Fabrication of NiTi intermetallic compound coating made by laser plasma hybrid spraying of mechanically alloyed powders

NiTi intermetallic compounds not only have shape memory effects but also hi gh erosion resistance. Therefore, applying this material as a coating is an effective method for preventing erosion. In this study, a mixture of Ti an d Ni powders was subjected to a mechanical alloying process. Then, the mech anical and structural properties of the coating fabricated by vacuum plasma spraying and laser plasma hybrid spraying were examined. The results of th is study are summarized as follows: (1) Mechanically alloyed powders suitab le for plasma spraying were obtained under the conditions of 2 mass% methyl alcohol as a process control agent and 72 ks alloying duration. (2) A NiTi intermetallic compound coating was directly fabricated by vacuum plasma sp raying. This means that nickel and titanium were alloyed while they were pa ssed through a plasma flame. The erosion resistance of this coating is more than 20 times as high as that of the coating made from a simple mixture of nickel and titanium powders. (3) The erosion resistance of the coating mad e by laser plasma hybrid spraying of mechanically alloyed powder was approx imately 40 times as high as that of titanium alloy. This high erosion resis tance was obtained at low relative fluence compared with that of the coatin g made from the simple mixture. This coating can prevent degradation of the interface, because a high fluence induces the formation of a brittle inter metallic compound at the interface. (C) 2001 Elsevier Science B.V. All righ ts reserved.