The objective of the study was to develop an alloy with a significant proportion of the γ′ phase and solvus, together with an optimal thermal processing range, by employing the CALPHAD (Calculation of Phase Diagrams) approach. The alloy composition employed consisted of iron (Fe), copper (Cu), silicon (Si), tungsten (W), and molybdenum (Mo) in the proportions of 30 %, 10 %, 10 %, 6 %, and 10 % respectively. The actual results validated the calculations and showed that Mo is a constituent that forms the γ phase in Fe-Cu-Si-W-based alloys. Molybdenum (Mo) is added to the alloy to mitigate the discrepancy in lattice structure, impede the formation of bigger particles, and lower the overall density of the alloy. The inclusion of a precise amount of Mo led to the formation of a superalloy that demonstrates a combination of superior mechanical performance at the γ′ solvus and a reduced density. Furthermore, the incorporation of Mo can greatly improve the ability of the Fe-Cu-Si-W high-temperature alloy to resist oxidation. At a temperature of 1000°C, the Fe-30Cu-10Si-6W-10Mo alloy showed minimal weight gain from oxidation, demonstrating its outstanding resistance to oxidation. The primary cause of this phenomenon is the formation of continuous layers of (Fe, Cu) (Si, Mo)2O4 spinel oxide after prolonged oxidation. © 2025 Elsevier B.V., All rights reserved.