Thermal conductivity enhancement in cutting tools by chemical vapor deposition diamond coating

Two different types of chemical vapor deposition (CVD) diamond-coated tools have been investigated: W 300-1000 mum films brazed to WC-6 wt.% Co substrates; and (ii) 70-mum-thick films directly deposited on Si3N4-SiC composites. Thermal diffusivity perpendicular to the tool surface was measured up to 1000 degreesC by the laser flash method. Multiple-layer heat conduction models were used to appraise the effective thermal diffusivity of the film/substrate system. The thermal conductivity of the brazed samples increased up to 65% with respect to the hard metal substrate, evidencing a strong dependence on the diamond thickness. In the directly coated Si3N4 based tool substrates, the thermal diffusivity and the mean thermal conductivity increased up to similar to10%. (C) 2002 Elsevier Science B.V. All lights reserved.