The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

► Well-adhered DLC films without observable cracks were deposited on AZ91 Mg alloy by arc ion plating. ► Negative pulse bias voltage has a significant effect on sp3 carbon content and mechanical properties of DLC films. ► Wear resistance and surface hardness of AZ91 Mg alloy are significantly improved by coating with DLC film. ► AZ91 Mg alloy coated with DLC film exhibits a low friction coefficient and a narrow, shallow wear track.