Microstructure and High Temperature Oxidation Behaviour of Zr-Doped Aluminide Coatings Fabricated on Nickel-based Super Alloy

In recent years, addition of rare earth elements such as Zr, Y and Hf to pack diffused aluminide coatings has been studied and practiced aiming to improve high temperature oxidation resistance of the coatings. In this work cementation packs containing ZrOCl2.8H2O as the activator and source of zirconium as well as mechanically alloyed 30% Al -Cr compound as the source of aluminum plus alumina as filler material were used to produce zirconium doped aluminide coatings. The cyclic oxidation of the coatings was measured at 1100 °C and each cycle was consisted of one hour heating in furnace and 10 minutes cooling in the air.The results showed that the Zr modified aluminide coatings provide a better resistance against high temperature oxidation and the highest resistance belonged to the coating that was achieved by 5 hours diffusion process in a pack that contained 2% activator.