Tribological behaviors of hot-pressed Al 2O 3/TiC ceramic composites with the additions of CaF 2 solid lubricants

Abstract

Al 2O 3/TiC ceramic composites with the additions of CaF 2 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 CaF 2 solid lubricants to Al 2O 3/TiC matrix led to a decrease in the flexural strength, fracture toughness, and hardness compared to a conventional Al 2O 3/TiC composite. The friction coefficient of Al 2O 3/TiC/CaF 2 ceramic composites when sliding against both cemented carbide and hardened steel decreased with an increase in CaF 2 content up to 15 vol.%. The reason is that the CaF 2 released and smeared on the wear surface, and acted as solid lubricant film between the sliding couple. When the content of CaF 2 solid lubricant is less than 10 vol.%, the wear rate of Al 2O 3/TiC/CaF 2 composites decreases with an increase in CaF 2 content, with further increases in CaF 2 content, the wear rate of Al 2O 3/TiC/CaF 2 composites increases rapidly. This is due to the large degradation of mechanical properties in samples with high CaF 2 contents.