ELECTRON-BEAM AND PLASMA OXIDATION-RESISTANT AND THERMAL-BARRIER COATINGS DEPOSITED ON TURBINE BLADES USING CAST AND POWDER Ni(Co)CrAlY(Sі) ALLOYS PRODUCED BY ELECTRON BEAM MELTING
III. FORMATION, STRUCTURE, AND CHEMICAL AND PHASE COMPOSITION OF THERMAL-BARRIER Ni(Co)CrAlY/ZrO₂–Y₂O₃ COATINGS PRODUCED BY PHYSICAL VAPOR DEPOSITION IN ONE PROCESS CYCLE 

Abstract

Physical and chemical vapor deposition methods are used to apply thermal barrier coatings (TBCs) to turbine blades, and operations aimed at forming a diffusion barrier layer are an individual process, which increases the coating application time and, accordingly, increases the energy consumption of in the production of turbines. In this effort, the formation of barrier layers at the ‘base blade material/heat-resistant metal layer’ and ‘heat-resistant metal layer/ceramic layer’ interfaces was studied using the combination of deposition processes. The structure and chemical and phase composition of TBCs at the metal/ceramic interface (NiCrAlY and CoCrAlY alloys/ZrO₂–(6–8 wt.% Y₂O₃) ceramics deposited in one process cycle. The study focused on were samples cut from blades made of the directionally crystallized ZhS26-BI alloy. The NiCrAlY and CoCrAlY alloys were used for coating the blades. The experiments were performed using L2 and UE-159 units at the Ivchenko-Progres (Zaporizhzhia) and Eltechmash (Vinnytsia) enterprises. The formation of a diffusion barrier layer at the metal/ceramic interface was examined when the blades preheated to 900 ± 30 °С were kept for some time above the surface of the ZrO₂–(6–8) wt.% Y₂O₃ ceramic material at 2600 ± 50 °С. Depending on the holding time, the diffusion barrier layer formed at the interface between the metal and ceramic layers significantly differs in morphology and chemical composition from the main TBC layers. The chemical and phase composition of the diffusion barrier layer was determined against conditions of TBC deposition. The results of thermal cycling studies of the coated blades were used to develop coating deposition modes that promote a diffusion barrier layer with optimal composition and structure.