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T. Glechner, S Lang, V. Moraes, D. Primetzhofer, J. Ramm, S. Kolozsvári, H. Riedl:
"Synthesis and thermomechanical properties of Hf-C-N coatings";
Talk: 47th International Conference on Metallurgical Coatings and Thin Films, ICMCTF, San Diego (USA); 2021-04-26 - 2021-04-30.

Hafnium and Hf-based compounds such as HfC, HfB2, or HfO2 are highly interesting materials based on their outstanding thermal properties indicated through melting points (TM) being individually nearly the highest within their material families. This makes these Hf based systems extremely interesting for ultra-high-temperature applications such as protective coatings applied on high-performance components. Except the metallic Hf itself, all other Hf based compounds lack particularly on their low fracture tolerance. Nevertheless, for transition metal (TM) carbides serval literature reports suggest that substitutional alloying of the non-metallic sublattice by exchanging C with N atoms enhance various properties, e.g. TM, Young´s modulus, as well as fracture tolerance [1,2]. Furthermore, the enhancement of the ductile character was in detail proven for the Ta-C-N system [2]. Along with these facts and a suggested increase in oxidation resistance with respect to the binary carbides, TM-carbonitrides can be a promising alternative for protective thin film materials.
Therefore, within this study the impact of the composition on the non-metallic sublattice for the Hf-C-N system has been explored systematically with respect to thermo mechanical properties, ranging from phase stability, fracture parameters, as well as oxidation resistance. We therefore applied a combined theoretical and experimental approach using density functional theory based calculations and PVD based synthesis techniques. Hf-C thin films were deposited via non-reactive magnetron sputtering, while ternary Hf-C-N coatings have been deposited in mixed N2/Ar atmospheres. Furthermore, to also compare the phase formation route with respect to chemical composition and grain boundary interior a Hf-C-N compound target was sputtered non-reactively. The chemical composition and morphology of all coatings deposited has been studied via ERDA and SEM/TEM, respectively. Mechanical characteristics such as hardness, Young´s modulus, or fracture toughness have been accessed by different micromechanical testing techniques. The phase evolution in inert and oxidizing atmospheres was analysed by DSC/TG.

Project Head Helmut Riedl:
CDL-SEC