scholarly journals High-Porosity Thermal Barrier Coatings from High-Power Plasma Spray Equipment—Processing, Performance and Economics

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 957
Author(s):  
Nicholas Curry ◽  
Matthias Leitner ◽  
Karl Körner
Keyword(s):  
Thermal Barrier Coatings ◽  
High Power ◽  
Deposition Efficiency ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Low Density ◽  
High Porosity ◽  
Plasma System ◽  
Barrier Coatings ◽  
The Impact

High-porosity thermal barrier coatings are utilized on gas turbine components where maximizing the coating thermal insulation capability is the primary design criteria. Though such coatings have been in industrial use for some time, manufacturing high-porosity coatings quickly and efficiently has proven challenging. With the industry demand to increase productivity and reduce waste generation, there is a drive to look at improved coating manufacturing methods. This article looks at high-porosity coatings manufactured using a high-power plasma system in comparison with a current industrial coating. A commercial spray powder is compared with an experimental Low-Density powder developed to maximize coating porosity without sacrificing coating deposition efficiency. The resultant coatings have been assessed for their microstructure, adhesion strength, furnace cyclic lifetime, thermal conductivity and sintering behavior. Finally, the impact of spray processing on coating economics is discussed. The use of a Low-Density powder with a high-power plasma system allows a high-porosity coating to be manufactured more efficiently and more cost effectively than with conventional powder feedstock. The improvement in thermal properties for the experimental coating demonstrates there is scope to improve industrial coatings by designing with specific thermal resistance rather than thickness and porosity as coating requirements.

Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

2015 ◽  
Vol 24 (4) ◽  
pp. 622-628 ◽  
Author(s):  
Jan Medřický ◽  
Nicholas Curry ◽  
Zdenek Pala ◽  
Monika Vilemova ◽  
Tomas Chraska ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
High Porosity ◽  
Barrier Coatings

scholarly journals Impact of Cooling with Thermal Barrier Coatings on Flow Passage in a Gas Turbine

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 85
Author(s):  
Yuanzhe Zhang ◽  
Pei Liu ◽  
Zheng Li
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Power Sources ◽  
Barrier Coatings ◽  
Flow Passage ◽  
Blade Cooling ◽  
The Impact

Inlet temperature is vital to the thermal efficiency of gas turbines, which is becoming increasingly important in the context of structural changes in power supplies with more intermittent renewable power sources. Blade cooling is a key method for gas turbines to maintain high inlet temperatures whilst also meeting material temperature limits. However, the implementation of blade cooling within a gas turbine—for instance, thermal barrier coatings (TBCs)—might also change its heat transfer characteristics and lead to challenges in calculating its internal temperature and thermal efficiency. Existing studies have mainly focused on the materials and mechanisms of TBCs and the impact of TBCs on turbine blades. However, these analyses are insufficient for measuring the overall impact of TBCs on turbines. In this study, the impact of TBC thickness on the performance of gas turbines is analyzed. An improved mathematical model for turbine flow passage is proposed, considering the impact of cooling with TBCs. This model has the function of analyzing the impact of TBCs on turbine geometry. By changing the TBCs’ thickness from 0.0005 m to 0.0013 m, its effects on turbine flow passage are quantitatively analyzed using the proposed model. The variation rules of the cooling air ratio, turbine inlet mass flow rate, and turbine flow passage structure within the range of 0.0005 m to 0.0013 m of TBC thicknesses are given.

scholarly journals Nano-Micro-Structured 6%–8% YSZ Thermal Barrier Coatings: A Comprehensive Review of Comparative Performance Analysis

Coatings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1474
Author(s):  
Amarnath Kumar ◽  
Jenna Moledina ◽  
Yuan Liu ◽  
Kuiying Chen ◽  
Prakash C. Patnaik
Keyword(s):  
Performance Analysis ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Comparative Performance ◽  
Barrier Coatings ◽  
Comprehensive Review ◽  
Wide Range ◽  
Tbc Systems

Beneficial properties achieved by nanostructuring effects in materials have generated tremendous interests in applications in surface engineering, especially in thermal barrier coatings (TBC). Limitations in conventional TBC processing for gas turbines and aero-propulsion systems have been exposed during past decades when rapid progress was made in nano-structuring coating research and developments. The present work is a comprehensive review of the current state of progress in nanostructured TBC (Ntbc) in reference to its microstructure, damage progression, failure mechanisms and a wide range of properties. The review aims to address the comparative performance analysis between the nanostructured and conventional (microstructured) 6–8 wt.% yttrium stabilized zirconia (YSZ) TBC systems. Oxidation resistance and sintering behavior in two TBCs are considered as the central focus of discussion. A few schematics are used to represent major microstructural features and failure progression. A performance analysis is performed for standard 2-layer, as well as functionally graded multilayer, TBC systems. A comparison of TBC characteristics processed by plasma spray and vapor deposition techniques is also made as reference. Compared to the sea of R&D efforts made for conventional TBC (Ctbc), limited experimental studies on Ntbc offers conflicting data, and prediction modeling and computational research are scarce.

scholarly journals Revisiting the Birth of 7YSZ Thermal Barrier Coatings: Stephan Stecura †

Coatings ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 255 ◽  
Author(s):  
James Smialek ◽  
Robert Miller
Keyword(s):  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Turbine Engines ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Turbine Engine ◽  
Power Turbine ◽  
Plasma Sprayed ◽  
The Impact

Thermal barrier coatings are widely used in all turbine engines, typically using a 7 wt.% Y2O3–ZrO2 formulation. Extensive research and development over many decades have refined the processing and structure of these coatings for increased durability and reliability. New compositions demonstrate some unique advantages and are gaining in application. However, the “7YSZ” (7 wt.% yttria stabilized zirconia) formulation predominates and is still in widespread use. This special composition has been universally found to produce nanoscale precipitates of metastable t’ tetragonal phase, giving rise to a unique toughening mechanism via ferro-elastic switching under stress. This note recalls the original study that identified superior properties of 6–8 wt.% yttria stabilized zirconia (YSZ) plasma sprayed thermal barrier coatings, published in 1978. The impact of this discovery, arguably, continues in some form to this day. At one point, 7YSZ thermal barrier coatings were used in every new aircraft and ground power turbine engine produced worldwide. 7YSZ is a tribute to its inventor, Dr. Stephan Stecura, NASA retiree.

Assessing the Impact of Thermal Barrier Coatings on Charge Temperature Stratification Within a Homogeneous Charge Compression Ignition Engine

2018 ◽  
Author(s):  
Ryan O’Donnell ◽  
Tommy Powell ◽  
Zoran Filipi ◽  
Mark Hoffman
Keyword(s):  
Thermal Barrier Coatings ◽  
Homogeneous Charge Compression Ignition ◽  
Thermal Barrier ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Barrier Coatings ◽  
Charge Mass ◽  
The Impact ◽  
Charge Temperature ◽  
Homogeneous Charge

The application of a Thermal Barrier Coating (TBC) to combustion chamber surfaces within a Low Temperature Combustion (LTC) engine alters conditions at the gas-wall boundary and affects the temperature field of the interior charge. Thin, low-conductivity, TBCs (∼150μm) exhibit elevated surface temperatures during late compression and expansion processes. This temperature ‘swing’ reduces gas-to-wall heat transfer during combustion and expansion, alters reaction rates in the wall affected zones, and improves thermal efficiency. In this paper, Thermal Stratification Analysis (TSA) is employed to quantify the impact of Thermal Barrier Coatings on the charge temperature distribution within a gasoline-fueled Homogeneous Charge Compression Ignition (HCCI) engine. Using an empirically derived ignition delay correlation for HCCI-relevant air-to-fuel ratios, an autoignition integral is tracked across multiple temperature ‘zones’. Charge mass is assigned to each zone by referencing the Mass Fraction Burn (MFB) profile from the corresponding heat release analysis. Closed-cycle temperature distributions are generated for baseline (i.e., ‘metal’) and TBC-treated engine configurations. In general, the TBC-treated engine configurations are shown to maintain a higher percentage of charge mass at temperatures approximating the isentropic limit.

Damage Analysis of Thermal Barrier Coatings Subjected to a High-Velocity Impingement of a Solid Sphere

2019 ◽  
Vol 827 ◽  
pp. 349-354
Author(s):  
Kiyohiro Ito ◽  
Fei Gao ◽  
Masayuki Arai
Keyword(s):  
Gas Turbine ◽  
Impact Velocity ◽  
Thermal Barrier Coatings ◽  
High Velocity ◽  
Turbine Blades ◽  
Interfacial Crack ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Wide Range ◽  
The Impact

A delamination of thermal barrier coatings (TBC) applied to turbine blades in gas turbine could be caused by a high-velocity impingement of various foreign objects. It is important to accurately predict the size of interfacial crack for safety operation of gas turbine. In this study, in order to establish a practical equation for prediction of the length of interfacial crack, a high velocity impingement test and a finite element analysis (FEA) based on a cohesive model were conducted. As the result, the length of interfacial crack is linearly increased with the impact velocity. In addition, it was confirmed that it was accurately estimated by the FEA. The equation for prediction of the length of interfacial crack was formulated based on these results and the energy conservation before and after impingement. Finally, the applicability of the equation was demonstrated in a wide range of impact velocity through a comparison with the experimental results.

scholarly journals Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2238
Author(s):  
Satyapal Mahade ◽  
Nicholas Curry ◽  
Stefan Björklund ◽  
Nicolaie Markocsan ◽  
Shrikant Joshi
Keyword(s):  
Layer Thickness ◽  
Thermal Barrier Coatings ◽  
Failure Modes ◽  
Cyclic Test ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Gadolinium Zirconate ◽  
Test Conditions ◽  
Thermal Cyclic Test

Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.

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