In this study, the deep cryogenic treatment (DCT) parameters were systematically optimized to enhance the microstructural integrity, phase stability, and corrosion resistance of an additively manufactured Ni-Fe-Cr alloy. Key process variables soaking temperature, soaking time, heating rate, and cooling rate were varied to evaluate their influence on material performance. DCT effectively reduced retained austenite and promoted martensitic transformation, leading to improved crystallinity and mechanical properties. A 22% increase in hardness (from 37.19 HV to 45.51 HV) and a 7.17% improvement in tensile strength were observed. Secondary carbide precipitation contributed to matrix refinement and internal stress relief. Corrosion resistance improved by 70.28%, with ANOVA identifying the heating rate (54%) and cooling rate (24%) as dominant factors. Dilatometry revealed a 27% reduction in thermal displacement (from 0.13 mm to 0.095 mm at 140 °C), confirming enhanced dimensional stability. These findings demonstrate that a carefully optimized DCT regime can significantly enhance the multifunctional properties of Ni-based alloys fabricated by additive manufacturing.