Dry sliding wear behavior of an Si-Al-O-N ceramic

Dry sliding wear tests were conducted on (Si-Al-O-N)-cast iron sliding pairs using a wear tester specifically designed to simulate closely the high pressures, velocities and resultant temperatures encountered in heavily loaded machinery and other engineering applications. A wear tester was designed so that both the contact load level and the sliding velocity could be varied. Wear testing indicated that, following a short wear-in period, mass loss varied linearly with sliding distance for all contact loads and sliding velocities investigated. The steady state wear rates, expressed in terms of mass loss per unit sliding distance, were found to increase as the applied contact load was increased for all the sliding velocities investigated. Further, the wear rate was found to vary inversely with sliding velocity for the highest contact load level investigated. For the intermediate and lowest contact load levels, this inverse relationship between velocity and wear rate (i.e. reduced wear for higher velocities) was less pronounced and restricted to the lower range of velocities investigated. Several different grinding procedures were used to prepare the specimens prior to wear testing but were found to have no significant influence on the measured wear rates. The experimental results are qualitatively explained by considering combined wear mechanisms involving brittle fracture and plastic deformation, which depend on the relative magnitudes of contact load and sliding velocity. Brittle fracture is assumed to be the primary wear mechanism especially at high contact loads and low sliding velocities. Plastic deformation mechanisms are also active and intensify with increasing frictional heating and concomitant thermal softening.