固溶渗氮温度对16Cr25N不锈钢组织性能的影响

Effect of solution nitriding temperature on microstructure and properties of 16Cr25N stainless steel

采用高温固溶渗氮工艺在自主设计研制的高温高真空渗氮炉中对16Cr25N铁素体不锈钢进行渗氮处理,通过X射线衍射仪、扫描电镜、能谱仪、金相显微镜、显微硬度计和氧氮分析仪分析了渗氮层的组织和性能。结果表明,在铁素体不锈钢表面形成了1 mm以上厚度的奥氏体渗氮层,单边渗氮层最大厚度超过2 mm,渗氮层氮含量最大达到1.502%,原始材料的铁素体组织已转变为奥氏体组织,相当于得到了高氮无镍不锈钢。相比于原始样品,渗氮处理后样品硬度大幅提升,达到320 HV0.5。通过渗层深度计算了16Cr25N不锈钢固溶渗氮时氮的扩散激活能,在氮气压力0.3 MPa、保温时间24 h、渗氮温度1200℃下,扩散激活能为176 kJ/mol。利用渗层硬度和扩散理论建立了16Cr25N铁素体不锈钢高温固溶渗氮层的氮含量模型,具有一定的指导作用。

16Cr25N ferritic stainless steel was nitrided by a high-temperature solution nitriding process in a self-designed high-temperature and high vacuum nitriding furnace, and then the microstructure and properties of the nitrided layer were analyzed by means of X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, metallographic microscopy, microhardness tester, and oxygen nitrogen analyzer. The results show that an austenitic nitrided layer with a thickness of more than 1 mm is formed on the surface of the tested steel, with the maximum single-side thickness of the nitrided layer being more than 2 mm and the maximum nitrogen content reaching 1.502%, and the original ferrite microstructure transforms into austenite, which is equivalent to obtaining a high-nitrogen and nickel-free stainless steel. and its hardness after the nitriding treatment is greatly increased to 320 HV0.5. The activation energy of nitrogen diffusion during solid solution nitriding of the 16Cr25N stainless steel is calculated by the depth of the infiltration layer, which is 176 kJ/mol under the condition of nitrogen pressure of 0.3 MPa, insulation time of 24 h, and nitriding temperature of 1200 ℃. The nitrogen content model for high temperature solution nitrided layer of the 16Cr25N ferrite stainless steel is established by using the infiltration layer hardness and diffusion theory, which has certain guiding impact.