Performance test of indenters made of CVD diamond used for scratch tester

The indenter tip of a scratch tester used for measuring adhesion of hard films is conventionally made of singlecrystal natural diamond. However, it has the problem of a short lifetime due to its tendency to cleave, leading to our attempt to replace it with CVD polycrystalline diamond. This paper deals with the results of an evaluation test in which two kinds of indenter tips were subjected to repeated scratch operations using an actual tester; one tip was made of single-crystal natural diamond and the other was made of 0.7mm-thick CVD wlycrystalline diamond. The following results were obtained; (1) The tip made of polycrystalline CVD diamond has a lifetime two or three times longer than that made of single-crystal natural diamond. (2) Single-crystal diamond indenter shows strong dependency on the relationship between crystal direction, scratch direction and loading direction as to the measured critical load value even when used for the same film sample, thus leading to a necessity to control the crystal on loading directions in order to obtain a well defined critical load value. (3) Polycrystalline diamond is free from a necessity to control crystal orientation in manufacturing good quality scratch indenters in terms of the said scatter.