Tribological behaviors of hot-pressed Al2O3/TiC ceramic composites with the additions of CaF2 solid lubricants

Al2O3/TiC ceramic composites with the additions of CaF2 solid lubricants were produced by hot pressing. The effect of the solid lubricant on the microstructure and mechanical properties of the ceramic composite has been studied. The friction coefficient and wear rates were measured using the ring-block method, and the tribological behaviors were discussed in relation to its mechanical properties and microstructure. Results showed that additions of CaF2 solid lubricants to Al2O3/TiC matrix led to a decrease in the flexural strength, fracture toughness, and hardness compared to a conventional Al2O3/TiC composite. The friction coefficient of Al2O3/TiC/CaF2 ceramic composites when sliding against both cemented carbide and hardened steel decreased with an increase in CaF2 content up to 15 vol.%. The reason is that the CaF2 released and smeared on the wear surface, and acted as solid lubricant film between the sliding couple. When the content of CaF2 solid lubricant is less than 10 vol.%, the wear rate of Al2O3/TiC/CaF2 composites decreases with an increase in CaF2 content, with further increases in CaF2 content, the wear rate of Al2O3/TiC/CaF2 composites increases rapidly. This is due to the large degradation of mechanical properties in samples with high CaF2 contents.