Ultrasonic erosion of whisker-reinforced ceramic composites

Uniaxial hot-pressing of SiC whisker reinforced Al2O3 ceramic composites induces an anisotropy in whisker distribution and leads to a composite with anisotropic mechanical properties. In this paper, the effects of whisker orientation on the material removal rates and mechanisms in ultrasonic machining of Al2O3/SiCw ceramic composites are reported. It was found that the material removal rates and machined surface roughness in ultrasonic machining of the composites varied according to the angle θ to the hot pressing direction. The maximum material removal rate and surface roughness were observed for the machining surface perpendicular to the hot-pressing direction (θ=0°), and the minimum ones were observed for the machining surface parallel to the hot-pressing direction (θ=90°). This effect was larger for specimens with higher SiC whisker content. Based on the lateral crack fracture analysis in ultrasonic machining of the composites, the mechanisms responsible for the anisotropy in material removal rates caused by whisker orientation were investigated.