Ti-based Quasicrystal Layers Produced by Plasma Thermal Spraying

摘要

Ti_(45)Zr_(38)Ni_(17)powders were thermally sprayed onto mild steel substrates in air and under a reduced pressure of argon. Two kinds of powder samples were used in this study. For one type the elemental powders were gently (manually) mixed in a vial, and for the other type they were mechanically alloyed by a planetary ball mill. Several kinds of oxides were formed after thermally-spraying the mechanically-alloyed powders in air. After spraying in a reduced pressure of argon, on the other hand, the coating layers obtained from the gently mixed powders consisted of the three elemental metals (Ti, Zr, Ni), but an amorphous phase primarily appeared in the thermally-sprayed mechanically-alloyed powders. This amorphous phase transformed into the icosahedral quasicrystal phase and a minor Ti2Ni-type crystal phase after annealing in vacuum at 828 K. The Vickers hardness and the contact angle with pure water for the quasicrystal layers were about 7 GPa and 92° respectively.