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利用低温离子渗碳技术,在不同温度下对AISI 316L奥氏体不锈钢进行渗碳处理。利用光学显微镜、显微硬度计、XRD以及电化学测试技术研究了渗碳温度对不锈钢表面显微组织和性能的影响。结果表明,渗碳温度显著影响AISI 316L奥氏体不锈钢渗碳层的组织结构与性能。渗碳温度在400~550℃之间时,可以获得无碳化物析出的、具有单一γc相结构的渗碳层;渗碳温度在550℃时,渗碳层为γc相+Cr23C6+Cr7C3+Fe3C+Fe2C的混合组织。渗碳层的厚度与硬度均随渗碳温度的升高而增加。550℃是AISI 316L奥氏体不锈钢中铬的碳化物析出的临界温度。为了避免铬的碳化物析出而降低不锈钢的耐蚀性能,奥氏体不锈钢渗碳必须在低于550℃的渗碳温度下进行。
AISI 316L austenitic stainless steels were carburized at different temperatures using low temperature ion carburization. The effects of carburizing temperature on the microstructure and properties of stainless steel were investigated by optical microscope, microhardness tester, XRD and electrochemical testing. The results show that the carburizing temperature significantly affects the microstructure and properties of carburized AISI 316L austenitic stainless steel. When carburizing temperature is between 400 ℃ and 550 ℃, carburized layer with single γc phase structure without carbides can be obtained. When carburizing temperature is 550 ℃, the carburized layer is γc phase + Cr23C6 + Cr7C3 + Fe3C + Fe2C mixed tissue. The thickness and hardness of carburized layer increase with the increase of carburizing temperature. 550 ° C is the critical temperature for precipitation of chromium from AISI 316L austenitic stainless steels. In order to avoid chromium carbide precipitation and reduce the corrosion resistance of stainless steel, austenitic stainless steel carburization must be carried out below the carburizing temperature of 550 ℃.