离子渗氮温度对Fe-C-Cr-Ni-Mn-V沉淀硬化型奥氏体不锈钢渗层组织和性能的影响

Effect of plasma nitriding temperature on microstructure and properties of nitrided layer on Fe-C-Cr-Ni-Mn-V precipitation-hardened austenitic stainless steel

采用离子渗氮工艺对一种Fe-C-Cr-Ni-Mn-V沉淀硬化型奥氏体不锈钢进行表面改性处理。利用光学显微镜(OM)、X射线衍射(XRD)、电子探针显微分析仪(EPMA)和维氏硬度计对不同离子渗氮温度下渗层的组织和性能进行了研究。结果表明,Fe-C-Cr-Ni-Mn-V沉淀硬化型奥氏体不锈钢经430~520℃离子渗氮处理10 h后,试样表面均形成一层厚度均匀的渗氮层,表面硬度显著增大。随着离子渗氮温度的升高,渗层厚度增大,520℃渗氮时渗层厚度达到78μm。当渗氮温度为430℃时,渗层表面主要由γN+CrN+γ′-Fe_(4)N相组成;当渗氮温度升高至520℃时,渗层表面主要由γ′-Fe_(4)N+CrN+ε-Fe_(2-3)N相组成。在3种渗氮温度下,渗层中均有CrN析出,导致渗层耐蚀性低于基体组织。

The surface of a Fe-C-Cr-Ni-Mn-V precipitation-hardened austenitic stainless steel was modified by plasma nitriding.Microstructure and properties of the nitrided layer at different nitriding temperatures were investigated by means of optical microscope(OM),X-ray diffraction(XRD),electron probe microanalysis(EPMA)and Vickers hardness tester.The results show that nitrided layer with uniform thickness on the specimen surface is formed by plasma nitriding at temperatures ranging from 430℃ to 520℃ for 10 h,and the surface hardness is significantly improved.The thickness of the nitrided layer increases with the increase of nitriding temperature and reaches 78μm at 520℃.The infiltration layer is composed of γ_(N),CrN and γ′-Fe_(4)N phases after nitriding at 430℃,and composed of γ′-Fe_(4)N,CrN and ε-Fe_(2-3)N phases when the nitriding temperature increases to 520℃.Precipitation of CrN is found in the infiltration layer at all the three nitriding temperatures,resulting in the poor corrosion resistance compared with that of the substrate.