High-temperature Corrosion Resistance of Composite Coating Prepared by Micro-arc Oxidation Combined with Pack Cementation Aluminizing

Al₂O₃ ceramic film was obtained by micro-arc oxidation (MAO) process on Al/C103 specimen, which was prepared by pack cementation aluminizing technology on C103 niobium alloy. With the aid of XRD and SEM equipped with EDS, chemical compositions and microstructures of the composite coatings before and after high-temperature corrosion were analyzed. The behavior and mechanism of the composite coatings in high-temperature oxidation and hot corrosion were also investigated. The results indicate that oxidation mass gain at 1000℃ for 10h of the Al/C103 specimen is 6.98mg/cm², and it is 2.89mg/cm² of the MAO/Al/C103 specimen. However, the mass gain of MAO/Al/C103 specimen (57.52mg/cm²) is higher than that of Al/C103 specimen (28.08mg/cm²) after oxidation 20h. After hot corrosion in 75%Na₂SO₄ and 25%NaCl at 900℃ for 50h, the mass gain of Al/C103 and MAO/Al/C103 specimens are 70.54mg/cm² and 55.71mg/cm² respectively, Al₂O₃ and perovskite NaNbO₃ phases are formed on the surface; the diffusion of molten salt is suppressed, due to part of NaNbO₃ accumulated in the MAO micropores. Therefore, MAO/Al/C103 specimen exhibits better hot corrosion resistance.