Influence of post heat treatment on microstructure and fracture strength of cemented carbides manufactured using laser-based additive manufacturing

Abstract

Laser-based additive manufacturing of cemented carbides (WC-Co) remains challenging due to crack forming and residual porosity. Reduction of temperature gradients by high preheating temperatures and successive thermal treatments are starting points for improving the quality of additively manufactured components. Thermal post-treatment is beneficial for the final densification and homogenization of the microstructure. In this study, hot isostatic pressing (HIP) and sinter-HIP are used for thermal post-treatment of additively manufactured parts of WC-12Co. Both methods use elevated temperatures and pressures for densification. Densification during the sinter-HIP process is achieved by liquid phase sintering, while in the HIP process, compaction is expected by plastic deformation of the material. The effect of these both methods for post-treatment on microstructure and fracture strength is investigated in this study. Subsequently, tungsten carbide grain size, as well as the composition of the binder phase, are related to these results.