Machining damage analysis of alumina in relation to thermal shock behavior

Abstract

Machining damage of alumina disks with two different finishes, C and F, was analyzed with the aim of explaining the differences in their thermal shock responses. Thermal treatments designed to simulate conditions in thermal shock testing were performed on sets of C and F disks. The damage was quantified by several techniques, including the measurement of residual stresses. The mechanical strength of as-machined disks and thermally treated disks was also determined, including fractographic analysis. A decrease in the residual stresses after thermal treatment was observed in F specimens, as was expected. Conversely, unusual behavior was observed in C disks, showing a tendency to increase the residual stresses when the disks were kept at high temperature. Several factors were discussed to explain this fact. Higher mechanical strength and a decrease in the critical flaw size was observed in thermally treated disks compared to as-machined specimens for both types of finishes.