Deposition temperature influence on the wear behaviour of carbon-based coatings deposited on hardened steel

Abstract

An evaluation regarding the influence of substrate material characteristics and deposition parameters on the tribological behaviour of carbon-based is presented. Chromium nitride interlayers and carbon-based thin films were deposited on hardened AISI 5115 case hardening steel, by magnetron sputtering. The physical vapour deposition (PVD) deposition was performed at three different temperatures: 180 °C, 200 °C and 250 °C. The chemical composition of the samples was assessed by Rutherford Backscattering Spectroscopy (RBS), the structure by X-ray Diffraction (XRD), and the surface morphology by Atomic Force Microscopy (AFM). The surface chemistry was analysed by X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The coatings are homogeneous, amorphous, with a smooth surface. The mechanical behaviour has been assessed on a pin-on disk rotational tribometer (wear characteristics), on a micro scratch tester (adhesion to the substrate), by ball-cratering (film thickness); by nanoindentation (hardness and the modulus of elasticity). A strong correlation between the substrate characteristics, but more importantly, of the deposition temperature, on one hand, and the mechanical characteristics, on the other hand, has been observed. The fracture toughness is positively influenced by the presence of the ceramic interlayer (chromium nitride). The modulus of elasticity and friction coefficient (both in dry conditions and lubricated) are decreased for higher deposition temperatures, however the higher deposition temperature negatively affects the hardness of the steel substrate.