Interfacial fracture toughness of transition metal nitrides

Interfacial fracture toughness is one of the key parameters in assessing and controlling the quality and performance of multiple-layer hard protective coatings. This paper reports on a study of interfacial fracture toughness of transition metal nitrides using ab initio density functional theory (DFT) calculations. Five transition metal nitrides, TiN. CrN, ZrN, VN and HfN, were selected for this study. The interfaces between these nitrides were constructed, and the ideal work of adhesion W-ad and Young's modulus E along (100) and (110) orientations for these nitrides were calculated. On the basis of calculated W-ad and E, the interfacial fracture toughness K-IC was evaluated. The trends of interfacial fracture toughness were analyzed for two specific orientations (100) and (110). It is proposed that interfacial fracture toughness may be used as guidance for the development of multi-layer coatings for either wear or erosion protection. (C) 2008 Elsevier B.V. All rights reserved.