The mechanical and corrosive properties of 00Cr13Ni4Mo （S13 -4N） were tested and compared with those of 00Cr13Ni6Mo （S13 -6）. The effects of nitrogen on the properties of the steels were analyzed. The results of t...The mechanical and corrosive properties of 00Cr13Ni4Mo （S13 -4N） were tested and compared with those of 00Cr13Ni6Mo （S13 -6）. The effects of nitrogen on the properties of the steels were analyzed. The results of the tensile and corrosion tests show the strength,the ductility,and the pitting corrosion resistance of S13 -4N are higher, lower and poorer than those of S13 -6 respectively, when tempered at a temperature below 550 ℃and vice versa when the tempering temperature is higher than 550℃. The results of the X-ray diffraction （XRD） and the electron backscattered diffraction （EBSD） analyses reveal that inversed austenite appears at 550℃ and the amount of it peaks at 600 ℃ with the best ductility. And the total amount of the inversed austenite in S13 -6 is more than that in S13 -4N in different forms. Nitrogen performs better in terms of stabilizing inversed austenite while nickel is more favorable for forming inversed austenite, the amount and stability of which affect the ductility remarkably. The reason for the embrittlement of S13 -4N at 450℃ can be the result of carbide and nitride precipitating at grain boundaries.展开更多
The microstructures and mechanical properties of Cr13 super martensitic stainless steel after different heat treatments were studied. The results show that the structures of the steel after quenching are of lath marte...The microstructures and mechanical properties of Cr13 super martensitic stainless steel after different heat treatments were studied. The results show that the structures of the steel after quenching are of lath martensite mixed with a small amount of retained austenite. With the raising quenching temperature, the original austenite grain size increases and the lath martensite gradually becomes thicker. The structures of the tempered steel are mixtures of tempered martensite and reversed austenite dispersed in the martensite matrix. The amount of reversed austenite is from 7.54% to 22. 49%. After different heat treatments, the tensile strength, the elongation and the HRC hardness of the steel are in the range of 813 1 070 MPa, 10.1%--21.2% and 21.33--32.37, respectively. The steel displays the best comprehensive mechanical properties after the sample is quenched at 1 050 ℃ followed by tempering at 650 ℃.展开更多
The effect of different heat treatments on the reversed austenite in Cr15 super martensitic stainless steel was investigated. The experimental results indicate that the microstructure of the steel is composed of tempe...The effect of different heat treatments on the reversed austenite in Cr15 super martensitic stainless steel was investigated. The experimental results indicate that the microstructure of the steel is composed of tempered martensite and diffused reversed austenite after quenching at 1 050 ℃ and tempering from 550 to 750 ℃. The volume fraction and size of reversed austenite increase with increasing tempering temperature and both of them reach the maximum value at 700 ℃. The volume fraction and size of reversed austenite decrease when the temperature is above 700 ℃. The transmission electron microscope （TEM） results indicate that the orientation relationship between tempered martensite and reversed austenite belongs to Kurdjmov-Sach （K-S） relationship.展开更多
In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary elec...In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary electron microscope(ASPEX PSEM detector),scanning electron microscope(SEM),transmission electron microscope(TEM),scanning Kelvin probe force microscope(SKP),potentiodynamic and potentiostatic polarizations were employed.The results obtained indicate that BASE steel contains Al_(2)O_(3)/Mn S,Al_(2)O_(3) and Mn S inclusions,while REM steels contain(La,Ce,Cr,Fe)-O and(La,Ce,Cr,Fe)-O-S inclusions.Compared with BASE steel,REM steel is more susceptible to induce the metastable pitting nucleation and repassivation,whereas it restrains the transition from metastable pitting to stable pitting.Adding 0.021%rare earth element to BASE steel can reduce the number and area of inclusions,while that of 0.058%can increase the number and enlarged the size of inclusions,which is also the reason that pitting corrosion resistance of 58 REM steel is slightly lower than that of 21 REM steel.In the process of pitting corrosion induced by Al_(2)O_(3)/Mn S inclusions,Mn S is preferentially anodic dissolved,and also the matrix contacted with Al_(2)O_(3) is subsequently anodic dissolved.For REM steels,anodic dissolution preferentially occurs at the boundary between inclusions and matrix,while(La,Ce,Cr,Fe)-O inclusions chemically dissolve in local acidic environment or are separated from steel matrix.The chemically dissolved substance(La^(3+) and Ce^(3+))of(La,Ce,Cr,Fe)-O inclusions are concentrated in pitting pits,which inhibits its continuous growth.展开更多
To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by ...To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by scanning electron microscopy,X-ray diffraction and electron backscattered diffraction,and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution.It was found that grains and the martensitic matrix were refined by TCHT through the cyclic quenching transformation and austenite recrystallization,which was conducive to more nucleation quantity of reversed austenite during tempering.Two-sphericalcap nucleation model was used to explain the effect of refined grains of TCHT on the nucleation of reversed austenite.Grain refinement by TCHT improved the brittle fracture stress to reduce the ductile-brittle transition temperature and thus improved the cryogenic impact toughness of 13-4MSS.Reversed austenite distributed at the martensitic lath boundary enhances the crack arrest performance and increases the britle fracture stress.It is concluded that reasonable TCHT plus tempering process significantly improves the strength-toughness of 13-4MSS,reflecting the comprehensive effect of grain refinement and reversed austenite.展开更多
文摘The mechanical and corrosive properties of 00Cr13Ni4Mo （S13 -4N） were tested and compared with those of 00Cr13Ni6Mo （S13 -6）. The effects of nitrogen on the properties of the steels were analyzed. The results of the tensile and corrosion tests show the strength,the ductility,and the pitting corrosion resistance of S13 -4N are higher, lower and poorer than those of S13 -6 respectively, when tempered at a temperature below 550 ℃and vice versa when the tempering temperature is higher than 550℃. The results of the X-ray diffraction （XRD） and the electron backscattered diffraction （EBSD） analyses reveal that inversed austenite appears at 550℃ and the amount of it peaks at 600 ℃ with the best ductility. And the total amount of the inversed austenite in S13 -6 is more than that in S13 -4N in different forms. Nitrogen performs better in terms of stabilizing inversed austenite while nickel is more favorable for forming inversed austenite, the amount and stability of which affect the ductility remarkably. The reason for the embrittlement of S13 -4N at 450℃ can be the result of carbide and nitride precipitating at grain boundaries.
文摘The microstructures and mechanical properties of Cr13 super martensitic stainless steel after different heat treatments were studied. The results show that the structures of the steel after quenching are of lath martensite mixed with a small amount of retained austenite. With the raising quenching temperature, the original austenite grain size increases and the lath martensite gradually becomes thicker. The structures of the tempered steel are mixtures of tempered martensite and reversed austenite dispersed in the martensite matrix. The amount of reversed austenite is from 7.54% to 22. 49%. After different heat treatments, the tensile strength, the elongation and the HRC hardness of the steel are in the range of 813 1 070 MPa, 10.1%--21.2% and 21.33--32.37, respectively. The steel displays the best comprehensive mechanical properties after the sample is quenched at 1 050 ℃ followed by tempering at 650 ℃.
文摘The effect of different heat treatments on the reversed austenite in Cr15 super martensitic stainless steel was investigated. The experimental results indicate that the microstructure of the steel is composed of tempered martensite and diffused reversed austenite after quenching at 1 050 ℃ and tempering from 550 to 750 ℃. The volume fraction and size of reversed austenite increase with increasing tempering temperature and both of them reach the maximum value at 700 ℃. The volume fraction and size of reversed austenite decrease when the temperature is above 700 ℃. The transmission electron microscope （TEM） results indicate that the orientation relationship between tempered martensite and reversed austenite belongs to Kurdjmov-Sach （K-S） relationship.
基金supported by the National Natural Science Foundation of China(No.51801219)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193)+1 种基金the Scientific Research Project of China Three Gorges Corporation(No.JD-YJ-05006)the National Key Research and Development Program of China(No.2017YFB0702302)。
文摘In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary electron microscope(ASPEX PSEM detector),scanning electron microscope(SEM),transmission electron microscope(TEM),scanning Kelvin probe force microscope(SKP),potentiodynamic and potentiostatic polarizations were employed.The results obtained indicate that BASE steel contains Al_(2)O_(3)/Mn S,Al_(2)O_(3) and Mn S inclusions,while REM steels contain(La,Ce,Cr,Fe)-O and(La,Ce,Cr,Fe)-O-S inclusions.Compared with BASE steel,REM steel is more susceptible to induce the metastable pitting nucleation and repassivation,whereas it restrains the transition from metastable pitting to stable pitting.Adding 0.021%rare earth element to BASE steel can reduce the number and area of inclusions,while that of 0.058%can increase the number and enlarged the size of inclusions,which is also the reason that pitting corrosion resistance of 58 REM steel is slightly lower than that of 21 REM steel.In the process of pitting corrosion induced by Al_(2)O_(3)/Mn S inclusions,Mn S is preferentially anodic dissolved,and also the matrix contacted with Al_(2)O_(3) is subsequently anodic dissolved.For REM steels,anodic dissolution preferentially occurs at the boundary between inclusions and matrix,while(La,Ce,Cr,Fe)-O inclusions chemically dissolve in local acidic environment or are separated from steel matrix.The chemically dissolved substance(La^(3+) and Ce^(3+))of(La,Ce,Cr,Fe)-O inclusions are concentrated in pitting pits,which inhibits its continuous growth.
基金supported by Specific Research Project of Guangxi for Research Bases and Talents(Grant No.GuiKe AD19245145)Natural Science Foundation of Guangxi Province(Grant No.2018GXNSFBA281106).
文摘To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by scanning electron microscopy,X-ray diffraction and electron backscattered diffraction,and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution.It was found that grains and the martensitic matrix were refined by TCHT through the cyclic quenching transformation and austenite recrystallization,which was conducive to more nucleation quantity of reversed austenite during tempering.Two-sphericalcap nucleation model was used to explain the effect of refined grains of TCHT on the nucleation of reversed austenite.Grain refinement by TCHT improved the brittle fracture stress to reduce the ductile-brittle transition temperature and thus improved the cryogenic impact toughness of 13-4MSS.Reversed austenite distributed at the martensitic lath boundary enhances the crack arrest performance and increases the britle fracture stress.It is concluded that reasonable TCHT plus tempering process significantly improves the strength-toughness of 13-4MSS,reflecting the comprehensive effect of grain refinement and reversed austenite.
