INFLUENCE OF ABRASIVE WEAR MODES ON THE COEFFICIENT OF FRICTION OF THIN FILMS
The purpose of this work is to study the influence of abrasive wear modes on the coefficient of friction (μ) of thin films. Initially, free rotative-ball micro-abrasive wear testing equipment was designed and constructed to measure the coefficient of friction on the tribological system “thin film – abrasive slurry – test sphere”. Experiments were conducted with thin films of TiN, CrN, TiAlN, ZrN, TiZrN, TiN/TiAlN, TiN/TiAlN (multi-layer), TiHfC and TiHfCN using a ball of AISI 52100 steel and abrasive slurries prepared with black silicon carbide (SiC) particles and glycerine. The aim of this design was to produce “grooving abrasion” and “rolling abrasion” on the surface of thin films. The normal force (N) and the tangential force (T) were monitored throughout the tests, and the coefficient of friction was calculated as μ = T/N. Aside from the thin film type, e.g., for all thin films studied, the results that have been obtained in this work show that the abrasive slurry concentration affected the abrasive wear modes (“grooving abrasion” or “rolling abrasion”) and, consequently, the magnitude of the coefficient of friction: i) a low abrasive slurry concentration was related with grooving abrasion and a relatively high coefficient of friction; ii) a high abrasive slurry concentration was related with rolling abrasion and a relatively low coefficient of friction.
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