Particle size effects on chemistry and structure of Al-Cu-Fe quasicrystalline coatings

Gas atomized Al63Cu25Fe12 powders of varying size fractions were plasma sprayed onto hot (similar to 600 degrees C) and cool (similar to 25 degrees C) substrates using Mach I and subsonic plasma gun configurations, The chemical composition and phase contents of coatings were determined, Furthermore, coatings were annealed in vacuum at 700 degrees C for 2 h to observe phase changes, It was found that finer particles (e.g., <25 mu m) tend to vaporize Al during spraying, which shifts the coating composition away from the quasicrystalline (psi) single-phase region in the Al-Cu-Fe phase diagram, Coatings deposited on hot substrates were denser, richer in the psi phase, and harder than the corresponding coatings deposited onto cool substrates.