Synthesis and Characterization of Ceramic High Entropy Carbide Thin Films from the Cr-Hf-Mo-Ta-W Refractory Metal System

Stasiak, T. and Debnárová, S. and Lin, S. and Koutná, N. and Czigány, Zs. and Balázsi, K. and Buršíková, V. and Vašina, P. and Souček, P. (2024) Synthesis and Characterization of Ceramic High Entropy Carbide Thin Films from the Cr-Hf-Mo-Ta-W Refractory Metal System. SURFACE AND COATINGS TECHNOLOGY : AN INTERNATIONAL JOURNAL DEVOTED TO THE SCIENCE AND APPLICATION OF ADVANCED SURFACE TREATMENTS FOR IMPROVEMENT OF MATERIAL PROPERTIES. No.-130839. ISSN 0257-8972 (print); 1879-3347 (online) (In Press)

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Abstract

We use reactive DC magnetron sputtering to showcase synthesis strategies for multicomponent carbides with the NaCl-type fcc structure and illustrate how deposition conditions allow controlling the formation of metallic and ceramic single phases in the Cr-Hf-Mo-Ta-W system. The synthesis is performed in argon flow and different acetylene flows from 0 to 12sccm, at ambient and elevated temperatures (700 °C), respectively, hindering/promoting the adatom diffusion. Structural and microstructural investigations reveal the formation of the bcc metallic phase (a =3.188–3.209Å) in films deposited without acetylene flow, also supported by ab initio density function theory (DFT) analysis of lattice parameters as a function of the C content. Experimentally, a bcc-to-fcc phase transition is observed through the formation of an amorphous coating. Contrarily, samples deposited in higher acetylene flow show an fcc multielement carbide phase (a =4.33–4.49 Å). The crystalline films reveal columnar morphology, while the amorphous ones are very dense. We report promising mechanical properties, with hardness up to 25± 1GPa. The indentation moduli reach up to 319± 6GPa and show trends consistent with DFT predictions. Our study paves the path towards the preparation of Cr-Hf-Mo-Ta-W multicomponent carbides by magnetron sputtering, showing promising microstructure as well as mechanical properties.

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