Adhesion at cerium doped metal-ceramic α-Fe/WC interface: A first-principles calculation

Abstract

Electronic structure, stability and bonding strength of α-Fe/WC interfaces between Ce-doped and undoped WC cermet coating were investigated by first-principles methodology based on density-functional theory (DFT). Based on the minimum mismatched lattices, the relatively stable interface that forms between WC (100) and bcc α-Fe (100) was employed to predict the atomic structure, bonding, and ideal work of adhesion. There are three possible positions which were defined as OT, MT, HCP, taking into account both C- and W-terminations. The sequence of structural stability tested in this paper was: MT > OT > HCP. After full relaxation, the results show that only the first and second layers of the interface have significant influence on the electronic structure between Fe and WC. The interaction of Ce elements at the interface is achieved by comparing the interface structure and electronic structure of the doped and undoped interfaces. Ce doped interface possesses a shorter interface distance (d0 = 0.09776 nm) and a larger interface energy (Wad = 8.98 J/m2) than undoped interface (Wad = 8.76 J/m2, d0 = 0.10134 nm).Charge density distribution and difference, and density of states were utilized to characterize the electronic properties and determine the interfacial bonding.The results demonstrate that strong covalent bonding existed in the undoped interface, while a mixed covalent/ionic bonding was formed at the Ce-doped interface.