Nickel enables nucleation and growth of well-oriented diamond crystals from the small lattice mismatch with diamond. However, its high solubility for carbon results in carbon loss during diamond deposition and, consequently, results in poor nucleation density. In this study, Ni/WC-6%Co specimens were carburized in a high-temperature furnace with inert gas atmosphere in order to provide nickel with sufficient carbon prior to diamond deposition. Two carburizing temperatures (750 C and 850 C) were set for 20 min and 60 min durations. The effect of this process in altering the nickel layer composition was characterized by microscopy, element analysis, and phase identification techniques. Scratch test was performed to evaluate the interface adhesion between the nickel layer and the substrate. The results show that the carburizing process led to the formation of different metallic phases, such as nickel carbide and cobalt nickel, which prevented carbon loss during diamond deposition as well as cobalt diffusion into diamond, and thus enhanced diamond nucleation and growth on the nickel surface.

Heat treatment processes have a positive impact in improving the adhesion strength of different interlayer/substrate materials. However, information regarding the effect of these processes in enhancing the adhesion strength of an electroplated nickel interlayer on tungsten carbide substrate for diamond deposition is lacking. In this study, the effect of carburizing and annealing process conditions in enhancing the adhesion strength of the electroplated nickel interlayer was investigated. The heat treatment processes were designed and modeled by the design of experiments technique. The heat-treated specimens were characterized by the field-emission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques. The adhesion of the interlayer before and after the heat treatment was assessed by the scratch test. The results show that the adhesion of the electroplated nickel interlayer was remarkably improved by both processes. The mathematical models for predicting the adhesion strength of the carburized and annealed nickel interlayer within the specified ranges were developed. The maximum adhesion strength of 30 N was obtained from the nickel interlayer annealed at the highest process condition of temperature and time.

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