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

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 similar to 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 similar to 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.

Automated summary

Aberration-corrected scanning transmission electron microscopy was used to study the atomic-level segregation mechanism in V-doped WC-Co composites. It was found that the segregation behavior largely depends on the orientation of low-index planes, particularly the basal and prismatic facets in WC-Co. V solute atoms show weak segregation at the WC prismatic plane-terminated interfaces, mainly occurring within a monolayer. In contrast, segregation at the basal facets of WC grains distributes within a bilayer with a higher concentration.