Superlattice supertoughness of TiN/MN (M = V, Nb, Ta, Mo, and W): First-principles study

• First-principles calculations give the structural and elastic properties of TiN/MN superlattices.
• TiN/MN superlattices exhibit in-plane ductility.
• In-plane Cauchy pressure of TiN/MN superlattices is significantly large than that in solid-solutions.
• Superlattice toughening derives from the coupling between macro- and micro-distortions.

In this study, a supertoughness effect is predicted through systematic first-principle calculations on structures and mechanical properties of transition metal nitride superlattices TiN/MN (M = V, Nb, Ta, Mo, and W). The TiN/WN superlattice has an in-plane Cauchy pressure as high as 296 GPa, which is 348% larger than that in Ti0.5W0.5N solid solutions. Supertoughness is also significantly affected by the coupling between macro- and micro-distortions in addition to previously reported valence electron concentration and atomic ordering effects. Present results indicate a route to develop superhard and supertough superlattice coatings.