Abstract
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.
Highlights
IntroductionContinuous silicon carbide fibre-reinforced silicon carbide ceramic matrix composite
Continuous silicon carbide fibre-reinforced silicon carbide ceramic matrix composite (SiC/SiCCMC) has been widely used in high-temperature environments owing to its high-temperature resistance, excellent mechanical properties, and low density [1,2,3]
A theoretical model forexperimental predicting the corrosion of rare-earth disilicates in highIn addition, under the same conditions, thebehaviour experimental results of another group differ temperature water vapour was established based on the gas diffusion theory
Summary
Continuous silicon carbide fibre-reinforced silicon carbide ceramic matrix composite CMC) has been widely used in high-temperature environments owing to its high-temperature resistance, excellent mechanical properties, and low density [1,2,3]. SiC/SiC CMC is gradually replacing the traditional nickel-based superalloy as the main structure and load-bearing part of combustion chambers and high-temperature turbine blade of aeroengines. To reduce corrosion of the ceramic matrix composite (CMC) induced by water vapour in aeroengines [4], it is necessary to prepare an environmental barrier coating (EBC) system on its surface [5]. Rare-earth disilicates are the most promising EBC material. Rare-earth disilicates are selectively corroded by high-temperature water vapour, which is one of the main causes of failure of EBC systems [6].
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