The effect of vanadium content and temperature on stick–slip phenomena under friction of CrV(x)N coatings

The aim of this work is to investigate the stick–slip phenomenon under friction of CrV(x)N (x=0%, 12%, 27%, and 35%) coatings at room and high temperatures. The effects of vanadium (V) content and the temperature on the friction and stick–slip parameters for the contact pair: coating-ceramic ball were analyzed. The amplitude – a difference between the maximal and minimal values of the friction force, the static force (at the beginning of friction) and the kinetic friction force (average value in the steady state) were chosen for the description of the stick–slip phenomenon. The surface morphology, the structure and the mechanical properties of coatings were analyzed by SEM, AFM and XRD techniques. The hardness and roughness parameters before and after friction were measured. It was shown that the addition of V up to 27–35% in CrV(x)N coatings increased the hardness and toughness and decreased the grain size. These parameters are responsible for the improved tribological properties of coatings with high a content of V. Friction of the CrV(0)N coating rubbed at room temperature is accompanied by strong sticking. High values of the stick–slip parameters are explained by mechanical “catching” and adhesion on the contact spots due to high roughness and transfer of Si films on the surface of the coating. Low values of the stick–slip parameters under friction of CrV(35)N at high temperature (T=500 °C) are due to the formation of lubricious V2O5 oxide layer providing easy shearing of tribofilms in the interface of rubbed surfaces.