Effect of ageing on microstructure changes in EB-PVD manufactured standard PYSZ top coat of thermal barrier coatings

Renteria, A. Flores; Saruhan, Bilge

doi:10.1016/j.jeurceramsoc.2005.04.027

Cited by 56 publications

(26 citation statements)

References 29 publications

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“…In general, these changes tend to cause reduced thermal insulation capacity [16][17][18]78] and reduced strain tolerance [19-21, 26, 79, 80], both of which are highly undesirable. It's also clear that sintering can be accelerated by the presence of species that become concentrated in grain boundaries or at free surfaces, whether present as impurities in the coatings [31] or as material absorbed during turbine operation [27][28][29][30].…”

Section: Sintering In Tbcsmentioning

confidence: 99%

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Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

2009

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A review is presented of how heat transfer takes place in plasma sprayed (zirconia-based) thermal barrier coatings (TBCs) during operation of gas turbines. These characteristics of TBCs are naturally of central importance to their function. Current state-of-the-art TBCs have relatively high levels of porosity (~15%) and the pore architecture (ie its morphology, connectivity and scale) has a strong influence on the heat flow. Contributions from convective, conductive and radiative heat transfer are considered, under a range of operating conditions, and the characteristics are illustrated with experimental data and modelling predictions. In fact, convective heat flow within TBCs usually makes a negligible contribution to the overall heat transfer through the coating, although what might be described as convection can be important if there are gross through-thickness defects such as segmentation cracks. Radiative heat transfer, on the other hand, can be significant within TBCs, depending on temperature and radiation scattering lengths, which in turn are sensitive to the grain structure and the pore architecture. Under most conditions of current interest, conductive heat transfer is largely predominant. However, it is not only conduction through solid ceramic that is important. Depending on the pore architecture, conduction through gas in the pores can play a significant role, particularly at the high gas pressures typically acting in gas turbines (although rarely applied in laboratory measurements of conductivity). The durability of the pore structure under service conditions is also of importance, and this review covers some recent work on how the pore architecture, and hence the conductivity, is affected by sintering phenomena. Some information is presented concerning the areas in which research and development work needs to be focussed if improvements in coating performance are to be achieved.

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Section: Sintering In Tbcsmentioning

confidence: 99%

“…Consequently increased through-thickness thermal conductivity [16][17][18] has been widely reported, and correlated with growth of the inter-splat contact area [7,15]. It's also clear that grain growth, and associated reduction in the scattering of radiation, can contribute to increased heat transfer.…”

Section: Introductionmentioning

confidence: 98%

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

2009

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“…3),4) EB-PVD technique for TBCs processing is widely studied, such as the ageing effect on microstructure changes, 5) the influence of microstructure of thermal conductivity, 6) layed TBCs with multiple interfaces 7) and low thermal conductivity by dopant atoms.…”

Section: Introductionmentioning

confidence: 99%

Degradation of EB-PVD ZrO2–4 mol%Y2O3 thermal barrier coatings by volcanic ash deposits

Jang

Kim

et al. 2016

J. Ceram. Soc. Japan

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This work describes the degradation of ZrO 2 4 mol%Y 2 O 3 (YSZ) coatings obtained by EB-PVD. YSZ coatings were exposed at 1200°C for 10 min50 hr by isothermal heat treatment in the presence of an erosive impurity of volcanic ash. At the interface between the YSZ coatings and volcanic ash, the coatings were partially dissolved in the volcanic ash, resulting in the degradation of coatings by the formation of the reacted region. A ZrSiO 4 or glassy phase is formed by the chemical reaction between YSZ coatings and volcanic ash at 1200°C. The chemically reacted region from the top surface of the YSZ coatings showed a tendency for increased degradation depth with an increase in isothermal heat-treatment time.

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“…After heat treatment at 1100°C for 100 hours, the sintering process becomes active, leading to morphological changes at all pore types 3 . Mass transfer occurs through bridging at the contact points between primary columns forming two dimensional groups of inter-columnar pores.…”

Section: Resultsmentioning

confidence: 99%

“…These may be due to the occurrence of a series of thermal processes varying from formation of bridges between the columns, formation of sintering necks at contact points between the featherarms, and eventually changes in pore geometry and sizes of the intra-columnar pores 2 . All these thermally activated processes generate surface area reduction and may follow in a similar way as the sintering processes 3 . Previous studies [4][5][6] indicate that the microstructural configuration of the EB-PVD PYSZ TBCs significantly contribute to the intrinsic thermal properties of the material.…”

Section: Introductionmentioning

confidence: 99%

Relation of Thermal Conductivity with Process Induced Anisotropic Void Systems in EB-PVD PYSZ Thermal Barrier Coatings

Renteria

Saruhan

Ilavský

Ceramic Engineering and Science Proceedings

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Thermal barrier coatings (TBCs) deposited by Electron-beam physical deposition (EB-PVD) protect the turbine blades situated at the high pressure sector of the aircraft and stationary turbines. It is an important task to uphold low thermal conductivity in TBCs during long-term service at elevated temperatures. One of the most promising methods to fulfil this task is to optimize the properties of PYSZ-based TBC by tailoring its microstructure. Thermal conductivity of the EB-PVD produced PYSZ TBCs is influenced mainly by the size, shape, orientation and volume of the various types of porosity present in the coatings. These pores can be classified as open (inter-columnar and between feather arms gaps) and closed (intra-columnar pores). Since such pores are located within the three-dimensionally deposited columns and enclose large differences in their sizes, shapes, distribution and anisotropy, the accessibility for their characterization is very complex and requires the use of sophisticated methods. In this work, three different EB-PVD TBC microstructures were manufactured by varying the process parameters, yielding various characteristics of their pores. The corresponding thermal conductivities in as-coated state and after ageing at 1100C/1h and 100h were measured via Laser Flash Analysis Method (LFA). The pore characteristics and their individual effect on the thermal conductivity are analysed by USAXS which is supported by subsequent modelling and LFA methods, respectively. Evident differences in the thermal conductivity values of each microstructure were found in as-coated and aged conditions. In summary, broader columns introduce higher values in thermal conductivity. In general, thermal conductivity increases after ageing for all three investigated microstructures, although those with initial smaller pore surface area show smaller changes.

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Effect of ageing on microstructure changes in EB-PVD manufactured standard PYSZ top coat of thermal barrier coatings

Cited by 56 publications

References 29 publications

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

Degradation of EB-PVD ZrO<sub>2</sub>–4 mol%Y<sub>2</sub>O<sub>3</sub> thermal barrier coatings by volcanic ash deposits

Relation of Thermal Conductivity with Process Induced Anisotropic Void Systems in EB-PVD PYSZ Thermal Barrier Coatings

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Effect of ageing on microstructure changes in EB-PVD manufactured standard PYSZ top coat of thermal barrier coatings

Cited by 56 publications

References 29 publications

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

Degradation of EB-PVD ZrO<sub>2</sub>&ndash;4 mol%Y<sub>2</sub>O<sub>3</sub> thermal barrier coatings by volcanic ash deposits

Relation of Thermal Conductivity with Process Induced Anisotropic Void Systems in EB-PVD PYSZ Thermal Barrier Coatings

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Product

Resources

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Degradation of EB-PVD ZrO<sub>2</sub>–4 mol%Y<sub>2</sub>O<sub>3</sub> thermal barrier coatings by volcanic ash deposits