Fabrication and Evaluation of the High-Temperature Bending Strength for Mo₂NiB₂-Ni Cermets

抄録

Mo₂NiB₂-Ni cermets, a type of boride-based cermet, exhibit attractive mechanical properties such as high hardness and good wear resistance. However, the mechanical properties of these cermets have predominantly been evaluated at room temperature. In this study, three-point bending tests were conducted at high temperatures to investigate the mechanical properties and fractography of Mo₂NiB₂-Ni cermets. A ternary Mo₂NiB₂-Ni cermet was prepared using a calcination process to synthesize Mo₂NiB₂ before sintering. The calcination process resulted in finer and more uniform Mo₂NiB₂ particles, enhancing the microstructure. Consequently, hardness and transverse rupture strength (TRS) were improved. Three-point bending strengths were measured for samples measuring 4.0 × 3.0 × 24 mm at temperatures up to 800°C in an argon environment, using silicon carbide jigs with a 16 mm span. The results indicated that TRS remained approximately constant at about 1.6 GPa up to 500°C but decreased sharply above 600°C, reaching about 0.12 GPa at 800°C. This decrease was attributed to the softening of the nickel binder phase, which adversely affected the TRS.