Environmental Barrier Coating Oxidation and Adhesion Strength

2020 ◽  
Author(s):  
Bryan J. Harder ◽  
Michael J. Presby ◽  
Jon A. Salem ◽  
Steven M. Arnold ◽  
Subodh K. Mital
Keyword(s):  
Adhesion Strength ◽  
Physical Vapor Deposition ◽  
Ceramic Matrix Composites ◽  
Thermally Grown Oxide ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Barrier Coating ◽  
Coating Durability

Abstract Plasma Spray-Physical Vapor Deposition (PS-PVD) environmental barrier coatings (EBCs) of Yb2Si2O7 were deposited on SiC and exposed in a steam environment (90% H2O/O2) at 1426°C to form a thermally grown oxide (TGO) layer between the substrate and EBC. In advanced ceramic material systems such as coated ceramic matrix composites (CMCs), the TGO layer is the weak interface in coated CMC systems and directly influences component lifetimes. The effect of surface roughness and TGO thickness on the adhesion strength were evaluated by mechanical testing of the coatings after exposure. Morphology and oxide layer thickness were analyzed with electron microscopy while the composition and crystal structure were tracked with X-ray diffraction. The strength of the system is evaluated with respect to oxidation rate to give a qualitative understanding of coating durability.

Environmental Barrier Coating Oxidation and Adhesion Strength

2020 ◽  
Author(s):  
Bryan Harder ◽  
Michael Presby ◽  
Jon Salem ◽  
Steven M. Arnold ◽  
Subodh Mital
Keyword(s):  
Adhesion Strength ◽  
Physical Vapor Deposition ◽  
Ceramic Matrix Composites ◽  
Thermally Grown Oxide ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Barrier Coating ◽  
Coating Durability

Abstract Plasma Spray- Physical Vapor Deposition (PS-PVD) environmental barrier coatings (EBCs) of Yb2Si2O7 were deposited on SiC and exposed in a steam environment (90% H2O/O2) at 1426°C to form a thermally grown oxide (TGO) layer between the substrate and EBC. In advanced ceramic material systems such as coated ceramic matrix composites (CMCs), the TGO layer is the weak interface in coated CMC systems and directly influences component lifetimes. The effect of surface roughness and TGO thickness on the adhesion strength were evaluated by mechanical testing of the coatings after exposure. Morphology and oxide layer thickness were analyzed with electron microscopy while the composition and crystal structure were tracked with X-ray diffraction. The strength of the system is evaluated with respect to oxidation rate to give a qualitative understanding of coating durability.

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.

scholarly journals Environmental Barrier Coatings Made by Different Thermal Spray Technologies

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 784 ◽  
Author(s):  
Robert Vaßen ◽  
Emine Bakan ◽  
Caren Gatzen ◽  
Seongwong Kim ◽  
Daniel Emil Mack ◽  
...  
Keyword(s):  
Plasma Spraying ◽  
Thermal Spray ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Atmospheric Plasma ◽  
Matrix Composites ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Thermal Expansion Coefficients

Environmental barrier coatings (EBCs) are essential to protect ceramic matrix composites against water vapor recession in typical gas turbine environments. Both oxide and non-oxide-based ceramic matrix composites (CMCs) need such coatings as they show only a limited stability. As the thermal expansion coefficients are quite different between the two CMCs, the suitable EBC materials for both applications are different. In the paper examples of EBCs for both types of CMCs are presented. In case of EBCs for oxide-based CMCs, the limited strength of the CMC leads to damage of the surface if standard grit-blasting techniques are used. Only in the case of oxide-based CMCs different processes as laser ablation have been used to optimize the surface topography. Another result for many EBCs for oxide-based CMC is the possibility to deposit them by standard atmospheric plasma spraying (APS) as crystalline coatings. Hence, in case of these coatings only the APS process will be described. For the EBCs for non-oxide CMCs the state-of-the-art materials are rare earth or yttrium silicates. Here the major challenge is to obtain dense and crystalline coatings. While for the Y2SiO5 a promising microstructure could be obtained by a heat-treatment of an APS coating, this was not the case for Yb2Si2O7. Here also other thermal spray processes as high velocity oxygen fuel (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) are used and the results described mainly with respect to crystallinity and porosity.

scholarly journals YAlO3—A Novel Environmental Barrier Coating for Al2O3/Al2O3–Ceramic Matrix Composites

Coatings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 609 ◽  
Author(s):  
Caren Gatzen ◽  
Daniel Emil Mack ◽  
Olivier Guillon ◽  
Robert Vaßen
Keyword(s):  
Plasma Spraying ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Atmospheric Plasma ◽  
Aluminum Silicate ◽  
Matrix Composites ◽  
Surface Pretreatment ◽  
X Ray ◽  
Environmental Barrier ◽  
Barrier Coating

Ceramic matrix composites (CMCs) are promising materials for high-temperature applications. Environmental barrier coatings (EBCs) are needed to protect the components against water vapor attack. A new potential EBC material, YAlO3, was studied in this paper. Different plasma-spraying techniques were used for the production of coatings on an alumina-based CMC, such as atmospheric plasma spraying (APS) and very low pressure plasma spraying (VLPPS). No bond coats or surface treatments were applied. The performance was tested by pull–adhesion tests, burner rig tests, and calcium-magnesium-aluminum-silicate (CMAS) corrosion tests. The samples were subsequently analyzed by means of X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Special attention was paid to the interaction at the interface between coating and substrate. The results show that fully crystalline and good adherent YAlO3 coatings can be produced without further substrate preparation such as surface pretreatment or bond coat application. The formation of a thin reaction layer between coating and substrate seems to promote adhesion.

scholarly journals Water Vapor Corrosion Behavior of Yb2SiO5 Environmental Barrier Coatings Prepared by Plasma Spray-Physical Vapor Deposition

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 392 ◽  
Author(s):  
Chao Wang ◽  
Min Liu ◽  
Junli Feng ◽  
Xiaofeng Zhang ◽  
Chunming Deng ◽  
...  
Keyword(s):  
Water Vapor ◽  
Porous Structure ◽  
Plasma Spray ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Ceramic Matrix Composite ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Barrier Coating ◽  
Water Vapor Corrosion

Tri-layer Si/mullite/Yb2SiO5 environmental barrier coating (EBC) was prepared on the SiCf/SiC ceramic matrix composite (CMC) by plasma spray-physical vapor deposition (PS-PVD). The EBC samples were carried out with water vapor corrosion at 1300 °C for 200 h. After steam corrosion, Yb2SiO5 layer forms a gradient porous structure. This is mainly due to the inclusion of SiO2-rich layer which is precipitated from the gasification inside the coating and existing a small amount of Yb2O3 separately. During the corrosion process, water vapor infiltrates into the coating and reacts with the SiO2 and Yb2O3 to generate volatile substances. This forms a porous structure to make the coating brittle, resulting in mud cracks finally. In addition, the results show that the Yb2SiO5 can react with the water vapor at the coating surface, forming an Yb2Si2O7 top layer.

Development and Evaluation of Environmental Barrier Coatings for Silicon Nitride

2002 ◽  
Author(s):  
Ellen Y. Sun ◽  
Harry E. Eaton ◽  
John E. Holowczak ◽  
Gary D. Linsey
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Ceramic Matrix Composites ◽  
Turbine Engines ◽  
Matrix Composites ◽  
Gas Turbine Engines ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Temperature Capability

Environmental barrier coatings (EBCs) are required for applications of silicon nitride (Si3N4) and silicon carbide (SiC) based materials in gas turbine engines because of the accelerated oxidation of Si3N4 and SiC and subsequent volatilization of silica in the high temperature high-pressure steam environment. EBC systems for silicon carbide fiber reinforced silicon carbide ceramic matrix composites (SiC/SiC CMC’s) were first developed and have been demonstrated via long-term engine tests. Recently, studies have been carried out at United Technologies Research Center (UTRC) to understand the temperature capability of the current celsian-based EBC systems and its suitability for silicon nitride ceramics concerning thermal expansion mismatch between the EBC coating and silicon nitride substrates. This paper will present recent progress in improving the temperature capability of the celsian –based EBC systems and discuss their effectiveness for silicon nitride.

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