scholarly journals Recession of Environmental Barrier Coatings under High-Temperature Water Vapour Conditions: A Theoretical Model

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4494
Author(s):  
Peng Jiang ◽  
Cheng Ye
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Theoretical Model ◽  
Water Vapour ◽  
Gas Flow ◽  
Gas Diffusion ◽  
Corrosion Process ◽  
Gas Pressure ◽  
Environmental Barrier ◽  
Corrosion Kinetics

Rare-earth disilicates are the major material used on the top layer of environmental barrier coating (EBC) systems. Although rare-earth disilicates are highly resistant to water vapour, corrosion due to water vapour at high temperature is still one of the main reasons of failure of EBC systems. In this study, a corrosion model of ytterbium disilicates in water vapour at high temperature was derived, based on the gas diffusion theory. Using this theoretical model, we studied the evolution rule of the corroded area on the top layer of the EBC under gas flow at high temperature. The influence of the various parameters of the external gas on the corrosion process and the corrosion kinetics curve were also discussed. The theoretical model shows that the increase in gas temperature, gas flow velocity, water partial pressure, and total gas pressure accelerate coating corrosion. Among these factors, the influence of total gas pressure on the corrosion process is relatively weak, and the effect of the continuous increase of the gas velocity on the corrosion process is limited. The shape of the corrosion kinetics curve is either a straight or parabolic, and it was determined by a combination of external gas parameters.

scholarly journals Mechanical–Chemical Coupling Effects on an Environmental Barrier Coating System under High-Temperature Water Vapour Conditions

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5907
Author(s):  
Dingjun Li ◽  
Fan Sun ◽  
Cheng Ye ◽  
Peng Jiang ◽  
Jianpu Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Theoretical Model ◽  
Water Vapour ◽  
Corrosion Process ◽  
Environmental Barrier ◽  
High Temperature Water ◽  
Water Vapour Concentration ◽  
Water Vapour Diffusion ◽  
Corrosion Zone ◽  
Temperature Water

The degradation mechanisms for environmental barrier coatings (EBCs) under high-temperature water vapour conditions are vital for the service of aero-engine blades. This study proposes a theoretical model of high-temperature water vapour corrosion coupled with deformation, mass diffusion and chemical reaction based on the continuum thermodynamics and the actual water vapour corrosion mechanisms of an EBC system. The theoretical model is suitable for solving the stress and strain fields, water vapour concentration distribution and coating corrosion degree of an EBC system during the water vapour corrosion process. The results show that the thickness of the corrosion zone on the top of the EBC system depended on water vapour diffusion, which had the greatest influence on the corrosion process. The top corroded area of the rare-earth silicate EBC system was significantly evident, and there was a clear dividing line between the un-corroded and corroded regions.

Relation between Synthesis Process, Microstructure and Corrosion Resistance of Two Yttrium Silicates

2008 ◽  
Vol 595-598 ◽  
pp. 923-931 ◽  
Author(s):  
Emilie Courcot ◽  
Francis Rebillat ◽  
Caroline Louchet-Pouillerie
Keyword(s):  
Corrosion Resistance ◽  
Rare Earth ◽  
High Temperature ◽  
Water Vapour ◽  
Synthesis Process ◽  
Structural Components ◽  
Moist Atmosphere ◽  
Silica Scale ◽  
Degree Of Crystallization ◽  
Silicon Based

Silicon-based ceramics are among the main candidates for high temperature structural components in aeronautic applications. One key drawback of silicon-based ceramics for these applications is the volatilization of the protective silica scale, in moisture and the resulting ceramic recession. Therefore, the further use of these ceramics components depends on the development of external protection against water vapour attack. Some of the most promising materials seem to be rare earth silicates. Based on much richer data in the bibliography, the purpose of this work is to investigate the influence of two yttrium silicates elaboration processes on both the capability to crystallize and the corrosion resistance in an oxidative moist atmosphere at high temperature. Taking into account the material’s morphology, composition and degree of crystallization, the composition (Y2SiO5 or Y2Si2O7) and the preferable synthesis process are discussed.

scholarly journals Stochastic Analysis of the Gas Flow at the Gas Diffusion Layer/Channel Interface of a High-Temperature Polymer Electrolyte Fuel Cell

2018 ◽  
Vol 8 (12) ◽  
pp. 2536 ◽  
Author(s):  
Dieter Froning ◽  
Junliang Yu ◽  
Uwe Reimer ◽  
Werner Lehnert
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Polymer Electrolyte ◽  
Gas Flow ◽  
Gas Diffusion ◽  
Stochastic Methods ◽  
Model Parameters ◽  
Efficient Operation ◽  
Multi Scale ◽  
Meso Scale

Gas diffusion layers (GDLs) play a significant role in the efficient operation of high-temperature polymer electrolyte fuel cells. They connect the electrodes to the gas channels of the bipolar plate by porous material with a meso-scale geometric structure. The electrodes must be sufficiently supplied by gases from the channels to operate fuel cells efficiently. Furthermore, reaction products must be transported in the other direction. The gas transport is simulated in the through-plane direction of the GDL, and its microstructure created by a stochastic model is equivalent to the structure of real GDL material. Continuum approaches in cell-scale simulations have model parameters for porous regions that can be taken from effective properties calculated from the meso-scale simulation results, as one feature of multi-scale simulations. Another significant issue in multi-scale simulations is the interface between two regions. The focus is on the gas flow at the interface between GDL and the gas channel, which is analyzed using statistical methods. Quantitative relationships between functionality and microstructure can be detected. With this approach, virtual GDL materials can possibly be designed with improved transport properties. The evaluation of the surface flow with stochastic methods offers substantiated benefits that are suitable for connecting the meso-scale to larger spatial scales.

DISPERSED PHASE VELOCITY IN A HIGH-TEMPERATURE GAS FLOW

2019 ◽  
Vol 23 (4) ◽  
pp. 319-328
Author(s):  
Dmitry V. Nesterovich ◽  
Oleg G. Penyazkov ◽  
Yu. A. Stankevich ◽  
M. S. Tretyak ◽  
Vladimir V. Chuprasov ◽  
...  
Keyword(s):  
High Temperature ◽  
Phase Velocity ◽  
Gas Flow ◽  
Dispersed Phase ◽  
High Temperature Gas

Passive Auto-Focus Algorithm for Correcting Image Distortions Caused by Gas Flow in High-Temperature Measurements of Surface Phenomena

2012 ◽  
Vol 17 (4) ◽  
pp. 379-384 ◽  
Author(s):  
Krzysztof Strzecha ◽  
Tomasz Koszmider ◽  
Damian Zarębski ◽  
Wojciech Łobodziński
Keyword(s):  
High Temperature ◽  
Gas Flow ◽  
Temperature Measurements ◽  
Surface Phenomena ◽  
Auto Focus ◽  
High Temperature Measurements

Abstract In this paper, a case-study of the auto-focus algorithm for correcting image distortions caused by gas flow in high-temperature measurements of surface phenomena is presented. This article shows results of proposed algorithm and methods for increasing its accuracy.

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