Microstructure-property relationships in Cr(C)N coatings

Abstract

In this study, the effect of carbon on microstructure, mechanical properties, tribological properties and the deformation and fracture behavior in CrN and CrCN coatings with various graphite target currents in the deposition process were investigated. The elemental composition of Cr(C)N was characterized by X-ray photoelectron spectroscopy (XPS). With the increase in graphite target current, the carbon content in the Cr(C)N increased. The microstructure of Cr(C)N was investigate using atomic force microscopy (AFM), focused ion beam (FIB) microscopy, x-ray diffraction (XRD) and transmission electron microscopy (TEM). AFM and cross-sectional FIB images and TEM images show the grain size was decreasing with carbon content. XRD and the selected area electron diffraction patterns (SAED) of TEM show the phase was changing from Cr2N-dominante to CrN-dominate with increasing carbon content in the Cr(C)N coatings. Energy dispersive spectroscopy (EDS) of TEM analyzes the distribution of elements across the sample cross-section. Hardness and Young s modulus were obtained using a Hysitron Triboindenter. The coefficient of friction was obtained using pin-on-disk tribometer. Deformation and fracture behaviour of the Cr(C)N coatings was determined using UMIS nanoindentation and pin-on-disk tribometer, followed by cross-sectional FIB and TEM analysis. Crack can only be observed in the Cr(C)N coatings with low carbon content even at a load of 500mN for UMIS nanoindentation and a load of 5N for pin-on-disk tribometer. Generally, hardness, modulus and coefficient of friction are generally decreased with carbon content. However, some results show a slightly difference which might attribute to various factors such as bonding types, phases and grain size etc.