Development of a functional hardness gradient in WC-TiC-Co cemented carbide during gradient sintering

In this study two functionally graded cemented carbide samples with gradients in both composition and grain size have been produced and studied. The two samples are manufactured by local addition of TiC to a pressed WC-Co green body prior to sintering. The two samples differ only by the in-going WC particle size, where one sub-micron and one coarse WC particle size is used. The Ti, Co, and C concentration profiles are analysed using energy−/ and wavelength-dispersive X-ray spectroscopy; Vickers hardness profiles are also measured. Furthermore, the measured experimental concentration profiles are compared with diffusion simulations using the DICTRA software. The concentration and hardness profiles show a similar trend for both samples with decreasing Ti and C concentrations while Co concentration increases with distance from the applied TiC layer. The composition gradient affects the number of stable phases and the WC grain size. Furthermore, there are distinct differences between the samples with different initial WC particle size. The sample with an initially finer WC particle size has a shorter gamma-phase zone and the difference in WC grain size across the gradient is larger as compared to the sample with an initially coarser WC particle size. Finally, abnormal grain growth occurs in both samples but it is suppressed with increasing Ti concentration.