Phase Assemblage of Al-Cu-Cr Quasicrystalline CoatingsSprayed by Low Power Plasma

摘要

Al-Cu-Cr quasicrystalline (QC) coatings were deposited ontomild steel Q235A substrate by low power plasma spraying.The plasma torch was designed such that the powders can beinjected axially (parallel to the axis of the plasma arc) into theregion between the anode and cathode, and the carrier gaseswere transferred to the plasma flame, so the heating efficiencyof the powders is greatly increased and the velocity ofparticles is much higher than an externally-fed powder system.The Al-Cu-Cr QC coatings were sprayed via this newtechnique at different plasma power (3~7kW) by controllingthe secondary plasma gases (H2 and N2) flow or changing thearc current. The results show that, the original powder wasmainly composed of a dominant icosahedral quasicrystallinephase I-Al65Cu24Cr11 and a minor monoclinic θ-Al13Cr2.However, besides these two phases, body-centered cubic α-Al69Cu18Cr13, the approximant to quasicrystal I-Al65Cu24 Cr11,has been detected in as-sprayed coatings. On the other hand,peak intensity of QC phase I-Al65Cu24Cr11 decreased and thatof crystalline phases (θ-Al13Cr2 or α-Al69Cu18Cr13) increasedas the plasma power was increased.