Effect of MoSi2 content on the lubricated sliding-wear resistance of ZrC-MoSi2 composites

The effect of MoSi2 content (5, 10, and 20 vol.%) on the lubricated, sliding-wear behaviour of ZrC-MoSi2 composites at room temperature is investigated and modeled. It was found that the resistance to sliding wear decreases markedly with increasing MoSi2 content, with a greater rate of mild wear, an earlier transition from mild to severe wear, but essentially the same rate of severe wear. The analysis of the wear results using a mechanistic model indicated that the worsened sliding-wear resistance with the increase in MoSi2 content derives from the decreased hardness and increased internal effective tensile stresses of the ZrC-MoSi2 composite, which speed up the accumulation of damage induced by plastic deformation within the grains and shorten the onset of the grain-boundary fracture condition and subsequent grain pullout. Reduction of the MoSi2 content thus emerges as an effective approach for making the ZrC-MoSi2 composites more sliding-wear resistant under lubrication at room-temperature. These results may have important implications because ZrC holds promise for use in tribological applications requiring both wear resistance and electrical contact, and MoSi2 is its commonest sintering additive.