Aluminizing Oil Casing Steeln80by A Low-Temperature Pack Processing Modified With Zinc Addition

Different aluminide coatings were prepared on oil casing steelN80at a relatively lower temperature of 530°C for 2 h by pack powder modified with different content of zinc (Zn). The cross-sectional microstructure, element distribution and properties of as-aluminized oil casing steelN80were investigated by SEM, EDS, micro-hardness test and electrochemical corrosion measurement. Results show that aluminide coating with around 50 μm in thickness can be successfully achieved by a low-temperature pack aluminizing processing with the addition ofZn.Znin the pack powder can enhance the uniformity and continuity of the coating layer, while it has little effect on the thickness of as-packed coating with the increasing content ofZnfrom 38.8 wt.% to 84.4 wt.%. As the content ofZnis over 58.8 wt.%, two layer coating consisting of pureZnlayer andFe–Alaluminide layer can be formed on oil casing steelN80substrate. Furthermore, oil casing steelN80with aluminizing coating shows a higher microhardness than that of original one except in the depth range of pureZnlayer, but the microhardness of oil casing steel substrate does not decrease after aluminizing which can be inferred that low-temperature aluminizing processing reported here will not bring any damages on the mechanical properties of oil casing steelN80. Additionally, a lower self-corrosion current density of oil casing steelN80with aluminizing coating also indicates that low-temperature aluminizing processing is helpful to the corrosion resistance of oil casing steelN80.