Optical Nondestructive Condition Monitoring of Thermal Barrier Coatings

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
A. L. Heyes ◽  
J. P. Feist ◽  
X. Chen ◽  
Z. Mutasim ◽  
J. R. Nicholls
Keyword(s):  
Rare Earth ◽  
Thermal Barrier Coatings ◽  
Condition Monitoring ◽  
Gas Turbines ◽  
Thermal Protection ◽  
Uv Light ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Calibration Data ◽  
Barrier Coatings

This paper describes recent developments of the thermal barrier sensor concept for nondestructive evaluation (NDE) of thermal barrier coatings (TBCs) and online condition monitoring in gas turbines. Increases in turbine inlet temperature in the pursuit of higher efficiency will make it necessary to improve or upgrade current thermal protection systems in gas turbines. As these become critical to safe operation, it will also be necessary to devise techniques for online condition monitoring and NDE. The authors have proposed thermal barrier sensor coatings (TBSCs) as a possible means of achieving NDE for TBCs. TBSCs are made by doping the ceramic material (currently yttria-stabilized zirconia (YSZ)) with a rare-earth activator to provide the coating with luminescence when excited with UV light. This paper describes the physics of the thermoluminescent response of such coatings and shows how this can be used to measure temperature. Calibration data are presented along with the results of comparative thermal cycle testing of TBSCs, produced using a production standard air plasma spray system. The latter show the durability of TBSCs to be similar to that of standard YSZ TBCs and indicate that the addition of the rare-earth dopant is not detrimental to the coating. Also discussed is the manufacture of functionally structured coatings with discreet doped layers. The temperature at the bond coat interface is important with respect to the life of the coating since it influences the growth rate of the thermally grown oxide layer, which in turn destabilizes the coating system as it becomes thicker. Experimental data are presented, indicating that dual-layered TBSCs can be used to detect luminescence from, and thereby the temperature within, subsurface layers covered by as much as 500 μm of standard TBC material. A theoretical analysis of the data has allowed some preliminary calculations of the transmission properties of the overcoat to be made, and these suggest that it might be possible to observe phosphorescence and measure temperature through an overcoat layer of up to approximately 1.56 mm thickness.

Optical Non-Destructive Condition Monitoring of TBC’s

2007 ◽  
Author(s):  
A. L. Heyes ◽  
J. P. Feist ◽  
X. Chen ◽  
Z. Mutasim ◽  
J. R. Nicholls
Keyword(s):  
Rare Earth ◽  
Thermal Barrier Coatings ◽  
Condition Monitoring ◽  
Gas Turbines ◽  
Thermal Protection ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Calibration Data ◽  
Barrier Coatings ◽  
Non Destructive

The paper describes recent developments of the thermal barrier sensor concept for non-destructive evaluation (NDE) of thermal barrier coatings and on-line condition monitoring in gas turbines. Increases in turbine inlet temperature in pursuit of higher efficiency will make it necessary improve or upgrade current thermal protection systems in gas turbines. As these become critical to safe operation it will also be necessary to devise techniques for online conditions monitoring and NDE. The authors have proposed thermal barrier sensor coatings (TBSC) as a possible means of achieving NDE for thermal barrier coatings. TBSC’s are made by doping the ceramic material (currently yttria stabilised zirconia) with a rare earth activator to provide the coating with luminescence when excited with UV light. The paper describes the physics of the thermo-luminescent response of such coatings and shows how this can be used to measure temperature. Calibration data is presented along with the results of comparative thermal cycle testing of TBSC’s, produced using a production standard APS system. The latter show the durability of TBSC’s to be similar to that of standard YSZ TBC’s and indicate that the addition of the rare-earth dopant is not detrimental to the coating. Also discussed is the manufacture of functionally structured coatings with discreet doped layers. The temperature at the bond coat interface is important with respect to the life of the coating since it influences the growth rate of the thermally grown oxide layer which in turn destabilises the coating system as it becomes thicker. Experimental data is presented indicating that duallayered TBSC’s can be used to detect luminescence from, and thereby the temperature within, sub surface layers covered by as much as 500μm of standard TBC material. A theoretical analysis of the data has allowed some preliminary calculations of the transmission properties of the overcoat to be made and these suggest that it might be possible to observe phosphorescence and measure temperature through an overcoat layer of up to approximately 1.56mm thickness.

scholarly journals Analytical and Experimental Study of Residual Stresses in Thermal Barrier Coatings Deposited on Gas Turbine Blades in Laboratory Dimensions by APS and HVOF Methods to Calculate the Optimal Thickness

2021 ◽  
Vol 3 (1) ◽  
pp. 63-67
Author(s):  
Esmaeil Poursaeidi ◽  
◽  
Farzam Montakhabi ◽  
Javad Rahimi ◽  
◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Analytical Model ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Optimal Thickness ◽  
Barrier Coatings

The constant need to use gas turbines has led to the need to increase turbines' inlet temperature. When the temperature reaches a level higher than the material's tolerance, phenomena such as creep, changes in mechanical properties, oxidation, and corrosion occur at high speeds, which affects the life of the metal material. Nowadays, operation at high temperatures is made possible by proceedings such as cooling and thermal insulation by thermal barrier coatings (TBCs). The method of applying thermal barrier coatings on the turbine blade creates residual stresses. In this study, residual stresses in thermal barrier coatings applied by APS and HVOF methods are compared by Tsui–Clyne analytical model and XRD test. The analytical model results are in good agreement with the experimental results (between 2 and 8% error), and the HVOF spray method creates less residual stress than APS. In the end, an optimal thickness for the coating is calculated to minimize residual stress at the interface between the bond coat and top coat layers.

Advances in Coating Design for High-Performance Gas Turbines

MRS Bulletin ◽  
2003 ◽  
Vol 28 (9) ◽  
pp. 659-670 ◽  
Author(s):  
J. R. Nicholls
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
High Performance ◽  
Surface Engineering ◽  
Thermal Protection ◽  
Low Cost ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Aluminide Coatings ◽  
Coating Design

AbstractSurface engineering is now a key materials technology in the design of future advanced gas-turbine engines. This article focuses on coating systems for hot-gas-path components, which can vary from low-cost aluminide diffusion coatings to the more exotic, and therefore expensive, thermal-barrier coatings. Available coating systems and their relative benefits are reviewed in terms of performance against manufacturing complexity and cost. Future trends in the design of environmental- and thermal-protection coatings are discussed, including the addition of multiple reactive elements, modified aluminide coatings, diffusion-barrier concepts, the design of “smart” corrosion-resistant coatings, and the development of structurally modified, low-thermal-conductivity thermal-barrier coatings.

scholarly journals Effect of Target Coating Thickness on the Abrasive Waterjet Machining Response of 8YSZ Segmented Thermal Barrier Coatings

2020 ◽  
Vol 2 (1) ◽  
pp. 56-62
Author(s):  
R. Patgunarajah ◽  
◽  
J. P. Borrmann ◽  
J. E. Döring ◽  
A. Sharma ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Machining Process ◽  
Abrasive Waterjet ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Barrier Coatings ◽  
Abrasive Waterjet Machining ◽  
Waterjet Machining ◽  
Thick Coatings

Segmented thermal barrier coatings (STBC) are a more strain-tolerant and erosion resistant alternative of the conventional porous thermal barrier coatings for hot gas components in gas turbines. Due to their relatively higher thermal conductivity and the ever-increasing turbine inlet temperature, there is a need for thicker STBCs. This paper presents an investigation of the microstructures and properties of STBCs with respect to coating thicknesses. Coatings with two significantly different thicknesses were fabricated under identical conditions and evaluated using standard metallographic methods. It was found that the microstructures for thin and thick coatings had subtle differences and hardness values decreased with in increasing thickness. When subjected to an abrasive waterjet machining process, the thicker STBCs showed a higher wear rate. A hypothesis is proposed to explain the observed thickness dependent changes and the microstructures and properties of STBCs.

Self Diagnostic EB-PVD Thermal Barrier Coatings

2010 ◽  
Vol 72 ◽  
pp. 65-74 ◽  
Author(s):  
John R. Nicholls ◽  
Richard G. Wellman ◽  
Remy Steenbakker ◽  
Jörg Feist
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Performance Monitoring ◽  
Thermal Protection ◽  
Interface Temperature ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Design And Manufacture ◽  
Tbc Systems

Thermal barrier coatings (TBCs) are an enabling materials technology to improve the efficiency and durability of gas turbines and thus through such efficiency improvements offer reduce fuel usage and an associated reduction in CO2 emission. This commercial drive is pushing both aero- and industrial turbines to be lifetime dependent on TBC performance – the TBC must be “prime reliant”. However, the prediction of the durability of the TBC system has proved difficult, with lifetimes varying from sample to sample and component to component. One factor controlling this is the inability to measure accurately the bondcoat/ceramic interface temperature when buried under a TBC. In operating engines this is further exacerbated by the fact that such TBC systems operate in strong temperature gradients due to the need to cool aerofoil components. This research examines the design and manufacture of self diagnostic thermal barrier coatings capable of accurately measuring the interface temperature under the TBC, whilst providing the requisite thermal protection. Data on the temperature sensing capability of various rare earth doped EB-PVD thermal barrier coatings will be reported. It will be shown that systems exist capable of measuring temperatures in excess of 1300oC. Details of the measurement method, the compositions and the thermal stability of such systems will be discussed in this paper. The ability to produce a sensing TBC capable of measuring interface temperature, surface temperature and heat flux will further be discussed permitting the design of thermal barrier protected components capable of in-situ performance monitoring.

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.

Design, Preparation and Thermal Properties of (La0.4Sm0.5Yb0.1)2Zr2O7 Ceramic for Thermal Barrier Coatings

2012 ◽  
Vol 512-515 ◽  
pp. 469-473 ◽  
Author(s):  
L. Liu ◽  
Z. Ma ◽  
F.C. Wang ◽  
Q. Xu
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Rare Earth ◽  
Thermal Expansion Coefficient ◽  
Thermal Barrier Coatings ◽  
Expansion Coefficient ◽  
Phonon Transport ◽  
Thermal Barrier ◽  
Barrier Coatings

According to the theory of phonon transport and thermal expansion, a new complex rare-earth zirconate ceramic (La0.4Sm0.5Yb0.1)2Zr2O7, with low thermal conductivity and high thermal expansion coefficient, has been designed by doping proper ions at A sites. The complex rare-earth zirconate (La0.4Sm0.5Yb0.1)2Zr2O7 powder for thermal barrier coatings (TBCs) was synthesized by coprecipitation-calcination method. The phase, microstructure and thermal properties of the new material were investigated. The results revealed that single phase (La0.4Sm0.5Yb0.1)2Zr2O7 with pyrochlore structure was synthesized. The thermal conductivity and the thermal expansion coefficient of the designed complex rare-earth zirconate ceramic is about 1.3W/m•K and 10.5×10-6/K, respectively. These results imply that (La0.4Sm0.5Yb0.1)2Zr2O7 can be explored as the candidate material for the ceramic layer in TBCs system.

scholarly journals Analysis of the energetic/environmental performances of gas turbine plant: Effect of thermal barrier coatings and mass of cooling air

2009 ◽  
Vol 13 (1) ◽  
pp. 147-164 ◽  
Author(s):  
Ion Ion ◽  
Anibal Portinha ◽  
Jorge Martins ◽  
Vasco Teixeira ◽  
Joaquim Carneiro
Keyword(s):  
Thermal Conductivity ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Heat Transfer Analysis ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Barrier Coatings ◽  
Cooling Air Flow ◽  
Cooling Air

Zirconia stabilized with 8 wt.% Y2O3 is the most common material to be applied in thermal barrier coatings owing to its excellent properties: low thermal conductivity, high toughness and thermal expansion coefficient as ceramic material. Calculation has been made to evaluate the gains of thermal barrier coatings applied on gas turbine blades. The study considers a top ceramic coating Zirconia stabilized with 8 wt.% Y2O3 on a NiCoCrAlY bond coat and Inconel 738LC as substrate. For different thickness and different cooling air flow rates, a thermodynamic analysis has been performed and pollutants emissions (CO, NOx) have been estimated to analyze the effect of rising the gas inlet temperature. The effect of thickness and thermal conductivity of top coating and the mass flow rate of cooling air have been analyzed. The model for heat transfer analysis gives the temperature reduction through the wall blade for the considered conditions and the results presented in this contribution are restricted to a two considered limits: (1) maximum allowable temperature for top layer (1200?C) and (2) for blade material (1000?C). The model can be used to analyze other materials that support higher temperatures helping in the development of new materials for thermal barrier coatings.

Effects of Powder Morphology, Microstructure, and Residual Stresses on Thermal Barrier Coating Thermal Shock Performance

1996 ◽  
Author(s):  
J. Wigren ◽  
J.-F. de Vries ◽  
D. Greving
Keyword(s):  
Residual Stresses ◽  
Thermal Shock ◽  
Thermal Barrier Coating ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Spray Parameters ◽  
Powder Morphology ◽  
Barrier Coatings ◽  
Barrier Coating

Abstract Thermal barrier coatings are used in the aerospace industry for thermal insulation in hot sections of gas turbines. Improved coating reliability is a common goal among jet engine designers. In-service failures, such as coating cracking and spallation, result in decreased engine performance and costly maintenance time. A research program was conducted to evaluate residual stresses, microstructure, and thermal shock life of thermal barrier coatings produced from different powder types and spray parameters. Sixteen coatings were ranked according to their performance relative to the other coatings in each evaluation category. Comparisons of residual stresses, powder morphology, and microstructure to thermal shock life indicate a strong correlation to thermal barrier coating performance. Results from these evaluations will aid in the selection of an optimum thermal barrier coating system for turbine engine applications.

Sign in / Sign up

Export Citation Format

Share Document