Microstructure and electrochemical behavior of laser treated FeCr and FeCrSiN surface alloyed layers on carbon steel

Laser surface alloyed FeCr and FeCrSiN layers on carbon steel were produced by laser irradiation involving preplaced Fe/Cr and Fe/Cr/Si3N4 powders, respectively. The effects of Cr content (13–25 wt.%) and microstructure on the corrosion behavior of the laser treated FeCr and FeCrSiN alloys in deaerated neutral 3.5 wt.% NaCl solution were studied. Potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements were used to evaluate the corrosion resistance of the surface layers. The results showed that the FeCrSiN treated layer with a fine duplex phase microstructure had a higher pitting potential than the FeCr treated layers. The passive film resistances increased and the passive current density decreased with increasing Cr content in the FeCr layer.