Atomic-scale insights into the enhancement of Fe/TiN interfaces by rare-earth elements

Titanium nitride (TiN) coatings are commonly applied to steel-based components in aero-engines to enhance interfacial performance, yet the relatively weak adhesion between TiN and the steel substrate severely limits component service life. Rare earth doping has emerged as an effective strategy for interface improvement. In this study, first-principles calculations were employed to systematically evaluate the effect of all stable rare-earth elements on the interfacial strength of the Fe/TiN interface at the atomic scale. Among the three constructed interfacial models, the N-terminated configuration was found to be the most stable. Calculations of interfacial adhesion indicate a precise strengthening sequence of rare earth elements on the Fe/TiN interface. Furthermore, doping at Fe sites was generally more advantageous than at Ti sites. Among all rare earth elements, Lu substitution at Fe sites shows the highest thermodynamic stability and the most substantial increase in orbital hybridization. These findings offer atomic-level design guidance for tuning Fe/TiN interfaces through rare-earth modification and provide theoretical insights for developing metal–ceramic protective coatings with superior interfacial performance.