Preparation and Performance of Ni-Al and 3Cr13 Coatings on Carbon Steel by Arc Spraying for Boiler Heat Exchanger Pipelines: A Comparative Study

This study compares nickel-aluminum (Ni-Al) and 3Cr13 steel coatings deposited on carbon steel substrates by arc spraying. The objective is to select a coating that will improve the corrosion and abrasion wear resistance of boiler heat exchanger pipes. This comparison involves the study of the microstructure, phase composition, microhardness, wear and erosion, and corrosion resistance of the coatings. The corrosion resistance was evaluated based on seawater immersion, electrochemical impedance, polarization, and galvanic corrosion tests. The results showed that the Ni-Al coating had a porosity of 6.3%, while the 3Cr13 coating had a porosity of 5.2%. The average surface roughness of the 3Cr13, Ni-Al coatings, and polished substrate were 11, 14.4, and 0.13 μm, respectively. The 3Cr13 lamellar structure coating was mainly composed of the α-Fe phase and a small amount of the CrO phase, and the Ni-16wt%Al coating included a solid solution phase and a small amount of the NiO phase. During the wear tests, the Cr13 steel coating had the highest microhardness and the best abrasion resistance at room temperature at the initial stage of friction. However, its abrasion resistance was lower than that of the Ni-Al coating after a 10-min friction test. The friction coefficients of the two coatings were almost the same at 300 °C. The corrosion resistance of the Ni-Al coating was better than that of the 3Cr13 steel coating. The current density of galvanic corrosion of the 3Cr13 coating was 108 μA m-2 and that of the Ni-Al coating was 37 μA cm-2, indicating that galvanic corrosion occurred between the substrate and the coating. This comparison showed that the Ni-Al coating could provide better high-temperature abrasion resistance and anti-corrosion performance for boiler heat exchanger piping compared with the 3Cr13 steel coating.