Electrometallurgy Today, 2017, №04



2017 №04 (01)

DOI of Article 10.15407/sem2017.04.02

2017 №04 (03)

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Electrometallurgy Today (Sovremennaya Elektrometallurgiya), 2017, #4, 8-16 pages

Structure and properties of condensed gradient metal-ceramic thermal barrier coatings with NiAl-bond coat alloyed with Y, Hf, Dy

K.Yu. Yakovchuk¹, Yu.E. Rudoy¹, A.V. Mykyktchyk¹, E.V. Onoprienko²

¹State-Run Enterprise «International Center for Electron Beam Technologies of E.O. Paton Electric Welding, NASU». 68 Gorky (Antonovich) Str. 03150, Kyiv, Ukraine. E-mail: yakovchuk@paton-icebt.kiev.ua
²«OPTEC» Group. 8 Illinskaya Str., 04070, Kyiv, Ukraine. E-mail: onoprienko@optecgroup.com

The analysis of modern methods for improving the service characteristics of NiAl heat-resistant alloy, used as a bond coat in thermal barrier coatings (TBC), was carried out by introducing active elements (AE), for example Y, Hf, Dy, into its composition. The article contains results of investigation of structure and properties of NiAl/ZrO2–8 % Y₂O₃ condensed TBC of 40...50/140...160 ?m thickness on ZhS-32VI super alloy samples with Y, Hf, Dy additives in NiAl, including gradient distribution of their concentration across the thickness of NiAl layer. It was found that the additions of active elements reduce the average grain size of the condensed NiAl layer by 4–5 times. It was shown that AEs in the bond layer are precipitated both along the boundaries and also inside the NiAl grains in the form of particles ranging in size from 5 nm to 20 ?m, depending on the level of their concentration. It has been established that graded NiAlDy/ZrO2–8 % Y₂O₃ coatings, in which the dysprosium content gradiently rises with NiAl layer thickness, reaching a maximum (4...9 %) at the interface with outer ceramic layer, possess the highest thermal cyclic life during tests in air at the 40...1150 ?С temperature mode. It is noted that the positive effect of Dy, as compared to, Y introduction into the NiAl composition, is provided due to the inhibition of Al diffusion (about 1, 2 times), delaying the Al₂O₃ scale growth rate at the metal-ceramic interface and the increase of adhesion of the scale layer by the growing-in of spindle-shaped precipitates of oxides on dysprosium base into the scale layer. 19 Ref., 13 Fig.

Key words: condensed gradient thermal barrier coatings; outer ceramic layer on zirconium dioxide base; heat-resistant NiAl bond coat; active elements Y, Hf, Dy; super alloys; thermal cyclic life of TBC
 
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