Plasma-Sprayed Thermal Barrier Coatings with Enhanced Splat Bonding for CMAS and Corrosion Protection

Liu, Tao; Yao, Shuwei; Wang, Li-Shuang; Yang, Guan-Jun

doi:10.1007/s11666-015-0345-9

Cited by 34 publications

(13 citation statements)

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“…Third, bubbles are observed in the upper zones of CMAS on Pellet32 and Pellet77, whereas such bubbles can hardly be observed in CMAS on Pellet6 and Pellet13. The interaction between YSZ and CMAS has been investigated by many researchers, but no evidence shows that gas phase can be released during their interaction . Therefore, these bubbles occur in the upper zones of CMAS presumably due to the upward migrations of the relatively large unfilled PMMA pores (with relatively large buoyancy) in the CMAS‐infiltrated zones (see higher‐magnification SEM images in Figure ) in Pellet32 and 77.…”

Section: Resultsmentioning

confidence: 99%

“…This kind of approach causes the crystallization of CMAS and the attendant arrest of the infiltrating CMAS front. Besides, some researchers tried to modify structures of TBCs to mitigate CMAS . For example, Liu et al fabricated a dense layer on the top of atmospheric plasma spray (APS) TBCs by alerting the processing parameters; they demonstrated that the dense layer can effectively suppress CMAS infiltration.…”

Section: Introductionmentioning

confidence: 99%

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Pore filling behavior of YSZ under CMAS attack: Implications for designing corrosion‐resistant thermal barrier coatings

et al. 2018

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To understand the pore filling behavior in thermal barrier coatings during calcium‐magnesium‐alumino‐silicate (CMAS) infiltration process, porous yttria‐stabilized zirconia pellets with different sizes of spherical pores were prepared to simulate thermal barrier coatings. The pores (D50 ranging from 6 to 77 μm) were introduced to the pellets using poly methyl methacrylate as pore forming agents. Then the pellets were sintered to remove the pore forming agents and to achieve a similar volume fraction of porosity with thermal barrier coatings. After CMAS infiltration, only some small pores in the CMAS‐infiltrated zones were filled by CMAS, whereas all large pores (larger than 13 μm) remained unfilled; besides, the results also show that even open pores can resist filling by CMAS. The reason may relate to pore diameters; if the diameter of a pore is relatively large, the pore surface will not be completely wetted by liquid CMAS, the liquid meniscus will be discontinuous, and therefore the pore cannot be filled. The key insight gained from this study is that introducing “CMAS‐proof” pores into thermal barrier coatings may be a potential way to mitigate CMAS damage.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pore filling behavior of YSZ under CMAS attack: Implications for designing corrosion‐resistant thermal barrier coatings

et al. 2018

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“…For gas turbines operating above 1200 o C, failure can occur by the deposits of calciummagnesium-aluminum-silicate, referred to as CMAS [66][67][68][69]. CMAS deposits on the turbine components are more likely to occur in gas turbines operating in areas close to the deserts.…”

Section: Cmas Corrosionmentioning

confidence: 99%

Failure mechanisms in APS and SPS thermal barrier coatings during cyclic oxidation and hot corrosion

Jonnalagadda¹

2017

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Linköping 2017Front page image: The top view of yttria stabilized zirconia thermal barrier coating after exposure to a salt mixture of vanadium pentoxide and sodium sulfate at 900 o C.During the course of research underlying this thesis, Krishna Praveen Jonnalagadda was enrolled in Agora Materiae, a multidisciplinary doctoral program at Linköping University, Sweden.ISBN: 978-91-7685-594-2 ISSN: 0280-7971Printed by LiU-Tryck 2017 iii AbstractThermal Barrier Coatings (TBCs) are advanced material systems that are being used in the hot sections of gas turbines such as combustor, turbine blades, and vanes. The top ceramic coating in TBCs provides insulation against the hot gases and the intermediate metallic bond coat provides oxidation and corrosion resistance to the underlying turbine components.Durability of thermal barrier coatings is very important for the overall performance of the gas turbine. TBCs can fail in several different ways and there is a combination of more than one failure mechanism in most situations. One of the most widely used TBC is atmospheric plasma sprayed (APS) yttria stabilized zirconia (YSZ). Both the deposition technique and the TBC material have certain limitations. The main aim of this research is to study new TBC materials and/or new deposition techniques and compare with the conventional YSZ and understand their failure mechanisms during cyclic oxidation and hot corrosion.Thermal cyclic oxidation of a newly developed high purity nano YSZ thermal barrier coating has been studied. Cross sectional analysis of exposed as well as completely failed samples showed a mixed-type failure caused by crack propagation parallel to the bond coat/top coat interface. The majority of the damage occurred towards the end of the coating life. A finite element model has been developed to study the probability of crack growth along different paths that leads to the final failure.Hot corrosion mechanism in suspension plasma sprayed two-layer gadolinium zirconate/YSZ, three-layer dense gadolinium zirconate/gadolinium zirconate/YSZ, and a single-layer YSZ has been studied in the presence of sodium sulfate and vanadium pentoxide. The test results showed that gadolinium zirconate coatings were more susceptible to corrosion compared to YSZ coatings despite gadolinium zirconate coatings having lower reactivity with the corrosive salts.Thermal cycling behavior of a high chromium bond coat has been studied. Cross-sectional analysis showed formation of sandwich type microstructure with chromium rich oxide and alumina as the top and the bottom layers.Inter-diffusion of minor elements between different MCrAlY coatings -substrate systems has been studied using, diffusion simulation software, DICTRA. The simulation results showed that the diffusion of minor elements in the coatings is dependent on the rate of β phase depletion in the beginning. After the depletion of β phase there was no clear dependence of the coating composition on the diffusion of minor elements.v SammanfattningTermiska barriärskikt, eller TBC från...

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“…Additive processes include deposition methods, such as physical vapor deposition [5][6][7], laser technology [8], thermal spray [9,10] and electrochemical deposition [11][12][13], to name a few. Among them, galvanic electrodeposition is scientifically recognized as a mature technology and one of the most effective, as well as low-cost, in industrial sectors worldwide.…”

Section: Introductionmentioning

confidence: 99%

Electroplating for Decorative Applications: Recent Trends in Research and Development

et al. 2018

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Electroplating processes are widely employed in industrial environments for a large variety of metallic coatings, ranging from technological to decorative applications. Even if the galvanic electrodeposition is certainly a mature technology, new concepts, novel applications, environmental legislation and the new material requirements for next-generation devices make the scientific research in this field still very active. This review focuses mostly at the decorative and wearable applications, and aims to create a bridge between the past knowledge and the future direction that this process, i.e., electrodeposition, is taking. Both the theoretical fundamentals as well as some of the most widespread practical applications-limited to metallic and alloy coatings-are explored. As an integral part of the industrial process, we take a look at the main techniques thought which the quality control of deposits and surfaces is carried out. Finally, global industrial performance and research directions towards sustainable solutions are highlighted.

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Plasma-Sprayed Thermal Barrier Coatings with Enhanced Splat Bonding for CMAS and Corrosion Protection

Cited by 34 publications

References 31 publications

Pore filling behavior of YSZ under CMAS attack: Implications for designing corrosion‐resistant thermal barrier coatings

Pore filling behavior of YSZ under CMAS attack: Implications for designing corrosion‐resistant thermal barrier coatings

Failure mechanisms in APS and SPS thermal barrier coatings during cyclic oxidation and hot corrosion

Electroplating for Decorative Applications: Recent Trends in Research and Development

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