Improving the oxidation resistance of NiCrAlY-coated superalloy by Zr/ZrN diffusion barrier

Abstract

The elemental interdiffusion between the bond-coat in thermal barrier coatings and the superalloy substrate has emerged as a critical factor in the failure of turbine blades. In order to mitigate this elemental interdiffusion, a Zr/ZrN diffusion barrier was strategically designed and deposited between the NiCrAlY bond-coat and the superalloy substrate using multi-arc ion plating. The performance of the as-deposited coatings was evaluated through annealing, quenching, thermal cycle oxidation, and isothermal oxidation tests. The microstructural evolutions of the Zr/ZrN diffusion barrier and the NiCrAlY bond-coat were investigated. The Zr/ZrN diffusion barrier exhibited remarkable bonding strength and diffusion barrier effect. Importantly, the structural integrity of the diffusion barrier remained unaffected by thermal stresses during quenching and thermal oxidation tests. Additionally, twins were observed within the ZrN layer after thermal cycle oxidation tests. The application of the Zr/ZrN diffusion barrier layer substantially enhanced the oxidation resistance of NiCrAlY by preventing the depletion of Al. These results suggest that ZrN holds promise as a favorable candidate material for diffusion barriers.