Formation and phase transformation of aluminide coating prepared by low-temperature aluminizing process

A low-temperature aluminizing process involving a surface slurry pre-coating and powder embedded aluminizing process, with AlCl3 as the chosen activator, was developed to avoid changes in the mechanical properties of the substrate at high temperatures. An electrolytic polishing process using an acidic electroplating solution was further adopted to improve the average surface roughness of the aluminide coating and the smoothing mechanism was explained. Heat treatment promotes the diffusion of iron into the coating and aluminum into the substrate, the phase structure of the coating changed simultaneously. After a 30 h heat treatment at 700 °C, the brittle phases of Fe2Al5 and FeAl3 disappeared and the aluminide coating completely transformed into the Fe3Al and FeAl phases no cracks were observed inside the coating. Through the above processes, a dense and ductile aluminide coating was obtained with a thickness of about 60 μm.