SEIZURE AND WEAR IN ALUMINA CERAMICS.

Alumina ceramics and bearing steel were tested in a four ball tester to determine their properties in seizure and wear. A load range per unit ball of 66 to 871 N and a sliding velocity range of 0. 095 to 0. 630 m/s were selected. Turbine oil was used as the lubricant in this test. The coefficient of friction of alumina ceramics in seizure increased gradually to 0. 4 with the load, while that of bearing steel increased abruptly to 0. 4 regardless of load. After seizure the coefficient of friction of alumina ceramics increased with the load from 0. 1 to 0. 15, while that of bearing steel remained at 0. 1 regardless of the load. The sliding distance of seizure in alumina ceramics was about 2 m when the sliding velocity was 0. 288 m/s, but that in bearing steel increased with the load. It was found that the wear rate in seizure increases with the sliding velocity and load. Scanning electron microscope observations revealed that the wear mechanism in alumina ceramics was related to brittle fracture and plastic deformation, but brittle fracture predominated when seizure occurred.