Wear resistance of alumina-coated oil casing steel N80 via MAO with rare earth additive

The wear resistance of oil casing steel N80 was improved by packing its aluminide prelayer at a relative low temperature. Then, an alumina coating was obtained through microarc oxidation (MAO), in which different La2O3 contents were added into the electrolyte. The chemical compositions and microstructures of the as-prepared coatings were characterized through scanning electron microscopy (SEM) equipped with energy-dispersive spectrometer (EDS). The wear resistance of the coated oil casing steel N80 under simulated oil and gas well condition was also investigated. With 1.5 g/L La2O3 addition, a denser alumina coating containing α-Al2O3 and γ-Al2O3 with 1750 HV microhardness value was obtained. Under the simulated oil and gas well wear condition, the oil casing steel N80 with an alumina ceramic coating, which was prepared by adding 1.5 g/L La2O3 in the electrolyte, showed a stable friction coefficient and low weight loss. Among the steel samples in this study, the oil casing steel N80 with an alumina ceramic coating exhibited the least wear debris and the shallowest groove. The influence mechanism of rare earth on the microstructure of the ceramic coating via MAO was discussed in detail.