Phase Transformation of Al-Cu-Cr Quasicrystalline Coatings in the Plasma Spray Processes

The effects of substrate temperature during the low-power plasma spraying (2.5~8.0kW) and subsequent annealing on the phase transformation of Al-Cu-Cr quasicrystalline coatings were investigated. Compared with the original powder mainly composed of icosahedral I-Al₆₅Cu₂₄Cr₁₁ quasicrystalline phase and monoclinic θ-Al₁₃Cr₄, the coatings show an icosahedral quasicrystal I-Al₆₅Cu₂₄Cr₁₁ and its body-centered cubic approximate phase α-Al₆₉Cu₁₈Cr₁₃. XRD patterns indicated that, for identical spraying condition, a rise in substrate temperature resulted in an increase of the I/α peak intensity ratio in the coatings, and the crystalline phases of AlCu₄ and Al₈₆Cr₁₄ were observed in the coatings after annealing at 1113K for half an hour.