On the influence of strong- and weak-nitride forming elements on the preparation of refractory metal based high entropy nitrides by magnetron sputtering
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| Year of publication | 2024 |
| Type | Conference abstract |
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| Description | Cr-Hf-Mo-Ta-W-N is chosen as a system of elements composed solely of strong nitride-forming elements. Moreover, all of them, except for tungsten, have similar atomic radii. This should favour an easy formation of a high entropy alloy in case of no nitrogen in the coatings or of a high entropy ceramic if sufficient nitrogen content is supplied during the deposition process. Indeed, a bcc cell is formed if the metallic targets are sputtered without nitrogen addition. As nitrogen was added, amorphization was observed in the case of the low energy deposition, while adding even more nitrogen into the deposition resulted in a single fcc phase, which was formed even for a high number of nitrogen vacancies in the nitrogen sublattice. The deposition conditions did not strongly affect the mechanical properties, and the hardness was ~ 20 GPa. Cr-Mn-Mo-Si-Y-N system is chosen as a comparison as manganese and yttrium do not readily form nitrides. Moreover, yttrium has a significantly higher atomic radius, and silicon has a significantly lower atomic radius than the other elements. In this case, the formation of a high entropy alloy and ceramic should be considerably more difficult than in the previous system. Indeed, coatings deposited at low temperature were amorphous, regardless of the nitrogen content. Post-deposition annealing at 800°C led to a start of crystallization of several phases, probably chromium nitride. Deposition at high energies resulted in nearly amorphous coatings with similar annealing results. The hardness of this system was considerably lower than in the previous system and was in the range of 8-16 GPa. |
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