Facet-dependent interfacial segregation behavior of V-doped WC-Co cemented carbides

Abstract

Understanding the interfacial segregation behavior in V-doped WC-Co hard metals is necessary to demystify the effect of dopant on microstructural evolution and mechanical properties. Herein, aberration-corrected scanning transmission electron microscopy was utilized to investigate the atomic level segregation mechanism at WC-Co phase boundaries and WC grain boundaries in V-doped WC-Co composites systematically. A key finding is that the segregation behavior largely depends on the orientation of low-index planes, particularly the basal and prismatic facets that prevail in WC-Co. V solute atoms show a relatively weak segregation at the WC prismatic plane-terminated interfaces, occurring largely within a monolayer with ∼10 at% V at the outermost surface. In contrast, segregation at the basal facets of WC grains distributes within a bilayer with a higher concentration of ∼25 at%. Additionally, this study shows that the facet-dependent interfacial segregation behavior is universal for both phase boundaries and grain boundaries, which often have at least one basal or prismatic WC facet. Our study presents a general solute segregation mechanism at an atomic level and demonstrates that the terminal planes of interfaces determine the atomic structure and segregation profile, while the interfacial orientation has little influence.