Novel thermal barrier coatings resistant to molten volcanic ash wetting

Conference Dates

June 24-29, 2018


Molten environmental deposits primarily emanating from volcanic ash pose a serious threat to aviation safety. When ingested into a jet engine, the volcanic ash melts and adheres to the surface of hot regions (i.e., combustion chamber, turbine blade, and nozzle guide vanes) of jet engines. Virtually, these hot zones in jet engines comprise a two-layer thermal barrier coating (TBCs). These ceramic TBCs provide thermal insulation to the underlying nickel-based super alloy substrate, but these coatings are more vulnerable to the damage caused by molten volcanic ash deposits. Particularly, in the pursuit of high output efficiency, turbine operating temperatures increasingly exceed 1250°C, leading to detrimental effects on the TBCs. Introducing rare-earth oxides (eg. Gadolinium oxide) into TBCs is regarded as one of the main migratory approach to prevent the damage by ash, because the infiltration silica-rich molten volcanic ash deposit is slowed down by crystallising the melt, preventing deeper infiltration into the coating. However, the initial phase of the damage progression of volcanic ash into the porous texture of TBC has become unavoidable. Here, we utilised thermal spray technology to produce a novel thermal barrier coating consisting of the mixture of the hexagonal boron nitride (h-BN, 30 vol.%) and yttria stabilized zirconia (YSZ, 70 vol. %) (BN-YSZ coating).

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