Crack reduction in electron beam cladding of AlCoCrFeNiCu high entropy alloy coatings by resistance seam welding pre-alloying

A major drawback in the application of AlCoCrFeNiCu high-entropy alloy (HEA) coatings is a susceptibility to hot-cracking, which is closely related to a grain boundary segregation due to the low melting point Cu component. Reducing or eliminating the grain boundary segregation of Cu is an effective means of reducing cracking in the HEA coating. In this study, blended and partial pre-alloyed powders were used as feedstock to fabricate the AlCoCrFeNiCu coating. The application of electron beam (EB) cladding to partial pre-alloyed powders, prepared by resistance seam welding (RSEW), resulted in an appreciable reduction of crack density in the coating. This response is attributed to the formation of Ni3Al and Al4Cu9 promoted by the relatively low heat generated during the RSEW process. In subsequent EB cladding, nanoscale Me3Al (Me = Cu, Ni) replaced the Cu-rich phase at grain boundaries. The hardness and wear resistance of coatings using partially pre-alloyed powders were 17.2 % and 15.8 % higher, respectively, than blended powders. The findings of this study indicate that the use of partial pre-alloyed powders can offer a new effective approach to reducing the hot cracks in EB cladding AlCoCrFeNiCu HEA coatings.