Interface improvement of diamond/copper composites through a low-temperature high-efficiency coating method

A tungsten coating was formed by the in situ reaction of tungsten trioxide formed by the thermal decomposition of ammonium metatungstate in a molten salt (NaCl+BaCl₂) environment with carbon atoms on the surface of diamond. Meanwhile, diamond/copper composites were prepared using the prepared tungsten-coated diamonds. The morphology and composition of the coatings and diamond/copper composites were observed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive spectroscopy. The results revealed that the originally smooth diamond surface was uniformly covered by a tungsten coating after low-temperature salt bath treatment at 1050 °C, a temperature 50–100 °C lower than that of traditional methods. Compared to the directly added tungsten trioxide, the tungsten trioxide produced by the thermal decomposition of ammonium metatungstate was more active, and the coating was more uniform. The bending strength and thermal conductivity of tungsten-coated diamond/copper composites were 280.6 MPa and 516 W/(m·k), respectively, which were significantly higher than those of uncoated diamond/copper composites (128.6 MPa and 168 W/m·K). This indirectly confirms that the diamond surface coating can improve the interfacial bonding performance between diamond and copper.