Effect of NiCrAlY content on mechanical and dielectric properties of NiCrAlY/Al₂O₃ composite coatings

NiCrAlY/Al₂O₃ (NA) composite coatings were fabricated by a plasma spraying method with nickel-based (NiCrAlY) particles as an absorber and Al₂O₃ as a matrix. The phase composition and microstructure of these coatings were characterized by X-ray diffraction and scanning electron microscopy, respectively. The mechanical and dielectric properties of the NA composite coatings with different NiCrAlY contents were investigated. The results indicate that the non-metallic phases (i.e., corundum and chromium corundum) and the metal phase nickel generate in the composite coatings. The bending resistance and fracture toughness all increased with increasing NiCrAlY content. The real part and the imaginary part of permittivity both changed in the frequency range of 8.2-12.4 GHz, and they reached the maximum values at NiCrAlY content of 25% mainly due to various amounts, solidified shapes and distributions of nickel in the composite coatings.