Numerical approach to the study of the stressed (001)NiO/(111)Ni coatings

This work is devoted to the study of the thermomechanical behaviour of the oxide films formed during the high-temperature oxidation of loaded (1 1 1)N i single-crystalline nickel samples, The NiO/Ni system is submitted to a hi gh-temperature creep in the oxygen atmosphere. First experiments performed with this system have shown, several deformation modes (diffusional creep, gliding at the interfaces, etc.) in the oxide film and the appearance of pe riodic cracks perpendicular to the loading direction. The inter-crack dista nce varies strongly with the load amplitude. In order to clarify these phen omena, we developed two numerical models. Both models take into account the oxide growth phenomenon and consequently the epitaxial strain due to the l attice misfit between the film and the substrate. A simplified 1D model of the oxide layer evolution and a complete 3D finite element model. The resul ts obtained for this model (residual stress and strain and their distributi on in the film along the direction perpendicular to the substrate) are used in the 3D model as initial data for the simulation of successive cracks th at appear during external loading. For that simulation, we associate remesh ing techniques and field mapping. Using the proposed approach, we study, na mely, the dissymmetrical coating growth. We analyse also the effect of the crack generation during the loading on the mechanical fields along the meta l/oxide interface, (C) 2000 Elsevier Science B.V. All rights reserved.