Surface modification of carbon steel with laser treated nitrogen-containing stainless steel layers

Laser surface alloying was used in this study to introduce nitrogen-containing stainless steel layers on carbon steel to improve its corrosion resistance. The alloying materials used were Fe-Cr-Ni-Si3N4 and Fe-Cr-Mn-Si3N4 powders which were pre-mixed before laser irradiation. The chemical composition, the microstructure and the electrochemical behavior of the alloyed layers were of particular interest and analyzed. Potentiodynamic polarization tests were performed to evaluate the corrosion resistance of the laser treated alloys in deaerated 3.5 wt.% NaCl solution at pH 4. Two austenitic stainless steels, namely 316L and F900N, were tested for comparison. Experimental results indicated that nitrogen contents in the laser treated Fe-Cr-Ni-Si-N and Fe-Cr-Mn-Si-N alloys could reach 0.38 and 0.83 wt.% respectively. The Fe-Cr-Ni-Si-N layer exhibited higher resistance to pitting corrosion in Cl- containing solution as compared with those of 316L and P900N stainless steels. However, the pitting corrosion resistance of Fe-Cr-Mn-Si-N layer was inferior to those of the 316L and P900N stainless steels.