Inter-diffusion behavior of recoated CoCrAlY coating/DZ125 directionally solidified superalloy

The thermal barrier coatings (TBCs) are widely used in gas turbines which could lower the surface operating temperature and improve the service life of the coated part component. When repair or refurbishment of these coated components, it is necessary to remove the coating and replace it with a new coatings. The CoCrAlY coatings were deposited by EB-PVD on the directionally solidified nickel-based superalloy DZ125. The coatings were removed via physical methods in varying thicknesses and recoated subsequently. The results showed that the depth of the removal had a significant impact on the inter-diffusion behavior as well as the oxidation resistance. The thickness of Al-depleted zone formed in the recoated coatings after oxidation are thinner than the first coated coatings. Moreover, the more the coating was removed, the thinner the Al-depleted zone was formed. The recoated coatings deposited on the substrate removed the entirely inter-diffusion zone (IDZ) showed the best oxidation resistance, and the IDZ formed after oxidation was similar to the first coated coatings.