| FeCrAl coating and NiCr coating produced by high velocity eletric arc spraying technology (HVAS) on the structural materials exhibite excellent high-temperature corrosion resistance and good wear-resistant features. So these coatings can be used in the field of prevention of corrosion in high-temperature environments and resistance to wear for the water-wall tubes of boilers in heat-engine plant, and they might rapidly lead to the industrial applications.In this study, microstructure of the FeCrAl coating and NiCr coating produced by HVAS have been analyzed by using modern testing techniques, such as scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersive spectrometry (EDS), light microscope technique, et al. The bond strength, high-temperature corrosion resistance, wear-resistant feature, thermal shock resistance and porosity of coatings produced by HVAS have been studied through a series of experiments as well as the mechanical property of coatings such as Young's modulus of coatings. Main results are summarized as follows:The SEM and XRD methods is used to analyze the microstructure of the FeCrAl coating and NiCr coating produced by HVAS. The microscopic structure of coatings appears typical layered structure characteristics. The coatings have high density, have not coarse pore, and have very thin oxide films and a small quantity of gas porosity. The phase composition of surface of FeCrAl coating is composed of iron-based solid solution and a little Fe2O3; the phase composition of surface of NiCr coating is composed of nickel-based solid solution, Cr2O3 and NiCr2O4.The bond strength of FeCrAl coating produced by HVAS has been studied . The bond strength between FeCrAl coating and NiAl bonding coating is more than the bond strength between NiAl bonding coating and base metal. Moreover, the study indicates that the process of producing NiAl bonding coating previously can be omitted if the blast sanding has been carried out on the surface of base metal .The study indicates that corrosion resistance of NiCr coating by HVAS is better than corrosion resistance of FeCrAl coating by HVAS and 20# steel, and corrosion resistance of FeCrAl coating by HVAS is highly better than corrosion resistance of 20# steel. The anti-corrosion mechanisms of coatings are evaluated. On the one hand, the Cr2O3 and spinel structure oxide formed firstly can effectively restrain the corrosion, so the NiCr coating have excellent high-temperature corrosion resistance. The loose Fe2O3 formed in low-temperature hot corrosion of FeCrAl coating is the main reason why the corrosion resistance of FeCrAl coating is in some sort worse than the corrosion resistance of NiCr coating. On the other hand, the porosity of coatings produced by HVAS is far lower than coatings produced by electric arc spraying technology, which also make for the elevation of corrosion resistant feature of coatings produced by HVAS. In addition, the porosity of FeCrAl coating is higher than that of NiCr coating. The fracture mechanism of coatings produced by HVAS in the cycle of heating and cooling is put forward. The difference of the thermal physical property between coatings and base metal results in the forming of thermal stress in the inner of coatings. Consequently, the coatings spall from the base metal.The wear mechanisms of FeCrAl coating have been analyzed. The experiment results have proved that wear-resistant feature of FeCrAl coating is far better than 20g steel. The stripping wear and abrasive material wear of coating metal particle have occurred in the friction wear testing in condition of oil wear.The mechanical property of FeCrAl coating and NiCr coating produced by HVAS is deep studied. Some flaws, such as gas hole, inevitably exit in the coatings. The flaws result in the factual capacity of coating is smaller than the capacity which we observe macroscopically. Therefore, the Young's modulus of coatings is far lower than that of the wires used for producing coatings. Moreover, the higher porosity of coating is, t...
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