High temperature corrosion behaviour of microcrystalline aluminide coating on Q235 steel

Abstract

Vibrating electrospark deposition equipment was developed to prepare metal coatings with high deposition efficiency. A Fe–Al intermetallic compound layer with thickness of ∼100 μm was formed on Q235 steel. The experimental results for oxidation in air at 600°C for 200 h and sulphuration in flowing 99·98%SO₂ at 600°C for 50 h using SEM, EDS and XRD analyses show that the high temperature oxidation and sulphuration resistance of sample with aluminide coating have been improved remarkably. The reasons are as follows: first, the Al content of Fe–Al intermetallic compound coating is high enough to form protective oxide scales so that catastrophic oxidation and sulphuration were avoided; second, the microcrystalline structure of coating promotes selective oxidation and the spallation resistance of scales; third, thick aluminide coating can act as the Al reservoir to support the formation of Al₂O₃ oxide scales and the coatings are metallurgically bonded with the substrate. Voltage of 22·5-30 V will be favourable for vibrating electropulse deposition on Q235 steel.