Oxidation behavior and microstructural evolution of hot-dipped aluminum coating on Ti-6Al-4V alloy at 800 °C

An aluminized Ti-6Al-4V alloy was prepared successfully by hot-dipping aluminum under a protective argon atmosphere at 800 °C. After isothermal oxidation tests at 800 °C for various times, the weight gain of the hot-dipped aluminum coating showed the aluminized coating can provide a significant degree of protection against oxidation at 800 °C. In addition, the coatings of as-coated hot-dipped aluminum and those after being exposed from 1 to 96 h were also evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS) analyses as well as Vickers microhardness test. Consequently, the microstructures of the hot-dipped aluminum coating were found to consist of an outer layer and a multilayer reaction zone. We found that a mixture of (Ti,V)Al3 and (Ti,V)Al2 phases exist in the outer layer and that (Ti,V)Al2, (Ti,V)Al, and (Ti,V)3Al phases form in sequence within the reaction zone after oxidizing for up to 96 h.