Interface-controlled defect engineering in TiN/TaN superlattices for enhanced hardness and fracture toughness

Materials & Design, vol. 270, pp. 116972

Abstract

TiN/TaN superlattice coatings were designed to investigate how atomic-scale interface chemistry and defect-stabilized TaN layers govern hardness and fracture toughness. Guided by first-principles predictions identifying TaN-based layers as more damage tolerant than TiN, coherent superlattices with a bilayer period of ~6 nm were synthesized by reactive magnetron sputtering and interfacially doped with C, B, or Si. Structural and chemical analyses reveal coherent fcc architectures with well-defined interfaces. Si segregates preferentially to the interfaces while incorporating into both TiN and TaN, whereas C and B predominantly diffuse into the TaN layers, modifying coherency strain, bonding, and defect populations. Consequently, hardness increases from ~34 GPa for the undoped superlattice to ~41 GPa for the Si-doped architecture, whereas fracture toughness increases from ~2.8 to ~4.0 MPa√m for the B-doped superlattice. First-principles calculations show that vacancy-stabilized TaxNy enhances elastic compliance and elastic contrast rather than intrinsic toughness, while the additional toughening induced by B indicates localized defect-assisted energy dissipation at chemically engineered interfaces. Thus, Si maximizes interface strengthening, whereas B provides the most favourable hardness-toughness balance while preserving high hardness (~38 GPa). These findings establish interface chemistry as an additional design parameter for tailoring the mechanical performance of ceramic nitride superlattices.

Authors 9

1. Zecui Gao

   Guangdong University of Technology · TU Wien

   Affiliation as printed

   Institute of Materials Science and Technology, Technische Universität Wien, Getreidemarkt 9, 1060 Vienna, Austria

   Plansee (Shanghai) High Performance Material Ltd., China

   School of Electromechanical Engineering, Guangdong University of Technology, Guangdong, China

2. Qimin Wang

   Guangdong University of Technology

   Affiliation as printed

   School of Electromechanical Engineering, Guangdong University of Technology, Guangdong, China

3. Julian Buchinger

   TU Wien

   Affiliation as printed

   Institute of Materials Science and Technology, Technische Universität Wien, Getreidemarkt 9, 1060 Vienna, Austria

4. Nikola Koutná

   TU Wien

   Affiliation as printed

   Institute of Materials Science and Technology, Technische Universität Wien, Getreidemarkt 9, 1060 Vienna, Austria

5. Marcus Hans Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

6. Zaoli Zhang

   Austrian Academy of Sciences · Erich Schmid Institute of Materials Science

   Affiliation as printed

   Erich Schmidt Institute of Materials Science, Austrian Academy of Sciences, Jahnstr. 12, 8700 Leoben, Austria

7. Jochen M. Schneider Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

8. Daniel Primetzhofer

   Uppsala University

   Affiliation as printed

   Materials Physics, Uppsala University, Regementsvägen 10, 752 37 Uppsala, Sweden

9. P.H. Mayrhofer corresponding

   TU Wien

   Affiliation as printed

   Institute of Materials Science and Technology, Technische Universität Wien, Getreidemarkt 9, 1060 Vienna, Austria