Electrometallurgy Today, 2022, №03



2022 №03 (01)

DOI of Article 10.37434/sem2022.03.02

2022 №03 (03)

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Electrometallurgy Today (Sovremennaya Elektrometallurgiya), 2022, #3, 11-17 pages

Development of the CoCrAlY/ZrO₂–8 % Y₂O₃ type thermal barrier coating by surface doping of the metal layer with aluminum

K.Yu. Yakovchuk¹, G.P. Myalnitsya², A.V. Mykytchyk¹, Yu.E. Rudoy¹, R.O. Tkach¹

¹State-Run Enterprise «International Center for Electron Beam Technologies of the E.O. Paton Electric Welding Institute, NASU», 68 Antonovych Str. 03150, Kyiv, Ukraine. E-mail: yakovchuk@paton-icebt.kiev.ua
²State-Run Enterprise «Gas Turbine Research & Production Complex «Zorya»-«Mashproekt». 42-a Bohoyavlenskyi Prosp., 54018, Mykolayiv, Ukraine. E-mail: presz@zorya.com.ua

Abstract
The diffusion processes occurring at aluminum enrichment of the CoCrAlY overlayer during vacuum annealing from the slurry suspension applied to its surface and their influence on the structure, chemical composition and properties of CoCrAlY/ZrO2–8 % Y2O3 electron beam evaporated on nickel-based superalloy samples were studied. It is shown that the diffusion layer formed on the surface of the CoCrAlY alloy, enriched in aluminum, has a heterogeneous thickness and contains two microstructural zones with different aluminum content (external zone with aluminum up to 31 % and inner with aluminum up to 19 %). It was found that during vacuum heat treatment, cobalt and chromium diffuse into the slurry layer. As a result, microhardness increases up to 9 GPa and microcracks that propagate into the CoCrAlY layer are formed. The parameters of low-temperature heat treatment, which provides the formation of a defect-free diffusion zone in CoCrAlY, are established. The attained results allowed us to optimize the technology of CoCrAlY layer thermodiffusional alumization from the slurry for CoCrAlY/ZrO2–8 % Y2O3 coatings in order to increase the operating temperature of the turbine blades made of CM-88U and CM-93 superalloys. Ref. 9, Tabl. 6, Fig. 7.
Keywords: electron beam physical vapor deposition; thermal barrier coatings; nickel-based superalloy; CoCrAlY metal bond coat; thermodiffusional alumization; slurry; thermally grown Al2O3 oxide (TGO); ZrO2–8 % Y2O3 outer ceramic layer, diffusion of elements

Received 30.06.2022

References

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