Influence of laser parameters on corrosion resistance of laser melting layer on C45E4 steel surface

The key to further improve the corrosion resistance of the laser melting layer on steel surface is to select appropriate laser parameters. In this paper, a single factor laser melting experiment on C45E4 steel surface by using a pulsed laser beam at a wavelength of 1064 nm and electrochemical analysis were conducted to explore the influences of laser parameters including single pulse energy density, spot overlap ratio and number of laser scans on the corrosion resistance of the laser melting layers. The optimal laser parameter combination was obtained: single-pulse energy density of 3.82 J center dot cm(-2), spot overlap rate of 80 % and 4 number of laser scans. The thickness of the optimal laser melting layer prepared with the optimal laser parameters was only 10.85 mu m, and it had a maximum self-corrosion potential of 1.031 V, a minimum corrosion current of 3.451 x 10(-9) A center dot cm(-2) and a maximum charge transfer resistance of 1541.2 ohm center dot cm(-2). During the salt spray corrosion test, the corrosion rate of the optimal laser melting layer was only one third of that of the traditional hot alkaline blackened layer with a thickness of 12.04 mu m. The results showed that the corrosion resistance of the optimal laser melted layer was significantly improved compared to that of the conventional thermally alkaline blackened layer. The main reason was that the determination of the optimal single-pulse energy density, spot overlap ratio and number of laser scans in turn, made the optimal laser melting layer had a stable Fe3O4-FeO corrosion resistance structure, effectively reduced the surface roughness, microcrack density and oxidation leakage point, and prevented the C45E4 steel surface from being over-oxidized.