Novel approach for dilution engineered CoCrFeMnNi in-situ weld overlay coating

The CoCrFeMnNi multi-principal element alloy (MPEA), renowned for exceptional mechanical, thermal and corrosion properties, presents challenges in cost-effective deposition. This work demonstrates a dilution-engineered Gas Tungsten Arc Welding (GTAW) in-situ alloying approach using commercially available feedstock (SS304 filler tube + elemental powders). A two-stage strategy was employed includes (1) full-factorial experimental design identifying critical heat input (H.I._c ≈ 784 J/mm) and critical dilution (D_c ≈ 23 at% Fe) and (2) powder volume (P_v) variation (20–60%) to achieve equiatomic composition. Results reveal equiatomic CoCrFeMnNi (20 at% each) achieved at optimized condition of 120 A, 100 mm/min, 30% P_v, with dominant single-phase FCC microstructure, grain refinement (30.6 ± 9.1 µm), and enhanced corrosion resistance (E_corr= −0.34 V vs. −0.51 V for vacuum arc-melted reference). The absence of intermetallic compounds in the micro-hardness survey across interface and superior metallurgical bonding (ASTM-E290 bend test >90° without de-lamination) demonstrate the viability of commercially feasible in-situ alloying for GTAW-based MPEA coatings.