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Abstract Laves phase segregation is a universal phenomenon in additive manufactured or as-cast Inconel 718 alloy, and the Laves phase usually degrades the mechanical properties of the matrix. In this work, nickel-based alloys designed with different Nb contents were successfully fabricated by laser metal deposition (LMD) via a dual-feed system, and the Laves phase distribution at the macro level was relatively uniform. The effects of Nb content on the microstructure, mechanical properties and surface potential of the as-received and heat-treated nickel-based alloys were investigated. The grain size of the as-received LMD nickel-based alloys decreased with the Nb content, and the Laves phase exhibited a universally higher nano-hardness but lower surface potential than the γ matrix. The nano-hardness of the Laves phase linearly increased, whereas the Volta potential decreased with the Nb content. The strength improvement for the as-received LMD nickel-based alloys with different Nb contents was equally attributed to grain refinement and enhancement of the Laves phase (both hardness and content), while the increase in the precipitate content (main γ″) as a function of Nb content contributed to the substantial improvement in hardness for the heat-treated LMD nickel-based alloys and the grain refinement strengthening effect was comparative minor after aging treatment. Graphical abstract Image 1 Highlights • Graded nickel-based alloys were fabricated one-time via a dual-feed system. • Nb content errors of the designed parts were all within 4%. • Strength improvement was attributed equally to grain refinement and Laves phase. • γ″ precipitation ascribed to the hardness improvement for heat-treated alloys. [ABSTRACT FROM AUTHOR]