Controlled Surface Flaws in Hot‐Pressed SiC

Abstract

Controlled semi‐elliptical surface flaws were produced in hot‐pressed SiC by Knoop microhardness indentation. Flawed specimens were placed in 4‐point bending in order to determine their critical stress intensity factor, K IC , at both room and high temperatures. Room‐temperature fracture and K IC values after annealing were sensitive to the annealing environment; this behavior correlated with the active/passive nature of the oxidation process. Flaw healing was observed for annealing exposures in air. Room‐temperature K IC values increased with increasing annealing temperature. High‐temperature K IC values decreased with increasing temperature as a result of a decrease in the fracture surface energy.