低温盐浴渗氮对420马氏体不锈钢性能的影响

Effect of salt bath nitriding process at low temperature on properties of 420 martensitic stainless steel

对420马氏体不锈钢进行低温（400-490℃）盐浴渗氮。通过X射线衍射仪、光学显微镜、扫描电镜、显微硬度仪、电化学方法等，研究了温度对不锈钢渗氮层的显微结构、厚度、耐蚀性以及显微硬度的影响。结果表明，渗氮层主要由铁氮化物和αN组成；经低温盐浴渗氮后，不锈钢的显微硬度明显提高，在腐蚀性介质中其表面能生成有效钝化膜，耐蚀性和耐冲刷腐蚀能力提高；长时间高温渗氮会使不锈钢出现贫铬现象，导致显微硬度和耐蚀性降低。

420 martensitic stainless steel was nitrided in salt bath at low temperature （400-490℃）. The effect of temperature on the microstructure, thickness, corrosion resistance, and microhardness of nitriding layer was studied by X-ray diffractometer, optical microscope, scanning electron microscope, microhardness tester, and electrochemical method. The results showed that the nitriding layer is mainly composed of iron nitrides and αN. The microhardness of stainless steel is increased after salt bath nitriding at low temperature. The corrosion and erosion-corrosion resistance of stainless steel are improved as a result of the formation of effective passive film on its surface in corrosive media. Poor chromium phenomenon appears to stainless steel after nitriding at high temperature for long time, resulting in the decrease of microhardness and corrosion resistance.