Tuning structure and mechanical properties of Ta-C coatings by N-alloying and vacancy population

T Glechner; P H Mayrhofer; D Holec; S Fritze; E Lewin; V Paneta; D Primetzhofer; S Kolozsvári; H Riedl

doi:10.1038/s41598-018-35870-x

Tuning structure and mechanical properties of Ta-C coatings by N-alloying and vacancy population

Sci Rep. 2018 Dec 5;8(1):17669. doi: 10.1038/s41598-018-35870-x.

Authors

T Glechner¹, P H Mayrhofer², D Holec³, S Fritze⁴, E Lewin⁴, V Paneta⁵, D Primetzhofer⁵, S Kolozsvári⁶, H Riedl²

Affiliations

¹ Institute of Materials Science and Technology, TU Wien, A-1060, Wien, Austria. thomas.glechner@tuwien.ac.at.
² Institute of Materials Science and Technology, TU Wien, A-1060, Wien, Austria.
³ Department of Materials Science, Montanuniversität Leoben, A-8700, Leoben, Austria.
⁴ Department of Chemistry - Ångström Laboratory, Uppsala University, SE-75120, Uppsala, Sweden.
⁵ Department of Physics and Astronomy, Uppsala University, SE-75120, Uppsala, Sweden.
⁶ Plansee Composite Materials GmbH, D-86983, Lechbruck am See, Germany.

Abstract

Tailoring mechanical properties of transition metal carbides by substituting carbon with nitrogen atoms is a highly interesting approach, as thereby the bonding state changes towards a more metallic like character and thus ductility can be increased. Based on ab initio calculations we could prove experimentally, that up to a nitrogen content of about 68% on the non-metallic sublattice, Ta-C-N crystals prevail a face centered cubic structure for sputter deposited thin films. The cubic structure is partly stabilized by non-metallic as well as Ta vacancies - the latter are decisive for nitrogen rich compositions. With increasing nitrogen content, the originally super-hard fcc-TaC_0.71 thin films soften from 40 GPa to 26 GPa for TaC_0.33N_0.67, accompanied by a decrease of the indentation modulus. With increasing nitrogen on the non-metallic sublattice (hence, decreasing C) the damage tolerance of Ta-C based coatings increases, when characterized after the Pugh and Pettifor criteria. Consequently, varying the non-metallic sublattice population allows for an effective tuning and designing of intrinsic coating properties.