Effect of Nanometer WC Coating on Thermal Conductivity of Diamond/6061 Composites

Abstract

Diamond has poor interface tolerance with Al. To enhance interface bonding, in this study, tungsten carbide (WC) nanocoatings on the surface of diamond particles were prepared using sol–gel and in-situ reaction methods. WO₃ sol–gel with two concentrations, 0.2 mol/L, and 0.5 mol/L, was, respectively, coated on diamond particles, then sintered at 1250 °C for 2 h to produce WC nanocoatings. The concentration of 0.2 mol/L WO₃ sol–gel was not enough to cover the surface of the diamond completely, while 0.5 mol/L WO₃ sol–gel could fully cover it. Moreover, WO₃ was preferentially deposited on {100} planes of the diamond. WO₃ converted to WC in-situ nanocoatings after sintering due to the in-situ reaction of WO₃ and diamond. The diamond-reinforced Al composites with and without WC coating were fabricated by powder metallurgy. The diamond/Al composite without coating has a thermal conductivity of 584.7 W/mK, while the composite with a coating formed by 0.2 mol/L and 0.5 mol/L WO₃ sol–gel showed thermal conductivities of 626.1 W/mK and 584.2 W/mK, respectively. The moderate thickness of nanocoatings formed by 0.2 mol/L WO₃ sol–gel could enhance interface bonding, therefore improving thermal conductivity. The nanocoating produced by 0.5 mol/L WO₃ sol–gel cracked during the fabrication of the composite, leading to Al₁₂W formation and a decrease in thermal conductivity.