Effect of Yttrium Deposition on the Oxidation Resistance of Al-Pack Coated Ni-Based Superalloys

With the aim of formation of thin and solid diffusion layers adherent to superalloys and suppression of void formation, composite aluminide coatings by combination of aluminide pack cementation with yttrium PVD coatings were investigated on ODS superalloys which contain 0.5 to 4.0 mass % Al. The subsequent oxidation of aluminide coated alloys was carried out for 72ks at 1373K in atmospheric pressure of oxygen. The thickness of diffusion zone and the density of precipitates increased in the combination of aluminizing with yttrium coatings. Yttrium coatings are effective in suppressing void formation in the subsequent oxidation not only in the subsurface of the diffusion zone but also in the inside of ODS alloys irrespective of formation of large voids and effective in an increase in their density in the oxidation of aluminide coatings