Synthesis and Characterization of High Entropy Ceramic Coatings from Cr-Hf-Mo-Ta-W Refractory Metal System
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| Year of publication | 2024 |
| Type | Conference abstract |
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| Description | In this contribution‚ we are examining the formation of single-phase high entropy nitrides and high entropy carbides NaCl-type fcc structure from the Cr-Hf-Mo-Ta-W system. Magnetron sputtering was used for all depositions. An ambient temperature was used for the first deposition set‚ while an elevated temperature of 700°C was used for the second to observe the influence of the temperature on the crystallization. Argon/nitrogen gas admixture was used in nitrides‚ while argon/acetylene was used in carbides. This led to the first difference in reaching different nitrogen/carbon content in the coatings. While sputtering in nitrogen is a typical representative of reactive magnetron sputtering and nitrogen content never exceeded 50 at.%‚ sputtering in acetylene belongs to the hybrid PVD-PECVD deposition processes‚ also known as unsaturated reactive sputtering‚ and much higher carbon content in the coatings is reached. The deposition rate did not significantly decrease for all reactive gas flows. The structure and mechanical properties of the coatings were heavily influenced by the reactive gas flow for both systems. In films deposited without acetylene flow‚ a bcc metallic phase was observed. Increasing reactive gas flow first showed an amorphous structure and then an fcc multielement carbide structure. Therefore‚ the ability of the system to form either metallic or ceramic nitride and carbide single phases was confirmed. Amorphous coatings exhibited a dense microstructure‚ while crystalline films were more columnar with multilayered structure at the nanoscale given by the deposition process geometry. The mechanical properties of the deposited films were good‚ exhibiting a hardness of up to 25 GPa‚ while the majority of the coatings were around 20 GPa. There was no great difference between the hardness of the corresponding nitrides and carbides. |
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