Study on the Tribological Properties of Low-power Plasma-sprayed Al-Cu-Cr Quasicrystalline Coating

Al-Cu-Cr quasicrystalline coatings were prepared by low power plasma spraying with axially-fed powder system. The Al(65)Cu(20)Cr(15) powders were deposited oil AISI 1045 steel Substrate at the power ranged from 4.0 to 5.5 kW. The effects of H(2)/Ar flow ratio on the phase composition, microstructure and tribological properties of the as-sprayed coatings were investigated. The XRD results showed that the feedstock powders and as-sprayed coatings contained a predominant icosahedral quasicrystalline phase I-Al(65)Cu(24)Cr(11) and three minor crystalline phases, including a body-centered cubic alpha-Al(69)Cu(18)Cr(13), a monoclinic theta-Al(13)Cr(2) (i.e. Al(83)Cu(4)Cr(13)) and a hexagonal epsilon-Al(2)Cu(3). A qualitative analysis on the XRD patterns indicated that the volume fraction of any crystalline phase (a, epsilon or theta) in the coatings increased, while the quasicrystalline I-phase decreased with the rise of hydrogen (H(2)) content in the working gas. However, as increasing the plasma power, the friction and wear resistance of the coating were improved under the same dry sliding wear test conditions. The improvement of the wear resistance may be attributed to the high hardness of quasicrystal.