Friction and wear mechanisms in boundary lubricated oxy-nitrided treated samples

Oxy-nitriding has been found to be an effective surface treatment technique, used widely in industrial applications due to its ability to prolong the performance lifetime of components. However there has been little work focussing on the potential synergistic effects on tribological behaviour between the treated layers after oxy-nitriding and anti-wear lubricant additives to optimise performance. The friction and wear behaviour of oxy-nitrided (QPQ), MoS2 coated and plain steel samples were analysed. Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy were employed to identify the morphologies and chemical compositions of the treated surfaces before and after testing. QPQ samples exhibited a lower friction coefficient and volume loss. The main mechanisms of these effects were attributed to the mechanical properties of the compound layer formed after the QPQ process and the possible influence of the greater concentration of FeS2 within the tribofilm.