Plasma-sprayed duplex and graded partially stabilized zirconia thermal barrier coatings: deposition process and properties

Atmospheric plasma spraying of duplex and graded ZrO2 (8% Y2O3) thermal barrier coatings (TBCs) on Inconel 617 substrate with a NiCrAlY bond coat is described in terms of a deposition process of con-trolled coating structure. Special attention is devoted to the dominant spray parameters and the injector configuration for powder feeding, which play a fundamental role in graded coating deposition with con-trolled formation of a graded metal-ceramic (GMC) intermediate zone. The results of the graded coating spraying allow: (a) suppression of step-interface effects, (b) suppression of large differences (misfit) be-tween physical and mechanical constants of the coating and those of the substrate material, and (c) favor-able intergrowth of crystallites for a microstructurally integrated structure. Sprayed TBCs were investigated and compared with regard to their thermal cycling, oxidation behavior, and mechanical properties.