Friction energy map for sliding wear of Al₂O₃-TiO₂ and Cr₂O₃-TiO₂ coatings

Abstract

The present study deals with the development of friction energy map for plasma sprayed Al2O3-TiO2 and Cr2O3-TiO2 coatings. Al2O3-TiO2 and Cr2O3-TiO2 coatings were deposited by atmospheric plasma spray technique. The structural and mechanical properties of coatings were studied using Scanning Electron Microscopy (SEM), x-ray Diffraction (XRD) and Vickers macro and micro hardness test. Sliding wear tests were performed on coated specimens over a range of sliding speed and load using pin on disc test apparatus. The analysis of worn surface and wear debris was carried by SEM, XRD and Raman Spectroscopy. Cr2O3-TiO2 coating showed higher hardness and elastic modulus and relatively lower fracture toughness than Al2O3-TiO2 coating. Al2O3-TiO2 coatings exhibited 1.8 times better wear resistance and 11%–30% lower friction coefficient, as compared to Cr2O3-TiO2 coating, depending upon the wear test conditions. The reduction in friction coefficient and wear rate at higher sliding speed was due to the formation of tribofilms on worn surface. A good correlation was observed between friction energy and contact severity; which incorporates mechanical properties of coatings. Friction energy map was used to rationalize wear rates of Al2O3-TiO2 and Cr2O3-TiO2 coatings, for the identification of various wear regimes and failure modes of the coating.