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

Abstract

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 the pin undergoes two transitions: severe to mild at low load and mild to severe 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 densification and TiB₂ reinforcement lowers the specific wear rate and expands the mild‐wear load domain. However, even when the volume wear rate is normalised with respect to the real contact area (load/hardness) the non‐dimensional wear factor is still seen to decrease with densification and reinforcement. This indicates that fracture toughness may also play an important role in determining the wear‐resistance of these materials. The surface coverage on the pin by the mechanically mixed layer increases with densification and reinforcement.