Session BB4.1

1:30 PM BB4.1
ABRASIVE WEAR BEHAVIOR OF QUASICRYSTALLINE-IRON ALUMINIDE COMPOSITE COATINGS. Daniel Sordelet, Matthew Besser, Ames Laboratory, Iowa State University, Ames, IA.

Quasicrystals are a new class of materials which exhibit previously forbidden rotational symmetries (e.g., 5-fold) and long range aperiodic translational order. Since their discovery in 1984, quasicrystals have been studied not only because of their fascinating atomic structures, but as a result of their useful physical and mechanical properties, which include low surface energy, low coefficients of friction, high hardness, and low thermal and electrical conductivities. Our group has been very active in developing Al-Cu-Fe based quasicrystalline surface coatings using conventional plasma and HVOF spraying techniques. High density, crackfree coatings have been difficult to produce due to the low thermal conductivity and brittleness of the Al₆₅Cu₂₃Fe₁₂ quasicrystalline phase. Therefore, experiments were performed to form composite coatings of the quasicrystalline phase with an iron aluminide (B2 structure) phase. The latter was selected because separate work has shown that the material is easy to deposit as a dense, relatively ductile thermal spray coating . The objective of this study was to decrease the porosity, cracking, and brittleness of quasicrystalline coatings through the addition of the iron a1uminide phase. Quasicrystalline powders were blended with iron aluminide (0, 1, 5, 10, 20, 100, v/o) powders and plasma sprayed in air and in argon at 300 torr. Fine (+25$\mu$m, -45$\mu$m) and coarse (+45$\mu$m, -75$\mu$m) size fractions were evaluated. Abrasive wear behavior was examined using a modification of the ASTM G-65 rubber wheel abrasion test. Results show that material removal during abrasion is decreased by the addition of iron aluminide. However, a particularly interesting observation is that the addition of only 1 v/o iron aluminide produced the most abrasive wear resistant coatings. This effect was observed with all four coating conditions. A proposed explanation involving a change in wear mechanism from brittle fracture to plastic deformation along with maintaining coating hardness will be presented.