Influence of the Lattice Parameter on Physical Properties of High-Entropy Coatings

Abstract.

Relevance. The appearance of high-entropy alloys with increased values of hardness and thermal stability led to the study of their properties in coatings. High-entropy metal coatings are described by high hardness values in the range from 7 to 19 GPa.

Purpose. Study of the general regularities of the influence of various parameters on physical properties of high-entropy metal coatings.

Methods. To obtain high-entropy alloys based on solid solutions with a body-centred cubic and face-centred cubic lattice, the metals Al, Ti, Cr, V, Nb, Mo, Zr, Hf, Ta, Mn, Fe, Co, Ni of groups 3-8 of the periodic table were used. Cast alloys were obtained by vacuum arc melting. Coatings – by methods of vacuum arc sputtering and ion sputtering in the plasma of a compressed vacuum arc discharge. The thickness of the coatings varied from 4 to 6 microns. The coatings were studied using X-ray phase analysis and instrumental indentation.

Results. The study of the initial materials and metal coatings made of them allowed determining the phase composition, hardness, modulus of elasticity and normalised hardness. In the studied alloys, the phase composition of the cast high-entropy alloy and coatings did not change. However, in most cases, the lattice parameter in the coatings was less than in the cast state, and the modulus of elasticity of the coatings was slightly higher than in the cast material. Due to the substantial reduction of the structure in the coatings, their hardness is more than twice the hardness of the cast material.

Conclusions. Based on the results obtained, the influence of the lattice parameter on the hardness and modulus of elasticity in high-entropy coatings based on body-centred cubic and face-centred cubic lattices is revealed. A decrease in the lattice parameter of a high-entropy coating by 10% causes a twofold increase in hardness, which is also typical for cast high-entropy alloys

Keywords: metal coatings, phase composition, BCC lattice, FCC lattice, modulus of elasticity and normalised hardness

https://doi.org/10.24144/2415-8038.2021.49.61-65