Effect of SiC-coated diamond and its size on the relative density and thermal conductivity of diamond/W composites

In this study, SiC coating was deposited on the diamond surfaces by magnetron sputtering, and SiC-coated diamonds with a diamond size of 100–400 μm were employed to prepared diamond(SiC)/W composite for improving the interface bonding and thermal conductivity. The effects of SiC coating and diamond size on the interfacial bonding, evolution of interfacial structure and thermal conductivity of composite were investigated. The results showed that a relatively homogeneous SiC coating was formed after 16h of deposition at a sputtering power of 150W. At a diamond size of 200 μm, when the diamond addition was lower than 40 vol%, through W-SiC interface reaction, SiC coating can improve the interface bonding, and increase the relative density and thermal conductivity of composites. As the diamond addition increased to 50-60 vol%, the enhanced degree of W-SiC reaction would lead to the broken and migration of WC-SiC layer under the action of sintering temperature, pressure and local Joule heat, causing an increase in interface defects and a decrease in thermal conductivity of composites. 40 vol%diamond(SiC)/W composite achieved the higher thermal conductivity of 152 W m⁻¹ K⁻¹. Increasing the diamond size would help increase the densification and heat transfer efficiency of composite, and 40 vol%diamond(SiC)/W composite with a diamond size of 400 μm possessed the maximum relative density and thermal conductivity, i.e. 96.78 % and 225 W m⁻¹ K⁻¹.