セラミックス被膜への圧子押込みにおける破壊発生機序に対する圧子サイズの影響に関する研究

抄録

Cracking is studied for a ceramic film coating (Al₂O₃) on a metal substrate (WC-Co) subjected to indentation by a spherical diamond indenter. The focus of the study is the pattern of crack growth and apparent variation of strength of the film with respect to size of indenters. To this end, we perform indentation experiments with indenters of five different radii. Based on the experimental results and FEM stress analysis, we discuss the apparent strength of the ceramic film using a Weibull distribution. It is found that only radial cracks are induced for a smaller indenter, but only circumferencial cracks are induced for a larger indenter. It is also revealed that the apparent strength of the film is strongly dependent on the size of indenters. For indenter radii above 500 μm, the variation of apparent strength with respect to the size of indenters is not so strong. Thus, the use of an indenter with a radius larger than 500 μm is recommended in order to obtain valid results. "