Effects of carbon content on microstructure and properties of WC–20Co cemented carbides

• Carbon content of the alloys varies from carbon-deficient to carbon-rich regions.
• We explore WC grain growth mechanism and shape morphology characteristic.
• Effects of carbon content on W solubility in the binder were analyzed by EPMA.
• Bending strength appears maximum in the two-phase region.

Effects of carbon content on microstructure and properties of WC–20Co cemented carbides with carbon content from 4.45% to 5.25% prepared by sinter-HIP were analyzed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), Rockwell hardness analysis, cobalt magnetic performance analysis, bending strength analysis and so on. The results show that carbon content plays a significant role in the phase composition and microstructure, WC grain size and shape, W solubility of the binder, and mechanical properties of cemented carbides. In the field of research, with increasing carbon content, the WC mean grain size increases and morphology characteristic of WC grains tends to show truncated trigonal prim shape. And carbon content also influences W solubility, so that in carbon-rich cemented carbides the binder dissolves about 4 mass% tungsten and in carbon-deficient cemented carbides up to 20 mass%. The density and Rockwell hardness of alloys decrease with increasing carbon content. On the contrary, the cobalt magnetic performance of alloys increases and the extent of variation gets smaller and smaller. The bending strength of alloys increases then substantially decreases with increasing carbon content and appears maximum in the two-phase region.