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.

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 Water vapor and CMAS corrosion tests of Si/Y2SiO5 Thermal and Environmental Barrier Coating

2021 ◽  
Author(s):  
Qi Zhang ◽  
Xueqin Zhang ◽  
Zhuang Ma ◽  
Ling Liu ◽  
Yanbo Liu ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Corrosion Test ◽  
Environmental Barrier ◽  
Alkali Salt ◽  
High Temperature Water ◽  
Environmental Barrier Coating ◽  
Barrier Coating ◽  
High Temperature Steam ◽  
Temperature Water

Abstract Thermal and environmental barrier coating (TEBC), the up-to-date concept, is introduced to protect silicon-based ceramics matrix composites (CMC) from not only high temperature water vapor but also the alkali salt from volcanic ash and dust suspending in atmosphere. Because both of high temperature steam and CMAS will make Si-based CMC deteriorate rapidly. By executing the corrosion test against high temperature water vapor, we find that Si/Y2SiO5 double-layer TEBC can effectively protect SiCf/SiC CMC from water vapor at 1300 ℃ for over 205 hours. Almost all Y2SiO5 transform into Y4.67(SiO4)3O after corrosion test. It is also found that in CMAS corrosion test, the reaction zone formed between CMAS and Y2SiO5 layer prevents the mutual diffusion of elements in CMAS and Y2SiO5 layer. The apparent activation energy of reaction between CMAS and Y2SiO5 in 1200~1300℃ temperature ranges is calculated to be 713.749kJ/mol. These findings provide a reference to select appropriate materials for TEBC.

scholarly journals The Effect of High-Temperature Water Vapour on Degradation and Failure of Hot Section Components of Gas Turbine Engines

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1061
Author(s):  
Kuiying Chen ◽  
Dongyi Seo ◽  
Pervez Canteenwalla
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Water Vapour ◽  
Alternative Fuels ◽  
Aviation Industry ◽  
High Hydrogen ◽  
Barrier Coatings ◽  
High Temperature Water ◽  
The Impact ◽  
Temperature Water

For the past decade, the aviation industry has been adopting sustainable aviation fuels (SAF) for use in aircraft to reduce the impact of aviation on climate change. Also, some nations look to SAF as an option for energy security for their military fleets. Understanding the critical impact of alternative fuel sources on hardware will provide the gas turbine industry with strategic options in sustainability and maintainability of the existing and new fleets. The alternative fuels with high hydrogen/carbon ratio (H/C) (such as synthetic paraffinic kerosenes (SPK)) could produce more water vapour content than the conventional jet fuels upon combustion, and this increased water vapour level could exert a significant impact over the long-term durability on hot section components such as the substrate blades, oxidation resistant coatings, thermal barrier coatings (TBCs), environmental barrier coatings (EBCs), resulting in an accelerated degradation of the turbine components. The possible detrimental effect of high-temperature water vapour on degradation and lifespan of hot section components was examined. Examples were specifically given on degradation and spallation of thermally grown oxides (TGO), formation of non-protective oxides and ceramics topcoats in TBCs. Results show that water vapour can lead to volatilization of TGO (Al2O3), and is responsible for the formation of non-protective oxides in both Pt-modified β-NiAl and MCrAlY coatings, leading to their early spallation. However, water vapour does not appear to directly affect the ceramic topcoat of the TBC. For EBCs coated on SiC-based substrates, the substrate recession via silica (TGO) volatilization was reviewed. These EBCs were observed undergoing degradation in highly hostile environments, e.g., constantly operating under high temperatures, pressures, and velocities condition in the presence of water vapour steam. The review intends to provide a perspective of high-temperature water vapour effect on the EBCs’ topcoat properties such as durability, degradation, crack nucleation and crack growth, and possible guidance for mitigating these degradation effects.

scholarly journals Anisotropic diamond etching through thermochemical reaction between Ni and diamond in high-temperature water vapour

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Masatsugu Nagai ◽  
Kazuhiro Nakanishi ◽  
Hiraku Takahashi ◽  
Hiromitsu Kato ◽  
Toshiharu Makino ◽  
...  
Keyword(s):  
High Temperature ◽  
Water Vapour ◽  
High Temperature Water ◽  
Temperature Water ◽  
Thermochemical Reaction
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