Low temperature hardening treatment of austenitic stainless steel

Austenitic stainless steel has excellent corrosion resistance and is widely used in chemical machinery, pharmaceutical machinery and food machinery. However, due to the low hardness and poor wear resistance of austenitic stainless steel, some mechanical parts that need wear resistance are made of austenitic stainless steel, and the surface properties are difficult to meet the requirements of use, which greatly reduces the service life of these mechanical parts. . People have been seeking how to improve the surface wear resistance without reducing the corrosion resistance of austenitic stainless steel. Among them, the austenitic stainless steel ion heat treatment process and equipment is simple, and it is a promising new technology for surface hardening of austenitic stainless steel.

The surface of austenitic stainless steel can be hardened by ion heat treatment at low temperature (nitriding <450 °C, carburizing <550 °C) to form a supersaturated solid solution of nitrogen or carbon on the surface, and no chromium The nitride or carbide precipitates, and the structure having such a characteristic is called the S phase. The surface hardness of the hardened austenitic stainless steel is as high as 900 HV or more, and its corrosion resistance is even better than that of the prior austenitic stainless steel.

The key to surface hardening of austenitic stainless steel is how to control the temperature of the workpiece being processed. If the temperature is low, the permeation rate is slow, even nitrogen or carbon atoms will not penetrate into the matrix; if the treatment temperature is high, the infiltrated nitrogen or carbon will form chromium nitride or carbide, which will reduce the concentration of free chromium on the stainless steel surface. The corrosion resistance of stainless steel is degraded. Therefore, the temperature of the surface hardening treatment of the austenitic stainless steel must be strictly controlled within the range of ±5 ° C, which is difficult to achieve in a general ion heat treatment apparatus.

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