The effect of microstructure on the tribological behaviour of monolithic Si3N4 and Si3N4-SiC composites

The tribological behaviour of various Si3N4 based materials, including Si3N 4/SiC composites, has been analysed from room temperature up to 700 degrees C, and for sliding speeds between 0.5 and 2 m/s. Materials have been prepa red by hot pressing at 1750 degrees C in nitrogen atmosphere, varying alpha -Si3N4 phase content, microstructure coarseness and shape and size of the S iC particles. Wear tests were performed in self-mated pairs using a pin on disc tribometer, without lubrication and at a fixed load of 5 N. Pin and di sc worn surfaces were observed by scanning electron microscopy (SEM-EDS). D ebris generated during tests was analysed by SEM-EDS and X-ray diffraction (XRD). Results showed friction, f, and wear coefficients, K, above 0.3 y 10 (-6) mm(3)N(-1)m(-1), respectively. Wear mechanism depended, on the microst ructure and the mechanical properties of the materials.