Binder jet additive manufacturing of tungsten carbide-cobalt tooling material

Abstract

WC–Co based materials are attractive for tooling applications due to a combination of excellent hardness, high compressive strength, and wear resistance. Traditional manufacturing methods like powder metallurgy and extrusion can produce WC–Co components with low porosity but are limited in geometric complexity. Additive manufacturing, especially binder jet sdditive manufacturing has emerged as a promising alternative for fabricating complex geometries more efficiently. However, challenges remained, particularly with the formation of undesirable η phases (such as W₃Co₃C and W₆Co₆C) during the sintering of WC–Co alloys, which degrade mechanical properties like hardness and toughness. To examine the wholistic effect of processing steps on microstructure and phase evolution, the current study investigated the fabrication of WC-10 wt.%Co via binder jet additive manufacturing with successive densification and post-processing steps, including sintering, hot isostatic pressing, as well as pack carburising. The sintered samples experienced partial decomposition of WC + Co into η phases. Although successive hot isostatic pressing improved densification, it continued resulting in material predominantly consisting of η phases. Whereas the pack carburising helped revert η phases into WC + Co microstructure in both as sintered and hot isostatically pressed samples. The hardness of these samples was comparable to the conventionally fabricated WC + Co material.