scholarly journals Effect of Heat Treatment on Microstructure and Thermal Conductivity of Thermal Barrier Coating

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7801
Author(s):  
Kyomin Kim ◽  
Woochul Kim
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Gas Turbines ◽  
Phase Changes ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Continuous Exposure ◽  
X Ray Diffraction ◽  
Barrier Coating ◽  
Before And After

Thermal barrier coatings (TBCs) are essential for increasing the inlet temperature of gas turbines to improve their thermal efficiency. Continuous exposure to flames is known to affect the thermal properties of TBCs, degrading the performance of gas turbines as a consequence. In this study, we quantified the changes in the thermal conductivity of yttria-stabilized zirconia coatings with respect to various heat treatment temperatures and times. The coating exhibited an increase in thermal conductivity after heat treatment, with higher heat treatment temperatures resulting in greater thermal conductivity. The coatings were analyzed by X-ray diffraction and scanning electron microscopy before and after heat treatment. Results showed that there was little change in thermal conductivity due to phase changes and grain size. We conclude that pore structures, i.e., circular and lamellar pores, affected the change in thermal conductivity. Specifically, we confirmed that the change in thermal conductivity depends on the size of the lamellar pores.

Influence of Heat Treatment on Fracture Toughness and Wear Resistance of Nicral-Zro2 Multilayered Thermal Barrier Coating

2018 ◽  
Vol 37 (5) ◽  
pp. 463-475
Author(s):  
Zibo Ye ◽  
Guanghong Wang
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Wear Resistance ◽  
Xrd Analysis ◽  
Thermal Barrier ◽  
Homogeneous Microstructure ◽  
Barrier Coating ◽  
Before And After ◽  
T Phase ◽  
The Relationship

AbstractThe chemical composition and fracture toughness of thermal barrier coatings (TBCs) before and after heat treatment were characterized, and the cracks around the interface between the coating and the substrate could be successfully eliminated and meanwhile the porosity of the coatings tended to reduce. The XRD analysis revealed the coatings were composed of non-transformable tetragonal t’ phase of ZrO2 and $\gamma $-(Ni, Cr) with minor Ni3Al ($\gamma ^' $) precipitates. Additionally, the relationship between the heat treatment and wear resistance was systematically studied. The results indicated that both the hardness and fracture toughness increased after quenching process. The oxidation wear became more prominent after heat treatment, which probably resulted from the better bonding strength of coatings. Dense and homogeneous microstructure introduced by vacuum oil-quenching improved stabilization of the weight gain during thermal cycle test.

Thermal Properties and Phase Analysis of Titania Doped Yttria-Zirconia Ceramics for Use as High Temperature Thermal Barrier Coatings (TBCs)

2011 ◽  
Author(s):  
L. J. Romualdez ◽  
M. Kibsey ◽  
X. Huang ◽  
R. Kearsey
Keyword(s):  
Thermal Conductivity ◽  
Phase Analysis ◽  
Primary Objective ◽  
Thermal Barrier ◽  
X Ray Diffraction ◽  
Calorimetric Analysis ◽  
Barrier Coating ◽  
Specific Heat Capacities ◽  
Thermal Diffusivities ◽  
Thermal Conductivities

Titania doped YSZ ceramic samples were subjected to calorimetric, thermal and microstructural analyses to assess the value of titania as a dopant for use as thermal barrier coating in modern gas turbine engines. The primary objective of titania addition was to effectively stabilize the tetragonal phase at operating temperatures while lowering the thermal conductivity. Powder blends with 5, 10, and 15 wt% titania added to standard 7YSZ powder were sintered at 1200°C for 325hrs after plasma spraying. Basic physical properties related to the thermal conductivity of the material such as bulk densities and Young’s modulus were determined. Phase analysis of all samples was performed using x-ray diffraction techniques so the percentage of monoclinic, tetragonal, and cubic phases could be determined. For all titania samples, it was shown that the composition was predominantly tetragonal with slightly decreasing amounts of monoclinic phases present with increasing titania content. The results of calorimetric analysis showed a marginal decrease in the specific heat capacities of the sintered titania doped samples. Similarly, thermal diffusivities were lowered by the addition of titania, though only slightly, since it has been previously shown that diffusivity is more strongly linked to sample porosity. Using these results, the experimental thermal conductivities for all titania doped samples were determined and compared to theoretical conductivities based solely on the mechanical properties of the ceramic. The results showed a decrease in thermal conductivity with the addition of titania, though with higher values than that predicted from the theoretical model. Experimental thermal conductivities were also shown to decrease with temperature initially, while increasing slightly at higher temperatures, which is most probably due to the radiation effect.

Structure and Thermal Conductivity of Nanostructured Hafnia-Based Thermal Barrier Coating Grown on SS-403

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
M. Noor-A-Alam ◽  
A. R. Choudhuri ◽  
C. V. Ramana
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Grazing Incidence ◽  
Thermal Barrier ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Eds Analysis ◽  
Barrier Coating

Yttria-stabilized hafnia (YSH) coatings were grown onto stainless steel 403 (SS-403) and Si substrates. The deposition was made at various growth temperatures ranging from room temperature (RT) to 500 °C. The microstructure and thermal properties of the YSH coatings were evaluated employing grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and photoacoustic measurements. GIXRD studies indicate that the coatings crystalize in cubic structure with a (111) texturing. Well-grown triangular dense morphology was evident in SEM data. EDS analysis indicates the composition stability of YSH coatings. The grain size increases with the increasing growth temperature. Thermal conductivity measurements indicate lower thermal conductivity of YSH coatings compared to either pure hafnia or yttria-stabilized zirconia.

scholarly journals A Combustor Can With 1.8 mm Thick Plasma Sprayed Thermal Barrier Coating

1998 ◽  
Author(s):  
Jan Wigren ◽  
Jens Dahlin ◽  
Mats-Olov Hansson
Keyword(s):  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Current State ◽  
Barrier Coating ◽  
Component Test ◽  
Before And After ◽  
Plasma Sprayed ◽  
Cooling Air

The benefits of thermal barrier coatings for protection of combustor walls are well known. However, the trend to higher combustor inlet temperatures and the reduced availability of cooling air leads to a demand for better insulation performance from the thermal barrier coating (TBC). This is of particular benefit for low emission combustors where wall quenching effects need to be minimised and often hot side cooling is not permissible. A combustor can, for advanced stationary gas turbines, with 1.8 mm thick thermal barrier was designed and tested. The can was compared to a combustor can with a thermal barrier coating sprayed with current state-of-the-art methods, but to the same thickness. Steps to optimise performance were taken in all development stages. The design allowed easy spray geometries, improved edges and no film cooling. Spraying was optimised in order to achieve a segmented microstructure for reduction of stresses (by decrease of the Young’s Modulus in the coating) and increase compliance of the coating. Testing in component test rigs showed excellent results. The lifetime of the optimised combustor can was beyond test capabilities, whereas the reference combustor failed immediately. Metallographic and X-ray characterisation before and after component rig testing was performed and revealed features that explain the superiority of the segmented thermal barrier coating. This work has been funded by the CEC under the contract BRE-CT94-0936.

scholarly journals COMPUTATIONAL EVALUATION OF THERMAL BARRIER COATINGS

2019 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Numerical Study ◽  
Combined Cycle ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Barrier Coatings

In the power plant industry, the turbine inlet temperature (TIT) plays a key role in the efficiency of the gas turbine and, therefore, the overall—in most cases combined—thermal power cycle efficiency. Gas turbine efficiency increases by increasing TIT. However, an increase of TIT would increase the turbine component temperature which can be critical (e.g., hot gas attack). Thermal barrier coatings (TBCs)—porous media coatings—can avoid this case and protect the surface of the turbine blade. This combination of TBC and film cooling produces a better cooling performance than conventional cooling processes. The effective thermal conductivity of this composite is highly important in the design and other thermal/structural assessments. In this article, the effective thermal conductivity of a simplified model of TBC is evaluated. This work details a numerical study on the steady-state thermal response of two-phase porous media in two dimensions using personal finite element analysis (FEA) code. Specifically, the system response quantity (SRQ) under investigation is the dimensionless effective thermal conductivity of the domain. A thermally conductive matrix domain is modeled with a thermally conductive circular pore arranged in a uniform packing configuration. Both the pore size and the pore thermal conductivity are varied over a range of values to investigate the relative effects on the SRQ. In this investigation, an emphasis is placed on using code and solution verification techniques to evaluate the obtained results. The method of manufactured solutions (MMS) was used to perform code verification for the study, showing the FEA code to be second-order accurate. Solution verification was performed using the grid convergence index (GCI) approach with the global deviation uncertainty estimator on a series of five systematically refined meshes for each porosity and thermal conductivity model configuration. A comparison of the SRQs across all domain configurations is made, including uncertainty derived through the GCI analysis.References: [1] Ibrahim, T. K. and Rahman, M. M., 2013, “Study on effective parameter of the triple-pressure reheat combined cycle performance,” Thermal Science, 17(2), pp. 497-508. [2] Nayak, J. and Mahto, D., 2014, “Effect of Gas Turbine Inlet Temperature on Combined Cycle Performance,” International Conference on Recent Innovations in Engineering & Technology. [3] Fathi, N., McDaniel, P., Forsberg, C., and de Oliveira, C., 2018, "Power Cycle Assessment of Nuclear Systems, Providing Energy Storage for Low Carbon Grids," Journal of Nuclear Engineering and Radiation Science, 4(2), 020911. [4] Fathi, Nima, Patrick McDaniel, Charles Forsberg, and Cassiano de Oliveira. "Nuclear Systems for a Low Carbon Electrical Grid." In 2016 24th International Conference on Nuclear Engineering, pp. V001T03A007-V001T03A007. American Society of Mechanical Engineers, 2016. [5] Hunter, I., Daleo, J., Wilson, J., and Ellison, K., 1999, “Analysis of Hot Section Failures on Gas Turbines in Process Plant Service,” Proceedings of the 28th Turbomachinery Symposium, 28, pp. 9-20. [6] Zohuri, Bahman, and Nima Fathi. "Thermal-Hydraulic Analysis of Nuclear Reactors." [7] Salehnasab, B., Poursaeidi, E., Mortazavi, S. A., and Farokhian, G. H, 2016, “Hot corrosion failure in the first stage nozzle of a gas turbine engine,” Engineering Failure Analysis, 60, pp. 316-325. [8] Rechard, Robert P., Teklu Hadgu, Yifeng Wang, Lawrence C. Sanchez, Patrick McDaniel, Corey Skinner, and Nima Fathi. Technical Feasibility of Direct Disposal of Electrorefiner Salt Waste. No. SAND2017-10554. Sandia National Lab.(SNLNM), Albuquerque, NM (United States), 2017. [9] Rechard, Rob P., Teklu Hadgu, Yifeng Wang, Larry C. Sanchez, Patrick McDaniel, Corey Skinner, Nima Fathi, Steven Frank, and Michael Patterson. "Feasibility of Direct Disposal of Salt Waste from Electochemical Processing of Spent Nuclear Fuel." arXiv preprint arXiv:1710.00855 (2017). [10] Lai, G. Y., 2007, High-Temperature Corrosion and Materials Applications, ASM International, Novelty, OH. [11] Rao, A. D, 2012, Combined Cycle Systems for Near-Zero Emission Power Generation, Woodhead Publishing Limited, Cambridge, UK.  [12] Ma, W., Li, X., Meng, X, Xue, Y, Bai, Y, Chen, W., and Dong, 2018, “Microstructure and Thermophysical Properties of SrZrO3 Thermal Barrier Coating Prepared by Solution Precursor Plasma Spray,” Journal of Thermal Spray Technology, 27(7), pp. 1056-1063. [13] McCay, M. H., Hsu, P.-f., Croy, D. E., Moreno, D., and Zhang, M., 2017, “The Fabrication, High Heat Flux Testing, and Failure Analysis of Thermal Barrier Coatings for Power Generation Gas Turbines,” Turbo Expo: Power for Land, Sea, and Air, 6():V006T24A008. [15] Irick, Kevin, and Nima Fathi. "Thermal Response of Open-Cell Porous Materials: A Numerical Study and Model Assessment." In ASME 2018 Verification and Validation Symposium, pp. V001T03A002-V001T03A002. American Society of Mechanical Engineers, 2018.

scholarly journals Progress in Novel Electrodeposited Bond Coats for Thermal Barrier Coating Systems

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4214
Author(s):  
Kranthi Kumar Maniam ◽  
Shiladitya Paul
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coating ◽  
Gas Turbines ◽  
High Performance ◽  
Turbine Engines ◽  
Thermal Barrier ◽  
Gas Turbine Engines ◽  
Potential Cost ◽  
Bond Coats ◽  
Barrier Coating

The increased demand for high performance gas turbine engines has resulted in a continuous search for new base materials and coatings. With the significant developments in nickel-based superalloys, the quest for developments related to thermal barrier coating (TBC) systems is increasing rapidly and is considered a key area of research. Of key importance are the processing routes that can provide the required coating properties when applied on engine components with complex shapes, such as turbine vanes, blades, etc. Despite significant research and development in the coating systems, the scope of electrodeposition as a potential alternative to the conventional methods of producing bond coats has only been realised to a limited extent. Additionally, their effectiveness in prolonging the alloys’ lifetime is not well understood. This review summarises the work on electrodeposition as a coating development method for application in high temperature alloys for gas turbine engines and discusses the progress in the coatings that combine electrodeposition and other processes to achieve desired bond coats. The overall aim of this review is to emphasise the role of electrodeposition as a potential cost-effective alternative to produce bond coats. Besides, the developments in the electrodeposition of aluminium from ionic liquids for potential applications in gas turbines and the nuclear sector, as well as cost considerations and future challenges, are reviewed with the crucial raw materials’ current and future savings scenarios in mind.

scholarly journals Research on Thermal Stability and Properties of Ca3ZrSi2O9 as Potential T/EBC Materials

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 583
Author(s):  
Yangyang Pan ◽  
Bo Liang ◽  
Yaran Niu ◽  
Dijuan Han ◽  
Dongdong Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Fracture Toughness ◽  
Room Temperature ◽  
Coefficient Of Thermal Expansion ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Mechanical And Thermal Properties ◽  
Self Healing ◽  
Barrier Coating

In this study, a new coating material for thermal barrier coating (TBC) or environment barrier coating (EBC) application, Ca3ZrSi2O9 (CZSO), was synthesized and prepared by atmospheric plasma spray (APS) technology. The evolution of the phases and microstructures of the coatings with different thermal-aged were characterized by XRD, XRF, EDS and SEM, respectively. The thermal stability was measured by TG-DTA and DSC. The mechanical and thermal properties, including Vickers hardness (HV), fracture toughness (KIC), thermal conductivity () and coefficient of thermal expansion (CTE) were focused on. It was found that the as-sprayed CZSO coating contained amorphous phase. Crystalline transformation happened at 900–960 ∘C and no mass changes took place from room temperature (RT) to 1300 ∘C. The phenomena of microcrack self-healing and composition uniformity were observed during thermal aging. The of coating was very low at about 0.57–0.80 Wm−1K−1 in 200–1200 ∘C. The combined properties indicated that the CZSO coating might be a potential T/EBC material.

The Study of Thermal Properties and Micro Structures of YSZ

2007 ◽  
Author(s):  
S. M. Guo ◽  
M. B. Silva ◽  
Patrick F. Mensah ◽  
Nalini Uppu
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Gas Turbine ◽  
Bond Coat ◽  
Sintering Temperature ◽  
Heating Process ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Low Thermal Conductivity ◽  
Gas Tight

Thermal barrier coatings (TBCs) are used in gas turbine engines to achieve a better efficiency by allowing increased turbine inlet temperature and decreasing the amount of cooling air used. Plasma spraying is one of the most reliable methods to produce TBCs, which are generally comprised of a top coating of ceramic and a bond-coat of metal. Usually, the top coating is Yttria-Stabilized-Zirconia (YSZ), providing the thermal barrier effect. The bond-coat is typically a layer of M-Cr-Al-Y (where “M” stands for “metal”), employed to improve the attachment between the ceramic top-coat and the substrate. Due to the extreme temperature gradient presented in the plasma jet and the wide particle size distribution, during the coating process, injected ceramic powders may experience a significantly different heating process. Different heating history, coupled with the substrate preheating temperature, may affect the thermal properties of the YSZ layers. In this paper, four sets of mol 8% YSZ disks are fabricated under controlled temperatures of 1100°C, 1200°C, 1400°C and 1600°C. Subsequently the thermal properties and the microstructures of these YSZ disks are studied. The results indicate a strong microstructure change at a temperature slightly below 1400°C. For a high sintering temperature, a dense YSZ layer can be formed, which is good for gas tight operation; At low sintering temperature, say 1200°C, a porous YSZ layer is formed, which has the advantage of low thermal conductivity. For gas turbine TBC applications, a robust low thermal conductivity YSZ layer is desirable, while for Solid Oxide Fuel Cells, a gas-tight YSZ film must be formed. This study offers a general guideline on how to prepare YSZ layers, mainly by controlling the heating process, to form microstructures with desired properties.

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