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T. Glechner, S Lang, R Hahn, M Alfreider, V. Moraes, D. Primetzhofer, J. Ramm, S. Kolozsvári, D. Kiener, H. Riedl:
"Correlation between fracture characteristics and valence electron concentration of sputtered Hf-C-N based thin films";
Surface & Coatings Technology, 399 (2020), 126212; 1 - 8.

Hard protective coating materials based on transition metal nitrides and carbides typically suffer from limited fracture tolerance. To further tune these properties non-metal alloying - substituting C with N - has been proven favorable for magnetron sputtered Hf-C-N based thin films. A theoretically predicted increase in valence electron concentration (from 8.0 to 9.0 e/f.u. from HfC to HfN) through nitrogen alloying lead to an increase in fracture toughness (KIC obtained during in-situ SEM cantilever bending) from 1.89 ± 0.15 to 2.33 ± 0.18 MPa·m1/2 for Hf0.43C0.57 to Hf0.35C0.30N0.35, respectively. The hardness remains close to the super-hard regime with values of 37.8 ± 2.1 to 39.9 ± 2.7 GPa for these specific compositions. Already the addition of small amounts of nitrogen, while sputtering a ceramic HfC target, leads to a drastic increase of nitrogen on the non-metallic sublattice for fcc single phased structured HfC1-xNx films, where x = N/(C + N). The here obtained results also provide experimental proof for the correlation between fracture characteristics and valence electron concentration.

Hf-C-N; Fracture resistance; Non-metal alloying; Valence electron concentration; Thermal stability

http://dx.doi.org/10.1016/j.surfcoat.2020.126212

https://publik.tuwien.ac.at/files/publik_292807.pdf

Project Head Helmut Riedl:
CDL-SEC