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采用离子轰击去除不锈钢表面的钝化膜,并活化试样的表面,然后再进行低温气体渗碳处理。经过反复几次循环处理后,实现AISI 316L奥氏体不锈钢表面低温硬化处理。利用显微硬度计测试表面硬度、硬度梯度;用光学显微镜观察硬化层横截面的显微组织。结果表明,在渗碳温度为440~590℃内,硬化层的表面硬度及厚度与渗碳温度和循环处理周期成正比。温度在440~510℃内,硬化层增厚相对比较缓慢;当渗碳温度超过510℃后,硬化层的厚度增速加快。在440~530℃之间,硬化层表面硬度基本保持不变,在530℃之后,硬化层的表面硬度继续增加。在3~7个循环处理周期内,硬化层厚度增长速度较快,在第7个循环处理周期后,硬化层厚度增长速度变慢。不降低耐蚀性能的奥氏体不锈钢低温渗碳硬化处理的临界温度为530℃。
The passive film on the surface of stainless steel is removed by ion bombardment and the surface of the sample is activated, and then the low-temperature carburizing is performed. After repeated cycles, AISI 316L austenitic stainless steel was hardened at low temperature. The surface hardness and hardness gradient were measured with a microhardness tester. The microstructure of the cross section of the hardened layer was observed with an optical microscope. The results show that the surface hardness and thickness of the hardened layer are proportional to the carburizing temperature and cycle time at the carburizing temperature of 440-590 ℃. When the temperature is in the range of 440-510 ℃, the thickening of the hardened layer is relatively slow. When the carburizing temperature exceeds 510 ℃, the thickness of hardened layer increases rapidly. Between 440 and 530 ℃, the surface hardness of the hardened layer remained almost unchanged, and the surface hardness of the hardened layer continued to increase after 530 ℃. During 3 to 7 cycles, the thickness of the hardened layer increased rapidly. After the 7th cycle, the thickness of the hardened layer increased slowly. The critical temperature of austenitic stainless steels for low temperature carburization without lowering the corrosion resistance is 530 ° C.