Crystallization Of Tungsten Carbide Processed By Plasma In-Situ Metallurgy

WC-based composite material was successfully fabricated by plasma in-situ metallurgy to break through the bottleneck of powder metallurgy cemented carbide in this paper. Microstructure and mechanical property were analyzed, reaction between W and C and the crystallizing process of WCP in a high temperature and C-rich situation were discussed.The structure analysis results reveal that level of electric current would influence the mouldability of the final composite; Main phases in the composite obtained by plasma in-situ metallurgy are WC,W2C,M6C (Fe3W3C),y-Fe and small amount of Cr7C3 and (Fe, Ni)3C.The composite has a uniform microstructure and the triangle and rectangle shape hard phase is with the length of 5-30μm.During the heating process of plasma in-situ metallurgy, the synchronously feeding powder and the matrix melst and form a molten bath together. Gases and slag produced by the intense reactions in the metallurgy area float upon. Once the crystal nucleus formed, it would grow up with a smooth solid-liquid interface.During the crystallization of WC, the anisotropy of crystal faces causes different surface energy of different crystal faces, then determine specific guillotine factor r and elongation k,then WC grain with characteristic of special morphological formed. WC crystal grow up along the crystal orientation<0001> based on (0001) crystal face because of the special construction of crystal and complex interfaces.The average hardness of all the prepared WC composite materials could exceed HRA82. The WCP phase has the highest hardness and the microhardness of it can reach above 2000HV0.2; the microhardness of Fe3W3C phase can reach above 1100 HV0.2; the microhardness of the matrix can reach around 600-800 HV0.2 because of high solid solubility of alloy elements. And the property of wear-resisting could approach or even achieve the level of powder metallurgy cemented carbide.