Surface strengthening of Ni_32-xCo₃₀Cr₁₀Fe₁₀Al₁₈Ti_x eutectic high-entropy alloys by laser remelting and heat treatment

Eutectic high-entropy alloys (EHEAs) have excellent properties with in situ two-phase composites. In EHEAs, the combination of hard and soft phases generates promising applications in the area of wear. Laser remelting modification and heat treatment can be used to further regulate the surface microstructure for the enhancement of surface properties. In this investigation, the surface hardness of Ni_32-xCo₃₀Cr₁₀Fe₁₀Al₁₈Ti_x EHEAs was significantly improved by laser remelting and subsequent aging. It was found that the remelted area of the alloy showed a refined microstructure and the nanoindentation confirmed the increased microhardness from the substrate to the remelted area. The optimal aging process was explored to further strengthen the surface by introducing precipitates while avoiding severe coarsening of the matrix. The surface of the remelted and the aged Ni₂₉Co₃₀Cr₁₀Fe₁₀Al₁₈Ti₃ alloy has the highest average microhardness of ~ 620 HV.