A nitriding technique for improving die life

Abstract

The absence of proper understanding and facilities for heat treatment, specifically surface treatment techniques has retarded the development of tooi and die industry in Sri Lanka. Thus there has been a growing interest among the local tool manufacturers and users for new heat treatment techniques. It has been shown that the surface properties for Dies and Moulds can be enhanced by nitriding and this technique was first used in early 1920’s. Since then much development has taken place and now the technique can be applied to a greater variety' of steels than it was originally thought possible. However nitriding is still in its infancy as far as the local industry is concerned. Nitriding is basically the introduction of atomic nitrogen from a surrounding medium into the surface of steel by diffusion. In contrast to most heat treatment procedures nitriding changes both the chemical composition and the structure of the layer thereby enabling the properties to vary in a wider range. Extreme hardness, retention of hardness at elevated temperatures, improved fatigue strength and corrosion resistance are some of the properties imparted by nitriding. This paper describes the work carried out towards developing a suitable nitriding technique adaptable by the local medium and small scale industries with due regards to economy and safety aspects. It is expected to carry out industrial trials to assess the efficiency of the proposed setup.