Development of Hard PVD Coating Systems for Machining Austenitic Stainless Steels

Abstract

Application of hard coatings was found to be a promising method in response to industry’s growing demand for improved productivity and avoiding high temperature in cutting zone. Cutting speed as a one of the major factors of productivity, significantly increase the heat generation and temperature in cutting zone. Therefore, using protective coatings with higher thermal stability is required to maintain the productivity at high level. This research investigated the effect of Al concentration in Ti1-xAlxN lattice with various x amount during high-speed machining of austenitic stainless steels. The results showed that higher up to a certain point, thermal stability, mechanical properties, machining performance of the coating improved. Above this point, a drop in properties was observed associated with a change in crystal structure. further development in coating properties was obtained by incorporating Ta into TiAlN coating. As a results, a significant improvement in mechanical properties, 25% prolonged tool life at higher cutting speed (650 m/min), better thermal stability and excellent oxidation resistance was obtained. Out of different coating architecture, the results showed that monolayer TiAlTaN coating showed best properties.