Computer Aided Design of Microstructure for Highly Functional Ceramics Coating Films

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Ceramics coating film is one of the most promising approaches for highly functional coating films. For example, the ceramics superlattice shows remarkable enhancement in indentation hardness and thermal stability with a specified laminating period, it is expected to be used as a wear-resistant corting films on the surfaces subjected to heavy duty friction such as cutting tools and slide ways. However, the mechanism of hardness enhancement has not been understood well due to the difficulties in highly reliable measurement of mechanical properties and observation of microstructure of the film.In this research, to clarify the correlation between the microstructure and mechanical properties of ceramics coating films and to establish the guidelines for design of highly functional ceramics coating films, the useful analytical methods of extended molecular dynamics (MD) computer simulations, which include MD/FEM hybrid model and renormalization groupe MD, are proposed for nano to micro scale … More analysis of material behavior.The results of simulations suggest that optimum laminating period, which was reported so far, for hardness enhancement does not appears at least in case of TiN/ZrN superlattice film. On the other hand, experimental results of microindentation on arc ion-plated TiN/ZrN superlattice films with the period of 12 nm shows larger hardness enhancement than that with 2.5 nm. As these films have polycrystalline structure, atomic misfits and grain boundaries are inevitably included in the film. A larger number of defects included in the film with smaller period may deteriorate its mecanical properties. Further simulations on the model including defects are now being continued. To clarify the mechanism of hardness enhancement, more efforts for comparative studies are required between MD simulation in micro scale and practical testing in macro scale. However, MD simulation can be an useful tool to help clear understanding in principle the correlation between microstructure and mechanical properties of ceramics superlattice. Less