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Microstructure, mechanical and thermal properties of YSZ thermal barrier coatings deposited by axial suspension plasma spraying

Poliarus Olena, Morgiel Jerzy, Żórawski Wojciech, Góral Anna, Pomorska Małgorzata, Wojciechowski Krzysztof T., Cherniushok Oleksandr

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no., e89, 2023

EN

Yttrium-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are indispensable elements of present-day turbine propulsion systems. The ones deposited with atmospheric plasma spraying (APS) are characterized by required low thermal conductivity, but they are unable to survive frequent thermomechanical loading and therefore their application is limited to parts remaining stationary. Expanding capability of TBCs is sought in various areas, but the one realized through modification of most proliferated apparatus used for plasma spraying (PS) (from radial to axial injection) and substituting micrometric powders with the nano-structured suspension needs least changes in the industry established procedures and offers the highest property improvement. The present experiment covered the deposition of ZrO2-8Y2O3 YSZ TBC using both atmospheric and suspension PS processes. They were performed with commercial micrometric and nano-structured YSZ (8% Y2O3) powders. The coatings morphology and microstructure were characterized with 3D profilometry, scanning and transmission electron microscopy (SEM/TEM) methods. Finally, the coating’s hardness and heat conductivity were measured. This complex approach allowed to state that PS of micrometric t’-ZrO2 powder having an admixture of m-ZrO2 phase is capable of only partial improvement in its homogenization. However, the suspension PS process of nano-structured powder eliminated any traces of the monoclinic phase from the coating. The TEM microstructure observations indicated that the suspension PS coating is built by in-flight solidified droplets as well as by the melted ones flattened on arrival. A surface layer of liquefied material on solid droplets increases their adhesion to surface asperities promoting pseudo-columnar growth of the coating. The preservation of monotonic slow increase of thermal conductivity during heating of the suspension PS coating means, that its pseudo-columnar microstructure is better suited to withstand high strains during such treatment.

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Thermal barrier coatings manufactured by suspension plasma spraying - a review

Łatka L.

Advances in Materials Science

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2018

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Vol. 18, nr 3(57)

95--117

EN

Thermal barrier coatings (TBC) is one of the most intensively studied of coatings’ applications area. From 1970’s TBC are developed in two independent ways: (i) development in new materials, with lower thermal conductivity, better erosion resistance and better thermal shock resistance or (ii) development in new deposition techniques. On this field besides conventional atmospheric plasma spraying (APS) and almost conventional (because of very common use) EB-PVD method, in the past 20 years two new techniques have been developed, namely suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS). In this paper only SPS method was described, as well as, new materials, which could be used in industrial applications of TBC. Moreover, the key issues, like suspension preparation, type of suspension injection, interaction between liquid droplets and plasma jet and deposition mechanism were described.

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Mikrostruktura powłok Al2O3 natryskanych plazmowo z zawiesin

Żórawski W.

Inżynieria Powierzchni

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2014

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nr 4

19--22

PL

W pracy przedstawiono wyniki badań mikrostruktury powłoki natryskanej plazmowo z zawiesin zawierającej nanometryczne i submikronowe ziarna Al2O3. Natryskana powłoka charakteryzowała się mikrostrukturą bi-modalną, składającą się z obszarów całkowicie przetopionych oraz z obszarów częściowo przetopionych zawierających połączone ze sobą nanoziarna proszku Al2O3.

EN

This paper presented results of microstructure researches of the plasma sprayed coating with application of Al 2O3 powder suspension containing nanometric i submikron grains. The sprayed coating showed a bi-modal structure composed of both fully melted region and partially melted regions included connected nanograins of Al2O3 powder.

4

Warstwy drobnoziarniste otrzymywane metodą natryskiwania plazmowego zawiesin

Tomaszek R., Pawłowski L., Znamirowski Z., Zdanowski J.

Elektronika : konstrukcje, technologie, zastosowania

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2005

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Vol. 46, nr 6

26-27

PL

Przedstawiono wyniki badań mikrostruktury warstw otrzymanych metodą natryskiwania plazmowego zawiesin. Powierzchnię i przekroje warstw analizowano za pomocą skaningowego mikroskopu elektronowego (SEM). Struktura krystaliczna proszku tworzącego zawiesinę oraz produkty transformacji fazowych w warstwie zostały przebadane dyfraktometrem rentgenowskim (XRD).

EN

The paper deals with microstructural characterization of suspension plasma sprayed coatings. Surface and sections of the coatings were investigated using scanning electron microscope (SEM). Crystal structure of initial powder/suspension and resulted phase transformations in coatings were analyzed using X-Ray diffraction.