The use of negative bias potential for structural engineering of vacuum-arc nitride coatings based on high-entropy alloys

Abstract

The effect of negative bias potential (U b = -40, -110, and -200 V) during the deposition of multi-element coat-ings on their composition, structure and mechanical properties was studied. It was established that during the transi-tion from a multi-element alloy to a nitride, a single-phase state possible to form on its basis (based on the fcc metal lattice, structural type NaCl). In this case, the composition (FeCoNiCuAlCrV)N of coatings with increasing U b is depleted by the element with the lowest enthalpy of formation of nitride (Cu). In (AlCrTiNbSi)N and (AlCrTiZrNbV)N coatings, the content of low-mass elements (Si and Al) decreases with increasing U b . In (TiZrHfVNb)N coatings of strong nitride-forming elements with increasing U b to 200 V, the composition practically does not change. The structure of such coatings is characterized by the presence of a texture with the [111] axis. The presence of weak nitride-forming elements in (FeCoNiCuAlCrV)N coatings leads to the formation of texture [110] for large U b = 110…200 V. In such coatings, the hardness does not exceed 35 GPa. It is shown that to achieve high hardness at high U b it is necessary to increase the content in the high-entropy alloy of elements with high nitride-forming ability. In this case, in (TiZrHfVNb)N coatings (made of strong nitride-forming elements with a large mass) at U b = 200 V, the hardness exceeds 45 GPa.