Influence of process parameters in pulse plasma nitriding of plain carbon steel

Abstract

Glow discharge nitriding is widely used to improve the mechanical characteristics of steel components. This treatment produces a modified surface layer, consisting of an outer compound zone and an inner diffusion zone. The compound zone (white layer) is the first zone and therefore, is the contact surface layer. It is of particular interest for establishing the exploitation features of engineering components exposed to the wear and corrosion. It is important to analyse the mechanical and tribological features of this layer. With the aim of optimising the nitriding process and gaining an insight for further research, experimental studies of the pulsed plasma nitriding of plain carbon steel grade DIN C45 (AISI C1043) were carried out, using a pulsed direct current glow discharge. The influence of gas composition, temperature, treatment time, duty cycle and frequency on compound layer thickness and microhardness has been investigated. Five experiments were performed. In each experiment, one of the process parameters was varied while the others were kept constant. The characteristics of the nitride surface layers were studied by optical metallography, Vickers microhardness measurement as well as specially modified Calo test method. The results obtained could be useful in optimising of the nitriding process and computer process control.