A Study of Active Screen Plasma Nitriding

Abstract

Active screen plasma nitriding (ASPN) is an emerging surface engineering technology that offers many advantages over the conventional dc plasma nitriding (DCPN). In this work, samples of a low alloy steel 722M 24 were AS plasma nitrided with various gas compositions and using different active screen setups. Normal dc plasma nitriding was also performed under similar conditions for comparison. The nitrided samples were characterised with a variety of analytical techniques, including optical microscopy and SEM for morphological and structural examination, XRD for phase identification, and microhardness testing for surface hardness and hardness profile measurements. It has been shown that ASPN can achieve a similar nitriding effect as the normal DCPN but without the common problems associated with dc nitriding such as the arcing surface damage, the edging effect, and the hollow cathode effect. The mechanism of nitrogen mass transfer in AS plasma nitriding has been investigated, and a modified sputtering deposition model has been used to explain the AS plasma nitriding experimental results.