Hard wear-resistant coatings with anisotropic thermal conductivity for high thermal load applications

Bottger, P. H. M.Laboratory of Nanoscale Materials Science, EMPA, Dübendorf, Switzerland (author)

High thermal load applications such as high speed dry cutting lead to high temperatures in the coated tool substrate that can soften the tool and high temperature gradients that can put stress on the coating/tool interface. In this work, theoretical considerations are presented for multilayer and graded protective coatings that can induce a significant anisotropy in their thermal conductivity. Solution of the heat equation shows that anisotropy of thermal conductivity has the potential to reduce temperatures and temperature gradients arising due to brief, localized heat at the coating surface ("hot-spots"). Experimental realization of high anisotropy is demonstrated in TiN/AlCrN multilayer coatings with variable layer thickness. In the coating with 50 nm bilayer periodicity, the highest anisotropy was obtained with a value of kappa(parallel to)/kappa(perpendicular to) = 3.0 +/- 0.9. Time-domain thermoreflectance is used to measure in-plane and cross-plane thermal conductivity of fabricated coatings. The observed high values of anisotropy of thermal conductivity are compared with theoretical predictions and its realisation is discussed with regard to the coating microstructure.

Braginsky, L.Laboratory of Crystallography, ETH Zürich, Zürich, Switzerland (author)
Shklover, V.Laboratory of Crystallography, ETH Zürich, Zürich, Switzerland (author)
Lewin, ErikLaboratory of Nanoscale Materials Science, EMPA, Dübendorf, Switzerland(Swepub:uu)leeri169 (author)
Patscheider, J.Laboratory of Nanoscale Materials Science, EMPA, Dübendorf, Switzerland (author)
Cahill, D. G.Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois, USA (author)
Sobiech, M.Oerlikon Balzers Coating AG, Balzers, Principality of Liechtenstein (author)
Laboratory of Nanoscale Materials Science, EMPA, Dübendorf, SwitzerlandLaboratory of Crystallography, ETH Zürich, Zürich, Switzerland (creator_code:org_t)

In:Journal of Applied Physics: AIP Publishing116:1, s. 013507-0021-89791089-7550

By the author/editor: Bottger, P. H. M ...; Braginsky, L.; Shklover, V.; Lewin, Erik; Patscheider, J.; Cahill, D. G.; show more...; Sobiech, M.; show less...

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