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

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. WO 3 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 WO 3 sol–gel was not enough to cover the surface of the diamond completely, while 0.5 mol/L WO 3 sol–gel could fully cover it. Moreover, WO 3 was preferentially deposited on {100} planes of the diamond. WO 3 converted to WC in-situ nanocoatings after sintering due to the in-situ reaction of WO 3 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 WO 3 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 WO 3 sol–gel could enhance interface bonding, therefore improving thermal conductivity. The nanocoating produced by 0.5 mol/L WO 3 sol–gel cracked during the fabrication of the composite, leading to Al 12 W formation and a decrease in thermal conductivity.