The influence of bias voltage on structure and mechanical/tribological properties of arc evaporated Ti–Al–V–N coatings

Abstract

Titanium aluminium vanadium nitride (Ti–Al–V–N) has recently been introduced as a possible candidate for further development of titanium aluminium nitride based coatings, e.g. for low friction applications. The aim of the present work is to investigate the influence of the bias voltage on structure, chemical composition and residual stresses as well as mechanical and tribological properties of Ti–Al–V–N coatings, in order to illuminate the possibility of tailoring the coating properties mentioned above. An industrial scale cathodic arc evaporation facility was used to deposit the coatings from powder metallurgically produced Ti 16.5Al 67V 16.5 targets onto cemented carbide and silicon samples at bias voltages ranging from − 40 to − 160 V. Investigations on coating structure by glancing angle X-ray diffraction displayed a change from a dual-phase structure with cubic and hexagonal phases to a single-phase cubic structure with increasing bias voltage. Nano-indentation and stress determination by laser-assisted curvature measurement yielded a hardness increase from 27.6 to 38 GPa and compressive stress values increase from 0.4 to 1.3 GPa for coatings deposited at − 40 and − 160 V bias voltage, respectively. The Young's modulus was found to increase from 349 GPa at − 40 V to a maximum value of 532 GPa for − 120 V bias. Ball-on-disc tests at room temperature indicated increasing negative wear with bias voltage, which is related to droplet-generated surface roughness. At 500 °C, negative wear was almost completely prevented, due to a tribologically formed protective oxide layer.