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为避免传统直流离子渗氮存在的表面打弧和边缘效应等弊端,采用活性屏阳极渗氮法对AISI 304奥氏体不锈钢进行表面处理。将样品放置于阳极电位,在440~520℃范围内,渗氮处理8 h。分析了渗氮层的微观组织结构与形貌,并考察了渗氮前后的摩擦磨损性能。结果表明:在低温440℃下,在表面制备了高硬度的S相强化层。XRD与TEM表明S相为面心立方结构,且无Cr N相析出。高温520℃渗氮表面硬度值(1100 HV0.1)是基体的5倍,但Cr N相明显析出。在干摩擦条件下,渗氮处理后的摩擦系数在0.8左右,相对渗氮前降低约0.2,特别是磨损率只有渗氮前的十分之一量级。磨损机制从原始基体的严重粘着转变为轻微的氧化和磨粒磨损。
In order to avoid the disadvantages of surface arc and edge effect of conventional DC plasma nitriding, AISI 304 austenitic stainless steel was surface-treated with anodic active nitriding method. The sample was placed in the anode potential in the range of 440 ~ 520 ℃, nitriding 8 h. The microstructure and morphology of nitrided layer were analyzed, and the tribological properties before and after nitriding were investigated. The results show that the S phase reinforced layer with high hardness is prepared on the surface at a low temperature of 440 ℃. X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that S phase is a face-centered cubic structure with no precipitation of Cr N phase. High temperature 520 ℃ nitriding surface hardness (1100 HV0.1) is 5 times the matrix, but the Cr N phase was precipitated. Under the condition of dry friction, the coefficient of friction after nitriding treatment is about 0.8, which is reduced by about 0.2 before nitriding. In particular, the wear rate is only one tenth of that before nitriding. The wear mechanism has shifted from severe adhesion of the original substrate to slight oxidation and abrasive wear.