抄録
The dependence of fracture toughness estimated by indentation fracture technique on measuring method was studied using several Si3N4 samples with various microstructures. The crack length at the indentation load of 19.6 N was measured by optical microscopy and SEM and fracture toughness was calculated for each case. The consistency of results between the two methods was obtained within the accuracy of the data for any microstructure. It was revealed that in the case of silicon nitrides indented at low load, the IF technique was not so equipment sensitive, indicating that the accuracy of IF method by OM is not necessarily inferior to one by the SEM. It was considered that the IF method with optical microscopy would become useful test for fracture toughness if the testing procedure is properly controlled to minimize the source of the measuring error.
