Cyclic Oxidation Behavior of Iridium-Modified Aluminide Coatings for Nickel-Base Single Crystal Superalloy TMS-75

Abstract

The oxidation behavior of iridium-modified aluminide (Ir-Al) coating obtained by a two-step process was investigated. A pure Ir layer was first electrodeposited on the nickel-base single crystal superalloy TMS-75, and then the Ir-coated TMS-75 was treated by a conventional low activity pack-cementation aluminizing process. The oxidation resistance of the Ir-Al coated TMS-75 and the simply aluminized TMS-75 was evaluated by a cyclic oxidation test at 1373 K in air. The results showed that the Ir-Al coated TMS-75 had better thermal cyclic oxidation resistance than the simply aluminized TMS-75. The existence of Ir in the Ir-Al coatings may promote the formation of dense and adherent Al2O3 scale and thus retard the degradation of β-(Ir, Ni)Al phase during oxidation process.