Laser surface remelting of Fe-based alloy coatings deposited by HVOF

• Published in: Surface & coatings technology 2012-01, Vol.206 (8), p.2388-2395
• Main Authors: Cui, Chong, Ye, Fuxing, Song, Guirong
• Format: Article
• Language: English
• Subjects: Applied sciences; Coatings; Corrosion; Corrosion environments; Corrosion resistance; Cross-disciplinary physics: materials science; rheology; Electrical steels; Electrochemical impedance spectroscopy; Exact sciences and technology; Fe-based alloy; Ferrous alloys; Flame spraying; HVOF; Intermetallic compounds; Laser surface remelting; Lasers; Materials science; Melting; Metallic coatings; Metals. Metallurgy; Microhardness; Physics; Porosity; Production techniques; Remelting; Silicon steels; Surface treatment; Surface treatments
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2011.10.038

Fe-based alloy coatings were deposited onto Fe360A (ISO 630) substrates by the High Velocity Oxy-Fuel (HVOF) technique. A Nd:YAG laser was used to remelt surfaces of the coatings. The experimental parameters were determined using an orthogonal experimental design approach. The microstructure and microhardness were studied using a metallographic microscope and a microhardness tester. The phase compositions were investigated by X-Ray Diffractomer (XRD). The effect of laser surface remelting on the corrosion resistance of Fe-based alloy coatings was evaluated by electrochemistry methods using a 10 wt.% NaOH solution. It was found that there were four types of typical shapes of laser surface remelting pools. Large holes inside the coatings could be avoided when the remelted thickness was equal to or greater than the thickness of as-sprayed coatings. The microstructure of the laser surface remelted coatings was homogeneous, and its microhardness was promoted from an average of 600 HV 0.1 to 900 HV 0.1 because of emergence of the high hardness compounds such as SiO 2 and Fe 3Si after laser surface treatment. The remelted thickness was found to have a linear relationship with the laser power density, while the microhardness of laser surface remelted coatings exhibited a parabolic relationship. Analysis of the polarization curves showed that the free corrosion current density of laser surface remelted coatings could be lowered down from 25.63 μA/cm 2 to 12.99 μA/cm 2. Results of the electrochemical impedance spectroscopy (EIS) also indicated that laser surface remelting could improve the corrosion resistance of Fe-based alloy coatings. ► An Fe-based alloy coating applied to corrosion resistance was laser surface remelted. ► Four kinds of typical shapes of laser surface remelting pools were discussed. ► Relationship between remelted alloy height and laser power density was studied. ► Corrosion resistance of coatings before and after laser surface remelting was studied.