Paper VII (v) Chemical and Microstructural Aspects of Debris Formation in Mild Sliding Wear

Abstract

Wear tests were performed on TiC hardcoating in air, at room temperature in pin-on-disk testers. Wear scars and surface films were analyzed by scanning Auger microscopy (SAM), secondary electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) equipped with energy dispersive X-ray analysis (EDX). Composition of the debris and the debris/rider interface were studied by SAM and SEM and the phases and morphology of the debris by TEM. SAM of transfer films showed titanium oxide, not TiC transferred from TiC to steel and sapphire riders. Comparison between analyses of transfer layers and remaining coatings suggested that shear took place at the oxide/carbide interface. TEM diffraction patterns indicated that the debris stripped from steel riders contained binary and/or ternary oxide compounds Fe2O 3 and/or FeTiO 3 and that the ones stripped from sapphire balls were pure TiO 2 . These phases were accounted for by equilibrium ternary and quaternary phases diagrams which were calculated from thermochemical data. This thermochemical model is used to discuss the friction and wear results obtained for other treatments: MoS2, TiN and Ti and Ti+C implantation and to explain the various phases found in the debris particles. Chemical and mechanical differences achieved when sliders are changed from steel to sapphire will be emphasized. Relations between friction, chemistry and morphology of debris particles will be discussed.