Microstructural study of hot-deformed cemented carbides

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Abstract
The microstructure of cemented transition-metal carbides has been characterized in both the as-sintered condition and after uniaxial plastic compression at temperatures of 1100 and 1400°C. Both the dislocation structure and the dislocation density were non-uniform within the same sample for all compositions and conditions investigated. These findings are attributed to the large but localized internal stresses developed during liquid-phase sintering and to localized differential thermal contraction on cooling from liquid-phase sintering. Later evidence suggested the presence of a thin film of Go at two-grain interfaces, although it could not be detected by X-ray microchemical analysis because of limited spatial resolution. The likely mechanism of high-temperature deformation is grain-boundary sliding. WC grain shapes were significantly less sharp and angular for samples compressed at 1400°C then for those compressed at 1100°C. It is suggested that this rounding of WC grains occurred as a consequence of a solution and reprecipitation process, which also may have resulted in a larger effective load-supporting cross-sectional area between adjacent WC networks, leading to the previously reported levelling (rather than sharp decrease) of compressive yield stress with respect to temperature as the temperature exceeds the binder liquidus.