Effect of feedstock characteristics on the dielectric and microwave absorption properties of plasma sprayed NiCrAlY/Al2O3 coatings

NiCrAlY/Al2O3 coatings were fabricated by low power plasma spraying with two different feedstock powders. The microstructure, phase composition and dielectric properties of the coatings were investigated. The result showed that the particle melting degree and the connection of NiCrAlY in the coatings were closely related to the feedstock characteristics, such as particle size and morphology, which played an important role in the microstructure and dielectric properties. The enhanced complex permittivity of the coating deposited from dried and crushed powder is attributed to interfacial polarization and conductance loss. Compared with the coating prepared from milled and agglomerated powder, the reflection loss of the coating fabricated with dried and crushed powder reaches -20.5 dB at 9.9 GHz and the eligible microwave absorption (below -10 dB) can be obtained in the frequency range 8.7-10.8 GHz.