Formulation and testing of optimised coating properties with regard to tribological performance in cold forging and fine blanking applications

Within the scope of a more environmentally friendly production, there is a trend to reduce the amount of additives in lubricants for fine blanking, as well as to abolish the workpiece pretreatment in cold forging applications. The tribological functions of the additives or the workpiece pretreatment are intended to be taken over by hard ceramic CVD or PVD coatings, applied to the surface of the tool elements. Many applications of hard ceramic coatings on tools for metal forming applications are known. However, every successful case appears to be based on a trial-and-error way of development. Therefore, this paper will present results in the characterisation of tribological conditions in cold forging and fine blanking processes. The tribological conditions are calculated using an approach on four different scales. Having analysed the tribological conditions that coatings are subjected to in the cold forging and fine blanking processes, models for the description of frictional and wear processes are presented. This leads to the formulation of optimised and desirable properties of coatings on tool elements. After formulation of the coating properties, the measurement of these properties will be discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.