Evaluation of the quality of composite diamond-containing materials by their electrical and thermal conductivity

Abstract

The serviceability of hot-pressed diamond-containing composite materials for application in tools depends substantially on the presence of microdefects, in particular, the residual porosity of the metal matrix, damaged diamond grains, and imperfect diamond-matrix interfaces. Experimental investigations of these defects are very difficult due to their small size and nonstandard shape as well as a strong inhomogeneity of the specimens. We propose an alternative technique of the nondestructive testing of the quality of diamond-containing composite materials, which includes measurement of the electrical resistance and thermal conductivity of a diamond-containing composite and analysis of the data obtained by the methods of composite mechanics. The quantitative estimate of quality is given in terms of two dimensionless parameters. The first of them, 0 < K < 1, reflects the quality of a sintered metal matrix, whereas the second, 0 < R < 1, is an aggregate measure of the integrity of diamond grains and the degree of perfection of the interfaces in a composite. The good agreement between theory and experiment corroborates the efficiency of this technique and the accuracy of the presented data.