Improvement of hot-working processes with PVD coatings and duplex treatment

Abstract

Optimisation of manufacturing processes in mechanical engineering which involve working temperatures higher than 600°C and high surface loads, e.g. pressure die-casting, hot extrusion and hot forging, is today under intensive investigation worldwide. Traditional production procedures and the enormous quantities of products in these industries are serious limitations to the introduction of any kind of improvement to moulds, tools and dies with PVD coatings and duplex treatment. Thus, the simulation of selected tribo-systems is practically impossible and any performance testing of new technologies must therefore be carried out in real industrial manufacturing. In this paper we discuss the properties of surface improvements relevant to these topics. These comprise PVD CrN, TiAlN and FUTURA TiN/TiAlN multilayer coatings, and duplex treatments, including plasma nitriding (PN) and all three PVD coatings. We studied the applications of CrN, PN+CrN and PN+TiAlN in aluminium pressure die-casting, CrN in hot extrusion of Al and FUTURA and PN+FUTURA coating in hot forging of steel parts. Performance tests were carried out in various industrial plants in Slovenia. The results show that an improvement in tool or die life (cost saving) of up to several 100% is not the decisive factor. More important for these traditional industries are better reproducibility of the surface quality of the products, an increase in the manufacturing reliability in heavy machining, a decrease in manufacturing interruption (down-time) and finally, the protection of the environment.