Scratch behavior of SiAlON ceramics

The mechanical response of four different types of hot pressed yttrium stabilized α/β composite SiAlON ceramics was investigated by scratch testing in order to interpret their severe wear behavior. A progressive loading scratch tester with both rough and smooth spherical diamond styluses was used to analyze the variation in mechanical response with roughness of stylus. The extent of subsurface damage produced by the different styluses on a 50% β-content composite was also investigated using a visualization technique with plasma etching, which has been previously developed by one of the authors. When scratched by the rough stylus, quasi-plastic deformation recognized in the form of grain release after plasma etching was present predominantly in the surface, and the use of this stylus was regarded to be more appropriate for comparing the results of scratch tests with those of severe wear due to similarity of crack formation between grain dislodgement in severe wear and subsurface damage in the scratch tests. The work required to produce damage and groove formation (Wdg) when scratched by the rough stylus was evaluated for all test materials and it was found that the worn volume under severe wear follows the reverse order of Wdg.