Quantitative determination of the adhesive fracture toughness of CVD diamond to WC-Co cemented carbide

Well-separated diamond particles were nucleated and grown by hot filament c hemical vapor deposition (HFCVD) onto WC-Co cemented carbide pretreated by Murakami's reagent and H2O2 + H2SO4 solution. The adhesive strength of diam ond particles to WC-Co cemented carbide was quantitatively determined in te rms of interface toughness by directly applying an external load to the CVD diamond particles. From the measurement of the maximum load required to sc ratch off the particles, we determined that the adhesive toughness was 14 J /m(2). This value is more than twice as high as that of CVD diamond on smoo th silicon substrate and comparable to the cleavage fracture energy of diam ond. The newly developed procedure will allow to check the effectiveness of substrate surface pretreatments for further improving the adhesion level o f diamond films on WC-Co. (C) 2000 Elsevier Science S.A. All rights reserve d.