STRUCTURAL AND PHASE STATES OF THE Al-Fe-Co-Cr-Ni HEA COATING FORMED ON THE 5083 ALLOY

10.25712/ASTU.1811-1416.2023.01.005

Abstract

Using the technology of cold metal transfer (wire-arc additive manufacturing (WAAM) combined with welding surfacing (CMT)) on a 5083 alloy substrate, a coating with a high-entropy alloy (HEA) Al-Fe-Cr-Co-Ni of non-equiatomic composition is formed. Using the methods of modern physical materials science, the analysis of the structure, phase and elemental composition, defective substructure of the "coating-substrate" system was carried out. It is shown that the elemental and phase composition, the defective substructure of the coating depend on the distance to the contact zone between the coating and the substrate. In a layer up to 200 µm thick adjoining the contact zone, the presence of inclusions of the second phase at the grain boundaries of HEA enriched with chromium and iron atoms was revealed. Microdiffraction analysis established that these are inclusions of Al₈Cr₅. In the mixing zone of the coating and substrate, the formation of a nanocrystalline Al₂O₃ and MgAlO phase 10-20 nm in size and a subgrain structure (subgrain size 140-170 nm) were revealed. Structure of the first type is characterized by the heterogeneous distribution of HEA chemical elements, the regions of lamellar from enriched by Cr atoms and spherical from enriched by Ni, Fe, Co atoms were revealed. Nanosized particles (NiCo)₃, Al₄ and Al₁₃Fe₄ are located along the boundaries of the subgrains of the structure. An assumption is made about the physical mechanisms of increasing the hardness of the material in the contact zone "coating-substrate".