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.