Residual stresses and microstructure in fine grained cemented carbides doped with Cr and Ti

Three fine grained WC-10 vol% Co cemented carbide materials were produced. One with 1 w% Cr addition, one with 0.025 w% Ti addition and one with both additions of 1 w% Cr and 0.025 w% Ti. It was found that doping of both Cr and Ti is advantageous for grain growth inhibition over just Cr- or Ti-doping. The impact of Cr and Ti as grain growth inhibitors on the residual stress state after sintering was investigated. The stress state in the centre of the composite, in WC and Co phase, was quantified by neutron diffraction. The addition of Ti and Cr significantly affects the residual stresses in WC. Notably, the co-doped material exhibits the lowest WC residual stresses despite rather similar WC average grain sizes and binder phase volume fractions compared to the Cr-doped material. This suggests that factors beyond grain size and Co-rich binder volume fraction can play a crucial role in residual stress development. Alterations in binder composition and resulting changes in binder stacking fault energy, thermal expansion coefficient and interface structures as well as changes of the solidification temperature are proposed to also effect the WC residual stresses, and further work is suggested to detail the underlying mechanisms.