Study on the martensitic transformation mechanism of binder phase in WC-10Co nanocrystalline cemented carbides

This study comprehensively investigates the martensitic transformation mechanism of the binder phase in nanocrystalline cemented carbides, focusing on the nucleation and growth of ε-Co mediated by orientation relationships among WC, ε-Co, and α-Co. Notably, when WC and α-Co share a common crystallographic orientation, such as (10-10) WC /(110) Co interface, they form a special interface characterized by continuously aligned lattice planes, which critically facilitates ε-Co nucleation. Such interfaces maximize matching efficiency, minimize interfacial energy, and thus provide favorable nucleation sites for ε-Co. Residual stress induces stacking faults along the (111) planes of α-Co at (10-10) WC /(110) Co interface. Progressive accumulation of stacking faults under cyclic stress conditions enables the complete FCC-to-HCP phase transition, transforming α-Co into ε-Co. The HCP-structured binder phase, with its limited slip systems and localized high-strain zones, exhibits exceptional resistance to deformation, thereby substantially improving mechanical performance. Through cryogenic coupled with pulsed electric field treatment, the ε-Co content in the binder phase increased dramatically from 1.89% to 16.55%, accompanied by a remarkable hardness enhancement from 1879 HV 30 to 2084 HV 30 .