Tribological properties of graphite- and ZrC-reinforced bulk metallic glass composites

The influence of second-phase reinforcement on the micro-tribological properties of Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit 105) was investigated by ball-on-disc tests. It was found that monolithic amorphous Vit 105 displays a coefficient of friction (COF) similar to that of 100Cr6 bearing steel. Further, it was seen that adding a low volume content of graphite and especially of ZrC generates a significant decrease in the COF, of up to 50%. Amorphous Vit 105 and its graphite-/ZrC-reinforced composites typically display two regimes of COF. After 100–500 revolutions it drops to about 2/3 of the starting value, and jumps back up to the initial COF are also observed. These transitions take place within the space of about 10 revolutions and are accompanied by a significant change in wear track depth. Investigation of the wear rate indicates that the graphite-/ZrC-reinforced bulk metallic glass composites display an even lower wear rate than 100Cr6 bearing steel.