Adhesion, stability, and bonding at metal/metal-carbide interfaces: Al/WC

We examine the relative stability and adhesion of the polar Al(1 1 1)/WC(0 0 0 1) interface using density functional theory. Relaxed atomic geometries and the ideal work of adhesion were calculated for six different interfacial structures, taking into account both W- and C-terminations of the carbide. The interfacial electronic structure was analyzed to determine the nature of metal/carbide bonding. Based on the surface and interfacial free energies, we find that both the clean WC(0 0 0 1) surface and the optimal interface geometry are W-terminated. Although both terminations yield substantial adhesion energies in the range 4-6 J/m², bonding at the optimal C-terminated structure is nearly 2 J/m² stronger, consistent with an argument based on surface reactivity. In addition, we examine the effects of Li and Mg alloying elements at the interface, and find that they result in a strain-induced reduction of metal-ceramic adhesion.