Laser-clad CoCrFeMo 0.85 Ni compositionally complex alloy (CCA) coatings were fabricated from gas atomized (GA) and mechanically alloyed (MA) powders, forming dense, adherent multilayer structures of FCC, BCC, and intermetallic σ-phases. The MA resulted in a more heterogeneous multiphase microstructure and lower hardness. Both coatings exhibited localized pitting corrosion. The GA produced a more chemically uniform FCC-based microstructure with spatially segregated σ-phase, reducing local electrochemical driving forces for micro-galvanic corrosion and pit initiation, although localized breakdown persisted once passivity was lost. Wear performance in both coatings was governed by abrasive and adhesive mechanisms facilitated by oxide formation, with maximum wear depth below 10% of the coating thickness. • Microstructure and elemental segregation govern the wear and corrosion behavior in GA and MA-derived coatings. • Mo addition modulates FCC–BCC/σ phase balance in CoCrFeNi-based CCAs, depending on powder processing route. • GA-derived coatings show higher hardness and more refined microstructure compared to the MA. • BCC/σ phases contributes to passive film formation, while σ phase helps improve pitting resistance. • Passive films on GA-derived coatings demonstrate stable behavior but limited repassivating ability in chloride media.
Oppong et al. (Sun,) studied this question.