Plasma nitriding in industry—problems, new solutions and limits

Abstract

Plasma nitriding as a diffusion process is the oldest plasma-assisted process for the surface treatment of metals. Although the use of this process in industry is already well developed and established there are still several scientific questions in the basic understanding of the process and consequently some problems and limits concerning its upscaling for industrial use. Therefore it is necessary to get reproducible results for different geometries of workpieces and for different workload sizes. Correlations between different plasma and treatment parameters, especially in big plants, have to be considered. To understand the process handling using some simple but impressive models the difficulties of treating single parts or mixed workloads are explained. For profitable applications of plasma nitriding plants, some guidelines for the use and selection of a suitable process and a device are given. By the use of a pulsed d.c. power supply for plasma generation most of the industrial problems of the past can be solved. Some industrial experiences of the use of the plasma nitriding process are presented. The better knowledge about the plasma and some of the solutions for plasma nitriding could be transferred to other plasma-assisted processes such as plasma vapour deposition and plasma-assisted chemical vapour deposition.