Surface roughness effect on the friction and wear of bulk metallic glasses

This paper investigates the effect of surface roughness on the friction and wear of bulk metallic glasses (BMGs). The pin-on-disk tests were carried out with the BMG pins of Ti40Zr25Ni3Cu12Be20 (Ti-BMG) and Cu47.5Zr47.5Al5 (Cu-BMG) sliding against an EN26 steel disk. It was found that the deformation of asperities prior to the contact sliding increases the asperity plasticity and plays an important role in the variation of the tribological properties of the materials. Although the friction coefficient and wear resistance of both the BMGs increase with the surface roughness, their mechanisms are different. The Ti-BMG experienced a typical abrasive wear, but the Cu-BMG went through an adhesive wear process. The wear resistance of the Cu-BMG is much higher although its hardness is almost the same as that of the Ti-BMG. The study concludes that it is mainly the higher plasticity of the Cu-BMG that leads to its better wear resistance, although the material layer transferred to the disk surface during sliding could have also influenced the wear rate.