Modification of an Electroplated Nickel Interlayer Surface by Annealing Heat Treatment for Diamond Deposition on Tungsten Carbide

The tungsten carbide (WC-6%Co) substrate was coated with a nickel layer using the electrochemical deposition process to suppress cobalt diffusion during diamond deposition. However, the high solubility of nickel for carbon is a major issue, which hinders diamond nucleation and growth. Annealing heat treatment was conducted on the Ni/WC-6%Co specimens to reduce the interlayer solubility for carbon and enable diamond deposition. The heat treatment process was carried out inside a high-temperature tube furnace at two different temperatures (1050 and 850 °C) for a 60-min duration. Diamond was then deposited on the electroplated and heat-treated samples in a hot filament CVD reactor. Field emission electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analyzing techniques were used to characterize the heat-treated and diamond-coated samples. The results show that the annealing process could successfully modify the nickel-coated surface composition by the diffusion of tungsten. In addition, the annealed interlayer was able to suppress cobalt diffusion and promote the nucleation and growth of a continuous diamond film on the tungsten carbide substrate.