Effects of sputtering condition on tribological properties of tungsten coatings

Tungsten coating is often used for tribological applications, especially for those at elevated temperatures due to its high melting point and good wear resistance. In this study, research was conducted to investigate the tribological behavior of tungsten coatings produced at various temperatures using a double glow discharge technique. The relationships among the coating’s microstructure, their properties and the deposition temperature were studied. The microstructure of the coatings was examined using optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Hardness and elasticity of the coatings were evaluated using a nano/micro-mechanical probe. Wear and friction of the coatings against a ceramic ball at various temperatures were evaluated using a high-temperature pin-on-disc tribometer. It was demonstrated that raising the substrate temperature from 400 to 1100 °C changed the microstructure of tungsten coatings from tapered grains with voids at boundaries to finer fibrous structure with fewer voids. The results illustrated that the mechanical and tribological behavior of a tungsten coating was strongly affected by its microstructure. The coating that was formed at the highest substrate temperature, 1100 °C showed, the best friction and wear behavior.