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 high erosion resistance. Therefore, applying this material as a coating is an effective method for preventing erosion. In this study, a mixture of Ti and Ni powders was subjected to a mechanical alloying process. Then, the mechanical and structural properties of the coating fabricated by vacuum plasma spraying and laser plasma hybrid spraying were examined. The results of this study are summarized as follows: (1) Mechanically alloyed powders suitable 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 spraying. This means that nickel and titanium were alloyed while they were passed 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 made by laser plasma hybrid spraying of mechanically alloyed powder was approximately 40 times as high as that of titanium alloy. This high erosion resistance was obtained at low relative fluence compared with that of the coating made from the simple mixture. This coating can prevent degradation of the interface, because a high fluence induces the formation of a brittle intermetallic compound at the interface. (C) 2001 Elsevier Science B.V. All rights reserved.