Nanocrystalline WC-Co HVAF-coatings by utilizing novel powder manufacturing route

In this study nanostructured WC-Co coatings were produced using experimental nanocrystalline WC-12Co and WC-24Co powders produced by a novel chemical synthesis route using water-soluble raw materials. Test coatings were produced using HVAF-spraying keeping the temperature as low as possible during the deposition in order to avoid decomposition of the nanocarbides. In experimental powders, two different Co incorporation methods were used: a conventional way in which cobalt was incorporated as a metallic Co powder and a chemical synthesis way in which cobalt acetate was used as a cobalt source. When using cobalt acetate it decomposes to metallic cobalt during the process. The effect of a cobalt origin (pure Co powder, cobalt acetate) on inhibition of carbide grain growth, deposition efficiency (DE) and carbide decomposition of the resulted HVAF-coatings was studied. As a research hypothesis, experimental powders with cobalt acetate as a cobalt source enable more homogenous distribution of the metal matrix in comparison to the conventional powders, in which cobalt has been incorporated as a metallic powder. The homogenous cobalt distribution is achieved via a novel powder manufacturing route using water-soluble raw materials.