Effect of nickel pre-plating on high-temperature oxidation behavior of hot-dipped aluminide mild steel

An aluminide/nickel duplex coating was prepared on mild steel by nickel pre-plating before hot-dip aluminizing. The isothermal and cyclic oxidations of the hot-dipped aluminide mild steel were performed at 750 °C in a static atmosphere. The effect of nickel pre-plating on the high-temperature oxidation behavior of the aluminide mild steel was studied. The results from the aluminide steel after isothermal oxidation show that the phase transformation in the aluminide layer was dominated by Ni/Al interdiffusion, leading to the aluminide layer being composed of Ni-Al intermetallic phases. Meanwhile, the aluminide layer was void-free. The result from the aluminide steel after cyclic oxidation is similar to that after isothermal oxidation. The aluminide layer has excellent thermal shock resistance, which did not form any cracks during cyclic oxidation. The oxidation kinetic result from the aluminide steel, after high-temperature oxidation, is consistent with the microstructure and phase constitution of the aluminide layer. The low oxidation rate of the aluminide steel proves that nickel pre-plating before hot-dipping can improve the oxidation resistance of the hot-dipped aluminide steel, especially under condition of cyclic oxidation.