Hardness enhancement mechanism of AlxCoCrFeNiSi high-entropy alloy coatings prepared by laser cladding.

In the present work, Al x CoCrFeNiSi high-entropy alloy coatings with Al content of 0.3 and 1.0 were prepared by laser cladding technology. The microstructure and crystallographic structure evolution, hardness, and strengthening mechanisms were systematically investigated. The coherent interface between the BCC phase and Al–Ni nano-precipitate was confirmed by TEM analysis. Al 0.3 coating exhibited a greater dislocation density and lots of sub-grain structures with grain boundary misorientation of less than 2.5°. The average grain size decreased from 29.94 μm to 20.05 μm with the increase of Al from 0.3 to 1.0. Dislocation strengthening and solid solution strengthening were the major strengthening mechanisms for Al 0.3 coating resulting in a hardness of 692 HV 0.2 , while solid solution strengthening and fine-grain strengthening were the strengthening mechanisms for Al 1.0 coating with a hardness up to 711 HV 0.2. • Al x CoCrFeNiSi (x = 0.3, 1.0) HEAcs were prepared by laser cladding. • The influences of Al content on microstructure, crystallographic structure evolution, and hardness enhanced were investigated. • The strengthening mechanisms of prepared HEAcs were clarified. [ABSTRACT FROM AUTHOR]