Quality rating of a metal matrix-diamondcomposite from its thermal conductivity and electric resistance |
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Authors: | N V Novikov A L Maystrenko V I Kushch S A Ivanov |
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Institution: | (1) N. V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, 2 Avtozavodskaya St., 04074 Kiev, Ukraine |
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Abstract: | The efficiency of hot-pressed diamond-containing composite materials (DCM) for various tool applications is greatly affected
by microdefects, namely, the residual porosity of the metal matrix, damaged diamond grains, and imperfect diamond-matrix interfaces.
An instrumental evaluation of these microdefects, predetermining the quality of a tool equipped with DCM, is rather difficult
due to the small size, the nonstandard shape, and the strong heterogeneity of specimens. Proposed here is an alternative,
nondestructive technique of DCM quality rating, which includes the measurement of electric resistance and thermal conductivity
of diamond-containing composites and processing the obtained data by the methods of composite mechanics. It exploits the fact
that diamond, being a dielectric, possesses an extremely high thermal conductivity, which allows estimating the residual porosity
of a sintered metal matrix from the ratio of specific electric resistances, one being measured and another predicted by a
theory. These data, in turn, are utilized to predict the thermal conductivity ofDCMwith an imperfect matrix. Matching with
experiments, after solving the inverse problem gives the thermal resistance of diamond-matrix interface, which, within the
frame work of the given model, simulates the damage of both the diamond grains and their bonds with the matrix. Thus, the
numerical rating of quality is given in terms of two dimensionless parameters. The first one, 0 < K < 1, reflects the quality of the sintered metal matrix, whereas the second one, 0 < R <1, is an aggregate measure of the integrity of diamond grains and the perfection degree of composite interfaces. The quite
satisfactory agreement observed between the theory and experiment confirms the efficiency of the technique and the reliability
of the data obtained.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 361–374, May–June, 2006. |
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Keywords: | diamond-containing composites imperfections nondestructive testing thermal conductivity electric resistance quality rating |
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