Stability Study of EBC/TBC Hybrid System on Si-based Ceramics in Gas Turbines

2012 ◽  
Vol 1519 ◽  
Author(s):  
JiaPeng Xu ◽  
Vinod Sarin ◽  
Soumendra Basu
Keyword(s):  
High Temperature ◽  
Hybrid System ◽  
Hot Corrosion ◽  
Gas Turbines ◽  
Ceramic Matrix Composites ◽  
Functionally Graded ◽  
Air Plasma ◽  
High Temperature Stability ◽  
Chemical Attack ◽  
Barrier Coating

ABSTRACTCurrently, ceramics are being used under increasingly demanding environments. These materials have to exhibit phase stability and resist chemical attack during service. This research involves the study of the high-temperature stability of ceramic materials in gas turbines. SiC/SiC ceramic matrix composites (CMCs) are being increasingly used in the hot-sections of gas turbines, especially for aerospace applications. These CMCs are prone to recession of their surface if exposed to a flow of high-velocity water vapor, and to hot-corrosion when exposed to molten alkali salts. The objective of this investigation was the development of a hybrid system containing an environmental barrier coating (EBC) for protection of the CMC from chemical attack and a thermal barrier coating (TBC) that allows a steep temperature gradient across it to lower the temperature of the CMC for increased lifetimes. The EBC used was a functionally graded mullite (3Al2O3∙2SiO2) coating deposited by chemical vapor deposition (CVD), while the TBC layer was yttria-stabilized zirconia (YSZ) deposited by air plasma spray (APS). The stability of this system was investigated, via adhesion between the two coating layers and the substrate, the physical and chemical stability of each layer at high temperature, and the performance under severe thermal shock and exposure to hot corrosion.

HOT CORROSION OF CERIA-YTTRIA STABILIZED ZIRCONIA PLASMA SPRAYED THERMAL BARRIER COATING BY EUTECTIC VANDIUM PENTAOXIDE-SODIUM SULFATE

2018 ◽  
Vol 18 (1) ◽  
pp. 182-192 ◽  
Author(s):  
Mohammed J Kadhim ◽  
Mohammed H Hafiz ◽  
Maryam A Ali Bash
Keyword(s):  
Thermal Barrier Coating ◽  
Hot Corrosion ◽  
Monoclinic Phase ◽  
Volume Fraction ◽  
High Volume ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Plan View ◽  
Barrier Coating ◽  
Plasma Sprayed

The high temperature corrosion behavior of thermal barrier coating (TBC) systemconsisting of IN-738 LC superalloy substrate, air plasma sprayed Ni24.5Cr6Al0.4Y (wt%)bond coat and air plasma sprayed ZrO2-20 wt% ceria-3.6 wt% yttria (CYSZ) ceramic coatwere characterized. The upper surfaces of CYSZ covered with 30 mg/cm2 , mixed 45 wt%Na2SO4-55 wt% V2O5 salt were exposed at different temperatures from 800 to 1000 oC andinteraction times from 1 up to 8 h. The upper surface plan view of the coatings wereidentified for topography, roughness, chemical composition, phases and reaction productsusing scanning electron microscopy, energy dispersive spectroscopy, talysurf, and X-raydiffraction. XRD analyses of the plasma sprayed coatings after hot corrosion confirmed thephase transformation of nontransformable tetragonal (t') into monoclinic phase, presence ofYVO4 and CeVO4 products. Analysis of the hot corrosion CYSZ coating confirmed theformation of high volume fraction of YVO4, with low volume fractions of CeOV4 and CeO2.The formation of these compounds were combined with formation of monoclinic phase (m)from transformation of nontransformable tetragonal phase (t').

scholarly journals Rear Earth Oxide Multilayer Deposited by Plasma Spray-Physical Vapor Deposition for Envisaged Application as Thermal/Environmental Barrier Coating

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 889
Author(s):  
Jie Zhong ◽  
Dongling Yang ◽  
Shuangquan Guo ◽  
Xiaofeng Zhang ◽  
Xinghua Liang ◽  
...  
Keyword(s):  
Composite Coating ◽  
High Temperatures ◽  
Physical Vapor Deposition ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Composites ◽  
Environmental Barrier ◽  
Chemical Attack ◽  
Environmental Barrier Coating ◽  
Barrier Coating

SiC fiber-reinforced SiC ceramic matrix composites (SiCf/SiC CMCs) are being increasingly used in the hot sections of gas turbines because of their light weight and mechanical properties at high temperatures. The objective of this investigation was the development of a thermal/environmental barrier coating (T/EBC) composite coating system consisting of an environmental barrier coating (EBC) to protect the ceramic matrix composites from chemical attack and a thermal barrier coating (TBC) that insulates and reduces the ceramic matrix composites substrate temperature for increased lifetime. In this paper, a plasma spray-physical vapor deposition (PS-PVD) method was used to prepare multilayer Si–HfO2/Yb2Si2O7/Yb2SiO5/Gd2Zr2O7 composite coatings on the surface of SiCf/SiC ceramic matrix composites. The purpose of this study is to develop a coating with resistance to high temperatures and chemical attack. Different process parameters are adopted, and their influence on the microstructure characteristics of the coating is discussed. The water quenching thermal cycle of the coating at high temperatures was tested. The results show that the structure of the thermal/environmental barrier composite coating changes after water quenching because point defects and dislocations appear in the Gd2Zr2O7 and Yb2SiO5 coatings. A phase transition was found to occur in the Yb2SiO5 and Yb2Si2O7 coatings. The failure mechanism of the T/EBC composite coating is mainly spalling when the top layer penetrates cracks and cracking occurs in the interface of the Si–HfO2/Yb2Si2O7 coating.

Use of Chromium Containing Fuel Additive to Reduce High Temperature Corrosion of Hot Section Parts

2000 ◽  
Author(s):  
Jean-Pierre Stalder ◽  
Peter A. Huber
Keyword(s):  
High Temperature ◽  
Hot Corrosion ◽  
Gas Turbines ◽  
High Temperature Corrosion ◽  
Fuel Oil ◽  
Fuel Additive ◽  
Fuel Quality ◽  
Common Belief ◽  
Heavy Fuel Oil ◽  
Fuel Treatment

The use of “clean” fuel is a prerequisite at today’s elevated gas turbine firing temperature, modern engines are more sensitive to high temperature corrosion if there are impurities present in the fuel and/or in the combustion air. It is a common belief that distillate grade fuels are contaminant-free, which is often not true. Frequently operators burning distillates ignore the fuel quality as a possible source of difficulties. This matter being also of concern in plants mainly operated on natural gas and where distillate fuel oil is the back-up fuel. Distillates may contain water, dirt and often trace metals such as sodium, vanadium and lead which can cause severe damages to the gas turbines. Sodium being very often introduced through contamination with seawater during the fuel storage and delivery chain to the plant, and in combination, or with air borne salt ingested by the combustion air. Excursions of sodium in treated crude or heavy fuel oil can occur during unnoticed malfunctions of the fuel treatment plant, when changing the heavy fuel provenience without centrifuge adjustment, or by inadequate fuel handling. For burning heavy fuel, treatment with oil-soluble magnesium fuel additive is state of the art to inhibit hot corrosion caused by vanadium. Air borne salts, sodium, potassium and lead contaminated distillates, gaseous fuels, washed and unwashed crude and residual oil can not be handled by simple magnesium based additives. The addition of elements like silicon and/or chromium is highly effective in reducing turbine blade hot corrosion and hot section fouling. This paper describes field experience with the use of chromium containing fuel additive to reduce high temperature corrosion of hot section parts, as well as the interaction of oil-soluble chromium and magnesium-chromium additives on material behaviour of blades and vanes, and their economical and environmental aspects.

Derivation of Temperature-Estimation Equation Based on Microstructural Changes in Coatings of In-Service Blades of Gas Turbines

2010 ◽  
Author(s):  
Mitsutoshi Okada ◽  
Tohru Hisamatsu ◽  
Terutaka Fujioka
Keyword(s):  
High Temperature ◽  
Diffusion Layer ◽  
Gas Turbines ◽  
Aluminum Content ◽  
Oxide Formation ◽  
Diffusion Layer Thickness ◽  
Temperature Estimation ◽  
Diffusion Layers ◽  
Barrier Coating ◽  
Trailing Edges

A CoNiCrAlY-coated blade of an in-service gas turbine is analyzed, and a diffusion layer is formed along the boundary between the coating and the substrate due to the interdiffusion in the middle and tip of the blade. Such a layer is not observed in the vicinity of the blade root because of a comparatively low temperature during the operation. Coated specimens are prepared from the portions of the blade devoid of the diffusion layers, and the specimens are exposed to a high temperature in air. On the basis of the increase in the diffusion layer thickness, an equation for estimating the temperature of the blade is derived. Analysis of another in-service blade with a thermal barrier coating (TBC) is carried out. The aluminum-content decreases below the bond coat surface due to Al diffusion caused by the Al-oxide formation. This results in the formation of an Al-decreased layer (ADL) along the leading and trailing edges. The ADL is not observed at the center of the blade chord. The specimens are extracted from the portions of the blade that are devoid of ADL, and they are subjected to a high temperature in air. On the basis of the increase in the ADL thickness, a temperature-estimation equation is derived.

Thermal Barrier Coating Applied to the Structural Shroud of an Inside-Out Ceramic Turbine

2021 ◽  
Author(s):  
P. K. Dubois ◽  
A. Gauvin-Verville ◽  
B. Picard ◽  
J.-S. Plante ◽  
M. Picard
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coating ◽  
Internal Surface ◽  
Small Scale ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Air Plasma ◽  
Barrier Coating ◽  
Deformation Mechanics ◽  
Inside Out

Abstract Recuperated, high-temperature microturbines (< 1 MW) could be a key enabler for hybrid powertrains of tomorrow’s small aircraft. To achieve competitive thermal efficiencies, turbine inlet temperature (TIT) must increase to 1550 K, well beyond conventional metallic microturbine limits. This calls for high-temperature refractory ceramics, which call for a new ceramic-specific, microturbine design like the Inside-Out Ceramic Turbine (ICT). This study focuses on the applicability of a refractory thermal barrier coating (TBC) to the internal surface of the ICT cooling ring. By cutting the heat transfer from the main flow to the structural rim-rotor, the use of a refractory TBC coating in an ICT enables higher TIT and lower cooling air mass flow. A preliminary experimental assessment is done at room temperature on 1 mm-thick coatings of 8% yttria-stabilized zirconia (8YSZ), air plasma sprayed (APS) TBC, applied to Inconel 718 and Ti64 test coupons. Results show that the strongly orthotropic behaviour of the tested TBC fits perfectly with the deformation mechanics of the ICT configuration under load. First, large in-plane strain tolerance allows the large tangential deformation imposed by the structural shroud under centrifugal loading. Second, high out-of-plane stiffness and compressive resistance combine to support extreme compressive loads with no apparent damage to the TBC even at more than 3 times blade indentation average loading. An experimental demonstration on a small-scale prototype shows a reduction of 40% in cooling flow in a, 8-minute ICT test, with no damage to the TBC, proving the effectiveness and potential of the proposed TBC design.

High Temperature Solid Particle Erosion in a Melt-Infiltrated SiC/SiC Ceramic Matrix Composite

2021 ◽  
Author(s):  
Michael J. Presby
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Gas Turbines ◽  
Material Removal ◽  
Gas Flow ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Solid Particles ◽  
Material System

Abstract Ceramic matrix composites (CMCs) are an enabling propulsion material system that offer weight benefits over current Ni-based superalloys, and have higher temperature capabilities that can reduce cooling requirements. Incorporating CMCs into the hot section of gas-turbine engines therefore leads to an increase in engine efficiency. While significant advancements have been made, challenges still remain for current and next-generation gas-turbines; particularly when operating in dust-laden or erosive environments. Solid particles entrained in the gas flow can impact engine hardware resulting in localized damage and material removal due to repeated, cumulative impacts. In this study, the erosion behavior of a melt-infiltrated (MI) silicon carbide fiber-reinforced silicon carbide (SiC/SiC) CMC is investigated at high temperature (1,200 °C) in a simulated combustion environment using 150 μm alumina particles as erodent. Particle impact velocities ranged from 100 to 200 m/s and the angle of impingement varied from 30° to 90°. Erosion testing was also performed on α-SiC to elucidate similarities and differences in the erosion response of the composite compared to that of a monolithic ceramic. Scanning electron microscopy (SEM) was used to study the post-erosion damage morphology and the governing mechanisms of material removal.

Off-Line Temperature Profiling Utilising Phosphorescent Thermal History Paints and Coatings

2014 ◽  
Author(s):  
J. P. Feist ◽  
S. Karmaker Biswas ◽  
C. Pilgrim ◽  
P. Y. Sollazzo ◽  
S. Berthier
Keyword(s):  
Thermal History ◽  
Gas Turbines ◽  
Elevated Temperatures ◽  
Life Time ◽  
Temperature Measurements ◽  
Host Material ◽  
Air Plasma ◽  
Spray Process ◽  
Barrier Coating ◽  
Line Temperature

Temperature profiling of components in gas turbines is of increasing importance as engineers drive to increase firing temperatures and optimise component’s cooling requirements in order to increase efficiency and lower CO2 emissions. However, on-line temperature measurements and, particularly, temperature profiling are difficult, sometimes impossible, to perform due to inaccessibility of the components. A desirable alternative would be to record the exposure temperature in such a way that it can be determined later, off-line. The commercially available Thermal Paints are toxic in nature and come with a range of technical disadvantages such as subjective readout and limited durability. This paper proposes a novel alternative measurement technique which the authors call Thermal History Paints and Thermal History Coatings. These can be particularly useful in the design process, but further could provide benefits in the maintenance area where hotspots which occurred during operation can be detected during maintenance intervals when the engine is at ambient temperature. This novel temperature profiling technique uses optical active ions in a ceramic host material. When these ions are excited by light they start to phosphoresce. The host material undergoes irreversible changes when exposed to elevated temperatures and since these changes are on the atomic level they influence the phosphorescent properties such as the life time decay of the phosphorescence. The changes in phosphorescence can be related to temperature through calibration such that in-situ analysis will return the temperature experienced by the coating. A major benefit of this technique is in the automated interpretation of the coatings. An electronic instrument is used to measure the phosphorescence signal eliminating the need for a specialist interpreter and thus increasing readout speed. This paper reviews results from temperature measurements made with a water based paint for the temperature range 100°C to 800°C in controlled conditions. Repeatability of the tests and errors will be discussed. Further, some measurements are carried out using an electronic hand-held interrogation device which can scan a component surface and provide a spatial resolution of below 3mm. The instrument enables mobile measurements outside of laboratory conditions. Further a robust Thermal History Coating is introduced demonstrating the capability of the coating to withstand long term exposures. The coating is based on Thermal Barrier Coating architecture with a high temperature bondcoat and deposited using an air plasma spray process to manufacture a reliable long lasting coating. Such a coating could be employed over the life of the component to provide critical temperature information at regular maintenance intervals for example indicating hot spots on engine parts.

Hot Corrosion and its Prevention in High Temperature Heavy Oil Firing Gas Turbines

1997 ◽  
Vol 251-254 ◽  
pp. 633-640 ◽  
Author(s):  
M. Nakamori ◽  
I. Kayano ◽  
Y. Tsukuda ◽  
Kunimasa Takahashi ◽  
Taiji Torigoe
Keyword(s):  
High Temperature ◽  
Heavy Oil ◽  
Hot Corrosion ◽  
Gas Turbines
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