Effect of Powder Feed Rate on the Structure and Properties of Plasma Deposited Stellite 6 Cladding on SS316L Stainless Steel Substrate

The effect of powder feed rate (PFR) on the structure, phase composition, and mechanical properties of Stellite 6 coating deposited on SS316L steel substrate by plasma welding is studied. It is shown that a high powder feed rate leads to delamination of the coating, and a low PFR leads to an extreme melting depth of the substrate due to the high thermal energy. It is shown that a cobalt-rich fcc phase is formed at low PFR, while the M₂₃C₆, M₆C, MC, and M₇C₃ phases (M is W, Cr, Co, and Mo) are metastable. At high PFRs, a cobalt-rich hcp phase is formed in the coating structure. The cobalt-based hcp phase is more resistant to sliding wear than the other phases. The coatings deposited at higher PFRs increase the hardness and the wear resistance due to formation of an hcp cobalt phase in the structure, but the bond between the substrate and the coating is worse than when using low PFRs. Therefore, for critical components used in the petrochemical industry, Stellite 6 coatings deposited on stainless steel at lower powder feed rates are recommended.