Air plasma-sprayed high-entropy (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 coating with high thermal protection performance

Abstract High-entropy rare-earth aluminate (Y 0.2 Yb 0.2 Lu 0.2 Eu 0.2 Er 0.2 ) 3 Al 5 O 12 (HE-RE 3 Al 5 O 12 ) has been considered as a promising thermal protection coating (TPC) material based on its low thermal conductivity and close thermal expansion coefficient to that of Al 2 O 3 . However, such a coating has not been experimentally prepared, and its thermal protection performance has not been evaluated. To prove the feasibility of utilizing HE-RE 3 Al 5 O 12 as a TPC, HE-RE 3 Al 5 O 12 coating was deposited on a nickelbased superalloy for the first time using the atmospheric plasma spraying technique. The stability, surface, and cross-sectional morphologies, as well as the fracture surface of the HE-RE 3 Al 5 O 12 coating were investigated, and the thermal shock resistance was evaluated using the oxyacetylene flame test. The results show that the HE-RE 3 Al 5 O 12 coating can remain intact after 50 cycles at 1200 °C for 200 s, while the edge peeling phenomenon occurs after 10 cycles at 1400 °C for 200 s. This study clearly demonstrates that HE-RE 3 Al 5 O 12 coating is effective for protecting the nickel-based superalloy, and the atmospheric plasma spraying is a suitable method for preparing this kind of coatings.