Effect of alpha-/beta Si3N4-phase ratio and microstructure on the tribological behaviour up to 700 degrees C

The present work analyses the effect of mechanical and microstructural char acteristics in the tribological behaviour of Si3N4 materials. Special atten tion was given to the alpha/beta phase ratio and the coarseness of the micr ostructure. Wear experiments were performed in a pin-on-disc tribometer usi ng self-mated Si3N4 pairs varying the sliding speed and the test temperatur e. In the case of fine and medium microstructures, fracture and delaminatio n was the main wear mechanism while for heterogeneous coarse material defor mation related to intergranular microfracture was prevalent. The latter pre sent higher wear rates at room temperature and low sliding speed but showed the best wear resistance when either sliding speed or temperature were inc reased. (C) 2000 Elsevier Science S.A. All rights reserved.