Effect of temperature and counterface on the tribological performance of W-DLC on a steel substrate

Diamond-like carbon coatings are used in a variety of applications to improve tribological performance. Many of the tests to assess friction and wear rate of the coatings are carried out at room temperature despite the fact that in service the coatings are often used at higher temperatures. Thus, the effect of elevated temperature testing the tribological performance of a tungsten carbide-doped a-C:H coating (W-DLC) deposited by physical vapour deposition onto a steel substrate has been characterized using elevated temperature scratch testing and multi-pass scratch testing. Pin-on-disk wear testing has been conducted at room temperature against both a steel and DLC counterface to assess the effect of hardness and tribochemistry on the wear mechanism. Additionally, the mechanical properties of the coating have been assessed using nanoindentation testing at room temperature and at temperatures up to 400 °C. The deformation and wear modes have been characterised using scanning electron microscopy. The results show that even relatively modest temperature increments can have a large effect on the tribological properties.