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.