Microstructure - Mechanical Properties - Wear Resistance Relationship of SiAlON Ceramics

In designing wear-resistant ceramics, it is important to understand the influence of the microstructure and material properties on friction and wear behavior. In addressing such issues, a series of fretting-wear tests was carried out on an important nonoxide engineering ceramic, i.e., SiAlON ceramics, densified using both pressureless and gas-pressure sintering routes. Under the selected operating conditions with a commercial SiAlON ball as a counterbody, tribomechanical wear assisted by deep abrasive grooves, plowing, grain pullout, and microcracking was observed as the major wear mechanism. In addition, the formation of a discontinuous silica-rich tribochemical layer on the worn surface was also observed. Although the steady-state coefficient of friction (COF) varies in a narrow window of 0.59 to 0.64, the wear rate of the investigated SiAlON ceramics lies in the range 7.3 × 10^-6 to 8.4 × 10^-5 mm³ /Nm. An attempt has been made to correlate wear loss with hardness and indentation toughness. Concerning the influence of the microstructure, the wear rate is found to have an inverse linear correlation with the β-SiAlON content. Another important observation has been that the wear rate has an inverse linear relationship with the substitution parameter (z).