Dynamic fatigue behavior of Si3N4-based ceramic tool materials at ambient and high temperatures

Abstract

Dynamic fatigue behaviors of three microwave-sintered Si3N4-based ceramic tool materials in ambient and high-temperature (800 °C) environments were investigated. The flexural strength at different loading rate (0.05 MPa/s, 0.5 MPa/s, 5 MPa/s and 15 MPa/s) was conducted by three-point bending test. The results showed that the subcritical crack growth parameter N of monolithic Si3N4, Si3N4/(W,Ti)C and Si3N4/(W,Ti)C/Ni at ambient temperature was 57.5, 34.8 and 81, respectively. The fatigue resistance performance at ambient temperature was ranked as Si3N4/(W,Ti)C/Ni > monolithic Si3N4 > Si3N4/(W,Ti)C. As the temperature increased to 800 °C, the flexural strength of all samples only decreased slightly, which indicated Si3N4-based ceramic tool materials had good thermal stability. The subcritical crack growth parameter N of monolithic Si3N4 and Si3N4/(W,Ti)C ceramic tool materials did not change, while the value N of Si3N4/(W,Ti)C/Ni decreased by 76.5%. The addition of metal phase can increase the ambient temperature fatigue resistance, while it is detrimental to the high-temperature fatigue resistance due to its weak strength at high temperature. Additionally, defect source caused by the oxidative corrosion was also not conducive to fatigue resistance performance of Si3N4-based composite ceramic tool materials at high temperature.