Microstructure, adhesion and tribological properties of W–C:Hx% coatings deposited on M2 and WC substrates

W–C:Hx% coatings with slightly different hydrogen contents are deposited on AISI M2 steel and WC substrates using an unbalanced magnetron (UBM) sputtering process. The microstructure, adhesion and tribological properties of the W–C:Hx% coatings are found to vary with the hydrogen content. For a hydrogen content of more than 1.2 at.%, the microstructure of the W–C:Hx% coating changes from a columnar form to a featureless morphology. The adhesion of the coatings deposited on the WC substrates is significantly better than that of the coatings deposited on the M2 substrates. Of the various coatings, the W–C:H1.3% coating provides the best tribological properties, including the lowest wear depth and the lowest friction coefficient.