High-temperature flexural strength and reliability of Ti(C5N5)-TiB2-(W7Ti3)C composite cermet tool material

Abstract

Abstract In this study, Ti(C5N5)-TiB2-(W7Ti3)C composite cermet tool material was fabricated, and variation of its high-temperature flexural strength was investigated. Results indicated that 800 °C was the deflection point of the high-temperature flexural strength of the Ti(C,N)-TiB2-(W,Ti)C composite cermet tool material. Distribution function for the measured high-temperature flexural strength and corresponding reliability function were established. With the increase in temperature above 800 °C, high-temperature flexural strength of Ti(C,N)-TiB2-(W,Ti)C composites decreased rapidly, which was attributed to microstructural damage caused by oxidation, softening of the metallic phase at high temperatures, reduction of interfacial bonding strength, reduction of the elastic shape parameter at high temperatures, and release of residual stress. The distribution of measured flexural strength for Ti(C5N5)-TiB2-(W7Ti3)C composite at 800 °C could well obey a Weibull distribution function. The Weibull distribution shape parameter was found to be higher at 800 °C than that at room temperature, and the distribution of flexural strength was less discrete at 800 °C than that at room temperature. For a reliability of 0.9, reliable flexural strength of Ti(C5N5)-TiB2-(W7Ti3)C composite at 800 °C was about 688 MPa, which satisfies cutting tool manufacturing requirements. The reliability can serve as reference for the determination of suitable high-speed cutting parameters.