Wear test of alumina-on-alumina sliding pairs as model experiment for wear in ceramic-on-ceramic joint prostheses

Abstract

Wear behavior of an alumina-on-alumina sliding pair was evaluated in a pin-on-disk wear test to estimate the effect of material composition and microstructure of alumina ceramics on the wear property of a ceramic-on-ceramic joint prosthesis. To eliminate the polyethylene wear problem, applications of ceramic-on-ceramic joint prostheses are growing because of its high wear resistance. However, some ceramic-on-ceramic hip joints also showed progressive loosening related to a significant wear of the alumina surface. Therefore, the alumina ceramics for ceramic-on-ceramic artificial joints must have a superior wear resistance to achieve long-term durability. In this study, wear behavior of several kinds of alumina ceramics was examined in uni-directional sliding wear tests by using a pin-on-disk test apparatus. Purity, density and microstructure, such as a mean grain size and number of flaws, of these alumina ceramics vary according to the preparation process as well as properties of the alumina powder. Hot isostatic pressing (HIP) and centrifugal compaction (CC) developed by Tashima et al were used to modify the microstructure and the mechanical properties of alumina ceramics. In these experiments, a pin specimen was matched with a disk specimen prepared from the same alumina ceramics and distilled water and diluted bovine serum were used as lubricants to simulate the tribological condition of a ceramic-on-ceramic hip joint prosthesis. Concerning results, alumina with high purity and a relatively small grain size showed the highest wear resistance. Moreover, the wear properties of alumina ceramics could be improved by means of HIP and CC. The observation of the worn surface indicated that two different wear mechanisms operated simultaneously. One was a removal of alumina grains and another was microscopic adhesive wear occurring at the surface of alumina grains. The preparation process and resulting microstructures of alumina ceramics had a significant effect on both the alumina grain removal and the microscopic adhesive wear.