Yb2 Si2 O7 Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

2018 ◽  
Vol 102 (3) ◽  
pp. 1507-1521 ◽  
Author(s):  
Kang N. Lee
Keyword(s):  
Bond Coat ◽  
Chemical Modifications ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Oxidation Rates ◽  
Long Life

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.

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.

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