Fracture Toughness of Thermal Spray Ceramics: Measurement Techniques and Processing Dependence

Smith, Gregory M.; Smith, A. G. R.; Sampath, Sanjay

doi:10.1007/s11666-018-0755-6

Cited by 11 publications

(4 citation statements)

References 46 publications

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“…From the figure, it seems the crack propagation follows a tortuous path along intersplat boundaries. Similar microstructural features have been reported for such top‐down fracture of plasma‐sprayed ceramics in other literature 67,68 …”

Section: Resultssupporting

confidence: 87%

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Laser thermal gradient testing of air plasma sprayed multilayered, multi‐material thermal barrier coatings

Wang

GildersleeveV³

et al. 2022

Int J Applied Ceramic Tech

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Air plasma sprayed (APS) thermal barrier coatings (TBCs) are a widely used technology in the gas turbine industry to thermally insulate and protect underlying metallic superalloy components. These TBCs are designed to have intrinsically low thermal conductivity while also being structurally compliant to withstand cyclic thermal excursions in a turbine environment. This study examines yttria-stabilized zirconia (YSZ) TBCs of varying architecture: porous and dense vertically cracked (DVC), which were deposited onto bond-coated superalloys and tested in a novel CO 2 laser rig. Additionally, multilayered TBCs: a two-layered YSZ (dense + porous) and a multi-material YSZ/GZO TBC were evaluated using the same laser rig. Cyclic exposure under simulative thermal gradients was carried out using the laser rig to evaluate the microstructural change of these different TBCs over time. During the test, real-time calculations of the normalized thermal conductivity of the TBCs were also evaluated to elucidate information about the nature of the microstructural change in relation to the starting microstructure and composition. It was determined that porous TBCs undergo steady increases in conductivity, whereas DVC and YSZ/GZO systems experience an initial increase followed by a monotonic decrease in conductivity.Microstructural studies confirmed the difference in coating evolution due to the cycling.

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Section: Resultssupporting

confidence: 87%

“…Similar microstructural features have been reported for such top-down fracture of plasma-sprayed ceramics in other literature. 67,68 Figure 9 shows the bilayered 7YSZ TBC (Specimen B) before and after thermal gradient cycling. The microstructural features between the bilayered TBC and the standard porous TBC are similar.…”

Section: 21mentioning

confidence: 99%

Laser thermal gradient testing of air plasma sprayed multilayered, multi‐material thermal barrier coatings

Wang

GildersleeveV³

et al. 2022

Int J Applied Ceramic Tech

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“…Thermal-sprayed metal coatings are used in applications such as airplane wings and turbines [8] and have been considered for the linings of nuclear fusion reactors [9]. A precise understanding of structure informs understanding of structural properties and predictions of performance in environments including these high-mechanical-stress and thermal environments.…”

Section: Thermal-sprayed Coatingsmentioning

confidence: 99%

Automated segmentation of porous thermal spray material CT scans with predictive uncertainty estimation

et al. 2023

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Thermal sprayed metal coatings are used in many industrial applications, and characterizing the structure and performance of these materials is vital to understanding their behavior in the field. X-ray computed tomography (CT) enables volumetric, nondestructive imaging of these materials, but precise segmentation of this grayscale image data into discrete material phases is necessary to calculate quantities of interest related to material structure. In this work, we present a methodology to automate the CT segmentation process as well as quantify uncertainty in segmentations via deep learning. Neural networks (NNs) have been shown to excel at segmentation tasks; however, memory constraints, class imbalance, and lack of sufficient training data often prohibit their deployment in high resolution volumetric domains. Our 3D convolutional NN implementation mitigates these challenges and accurately segments full resolution CT scans of thermal sprayed materials with maps of uncertainty that conservatively bound the predicted geometry. These bounds are propagated through calculations of material properties such as porosity that may provide an understanding of anticipated behavior in the field.

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“…Such free-standing coatings allow measurements of properties that are difficult or rather impossible to determine with a substrate underneath. These measurements can be mechanical tests, e.g., for the evaluation of Young's modulus [1], bending strength [2], creep [3,4] or sintering properties [5][6][7], toughness [8], and crack propagation [9,10]. Additionally, functional properties like thermal diffusivity [11], optical properties [12], phase evolution [13], and attack by corrosive species as Calcium-Magnesium-Aluminum-Silicate (CMAS, [14]) are measured on free-standing coatings.…”

Section: Introductionmentioning

confidence: 99%

Influence of Substrate Removal Method on the Properties of Free-Standing YSZ Coatings

2021

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Thermally sprayed ceramic coatings are often tested as free-standing layers to investigate different properties such as thermal expansion coefficient, thermal conductivity, sintering, mechanical behavior, corrosion resistance, gas tightness, or electrical properties. In this paper, four different substrate removal methods were used to obtain free-standing YSZ coatings. At first, spraying on a steel substrate and subsequent dissolution of the substrate-coating interface by hydrochloric acid (HCl) was used. Second, the steel substrate was removed by applying an electrical field via electrochemical corrosion of the surface of the substrate. In a third method, the coating was sprayed on a salt (NaCI) interlayer, which was removed later by dissolution in water. At last, the coating was sprayed on a graphite substrate and the substrate was removed by heat treatment. After the preparation of free-standing coatings, these were characterized using scanning electron microscopy, mercury porosimetry, indentation tests, and room temperature three-point bending tests, which allowed the determination of Young’s modulus and viscosity. The results revealed measurable differences in coating properties as a result of the substrate removal methods, i.e., HCl method led to higher porosity and lower modulus in the YSZ coating.

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Fracture Toughness of Thermal Spray Ceramics: Measurement Techniques and Processing Dependence

Cited by 11 publications

References 46 publications

Laser thermal gradient testing of air plasma sprayed multilayered, multi‐material thermal barrier coatings

Laser thermal gradient testing of air plasma sprayed multilayered, multi‐material thermal barrier coatings

Automated segmentation of porous thermal spray material CT scans with predictive uncertainty estimation

Influence of Substrate Removal Method on the Properties of Free-Standing YSZ Coatings

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