Conditions for the in-situ formation of carbide coatings on diamond grains during their sintering with CuWC binders |
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| Affiliation: | 1. School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300132, China;2. Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, Hebei University of Technology, Tianjin 300132, China;1. Vienna University of Technology, Institute of Chemical Technologies and Analytics, Vienna, Austria;2. Vienna University of Technology, Institute of Solid State Physics, Vienna, Austria;3. École Polytechnique Fédérale de Lausanne EPFL, Mechanical Metallurgy Laboratory, Lausanne, Switzerland;1. Production Technology Department, Faculty of Industrial Education, Helwan University, Cairo, Egypt;2. Powder Metallurgy Division, Manufacturing Department, Central Metallurgical Research and Development Institute, Egypt;3. Mechanical Department, Faculty of Industrial Education, Beni-Suef University, Egypt |
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| Abstract: | In present work, self-assembled WC/W coatings on diamond grains, sintered with Cu matrix were firstly obtained by gas phase transport mechanism. Conditions for spontaneous coating formation were also determined. The coatings can improve adhesion strength between diamond grains and a binder. Discovered method can be used for production of heat sink and heat spreader devices, as well as cutting tools. As functional additives (precursors) for coating formation, WC and WO3 were used. Morphology and composition of the coatings were identified by XPS, SEM, and TEM techniques. Coating consisting of mixture of metallic tungsten and tungsten carbide is formed on diamond when the Cu + WC binder is used. No coating is formed when copper is modified with WO3 nanoparticles; introduction of 20% Fe to the binder leads to formation of a coating containing 100% tungsten in metallic form. Hence, conditions for formation of the tungsten (tungsten carbide) coating onto the diamond surface during sintering with a metal binder include the presence of a nucleating agent WC and a metal that catalyzes graphitization. It was found that the driving force for spontaneous coating formation is a chemically activated gas-phase mass transfer of WO3 to the diamond surface, its chemisorption and subsequent reduction. |
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