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Toughness Enhancement in TiN/WN Superlattice Thin Films

57 Pages Posted: 28 Mar 2019 First Look: Accepted

See all articles by Julian Buchinger

Julian Buchinger

Vienna University of Technology - Institute of Materials Science and Technology

Nikola Koutná

Vienna University of Technology - Institute of Materials Science and Technology

Zhuo Chen

University of Vienna - Erich Schmid Institute of Materials Science

Zaoli Zhang

University of Vienna - Erich Schmid Institute of Materials Science

Paul Heinz Mayrhofer

Vienna University of Technology - Institute of Materials Science and Technology

David Holec

Montanuniversität Leoben - Department of Materials Science

Matthias Bartosik

Vienna University of Technology - Institute of Materials Science and Technology

Abstract

Transition metal nitride thin films traditionally possess a low intrinsic fracture toughness. Motivated by the recently discovered fracture toughness enhancing superlattice (SL) effect, as well as the remarkably high potential for toughness predicted by theoretical studies for TiN/WN superlattices, we synthesise a series of these materials by DC reactive magnetron sputtering. The SL coatings demonstrate a vacancy-stabilised cubic configuration throughout, as well as a marginal lattice mismatch between the TiN and WN layers. All investigated mechanical properties produced a distinct dependence on the bilayer period, featuring a hardness peak of 36.7 ± 0.2 GPa and a minimum of the indentation modulus of 387 ± 2 GPa. The toughness-related quantities of the SLs in particular show a significant enhancement compared to monolithic TiN and WN, including a tripling of the fracture energy. The fracture toughness is raised from 2.8 ± 0.1 (TiN) and 3.1 ± 0.1 (WN) to 4.6 ± 0.2 MPa√m by the SL arrangement. We relate this maximisation to the vastly disparate elastic moduli and compositional fluctuations. To complement our experimental data, we present Density Functional Theory-based models to disentangle the conspicuous trends observed for TiN/WN superlattices.

Keywords: Superlattice, Fracture Toughness, Thin Film, Sputtering, DFT

Suggested Citation

Buchinger, Julian and Koutná, Nikola and Chen, Zhuo and Zhang, Zaoli and Mayrhofer, Paul Heinz and Holec, David and Bartosik, Matthias, Toughness Enhancement in TiN/WN Superlattice Thin Films (March 23, 2019). Available at SSRN: https://ssrn.com/abstract=3358867 or http://dx.doi.org/10.2139/ssrn.3358867

Julian Buchinger (Contact Author)

Vienna University of Technology - Institute of Materials Science and Technology ( email )

Karlsplatz 13
Vienna
Austria

Nikola Koutná

Vienna University of Technology - Institute of Materials Science and Technology

Karlsplatz 13
Vienna
Austria

Zhuo Chen

University of Vienna - Erich Schmid Institute of Materials Science

Jahnstraße 12
Leoben
Austria

Zaoli Zhang

University of Vienna - Erich Schmid Institute of Materials Science

Jahnstraße 12
Leoben
Austria

Paul Heinz Mayrhofer

Vienna University of Technology - Institute of Materials Science and Technology

Karlsplatz 13
Vienna
Austria

David Holec

Montanuniversität Leoben - Department of Materials Science

Leoben
Austria

Matthias Bartosik

Vienna University of Technology - Institute of Materials Science and Technology

Karlsplatz 13
Vienna
Austria

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