Low temperature plasma diffusion treatment of stainless steels for improved wear resistance

The use of a thermionically enhanced low pressure plasma process to provide nitriding and carburizing treatments on a precipitation hardening martensitic stainless steel (AISI 17/4PH) at low temperature (420°C or less) is reported. The resulting diffusion layers are analysed by glow discharge optical spectroscopy and X-ray diffraction depth profiling to provide information on the changes in diffused-species concentration and metallurgical structure with treatment depth. It is shown that there exists the possibility to synthesize a variety of layered structures under different plasma conditions using the low pressure enhanced plasma process—with particular emphasis on the production of hard, yet “precipitate-free” surface layers based on an expanded austenite lattice. These types of layered diffusion treatments may provide considerable improvements in the wear resistance of stainless steels without significantly compromising their desirable corrosion-resistant properties.