Effects of Al2O3 and NbC additives on the microstructure and mechanical properties of TiB2-TiC composite ceramic cutting tool materials

A study of the effects of Al2O3 and NbC additives on the microstructure and mechanical properties of TiB2 TiC composite ceramic cutting tool materials is presented. The relations of the room temperature and high-temperature mechanical properties to the microstructure of the composite were investigated. The Al2O3 additive was determined to slightly increase the flexural strength and fracture toughness of the composite at room temperature and significantly increase the flexural strength of the composite at high temperatures. The superfine NbC additive improved the room-temperature flexural strength of the composite by approximately 30%. The microstructure was refined, and the resultant mechanical properties were improved if Al2O3 and NbC were added to the composite together. The flexural strength of the TiB2-TiC+Al2O3+NbC composite material still exceeded 500 MPa at 800 degrees C, which can meet the demands of cutting tool materials. The quick degradation of the high-temperature flexural strength of the composite above 800 degrees C was mainly due to the softening of Ni binder phase. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.