Kinetics of low temperature plasma carburizing of austenitic stainless steels

A low temperature plasma carburizing technique has recently been developed to engineer the surfaces of austenitic stainless steels for combined improvement in wear and corrosion resistance. The resultant carburized layer is characterized by the supersaturation of carbon in austenite lattices, the much-increased hardness and wear resistance, and most importantly its superior corrosion resistance. This paper presents recent experimental results on the kinetics of this novel process, in terms of the growth of the precipitation-free layer and its variation with processing temperature, time and substrate material. This work demonstrates that the low temperature carburizing process is a diffusion-controlled process, and only when the processing temperature is sufficiently low can a precipitation-free layer be produced. In addition, the chemical compositions of the substrate material also affect the formation and kinetics of the precipitation-free layer. By proper process control and material selection, a high-quality carburized layer 10-50 μm thick can be produced at temperatures between 400 and 500 °C for wear protection in highly corrosive environments.