M50NiL steel was plasma nitrocarburized at 480 °C with and without rare earth （RE） addition. The microstructures of the surface layer were characterized by optical microscopy, X-ray diffraction and scanning ele...M50NiL steel was plasma nitrocarburized at 480 °C with and without rare earth （RE） addition. The microstructures of the surface layer were characterized by optical microscopy, X-ray diffraction and scanning electron microscopy. The mechanical proper-ties and corrosion resistances of the surface layer were studied by Vickers microhardness measurements and polarization tests in 3.5% NaCl solution. The results showed that RE atoms could diffuse into the surface layer of the steel and inhabit the formation ofε-Fe2–3（N,C） phase. As compared to the treatment without RE addition, RE addition further increased the surface hardness by 143 HV0.1, and further increased the thickness of the nitrocarburized layer by 39μm. Compared with the quenched bearing steel, the cor-rosion resistance of the samples nitrocarburized with and without RE addition could be significantly improved. Especially, the sample plasma nitrocarburized with RE addition exhibited the highest corrosion resistance.展开更多
The dissolution and precipitation behaviors of the carbides in carburized M50NiL steel were derived from different solution and tempering treatments.Totally four kinds of carbides of (V,Cr)-rich MC,(Mo,Fe)-rich M2C,Fe...The dissolution and precipitation behaviors of the carbides in carburized M50NiL steel were derived from different solution and tempering treatments.Totally four kinds of carbides of (V,Cr)-rich MC,(Mo,Fe)-rich M2C,Fe-rich M3C and (Fe,Cr)-rich M7C3 were obtained from the carburized M50NiL steel after different heat treatments.The key carbides of carbufized M50NiL steel were proved to be tough V-rich MC and Cr-rich M7C3.The highest hardness (634 HV)and the optimal surface structure with 1.0% volume fraction of uniformly distributed MC carbides were obtained after the carbufized M50NiL steel was solution-treated at 1150 ℃ and tempered at 500 ℃.The quantitative statistics show that 63%of the MC carbides were less than 200 nm under that heat treatment.The variety of carbides changed with solution and tempering conditions.When the solution temperature increased from 1050 to 1150 ℃,the undissolved carbides were proved to be Fe-rich M7C3,Mo-fich MC and (Mo,Fe)-fich M2C.Besides,the equivalent content of V-rich MC was found increased when the tempering temperature changed from 500 to 550 ℃.The combination of high-temperature solution and low-temperature tempering is recommendable heat treatment for the high hardness as well as the tiny and uniformly distributed carbides.展开更多
基金supported by the National Natural Science Foundation of China(51371070,51401062)
文摘M50NiL steel was plasma nitrocarburized at 480 °C with and without rare earth （RE） addition. The microstructures of the surface layer were characterized by optical microscopy, X-ray diffraction and scanning electron microscopy. The mechanical proper-ties and corrosion resistances of the surface layer were studied by Vickers microhardness measurements and polarization tests in 3.5% NaCl solution. The results showed that RE atoms could diffuse into the surface layer of the steel and inhabit the formation ofε-Fe2–3（N,C） phase. As compared to the treatment without RE addition, RE addition further increased the surface hardness by 143 HV0.1, and further increased the thickness of the nitrocarburized layer by 39μm. Compared with the quenched bearing steel, the cor-rosion resistance of the samples nitrocarburized with and without RE addition could be significantly improved. Especially, the sample plasma nitrocarburized with RE addition exhibited the highest corrosion resistance.
基金National Natural Science Foundation of China under Grant NSFC 51471012.
文摘The dissolution and precipitation behaviors of the carbides in carburized M50NiL steel were derived from different solution and tempering treatments.Totally four kinds of carbides of (V,Cr)-rich MC,(Mo,Fe)-rich M2C,Fe-rich M3C and (Fe,Cr)-rich M7C3 were obtained from the carburized M50NiL steel after different heat treatments.The key carbides of carbufized M50NiL steel were proved to be tough V-rich MC and Cr-rich M7C3.The highest hardness (634 HV)and the optimal surface structure with 1.0% volume fraction of uniformly distributed MC carbides were obtained after the carbufized M50NiL steel was solution-treated at 1150 ℃ and tempered at 500 ℃.The quantitative statistics show that 63%of the MC carbides were less than 200 nm under that heat treatment.The variety of carbides changed with solution and tempering conditions.When the solution temperature increased from 1050 to 1150 ℃,the undissolved carbides were proved to be Fe-rich M7C3,Mo-fich MC and (Mo,Fe)-fich M2C.Besides,the equivalent content of V-rich MC was found increased when the tempering temperature changed from 500 to 550 ℃.The combination of high-temperature solution and low-temperature tempering is recommendable heat treatment for the high hardness as well as the tiny and uniformly distributed carbides.
