High-temperature oxidation-resistant NiCr/Al duplex coating on carbon steel substrate

Abstract

In this study, high temperature oxidation-resistant NiCr/Al duplex coatings on carbon steel substrate have been fabricated by electrical wire arc-spraying process. The oxidation resistance properties of NiCr/Al duplex coating system have been evaluated at 800 °C during retention times of 1.5, 3.0, 4.5 and 6.0 hours. The morphology and chemical composition of their cross-sectional structures were investigated using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Micro-hardness and X-ray diffraction (XRD) measurements on the cross-sectional structure of the NiCr/Al coating were also taken place. After the oxidation test, SEM/EDS data indicated the diffusion of aluminum into the NiCr coating whereas XRD patterns revealed the appearance of new phases (Al₃Ni₂ and Al₂O₃). In addition, an increase in micro-hardness (upto 518 - 842 HV) was obtained after oxidation test. These obtained findings indicated that NiCr/Al coating had higher oxidation resistance than NiCr coating. The results suggested that the NiCr/Al duplex coating can be a good candidate for applying to high temperature working parts such as cement plant and waste treatment plant, etc.