scholarly journals Steam Degradation of Ytterbium Disilicate Environmental Barrier Coatings: Effect of Composition, Microstructure and Temperature

2022 ◽  
Author(s):  
Daniel Tejero-Martin ◽  
Mingwen Bai ◽  
Acacio R. Romero ◽  
Richard G. Wellman ◽  
Tanvir Hussain
Keyword(s):  
Underlying Mechanism ◽  
Turbine Engines ◽  
Free Standing ◽  
Porosity Level ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Three Samples ◽  
High Temperature Steam ◽  
Plasma Sprayed

Recession of environmental barrier coatings (EBC) in environments containing steam is a pressing concern that requires further research before their implementation in gas turbine engines can be realized. In this work, free-standing plasma sprayed Yb2Si2O7 coatings were exposed to flowing steam at 1350 °C and 1400 °C for 96 h. Three samples were investigated, one coating with a low porosity level (< 3 %) and 1 wt.% Al2O3 representing traditional EBCs; and two coatings with higher porosity levels (~20 %) representing abradable EBCs. Phase composition and microstructural evolution were studied in order to reveal the underlying mechanism for the interaction between high temperature steam and ytterbium disilicate. The results show depletion of Yb2SiO5 near the surface and formation of ytterbium garnet (Yb3Al5O12) on top of all three coatings due to the reaction with gaseous Al-containing impurities coming from the alumina furnace tubes. The 1 wt.% Al2O3 added to the EBC sample exacerbated the formation of garnet at 1400 °C compared to the abradable samples, which presented lower quantities of garnet. Additionally, inter-splat boundaries were visible after exposure, indicating preferential ingress of gaseous Al-containing impurities through the splat boundaries.

Computational investigation of foreign object damage sustained by environmental barrier coatings (EBCs) and SiC/SiC ceramic-matrix composites (CMCs)

2015 ◽  
Vol 11 (2) ◽  
pp. 238-272 ◽  
Author(s):  
Mica Grujicic ◽  
Jennifer Snipes ◽  
Ramin Yavari ◽  
S. Ramaswami ◽  
Rohan Galgalikar
Keyword(s):  
Gas Turbine ◽  
Ceramic Matrix ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Foreign Object ◽  
Barrier Coatings ◽  
Content Type ◽  
Environmental Barrier Coatings ◽  
Foreign Object Damage ◽  
Environmental Barrier

Purpose – The purpose of this paper is to prevent their recession caused through chemical reaction with high-temperature water vapor, SiC-fiber/SiC-matrix ceramic-matrix composite (CMC) components used in gas-turbine engines are commonly protected with so-called environmental barrier coatings (EBCs). EBCs typically consist of three layers: a top thermal and mechanical protection coat; an intermediate layer which provides environmental protection; and a bond coat which assures good EBC/CMC adhesion. The materials used in different layers and their thicknesses are selected in such a way that the coating performance is optimized for the gas-turbine component in question. Design/methodology/approach – Gas-turbine engines, while in service, often tend to ingest various foreign objects of different sizes. Such objects, entrained within the gas flow, can be accelerated to velocities as high as 600 m/s and, on impact, cause substantial damage to the EBC and SiC/SiC CMC substrate, compromising the component integrity and service life. The problem of foreign object damage (FOD) is addressed in the present work computationally using a series of transient non-linear dynamics finite-element analyses. Before such analyses could be conducted, a major effort had to be invested toward developing, parameterizing and validating the constitutive models for all attendant materials. Findings – The computed FOD results are compared with their experimental counterparts in order to validate the numerical methodology employed. Originality/value – To the authors’ knowledge, the present work is the first reported study dealing with the computational analysis of the FOD sustained by CMCs protected with EBCs.

Development and Evaluation of Environmental Barrier Coatings for Si-Based Ceramics

2004 ◽  
Author(s):  
Tania Bhatia ◽  
Venkat Vedula ◽  
Harry Eaton ◽  
Ellen Sun ◽  
John Holowczak ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Field Tests ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
And Performance ◽  
Combustor Liner

Environmental barrier coatings (EBCs) are being developed for silicon carbide (SiC) based composites and monolithic silicon nitride (Si3N4) to protect against the accelerated oxidation and subsequent silica volatilization in high temperature, high-pressure steam environments encountered in gas turbine engines. While EBCs for silicon carbide (EBCSiC) have been demonstrated in combustor liner applications, efforts are ongoing in the development of EBC systems for silicon nitride (EBCSiN). The challenges of adapting EBCSiC to monolithic Si3N4 are discussed in this paper. Progress in the area of EBCSiN including development and performance during field tests and tests simulating engine conditions are reviewed.

Environmental Barrier Coatings for Monolithic Silicon Nitride: Bond Coat Development

2007 ◽  
Author(s):  
Tania Bhatia ◽  
G. V. Srinivasan ◽  
Sonia V. Tulyani ◽  
Robert A. Barth ◽  
Venkat R. Vedula ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Bond Coat ◽  
Room Temperature ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Pressure Steam ◽  
Non Line Of Sight

Environmental barrier coatings (EBCs) are being developed for silicon carbide (SiC) based composites and monolithic silicon nitride (Si3N4) to protect against the accelerated oxidation and subsequent silica volatilization in high temperature high-pressure steam environments encountered in gas turbine engines. It has been found that the application of EBCs developed for SiC-based composites (EBCSiC) to monolithic silicon nitride results in a loss of room temperature mechanical strength of the monolithic substrate. In this paper, we discuss the development of a bond coat system tailored for monolithic silicon nitride that helps retain the strength of the substrate. Some of the unique requirements and challenges associated with the processing of non-line-of-sight EBCs for Si3N4 will also be discussed. Preliminary results from coating of airfoils will be presented.

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.

In Search of Durable Sandphobic Thermal/Environmental Barrier Coatings for Rotorcraft Gas Turbine Engines

2021 ◽  
Author(s):  
Muthuvel Murugan ◽  
Anindya Ghoshal ◽  
Michael Walock ◽  
Luis G. Bravo ◽  
Rahul Koneru ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier
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