Liquid Phase Migration and Shape Distortion of WC-Co Cemented Carbides—The Effect of Carbon Content Gradient in Sintered Compacts—

The effect of carbon content gradient in WC-Co cemented carbides on the liquid phase migration (LPM) and the shape distortion during sintering was investigated. Ready to press powders for WC-10 mass%Co cemented carbides with high and low carbon contents were prepared. Then, the bi-layered green compacts of round bars and square plates with high and low carbon contents were fabricated and sintered under various conditions. LPM occurred from the high-carbon side to the low-carbon side, which caused the diameter change in the round bars and the warping in the square plates. The amount of LPM and the shape distortion decreased with increasing sintering temperature and sintering time and they increased with decreasing cooling rate from 1673 K. We concluded that the LPM with the carbon content gradient is caused by the generation of the migration pressure in the solid-liquid Co coexistence zone (ΠSL) on the lower carbon side during cooling after sintering. The mechanism of LPM is the same as that from the higher temperature side to the lower temperature side, which we clarified in the previous studies.