Tuning Co distribution in powder feedstock for laser powder bed fusion of crack-free WC-Co cemented carbides

Abstract

This work presents specific one-step additive manufacturing of crack-free WC-12Co cemented carbides by the laser powder bed fusion (LPBF) technology using the mixed ultra-coarse WC and agglomerated Co powder as feedstock. The critical role of the agglomerated Co in elimination of cracks, pores and carbon-deficient phases during the LPBF fabrication and subsequent heat-treatment process was disclosed. Moreover, the agglomerated Co led to the formation of lath-shaped WC grains containing numerous Co-rich particles with sizes ranging from a few nanometers to approximately 300 nm. These in-grain Co-rich particles could accommodate plastic deformation and hinder dislocation motion within lath-shaped WC grains, but did not cause local stress concentration, thereby contributing to enhance both the toughness and strength of the resulting cemented carbides. The proposed novel strategy of tuning the distribution state of metallic phase within the feedstock holds significant potential for applications in the direct additive manufacturing of high-performance cermet materials.