Apparent yield strength of hot-pressed SiCs

Apparent yield strengths (Y _App) of four hot-pressed silicon carbides (SiC-B, SiC-N, SiC-HPN, and SiC-SC-IRN) were estimated using diamond spherical or Hertzian indentation and the considerations of the von Mises and Tresca yield criteria. The developed test method was robust, simple and quick to execute, enabling the acquisition of confident sampling statistics. The choice of indenter size, test method, and method of analysis are described. The compressive force necessary to initiate apparent yielding was identified postmortem using differential interference contrast (or Nomarski) imaging with an optical microscope. It was found that the Y _APP of SiC-HPN (14.0 GPa) was approximately 10% higher than the equivalently valued Y _APP of SiC-B, SiC-N, and SiC-SC-1RN. This distinction in Y _ApP shows that the use of this test method could be valuable because there were no differences among the average Knoop hardnesses of the four SiC grades.