Modelling and experimental studies of VN/TiN interfaces and surfaces

01.02.2008 - 31.01.2009
Research funding project
It is well established in literature that at elevated temperatures TiN/VN layers start to interdiffuse. This process may lead to a degradation of the coating hardness. However, at elevated temperatures, V also diffuses on to the coating surface where it forms in air a Magnéli oxide phase. In particular, the formed V2O5 phase has a low melting point of 685°C and thus leads to self-lubrication at elevated temperatures by a few nanometer thin molten layer on top of the coating. This may significantly increase the lifetime and performance of cutting tools and is economically and ecologically a major driving force for developing optimized design criteria for coatings. The present proposal is focused on the investigation of the atomic processes controlling the functionally of self-lubricating TiN/VN multilayers by combining experiment and ab-initio modelling to achieve an atomistic insight into the physical and chemical properties of VN and TiN interfaces. This will provide in-depth understanding of more complex coating systems, e.g. TiAlN/VN superlattices or V-alloyed TiAlN monolayers. The interplay between surface and interface orientation, internal stresses, and diffusion of V in dependence of the N-content through TiN layers will be analysed in order to optimise the design of nano-sized TiN / VN based multilayer coatings. During the first two years of the project, the main effort was to grow and model TiN / VN layers of single-crystal quality with (100) and (111) orientation relationship by unbalanced magnetron sputtering and ab-initio density-functional theory DFT calculations. After analysis of their chemical composition and comparison to the ab-initio modelling, the main focus of the proposed third year will be laid on (i) interface atomic structure of (100) and (111) oriented TiN/VN multilayers where the experimental results will be compared with the calculated ab-initio data. The chemical composition, defects and strain in the layers will be taken into account, (ii) TiN/VN interdiffusion mechanisms and kinetics will be studied in combination with an ab-initio modelling of diffusion profiles within the layers and across the interfaces, and (iii) additionally, interdiffusion will be also analysed for polycrystalline multilayers and compared to the results of the single crystal films.

People

Project leader

Project personnel

Institute

Grant funds

  • FFG - Österr. Forschungsförderungs- gesellschaft mbH (National) Austrian Research Promotion Agency (FFG)

Research focus

  • Non-metallic Materials: 20%
  • Computational Materials Science: 70%
  • Surfaces and Interfaces: 10%

Keywords

GermanEnglish
Grenzflächen Interfaces
Nano-BeschichtungenNano-Coatings
TiN / VN ÜbergitterTiN / VN Superlattice
OberflächenSurfaces
Diffusiondiffusion

External partner

  • Montanuniversität Leoben - Institut für Metallkunde und metallische Werkstoffe
  • Österr. Akademie der Wissenschaften

Publications