Industrial applications of PACVD hard coatings

Abstract

Transition metal nitride based hard coatings are widely applied in metal cutting, however, there are still drawbacks in metal forming processes limiting their implementation. The aim of this study is thus to discuss deposition processes suitable for coating of the often large and three-dimensional molds and dies used in metal forming. Furthermore, results obtained using different hard coatings in industrial applications for several case studies like aluminum pressure die-casting, plastics injection molding and sheet metal forming are presented and discussed. For best coating performance, a careful optimization of both substrate pre-treatment and coating deposition is necessary. The plasma-assisted chemical vapor deposition (PACVD) technique shows advantages for these applications because of the high flexibility in pre-treatment using chemical etching and plasma-nitriding, because of its ability to coat large complexly shaped tools and because of the possibility of deposition of low-chlorine containing low-friction coatings. Typical factors for the increase in lifetime in aluminum pressure die-casting are between 2 and 4, in plastics injection molding more than 10 and in deep drawing of 13 with respect to uncoated tools.