Effect of Copper Content on the Microstructure and Electrochemical Corrosion Behavior of Laser Cladding 316L Stainless Steel Coating

To evaluate the effect of copper (Cu) content on the microstructure and corrosion resistance of austenite stainless steel, 316L stainless steel coatings with varying Cu contents were prepared by laser cladding. The phase composition, microstructure, and electrochemical corrosion behavior of the coatings were studied in detail. The results indicated that γ-Fe was the dominant phase in the 316L stainless steel coating, and ε-Cu appeared after the addition of Cu. The incorporation of Cu was beneficial for refining the typical dendrite structures. Potentiodynamic polarization tests in 0.5 M H2SO4 solution revealed that as the Cu content increased, the corrosion potential of the coating became more positive and corrosion current density decreased, demonstrating that the addition of Cu could improve the corrosion resistance of the coating. Similar conclusions were also obtained from long-term electrochemical impedance spectroscopy tests. By characterizing the Mott-Schottky curve and element valence of the passivation film on the Cu-containing 316L stainless steel coating, it was found that Cu addition could reduce the point defect density and improve the stability of the passivation film. Moreover, Cu could also promote the enrichment of oxidized-state Cr and Cu/Cu2O in the passivation film, making it more protective.