Effect of densification and TiB2 reinforcement on the wear of molybdenum disilicide

Wear tests were done in a pin-on-disc machine by sliding MoSi2 pins against hard-steel discs in a normal load range of 5-140 N and a speed of 0.5 m/s under nominally dry conditions in the ambient. The specific wear rate of th e pin undergoes two transitions: severe to mild at low load and mild to sev ere at high load. The mild-wear domain is distinguished by the formation of a protective mechanically mixed layer of steel and its oxides, transferred from the counterface in particulate form. Increasing the hardness by densi fication and TiB2 reinforcement lowers the specific wear rate and expands t he mild-wear load domain. However, even when the volume wear rate is normal ised with respect to the real contact area (load/hardness) the non-dimensio nal wear factor is still seen to decrease with densification and reinforcem ent. This indicates that fracture toughness may also play an important role in determining the wear-resistance of these materials. The surface coverag e on the pin by the mechanically mixed layer increases with densification a nd reinforcement.