Cyclic oxidation and diffusion barrier behaviors of oxides dispersed NiCoCrAlY coatings

Abstract

NiCoCrAlY has been widely used as the bond coat material in thermal barrier coatings (TBCs). Inter-diffusion between the bond coat and superalloy could degrade the performance of the coating and the mechanical properties of the superalloy. In this paper, oxide dispersed (OD) NiCoCrAlY coatings were deposited onto superalloy DZ 125 using EB-PVD by introducing oxygen during the deposition process. Cyclic oxidation and inter-diffusion behaviors of the coated specimens at 1323 K were investigated. The OD coating deposited with high level oxygen input effectively prevented outward diffusion of the elements such as Hf and W in superalloy. For the conventional NiCoCrAlY coating, Hf migrated to the coating surfaces and caused accelerated thickening and chipping spallation of TGO. The OD coating with high level oxygen input exhibits an improved cyclic oxidation resistance as compared to the conventional NiCoCrAlY coating and the OD coating with lower level of oxygen input.