Low pressure r.f. nitriding of austenitic stainless steel in an industrial-style heat-treatment furnace

The nitriding efficiency of a low pressure r.f. plasma is investigated in a n industrial style hot-wall furnace in which the component is heated by the rmal radiation from the walls of the vacuum chamber. The role of degassed i mpurities is also addressed. Samples of AISI 316 stainless steel were treat ed at a relatively low temperature of 400 degrees C to avoid loss of corros ion resistance. The results are compared with treatments under similar cond itions of plasma (sample bias, gas pressure, process temperature and treatm ent time), in cold wall experimental reactors, including a fully UHV compat ible apparatus. Process conditions can be found for which the hot-wall furn ace gives the best results, despite a high rate of impurity evolution. The apparently higher activity of the low pressure r.f. plasma in this environm ent can be exploited for low temperature plasma assisted nitriding. (C) 199 9 Elsevier Science S.A. All nights reserved.