Research on the mechanical and tribological properties of Mo–Si/Si3N4 composite at elevated temperature

Abstract

Silicon nitride with 5, 10 and 20 wt.% molybdenum addition (Mo-Si/Si 3 N 4 composite) was prepared by spark plasma sintering and its mechanical and tribological properties at RT, 300, 600 and 900 °C were systematically investigated. When the test temperature below 600 °C, the multiple effects of in-situ generated Mo-Si compounds on cracks, including deflection and closure during the initiation stage and deflection and bridging during the crack propagation, effectively improved the fracture toughness of Mo-Si/Si 3 N 4 composite. Furthmore, Mo-Si/Si 3 N 4 composite exhibited excellent tribological properties at elevated temperature, which rely on the substrate protection through the generation of MoO 3 tribofilm. Especially, at 600 °C, the sample with 20 wt.% Mo addition showed only 8.1×10 -6 mm -3 /Nm in wear rate while monolithic Si 3 N 4 showed 1.5×10 -3 mm -3 /Nm in wear rate, resulted in a three-order-of-magnitude decrease in wear.