplex stainless steel subjected to hydrostatic extrusion were examined. The refinement of the structure in the initial state and in the two deformation states (ε = 1.4 and ε = 3.8) was observed in an optical microscope (OM) and a transmission electron microscope (TEM). The results indicate that the structure evolved from microcrystalline with a grain size of about 4 μm to nanocrystalline with a grain size of about 150 nm in ferrite and 70 nm in austenite. The material was characterized mechanically by tensile tests performed in the two deformation states. The ultimate strength appeared to increase significantly compared to that in the initial deformation stages, which can be attributed to the grain refinement and plastic deformation. The heterogeneity observed in microregions results from the dual-phase structure of the steel. The results indicate that hydrostatic extrusion is a highly potential technology suitable for improving the properties of duplex steels. - Highlights: • Duplex stainless steel was hydro extruded to a total strain of 3.8 • After the last stage of deformation heterogeneous structure was obtained in the material • As a result of stresses non-diffusive transformation γ→α’ occurred in the material • Nanometric (sub)grains were obtained in the austenite regions

  14. Duplex treatment of 304 AISI stainless steel using rf plasma nitriding and carbonitriding

    International Nuclear Information System (INIS)

    Surface of 304 AISI austenitic stainless steel has been modified using duplex treatment technique of nitriding and carbonitriding. A thick modified nitrided layer, of approximately 20 μm, has been achieved when rf inductively coupled plasma was adjusted at 450 W for processing time of only 10 min. After performing the nitrided layer, the nitrided samples were carbonitrided using the same technique at different acetylene partial pressure ratios ranges from 10% to 70%, the balance was pure nitrogen. Different amount of nitrogen and carbon species are diffused underneath the surface through the nitrided layer during carbonitriding process and are found to be gas composition dependent. The treated samples were characterized by glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy and Vickers microhardness tester. The microstructure of the duplex treated layer indicates the formation of γ-Fe4N, Fe3C, CrN and nitrogen-expanded austenite (γN). The thickness of the duplex treated layer increases with increasing the acetylene partial pressure ratio. The surface microhardness of duplex treated samples has been found to be gas composition dependent and increased by 1.29 fold in comparison to the nitrided sample.

  15. Fracture mechanics analysis of cast duplex stainless steel elbows containing a surface crack

    International Nuclear Information System (INIS)

    EDF, in cooperation with the French Atomic Energy Commission (CEA) and Framatome, has conducted a research program on the fracture behavior of aged cast duplex stainless steel elbows. The main task of this program consisted in testing two large diameter aged cast elbows under in-plane closure bending at 420 C. This paper, after a short presentation of the experimental results, presents the ductile fracture analyses performed. Both elbows contained a semi-elliptical notch machined on the outer surface of one flank, oriented either in the longitudinal direction (first test) or in the circumferential one (second test). The crack was submitted to tensile stresses, so it may initiate and subsequently grow by ductile tearing. Despite the low toughness of the steel, the crack extension remained stable up to the end of the tests, the final crack extension reaching 8 mm (first test) and 13 mm (second one). The test analyses were performed using elastic-plastic finite element calculations, with a model built up with 20-node elements and containing about 12,000 nodes. Due to the importance of the ovalization phenomenon in the elbows, the calculations were made under the large deformation hypothesis, requiring the development of a new formulation for the energy release rate parameter G. The first purpose of these calculations was to show their ability to simulate accurately the tests, by comparison with the measurements. The second purpose was to conduct a crack growth analysis by comparing calculated J curves (accounting for different crack depths) to the material J-R curve obtained on CT specimens. The accuracy of this type of analysis is satisfactory, considering the scatter of the J material data

  16. 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.

  17. Effect of ageing on phase evolution and precipitation behaviour of duplex steel

    Science.gov (United States)

    Podany, P.; Kover, M.; Dlouhy, J.

    2015-12-01

    The isothermal formation of secondary phases in duplex stainless steel was studied. Samples were isothermally heat treated (aged) at temperatures of 700, 800 and 850°C in a quenching dilatometer. Microstructured evolution of secondary phases was analysed by means of optical and scanning electron microscopes. Both common phases, Chi and Sigma, were observed. The resulting shrinkage curves from dilatometric measurements show the potential for research into the formation of minor phases and the estimation of transformation kinetics in this kind of steel.

  18. Fabrication of Gd Containing Duplex Stainless Steel Sheet for Neutron Absorbing Structural Materials

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong [Dankook Univ., Yongin (Korea, Republic of); Moon, Byung M. [KITECH, Incheon (Korea, Republic of); Sohn, Dongseong [UNIST, Ulsan (Korea, Republic of)

    2013-10-15

    A duplex stainless steel sheet with 1 wt.% gadolinium was fabricated for a neutron absorbing material with high strength, excellent corrosion resistance, and low cost as well as high neutron absorption capability. The microstructure of the as-cast specimen has typical duplex phases including 31% ferrite and 69% austenite. Main alloy elements like chromium (Cr), nickel (Ni), and gadolinium (Gd) are relatively uniformly distributed in the matrix. Gadolinium rich precipitates were present in the grains and at the grain boundaries. The solution treatment at 1070 .deg. C for 50 minutes followed by the hot-rolling above 950 .deg. C after keeping the sheet at 1200 .deg. C for 1.5 hours are important points of the optimum condition to produce a 6 mm-thick plate without cracking.

  19. The Mechanical Behavior of a 25Cr Super Duplex Stainless Steel at Elevated Temperature

    Science.gov (United States)

    Lasebikan, B. A.; Akisanya, A. R.; Deans, W. F.

    2013-02-01

    Super duplex stainless steel (SDSS) is a candidate material for production tubing in oil and gas wells and subsea pipelines used to transport corrosive hydrocarbon fluids. The suitability of this material for high temperature applications is examined in this article. The uniaxial tensile properties are determined for a 25Cr SDSS over a range of temperature relevant to high pressure-high temperature oil and gas wells. It is shown that there is a significant effect of temperature on the uniaxial tensile properties. Elevated temperature was shown to reduce the Young's modulus and increase the strain hardening index; temperature effects on these two parameters are usually neglected in the design of subsea pipelines and oil well tubulars, and this could lead to wrong predictions of the collapse pressure. The manufacturing process of the super duplex tubular did not lead to significant anisotropy in the hardness and the ultimate tensile and uniaxial yield strengths.

  20. Use of a gray level co-occurrence matrix to characterize duplex stainless steel phases microstructure

    Directory of Open Access Journals (Sweden)

    L. Zortea

    2011-04-01

    Full Text Available Duplex stainless steels are widely used in industry. This is due to their higher strength compared to austenitic steels and to their higher toughness than ferritic steels. They also have good weldability and high resistance to stress corrosion cracking.These steels are characterized by two-phase microstructures composed by almost the same level of ferrite and austenite.Duplex steel 2205 samples evaluated are: as received, cold rolled (33% and heat-treated at 800°C for 10 hours.A metallographic etching with 10% oxalic acid has been carried out to highlight the phases morphology. Some photos have been taken by SEM microscope and submitted to image analysis. The analysis carried out is based on the determination of co-occurrence matrix and on the following interpretation of appropriate indicators. Through these indicators is possible to estimate the features of images objectively.

  1. Spinodal decomposition mechanism study on the duplex stainless steel UNS S31803 using ultrasonic speed measurements

    International Nuclear Information System (INIS)

    This work, focuses on the spinodal decomposition mechanism study on the duplex stainless steel duplex UNS S31803, composed by austenite (γ) and ferrite (α) phases, at 425 oC and 475 oC temperatures by ultrasonic speed measurements. This temperature range is responsible for the transformation mechanism of αinitial phase to α phases (poor in chromium) and α' (rich in chromium) by spinodal decomposition. The techniques to accomplish this analysis are based mainly on X-ray diffraction measures and ultrasonic speed. The obtained results show that it is possible to conclude that the use of ultrasonic speed measurements indicates a promising technique for following-up the phase transformation and spinodal decomposition on the steel studied.

  2. TEM [transmission electron microscopy], APFIM [atom-probe field ion microscopy], and SANS [small-angle neutron scattering] examination of aged duplex stainless steel components from some decommissioned reactors

    International Nuclear Information System (INIS)

    The present investigation indicates that the primary embrittlement processes of the CF-8 grade cast stainless steel components during extended reactor service are spinodal decomposition of the ferrite phase and M23C6 carbide precipitation on the austenite-ferrite boundaries. The ferrite hardness measured for the Shippingport reactor valves appears to reflect the different extent of spinodal decomposition among the different valves which contain slightly different Cr contents. G-phase precipitation was minimal compared to that during accelerated aging of CF-8 steel in the laboratory (i.e., near 400/degree/C). This indicates that the activation energy may be strongly influenced by the synergism among the G-phase precipitation, carbide formation, and spinodal decomposition. 13 refs., 2 figs

  3. Duplex and Superduplex stainless steel grades for wet flue gas desulphurisation systems

    Energy Technology Data Exchange (ETDEWEB)

    Peultier, J.; Barrau, F.; Gagnepain, J.C.; Soulignac, P. [Industeel ArcelorMittal, Le Creusot (France)

    2008-05-15

    Initially this paper deals with the corrosion risks related to the local environments which are expected to exist in each area of a wet flue gas desulphurization system. Then the uniform and localized corrosion resistances of different stainless steels are studied by electrochemical testing performed under laboratory conditions which simulate process conditions. In particular, the effect of chloride content, fluoride content, pH and temperature on corrosion resistance is discussed. The results show that duplex UNS S32205 or superduplex UNS S32520 grades may be used in many aggressive environments where austenitic grade 317LNM or super austenitic grades like UNS S34565 have normally been selected. The life cycle costs of scrubbers constructed of stainless steels plates or clad plates are compared in a second part of the paper. The excellent corrosion resistance of duplex and superduplex stainless steels, combined with the increased mechanical properties and moderate alloy cost (lower nickel and molybdenum content) make these materials very cost effective solutions for wet flue gas desulphurization applications.

  4. Selective corrosion of duplex stainless steel. Pt. 2 Localized corrosion manifestations under exposure of chlorides on duplex stainless steel X2CrNiMoN22-5-3 and mechanical behavior in dependence of the microstructure

    International Nuclear Information System (INIS)

    In completion to part 1 of this paper this part deals with interrelations between localized corrosion manifestations, mechanical properties and the microstructure of duplex stainless steel X2CrNiMoN22-5-3. The pit formation on duplex stainless steels is substantially determined by the distribution of the alloying elements within single phases and by defects in the oxide layer. The positive properties of molybdenum become ineffective at thicker oxide layers due to the fact, that molybdate, which is responsible for inhibition of pitting, can not be formed. Depletion areas caused by precipitations are preferential attack places for corrosion. The influence of chlorides for duplex stainless steels in rolled and welded conditions is characterized by a logarithmic dependence. (orig.)

  5. Influence of sintering parameters on the properties of duplex stainless steel

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-01-01

    Full Text Available Purpose: of this paper was to examine the influence of sintering parameters like time, temperature, atmosphereand gas pressure under cooling stage on the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powdermetallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements,such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was takeninto consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace withargon backfilling at temperatures from 1200°C to 1285°C for 0.5, 1 and 2 h. After sintering different coolingcycles were applied using nitrogen under pressure from 0.6 MPa to 0.002MPa in argon atmosphere. Producedduplex stainless steels have been studied by scanning and optical microscopy and EDS chemical analysis ofmicrostructure components. Mechanical properties have been studied through tensile test.Findings: Mechanical properties of sintered stainless steels are strictly connected with the density and the poremorphology present in the microstructure too and especially of cooling rate directly from sintering temperature.The lowest cooling rate - applied gas pressure, the mechanical properties decrease due to precipitation of sigmaphase. Mechanical properties of studied steels depends on austenite/ferrite ratio in the microstructure andelements partitioning between phases too.Research limitations/implications: Applied fast cooling rate seems to be a good compromise for mechanicalproperties and obtained microstructures, nevertheless further tests should be carried out in order to examine itinfluence on corrosion properties.Originality/value: The use of elemental powders added to a stainless steel base showed its potentialities, interms of fair compressibility and final sintered density. In addition a good microstructural homogeneity

  6. The influence of nitrogen alloying on the pitting and crevice corrosion of austenitic and duplex stainless steels

    International Nuclear Information System (INIS)

    The effect of nitrogen alloying on the pitting corrosion resistance of duplex and austenitic stainless steels has been examined. In order to avoid alteration of the phase ratio as a result of nitrogen alloying of the duplex steels, a simultaneous decrease has been made in the nickel content. Austenitic alloys of compositions corresponding to the austenite phase of the duplex steels have been investigated and compared to the behaviour of austenitic steels in which the nitrogen content or the nickel content alone has been varied. Nitrogen has a beneficial effect on pitting and crevice corrosion resistance in all cases but the duplex stainless steel exhibit a lower resistance to pitting and a higher resistance to crevice corrosion than predicted from the austenite nitrogen content. (orig.)

  7. Role of Austenite in Brittle Fracture of Bond Region of Super Duplex Stainless Steel

    Science.gov (United States)

    Kitagawa, Yoshihiko; Ikeuchi, Kenji; Kuroda, Toshio

    Weld simulation of heat-affected zone (HAZ) was performed to investigate the mechanism by which austenite affects the toughness of super duplex stainless steel. Thermal cycles of various peak temperatures in the range from 1373 K to 1673 K corresponding to the HAZ were applied to SAF2507 super duplex stainless steel specimens. Charpy impact test was carried out using the specimens after the weld simulation, and the fracture surfaces were observed by SEM using three-dimensionally reconstruction technique. Austenite content decreased with increasing the peak temperature when the peak temperature exceeded 1473 K and the impact value decreased with increasing the peak temperature and decreasing the austenite content. The thermal cycle of the peak temperature of 1673 K corresponding to weld bond region caused decreasing of austenite content which was 22% lower than that of the base metal. The ductile-brittle transition temperature was measured. As a result the temperature increased rapidly in the weld bond region, the peak temperature of which exceeded 1623 K by the grain growth of ferrite matrix occurring subsequently to the completely dissolution of austenite. The morphology of the fracture surfaces after impact testing at 77 K showed cleavage fracture of ferrite. The {100} orientations of cleavage fracture facets were measured using three-dimensional images of the fracture surfaces and the results were visualized as the orientation color maps. The results showed that there were cleavage fractures consisting of a few facets parallel to each other. It was considered that a few facets existed in one ferrite grain. It was concluded that Widmanstätten austenite divided the large fracture into smaller cleavage facets in a ferrite grain and then suppressed the degradation of bond toughness of duplex stainless steel.

  8. Effect of laser shock processing on fatigue crack growth of duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Gonzalez, C., E-mail: crubio@cidesi.mx [Centro de Ingenieria y Desarrollo Industrial, Pie de la Cuesta, 702, Desarrollo San Pablo, Queretaro, Qro., 76130 (Mexico); Felix-Martinez, C. [Centro de Ingenieria y Desarrollo Industrial, Pie de la Cuesta, 702, Desarrollo San Pablo, Queretaro, Qro., 76130 (Mexico); Gomez-Rosas, G. [Universidad de Guadalajara, Guadalajara, Jal (Mexico); Ocana, J.L.; Morales, M.; Porro, J.A. [Departamento de Fisica Aplicada a la Ingenieria Industrial, E.T.S.I.I., Universidad Politecnica de Madrid (Spain)

    2011-01-25

    Research highlights: {yields} LSP is an effective surface treatment to improve fatigue properties of duplex stainless steel. {yields} Increasing pulse density, fatigue crack growth rate is reduced. {yields} Microstructure is not affected by LSP. {yields} Compressive residual stresses increases increasing pulse density. - Abstract: Duplex stainless steels have wide application in different fields like the ship, petrochemical and chemical industries that is due to their high strength and excellent toughness properties as well as their high corrosion resistance. In this work an investigation is performed to evaluate the effect of laser shock processing on some mechanical properties of 2205 duplex stainless steel. Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduces fatigue crack growth rate. A convergent lens is used to deliver 2.5 J, 8 ns laser pulses by a Q-switched Nd:YAG laser, operating at 10 Hz with infrared (1064 nm) radiation. The pulses are focused to a diameter of 1.5 mm. Effect of pulse density in the residual stress field is evaluated. Residual stress distribution as a function of depth is determined by the contour method. It is observed that the higher the pulse density the greater the compressive residual stress. Pulse densities of 900, 1600 and 2500 pul/cm{sup 2} are used. Pre-cracked compact tension specimens were subjected to LSP process and then tested under cyclic loading with R = 0.1. Fatigue crack growth rate is determined and the effect of LSP process parameters is evaluated. In addition fracture toughness is determined in specimens with and without LSP treatment. It is observed that LSP reduces fatigue crack growth and increases fracture toughness if this steel.

  9. Effect of laser shock processing on fatigue crack growth of duplex stainless steel

    International Nuclear Information System (INIS)

    Research highlights: → LSP is an effective surface treatment to improve fatigue properties of duplex stainless steel. → Increasing pulse density, fatigue crack growth rate is reduced. → Microstructure is not affected by LSP. → Compressive residual stresses increases increasing pulse density. - Abstract: Duplex stainless steels have wide application in different fields like the ship, petrochemical and chemical industries that is due to their high strength and excellent toughness properties as well as their high corrosion resistance. In this work an investigation is performed to evaluate the effect of laser shock processing on some mechanical properties of 2205 duplex stainless steel. Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduces fatigue crack growth rate. A convergent lens is used to deliver 2.5 J, 8 ns laser pulses by a Q-switched Nd:YAG laser, operating at 10 Hz with infrared (1064 nm) radiation. The pulses are focused to a diameter of 1.5 mm. Effect of pulse density in the residual stress field is evaluated. Residual stress distribution as a function of depth is determined by the contour method. It is observed that the higher the pulse density the greater the compressive residual stress. Pulse densities of 900, 1600 and 2500 pul/cm2 are used. Pre-cracked compact tension specimens were subjected to LSP process and then tested under cyclic loading with R = 0.1. Fatigue crack growth rate is determined and the effect of LSP process parameters is evaluated. In addition fracture toughness is determined in specimens with and without LSP treatment. It is observed that LSP reduces fatigue crack growth and increases fracture toughness if this steel.

  10. Welds in the lean duplex stainless steel LDX 2101 : effect of microstructure and weld oxides on corrosion properties

    OpenAIRE

    Westin, Elin M.

    2008-01-01

    Duplex stainless steels are a very attractive alternative to austenitic grades due to their higher strength and good corrosion performance. The austenitic grades can often be welded autogenously, while the duplex grades normally require addition of filler metal. This is to counteract segregation of important alloying elements and to give sufficient austenite formation to prevent precipitation of chromium nitrides that could have a negative effect on impact toughness and pitting resistance. Th...

  11. EFFECT OF MICROSTRUCTURE AND SURFACE FINISH ON LOCALIZED CORROSION PERFORMANCE OF SUPER DUPLEX STAINLESS STEEL IN SEAWATER

    OpenAIRE

    Næss, Monika

    2014-01-01

    Corrosion resistant alloys (CRAs) used in subsea pressure-retaining components must be compatible with production fluids and resistant to pitting and crevice corrosion in seawater. Whereas materials selection in production environments is governed by well-established international standards such as ISO 15156, much debate still exists as of how to determine the seawater localized corrosion resistance of higher grade CRAs such as duplex super duplex stainless steels (DSS and SDSS, respectively)...

  12. EBSD investigation of the microstructure and texture characteristics of hot deformed duplex stainless steel.

    Science.gov (United States)

    Cizek, P; Wynne, B P; Rainforth, W M

    2006-05-01

    The microstructure and crystallographic texture characteristics were studied in a 22Cr-6Ni-3Mo duplex stainless steel subjected to plastic deformation in torsion at a temperature of 1000 degrees C using a strain rate of 1 s(-1). High-resolution EBSD was successfully used for precise phase and substructural characterization of this steel. The austenite/ferrite ratio and phase morphology as well as the crystallographic texture, subgrain size, misorientation angles and misorientation gradients corresponding to each phase were determined over large sample areas. The deformation mechanisms in each phase and the interrelationship between the two are discussed. PMID:16774517

  13. Relationship between hydrogen-induced phase transformations and pitting nucleation sites in duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Liqiu; Yang, Binjie; Qin, Sixiao [University of Science and Technology Beijing (China). Corrosion and Protection Center

    2016-02-15

    This paper demonstrates the hydrogen-induced phase transformation and the associated pitting nucleation sites of 2507 duplex stainless steel using scanning Kelvin probe force microscopy and magnetic force microscopy. The low potential sites in Volta potential images, which are considered as the pitting nucleation sites, are strongly dependent on the hydrogen-induced phase transformation. They firstly initiate on the magnetic martensite laths in the austenite phase or at the ferrite/austenite boundaries, and then appear near the needle-shaped microtwins in the ferrite phase, because of the difference in physicochemical properties of hydrogen-induced phase transformation microstructures.

  14. σ- Phase precipitation in a duplex stainless steel: an APFIM investigation

    Science.gov (United States)

    Swens, J. J.; Kolster, B. H.

    1991-04-01

    Structural transformations at elevated temperatures severely damage the mechanical and corrosion resistant properties of duplex stainless steels. One of the most deleterious transformations is the precipitation of σ-phase. In order to gain a better understanding of this precipitation an AP-FIM analysis has been performed on a γ-σ phase boundary. Compositions for the austenite, the σ-phase and the γ-σ phase boundary, have been obtained as well as a γ-σ phase boundary composition profile. A first attempt has been made to use the N 2+ distribution in order to verify the troublesome N-Si deconvolution.

  15. Microhardness changes gradient of the duplex stainless steel (DSS surface layer after dry turning

    Directory of Open Access Journals (Sweden)

    G. Krolczyk

    2014-10-01

    Full Text Available The article presents the gradient of microhardness changes as a function of the distance from the material surface after turning with a wedge provided with a coating with a ceramic intermediate layer. The investigation comprised the influence of cutting speed on surface integrity microhardness in dry machining. The tested material was duplex stainless steel (DSS with two-phase, ferritic-austenitic structure. The tests have been performed under production conditions during machining of parts for electric motors and deep-well pumps.

  16. Investigation of selected surface integrity features of duplex stainless steel (DSS after turning

    Directory of Open Access Journals (Sweden)

    G. Krolczyk

    2015-01-01

    Full Text Available The article presents surface roughness profiles and Abbott - Firestone curves with vertical and amplitude parameters of surface roughness after turning by means of a coated sintered carbide wedge with a coating with ceramic intermediate layer. The investigation comprised the influence of cutting speed on the selected features of surface integrity in dry machining. The material under investigation was duplex stainless steel with two-phase ferritic-austenitic structure. The tests have been performed under production conditions during machining of parts for electric motors and deep-well pumps. The obtained results allow to draw conclusions about the characteristics of surface properties of the machined parts.

  17. Evaluation of the magnetic permeability for the microstructural characterization of a duplex stainless steel

    OpenAIRE

    Edgard de M. Silva; Josinaldo P. Leite; Francisco A. de França Neto; Leite, João P.; Walter M. L. Fialho; de Albuquerque, Victor Hugo C.; João Manuel R. S. Tavares

    2016-01-01

    Non-Destructive Testing has been commonly used to assess the presence of discontinuities that may affect the integrity of materials in service. In this study, a Hall effect sensor is used in a methodology developed to study in a non-destructive manner the microstructural variations of a material that occur due to the single-phase decomposition. The material selected was the UNS S31803 duplex stainless steel, particularly due to its behavior under temperatures below 525 °C. Measurements of mag...

  18. Effect of Nitrogen Partitioning on Yield Strength in Nitrogen-Alloyed Duplex Stainless Steel During Annealing

    Science.gov (United States)

    Jang, Min-Ho; Moon, Joonoh; Lee, Tae-Ho; Park, Seong-Jun; Han, Heung Nam

    2014-04-01

    Nitrogen partitioning and its effect on the yield strength in nitrogen-alloyed duplex stainless steel during annealing were investigated at different annealing temperatures. The decrease in the austenite fraction with an increase in the annealing temperature promoted nitrogen partitioning into austenite. When the nitrogen content in austenite was low, the yield strength decreased with an increase in the annealing temperature due to grain growth, while when it was higher than 0.5 wt pct, the yield strength increased with an increase in the annealing temperature, because the austenite became noticeably hard.

  19. A study on the effect of solution heat treatment on the corrosion resistance of super duplex stainless steels

    International Nuclear Information System (INIS)

    High temperature solution heat treatment(typically higher than 1100 .deg. C) is known generally to reduces the resistance to localized corrosion on super duplex stainless. This is attributed to the formation of zone depleted of alloying elements. In this study, the corrosion properties were investigated on super duplex stainless steels with various solution heat treatments. The corrosion resistance of these steels was evaluated in terms of critical pitting temperature and cyclic potentiodynamic polarization test. Chemical composition of the austenite and ferrite phases were analyzed by SEM-EDS. The following results were obtained. (1) By conducting furnace cooling, critical pitting temperature and repassivation potential increased. (2) By omitting furnace cooling, solution heat treatment produced Cr and Mo depleted zone in the phase boundary. (3) During furnace cooling, Cr and Mo rediffused through the phase boundary. This increased the corrosion resistance of super duplex stainless steels

  20. Corrosion behavior of a high-chromium duplex stainless steel with minor additions of ruthenium in sulfuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Potgieter, J.H. [Pretoria Portland Cement, Johannesburg (South Africa). Technical Services Dept.; Brookes, H.C. [Univ. of Natal, Durban (South Africa). Dept. of Chemistry

    1995-04-01

    The influence of small ruthenium additions on the corrosion behavior of high-chromium duplex stainless steels (DSS) was studied. Ruthenium additions ({le} 0.28%) increased the corrosion resistance of the base alloy by simultaneously improving hydrogen evolution efficiency and inhibiting anodic dissolution. The corrosion behavior of the high-chromium DSS with small ruthenium additions differed somewhat from behavior of similar duplex alloys of the 22%-Cr type. The lowering of hydrogen overpotential, which promotes an elevated corrosion potential leading to passivity, was much more significant in the 29%-Cr duplex alloys than in the 22%-Cr types.

  1. Influence of surface texture on the galling characteristics of lean duplex and austenitic stainless steels

    DEFF Research Database (Denmark)

    Wadman, Boel; Eriksen, J.; Olsson, M.;

    2010-01-01

    Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations of...... industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed to...... high strain levels in tools normally applied for forming of austenitic steels, but tool adaptations are needed to comply with the higher strength and springback of the material....

  2. Development of corrosion resistant high silicon duplex stainless steel DP9 for reprocessing plants

    International Nuclear Information System (INIS)

    A new high silicon duplex stainless steel, DP 9, has been developed as a construction material for reprocessing plants dealing with used nuclear fuels. This alloy contain 23 % chrominum, 11 % nickel, 3.3 % silicon and 0.1 % nitrogen. It shows corrosion resistance to concentrated nitric acid at high temperatures superior to commercially available stainless steels. The mechanical properties, corrosion resistance, weldability, and physical properties of plates, pipe and joints made from this material were evaluated. Both base metal and welded joints showed excellent corrosion resistance to nitric acid with or without oxidizing Cr6+ ions at high concentrations and temperatures. Weldability, as evaluated by Varestraint test, restraint weld cracking test and weld joining test, was also good. In addition, proper welding conditions for good mechanical and corrosion properties are reported on. It was confirmed by trial manufacturing that plates, pipe, pipe joints, and welding material made of DP 9 are commercially applicable. (author)

  3. Study of Corrosion Behavior of a 2507 Super Duplex Stainless Steel : Influence of Quenched-in and Isothermal Nitrides

    OpenAIRE

    Bettini, Eleonora; Kivisäkk, Ulf; Leygraf, Christofer; Pan, Jinshan

    2014-01-01

    Precipitation of different types of chromium nitrides may occur during processing of super duplex stainless steels, affecting the properties of the material. In this study the influence of quenched-in (size range ca. 50-100 nm) and isothermal (size range ca. 80-250 nm) types of nitrides on the corrosion behavior of a 2507 super duplex stainless steel has been investigated at room temperature and at 90 degrees C (above the critical pitting temperature) in 1 M NaCl solution. The microstructure ...

  4. Precipitation of Chromium Nitrides in the Super Duplex Stainless Steel 2507

    Science.gov (United States)

    Pettersson, Niklas; Pettersson, Rachel F. A.; Wessman, Sten

    2015-03-01

    Precipitation of chromium nitrides during cooling from temperatures in the range 1373 K to 1523 K (1100 °C to 1250 °C) has been studied for the super duplex stainless steel 2507 (UNS S32750). Characterization with optical, scanning and transmission electron microscopy was combined to quantify the precipitation process. Primarily Cr2N nitrides were found to precipitate with a high density in the interior of ferrite grains. An increased cooling rate and/or an increased austenite spacing clearly promoted nitride formation, resulting in precipitation within a higher fraction of the ferrite grains, and lager nitride particles. Furthermore, formation of the meta-stable CrN was induced by higher cooling rates. The toughness seemed unaffected by nitrides. A slight decrease in pitting resistance was, however, noticed for quenched samples with large amounts of precipitates. The limited adverse effect on pitting resistance is attributed to the small size (~200 nm) of most nitrides. Slower cooling of duplex stainless steels to allow nitrogen partitioning is suggested in order to avoid large nitrides, and thereby produce a size distribution with a smaller detrimental effect on pitting resistance.

  5. Fatigue cracking of hybrid plasma gas metal arc welded 2205 duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Yurtisik, Koray; Tirkes, Suha [Middle East Technical Univ., Ankara (Turkey). Welding Technology and Nondestructive Testing Research/Application Center

    2014-10-01

    Contrary to other keyhole welding applications on duplex stainless steels, a proper cooling time and a dilution were achieved during hybrid plasma gas metal arc welding that provided sufficient reconstructive transformation of austenite without sacrificing its high efficiency and productivity. Simultaneous utilization of keyhole and metal deposition in the hybrid welding procedure enabled us to get an as-welded 11 mm-thick standard duplex stainless steel plate in a single pass. Metallographic examination on hybrid plasma-gas metal arc weldments revealed only primary austenite in ferrite matrix, whereas in addition to reconstructive transformation of primary austenite during solidification, secondary austenite was also transformed in a displacive manner due to successive thermal cycles during multi-pass gas metal arc welding. On the one hand, secondary austenite provided barriers and retarded the crack propagation during the tests in laboratory air. On the other hand, chromium and molybdenum depletion in the neighborhood of secondary austenite precipitates yielded relatively high crack propagation rates in multi-pass weldments under chloride attack.

  6. Fatigue cracking of hybrid plasma gas metal arc welded 2205 duplex stainless steel

    International Nuclear Information System (INIS)

    Contrary to other keyhole welding applications on duplex stainless steels, a proper cooling time and a dilution were achieved during hybrid plasma gas metal arc welding that provided sufficient reconstructive transformation of austenite without sacrificing its high efficiency and productivity. Simultaneous utilization of keyhole and metal deposition in the hybrid welding procedure enabled us to get an as-welded 11 mm-thick standard duplex stainless steel plate in a single pass. Metallographic examination on hybrid plasma-gas metal arc weldments revealed only primary austenite in ferrite matrix, whereas in addition to reconstructive transformation of primary austenite during solidification, secondary austenite was also transformed in a displacive manner due to successive thermal cycles during multi-pass gas metal arc welding. On the one hand, secondary austenite provided barriers and retarded the crack propagation during the tests in laboratory air. On the other hand, chromium and molybdenum depletion in the neighborhood of secondary austenite precipitates yielded relatively high crack propagation rates in multi-pass weldments under chloride attack.

  7. Corrosion behaviour of hyper duplex stainless steel in various metallurgical conditions for sea water cooled condensers

    International Nuclear Information System (INIS)

    The sea water cooled condensers have to resist severe corrosion as marine environment is the most corrosive natural environment. Copper alloys are being phased out due to difficulties in water chemistry control and Titanium base alloys are extremely expensive. Austenitic stainless steels (SS) remain prone to localized corrosion in marine environments hence not suitable. These heat exchangers operate at temperatures not exceeding 50 deg C and at very low pressures. The tubes of these heat exchangers are joined to the carbon steel tube sheets by roll expansion or by roll expansion followed by seam welding. These conditions are expected to affect the localized corrosion resistance of the tube in roll joined region due to cold working and in the tube-tube sheet welded joint due to thermal effects of welding. In this study, the localized corrosion behaviour of a Hyper Duplex Stainless Steel (HDSS) has been evaluated, and compared with other materials e.g. types 304L SS, 316L SS, Duplex SS 2205, Titanium grade - 2, and Al Brass. The evaluation is done in three metallurgical conditions (a) as received, (b) cold rolled and (c) welded condition in synthetic sea water at room temperature and at 50 deg C to assess the resistance to crevice, pitting and stress corrosion cracking using standard ASTM exposure and electrochemical techniques. The results provide comparative assessment of these alloys and show their susceptibility in the three metallurgical conditions as encountered in condensers. Hyper-duplex SS has been shown to be highly resistant in sea water for the condenser tubing application. (author)

  8. High nitrogen-dosed austenitic-stainless steels and duplex steels

    International Nuclear Information System (INIS)

    The austenitic grades represent the most important group in the family of stainless steels. Nitrogen addition to austenitic stainless steels provides much higher yield strength. It was the goal of the present work to develop new high strength austenitic and duplex stainless steels and to investigate the beneficial influence of nitrogen. More than 40 small ingots up to a weight of 1.5 kg were melted in a specially developed high pressure induction furnace. In addition 20 more alloys produced by a pressurized electro slag remelting facility were included in this investigation. The nitrogen content was varied between 0.37 and 1.47 wt.%. New coefficients are proposed for the nickel equivalent in the Schaeffler diagram; these are from 0.12 to 0.24 for manganese and 18 for nitrogen. The increase in yield strength by interstitially dissolved nitrogen is due to solid solution hardening and to increased grain boundary hardening. The addition of 1% nitrogen gives a yield strength of more than 759 MPa. The toughness remains very good. At room temperature nitrogen alloyed Fe-Cr-Mn austenitic steels give the highest product of strength and toughness. Nitrogen containing austenitic stainless steels show a substantial increase in strength at low temperature. From room temperature to 4K the yield strength is more than tripled. Nitrogen alloyed Fe-Cr-Mn austenitic stainless steels exhibit a ductile to brittle transition as the temperature is lowered. This is due to a planar deformation mode which could be caused by low stacking fault energy. Nickel improves the low temperature toughness and also raises the stacking fault energy. In the temperature range from 600 to 900oC, Cr2N precipitate. The minimal time for precipitation is longer by a factor of 10 than in Fe-Cr-Ni grade. Nitrogen decreases the corrosion rate in austenitic and duplex stainless steels. The resistance to pitting corrosion can be described by the equation WL= %Cr + 3.3 %Mo + 30 %N. (author) figs., tabs., refs

  9. Characterization of duplex stainless steels by TEM [transmission electron microscopy], SANS [small-angle neutron scattering], and APFIM [atom-probe field ion microscopy] techniques

    International Nuclear Information System (INIS)

    Results are presented of complementary characterization of aged duplex stainless steels by advanced metallographic techniques, including transmission and high-voltage electron microscopies; small-angle neutron scattering; and atom-probe field ion microscopy. On the basis of the characterization, the mechanisms of aging embrittlement have been shown to be associated with the precipitation of Ni- and Si-rich G phase and Cr-rich α' in the ferrite, and M23C6 carbides on the austenite-ferrite phase boundaries. 19 refs., 19 figs., 1 tab

  10. X-Ray diffraction technique applied to study of residual stresses after welding of duplex stainless steel plates

    Energy Technology Data Exchange (ETDEWEB)

    Monin, Vladimir Ivanovitch; Assis, Joaquim Teixeira de [Instituto Politecnico do Rio e Janeiro (IPRJ), Nova Friburgo, RJ (Brazil); Lopes, Ricardo Tadeu; Turibus, Sergio Noleto; Payao Filho, Joao C., E-mail: sturibus@nuclear.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil)

    2014-08-15

    Duplex stainless steel is an example of composite material with approximately equal amounts of austenite and ferrite phases. Difference of physical and mechanical properties of component is additional factor that contributes appearance of residual stresses after welding of duplex steel plates. Measurements of stress distributions in weld region were made by X-ray diffraction method both in ferrite and austenite phases. Duplex Steel plates were joined by GTAW (Gas Tungsten Arc Welding) technology. There were studied longitudinal and transverse stress components in welded butt joint, in heat affected zone (HAZ) and in points of base metal 10 mm from the weld. Residual stresses measured in duplex steel plates jointed by welding are caused by temperature gradients between weld zone and base metal and by difference of thermal expansion coefficients of ferrite and austenite phases. Proposed analytical model allows evaluating of residual stress distribution over the cross section in the weld region. (author)

  11. X-Ray diffraction technique applied to study of residual stresses after welding of duplex stainless steel plates

    International Nuclear Information System (INIS)

    Duplex stainless steel is an example of composite material with approximately equal amounts of austenite and ferrite phases. Difference of physical and mechanical properties of component is additional factor that contributes appearance of residual stresses after welding of duplex steel plates. Measurements of stress distributions in weld region were made by X-ray diffraction method both in ferrite and austenite phases. Duplex Steel plates were joined by GTAW (Gas Tungsten Arc Welding) technology. There were studied longitudinal and transverse stress components in welded butt joint, in heat affected zone (HAZ) and in points of base metal 10 mm from the weld. Residual stresses measured in duplex steel plates jointed by welding are caused by temperature gradients between weld zone and base metal and by difference of thermal expansion coefficients of ferrite and austenite phases. Proposed analytical model allows evaluating of residual stress distribution over the cross section in the weld region. (author)

  12. Effect of heat treatment on the Mechanical Properties and Corrosion Behavior of Duplex Stainless Steel Pipeline Weldments

    International Nuclear Information System (INIS)

    Duplex stainless steel (DSS) is a relatively new class of alloys characterized by a low - carbon content (< 0.03 wt %). body centered cubic ferrite . face centered cubic austenite microstructure, and additions of molybdenum, nitrogen, tungsten nd copper. the typical chromium and nickel contents are 20 to 30% and 5 to 10% respectively. the specific advantages offered by DSS over conventional 300 series stainless steel are strength (about twice that of austenitic stainless steels), chloride-stress corrosion cracking resistance and pitting corrosion resistance. these materials are used in the intermediate temperature range about-60 to 300 C where resistance to acids and aqueous chloride is required

  13. Short fatigue cracks nucleation and growth in lean duplex stainless steel LDX 2101

    Energy Technology Data Exchange (ETDEWEB)

    Strubbia, R., E-mail: strubbia@ifir-conicet.gov.ar [Instituto de Física Rosario – CONICET, Universidad Nacional de Rosario (Argentina); Hereñú, S.; Alvarez-Armas, I. [Instituto de Física Rosario – CONICET, Universidad Nacional de Rosario (Argentina); Krupp, U. [Faculty of Engineering and Computer Science, University of Applied Sciences Osnabrück (Germany)

    2014-10-06

    This work is focused on the fatigue damage of lean duplex stainless steels (LDSSs) LDX 2101. Special interest is placed on analyzing short fatigue crack behavior. In this sense, short crack initiation and growth during low cycle fatigue (LCF) and short crack nucleation during high cycle fatigue (HCF) of this LDSS have been studied. The active slip systems and their associated Schmid factors (SF) are determined using electron backscattered diffraction (EBSD). Additionally, the dislocation structure developed during cycling is observed by transmission electron microscopy (TEM). Regardless of the fatigue regime, LCF and HCF, short cracks nucleate along intrusion/extrusions in ferritic grains. Moreover, during the LCF phase boundaries decelerate short crack propagation. These results are rationalized by the hardness of the constitutive phases and the dependence of screw dislocation mobility in the ferrite phase on strain rate and stress amplitude.

  14. Embrittlement of a Duplex Stainless Steel in Acidic Environment Under Applied Cathodic Potentials

    Science.gov (United States)

    Roychowdhury, S.; Kain, Vivekanand

    2008-10-01

    Hydrogen-induced degradation of mechanical properties of a duplex stainless steel in 0.1N H2SO4 solution has been studied under in situ cathodic charging conditions. Significant reductions in percentage of elongation, toughness, and time to failure were noticed due to the ingress of hydrogen into the material at various applied cathodic potentials in the range of -200 to -800 mV (SCE). Cleavage fractures were identified mainly in the ferritic phases. Crack growth was observed to be inhibited by the austenite phase. However, depending on the severity of the environment, both the ferrite and austenite phases could be embrittled. At less negative potentials, presence of surface film and low hydrogen fugacity seemed to control hydrogen ingress in the metal. Addition of thiosulfate to the acidic solution further degraded the mechanical properties of the steel at the applied cathodic potential.

  15. Effect of Secondary Phase Precipitation on the Corrosion Behavior of Duplex Stainless Steels

    Directory of Open Access Journals (Sweden)

    Kai Wang Chan

    2014-07-01

    Full Text Available Duplex stainless steels (DSSs with austenitic and ferritic phases have been increasingly used for many industrial applications due to their good mechanical properties and corrosion resistance in acidic, caustic and marine environments. However, DSSs are susceptible to intergranular, pitting and stress corrosion in corrosive environments due to the formation of secondary phases. Such phases are induced in DSSs during the fabrication, improper heat treatment, welding process and prolonged exposure to high temperatures during their service lives. These include the precipitation of sigma and chi phases at 700–900 °C and spinodal decomposition of ferritic grains into Cr-rich and Cr-poor phases at 350–550 °C, respectively. This article gives the state-of the-art review on the microstructural evolution of secondary phase formation and their effects on the corrosion behavior of DSSs.

  16. MICROSTRUCTURE AND TENSILE PROPERTY OF AN AS-CAST DUPLEX STAINLESS STEEL

    Institute of Scientific and Technical Information of China (English)

    P.L.Mao; K.Yang; G.Y.Su

    2001-01-01

    The effect of high temperature solution heat treatment on the microstructure and ten-sile property of as-cast 0Cr17Mn14Mo2N duplex stainless steel was investigated.Itwas found that the morphology ofδ-ferrite in the dual phases microstructures changedgradually from dendritic to lamellar and then to spheroidal,and its distribution be-came more uniform under appropriate treatment.When the treat temperature waslower than 1250C,the spheroidial ratio and the homogeneous distribution o fδ-ferriteincrease with increasing temperature,which corresponds to a better tensile property.In addition,when the treat temperature reached 1250~C and above,the microstructureconsists of coarse equiaxial δ-ferrite grains with the needle austenite at its boundaries,which results in a decrease of the tensile properties of the steel.

  17. Relative merits of duplex and austenitic stainless steels for applications in the oil and gas industry

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, Elisabeth; Wegrelius, Lena; Pettersson, Rachel [Outokumpu Stainless AB, Avesta (Sweden)

    2012-07-01

    The broad range of available stainless steel grades means that these materials can fulfil a wide variety of requirements within the oil and gas industry. The duplex grades have the advantage of higher strength than standard austenitic grades, while the superaustenitic grades provide a cost-effective alternative to nickel-base alloys in a number of cases. The paper presents the results of various types of laboratory testing to rank the grades in terms of resistance to pitting, crevice corrosion and stress corrosion cracking. Results from field testing in actual or simulated service conditions are discussed and a number of application examples, including process piping flexible, heat exchangers and topside equipment are presented. (author)

  18. Passivation behavior of Ce-containing hyper duplex stainless steels in sulfuric acid solution

    International Nuclear Information System (INIS)

    The passivation behavior of Ce containing hyper duplex stainless steels in sulfuric acid solution was investigated by electrochemical testing and X-ray photoelectron spectroscopy surface analysis. The addition of Ce to the alloy increased the corrosion resistance at a passive region of 0.4 VSCE. The Ce addition also improved the stability of the passive film because of the formation of inclusions containing Ce with low Cr content and an enrichment of the Cr oxide and hydroxide in the passive film. Further, Ce addition to the alloy decreased the interface between the inclusion and the metallic matrix functioning as defects in the passive film. The Cr-enriched zones formed around the Ce containing inclusion improved the corrosion resistance of the metallic matrix around the inclusions, which act as corrosion propagation sites. (author)

  19. Microhardness and Surface Integrity in Turning Process of Duplex Stainless Steel (DSS) for Different Cutting Conditions

    Science.gov (United States)

    Krolczyk, G.; Nieslony, P.; Legutko, S.

    2014-03-01

    The objective of the investigation was to identify microhardness of surface integrity (SI) after turning with wedges of coated sintered carbide. SI is important in determining corrosion resistance, and also in fatigue crack initiation. The investigation included microhardness analyses in dry and wet machining of duplex stainless steel. The microhardness of SI for various cutting speeds was compared. It has been shown that wet cutting leads to the decrease of SI hardening depth, while increasing the rounded cutting edge radius of the wedge increases the maximum microhardness values and the hardening depth. An infinite focus measurement machine has been used for the rounded cutting edge radius analysis. The study has been performed within a production facility during the production of electric motor parts and deep-well pumps as well as explosively cladded sheets.

  20. Effect of Continuous Cooling on Secondary Phase Precipitation in the Super Duplex Stainless Steel ZERON-100

    Science.gov (United States)

    Calliari, Irene; Bassani, Paola; Brunelli, Katya; Breda, Marco; Ramous, Emilio

    2013-12-01

    The precipitation of secondary phases in super duplex stainless steels (SDSS) is a subject of great relevance owing to their dangerous effects on both mechanical and corrosion-resistance properties. This paper examines the effect of continuous cooling after solution annealing treatment on secondary phase precipitation in the ZERON-100 SDSS. It considers the influence of cooling rate on volume fraction, morphology and chemical composition. It has been found that the formation of sigma and chi phases can be avoided only at cooling rates higher than 0.7 °C/s. In addition, at the lowest cooling rate the sigma phase amount approaches the equilibrium value, but the chi phase amount remains significantly low.

  1. Effects of Solution Annealing Temperature on the Galvanic Corrosion Behavior of the Super Duplex Stainless Steels

    Science.gov (United States)

    Lee, Jun-Seob; Jeon, Soon-Hyeok; Park, Yong-Soo

    2013-02-01

    This study investigated the active dissolution of super duplex stainless steel (SDSS) at various solution annealing temperatures. The active dissolutions of the α-phase and γ-phase were compared, and the effects of the surface area ratio on the active dissolutions of both phases were investigated. There were two peaks in the active-passive transition region in the potentiodynamic test in the modified green-death solution. The two peaks changed as the solution annealing temperature was increased from 1050 to 1150 °C. The solution annealing temperature difference affected the critical anodic current densities. This provides useful information for determining the appropriate solution annealing temperature in the modified green-death solution for SDSS.

  2. Influence of thermal history on corrosion resistance of duplex stainless steel linepipe

    International Nuclear Information System (INIS)

    Using NK CR22 duplex stainless steel 22%Cr-5.5%Ni-3%Mo, research has been carried out to analyze the influence of various thermal cycles on corrosion resistance. Special attention was paid to resistance to pitting corrosion in the weld heat affected zone (HAZ). The optimum range of welding heat input exists for the improvement of pitting corrosion resistance in the HAZ. Lower heat input brings about the deterioration of the resistance near the fusion line, higher one on the contrary degrades the HAZ apart from the fusion line. Both these phenomena are closely related to the sensitization of grain boundaries caused by the precipitation of chromium nitrides. Solution annealing is effective in giving pitting resistance in the HAZ. Annealing at temperatures over 11000C, increases susceptibility by sensitization of ferrite boundaries

  3. Role of surface finishing on pitting corrosion of a duplex stainless steel in seawater

    Science.gov (United States)

    Salah-Rousset, N. Ben; Chaouachi, M. A.; Chellouf, A.

    1996-04-01

    Localized corrosion of duplex UNS S32550 stainless steel in seawater was investigated in the laboratory and in field trials for several surface finish conditions: polished, ground, and sandblasted. Electrochemical data obtained by polarization curves showed that the smoother, polished surface had better characteristics (higher pitting and protection potentials) than the ground or sandblasted surfaces. However, despite its high degree of roughness, the sandblasted surface was the most resistant in field conditions, exhibiting the lowest number of sites attacked. Internal compressive stresses created by sandblasting seem also to have an “unsensitizing” effect on sensitized zones that exist in cast steel (due to repairs of mold defects), reducing its susceptibility to microbiologically influenced corrosion (MIC). Such stresses are not generated in polished or ground surfaces, and localized MIC attack can occur.

  4. Corrosion of 2205 Duplex Stainless Steel Weldment in Chloride Medium Containing Sulfate-Reducing Bacteria

    Science.gov (United States)

    Antony, P. J.; Singh Raman, R. K.; Kumar, Pradeep; Raman, R.

    2008-11-01

    Influence of changes in microstructure caused due to welding on microbiologically influenced corrosion of a duplex stainless steel was studied by exposing the weldment and parent metal to chloride medium containing sulfate-reducing bacteria (SRB). Identically prepared coupons (same area and surface finish) exposed to sterile medium were used as the control. Etching-type attack was observed in the presence of SRB, which was predominant in the heat-affected zone (HAZ) of the weldment. The anodic polarization studies indicated an increase in current density for coupon exposed to SRB-containing medium as compared to that obtained for coupon exposed to sterile medium. The scanning electron microscopy (SEM) observations after anodic polarization revealed that the attack was preferentially in the ferrite phase of HAZ of the weldment, whereas it was restricted to the austenite phase of the parent metal.

  5. Study of fatigue damage micromechanisms in a duplex stainless steel by complementary analysis techniques

    Energy Technology Data Exchange (ETDEWEB)

    El Bartali, Ahmed; Aubin, Veronique; Degallaix, Suzanne [Laboratoire de Mecanique de Lille, LML UMR CNRS Ecole Centrale de Lille, Villeneuve d' Ascq (France)

    2009-09-15

    The low-cycle fatigue (LCF) damage micromechanisms are studied in a duplex stainless steel at room temperature using complementary analysis techniques. Surface damage is observed in real-time with an in-situ microscopic device during a low-cycle fatigue test. Slip systems activated in each grain in each phase are identified from SEM photographs and EBSD measurements. The surface relief appeared at the end of the test is measured with an interferometric profilometer. Displacement and strain fields on the microstructural scale are calculated using DIC technique from surface images taken during cycling. Observations were combined to analyse damage mechanisms from slip marking appearance to strain localisation and crack initiation. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  6. Short fatigue cracks nucleation and growth in lean duplex stainless steel LDX 2101

    International Nuclear Information System (INIS)

    This work is focused on the fatigue damage of lean duplex stainless steels (LDSSs) LDX 2101. Special interest is placed on analyzing short fatigue crack behavior. In this sense, short crack initiation and growth during low cycle fatigue (LCF) and short crack nucleation during high cycle fatigue (HCF) of this LDSS have been studied. The active slip systems and their associated Schmid factors (SF) are determined using electron backscattered diffraction (EBSD). Additionally, the dislocation structure developed during cycling is observed by transmission electron microscopy (TEM). Regardless of the fatigue regime, LCF and HCF, short cracks nucleate along intrusion/extrusions in ferritic grains. Moreover, during the LCF phase boundaries decelerate short crack propagation. These results are rationalized by the hardness of the constitutive phases and the dependence of screw dislocation mobility in the ferrite phase on strain rate and stress amplitude

  7. Effect of hot deformation mode on the microstructure evolution of lean duplex stainless steel 2101

    International Nuclear Information System (INIS)

    Microstructure and crystallographic texture evolution of lean duplex stainless steel 2101 (LDX 2101) during single- and multi-pass hot compressions were studied by electron backscatter diffraction (EBSD). The flow curve characteristics of LDX 2101 were interpreted by coupling behaviors of the microstructure evolution in austenitic and ferric phases. The softening of both the phases during straining is caused by continuous dynamic recrystallization by the gradual transformation of low-angle grain boundaries into high-angle grain boundaries, without obvious changes in the phase ratio. The hot compression textures of the constituent phases show that the brass-type texture, which is typical of face-centered cubic materials with low stacking fault energy, is developed in the austenitic phase, and the rotated-cube texture is developed in the ferric phase. The differences in the microstructures and texture evolution features under different hot deformation modes can be explained by the differences in softening mechanisms

  8. Tribological study in roll forming of lean duplex stainless steel sheets

    DEFF Research Database (Denmark)

    Nielsen, Peter Søe; Nielsen, Morten Strogaard; Bay, Niels

    2012-01-01

    are relatively low and surface expansion is more or less non-existent, long roll forming production runs imply large sliding/contact lengths due to relative movement between steel strip and rolls. This requires an efficient tribological system to prevent pick-up formation on the forming tools. The......In roll forming a sheet metal strip undergoes deformation in several successive forming steps until the desired shape is reached. It is a very cost effective process to produce series of continuous profiles. Though roll forming is not considered a tribologically critical process, as process loads...... present work focus on tribological issues are galling and pick-up formation as well as tool life in roll forming of stainless duplex steel sheets. The roll forming process is exemplified by production of an s-shaped profile used in interlock carcass production for flexible pipes used in off-shore oil...

  9. Corrosion Fatigue Behavior of Duplex Stainless Steel in 3.5% Sodium Chloride Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The corrosion fatigue behavior of duplex stainless steel (DSS) was studied at different cyclic stress levels in 3.5%NaCl (mass fraction, so as the follows) solution (pH=7) at 50℃. The results showed that DSS was susceptible to pitting corrosion and corrosion fatigue. Both intergranluar corrosion cracking and transgranlular corrosion cracking initiated at the bottom of pitting holes. Furthermore, the corrosion fatigue properties of DSS in 3.5%NaCl solution may be relatived to complex electrochemical and mechanical coupling effects between the three phases (austenite, ferrite and martensite), where martensite and ferrite were anodic in the corrosion cell and could be prone to cracking under certain condition.

  10. Microtexture of constituent phases in a heavily warm- rolled and annealed duplex stainless steel

    Science.gov (United States)

    Zaid, M.; Bhattacharjee, P. P.

    2015-04-01

    Evolution of microtexture during isothermal annealing of a heavily warm-rolled Fe- 0.08%C-24.18%Cr-10.5%Ni duplex stainless steel (DSS) having approximately equal volume fraction of ferrite and austenite was investigated in the present work. The DSS was warm-rolled to ∼90% reduction in thickness at three different temperatures, namely, 225°C, 425°C and 625°C followed by isothermal annealing at 1175°C for different length of time. Austenite showed pure metal or copper type texture at different warm-rolling temperatures. In contrast, the texture of ferrite in different warm-rolled DSS revealed the presence of RD (RD//) and ND (ND//) fibers. The annealing texture of austenite showed retention of the deformation texture components while ferrite revealed strong RD-fiber.

  11. PREDICTION OF SURFACE ROUGHNESS IN END MILLING OPERATION OF DUPLEX STAINLESS STEEL USING RESPONSE SURFACE METHODOLOGY

    Directory of Open Access Journals (Sweden)

    S. D. PHILIP

    2015-03-01

    Full Text Available Response surface methodology has been used to study the effects of the machining parameters such as spindle speed, feed rate and axial depth of cut on surface roughness of duplex stainless steel in end milling operation. Dry milling experiments were conducted with three levels of spindle speed, feed rate and axial depth of cut. A mathematical model has been developed to predict the surface roughness in terms of the machining parameters using Box-Behnken design response surface methodology. The adequacy of the model was verified using analysis of variance. The prediction equation shows that the feed rate is the most important factor that influences the surface roughness followed by axial depth of cut and spindle speed. The validity of the model was verified by conducting the confirmation experiment.

  12. Surface Layer Investigation of a Shot-Peened Duplex Stainless Steel Utilizing X-ray Diffraction

    Science.gov (United States)

    Feng, Qiang; Wu, Xueyan; Jiang, Chuanhai; Xu, Zhou; Wu, Lihong

    2013-07-01

    Distributions of residual stresses and microstructure in the surface layers of shot-peened duplex stainless steel (DSS) S32205 were investigated. The results reveal that both compressive residual stresses (CRS) and microhardness increase with the enhancement of shot-peening (SP) intensity in the surface deformation layers. The maximum value of CRS of ferrite lies in the surface layer but that of austenite locates below the surface layer after SP. SP influence on the microstructure of DSS was studied using x-ray diffraction profiles, and the domain size and microstrain were calculated via Voigt method. After SP, the domain sizes are refined, and microstrain becomes severe at surface layers in both phases. On comparing the calculated results, it is found that the more evident domain size subdivision and the more serious microstrain increase in austenite than those in ferrite are due to the higher work hardening of austenite.

  13. Finite element modelling and characterization of friction welding on UNS S31803 duplex stainless steel joints

    Directory of Open Access Journals (Sweden)

    Mohammed Asif. M

    2015-12-01

    Full Text Available Solid state joining techniques are increasingly employed in joining duplex stainless steel materials due to their high integrity. Continuous drive friction welding is a solid state welding technique which is used to join similar and dissimilar materials. This joining technique is characterized by short cycle time, low heat input and narrow heat affected zones. The simulation becomes an important tool in friction welding because of short welding cycle. In the present work, a three dimensional non-linear finite element model was developed. The thermal history and axial shortening profiles were predicted using ANSYS, a software tool. This numerical model was validated using experimental results. The results show that the frictional heating stage of the process has more influence on temperature and upsetting stage has more impact on axial shortening. The knowledge of these parameters would lead to optimization of input parameters and improvement of design and machine tools.

  14. Decomposition and Precipitation Process During Thermo-mechanical Fatigue of Duplex Stainless Steel

    Science.gov (United States)

    Weidner, Anja; Kolmorgen, Roman; Kubena, Ivo; Kulawinski, Dirk; Kruml, Tomas; Biermann, Horst

    2016-05-01

    The so-called 748 K (475 °C) embrittlement is one of the main drawbacks for the application of ferritic-austenitic duplex stainless steels (DSS) at higher temperatures caused by a spinodal decomposition of the ferritic phase. Thermo-mechanical fatigue tests performed on a DSS in the temperature range between 623 K and 873 K (350 °C and 600 °C) revealed no negative influence on the fatigue lifetime. However, an intensive subgrain formation occurred in the ferritic phase, which was accompanied by formation of fine precipitates. In order to study the decomposition process of the ferritic grains due to TMF testing, detailed investigations using scanning and transmission electron microscopy are presented. The nature of the precipitates was determined as the cubic face centered G-phase, which is characterized by an enrichment of Si, Mo, and Ni. Furthermore, the formation of secondary austenite within ferritic grains was observed.

  15. Aging degradation of cast stainless steel: status and program

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Ayrault, G.

    1983-10-01

    A program has been initiated to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. The existing data are reviewed to determine the critical parameters that control the aging behavior and to define the objectives and scope of the investigation. The test matrices for microstructural studies and mechanical property measurements are presented. The initial experimental effort is focussed on characterizing the microstructure of long-term, low-temperature aged material. Specimens from three heats of cast CF-8 and CF-8M stainless steel aged for up to 70,000 h at 300, 350, and 400/sup 0/C were obtained from George Fisher Ltd., of Switzerland. Initial analyses reveal the formation of three different types of precipitates which are not ..cap alpha..'. An FCC phase, similar to the M/sub 23/C/sub 6/ precipitates, was present in all the long-term aged material. 15 references, 10 figures, 2 tables.

  16. Mechanism of hot-rolling crack formation in lean duplex stainless steel 2101

    Science.gov (United States)

    Feng, Zhi-hui; Li, Jing-yuan; Wang, Yi-de

    2016-04-01

    The thermoplasticity of duplex stainless steel 2205 (DSS2205) is better than that of lean duplex steel 2101 (LDX2101), which undergoes severe cracking during hot rolling. The microstructure, microhardness, phase ratio, and recrystallization dependence of the deformation compatibility of LDX2101 and DSS2205 were investigated using optical microscopy (OM), electron backscatter diffraction (EBSD), Thermo-Calc software, and transmission electron microscopy (TEM). The results showed that the phase-ratio transformations of LDX2101 and DSS2205 were almost equal under the condition of increasing solution temperature. Thus, the phase transformation was not the main cause for the hot plasticity difference of these two steels. The grain size of LDX2101 was substantially greater than that of DSS2205, and the microhardness difference of LDX2101 was larger than that of DSS2205. This difference hinders the transfer of strain from ferrite to austenite. In the rolling process, the ferrite grains of LDX2101 underwent continuous softening and were substantially refined. However, although little recrystallization occurred at the boundaries of austenite, serious deformation accumulated in the interior of austenite, leading to a substantial increase in hardness. The main cause of crack formation is the microhardness difference between ferrite and austenite.

  17. Mechanism of hot-rolling crack formation in lean duplex stainless steel 2101

    Institute of Scientific and Technical Information of China (English)

    Zhi-hui Feng; Jing-yuan Li; Yi-de Wang

    2016-01-01

    The thermoplasticity of duplex stainless steel 2205 (DSS2205) is better than that of lean duplex steel 2101 (LDX2101), which un-dergoes severe cracking during hot rolling. The microstructure, microhardness, phase ratio, and recrystallization dependence of the deforma-tion compatibility of LDX2101 and DSS2205 were investigated using optical microscopy (OM), electron backscatter diffraction (EBSD), Thermo-Calc software, and transmission electron microscopy (TEM). The results showed that the phase-ratio transformations of LDX2101 and DSS2205 were almost equal under the condition of increasing solution temperature. Thus, the phase transformation was not the main cause for the hot plasticity difference of these two steels. The grain size of LDX2101 was substantially greater than that of DSS2205, and the microhardness difference of LDX2101 was larger than that of DSS2205. This difference hinders the transfer of strain from ferrite to austenite. In the rolling process, the ferrite grains of LDX2101 underwent continuous softening and were substantially refined. However, although little recrystallization occurred at the boundaries of austenite, serious deformation accumulated in the interior of austenite, leading to a substantial increase in hardness. The main cause of crack formation is the microhardness difference between ferrite and austenite.

  18. Effect of Plastic Deformation on the Corrosion Behavior of a Super-Duplex Stainless Steel

    Science.gov (United States)

    Renton, Neill C.; Elhoud, Abdu M.; Deans, William F.

    2011-04-01

    The role of plastic deformation on the corrosion behavior of a 25Cr-7Ni super-duplex stainless steel (SDSS) in a 3.5 wt.% sodium chloride solution at 90 °C was investigated. Different levels of plastic strain between 4 and 16% were applied to solution annealed tensile specimens and the effect on the pitting potential measured using potentiodynamic electrochemical techniques. A nonlinear relationship between the pitting potential and the plastic strain was recorded, with 8 and 16% causing a significant reduction in average E p, but 4 and 12% causing no significant change when compared with the solution-annealed specimens. The corrosion morphology revealed galvanic interaction between the anodic ferrite and the cathodic austenite causing preferential dissolution of the ferrite. Mixed potential theory and the changing surface areas of the two phases caused by the plastic deformation structures explain the reductions in pitting potential at certain critical plastic strain levels. End-users and manufacturers should evaluate the corrosion behavior of specific cold-worked duplex and SDSSs using their as-produced surface finishes assessing in-service corrosion performance.

  19. Electrochemical evaluation of a corrosion fatigue failure mechanism in a duplex stainless steel

    Science.gov (United States)

    Stoudt, M. R.; Ricker, R. E.

    2004-08-01

    Laboratory corrosion fatigue studies on smooth and precracked samples indicated that two duplex stainless steels would have similar service lives in a paper-processing environment; but, in service, one of these alloys has exhibited premature failures. Since corrosion fatigue experiments had proven unable to detect this failure mechanism, electrochemical measurements and slow strain rate tensile tests were used to evaluate four alloy composition-dependent failure mechanism hypotheses. No significant differences were found in the dissolution rates or hydrogen fugacities produced when mechanical processes expose bare surface, and slow strain rate tensile tests found no indication of a difference in cracking susceptibility for the same hydrogen fugacity. Electrochemical experiments found that pits nucleate in one phase of the duplex microstructure at lower potentials in the failure prone alloy, but do not propagate beyond the microscopic dimensions of this phase. These microstructurally limited “micropits” were found to nucleate fracture in slow strain rate tensile tests, and examination of a service failure confirmed the presence of microscopic pits at crack initiation sites. The premature failures are attributed to the lower pitting resistance of the failure prone alloy, and the failure of laboratory experiments to predict this behavior is attributed to the slow kinetics of pit nucleation in these experiments. A laboratory testing methodology is suggested that will ensure detection of similar susceptibilities in future corrosion fatigue testing programs.

  20. Formation of NiAl intermetallic coatings on stainless steel by a conventional duplex process

    International Nuclear Information System (INIS)

    Nickel-aluminide coatings were formed on 403 stainless steel samples by a duplex process incorporating electro-deposition and diffusion coating. Nickel was deposited by conventional electroplating on some specimens to appropriate thickness. The uncoated and nickel-coated samples were then aluminized by a powder pack method. Process parameters including pack composition, temperature, coating and annealing cycles were optimized in terms of the intermetallic phases produced in the near surface layers. The coatings and interface regions were characterized by optical and scanning electron microscopy, x-ray diffraction, glow discharge spectroscopy, micro-hardness measurements and pin-on-disc wear testing. Experimental results indicate that deposition of nickel on 403 steel before aluminizing produced two distinct layers of NiAl and FeAl on the surface and below that, respectively. The formation of these phases depends on the coating and annealing temperatures. The intermetallic phase NiAl on steel substrate acts as an alumina forming material to increase the life of aluminized layer. The intermetallic coatings produced by this duplex process had dense structure and excellent adhesion to the substrate; these are suitable candidates for high temperature applications of steel components under oxidation and hot corrosion conditions. (author)

  1. Energy absorption behaviour of austenitic and duplex stainless steels in a crash box geometry

    Energy Technology Data Exchange (ETDEWEB)

    Ratte, E.; Bleck, W. [Dept. of Ferrous Metallurgy, RWTH Aachen Univ., Aachen (Germany); Leonhardt, S. [Honda R und D Europe (Deutschland), Offenbach/ Main (Germany); Franzen, M.; Urban, P. [Inst. fuer Kraftfahrwesen, RWTH Aachen Univ., Aachen (Germany)

    2006-09-15

    The improvement of the passive safety plays an important role in the development of new steels for automotive parts. At the same time aspects of weight reduction as well as the industrial feasibility have to be considered. Powered by these objectives, the development and application of new steel concepts for various purposes is promoted. For the present investigation especially weight reduction combined with an improvement of the passive safety are emphasised. As example one representative part of the body structure, the crash box, is considered. At the moment different steel grades (dual phase-, TRIP-and HSLA-steels) as well as fibre reinforced materials are applied. New materials for this special purpose have to exhibit outstanding formability, a high capacity to absorb energy during a possible crash and should be cost effective compared to already existing material concepts. During this project different grades of austenitic stainless steels with varying stability were compared to duplex stainless steels and a TRIP grade with regard to their possible application as crash-box material. The austenitic grades show excellent gradual formability according to their strength level. All of them exhibit an extraordinary strain hardening behaviour. The duplex grades show a lower formability but on a much higher yield level. Besides the determination of classical material data such as uni- and multi-axial flow curves, dynamic tensile tests and forming tests for the determination of forming limit curves were performed. The material data were used in the simulation of a drop tower test which is commonly used to evaluate the performance of different materials in car components. The results were then evaluated with regard to the absorbed energy, the folding behaviour and the resulting forces. (orig.)

  2. Effect of Microstructure on Mechanical Properties and Corrosion Resistance of 2205 Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Łabanowski Jerzy

    2015-01-01

    Full Text Available This paper presents results of the research on impact of microstructure of austenitic-ferritic steel of duplex type on its mechanical properties and susceptibility to stress corrosion cracking. As showed, improper processing technologies more and more often used in shipbuilding industry for plates and other half-finished products made of duplex steel may cause significant lowering their properties, which frequently makes their replacing necessary. Results of the tests on stress corrosion under tension with low strain rate (SSRT conducted in an inert and corrosion (boiling magnesium chloride environment, are presented. It was proved that even minor structural transformations taking place in 500°C ageing temperature lower corrosion resistance of the steel. Structural transformations occurring in 700°C temperature to a smaller extent influence susceptibility to stress corrosion of the steel, however they cause drastic drop in its plasticity.

  3. Microstructure and corrosion behavior of shielded metal arc-welded dissimilar joints comprising duplex stainless steel and low alloy steel

    Science.gov (United States)

    Srinivasan, P. Bala; Muthupandi, V.; Sivan, V.; Srinivasan, P. Bala; Dietzel, W.

    2006-12-01

    This work describes the results of an investigation on a dissimilar weld joint comprising a boiler-grade low alloy steel and duplex stainless steel (DSS). Welds produced by shielded metal arc-welding with two different electrodes (an austenitic and a duplex grade) were examined for their microstructural features and properties. The welds were found to have overmatching mechanical properties. Although the general corrosion resistance of the weld metals was good, their pitting resistance was found to be inferior when compared with the DSS base material.

  4. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

    Energy Technology Data Exchange (ETDEWEB)

    Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shamanian, Morteza [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandarian, Masoomeh [Department of Materials Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Zabolian, Azam [Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Szpunar, Jerzy A. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada)

    2015-08-15

    The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientation relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld

  5. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

    International Nuclear Information System (INIS)

    The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientation relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld

  6. Synthesis of nano-structured duplex and ferritic stainless steel powders by planetary milling: An experimental and simulation study

    Science.gov (United States)

    Gupta, Shalabh; Shashanka, R.; Chaira, D.

    2015-02-01

    Nano-structured duplex and ferritic stainless steel powders were prepared by planetary milling of elemental Fe, Ni and Cr powder compositions (duplex: 69Fe-18Cr-13Ni and ferritic:82Fe-17Cr-1Ni) in a dual drive planetary mill for 10 hours. The feasibility for solid solution formation of Cr and Ni in Fe matrix were studied. The samples were collected at regular time intervals and characterized for their morphological and phase analysis using X- Ray diffraction (XRD) and scanning electron microscopy (SEM). It has been observed that as the milling time increases crystallite size decreases and lattice strain increases. Thermodynamic aspects of milled stainless steel powders were performed using Miedema model. The theoretical values ΔH,ΔS and ΔG of and were calculated and were found to be -14.32kJ/mol, 6.93J/mol and -16.39 kJ/mol for duplex stainless steel and -2.81kJmol, 4.35Jmol and -4.11 kJ/mol for ferritic stainless steel respectively.

  7. Magnetic detection of sigma phase in duplex stainless steel UNS S31803

    Energy Technology Data Exchange (ETDEWEB)

    Tavares, S.S.M., E-mail: ssmtavares@terra.com.b [Universidade Federal Fluminense, Departamento de Engenharia Mecanica, PGMEC, Rua Passo da Patria, 156, CEP 24210-240, Niteroi (Brazil); Pardal, J.M.; Guerreiro, J.L. [Universidade Federal Fluminense, Departamento de Engenharia Mecanica, PGMEC, Rua Passo da Patria, 156, CEP 24210-240, Niteroi (Brazil); Gomes, A.M. [Universidade Federal do Rio de Janeiro, Instituto de Fisica (Brazil); Silva, M.R. da [Universidade Federal de Itajuba, Instituto de Ciencias (Brazil)

    2010-09-15

    Duplex stainless steels are high strength and corrosion resistant steels extensively used in the chemical and petrochemical industry. The best mechanical properties and corrosion resistance are obtained with a microstructure composed by equal parts of ferrite and austenite and free from tertiary phases. Sigma phase is one of these deleterious tertiary phases. In the present work different amounts of sigma phase were precipitated by heat treatments in a UNS S31803 stainless steel. Some specimens were cold rolled before sigma phase precipitation in order to evaluate the effect of deformation on the magnetic measurements. The amount of sigma phase was precisely determined by microscopy and image analysis for each heat treatment condition. The effects of sigma phase on the steel properties were investigated, confirming the detrimental effects of very small percentages on corrosion resistance and toughness. Two magnetic methods were used to detect sigma phase: magnetization saturation measurements in a Vibrating Sample Magnetometer and ferritoscope testing. Both methods were found to be sensitive to small percentages of sigma phase in the microstructure.

  8. Magnetic detection of sigma phase in duplex stainless steel UNS S31803

    Science.gov (United States)

    Tavares, S. S. M.; Pardal, J. M.; Guerreiro, J. L.; Gomes, A. M.; da Silva, M. R.

    2010-09-01

    Duplex stainless steels are high strength and corrosion resistant steels extensively used in the chemical and petrochemical industry. The best mechanical properties and corrosion resistance are obtained with a microstructure composed by equal parts of ferrite and austenite and free from tertiary phases. Sigma phase is one of these deleterious tertiary phases. In the present work different amounts of sigma phase were precipitated by heat treatments in a UNS S31803 stainless steel. Some specimens were cold rolled before sigma phase precipitation in order to evaluate the effect of deformation on the magnetic measurements. The amount of sigma phase was precisely determined by microscopy and image analysis for each heat treatment condition. The effects of sigma phase on the steel properties were investigated, confirming the detrimental effects of very small percentages on corrosion resistance and toughness. Two magnetic methods were used to detect sigma phase: magnetization saturation measurements in a Vibrating Sample Magnetometer and ferritoscope testing. Both methods were found to be sensitive to small percentages of sigma phase in the microstructure.

  9. Selective corrosion of duplex stainless steel. Pt. 1 Corrosion behaviour of duplex stainless steel X2CrNiMoN22-5-3 with special consideration of the microstructure

    International Nuclear Information System (INIS)

    This paper is dealing with investigations on interrelations between microstructure and corrosion behaviour of duplex stainless steel X2CrNiMoN22-5-3. With the application of conventional methods like Strauss- and Huey-test it is not possible to describe correctly the corrosion behaviour. In contrary, by means of the development of the electrochemical potentiodynamic reactivation (EPR) method it is possible to give a reliable proof of corrosion susceptibility. The knowledge about the corrosion of duplex stainless steel was intensified by fundamental investigation of interrelations between precipitations and corrosion behaviour. By means of numerous investigations on the microstructure by means of SEM and TEM secondary phases were analysed and quantified and depletion areas created by precipitations were characterized. (orig.)

  10. Law of mixture used to model the flow behavior of a duplex stainless steel at high temperatures

    International Nuclear Information System (INIS)

    In this investigation the flow curves of a duplex stainless steel were drawn by performing hot compression tests over a wide temperature range of 950–1200 °C and strain rates of 0.001–100 s−1. The flow curves of ferrite and austenite phases in the duplex structure were depicted by conducting similar hot compression tests on two steels that were cast and prepared with the same chemical compositions. The flow curves of the austenitic steel were found typical of dynamic recrystallization. They were successfully modeled by using the experimental exponential equation proposed by Cingara and McQueen. The flow curves of the ferritic steel were typical of dynamic recovery. They were modeled by the dislocation density evolution function proposed by Estrin and Meckning. Comparing the flow curves of three studied steels, it was found that the flow curves of the duplex steel were very similar and close to those of the ferrite steel. It was understood that in a duplex structure of ferrite and austenite the flow behavior is mostly controlled by the softer phase, i.e. ferrite. The law of mixture was modified to consider the strain partitioning between ferrite and austenite. The distribution coefficients of ferrite and austenite were described and determined at different deformation conditions. The results of modeling satisfactorily predicted the experimental curves. It was shown that the influence of austenite on the flow behavior of the duplex structure is almost low. However, it increases as strain rate or temperature rises. - Highlights: ► Flow curves of austenite and ferrite in the duplex steel were modeled separately. ► The flow behavior of the duplex steel is mostly controlled by ferrite. ► The effect of austenite on flow curve increases with temperature and strain rate. ► The flow curve of the duplex steel is modeled by the modified law of mixture

  11. Superficial integrity analysis in a super duplex stainless steel after turning

    Directory of Open Access Journals (Sweden)

    E.C. Bordinassi

    2006-08-01

    Full Text Available Purpose: Purpose of this paper was to study the main effects of the turning in the superficial integrity of theduplex stainless steel ASTM A890-Gr6A.Design/methodology/approach: The focus of the work was the finishing operations and a complete factorialplanning was used, with 2 levels and 5 factors. The tests were conducted on a turning center with carbidetools and the main entrances variables were: tool material class, feed rate, cutting depth, cutting speed andcutting fluid utilization. The answers analyzed were: micro structural analysis by optical microscopy and x-raydiffraction, cutting forces measurements by a piezoelectric dynamometer, surface roughness, residual stress byx-ray diffraction technique and the micro-hardness measurements.Findings: The results do not showed any changes in the micro structural of the material, even when the greatercutting parameters were used. All the other answers were correlated with the cutting parameters and its bettercombination was founded for the best superficial integrity. The smaller feed rate (0.1 mm/v, smaller cuttingspeed (110 m/min and the greater cutting depth (0.5 mm provided the smaller values for the tensile residualstress, the smaller surface roughness and the greater micro-hardness.Research limitations/implications: The correlation between all the answers was very difficult to analyzebecause there was great interaction between the factors, but for some data group it was possible.Originality/value: The paper contribute for the study of the super duplex stainless steel, considering that no oneresearches was founded for the studied topics in this material in witch presents different behavior in machiningwhen compared with another stainless steels.

  12. Study of corrosion behavior of a 22% Cr duplex stainless steel : influence of nano-sized chromium nitrides and exposure temperature

    OpenAIRE

    Bettini, Eleonora; Kivisäkk, Ulf; Leygraf, Christofer; Pan, Jinshan

    2013-01-01

    Chromium nitrides may precipitate in duplex stainless steels during processing and their influence on the corrosion behavior is of great importance for the steel performance. In this study, the influence of nano-sized quenched-in chromium nitrides on the corrosion behavior of a heat treated 2205 duplex stainless steel was investigated at room temperature and 50 °C (just above critical pitting temperature). The microstructure was characterized by SEM/EDS and AFM analyses, and quenched-in nitri...

  13. Long-term embrittlement of cast duplex stainless steels in LWR systems

    International Nuclear Information System (INIS)

    Charpy-impact, tensile. and fracture toughness data are presented for several heats of cast stainless steel that were aged up to 58,000 h at temperatures of 290--400 degrees C. Results indicate that thermal aging increases the tensile stress and decreases the fracture toughness of the materials. In general, CF-3 steels are the least sensitive to thermal aging embrittlement and CF-8M steels are the most sensitive. The increase in flow stress of fully aged cast stainless steels is ∼10% for CF-3 steels and ∼20% for CF-8 and CF-8M steels. The fracture toughness JIc and average tearing modulus for heats that are sensitive to thermal aging (e.g., CF-8M steels) are as low as ∼90 kJ/m2 and ∼60, respectively

  14. Study of corrosive effect of oil in super duplex stainless steels; Estudo do efeito corrosivo do petroleo em acos super duplex

    Energy Technology Data Exchange (ETDEWEB)

    Gusmao, E.F.; Azambuja, V.M. [IFES, Coordenadoria de Metalurgia, Vitoria, ES (Brazil); Santos, D.S. [Universidade Federal do Rio de Janeiro (PEMM/COPPE/UFRJ), RJ (Brazil). Pos-Graduacao em Engenharia Metalurgica e de Materiais

    2010-07-01

    The super duplex stainless steel was exposed in an environment at 75 degree C with oil for days, weeks and month to observe the change in mass. The corrosion leads to loss of weight of material which could harm the economy of a company, as this will have to stop production to replace the corroded part. Hence the great importance of studies on ways to mitigate the corrosion. There was a chemical attack by the reagent Behara and testing to study the quality of the protective coating after the tests with oil by electrochemical impedance. (author)

  15. The influence of oxygen partial pressure on the kinetics of duplex scale formation on 316 stainless steel

    International Nuclear Information System (INIS)

    A previous study of iron tracer diffusion in duplex scale grown on vacuum annealed 316 steel had suggested that Fe cation diffusion was slower in the outer Fe3O4 layer than in the inner spinel. In order to obtain additional information on the location of the rate controlling step during duplex oxidation of 18 Cr-8 Ni type stainless steels, vacuum annealed 316 steel was oxidized at 6000C in atmospheres of controlled oxygen partial pressure covering the whole of the Fe3O4 stability range at that temperature. An oxygen partial pressure dependence of the primary parabolic rate of duplex scale formation of ksub(p) varies as Psub(O2)sup(0.135) was observed, providing further evidence that the rate controlling process is located in the outer Fe3O4 layer. (author)

  16. Effect of Aging Treatment on the Sensitization of Fe-Cr-Mn-N Stainless Steels

    International Nuclear Information System (INIS)

    In this work, the effects of aging treatment on the precipitation and mechanical properties of Fe-Cr-Mn-N stainless steels were studied. Experimental alloys were designed by the change of Creq/Nieq ratio, and two kinds of alloys having a austenitic phase and a duplex(austenite + ferrite) phase were manufactured. Optical microscope, scanning electron microscope, transmission electron microscope, and XRD were used to identify the precipitates formed by aging treatment. Mechanical properties were measured using techniques of a hardness test, a tensile test, and an impact test. In austenitic Fe-Cr-Mn-N steel, carbide and/or nitride were first precipitated in grain boundary by aging and then the increased aging time made intragranular precipitations which showed lamellar structures and grew from grain boundary into grain. Hardness, yield strength, and tensile strength were slightly increased, and the elongation and impact energy were largely decreased by aging treatment. However, duplex stainless steel showed the ferrite decomposition to sigma phase and austenite Il phase as like in case of Fe-Cr-Ni steels. In case of duplex Fe-Cr-Mn-N steels, the effects of aging treatment on the hardness, yield strength, and tensile strength were relatively small, but its effects were strong on the decrease of elongation and impact energy

  17. Corrosion resistance of duplex stainless steel subjected to long-term annealing in the spinodal decomposition temperature range

    Energy Technology Data Exchange (ETDEWEB)

    Lo, K.H., E-mail: KHLO@umac.mo [Department of Electromechanical Engineering, University of Macau, Macau (China); Kwok, C.T.; Chan, W.K.; Zeng, D. [Department of Electromechanical Engineering, University of Macau, Macau (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Long-term DLEPR data on duplex stainless steel. Black-Right-Pointing-Pointer Spinodal decomposition remains unabated even after 15,000 h of annealing. Black-Right-Pointing-Pointer Effect of long-term annealing on healing has been investigated. - Abstract: The effect of thermal annealing up to 15,000 h between 300 Degree-Sign C and 500 Degree-Sign C on the corrosion resistance of the duplex stainless steel (DSS) 7MoPLUS has been investigated by using the DLEPR test. Spinodal decomposition in 7MoPLUS is unabated even after annealing for 15,000 h and no healing has been observed. The possible healing mechanisms in this temperature range (back diffusion of Cr atoms from the Cr-rich ferrite ({alpha}{sub Cr}) and diffusion of Cr atoms from the austenite) and its absence in the present steel have been discussed.

  18. Aging degradation of cast stainless steels: Effects on mechanical properties

    International Nuclear Information System (INIS)

    A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water operating conditions. Mechanical property data are presented from Charpy-impact, tensile, and J-R curve tests for several heats of cast stainless steel aged up to 10,000 h at 450, 400, 350, 320, and 2900C. The results indicate that thermal aging increases the tensile strength and decreases the impact energy, J/sub IC/, and tearing modulus of the steels. Also, the ductile-to-brittle transition curve shifts to higher temperatures. The fracture toughness results are consistent with the Charpy-impact data, i.e., the relative reduction in J/sub IC/ is similar to the relative decrease in impact energy. The ferrite content and concentration of C in the steel have a strong effect on the overall process of low-temperature embrittlement. The low-carbon CF-3 steels are the most resistant and Mo-containing CF-8M steels are most susceptible to embrittlement. Weakening of the ferrite/austenite phase boundaries by carbide precipitates has a significant effect on the kinetics and extent of embrittlement of the high-carbon CF-8 and CF-8M steels, particularly after aging at temperatures ≥4000C. The influence of N content and distribution of ferrite on loss of toughness are discussed. The data also indicate that existing correlations do not accurately represent the embrittlement behavior over the temperature range 280 to 4500C, i.e., extrapolation of high-temperature data to reactor temperatures may not be valid for some compositions of cast stainless steel

  19. Effect of W substitution for Mo on stress corrosion cracking behavior of 25Cr-7Ni duplex stainless steel

    International Nuclear Information System (INIS)

    The effect of W substitution for Mo in duplex stainless steel (DSS) was investigated with respect to microstructure and stress corrosion cracking behavior. Homogenizing treatment was performed at 1100.deg.C for 10 minutes, while aging treatment was performed at 900.deg.C with different holding times. In homogenized condition, regardless of W substitution, all the specimens had the nearly equal volume-ratio of ferrite and austenite, and had no secondary phase precipitation. On aging, the W modification on suppression of secondary phase precipitation was very effective. Total amount of secondary phase precipitates was greatly reduced in the W-modified DSS in the early stage of the ageing treatment comparing to the commercial grade DSS without W modification. However, this effect was reduced rapidly as the aging time increased. Stress corrosion cracking(SCC) was examined in boil-ing 42% MgCl2 solution by slow strain rate test(SSRT) and constant load test (CLT). Under the homogenized condition, the beneficial effect of W was clearly observed at the low applied stress levels where the electrochemical action plays a dominant role. In the commercial grade DSS without W modification, the crack propagated in a trans-phase mode,whereas in the W-modified DSS, the crack propagated in a mixed mode of trans-phase and inter-phase due to barrier effect of austenite phase against crack growth. Under the aged condition, the signification improvement in SCC resistance of the aged DSS specimens with W modification resulted from increase in toughness due to a relatively small amount of the brittle secondary phase precipitates. However, the cracks propagated in a trans-phase mode in the DSS specimens regardless of W modification

  20. Effect of gadolinium addition on the corrosion, wear, and neutron absorbing behaviors of duplex stainless steel sheet

    Science.gov (United States)

    Baik, Youl; Choi, Yong; Moon, Byung M.; Sohn, Dong S.; Bogdanov, S. G.; Pirogov, A. N.

    2015-11-01

    In order to develop the neutron absorbing and shield materials, a hot-rolled 0.02%-Gd duplex stainless steel was prepared with 55 vol. % of ferrite and 45 vol. % of austenite. The σ phase with an average grain size of 9-11 μm in austenitic (γ) grains tended to be elongated parallel to the rolling direction, with (100) poles concentrated towards the normal direction, and (110) poles located between the normal and radial directions (ND and RD, respectively). Most of the gadolinium existed as sub-micro-meter-sized Gd2O3 and GdCrO3 precipitates. The yield strength, ultimate tensile strength, elongation, and microhardness of the 0.02%-Gd duplex stainless steel were 522.8 MPa, 700.2 MPa, 38.1%, and 258.5-314.7 HV, respectively. The friction coefficient and wear resistance were 3.11 and 0.004 mg/kg/cycle, respectively. The corrosion potential and corrosion rate of the 0.02%-Gd duplex stainless steel were-0.448 V SHE and 1.263 × 10-3 A/cm2 for 1M-HCl,-0.544 V SHE and 2.619 × 10-3 A/cm2 for 1M-NaCl,-0.299 V SHE and 1.469 × 10-3 A/cm2 for 1M-H2SO4, and-0.607 V SHE and 2.295 × 10-3 A/cm2 for synthetic water, respectively. The coefficient of neutron transmission for the 0.02%-Gd duplex stainless steel sheet of 2 mm thickness at neutron beam wavelength of 0.48 nm was 0.6.

  1. Evaluation of the low corrosion resistant phase formed during the sigma phase precipitation in duplex stainless steels

    OpenAIRE

    Kobayashi Darlene Yuko; Wolynec Stephan

    1999-01-01

    The duplex stainless steels, having a volumetric fraction of 50% ferrite and 50% austenite, conciliate high corrosion resistance with good mechanical properties. But, in many circumstances different phase transformations may occur, such as that responsible for sigma phase precipitation, which make the steel susceptible to localized corrosion. During the sigma phase precipitation a new austenitic phase is formed with a very low corrosion resistance. In the present research the composition of t...

  2. Effect of Free Surface on the Stability of Individual Retained Austenite Grains in a Duplex Stainless Steel

    Science.gov (United States)

    He, B. B.; Huang, M. X.; Ngan, A. H. W.; van der Zwaag, S.

    2014-10-01

    The present work explored the effect of free surface on the stability of individual austenite grains in a duplex stainless steel. It was found that martensitic transformation took place automatically in the retained austenite grain when a free surface was introduced. This is due to the fact that the martensite nucleation energy barrier can be lowered to a thermally surmountable value as the strain energy induced by martensitic transformation is largely lowered when the matrix constraints were removed.

  3. NUMERICAL 2D MODELING OF PLASTIC DEFORMATION OF DUPLEX STAINLESS STEEL X2CRNIMON25-07

    Czech Academy of Sciences Publication Activity Database

    Náhlík, Luboš

    Bratislava : Slovak University of Technology, 2004 - (Jančo, R.), s. 316 ISBN 80-227-2030-5. [Applied Mechanics 2004 /6./. Kočovce (SK), 22.03.2004-25.03.2004] R&D Projects: GA ČR GP106/04/P084 Institutional research plan: CEZ:AV0Z2041904 Keywords : plastic deformation * duplex stainless steel * numerical modeling Subject RIV: JG - Metallurgy

  4. Effect of different Mo contents on tensile and corrosion behaviors of CD4MCU cast duplex stainless steels

    International Nuclear Information System (INIS)

    In the present study, the effect of Mo contents on the microstructure, tensile and corrosion behaviors of as-solutionized CD4MCU cast duplex stainless steel was examined. The polarization test was conducted in 3.5% NaCl +5% H2SO4 aqueous solution for general corrosion resistance and the slow strain rate tests were also conducted in air and 3.5% NaCl+5% H2SO4 aqueous solution to study the Stress Corrosion Cracking (SCC) of the present alloy. A substantial microstructural evolution of CD4MCU cast duplex stainless steel was observed with different Mo contents, which in turn affected the tensile and corrosion behaviors significantly. The beneficial effect of Mo on improving the corrosion and the SCC resistances was largely overwhelmed by this variation of microstructural characteristics. The relationship between the microstructural evolution and the tensile and corrosion behavior of CD4MCU cast duplex stainless steels with different Mo contents was discussed based on the optical and SEM micrographic and fractographic observations

  5. Clean cast steel technology. Determination of transformation diagrams for duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chumbley, S. L. [Iowa State Univ., Ames, IA (United States)

    2005-09-01

    Duplex stainless steels (DSS) constitute both ferrite and austenite as a matrix. Such a microstructure confers a high corrosion resistance with favorable mechanical properties. However, intermetallic phases such as sigma ( can also form during casting or high-temperature processing and can degrade the properties of the DSS. This research was initiated to develop time-temperature-transformation (TTT) and continuous-cooling- transformation (CCT) diagrams of two types of cast duplex stainless steels, CD3MN (Fe 22Cr-5Ni-Mo-N) and CD3MWCuN (Fe-25Cr-7Ni-Mo-W-Cu-N), in order to understand the time and temperature ranges for intermetallic phase formation. The alloys were heat treated isothermally or under controlled cooling conditions and then characterized using conventional metallographic methods that included tint etching, and also using electron microscopy (SEM, TEM) and wavelength dispersive spectroscopy (WDS). The kinetics of intermetallic-phase ( formation were analyzed using the Johnson-Mehl-Avrami (JMA) equation in the case of isothermal transformations and a modified form of this equation in the case of continuous cooling transformations, The rate of intermetallic-phase formation was found to be much faster in CD3MWCuN than CD3MN due mainly to differences in the major alloying contents such as Cr, Ni and Mo. To examine in more detail the effects of these elements of the phase stabilities, a series of eight steel castings was designed with the Cr, Ni and Mo contents systematically varied with respect to the nominal composition of CD3MN. The effects of varying the contents of alloying additions on the formation of intermetallic phases were also studied computationally using the commercial thermodynamic software package, Thermo-Calc. In general, was stabilized with increasing Cr addition and by increasing Mo addition. However, a delicate balance among Ni and other minor elements such as N and Si also exists. Phase equilibria in DSS can be affected by local

  6. The induction of hyperthermia in rabbit liver by means of duplex stainless steel thermoseeds

    International Nuclear Information System (INIS)

    To determine the heating characteristics of needle-shaped duplex stainless steel thermoseeds, and to evaluate their effectiveness in the induction of hyperthermia in rabbit liver. Thermoseeds of the two different shapes, L-shaped for single doses of hyperthermia and I-shaped for in-vitro study and repeated hyperthermic induction, were prepared. For the in-vitro study, an I-shaped thermoseed 0.23 mm in diameter and 25 mm long was placed inside a plastic tube filled with water. Heat was applied for 30 minutes within an induction magnetic field, and during this time changes in temperature were recorded using three thermocouples. For the in-vivo study, fifteen New Zealand white rabbits were divided into five equal groups. An I-shaped or L-shaped thermoseed was inserted in each rabbit's liver, and then placed within the center of the magnetic induction coil during a 30-minute period of hyperthermia. The rabbits in the first group were sacrificed immediately after hyperthermia was induced once, while those in the other groups were sacrificed at 1, 3, and 7 days, respectively, also after one induction. The remaining three rabbits were sacrificed 4 days after three consecutive daily treatment sessions. The resected segments of liver were subsequently evaluated histopathologically for the extent of coagulation necrosis caused by heating of the thermoseed. The in-vitro study demonstrated that the temperature in the thermoseed, which was 25.9. deg. C before heating and 54.8 .deg. C after heating, rose rapidly at first but progressively less rapidly as time elapsed. Light microscopic examination of the rabbits' livers revealed coagulation necrosis and infiltration by inflammatory cells around the insertion site of the thermoseed. The maximum diameter of coagulation necrosis was 2.81±1.68 mm, and this occurred in the rabbits that were sacrificed 7 days after heat induction. Needle-shaped duplex stainless steel thermoseeds show temperature-dependent-type heating characteristics

  7. Low temperature aging of a duplex steel DIN 1.4462

    International Nuclear Information System (INIS)

    Duplex stainless steels (DSS) are an important and expanding class of stainless steels with a noticeable combination of mechanical properties and resistance to corrosion, due to their two phase austenite-ferrite structure. The ferrite provides high mechanical and corrosion resistance, while the austenite supplies ductility and uniform resistance to corrosion. This family of steels, however, becomes brittle when exposed to intermediate temperatures, from 300oC to 500oC, which limits their applications. In the ferrite phase of these alloys the solution is to develop a spinodal decomposition with iron and chromium rich regions called '475oC embrittlement'. The sharp drop in the toughness and ductility that can occur in the material makes more research about its response to aging at intermediate temperatures necessary in order to determine their reliability under these conditions. There are studies on the effects of aging on the development of mechanical properties in different types of steels, but the effects on the properties of fatigue have not been studied extensively and the few existing reports focus on the development of the properties of a first generation aged DSS steel. This work presents a study on the behavior of a DIN 1.4462 steel submitted to aging at temperatures from 400oC to 515oC. Microscopy and hardness measurements determined the provisional evolution of the aging; while cyclic tests determined how this affects the material's life in fatigue. The austenite does not noticeably change in hardness, but the ferrite's hardness continuously increases at all temperature ranges studied, with a maximum of around 480oC. The fatigue properties with low numbers of cycles after aging for 100 hours at 475oC do not differ noticeably from the behavior without aging, while the cyclic hardening-softening curves show heavy hardening caused by the aging that increases the flow limit as well as the saturation stress(CW)

  8. Effect of Heat Treatment on Corrosion and Stress Corrosion Cracking of S32205 Duplex Stainless Steel in Caustic Solution

    Science.gov (United States)

    Bhattacharya, Ananya; Singh, Preet M.

    2009-06-01

    Duplex stainless steels (DSSs) have generally performed very well in caustic environments. However, some corrosion and stress corrosion cracking (SCC) of DSSs have been reported in different pulp mill environments employing caustic solutions. Studies have shown that the corrosion and SCC susceptibility of DSSs depend on the alloy composition and microstructure of the steel. In this study, the effect of a sulfide-containing caustic environment (pulping liquor) and material properties (DSS alloy composition and microstructure) on the corrosion and SCC of DSSs was evaluated. During metal fabrication processes, localized areas of DSSs may be exposed to different temperatures and cooling rates, which may lead to changes in the microstructure in these regions. This change in microstructure, in turn, may affect the general and localized corrosion or SCC susceptibility of the affected area as compared to the rest of the metal. Hence, the effect of different annealing and aging temperatures as well as cooling rates on the microstructure and corrosion behavior of S32205 DSSs in caustic environment was evaluated. The results showed that changes in the microstructure of S32205 DSSs due to selected heat treatments did not have a significant effect on the general corrosion susceptibility of the steel in caustic environment, but its SCC susceptibility varied with changes in microstructures.

  9. Metallurgical and Corrosion Characterization of POST Weld Heat Treated Duplex Stainless Steel (uns S31803) Joints by Friction Welding Process

    Science.gov (United States)

    Asif M., Mohammed; Shrikrishna, Kulkarni Anup; Sathiya, P.

    2016-02-01

    The present study focuses on the metallurgical and corrosion characterization of post weld heat treated duplex stainless steel joints. After friction welding, it was confirmed that there is an increase in ferrite content at weld interface due to dynamic recrystallization. This caused the weldments prone to pitting corrosion attack. Hence the post weld heat treatments were performed at three temperatures 1080∘C, 1150∘C and 1200∘C with 15min of aging time. This was followed by water and oil quenching. The volume fraction of ferrite to austenite ratio was balanced and highest pit nucleation resistance were achieved after PWHT at 1080∘C followed by water quench and at 1150∘C followed by oil quench. This had happened exactly at parameter set containing heating pressure (HP):40 heating time (HT):4 upsetting pressure (UP):80 upsetting time (UP):2 (experiment no. 5). Dual phase presence and absence of precipitates were conformed through TEM which follow Kurdjumov-Sachs relationship. PREN of ferrite was decreasing with increase in temperature and that of austenite increased. The equilibrium temperature for water quenching was around 1100∘C and that for oil quenching was around 1140∘C. The pit depths were found to be in the range of 100nm and width of 1.5-2μm.

  10. 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

  11. Mechanical Properties of Super Duplex Stainless Steel 2507 after Gas Phase Thermal Precharging with Hydrogen

    Science.gov (United States)

    San Marchi, C.; Somerday, B. P.; Zelinski, J.; Tang, X.; Schiroky, G. H.

    2007-11-01

    Thermal precharging of super duplex stainless steel 2507 with 125 wppm hydrogen significantly reduced tensile ductility and fracture toughness. Strain-hardened 2507 exhibited more severe ductility loss compared to the annealed microstructure. The reduction of area (RA) was between 80 and 85 pct for both microstructures in the noncharged condition, while reductions of area were 25 and 46 pct for the strain-hardened and annealed microstructures, respectively, after hydrogen precharging. Similar to the effect of internal hydrogen on tensile ductility, fracture toughness of strain-hardened 2507 was lowered from nearly 300 MPa m1/2 in the noncharged condition to less than 60 MPa m1/2 in the hydrogen-precharged condition. While precharging 2507 with hydrogen results in a considerable reduction in ductility and toughness, the absolute values are similar to high-strength austenitic steels that have been tested under the same conditions, and which are generally considered acceptable for high-pressure hydrogen gas systems. The fracture mode in hydrogen-precharged 2507 involved cleavage cracking of the ferrite phase and ductile fracture along oblique planes in the austenite phase, compared to 100 pct microvoid coalescence in the absence of hydrogen. Predictions from a strain-based micromechanical fracture toughness model were in good agreement with the measured fracture toughness of hydrogen-precharged 2507, implying a governing role of austenite for resistance to hydrogen-assisted fracture.

  12. Effect of thermal treatments on the wear behaviour of duplex stainless steels

    International Nuclear Information System (INIS)

    Duplex stainless steel (DSS) is a family of steels characterized by two-phase microstructure with similar percentages of ferrite (α) and austenite (γ).Their attractive combination of mechanical properties and corrosion resistance has increased its use in last decades in the marine and petrochemical industries. Nevertheless, an inappropriate heat treatment can induce the precipitation of secondary phases which affect directly their mechanical properties and corrosion resistance. There are few works dealing with the influence of heat treatments on wear behaviour of these steels in the literature. For instances, this paper aims to determine wear kinetic and sliding wear volume developed as a function of heat treatment conditions. Therefore, the samples were heat treated from 850 deg. C to 975 deg.C before sliding wear tests. These wear tests were carried out using ball on disk technique at constant sliding velocity and different sliding distances. Two methodologies were used to calculate the wear volume: weight loss and area measurement using a simplified contact model. Microstructural observations showed the presence of sigma phase for all studied conditions. The formation kinetics of this phase is faster at 875 deg. C and decrease at higher temperatures. Results related to wear showed that the hardness introduced due to the presence of sigma phase plays an important role on wear behaviour for this steel. It was observed also that wear rates decreased when increasing the percentage of sigma phase on the microstructure.

  13. Effect of silver on microstructure and antibacterial property of 2205 duplex stainless steel.

    Science.gov (United States)

    Yang, Sheng-Min; Chen, Yi-Chun; Pan, Yeong-Tsuen; Lin, Dong-Yih

    2016-06-01

    In this study, 2205 duplex stainless steel (DSS) was employed to enhance the antibacterial properties of material through silver doping. The results demonstrated that silver-doped 2205 DSS produces an excellent bacteria-inhibiting effect against Escherichia coli and Staphylococcus aureus. The antibacterial rates were 100% and 99.5%, respectively. Because the mutual solubility of silver and iron is very low in both the solid and liquid states, a silver-rich compound solidified and dispersed at the ferrite/austenite interface and the ferrite, austenite, and secondary austenite phases in silver-doped 2205 DSS. Doping 2205 DSS with silver caused the Creq/Nieq ratio of ferrite to decrease; however, the lower Creq/Nieq ratio promoted the rapid nucleation of γ2-austenite from primary α-ferrite. After 12h of homogenisation treatment at 1200°C, the solubility of silver in the γ-austenite and α-ferrite phases can be increased by 0.10% and 0.09%, respectively. Moreover, silver doping was found to accelerate the dissolution of secondary austenite in a ferrite matrix during homogenisation. PMID:27040232

  14. Evolutions of Microstructure and Properties During Cold Rolling of 19Cr Duplex Stainless Steel

    Science.gov (United States)

    Ran, Qingxuan; Xu, Wanjian; Wu, Zhaoyu; Li, Jun; Xu, Yulai; Xiao, Xueshan; Hu, Jincheng; Jiang, Laizhu

    2016-07-01

    Evolutions of microstructure, mechanical, and corrosion properties of 19Cr (Fe-18.9Cr-10.1Mn-0.3Ni-0.261N-0.030C-0.5Si) duplex stainless steel have been investigated during cold rolling at room temperature. Dislocation slip dominated deformation mode of ferrite phase. However, deformation mechanism of austenite phase was different with the increasing cold-rolling reductions. Dislocation slip and strengthening effect of twin boundaries caused pile-up phenomenon at the initial deformation stage. When the amount of cold-rolling reduction attained greater than 50 pct, induced α'-martensite appeared in deformed austenite phase. Hardness of austenite phase was higher than that of the deformed ferrite because of its higher strengthening effect during cold-rolling process. Cold-rolling deformation caused deterioration of the pitting corrosion resistance in 3.5 wt pct NaCl aqueous solution. Pitting corrosion always initiated in the ferrite phase and the phase boundary in the solution-treated alloy. Additional pitting holes appeared in deformed austenite phase because of the decrease in corrosion resistance caused by dislocation accumulation and induced α'-martensite.

  15. Multiobjective optimization of friction welding of UNS S32205 duplex stainless steel

    Directory of Open Access Journals (Sweden)

    P.M. Ajith

    2015-06-01

    Full Text Available The present study is to optimize the process parameters for friction welding of duplex stainless steel (DSS UNS S32205. Experiments were conducted according to central composite design. Process variables, as inputs of the neural network, included friction pressure, upsetting pressure, speed and burn-off length. Tensile strength and microhardness were selected as the outputs of the neural networks. The weld metals had higher hardness and tensile strength than the base material due to grain refinement which caused failures away from the joint interface during tensile testing. Due to shorter heating time, no secondary phase intermetallic precipitation was observed in the weld joint. A multi-layer perceptron neural network was established for modeling purpose. Five various training algorithms, belonging to three classes, namely gradient descent, genetic algorithm and Levenberg–Marquardt, were used to train artificial neural network. The optimization was carried out by using particle swarm optimization method. Confirmation test was carried out by setting the optimized parameters. In conformation test, maximum tensile strength and maximum hardness obtained are 822 MPa and 322 Hv, respectively. The metallurgical investigations revealed that base metal, partially deformed zone and weld zone maintain austenite/ferrite proportion of 50:50.

  16. 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.

  17. 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.

  18. Surface properties and activation energy of superplastically carburized duplex stainless steel

    International Nuclear Information System (INIS)

    A new surface carburizing technique which combines superplastic phenomenon and carburizing process called superplastic carburizing (SPC) was introduced and compared with conventional carburizing (CC) process. Thermomechanically treated duplex stainless steel (DSS) with a fine grain microstructure that exhibits superplasticity was used as the superplastic material. SPC was carried out at temperatures of 1198-1248 K and a compression rate of 1 x 10-4 s-1 for various durations. Metallographic studies revealed that a carbon layer with a uniform, dense and smooth morphology formed on all carburized specimens. The case depth of the carbon layer was between 50.8 and 159.1 μm. A remarkable increase in surface hardness was observed in the range 389.9-1129.0 HV. Activation energy for SPC was determined as 183.4 kJ mol-1, which is lower compare to CC process. The results indicate that SPC accelerates the diffusion of carbon atoms into the surface of DSS, thus increasing the thickness of the carburized layer and the surface hardness, at lower activation energy.

  19. Effect of thermal treatments on the wear behaviour of duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Fargas, G; Mestra, A; Anglada, M; Mateo, A, E-mail: antonio.manuel.mateo@upc.edu [Center for Structural Integrity and Reliability of Materials, CIEFMA Dpt. Materials Science and Metallurgical Engineering, Universitat Politecnica de Catalunya, UPC, Av. Diagonal 647, 08028 Barcelona (Spain)

    2009-09-15

    Duplex stainless steel (DSS) is a family of steels characterized by two-phase microstructure with similar percentages of ferrite ({alpha}) and austenite ({gamma}).Their attractive combination of mechanical properties and corrosion resistance has increased its use in last decades in the marine and petrochemical industries. Nevertheless, an inappropriate heat treatment can induce the precipitation of secondary phases which affect directly their mechanical properties and corrosion resistance. There are few works dealing with the influence of heat treatments on wear behaviour of these steels in the literature. For instances, this paper aims to determine wear kinetic and sliding wear volume developed as a function of heat treatment conditions. Therefore, the samples were heat treated from 850 deg. C to 975 deg.C before sliding wear tests. These wear tests were carried out using ball on disk technique at constant sliding velocity and different sliding distances. Two methodologies were used to calculate the wear volume: weight loss and area measurement using a simplified contact model. Microstructural observations showed the presence of sigma phase for all studied conditions. The formation kinetics of this phase is faster at 875 deg. C and decrease at higher temperatures. Results related to wear showed that the hardness introduced due to the presence of sigma phase plays an important role on wear behaviour for this steel. It was observed also that wear rates decreased when increasing the percentage of sigma phase on the microstructure.

  20. Critical pitting and repassivation temperatures for duplex stainless steel in chloride solutions

    Energy Technology Data Exchange (ETDEWEB)

    Deng Bo; Jiang Yiming; Gong Jia; Zhong Cheng; Gao Juan [Department of Material Science, Fudan University, Shanghai 200433 (China); Li Jin [Department of Material Science, Fudan University, Shanghai 200433 (China)], E-mail: jinli@fudan.edu.cn

    2008-06-30

    Both the critical pitting temperature (CPT) and critical repassivation temperature (T{sub r}) for two kinds of duplex stainless steels (DSS, namely UNS S31803 and UNS S32750) were investigated in 1 mol/L NaCl solution using the cyclic thermammetry method. Potentiodynamic anodic polarization technique was employed to validate the cyclic thermammetry technique. In addition, the site of pitting nucleated preferentially on the DSS had been confirmed by scanning electron microscopy (SEM). The results demonstrated that there exhibits a hysteresis loop in cyclic thermammetry curve, revealing that the propagating pits could repassivate during the cooling half-cycle. The CPT and T{sub r} for UNS S31803 were 59.6 deg. C and 36.5 deg. C, whilst the CPT and T{sub r} for UNS S32750 were 87.5 deg. C and 70.5 deg. C, respectively. Pitting was always observed preferentially in the austenite phase. The results can be partially explained based on the changes in chemical composition of ferrite and austenite phases. Moreover, a semi-quantitative model is proposed to explain the existence of T{sub r}.

  1. SnO2:F Coated Duplex Stainless Steel for PEM Fuel Cell Bipolar Plates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H.; Turner, J. A.

    2008-01-01

    Duplex 2205 stainless steel was deposited with 0.6 {micro}m thick SnO2:F coating; coated steel was characterized for PEMFC bipolar plate application. Compared with bare alloy, interfacial contact resistance (ICR) values of the coated 2205 steel are higher. SnO2:F coating adds its own resistance to the air-formed film on the steel. In a PEMFC anode environment, a current peak of ca. 25 {micro}A/cm2 registered at ca. 30 min for coated 2205 steel. It stabilized at ca. 2.0 {approx} -1.0 {micro}A/cm2. This peak is related to the complicated process of coating dissolution and oxide-layer formation. Anodic-cathodic current transfer occurred at ca. 200 min polarization. In a PEMFC cathode environment, current was stable immediately after polarization. The stable current was ca. 0.5 {approx} 2.0 {micro}A/cm2 during the entire polarization period. AES depth profiles with tested samples and ICP analysis with the tested solutions confirmed the excellent corrosion resistance of the SnO2:F coated 2205 alloy in simulated PEMFC environments.

  2. Characterization of a cold-rolled 2101 lean duplex stainless steel.

    Science.gov (United States)

    Bassani, Paola; Breda, Marco; Brunelli, Katya; Mészáros, Istvan; Passaretti, Francesca; Zanellato, Michela; Calliari, Irene

    2013-08-01

    Duplex stainless steels (DSS) may be defined as a category of steels with a two-phase ferritic-austenitic microstructure, which combines good mechanical and corrosion properties. However, these steels can undergo significant microstructural modification as a consequence of either thermo-mechanical treatments (ferrite decomposition, which causes σ- and χ-phase formation and nitride precipitation) or plastic deformation at room temperature [austenite transformation into strain-induced martensite (SIM)]. These secondary phases noticeably affect the properties of DSS, and therefore are of huge industrial interest. In the present work, SIM formation was investigated in a 2101 lean DSS. The material was subjected to cold rolling at various degrees of deformation (from 10 to 80% thickness reduction) and the microstructure developed after plastic deformation was investigated by electron backscattered diffraction, X-ray diffraction measurements, and hardness and magnetic tests. It was observed that SIM formed as a consequence of deformations higher than ~20% and residual austenite was still observed at 80% of thickness reduction. Furthermore, a direct relationship was found between microstructure and magnetic properties. PMID:23721654

  3. Microstructural evolution and pitting resistance of annealed lean duplex stainless steel UNS S32304

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ziying [Department of Materials Science, Fudan University, Shanghai 200433 (China); Key Laboratory of Ecophysics, Department of Physics, Shihezi University, Shihezi 832003 (China); Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters, Yili Normal University, Yining 835000 (China); Han Dong; Jiang Yiming; Shi Chong [Department of Materials Science, Fudan University, Shanghai 200433 (China); Li Jin, E-mail: jinli@fudan.edu.cn [Department of Materials Science, Fudan University, Shanghai 200433 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer The relationship between pitting corrosion resistance and annealing temperature for UNS S32304 was systemically studied. Black-Right-Pointing-Pointer The specimens annealed at 1080 Degree-Sign C for 1 h, quenched in water exhibit the best pitting corrosion resistance. Black-Right-Pointing-Pointer The relationship between microstructural evolution and pitting resistance of annealed UNS S32304 was discussed in detail. Black-Right-Pointing-Pointer The pitting corrosion resistance is consistent with pitting resistance equivalent number of weaker phase for UNS S32304 alloy. - Abstract: The effect of annealing temperature in the range from 1000 to 1200 Degree-Sign C on the pitting corrosion behavior of duplex stainless steel UNS S32304 was investigated by the potentiodynamic polarization and potentiostatic critical pitting temperature techniques. The microstructural evolution and pit morphologies were studied using a scanning electron microscopy with energy dispersive X-ray spectroscopy. The results demonstrated that the nucleation of metastable pits transformed from austenite phase to ferrite phase with the increasing annealing temperature. As the annealing temperature increased, the pitting corrosion resistance firstly increased and then decreased. The highest pitting corrosion resistance was obtained at 1080 Degree-Sign C with the highest critical pitting temperature value and pitting nucleation resistance. The results could be well explained by the microstructural evolution of ferrite and austenite phases induced by annealing treatment.

  4. Influence of nitrogen in the shielding gas on corrosion resistance of duplex stainless steel welds

    Science.gov (United States)

    Bhatt, R. B.; Kamat, H. S.; Ghosal, S. K.; de, P. K.

    1999-10-01

    The influence of nitrogen in shielding gas on the corrosion resistance of welds of a duplex stainless steel (grade U-50), obtained by gas tungsten arc (GTA) with filler wire, autogenous GTA (bead-on-plate), electron beam welding (EBW), and microplasma techniques, has been evaluated in chloride solutions at 30 °C. Pitting attack has been observed in GTA, electron beam welding, and microplasma welds when welding has been carried out using pure argon as the shielding gas. Gas tungsten arc welding with 5 to 10% nitrogen and 90 to 95% argon, as the shielding gas, has been found to result in an improved pitting corrosion resistance of the weldments of this steel. However, the resistance to pitting of autogenous welds (bead-on-plate) obtained in pure argon as the shielding gas has been observed to remain unaffected. Microscopic examination, electron probe microanalysis (EPMA), and x-ray diffraction studies have revealed that the presence of nitrogen in the shielding gas in the GTA welds not only modifies the microstructure and the austenite to ferrite ratio but also results in a nearly uniform distribution of the various alloying elements, for example, chromium, nickel, and molybdenum among the constitutent phases, which are responsible for improved resistance to pitting corrosion.

  5. Effect of thermal treatments on the wear behaviour of duplex stainless steels

    Science.gov (United States)

    Fargas, G.; Mestra, A.; Anglada, M.; Mateo, A.

    2009-09-01

    Duplex stainless steel (DSS) is a family of steels characterized by two-phase microstructure with similar percentages of ferrite (α) and austenite (γ).Their attractive combination of mechanical properties and corrosion resistance has increased its use in last decades in the marine and petrochemical industries. Nevertheless, an inappropriate heat treatment can induce the precipitation of secondary phases which affect directly their mechanical properties and corrosion resistance. There are few works dealing with the influence of heat treatments on wear behaviour of these steels in the literature. For instances, this paper aims to determine wear kinetic and sliding wear volume developed as a function of heat treatment conditions. Therefore, the samples were heat treated from 850 °C to 975 °C before sliding wear tests. These wear tests were carried out using ball on disk technique at constant sliding velocity and different sliding distances. Two methodologies were used to calculate the wear volume: weight loss and area measurement using a simplified contact model. Microstructural observations showed the presence of sigma phase for all studied conditions. The formation kinetics of this phase is faster at 875 °C and decrease at higher temperatures. Results related to wear showed that the hardness introduced due to the presence of sigma phase plays an important role on wear behaviour for this steel. It was observed also that wear rates decreased when increasing the percentage of sigma phase on the microstructure.

  6. Microbiologically Influenced Corrosion of 2707 Hyper-Duplex Stainless Steel by Marine Pseudomonas aeruginosa Biofilm

    Science.gov (United States)

    Li, Huabing; Zhou, Enze; Zhang, Dawei; Xu, Dake; Xia, Jin; Yang, Chunguang; Feng, Hao; Jiang, Zhouhua; Li, Xiaogang; Gu, Tingyue; Yang, Ke

    2016-02-01

    Microbiologically Influenced Corrosion (MIC) is a serious problem in many industries because it causes huge economic losses. Due to its excellent resistance to chemical corrosion, 2707 hyper duplex stainless steel (2707 HDSS) has been used in the marine environment. However, its resistance to MIC was not experimentally proven. In this study, the MIC behavior of 2707 HDSS caused by the marine aerobe Pseudomonas aeruginosa was investigated. Electrochemical analyses demonstrated a positive shift in the corrosion potential and an increase in the corrosion current density in the presence of the P. aeruginosa biofilm in the 2216E medium. X-ray photoelectron spectroscopy (XPS) analysis results showed a decrease in Cr content on the coupon surface beneath the biofilm. The pit imaging analysis showed that the P. aeruginosa biofilm caused a largest pit depth of 0.69 μm in 14 days of incubation. Although this was quite small, it indicated that 2707 HDSS was not completely immune to MIC by the P. aeruginosa biofilm.

  7. The Influence of Hydrogen on the Microstructure and Dynamic Strength of Lean Duplex Stainless Steel

    Science.gov (United States)

    Silverstein, Ravit; Glam, Benny; Eliezer, Dan; Moreno, Daniel; Eliezer, Shalom

    2015-06-01

    In this research the dynamic strength of lean duplex stainless steel (LDS) with and without hydrogen was investigated. The LDS was chosen since it has a mixed structure of ferrite (BCC) and austenite (FCC) which allows an attractive combination of high strength and plasticity. Data collection was performed by VISAR and metallurgical analysis by post mortem observation. In addition, a thermal desorption process (TDS) was carried out in order to observe the influence of hydrogen charging on LDS crystal structure and to determine the hydrogen trapping mechanism before and after the plate impact experiments. Several assessments can be made based on the results of this study. TDS analysis revealed that even after hydrogen desorption, some hydrogen remained trapped in the austenitic phase causing a small lattice expansion. After impact, a brittle spall mechanism was seen, which occurred through crack progression along both phases grain boundaries. It was found that even small hydrogen content affects the dynamic strength of LDS. The relation between the microstructure and the dynamic strength of the LDS in the presence of hydrogen will be discussed. This work was supported by the Pazi foundation.

  8. -Doped Titanium Dioxide Photocatalytic Films on 304 Stainless Steel by Duplex Treatment

    Science.gov (United States)

    Tian, Linhai; Qian, Laohong; Yao, Xiaohong; Li, Xiaoying

    2014-05-01

    Sn4+-doped titanium dioxide photocatalytic films were synthesized on 304 stainless steel (SS) by a duplex treatment. The SS substrates were alloyed with titanium (Ti) through cathodic-arc ion plating followed by a microarc oxidation (MAO) treatment in different electrolytes. Field-emission scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy were used to characterize the films surface morphology, crystalline phase, and composition, respectively. Photocatalytic activity was measured using an UV-Vis spectrophotometer. It was found that the films with a porous structure are mainly composed of TiO2, which exists in an anatase and rutile state. Furthermore, small quantities of SnO2 have been found in the Sn4+-doped titanium dioxide films. The fraction of anatase varies with the MAO time and electrolytes, whereas the pore size remains the similar with the same MAO current intensity and density and the surface roughness increases slightly with increasing MAO time. It was also found that the photocatalytic activity of the Sn4+-doped porous film improved, and the film synthesized with a shorter MAO time in a lower Na2SnO3-containing electrolyte is superior to the films with longer MAO times and higher Na2SnO3 concentrations.

  9. Erosive Wear Behavior of High-Alloy Cast Iron and Duplex Stainless Steel under Mining Conditions

    Science.gov (United States)

    Yoganandh, J.; Natarajan, S.; Kumaresh Babu, S. P.

    2015-09-01

    Centrifugal pumps used in the lignite mines encounter erosive wear problems, leading to a disastrous failure of the pump casings. This paper attempts to evaluate the erosive wear resistance of Ni-Hard 4, high-chromium iron, and Cast CD4MCu duplex stainless steel (DSS), for mining conditions. The prepared test coupons were subjected to an erosion test by varying the impingement velocity and the angle of impingement, under two different pH conditions of 3 and 7, which pertained to the mining conditions. XRD analysis was carried out to confirm the phases present in the alloy. The eroded surface was subjected to SEM analysis to identify the erosion mechanisms. The surface degradation of Ni-Hard 4 and high-chromium iron came from a low-angle abrasion with a grooving and plowing mechanism at a low angle of impingement. At normal impingement, deep indentations resulted in lips and crater formations, leading to degradation of the surface in a brittle manner. A combined extrusion-forging mechanism is observed in the CD4MCu DSS surface at all the impingement angles.

  10. Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

    Science.gov (United States)

    Momeni, Amir; Kazemi, Shahab; Bahrani, Ali

    2013-10-01

    The hot deformation characteristics of 1.4462 duplex stainless steel (DSS) were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100°C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-Hollomon parameter ( Z) increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6.×1015 (ln Z=35.5), a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction (EBSD) confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.

  11. Delaminations by Cleavage Cracking in Duplex Stainless Steels at Sub-zero Temperatures

    Science.gov (United States)

    Pilhagen, Johan; Sandström, Rolf

    2013-10-01

    Impact toughness testing was conducted on 10 and 30 mm plates of 2205 together with a 30 mm plate of LDX 2101® duplex stainless steel (DSS). The testing temperatures were between 153 K (-120 °C) and room temperature. Interrupted fracture toughness tests of the 10 mm plate and a 50 mm plate of 2205 were also performed. The conclusion from the fractographic investigation was that the delaminations that occur in hot-rolled DSSs were cleavage fractures. The toughness anisotropy can be explained by the cleavage fracture and the appearance of the microstructure. The result from the interrupted fracture toughness test revealed that the delaminations initiated prior to the maximum force plateau and propagated ahead of the stable crack growth during testing. Estimated upper limit for the fracture delamination initiation toughness at sub-zero temperatures for the 2205 base metal according to the crack-tip opening displacement method was 28 to 61 μm for the 10 mm plate, 70 to 106 μm for the 30 mm plate and below 100 μm for the 50 mm plate.

  12. Double-Sided Single-Pass Submerged Arc Welding for 2205 Duplex Stainless Steel

    Science.gov (United States)

    Luo, Jian; Yuan, Yi; Wang, Xiaoming; Yao, Zongxiang

    2013-09-01

    The duplex stainless steel (DSS), which combines the characteristics of ferritic steel and austenitic steel, is used widely. The submerged arc welding (SAW) method is usually applied to join thick plates of DSS. However, an effective welding procedure is needed in order to obtain ideal DSS welds with an appropriate proportion of ferrite (δ) and austenite (γ) in the weld zone, particularly in the melted zone and heat-affected zone. This study evaluated the effectiveness of a high efficiency double-sided single-pass (DSSP) SAW joining method for thick DSS plates. The effectiveness of the converse welding procedure, characterizations of weld zone, and mechanical properties of welded joint are analyzed. The results show an increasing appearance and continuous distribution feature of the σ phase in the fusion zone of the leading welded seam. The converse welding procedure promotes the σ phase to precipitate in the fusion zone of leading welded side. The microhardness appears to significantly increase in the center of leading welded side. Ductile fracture mode is observed in the weld zone. A mixture fracture feature appears with a shear lip and tears in the fusion zone near the fusion line. The ductility, plasticity, and microhardness of the joints have a significant relationship with σ phase and heat treatment effect influenced by the converse welding step. An available heat input controlling technology of the DSSP formation method is discussed for SAW of thick DSS plates.

  13. Degradation detection of materials used in nuclear power plant components applying probe-type eddy current sensor. Pt. 1. Detection of thermal embrittlement in duplex stainless steel

    International Nuclear Information System (INIS)

    Material degradation caused by aging of nuclear power plant components includes fatigue, neutron irradiation embrittlement and thermal embrittlement of duplex stainless steel. Detecting of these degradation in an earlier stage for prevention of possible accidents may contribute to improve availability and reliability of nuclear power plants. Eddy current testing method has been widely used in nondestructive testing field because the apparatus and sensor are light in weight and compact in size. It also allows testing without contact and provides excellent recordability because eddy current is generated by electromagnetic induction. In this research, material degradation by thermal embrittlement of duplex stainless steel was measured with eddy current changing frequency in steps of 1 kHz, output signal from coil was processed by phase detection technique and displayed as a trajectory on complex plane. By comparing the trajectory of a non-degraded material with that of a degraded material, degradation was evaluated quantitatively. Drawing such trajectory enabled us to capture the eddy current behavior totally and thus to select a proper method of evaluation. (author)

  14. Investigations on structure–property relationships of activated flux TIG weldments of super-duplex/austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Devendranath Ramkumar, K., E-mail: ramdevendranath@gmail.com; Bajpai, Ankur; Raghuvanshi, Shubham; Singh, Anshuman; Chandrasekhar, Aditya; Arivarasu, M.; Arivazhagan, N.

    2015-06-25

    This research work articulated the effect of SiO{sub 2} flux assisted tungsten inert gas (TIG) welding on the microstructure and mechanical properties of marine grade stainless steel weldments, such as super-duplex stainless steel (UNS S32750) and austenitic stainless steel (AISI 316L). The studies showed that the use of flux decreased the heat input required to obtain complete penetration. Microstructure studies revealed the presence of ferrite at the heat affected zone of AISI 316L and the fusion zone which obviated the hot cracking tendency. Tensile studies corroborated that the joint strength was sufficiently greater than that of the parent metals. Impact toughness slightly impoverished owing to the presence of large platelets of Widmanstätten austenite in the fusion zone. The study also explored the structure–property relationships of the flux assisted weldments using the combined techniques of optical and scanning electron microscopy analysis. Owing to the better metallurgical and mechanical properties, this study recommends the use of SiO{sub 2} flux for joining the dissimilar metals involving austenitic and super-duplex stainless steels.

  15. Investigations on structure–property relationships of activated flux TIG weldments of super-duplex/austenitic stainless steels

    International Nuclear Information System (INIS)

    This research work articulated the effect of SiO2 flux assisted tungsten inert gas (TIG) welding on the microstructure and mechanical properties of marine grade stainless steel weldments, such as super-duplex stainless steel (UNS S32750) and austenitic stainless steel (AISI 316L). The studies showed that the use of flux decreased the heat input required to obtain complete penetration. Microstructure studies revealed the presence of ferrite at the heat affected zone of AISI 316L and the fusion zone which obviated the hot cracking tendency. Tensile studies corroborated that the joint strength was sufficiently greater than that of the parent metals. Impact toughness slightly impoverished owing to the presence of large platelets of Widmanstätten austenite in the fusion zone. The study also explored the structure–property relationships of the flux assisted weldments using the combined techniques of optical and scanning electron microscopy analysis. Owing to the better metallurgical and mechanical properties, this study recommends the use of SiO2 flux for joining the dissimilar metals involving austenitic and super-duplex stainless steels

  16. Austenitic and duplex stainless steels in simulated physiological solution characterized by electrochemical and X-ray photoelectron spectroscopy studies.

    Science.gov (United States)

    Kocijan, Aleksandra; Conradi, Marjetka; Schön, Peter M

    2012-04-01

    A study of oxide layers grown on 2205 duplex stainless steel (DSS) and AISI 316L austenitic stainless steel in simulated physiological solution is presented here in order to establish the possibility of replacement of AISI 316 L with 2205 DSS in biomedical applications. The results of the potentiodynamic measurements show that the extent of the passive range significantly increased for DSS 2205 compared to AISI 316L stainless steel. Cyclic voltammetry was used to investigate electrochemical processes taking place on the steel surfaces. Oxide layers formed by electrochemical oxidation at different oxidation potentials were studied by X-ray photoelectron spectroscopy, and their compositions were analyzed as a function of depth. The main constituents on both the investigated materials were Cr- and Fe-oxides. Atomic force microscopy topography studies revealed the higher corrosion resistance of the DSS 2205 compared to the AISI 316L under the chosen experimental conditions. PMID:22331841

  17. Irradiation response of delta ferrite in as-cast and thermally aged cast stainless steel

    Science.gov (United States)

    Li, Zhangbo; Lo, Wei-Yang; Chen, Yiren; Pakarinen, Janne; Wu, Yaqiao; Allen, Todd; Yang, Yong

    2015-11-01

    To enable the life extension of Light Water Reactors (LWRs) beyond 60 years, it is critical to gain adequate knowledge for making conclusive predictions to assure the integrity of duplex stainless steel reactor components, e.g. primary pressure boundary and reactor vessel internal. Microstructural changes in the ferrite of thermally aged, neutron irradiated only, and neutron irradiated after being thermally aged cast austenitic stainless steels (CASS) were investigated using atom probe tomography. The thermal aging was performed at 400 °C for 10,000 h and the irradiation was conducted in the Halden reactor at ˜315 °C to 0.08 dpa (5.6 × 1019 n/cm2, E > 1 MeV). Low dose neutron irradiation at a dose rate of 5 × 10-9 dpa/s was found to induce spinodal decomposition in the ferrite of as-cast microstructure, and further to enhance the spinodal decomposition in the thermally aged cast alloys. Regarding the G-phase precipitates, the neutron irradiation dramatically increases the precipitate size, and alters the composition of the precipitates with increased, Mn, Ni, Si and Mo and reduced Fe and Cr contents. The results have shown that low dose neutron irradiation can further accelerate the degradation of ferrite in a duplex stainless steel at the LWR relevant condition.

  18. Burst pressure of super duplex stainless steel pipes subject to combined axial tension, internal pressure and elevated temperature

    International Nuclear Information System (INIS)

    The burst pressure of super duplex stainless steel pipe is measured under combined internal pressure, external axial tension and elevated temperature up to 160 °C. The experimental results are compared with existing burst pressure prediction models. Existing models are found to provide reasonable estimate of the burst pressure at room temperature but significantly over estimate the burst pressure at elevated temperature. Increasing externally applied axial stress and elevated temperature reduces the pressure capacity. - Highlights: • The burst pressure of super duplex steel is measured under combined loading. • Effect of elevated temperature on burst pressure is determined. • Burst pressure decreases with increasing temperature. • Existing models are reliable at room temperature. • Burst strength at elevated temperature is lower than predictions

  19. The role of nitrogen in improving pitting corrosion resistance of high-alloy austenitic and duplex stainless steel welds

    International Nuclear Information System (INIS)

    The effects of nitrogen alloyed shielding gas on weld nitrogen content and pitting corrosion resistance of super austenitic (6%Mo) and super duplex stainless steels have been studied with special emphasis on microsegregation behaviour of Cr, Mo and N. The measurements performed with the 6%Mo steel indicate that all these elements segregate interdendritically in the fully austenitic weld metal. With nitrogen addition to the shielding gas the enrichment of nitrogen to the interdendritic regions is more pronounced than to the dendrite cores due to which the pitting corrosion resistance of the dendrite cores increases only marginally. In the super duplex steel welds nitrogen enriches in austenite increasing its pitting corrosion resistance more effectively. In these welds the pitting corrosion resistance of the ferrite phase remains lower. (orig.)

  20. The role of nitrogen in improving pitting corrosion resistance of high-alloy austenitic and duplex stainless steel welds

    Energy Technology Data Exchange (ETDEWEB)

    Vilpas, M. [VTT Manuf. Technol. (Finland); Haenninen, H. [Helsinki Univ. of Technol., Espoo (Finland). Lab. of Eng. Mater.

    1999-07-01

    The effects of nitrogen alloyed shielding gas on weld nitrogen content and pitting corrosion resistance of super austenitic (6%Mo) and super duplex stainless steels have been studied with special emphasis on microsegregation behaviour of Cr, Mo and N. The measurements performed with the 6%Mo steel indicate that all these elements segregate interdendritically in the fully austenitic weld metal. With nitrogen addition to the shielding gas the enrichment of nitrogen to the interdendritic regions is more pronounced than to the dendrite cores due to which the pitting corrosion resistance of the dendrite cores increases only marginally. In the super duplex steel welds nitrogen enriches in austenite increasing its pitting corrosion resistance more effectively. In these welds the pitting corrosion resistance of the ferrite phase remains lower. (orig.)

  1. Role of secondary austenite on corrosion and stress corrosion cracking of sensitized duplex stainless steel weldments

    International Nuclear Information System (INIS)

    The role of secondary austenite on corrosion and stress corrosion cracking in high temperature water for sensitized duplex stainless steel weldment was investigated using transmission electron microscopy and fractography. Pitting potential measurements, 10% oxalic acid tests (ASTM A262A), Strauss tests (ASTM A262E) and Huey tests (ASTM A262C) were carried out for the corrosion assessment. For stress corrosion cracking, the slow strain rate testing (SSRT) was carried out at 562K with 8 ppm dissolved oxygen under 8 MPa at a strain rate of 4.17x10-6s-1. Volume fraction of γphase decreased with increasing peak temperature and the grain size of the γphase increased with increasing peak temperature. The amount of precipitation of Cr2N at the grain boundary and in the grain increased with increasing peak temperature. The region around Cr2N showed intergranular corrosion. For the sensitization at 923K for 72ks, σphase precipitated and secondary γphases (named γ* phase) appeared between primary γphase and σphase. The γ* phases were predominantly corroded and the pitting potentials were low. Stress corrosion cracking in high temperature water hardly occurred for the solution-treated specimen. The reduction in area of the specimen sensitized at 923K for 72ks was much lower than that of the solution-treated specimens and decreased with decreasing peak temperature, because the γ* phases near the M23C6 and σphase were predominantly corroded and dissolved. (author)

  2. Influence o the microstructure of duplex stainless steels on their failure characteristics during hot deformation

    Directory of Open Access Journals (Sweden)

    Reis G.S.

    2000-01-01

    Full Text Available Two types of duplex stainless steels were deformed by torsion at a temperature range of 900 to 1200 °C and strain rate of 1.0 s-1 and their final microstructures were observed. The austenite volume fraction of steel A (26.5Cr - 4.9Ni - 1.6Mo is approximately 25% at room temperature, after conventional annealing, while that of steel B (24Cr - 7.5Ni - 2.3Mo is around 55%. Experimental data show that steel A is ductile at high temperatures and displays low ductility at low temperatures, while steel B has low ductility in the entire range of temperatures studied. At high temperatures, steel A is essentially ferritic and shows dynamic recrystallized grains after deformation. When steel A is strained at low temperatures and displays low austenite volume fraction, microstructural observations indicate that failure is triggered by grain boundary sliding due to the formation of an austenite net structure at the ferrite grain boundaries. At intermediate volume fraction, when austenite forms a dispersed second-phase in steels A and B, failure begins at the ferrite/ferrite boundaries since some of the new ferrite grains may become immobilized by the austenite particles. When steel B is strained at volume fraction of around 50% of austenite and both phases percolate the microstructure, failure occurs after low straining as a consequence of the different plastic behaviors of each of the phases. The failure characteristics of both steels are correlated not only with the volume fraction of austenite but also with its distribution within the ferrite matrix, which limits attainable strain without failure.

  3. Effect of N addition on tensile and corrosion behaviors of CD4MCU cast duplex stainless steels

    Science.gov (United States)

    Son, Jinil; Kim, Sangshik; Lee, Jehyun; Choi, Byunghak

    2003-08-01

    The effect of N addition on the microstructure, tensile, and corrosion behaviors of CD4MCU (Fe-25Cr-5Ni-2.8Cu-2Mo) cast duplex stainless steel was examined in the present study. The slow strain rate tests were also conducted at a nominal strain rate of 1 × 10-6/s in air and 3.5 pct NaCl+5 pct H2SO4 solution for studying the stress corrosion cracking (SCC) behavior. It was observed that the volume fraction of austenitic phase in CD4MCU alloy varied from 38 to 59 pct with increasing nitrogen content from 0 to 0.27 wt. pct. The tensile behavior of CD4MCU cast duplex stainless steels, which tended to vary significantly with different N contents, appeared to be strongly related to the volume changes in ferritic and austenitic phases, rather than the intrinsic N effect. The improvement in the resistance to general corrosion in 3.5 pct NaCl+5 pct H2SO4 aqueous solution was notable with 0.13 pct N addition. The further improvement was not significant with further N addition. The resistance to SCC of CD4MCU cast duplex stainless steels in 3.5 pct NaCl+5 pct H2SO4 aqueous solution, however, increased continuously with increasing N content. The enhancement in the SCC resistance was believed to be related to the volume fraction of globular austenitic colonies, which tended to act as barriers for the development of initial pitting cracks in the ferritic phase into the sharp ones.

  4. The Effect of Constant and Pulsed Current Gas Tungsten Arc Welding on Joint Properties of 2205 Duplex Stainless Steel to 316L Austenitic Stainless Steel

    Science.gov (United States)

    Neissi, R.; Shamanian, M.; Hajihashemi, M.

    2016-05-01

    In this study, dissimilar 316L austenitic stainless steel/2205 duplex stainless steel (DSS) joints were fabricated by constant and pulsed current gas tungsten arc welding process using ER2209 DSS as a filler metal. Microstructures and joint properties were characterized using optical and electron scanning microscopy, tensile, Charpy V-notch impact and micro-hardness tests, and cyclic polarization measurements. Microstructural observations confirmed the presence of chromium nitride and delta ferrite in the heat-affected zone of DSS and 316L, respectively. In addition, there was some deviation in the austenite/ferrite ratio of the surface welding pass in comparison to the root welding pass. Besides having lower pitting potential, welded joints produced by constant current gas tungsten arc welding process, consisted of some brittle sigma phase precipitates, which resulted in some impact energy reduction. The tensile tests showed high tensile strength for the weld joints in which all the specimens were broken in 316L base metal.

  5. The Effect of Constant and Pulsed Current Gas Tungsten Arc Welding on Joint Properties of 2205 Duplex Stainless Steel to 316L Austenitic Stainless Steel

    Science.gov (United States)

    Neissi, R.; Shamanian, M.; Hajihashemi, M.

    2016-04-01

    In this study, dissimilar 316L austenitic stainless steel/2205 duplex stainless steel (DSS) joints were fabricated by constant and pulsed current gas tungsten arc welding process using ER2209 DSS as a filler metal. Microstructures and joint properties were characterized using optical and electron scanning microscopy, tensile, Charpy V-notch impact and micro-hardness tests, and cyclic polarization measurements. Microstructural observations confirmed the presence of chromium nitride and delta ferrite in the heat-affected zone of DSS and 316L, respectively. In addition, there was some deviation in the austenite/ferrite ratio of the surface welding pass in comparison to the root welding pass. Besides having lower pitting potential, welded joints produced by constant current gas tungsten arc welding process, consisted of some brittle sigma phase precipitates, which resulted in some impact energy reduction. The tensile tests showed high tensile strength for the weld joints in which all the specimens were broken in 316L base metal.

  6. Effect of cooling rate and forced convection on as-cast structure of 2205 duplex stainless steel

    OpenAIRE

    Cheng Zhang; Hong-gang Zhong; Cong-sen Wu

    2015-01-01

    To forecast the as-cast structure and ferrite-austenite phase ratio of 2205 duplex stainless steel (DSS), the effects of cooling rate and forced convection were observed in a high-vacuum resistance furnace in which the forced convection was created by the rotation of the crucible. The as-cast structure of all 2205 DSS samples is full equiaxed grains, and the microstructure consists of a great amount of desirable intra-granular austenite inside the continuous ferrite grain matrix, besides Widm...

  7. Effect of Microstructure on Atmospheric-Induced Corrosion of Heat-treated Grade 2205 and 2507 Duplex Stainless Steels

    OpenAIRE

    Cem Örnek, Amina H. Ahmed, Dirk Engelberg

    2012-01-01

    Atmospheric-induced corrosion tests under MgCl2 salt deposits were carried out on duplex stainless steel grade 2205 and 2507. As-received and 750°C heat-treated material conditions were investigated, and selected micro-structural sites targeted with salt-laden deposits to determine their corrosion response. Deposits were wetted under controlled climatic conditions at 80°C and 40% relative humidity. Observations of micro-structural attack indicated the presence of net anodic and net cathodic s...

  8. Effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel - Part 1

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Soon-Tae; Jeon, Soon-Hyeok; Lee, In-Sung [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Park, Yong-Soo [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)], E-mail: yongsoop@yonsei.ac.kr

    2010-06-15

    To elucidate the effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel, a metallographic examination, potentiodynamic and potentiostatic polarization tests, a SEM-EDS and a SAM analysis of inclusion, austenite phase and ferrite phase were conducted. The addition of rare earth metals to the base alloy led to the formation of (Mn, Cr, Si, Al, Ce) oxides and (Mn, Cr, Si, Ce) oxides, which improved the resistance to pitting corrosion and caused a decrease in the preferential interface areas for the initiation of the pitting corrosion.

  9. Effect of annealing treatment on microstructure evolution and the associated corrosion behavior of a super-duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Deng, B.; Jiang, Y.M.; Gao, J. [Department of Materials Science, Fudan University, Handan Street, Shanghai 200433 (China); Li, J., E-mail: jinli@fudan.edu.c [Department of Materials Science, Fudan University, Handan Street, Shanghai 200433 (China)

    2010-03-18

    The influence of annealing temperature on the pitting corrosion of a super-duplex stainless steel (SDSS) with mischmetal addition was investigated in chloride solution by critical pitting temperature (CPT) measurement. The corrosion behavior is strongly dependent on the microstructure, namely the presence of secondary phases, elemental partitioning behavior and volume fractions of ferrite and austenite. Based on CPT results and alloying rules, the optimal annealing temperature is determined as 1070 {sup o}C and a guideline for further development of improved SDSS is formulated.

  10. Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel

    OpenAIRE

    Yanjun Guo; Jincheng Hu; Jin Li; Laizhu Jiang; Tianwei Liu; Yanping Wu

    2014-01-01

    The effect of annealing temperature (1000–1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), energy dispersive X-ray spectroscopy (EDS), uniaxial tensile tests (UTT), and pot...

  11. Identification and analysis of slip systems activated during low-cycle fatigue in a duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    El Bartali, A.; Aubin, V.; Sabatier, L. [Laboratoire de Mecanique de Lille, LML, UMR CNRS 8107, Ecole Centrale de Lille, BP 48, 59651 Villeneuve d' Ascq Cedex (France); Villechaise, P. [Laboratoire de Mecanique et de Physique des Materiaux, LMPM, UMR CNRS 6617, Ecole Nationale Superieure de Mecanique et Aerotechnique, Teleport 2, 1 Avenue C. Ader, BP 40109, 86961 Futuroscope, Chasseneuil Cedex (France); Degallaix-Moreuil, S. [Laboratoire de Mecanique de Lille, LML, UMR CNRS 8107, Ecole Centrale de Lille, BP 48, 59651 Villeneuve d' Ascq Cedex (France)], E-mail: suzanne.degallaix@ec-lille.fr

    2008-12-15

    This paper focuses on the identification of activated slip systems in low-cycle fatigue ({delta}{epsilon}{sub t}/2 = 5 x 10{sup -3}) in a duplex stainless steel. From electron backscattered diffraction measurements and scanning electron microscopy observations, the slip systems and their associated Schmid factor are analyzed in both constitutive phases. In austenitic grains, one or two slip systems are activated with Schmid factors greater than 0.25. While in the ferritic grains, several slip systems are activated, with a variety of Schmid factors.

  12. Identification and analysis of slip systems activated during low-cycle fatigue in a duplex stainless steel

    International Nuclear Information System (INIS)

    This paper focuses on the identification of activated slip systems in low-cycle fatigue (Δεt/2 = 5 x 10-3) in a duplex stainless steel. From electron backscattered diffraction measurements and scanning electron microscopy observations, the slip systems and their associated Schmid factor are analyzed in both constitutive phases. In austenitic grains, one or two slip systems are activated with Schmid factors greater than 0.25. While in the ferritic grains, several slip systems are activated, with a variety of Schmid factors

  13. Electrochemical noise transient analysis for 316 and Duplex 2205 stainless steels in NaCl and FeCl

    International Nuclear Information System (INIS)

    This work shows the results obtained from electrochemical noise measurements for different materials exhibiting pitting corrosion. The transients presented in the potential and current time, correlates with the scanning electron microscopy (SEM) surface analysis. Electrochemical measurements were made at different exposure times to obtain the correlation. The materials used were stainless steel austenitic 316 and duplex 2205, immersed in ferric chloride (FeCl3) and sodium chloride (NaCl) electrolytes. SEM analysis shows that the transients observed in the time series, really correspond to the activity of pit nucleation developed over the surface of the electrodes. (Author) 31 refs.

  14. A study on the effect of corrosion resistance according to the composition variety of C, Cr, N in duplex stainless steel

    International Nuclear Information System (INIS)

    Recently the alloy development of duplex stainless steel has been done. On this study we studied the effect of the corrosion resistance according to the composition variety of C, Cr, N in the alloy elements of duplex stainless steel. Materials which have below 0.1 [mm/year] corrosion rate enable to use for corrosion-resisting materials, generally. On this experiment we inspected the effect of the composition variety of C, Cr, N in duplex stainless steel and the heat treatment, which the condition was the water quenching after the heat treatment for 1 hr. The experiment was done on the basis of the ASTM G48A test, Critical pitting temperature(CPT), and ASTM G-61(Electrochemical tests for cyclic polarization)

  15. Influence of the grain orientation spread on the pitting corrosion resistance of duplex stainless steels using electron backscatter diffraction and critical pitting temperature test at the microscale

    International Nuclear Information System (INIS)

    Highlights: ► Influence of grain orientation spread on the corrosion behavior of duplex stainless steels. ► Metallurgical criterion for pit initiation of duplex stainless steels. ► Crystallographic and electrochemical investigations at the microscale within both phases. - Abstract: The corrosion behavior of UNS S32202 duplex stainless steel was studied by combining electron backscatter diffraction (EBSD) measurements and critical pitting temperature tests at the microscale. The grain orientation spread (GOS) value was determined in grains of both phases from EBSD data. It was shown that austenitic sites containing extremely small ferrite grains having a GOS value greater than 1.3° were precursor sites for pitting in 4 M NaCl. The critical pitting temperature range was 45–90 °C. All the other sites of both phases remained passive up to 100 °C.

  16. Evaluation of intergranular corrosion susceptibility of UNS S31803 duplex stainless steel with an optimized double loop electrochemical potentiokinetic reactivation method

    Energy Technology Data Exchange (ETDEWEB)

    Gong Jia; Jiang, Y.M.; Deng, B.; Xu, J.L. [Department of Materials Science, Fudan University, Shanghai 200433 (China); Hu, J.P. [Chemistry Research Laboratory, University of Oxford, Mansfield Rd, Oxford, OX1 3TA (United Kingdom); Li Jin, E-mail: corrosion@fudan.edu.c [Department of Materials Science, Fudan University, Shanghai 200433 (China)

    2010-07-15

    In this study, an optimized double loop electrochemical potentiokinetic reactivation (DL-EPR) test was applied to evaluate the degree of intergranular corrosion (IGC) susceptibility of duplex stainless steel UNS S31803. The measurement in a solution of 2 M H{sub 2}SO{sub 4} + 1 M HCl at 30 {sup o}C with a scan rate of 1.66 mV s{sup -1}can successfully be used to analyze the interactions between precipitation, chromium depletion, and IGC sensitization of the UNS S31803 steel, which was aged between 30 min and 48 h at 800 {sup o}C. To gain an insight into the phase transition, the specimens were analyzed by scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDX). The results indicated healing due to re-diffusion of Cr and Mo from the {sigma} phase to the {gamma}{sub 2} phase.

  17. Monte Carlo simulation of spinodal decomposition in a ternary alloy within a three-phases field: comparison to phase transformation of ferrite in duplex stainless steels

    Science.gov (United States)

    Emo, Jonathan; Pareige, Cristelle; Saillet, Sébastien; Domain, Christophe; Pareige, Philippe

    2014-06-01

    This work proposes to model phase transformations occurring in duplex stainless steels using atomistic kinetic Monte Carlo in a ternary model alloy. Kinetics are simulated in the three-phase field of a ternary system. Influence of the precipitation of the third phase on the kinetic of spinodal decomposition between the two other phases is studied in order to understand the synergy between spinodal decomposition and G-phase precipitation which exists in duplex stainless steels. Simulation results are compared to experimental data obtained with atom probe tomography.

  18. Some pitfalls in welding of duplex stainless steels Algumas armadilhas na soldagem de aços inoxidáveis duplex

    Directory of Open Access Journals (Sweden)

    Demian J. Kotecki

    2010-12-01

    Full Text Available Duplex stainless steels (DSS, including super duplex stainless steels {SDSS} have proven to be very useful engineering materials, albeit with somewhat different welding requirements than those of the more familiar austenitic stainless steels. Despite a generally good track record in welding of duplex stainless steels, certain pitfalls have been encountered with enough frequency that they deserve review. Inappropriate base metal specification often leads to unsuitable heat affected zone (HAZ properties. Autogenous fusion zones are also of concern. This issue centers around nitrogen limits. The most frequently encountered is applying the UNS S31803 composition for 2205 DSS, instead of the S32205 composition. Inappropriate welding heat input arises most frequently with SDSS. While 0.5 to 1.5 kJ/mm is a normal heat input recommendation for SDSS, either a root pass or many small beads towards the low end of this heat input range tends to result in precipitation and/or secondary austenite formation in weld metal subjected to repeated thermal cycles from multiple weld passes. Inappropriate PWHT occurs when the enhanced nickel filler metals (typically 9% Ni are used. DSS are not normally given PWHT, but extensive forming of heads, for example, or repair welding of castings, may require a postweld anneal. Specifications such as ASTM A790 and A890 call for annealing at 1040ºC minimum, and the fabricator tends to use temperatures close to that minimum. However, the enhanced nickel filler metals require higher temperatures to dissolve sigma phase that forms during heating to the annealing temperature.Aços inoxidáveis duplex (AID, incluindo os aços super duplex, AISD provaram ser materiais de engenharia muito úteis, embora com requerimentos de soldagem em alguma medida diferentes daqueles dos aços inoxidáveis austeníticos mais usuais. Apesar do histórico geralmente bom dos aços inoxidáveis duplex quanto a soldagem, algumas dificuldades têm sido

  19. Gas tungsten arc and laser beam welding processes effects on duplex stainless steel 2205 properties

    International Nuclear Information System (INIS)

    Highlights: ► LBW results in considerable variation in the ferrite–austenite balance of FZ. ► LBW produces smaller FZ size than GTAW. ► The effect of FZ size is more pronounced than that of ferrite–austenite balance. ► Satisfactory mechanical properties were obtained using both GTAW and LBW. ► LBW process has produced welded joint properties comparable to BM. - Abstract: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4 mm thickness was investigated. Autogenous butt welded joints were made using both GTAW and LBW. The GTA welded joint was made using well established welding parameters (i.e., current ampere of 110 A, voltage of 12 V, welding speed of 0.15 m/min and argon shielding rate of 15 l/min). While optimum LBW parameters were used (i.e., welding speed of 0.5 m/min, defocusing distance of 0.0 mm, argon shielding flow rate of 20 l/min and maximum output laser power of 8 kW). The results achieved in this investigation disclose that welding process play an important role in obtaining satisfactory weld properties. In comparison with GTAW, LBW has produced welded joint with a significant decrease in FZ size and acceptable weld profile. The ferrite–austenite balance of both weld metal WM and heat affected zone (HAZ) are influenced by heat input which is a function of welding process. In comparison with LBW, GTAW has resulted in ferrite–austenite balance close to that of base metal BM due to higher heat input in GTAW. However, properties of LB welded joint, particularly corrosion resistance are much better than that of GTA welded joint. The measured corrosion rates for LBW and GTAW joints are 0.05334 mm/year and 0.2456 mm/year, respectively. This is related to the relatively small size of both WM and HAZ produced in the case

  20. Cyclic stress effect on stress corrosion cracking of duplex stainless steel in chloride and caustic solutions

    Science.gov (United States)

    Yang, Di

    Duplex stainless steel (DSS) is a dual-phase material with approximately equal volume amount of austenite and ferrite. It has both great mechanical properties (good ductility and high tensile/fatigue strength) and excellent corrosion resistance due to the mixture of the two phases. Cyclic loadings with high stress level and low frequency are experienced by many structures. However, the existing study on corrosion fatigue (CF) study of various metallic materials has mainly concentrated on relatively high frequency range. No systematic study has been done to understand the ultra-low frequency (˜10-5 Hz) cyclic loading effect on stress corrosion cracking (SCC) of DSSs. In this study, the ultra-low frequency cyclic loading effect on SCC of DSS 2205 was studied in acidified sodium chloride and caustic white liquor (WL) solutions. The research work focused on the environmental effect on SCC of DSS 2205, the cyclic stress effect on strain accumulation behavior of DSS 2205, and the combined environmental and cyclic stress effect on the stress corrosion crack initiation of DSS 2205 in the above environments. Potentiodynamic polarization tests were performed to investigate the electrochemical behavior of DSS 2205 in acidic NaCl solution. Series of slow strain rate tests (SSRTs) at different applied potential values were conducted to reveal the optimum applied potential value for SCC to happen. Room temperature static and cyclic creep tests were performed in air to illustrate the strain accumulation effect of cyclic stresses. Test results showed that cyclic loading could enhance strain accumulation in DSS 2205 compared to static loading. Moreover, the strain accumulation behavior of DSS 2205 was found to be controlled by the two phases of DSS 2205 with different crystal structures. The B.C.C. ferrite phase enhanced strain accumulation due to extensive cross-slips of the dislocations, whereas the F.C.C. austenite phase resisted strain accumulation due to cyclic strain

  1. Gas tungsten arc and laser beam welding processes effects on duplex stainless steel 2205 properties

    Energy Technology Data Exchange (ETDEWEB)

    Mourad, A-H.I., E-mail: ahmourad@uaeu.ac.ae [Mechanical Engineering Department, Faculty of Engineering, United Arab Emirates University, Al-Ain, P.O. Box. 17555 (United Arab Emirates); Khourshid, A.; Sharef, T. [Mechanical Design and Production Department, Faculty of Engineering, Tanta University, Tanta (Egypt)

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer LBW results in considerable variation in the ferrite-austenite balance of FZ. Black-Right-Pointing-Pointer LBW produces smaller FZ size than GTAW. Black-Right-Pointing-Pointer The effect of FZ size is more pronounced than that of ferrite-austenite balance. Black-Right-Pointing-Pointer Satisfactory mechanical properties were obtained using both GTAW and LBW. Black-Right-Pointing-Pointer LBW process has produced welded joint properties comparable to BM. - Abstract: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4 mm thickness was investigated. Autogenous butt welded joints were made using both GTAW and LBW. The GTA welded joint was made using well established welding parameters (i.e., current ampere of 110 A, voltage of 12 V, welding speed of 0.15 m/min and argon shielding rate of 15 l/min). While optimum LBW parameters were used (i.e., welding speed of 0.5 m/min, defocusing distance of 0.0 mm, argon shielding flow rate of 20 l/min and maximum output laser power of 8 kW). The results achieved in this investigation disclose that welding process play an important role in obtaining satisfactory weld properties. In comparison with GTAW, LBW has produced welded joint with a significant decrease in FZ size and acceptable weld profile. The ferrite-austenite balance of both weld metal WM and heat affected zone (HAZ) are influenced by heat input which is a function of welding process. In comparison with LBW, GTAW has resulted in ferrite-austenite balance close to that of base metal BM due to higher heat input in GTAW. However, properties of LB welded joint, particularly corrosion resistance are much better than that of GTA welded joint. The measured corrosion rates for LBW and GTAW joints are 0.05334 mm

  2. Prediction and optimization of friction welding parameters for super duplex stainless steel (UNS S32760) joints

    International Nuclear Information System (INIS)

    Highlights: • Corrosion resistance and impact strength – predicted by response surface methodology. • Burn off length has highest significance on corrosion resistance. • Friction force is a strong determinant in changing impact strength. • Pareto front points generated by genetic algorithm aid to fix input control variable. • Pareto front will be a trade-off between corrosion resistance and impact strength. - Abstract: Friction welding finds widespread industrial use as a mass production process for joining materials. Friction welding process allows welding of several materials that are extremely difficult to fusion weld. Friction welding process parameters play a significant role in making good quality joints. To produce a good quality joint it is important to set up proper welding process parameters. This can be done by employing optimization techniques. This paper presents a multi objective optimization method for optimizing the process parameters during friction welding process. The proposed method combines the response surface methodology (RSM) with an intelligent optimization algorithm, i.e. genetic algorithm (GA). Corrosion resistance and impact strength of friction welded super duplex stainless steel (SDSS) (UNS S32760) joints were investigated considering three process parameters: friction force (F), upset force (U) and burn off length (B). Mathematical models were developed and the responses were adequately predicted. Direct and interaction effects of process parameters on responses were studied by plotting graphs. Burn off length has high significance on corrosion current followed by upset force and friction force. In the case of impact strength, friction force has high significance followed by upset force and burn off length. Multi objective optimization for maximizing the impact strength and minimizing the corrosion current (maximizing corrosion resistance) was carried out using GA with the RSM model. The optimization procedure resulted in

  3. Surface layer investigation of duplex stainless steel S32205 after stress peening utilizing X-ray diffraction

    International Nuclear Information System (INIS)

    Highlights: ► The stress shot peening is superior to the conventional shot peening. ► Residual stresses along the loaded direction are bigger than transverse direction. ► Higher prestress leads to smaller domain size, high density of dislocation. ► Compared to ferrite, austenite has much higher hardness and work hardening. ► Ferrite has higher recover of elastic deformation than austenite after unloading. - Abstract: Residual stresses and micro-hardness of duplex stainless steel S32205 after stress peening are measured and domain sizes and microstrain are calculated. The results show that stress peening can significantly improve the compressive residual stresses and micro-hardness in both austenite and ferrite, and the former is affected by both the prestress and the measurement directions. Microstructure investigation reveals that material deformation is enhanced after stress peening, and smaller domain sizes and higher microstrain are introduced. The compressive residual stress enhancement by stress peening in ferrite is more than that in austenite under the same stress peening, which is due to the more elastic deformation recover in ferrite. Therefore, the difference of residual stresses between ferrite and austenite can be narrowed down by conducting appropriate stress peening. Based on these investigations, it is concluded that stress peening is superior to conventional shot peening treatment to improve the surface properties of duplex stainless steel

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

    Science.gov (United States)

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

    2015-02-01

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

  5. 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.

  6. Microstructure evolution during isothermal annealing of a standard duplex stainless steel type 1.4462

    Energy Technology Data Exchange (ETDEWEB)

    Duprez, L.; Cooman, B.C. de [Ghent Univ. (Belgium). Lab. for Iron and Steelmaking; Akdut, N. [OCAS N.V., Zelzate (Belgium). Research Center of the Sidmar Group

    2000-10-01

    Small alterations in chemical composition, even within the boundaries of the international standards, can drastically alter the formation kinetics of intermetallic phases in a stainless steel. Therefore, by means of isothermal annealing experiments, the time-temperature-precipitation (TTP) diagram was constructed for an industrially cold rolled and annealed standard duplex stainless steel of type 1.4462 (X2CrNiMoN22-5-3), having a distinct composition. Temperature was varied from 600 to 1050 C, with annealing times from 10 to 3.10{sup 5} s Two intermetallic phases were observed with scanning electron microscopy (SEM): {sigma} phase and {chi} phase. {sigma} precipitation occurred in a slightly higher temperature range than {chi} precipitation. In addition, at high temperatures {sigma} was the first phase to appear, while at lower temperatures {chi} was the first. This could be explained by the driving force for transformation, which is larger for {sigma} at high temperatures and larger for {chi} at low temperatures. The microstructural changes during the heat treatment were studied in detail in order to provide a complete overview of all the phenomena that occur during annealing. At temperatures between 750 and 900 C precipitation was fastest and all the {alpha} was replaced by {gamma} and {sigma} after prolonged times. The presence of neighbouring ferrite seems to be a necessary condition for the {chi} phase to be stable. The appearance of large volume fractions of {sigma} above 700 C was accompanied by a strong growth of the austenitic phase resulting in a more isotropic microstructure. Beneath 700 C, the precipitated volume fractions of {sigma} were relatively small and consequently the original banded structure remained clearly visible. At these lower temperatures the mobility of alloying elements is limited and a Widmannstaetten like austenite was observed to grow into the ferrite in a needle-like manner. (orig.) [German] Schon kleine Veraenderungen der

  7. Effect of Microstructure on Mechanical Properties and Corrosion Resistance of 2205 Duplex Stainless Steel

    OpenAIRE

    Łabanowski Jerzy; Świerczyńska Aleksandra; Topolska Santina

    2015-01-01

    This paper presents results of the research on impact of microstructure of austenitic-ferritic steel of duplex type on its mechanical properties and susceptibility to stress corrosion cracking. As showed, improper processing technologies more and more often used in shipbuilding industry for plates and other half-finished products made of duplex steel may cause significant lowering their properties, which frequently makes their replacing necessary. Results of the tests on stress corrosion unde...

  8. The corrosion behaviour of austenitic and duplex stainless steels in artificial body fluids: Korozijsko vedenje avstenitnega in dupleksnega nerjavnega jekla v simuliranih telesnih tekočinah:

    OpenAIRE

    Conradi, Marjetka; Kocijan, Aleksandra

    2010-01-01

    The evolution of the passive film formed on duplex stainless steel 2205 and AISI 316L stainless steel in artificial saliva and a simulated physiological solution was studied using cyclic voltammetry and potentiodynamic measurements. The extent of the passive range slightly decreased with the increasing chloride concentration from artificial saliva to the simulated physiological solution. The formation of pits during the potentiostatic conditions was studied using atomic force microscopy and t...

  9. Final Report, Volume 2, The Development of Qualification Standards for Cast Duplex Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Steven, W.; Lundin, Carl, D.

    2005-09-30

    The scope of testing cast Duplex Stainless Steel (DSS) required testing to several ASTM specifications, while formulating and conducting industry round robin tests to verify and study the reproducibility of the results. ASTM E562 (Standard Test Method for Determining Volume Fraction by Systematic manual Point Count) and ASTM A923 (Standard Test Methods for Detecting Detrimental Intermetallic Phase in Wrought Duplex Austenitic/Ferritic Stainless Steels) were the specifications utilized in conducting this work. An ASTM E562 industry round robin, ASTM A923 applicability study, ASTM A923 industry round robin, and an ASTM A923 study of the effectiveness of existing foundry solution annealing procedures for producing cast DSS without intermetallic phases were implemented. In the ASTM E562 study, 5 samples were extracted from various cast austenitic and DSS in order to have varying amounts of ferrite. Each sample was metallographically prepared by UT and sent to each of 8 participants for volume fraction of ferrite measurements. Volume fraction of ferrite was measured using manual point count per ASTM E562. FN was measured from the Feritescope{reg_sign} and converted to volume fraction of ferrite. Results indicate that ASTM E562 is applicable to DSS and the results have excellent lab-to-lab reproducibility. Also, volume fraction of ferrite conversions from the FN measured by the Feritescope{reg_sign} were similar to volume fraction of ferrite measured per ASTM E562. In the ASTM A923 applicability to cast DSS study, 8 different heat treatments were performed on 3 lots of ASTM A890-4A (CD3MN) castings and 1 lot of 2205 wrought DSS. The heat treatments were selected to produce a wide range of cooling rates and hold times in order to study the suitability of ASTM A923 to the response of varying amounts on intermetallic phases [117]. The test parameters were identical to those used to develop ASTM A923 for wrought DSS. Charpy V-notch impact samples were extracted from the

  10. Final Report, Volume 2, The Development of Qualification Standards for Cast Duplex Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Steven, W.; Lundin, Carl, W.

    2005-09-30

    The scope of testing cast Duplex Stainless Steel (DSS) required testing to several ASTM specifications, while formulating and conducting industry round robin tests to verify and study the reproducibility of the results. ASTM E562 (Standard Test Method for Determining Volume Fraction by Systematic manual Point Count) and ASTM A923 (Standard Test Methods for Detecting Detrimental Intermetallic Phase in Wrought Duplex Austenitic/Ferritic Stainless Steels) were the specifications utilized in conducting this work. An ASTM E562 industry round robin, ASTM A923 applicability study, ASTM A923 industry round robin, and an ASTM A923 study of the effectiveness of existing foundry solution annealing procedures for producing cast DSS without intermetallic phases were implemented. In the ASTM E562 study, 5 samples were extracted from various cast austenitic and DSS in order to have varying amounts of ferrite. Each sample was metallographically prepared by UT and sent to each of 8 participants for volume fraction of ferrite measurements. Volume fraction of ferrite was measured using manual point count per ASTM E562. FN was measured from the Feritescope® and converted to volume fraction of ferrite. Results indicate that ASTM E562 is applicable to DSS and the results have excellent lab-to-lab reproducibility. Also, volume fraction of ferrite conversions from the FN measured by the Feritescope® were similar to volume fraction of ferrite measured per ASTM E562. In the ASTM A923 applicability to cast DSS study, 8 different heat treatments were performed on 3 lots of ASTM A890-4A (CD3MN) castings and 1 lot of 2205 wrought DSS. The heat treatments were selected to produce a wide range of cooling rates and hold times in order to study the suitability of ASTM A923 to the response of varying amounts on intermetallic phases [117]. The test parameters were identical to those used to develop ASTM A923 for wrought DSS. Charpy V-notch impact samples were extracted from the castings and wrought

  11. Characterization by X ray diffraction of deleterious phases precipitated in a super duplex stainless steel; Caracterizacao por difracao de raios X de fases deleterias precipitadas em aco inoxidavel superduplex

    Energy Technology Data Exchange (ETDEWEB)

    Pardal, Juan M.; Tavares, Sergio S. Maior; Fonseca, Maria P. Cindra; Montenegro, Talles Ribeiro, E-mail: juanpardal@vm.uff.b [Universidade Federal Fluminense (PGEMEC/UFF), Niteroi, RJ (Brazil). Programa de Pos-graduacao em Engenharia Mecanica; Dias, Antonio Jose N.; Almeida, Sergio L. de [Instituto Nacional de Tecnologia (INT), Rio de Janeiro, RJ (Brazil). Div. de Materiais Ceramicos e Metalicos. Lab. de Tecnologia de Materiais

    2010-07-01

    In this work the identification and quantification of deleterious phases in two super duplex stainless steels grade UNS S32750, with quite different grain sizes, was performed by X-ray diffraction. The materials were isothermally aged in the 800 . 950 deg C range. Direct comparison method was used to quantify the ferrite phase in each sample. The amount of deleterious phases ({sigma}, {chi} and {gamma}2) formed was calculated by the difference of the amount of ferrite phase measured in each specimen to the amount of ferrite initially measured in the un-aged steel. The results obtained give an useful contribution to the understanding of kinetics of deleterious phases precipitation in super duplex steels. (author)

  12. Lean duplex stainless steels—The role of molybdenum in pitting corrosion of concrete reinforcement studied with industrial and laboratory castings

    International Nuclear Information System (INIS)

    Highlights: ► Mo influence on corrosion of DSS was studied with industrial and laboratory heats. ► Beneficial effect of Mo was associated with ferrite corrosion resistance. ► Mo-species in the alkaline solution did not improve pit resistance. ► Mo role in DSS under alkaline conditions was ascribed to its presence in oxide film. - Abstract: The influence of Mo addition on pitting corrosion resistance of lean duplex stainless steels is not clearly understood in alkaline chloride conditions even if this element is widely recognized to increase corrosion resistance in acidic and neutral environments. This work aims to study the effect of Mo on pitting corrosion of lean duplex stainless steels in synthetic concrete pore solutions simulating degraded concrete. Results are discussed with respect to the influence of Mo on pitting potential for two industrial alloys in chloride rich and carbonated solution simulating concrete pore environments. To establish the real effect of Mo addition on lean duplex corrosion and passivation properties, two specific laboratory lean duplex alloys, for which the only difference is strictly the Mo content, are also studied. Mo presented a strong positive influence on the pitting corrosion resistance of industrial and laboratory lean duplex stainless steels in all studied chloride-rich solutions, but its effect is as less pronounced as the pH increases. In presence of Mo, pitting initiates and propagates preferentially in the austenitic phase at high temperature.

  13. Life evaluation of cast duplex stainless steel elbows in French PWR NPP

    International Nuclear Information System (INIS)

    The principal primary circuit cast elbows of French PWR are in austenitic-ferritic cast stainless steel CF8 - CF8M types. This material is sensitive to thermal aging at PWR operating temperatures. The aging results in a diminishment of tearing resistance characteristics, and with the possible presence of foundry flaws this could lead to a fear of increased break risk. An extensive program on material properties, inspection, tests in laboratory, flaw evaluations, etc, has been covered out in the last 5 years between EDF and FRAMATOME. This paper presents the major tasks performed to justify a good behaviour of these elbows, and they will remain operational at least for the 40-year design lifetime, the consequences at the maintenance level and the utility point of view. CF8 and CF8M are cast materials, that can have casting defects that we generally assume conservatively as a perfect crack for fracture mechanics analysis. The other fact is that materials can be sensitive to thermal aging that were not clearly quantified at the design level by any international code in the 70's. This paper shows EDF's maintenance strategy for those nuclear power plants at present being operated. One important task described in this paper is the material toughness evaluation work proposed to cover all the pipe elbows in 3 loops and 4 loops nuclear power plants. Presently, all the EDF PWR elbows can be used safely for the 40 year design period, some complementary work is in progress to support this conclusion. (author)

  14. Structural stability of super duplex stainless weld metals and its dependence on tungsten and copper

    International Nuclear Information System (INIS)

    Three different superduplex stainless weld metals have been produced using manual metal arc welding under identical welding conditions. The concentration of the alloying elements tungsten and copper corresponded to the concentrations in commercial superduplex stainless steels (SDSS). Aging experiments in the temperature range 700 C to 1,110 C showed that the formation of intermetallic phase was enhanced in tungsten-rich weld metal and also dissolved at higher temperatures compared with tungsten-poor and tungsten-free weld metals. It could be inferred from time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams produced in the present investigation that the critical cooling rate to avoid 1 wt pct of intermetallic phase was 2 times faster for tungsten-rich weld metal. Microanalysis in combination with thermodynamic calculations showed that tungsten was accommodated in χ phase, thereby decreasing the free energy. Experimental evidence supports the view that the formation of intermetallic phase is enhanced in tungsten-rich weld metal, owing to easier nucleation of nonequilibrium χ phase compared with σ phase. The formation of secondary austenite (γ2) during welding was modeled using the thermodynamic computer program Thermo-Calc. Satisfactory agreement between theory and practice was obtained. Thermo-Calc was capable of predicting observed lower concentrations of chromium and nitrogen in γ2 compared with primary austenite. The volume fraction of γ2 was found to be significantly higher in tungsten-rich and tungsten + copper containing weld metal. The results could be explained by a higher driving force for precipitation of γ2 in these

  15. Effect of sigma phase precipitation on the mechanical and wear properties of Z3CN20.09M cast duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.Q.; Han, J.; Wu, H.C. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology, Beijing (China); Yang, B., E-mail: byang@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology, Beijing (China); Wang, X.T. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology, Beijing (China)

    2013-06-15

    Highlights: ► The σ phase in the steel precipitated at a temperature range of 600–900 °C. ► The decomposition of α-ferrite into γ{sub 2} and σ phase in aged specimens is suggested. ► The tensile and yield strengths decreased first and then increased with aging time. ► The impact energy decreased slightly first but then drastically with aging time. ► The hardness and wear rates are not sensitive parameters to aged specimens. -- Abstract: The effect of sigma phase on the mechanical and wear properties of a Z3CN20.09M cast duplex stainless steel (CDSS) used in primary coolant pipe of nuclear power plants has been investigated. The experimental results showed that the sigma phase precipitated from ferrite at a temperature range of 600–900 °C. The tensile and yield strengths of the specimens aged at 700 °C decreased first and then increased with the increase of aging time. With increasing aging time, the impact energy of specimens decreased slightly before 4 h and then dropped drastically when aged a longer time more than 10 h. Fracture surface analysis showed that the hard and brittle sigma phase degraded the toughness of the aged steel. The hardness and wear resistance of the specimens aged for 1–4 h were lower than those of un-aged ones. However, the higher values of hardness and wear resistance were got in the specimens aged more than 10 h.

  16. Effect of sigma phase precipitation on the mechanical and wear properties of Z3CN20.09M cast duplex stainless steel

    International Nuclear Information System (INIS)

    Highlights: ► The σ phase in the steel precipitated at a temperature range of 600–900 °C. ► The decomposition of α-ferrite into γ2 and σ phase in aged specimens is suggested. ► The tensile and yield strengths decreased first and then increased with aging time. ► The impact energy decreased slightly first but then drastically with aging time. ► The hardness and wear rates are not sensitive parameters to aged specimens. -- Abstract: The effect of sigma phase on the mechanical and wear properties of a Z3CN20.09M cast duplex stainless steel (CDSS) used in primary coolant pipe of nuclear power plants has been investigated. The experimental results showed that the sigma phase precipitated from ferrite at a temperature range of 600–900 °C. The tensile and yield strengths of the specimens aged at 700 °C decreased first and then increased with the increase of aging time. With increasing aging time, the impact energy of specimens decreased slightly before 4 h and then dropped drastically when aged a longer time more than 10 h. Fracture surface analysis showed that the hard and brittle sigma phase degraded the toughness of the aged steel. The hardness and wear resistance of the specimens aged for 1–4 h were lower than those of un-aged ones. However, the higher values of hardness and wear resistance were got in the specimens aged more than 10 h

  17. Cyclic plastic response and fatigue life of duplex and superduplex stainless steel

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav

    43 2005, č. 4 (2005), s. 280-289. ISSN 0023-432X R&D Projects: GA ČR(CZ) GA106/02/0584 Institutional research plan: CEZ:AV0Z20410507 Keywords : duplex steel * fatigue life * cyclic plasticity Subject RIV: JG - Metallurgy Impact factor: 0.973, year: 2005

  18. Short crack growth and fatigue life in austenitic-ferritic duplex stainless steel

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Zezulka, Petr

    28 2005, č. 10 (2005), s. 923-935. ISSN 8756-758X R&D Projects: GA ČR(CZ) GA106/01/0376 Institutional research plan: CEZ:AV0Z20410507 Keywords : crack growth * crack initiation * duplex steel Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.673, year: 2004

  19. Effect of kinematic stability of initial orientation on deformation heterogeneity and ductile failure in duplex stainless steel during uniaxial tension

    International Nuclear Information System (INIS)

    The crystal plasticity finite element method (CPFEM) was used to investigate the effect of the kinematic stability of the initial orientations on the deformation heterogeneity and ductile failure of ferrite and austenite phases in duplex stainless steel (DSS) during uniaxial tension. The individual stress–strain relationships of ferrite and austenite phases in DSS were evaluated via in situ neutron diffraction in combination with the CPFEM. A CPFEM based on the volume elements (VEs) of a unit cell of DSS with a regular banded microstructure demonstrated that the kinematic stability of the initial orientations significantly affected the deformation heterogeneity and ductile failure in the constituent phases in VEs during uniaxial tension. The regions susceptible to ductile failure were identified as being in the austenite phase near the phase boundaries of ferrite and austenite

  20. Influence of the mechanical surface treatment on the resistance of localized corrosion in sea water of a duplex stainless steel

    International Nuclear Information System (INIS)

    Author.Localized corrosion in sea water of a duplex stainless sensitized to IGC has been investigated in relation with its mechanical surface finishing. Samples were milled and sandblasted, two mechanical treatments that induced different internal stresses, tensile in the first case and compressive in teh second. In field conditions, sandblasting reduces susceptibility to localized corrosion in sea water even in thermal sensitized conditions. These results have been corroborated by potentiodynamic measurements that show an increase in pitting potential increasing and also in protection potential for the more severe sand blasting condition. Milling has also increased pitting potentials of the sensitized steel but due to temperature elevation during machining that induce dissolution of sigma phase responsible of the localized corrosion of this kind of steel

  1. Investigations on the microstructure and mechanical properties of multi-pass PCGTA welding of super-duplex stainless steel

    Indian Academy of Sciences (India)

    K Devendranath Ramkumar; Debidutta Mishra; G Thiruvengatam; S P Sudharsan; Tadikonda Harsha Mohan; Vimal Saxena; Rachit Pandey; N Arivazhagan

    2015-08-01

    This paper addresses the weldability, microstructure and mechanical properties of the multi-pass welding of super-duplex stainless steel (SDSS). Pulsed current gas tungsten arc welding (PCGTAW) was carried out employing ER2553 and ERNiCrMo-4 fillers. Microstructure examination showed the presence of austenite in different forms at the weld zone of ER2553 whereas multi-directional grain growth was observed for ERNiCrMo-4 welds. Tensile and impact studies corroborated that the weldments employing ER2553 exhibited better results compared with ERNiCrMo-4 weldments. Detailed structure–property relationships of the weldments have been reported in the present study. The results corroborated that the enhanced properties could be achieved with the matching filler wire compared with the over-alloyed filler.

  2. The influence of microstructure on the oxidation of duplex stainless steels in simulated propane combustion products at 1000 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Jepson, M.A.E. [Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)], E-mail: m.jepson@sheffield.ac.uk; Higginson, R.L. [Department of Materials, Loughborough University, Loughborough LE11 3TU (United Kingdom)

    2009-03-15

    A low nickel Type S32101 duplex stainless steel has been oxidised in simulated industrial reheating conditions. The surfaces have been studied using optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Observations show that local breakaway regions (LBRs) form on the austenitic regions whereas thinner oxides are observed on the ferritic regions of the substrate. The reason proposed for these differences is the formation of a continuous oxide layer on the ferrite region and a discontinuous layer on the austenitic region during the early stages of oxidation. The chemical composition of these LBRs have been shown to be oxide islands of iron and manganese and oxide craters of chromium rich oxides. The more protective regions consist of chromium and manganese rich oxides. A silica layer formed below the oxide which may be attributable to a slight enrichment of silicon in the ferritic regions or due to faster rates of diffusion in ferrite.

  3. Effect of annealing temperature on the pitting corrosion resistance of super duplex stainless steel UNS S32750

    Energy Technology Data Exchange (ETDEWEB)

    Tan Hua; Jiang Yiming; Deng Bo; Sun Tao; Xu Juliang [Department of Material Science, Fudan University, Shanghai 200433 (China); Li Jin, E-mail: jinli@fudan.edu.cn [Department of Material Science, Fudan University, Shanghai 200433 (China)

    2009-09-15

    The pitting corrosion resistance of commercial super duplex stainless steels SAF2507 (UNS S32750) annealed at seven different temperatures ranging from 1030 deg. C to 1200 deg. C for 2 h has been investigated by means of potentiostatic critical pitting temperature. The microstructural evolution and pit morphologies of the specimens were studied through optical/scanning electron microscope. Increasing annealing temperature from 1030 deg. C to 1080 deg. C elevates the critical pitting temperature, whereas continuing to increase the annealing temperature to 1200 deg. C decreases the critical pitting temperature. The specimens annealed at 1080 deg. C for 2 h exhibit the best pitting corrosion resistance with the highest critical pitting temperature. The pit morphologies show that the pit initiation sites transfer from austenite phase to ferrite phase as the annealing temperature increases. The aforementioned results can be explained by the variation of pitting resistance equivalent number of ferrite and austenite phase as the annealing temperature changes.

  4. Residual Stress Relaxation of Shot-Peened Deformation Surface Layer on Duplex Stainless Steel Under Applied Loading

    Science.gov (United States)

    Feng, Qiang; Jiang, Chuanhai; Xu, Zhou

    2013-10-01

    The relaxation of residual stress in shot-peened surface layer of duplex stainless steel S32205 under static and cyclic loading was investigated. The results reveal that the compressive residual stress is relaxed under applied tensile stress. The relaxation of residual stress in longitudinal direction is more obvious than that in transverse direction in both austenite and ferrite. When the applied stress is beyond the yield strength of the materials, the relaxation of the residual stress becomes drastic. Under cyclic loading, the residual stress relaxation occurs fast in the first few cycles, it then becomes stable gradually. A model was used to quantitatively calculate the residual stress under cyclic loading with different applied tensile stresses. The relaxation behavior is determined by the applied loading, the number of cycles, dislocation density, and the residual stress gradient. The relaxation behavior difference under cyclic loading between ferrite and austenite is discussed.

  5. 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

  6. Tensile-property characterization of thermally aged cast stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Michaud, W.F.; Toben, P.T.; Soppet, W.K.; Chopra, O.K. [Argonne National Lab., IL (United States)

    1994-02-01

    The effect of thermal aging on tensile properties of cast stainless steels during service in light water reactors has been evaluated. Tensile data for several experimental and commercial heats of cast stainless steels are presented. Thermal aging increases the tensile strength of these steels. The high-C Mo-bearing CF-8M steels are more susceptible to thermal aging than the Mo-free CF-3 or CF-8 steels. A procedure and correlations are presented for predicting the change in tensile flow and yield stresses and engineering stress-vs.-strain curve of cast stainless steel as a function of time and temperature of service. The tensile properties of aged cast stainless steel are estimated from known material information, i.e., chemical composition and the initial tensile strength of the steel. The correlations described in this report may be used for assessing thermal embrittlement of cast stainless steel components.

  7. Tensile-property characterization of thermally aged cast stainless steels

    International Nuclear Information System (INIS)

    The effect of thermal aging on tensile properties of cast stainless steels during service in light water reactors has been evaluated. Tensile data for several experimental and commercial heats of cast stainless steels are presented. Thermal aging increases the tensile strength of these steels. The high-C Mo-bearing CF-8M steels are more susceptible to thermal aging than the Mo-free CF-3 or CF-8 steels. A procedure and correlations are presented for predicting the change in tensile flow and yield stresses and engineering stress-vs.-strain curve of cast stainless steel as a function of time and temperature of service. The tensile properties of aged cast stainless steel are estimated from known material information, i.e., chemical composition and the initial tensile strength of the steel. The correlations described in this report may be used for assessing thermal embrittlement of cast stainless steel components

  8. Thermally Sprayed Aluminum (TSA) Coatings for Extended Design Life of 22%Cr Duplex Stainless Steel in Marine Environments

    Science.gov (United States)

    Paul, S.; Shrestha, S.; Lee, C. M.; Harvey, M. D. F.

    2013-03-01

    In this article, evaluation of sealed and unsealed thermally sprayed aluminum (TSA) for the protection of 22%Cr duplex stainless steel (DSS) from corrosion in aerated, elevated temperature synthetic seawater is presented. The assessments involved general and pitting corrosion tests, external chloride stress corrosion cracking (SCC), and hydrogen-induced stress cracking (HISC). These tests indicated that DSS samples, which would otherwise fail on their own in a few days, did not show pitting or fail under chloride SCC and HISC conditions when coated with TSA (with or without a sealant). TSA-coated specimens failed only at very high stresses (>120% proof stress). In general, TSA offered protection to the underlying or exposed steel by cathodically polarizing it and forming a calcareous deposit in synthetic seawater. The morphology of the calcareous deposit was found to be temperature dependent and in general was of duplex nature. The free corrosion rate of TSA in synthetic seawater was measured to be ~5-8 μm/year at ~18 °C and ~6-7 μm/year at 80 °C.

  9. Numerical simulation of a Charpy test and correlation of fracture toughness with fracture energy. Vessel steel and duplex stainless steel of the primary loop

    International Nuclear Information System (INIS)

    The analysis methods used to evaluate the harmlessness of defects in the components of the primary coolant circuit of pressurized water reactor are based on the knowledge of the failure properties of concerned materials. The toughness is used to be measured through tests performed on normalized samples. But in some cases, especially for the vessel steel submitted to irradiation effects or for cast components in duplex stainless steel sensitive to thermal ageing, these measurements are not available on the material aged in operation. Therefore, fracture resistance has been evaluated through Charpy tests. Toughness is thus obtained on the basis of an empirical correlation. To improve these predictions, a modeling of the Charpy test in the framework of the local approach to fracture has been performed, for both materials. For the vessel steel, a complete evaluation of toughness has been achieved on the basis of a bidimensional viscoplastic modeling under large strain assumptions and a post-treatment with a Weibull model (cleavage fracture). The main hypothesis (partition between plain stress and plain strain areas in the bidimensional modeling) was corrected after a three dimensional calculations with the finite element program Code-Aster. The fracture analysis put into evidence that damage considerations like cavity nucleation and growth have to be introduced in the model in order to improve the description of physical phenomena. Two ways of progress have been suggested and are in course of being investigated, one in the framework of local approach to failure, the other with the help of micro-macro relationship. With regard to the duplex steel, the description of a Charpy (U) test allowed to clearly discriminate between crack initiation and propagation phases. A modeling through an equivalent homogenous material with a damage law based on a modified Gurson potential enables to describe quantitatively both phases of fracture. It clearly appears that a reliable

  10. Pitting and Crevice Corrosion of Super Duplex Stainless Steels in Seawater - Effect of Tungsten

    OpenAIRE

    Bjørge Haugan, Eirik

    2015-01-01

    The need for low cost and lighter materials with higher mechanical and chemical properties has lead to more frequently usage of SDSS because of their increased mechanical and superior corrosion properties compared to other stainless steels. SDSS is also relatively less expensive compared to austenitic stainless steels (ASS) due to lower nickel content. This has lead to an increased hunger for knowledge about every aspect of different alloy elements effect on different parameters for the best ...

  11. Corrosion behaviour of single (Ti) and duplex (Ti-TiO2) coating on 304L stainless steel in nitric acid medium

    International Nuclear Information System (INIS)

    Highlights: → Ti coated 304L SS showed moderate to marginal corrosion resistance in 1 M and 8 M HNO3. → Duplex Ti-TiO2 coated 304L SS showed minimization of structural heterogeneities. → Passive film property improves by minimizing structural heterogeneities. → Protection efficiency for 304L SS increases with duplex Ti-TiO2 coating in HNO3. - Abstract: Sputter deposited single titanium (Ti) layer, and duplex Ti-TiO2 coating on austenitic type 304L stainless steel (SS) was prepared, and the corrosion performance was evaluated in nitric acid medium using surface morphological and electrochemical techniques. Morphological analysis using atomic force microscope of the duplex Ti-TiO2 coated surface showed minimization of structural heterogeneities as compared to single Ti layer coating. The electrochemical corrosion results revealed that, titanium coated 304L SS showed moderate to marginal improvement in corrosion resistance in 1 M, and 8 M nitric acid, respectively. Duplex Ti-TiO2 coated 304L SS specimens showed improved corrosion resistance as compared to Ti coating from dilute (1 M) to concentrated medium (8 M). The percentage of protection efficiency for base material increases significantly for duplex Ti-TiO2 coating as compared to single Ti layer coating. The oxidizing ability of nitric acid on both the coatings as well as factors responsible for improvement in protection efficiency are discussed and highlighted in this paper.

  12. The corrosion behaviour of austenitic and duplex stainless steels in artificial saliva with the addition of fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Kocijan, Aleksandra, E-mail: Aleksandra.Kocijan@imt.s [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Merl, Darja Kek [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Jenko, Monika [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia)

    2011-02-15

    Research highlights: The corrosion behaviour of AISI 316L and 2205 DSS in orthodontics. The increased passive range for DSS 2205 compared to AISI 316L in artificial saliva. Higher R{sub p} values of DSS compared to AISI 316L in artificial saliva. The main constituent of the passive layers on DSS at the OCP in saliva was Cr-oxide. DSS 2205 is suitable for orthodontic applications in artificial saliva. - Abstract: The evolution of the passive films on 2205 duplex stainless steel (2205 DSS) and AISI 316L stainless steel in artificial saliva, and with the addition of fluoride, was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements. The extent of the passive range increased for the 2205 DSS compared to the AISI 316L in both solutions. The formation of the passive film was studied by EIS at the open-circuit potential (OCP). The passive layers were studied at the OCP by X-ray photoelectron spectroscopy (XPS). The passive films on both materials predominantly contained Cr-oxides, whereas the Fe species were markedly depleted.

  13. Effect of post treatments on the corrosion resistance of plasma sprayed duplex stainless steel coating in salt water

    International Nuclear Information System (INIS)

    The uniform composition of a thermally sprayed duplex stainless steel coating is essential to ensure its good corrosion resistance in salt water. Stainless steel coatings made by atmospheric plasma spraying (APS) always contain pores and oxides accompanied with chromium-depleted zones which destroy the corrosion resistance of such coatings. To reduce porosity and oxidation of the coatings, several post treatments for the coatings sprayed by APS and by APS with gas shielding around the plasma jet (APS/S) were studied including resin impregnation, hot isostatic pressing (HIP), shot peening and vacuum annealing. Electrochemical corrosion tests revealed that the corrosion resistance of the APS coatings could not be improved by any post treatments because oxidation during spraying caused chromium-depleted zones in the coating. The best corrosion resistance was obtained by using the shielding gas shroud with APS. Such coatings had a very low oxide content and primarily ferritic structure. The corrosion resistance of these APS/S coatings can be further improved by shot peening to densify the coating or by post annealing, which balances the austenite/ferrite ratio of the coating as well as reduce porosity

  14. The corrosion behaviour of austenitic and duplex stainless steels in artificial saliva with the addition of fluoride

    International Nuclear Information System (INIS)

    Research highlights: → The corrosion behaviour of AISI 316L and 2205 DSS in orthodontics. → The increased passive range for DSS 2205 compared to AISI 316L in artificial saliva. → Higher Rp values of DSS compared to AISI 316L in artificial saliva. → The main constituent of the passive layers on DSS at the OCP in saliva was Cr-oxide. → DSS 2205 is suitable for orthodontic applications in artificial saliva. - Abstract: The evolution of the passive films on 2205 duplex stainless steel (2205 DSS) and AISI 316L stainless steel in artificial saliva, and with the addition of fluoride, was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements. The extent of the passive range increased for the 2205 DSS compared to the AISI 316L in both solutions. The formation of the passive film was studied by EIS at the open-circuit potential (OCP). The passive layers were studied at the OCP by X-ray photoelectron spectroscopy (XPS). The passive films on both materials predominantly contained Cr-oxides, whereas the Fe species were markedly depleted.

  15. Evaluation of structural behaviour and corrosion resistant of austenitic AISI 304 and duplex AISI 2304 stainless steel reinforcements embedded in ordinary Portland cement mortars

    International Nuclear Information System (INIS)

    The mechanical and structural behaviour of two stainless steels reinforcements, with grades austenitic EN 1.4301 (AISI 304) and duplex EN 1.4362 (AISI 2304) have been studied, and compared with the conventional carbon steel B500SD rebar. The study was conducted at three levels: at rebar level, at section level and at structural element level. The different mechanical properties of stainless steel directly influence the behaviour at section level and structural element level. The study of the corrosion behaviour of the two stainless steels has been performed by electrochemical measurements, monitoring the corrosion potential and the lineal polarization resistance (LPR), of reinforcements embedded in ordinary Portland cement (OPC) mortar specimens contaminated with different amount of chloride over one year time exposure. Both stainless steels specimens embedded in OPC mortar remain in the passive state for all the chloride concentration range studied after one year exposure. (Author) 26 refs.

  16. Influence of the shielding gas composition on the passive film and erosion corrosion of tube-to-tube sheet welds of hyper duplex stainless steel

    International Nuclear Information System (INIS)

    Highlights: • Addition of nitrogen gas in shielding gas facilitated reformation of austenite phase. • Addition of nitrogen gas improved the erosion corrosion resistance in the weld metal. • Heat affected zones are susceptible to erosion corrosion damage. • Increase of chemical species related to nitrogen improved stability of passive film. - Abstract: Resistance to erosion corrosion was determined by degree of repair of passive film under flowing conditions combined corrosive solution. To examine effects of nitrogen addition to argon shielding gas on erosion corrosion of hyper duplex stainless steel welds, stability of oxide film passivity of hyper duplex stainless steel welds was measured through electrochemical tests and X-ray photoelectron spectroscopy analyses. The results indicated the resistance to erosion corrosion was improved due to the increase of austenite phase and the stability of the passive film resulting in change of chemical species as supplemented with the nitrogen gas in the argon shielding gas

  17. Corrosion Resistance and Mechanical Properties of TIG and A-TIG Welded Joints of Lean Duplex Stainless Steel S82441 / 1.4662

    Directory of Open Access Journals (Sweden)

    Brytan Z.

    2016-06-01

    Full Text Available This paper presents results of pitting corrosion resistance of TIG (autogenous and with filler metal and A-TIG welded lean duplex stainless steel S82441/1.4662 evaluated according to ASTM G48 method, where autogenous TIG welding process was applied using different amounts of heat input and shielding gases like pure Ar and Ar+N2 and Ar+He mixtures. The results of pitting corrosion resistance of the welded joints of lean duplex stainless steel S82441 were studied in as weld conditions and after different mechanical surface finish treatments. The results of the critical pitting temperature (CPT determined according to ASTM G48 at temperatures of 15, 25 and 35°C were presented. Three different surface treatment after welding were applied: etching, milling, brushing + etching. The influence of post weld surface treatment was studied in respect to the pitting corrosion resistance, basing on CPT temperature.

  18. Influence of pH on the electrochemical behaviour of a duplex stainless steel in highly concentrated LiBr solutions

    OpenAIRE

    Guiñon Pina, Virginia; Igual Muñoz, Anna Neus; García Antón, José

    2011-01-01

    The objective is to study the influence of pH on the corrosion and passive behaviour of duplex stainless steels (DSS) using potentiodynamic measurements, potentiostatic tests and electrochemical impedance spectroscopy (EIS). DSS are spontaneously passive in heavy brine LiBr solutions. Under potentiostatic conditions at applied anodic potentials within the passive domain an equivalent circuit with two time constants is the most suitable model to describe the corrosion mechanism in the interfac...

  19. Effects of hydrogen assisted stress corrosion on damage tolerance of a high-strength duplex stainless steel wire for prestressing concrete

    OpenAIRE

    Abreu Rodrigues, Maricely de; Iordachescu, Mihaela; Valiente Cancho, Andrés

    2014-01-01

    The study brings new insights on the hydrogen assisted stress corrosion on damage tolerance of a high-strength duplex stainless steel wire which concerns its potential use as active reinforcement for concrete prestressing. The adopted procedure was to experimentally state the effect of hydrogen on the damage tolerance of cylindrical smooth and precracked wire specimens exposed to stress corrosion cracking using the aggressive medium of the standard test developed by FIP (International Prestre...

  20. SKPFM measured Volta potential correlated with strain localisation in microstructure to understand corrosion susceptibility of cold-rolled grade 2205 duplex stainless steel

    OpenAIRE

    Cem Örnek, Dirk L. Engelberg

    2015-01-01

    Scanning Kelvin probe force microscopy (SKPFM) of annealed and cold-rolled grade 2205 duplex stainless steel has been correlated with microstructure analysis using electron back-scattered diffraction (EBSD). In annealed microstructure Volta potential differences indicated micro-galvanic coupling between ferrite and austenite reasoning selective dissolution of ferrite. The introduction of cold work reduced the difference between both phases, but the development of local extremes in Volta poten...