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.