Microstructure and mechanical properties of hot-pressed Al 2O 3/TiC ceramic composites with the additions of solid lubricants

Abstract

Al 2O 3/TiC ceramic composites with the additions of different solid lubricants such as MoS 2, BN, and CaF 2 were produced by hot pressing. Effect of the solid lubricants on the microstructure and mechanical properties of this ceramic composite has been studied. No trace of MoS 2 was found in the sintered Al 2O 3/TiC/MoS 2 composite owing to its low melting point and escaping during the hot-pressing process. The flexural strength, fracture toughness, and hardness of Al 2O 3/TiC/MoS 2 composite continuously decreased with the increasing of MoS 2 content. AlN phase resulted from the reaction of Al 2O 3 with BN was formed in Al 2O 3/TiC/BN composite after sintering. Significant micro-cracks resulted from the residual stress owing to the difference in the thermal expansion coefficient were found on the polished surface, and caused large mechanical properties degradation for Al 2O 3/TiC/BN composite. While Al 2O 3/TiC/CaF 2 ceramic composite showed relative higher flexural strength, fracture toughness, and hardness compared with that of Al 2O 3/TiC/MoS 2 and Al 2O 3/TiC/BN composites owing its absence porosity and finer microstructure.