Effect of Cu Content on the Structure, and Performance of Substoichiometric Cr-N Coatings

Cu-Cr-N coatings with Cu contents between 3 and 65 at.%, Cu/Cr ratios in the 0.04-4.5 range and 21-27 at.% N, synthesized by twin electron-beam Physical Vapor Deposition at 450 °C, were investigated and compared against substoichiometric Cr-N reference samples. The main objective of this study is to study the influence of Cu on the structure, and the subsequent effects on the mechanical properties, room (22 °C) and high temperature (500 and 840 °C) tribological performance of Cu-Cr-N coatings. Using X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and scanning electron microscopy, in combination with nanoindentation mechanical property measurements and laboratory-controlled ball-on-disc sliding experiments, it is shown that Cu-Cr-N coatings with low Cu content (3 at.%) possess sufficient wear resistance for high-temperature demanding tribological applications. The lubricious effect of oxide formation at high temperatures is also evaluated.