Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China.
Corresponding author. Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, No. 3-11 Wenhua Road, Heping District, Shenyang, Liaon-ing Province, 110819, P. R. China. Tel: +86-24-83681726; Fax: +86-24-83681758; Email:wangq@mail.neu.edu.cn
Abstract:
At present, the functionally gradient cemented carbide (FGCC) substrate with enrich cobalt on surface is mainly formed from medium grained WC grains. In order to further improve the properties of gradient cemented carbides, the ultrafine powder was chosen in this study and the functionally gradient cemented carbide with ultrafine grains was prepared by a two-step process, where the cemented carbide is first lower pressure pre-sintered and then subjected to a gradient sintering. The results show that it is possible to form gradient layer with enriched cobalt on surface by this method and also the grain growth can be inhibited by low pressure pre-sintering. Ultrafine grain gradient cemented carbide was fabricated after the gradient sintering, the thickness of gradient layer was about 43μm and the average grain size of WC is about 0.42μm. The formational mechanism of the functionally gradient cemented carbide with ultrafine grains are discussed through analyzing the influence of ultrafine microstructure, which was obtain by lower pressure pre-sintering, on atomic diffusion and grain growth during gradient sintering process.
