Indentation Fracture Toughness of Sintered Silicon Carbide in the Palmqvist Crack Regime

The fracture toughness of a sintered dense α‐SiC was estimated by the Vickers indentation microfracture method in the low‐load Palmqvist crack regime. It was observed that the use of simultaneously obtained Vickers hardnesses does not yield reliable fracture toughness values, nor does application of the median‐crack‐derived equations. It is necessary to utilize a load‐independent, crack‐free hardness value with this toughness estimation method. Although several of the curvefitting equations yield similar toughnesses, it is concluded for the Palmqvist crack system in this α‐SiC that the Niihara‐Morena‐Hasselman equation is the only one which yields fracture toughness values in agreement with conventional measurement techniques.