Synthesis and characterization of ceramic high entropy carbide thin films from the Cr-Hf-Mo-Ta-W refractory metal system

• 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 12 sccm, at ambient and elevated temperatures (700 degrees C), respectively, hindering/promoting the adatom diffusion. Structural and microstructural investigations reveal the formation of the bcc metallic phase ( a = 3.188 - 3.209 & Aring;) 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 & Aring;). The crystalline films reveal columnar morphology, while the amorphous ones are very dense. We report promising mechanical properties, with hardness up to 25 +/- 1 GPa. The indentation moduli reach up to 319 +/- 6 GPa 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.

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

High entropy carbide; High entropy alloy; Multicomponent ceramics; Multicomponent material; Thin film; Magnetron sputtering

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