Preparation and characterization of high emissivity high-entropy lanthanum aluminate coatings

Abstract In order to prepare high-temperature-resistant and high-emissivity coatings, this paper prepares high-entropy La(Fe 0.2 Ni 0.2 Mn 0.2 Ti 0.2 Al 0.2 )O 3 powder using solid-state synthesis with La 2 O 3 , Al 2 O 3 , NiO, Mn 3 O 4 , TiO 2 , and Fe 2 O 3 as raw materials. After spray drying and high-temperature sintering, the obtained high-entropy La(Fe 0.2 Ni 0.2 Mn 0.2 Ti 0.2 Al 0.2 )O 3 agglomerated powder is used to prepare a composite coating on the surface of Gh2747 alloy by means of atmospheric plasma spraying. The microstructure and morphology of the agglomerated powder before and after sintering, adhesion strength, thermal shock resistance, and radiation properties of the coating are tested. The results show that: perovskite-type high-entropy lanthanum aluminate ceramic powder is successfully prepared, and the spherical shape and fluidity of the agglomerate after granulation meet the requirements of atmospheric plasma spraying. The prepared high-entropy La(Fe 0.2 Ni 0.2 Mn 0.2 Ti 0.2 Al 0.2 )O 3 coating has a porosity of 11.3%, excellent adhesion strength, and a normal total emissivity of up to 0.86 at 1000°C. After 5 cycles from 1150°C to room temperature, delamination occurs in the coating.