scholarly journals Delayed Formation of Thermally Grown Oxide in Environmental Barrier Coatings for Non-Oxide Ceramic Matrix Composites

Coatings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 6 ◽  
Author(s):  
Hagen Klemm ◽  
Katrin Schönfeld ◽  
Willy Kunz
Keyword(s):  
Intermediate Layer ◽  
Elevated Temperatures ◽  
Failure Mechanisms ◽  
Ceramic Matrix Composites ◽  
Thermally Grown Oxide ◽  
Oxide Ceramic ◽  
Gap Formation ◽  
Environmental Barrier ◽  
Sic Particles ◽  
Thermally Grown

The oxidation and corrosion behavior at elevated temperatures of a SiCF/SiC(N) composite with two plasma-sprayed environmental barrier coating (EBC) systems were studied. After both processes, the formation of a silica-based thermally grown oxide (TGO) layer was observed. The formation of this TGO caused two principal failure mechanisms of the EBC. Firstly, spallation of the EBC induced by stresses from volume expansion and phase transformation to crystalline SiO2 was observed. Water vapor corrosion of the TGO with gap formation in the top region of the TGO was found to be a second failure mechanism. After a burner rig test of the Al2O3-YAG EBC system, this corrosion process was observed at the TGO surface and in the volume of the Al2O3 bond coat. In the case of the second system, Si-Yb2Si2O7/SiC-Yb2SiO5, the formation of the TGO could be delayed by introducing an additional intermediate layer based on Yb2Si2O7 filled with SiC particles. The SiC particles in the intermediate layer were oxidized and served as getter to reduce the permeation of oxidants (O2, H2O) into the material. In this way, the formation of the TGO and the failure mechanisms caused by their formation and growth could be delayed.

scholarly journals Analysis of failure mechanisms of oxide - Oxide ceramic matrix composites

2021 ◽  
Author(s):  
Karthikeyan Ramachandran ◽  
Subhashree Leelavinodhan ◽  
Christian Antao ◽  
Antony Copti ◽  
Cantalapiedra Mauricio ◽  
...  
Keyword(s):  
Failure Mechanisms ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Oxide Ceramic ◽  
Matrix Composites

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.

Compressive Creep Testing of Thermal Barrier Coated Nickel-Based Superalloys

2010 ◽  
Author(s):  
Ventzislav G. Karaivanov ◽  
William S. Slaughter ◽  
Sean Siw ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Mechanical Properties ◽  
Creep Strain ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Thermally Grown Oxide ◽  
Tensile Creep ◽  
Thermal Barrier ◽  
Elemental Distribution ◽  
Compressive Creep ◽  
Thermally Grown

Turbine airfoils have complex geometries and during service operation are subjected to complex loadings. In most publications, results are typically reported for either uniaxial, isothermal tensile creep or for thermal cyclic tests. The former generally provide data for creep of the superalloy and the overall performance, and the later provide data for thermal barrier coating (TBC) spallation as a function of thermally-grown oxide (TGO) thickness, surface roughness, temperature, and thermal mismatch between the layers. Both tests provide valuable data, but little is known about the effect of compressive creep strain on the performance of the superalloy/protective system at elevated temperatures. In conjunction with computational model development, laboratory-scale experimental validation was undertaken to verify the viability of the underlying damage mechanics concepts for the evolution of TBC damage. Nickel-based single-crystal Rene´ N5 coupons that were coated with a ∼150–200 μm MCrAlY bond coat and a ∼200–240 μm 7-YSZ APS topcoat were used in this effort. The coupons were exposed to 900, 1000, and 1100°C, for periods of 100, 300, 1000 and 3000 hours in slotted silicon carbide fixtures. The difference in the coefficients of thermal expansion of the Rene´ N5 substrate and the test fixture introduces thermally induced compressive stress in the coupon samples. Exposed samples were cross-sectioned and evaluated using scanning electron microscopy (SEM). Performance data was collected based on image analysis. Energy-dispersive x-ray (EDX) was employed to study the elemental distribution in the TBC system after exposure. To better understand the loading and failure mechanisms of the coating system under loading conditions, nanoindentation was used to study the mechanical properties (Young’s modulus and hardness) of the components in the TBC system and their evolution with temperature and time. The effect of uniaxial in-plane compressive creep strain on the rate of growth of the thermally grown oxide layer, the time to coating failure in TBC systems, and the evolution in the mechanical properties are presented.

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