WEAR MECHANISMS AND TRIBO MAPPING OF AL2O3 AND SIC IN DRY SLIDING

The wear and friction behaviour of Al2O3 and SiSiC have been investigated over a broad range of normal loads and sliding velocities. The dominating wear mechanisms have been identified and are illustrated in wear mechanism maps outlining the boundaries separating different wear regimes. Friction maps have been constructed to illustrate the influence of load and speed on the coefficient of friction. The Al2O3 has two primordial wear regimes, one mild with extremely low specific wear rates, 10(-10)-10(-9) mm(3) Nm(-1), and one severe with wear rates several orders of magnitude higher. The coefficients of friction in the mild regime were below 0.6 and in the severe above 0.6. The SiSiC showed three wear regimes determined by prevailing tribe chemical reactions. A passive tribo oxidation regime occurred at low loads and was characterised by extensive silica (SiO2 formation. An active tribo oxidation regime occurred at higher toads and featured silicon monoxide (SiO) formation. At the highest loads of these tests macro surface fracture was the dominating mechanism. The specific wear rates were in passive conditions below 10(-5) mm(3) Nm(-1) and under active oxidation above 2X10(-5) mm(3) Nm(-1).