Multicomponent AlSiNiCoFeCr and AlSiNiCoFeCrTi High-Entropy Coatings on Steel

Background. In many situations, only the contact surface properties are important in determining performance of the component in practical applications. Therefore, the use of a coating from materials with high physical and mechanical characteristics, such as high-entropy alloys (HEA), has several attractive advantages. HEAs have been found to have novel microstructures and unique properties. Considering HEA's tendency to form simple structures, fabricating HEA coating by electron beam welding process is of great significance and potential for extensive use. Until now this novel method for preparing HEA coatings has just been reported by any organizations. Objective. The purpose of this work is to study the features of microstructure, phase and chemical composition, and microhardness of HEA coatings, produced by electron-beam welding on steel substrate of 6 and 7-component powder equiatomic mixtures of the system Al–Si–Ni–Со–Fe–Cr–Ti. Methods. The coatings were obtained by electron-beam welding. The microstructure, chemical composition, and constituent phases of the synthesized coatings were characterized by SEM, EDX, and XRD analysis, respectively. Microhardness was also evaluated. Results. Experimental results demonstrate that the AlSiNiСоFeCr and AlSiNiСоFeCrTi HEA coatings are composed of only three substitutional solid solutions with body-centered cubic (BCC) structure and different lattice parameter due to different component concentration. The coatings exhibit dendritic microstructure with different size and morphology. The Vickers's hardness of AlSiNiСоFeCr and AlSiNiСоFeCrTi HEA coatings has been found to be HV = 9.2 ± 0.2 and HV = 11.25 ± 0.3 GPa, respectively, and is much higher than that of the similar alloys prepared by laser cladding technique. Conclusions. Evidence from multicomponent powder mixtures of the Al–Si–Ni–Со–Fe–Cr–Ti system, it is possible to form HEA coatings consisting of solid substitution solutions with a BCC structure and all initial components by electron-beam welding method. Through the strong crystal lattice distortion of solid solutions at the mutual dissolving of dissimilar atoms of AlSiNiCoFeCr and AlSiNiCoFeCrTi, HEA coatings have a high microhardness that is much higher than the hardness of the initial components.