Sliding Wear and Micro-Tribological Behaviors of Mo<SUB>5</SUB>Si<SUB>3</SUB> Particle Reinforced Si<SUB>3</SUB>N<SUB>4</SUB> Composite

Mo5Si3 particle reinforced Si3N4 matrix composite was fabricated by sintering molybdenum solution-infiltrated porous Si3N4, and the microstructure, mechanical properties, sliding wear and micro-tribological behaviors of 2.8 mass%Mo5Si3-Si3N4 composite were studied. Because the grain boundary glass phases protruded from the surface approximately few nanometers compared with the Si3N4 grain after polishing, the grain boundary phases contacted with the sliding pair and failed earlier than the Si3N4 grains during the sliding wear. The failures of the grain boundary phases decreased the bonding of the Si3N4 grains, and accelerated the failure of Si3N4 grains. The severe failure of grain boundary phases indicated that the wear of the Si3N4 composite mainly depend on the grain boundary. By incorporating the Mo5Si3 particle to the grain boundary phases of Si3N4, not only the mechanical properties, but also the wear behaviors were improved. The friction coefficient and the wear rate of the Mo5Si3-Si3N4 composite were 0.52, 8.9×10−9 mm2/N, respectively, under dry condition, both values∼15% lower than those for the normal sintered Si3N4. The microtribological behavior of Mo5Si3-Si3N4 composite was evaluated using the friction force microscope, and the results indicated that the friction coefficient of Mo5Si3 was about 0.34∼0.47, lower than that of the Si3N4 grain. Mo5Si3 particle showed the lower friction resistance, and exhibited the self-lubricant behavior during the sliding wear.