Nanoindentation study of PVD WC/C coatings supported by cross-sectional electron microscopy observations

Coatings consisting of multilayer tungsten carbide, carbon (WC/C) were depo sited by physical vapour deposition (PVD) onto, steel substrates. The goal of this investigation was to probe the outcome of coatings dissimilarities as well as the substrates employed on the mechanical properties of the syst em by nonoindentation techniques. The coatings investigated are mainly comp osed of a chromium columnar interlayer to improve the adhesion to the subst rate, an inter-multilayer of WC and carbon, and an interlaminar amorphous W C/C multilayer structure. The mechanical properties were assessed by nanoin dentation techniques. The hysteresis loops were analysed and discussed in t erms of the method developed by Oliver and Pharr. Moreover, a new technique for cross-sectional transmission electron microscopy of the nanoindentatio ns has been developed. anti the information obtained was correlated with th e load-displacement data from a nanoindentation cycle to clarify the extent of any delamination fracture. (C) 2001 IoM Communications Ltd.