Microstructure and electrochemical behavior of laser cladded Fe-Cr-Mo-Si-N surface alloys on carbon steel

Laser surface cladding was used in this study to introduce Fe-Cr-Mo, Fe-Cr-Si-N and Fe-Cr-Mo-Si-N stainless steel layers on carbon steel to improve its corrosion resistance. The cladding materials used were Fe/Cr/Mo, Fe/Cr/Si3N4 and Fe/Cr/Mo/Si3N4 powders which were premixed before laser irradiation. The chemical composition, the microstructure and the electrochemical behavior of the cladded layers were of particular interest and were analyzed. Cyclic potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements were performed to evaluate the corrosion resistance of the cladded layers in a deaerated 3.5 wt.% NaCl solution at pH 4. Experimental results indicated that the Fe-Cr-Mo cladded layers exhibited a lower passive potential range with a higher anodic passive current density, while the Fe-Cr-Si-N and Fe-Cr-Mo-Si-N cladded layers both with a duplex microstructure evidenced a higher passive potential range with a lower anodic passive current density in Cl−-containing solution, as demonstrated by the cyclic potentiodynamic polarization test. The polarization resistance of the laser cladded Fe-Cr-Mo-Si-N layer was higher than that of Fe-Cr-Si-N as determined by electrochemical impedance spectroscopy.