Effect of rf Plasma Carbonitriding on Physical Properties of 304 Stainless Steel and 1050 Aluminium

Abstract

In recent years there has been growing interest in using low• pressure glow discharge for promoting chemical or physical reactions that are otherwise difficult or indeed impossible to achieve by conventional methods. This has resulted in the development of novel processes and materials. The nonequilibrium nature of the plasma (high electron temperature and low gas temperature) leads to dissociation of a gas and deposition of a film at much lower temperatures than are possible with pyrolytic chemical vapor deposition (CVD). Plasma processing utilizes an ionized gas to change the surface or sometimes, the bulk • structure of materials. The surface hardening of materials by nitriding has become important commercial process. Through nitriding, very hard surface layers obtained without substantial modification of the bulk material properties. There are many techniques of nitriding materials such as traditional nitriding by gases containing ammonia, ion nitriding, ion implantation and rf plasma discharges.

Frequently components like gears and axles need to be tough and ductile but, at the same time, have a hard and wear- resistance surface. Ductile materials, are usually soft whilst hard materials are generally brittle, so the most effective way to achieve this difficult combination of properties is to use steel I stainless steel which has a surface of different composition from that of the core; as is contrived by nitriding. The principal reasons for nitriding could be used to achieve high surface hardness, high wear resistance, long fatigue life, high corrosion resistance (except for some. kinds of stainless steels) and to obtain a surface that is resistant to the softening effect of heat at temperatures up to the nitriding temperature.