Vacuum Plasma Spray Forming of Shape-Memory Alloy Components

MRi proposes to develop manufacturing NiTinol (shape memory alloys, SMA) processes based on vacuum plasma spray consolidation of NiTinol powders into near- net shapes. Shape-memory alloys (SMA's) have emerged as materials with unique thermal and mechanicalproperties could be used to reconfigure the shape of the rotor blades or for actuation and reconfigurability in other applications.MRi is proposing using vacuum plasma spray consolidation to eliminate many of the cast and wrought defects, while offering an opportunity to be able to shape NiTinol. In the proposed investigation NiTinol powders would be fed into plasma jets that areoperating in low pressure inert gas atmospheres where the heated powders are deposited onto mandrels that would shape the deposits. In Phase I, MRi would demonstrate the feasibility of the vacuum plasma spray process, in terms of process effects on theshape-memory behaviors of the NiTinol materials, including the effects on Ms, Mf, As and Af transition temperatures and stress-strain vs. temperature characteristics. The initial investigations would conclude with the fabrication of 1/4 scale vacuum plasmaspray formed NiTinol prototypes (tubes up to 12 inches in length, 3 inches outside diameter, and 0.25 inch in tube thickness and flat forms that would be characterized thermally and mechanically. SMA's such as NiTinol (NiTi) are in many actuators for flow control, electronic switching and now in biomedical applications for minimally invasive surgery implants and stents. Improved shaping capability concurrent with improved metallurgical structurescould advance more of these applications. Additionally, DoD applications have also emerged related to smart surfaces, where the aero control surfaces such as helicopter rotor blades could be shaped in flight using SMA's. A spray forming capability wouldmake the shaping of such blades more practical. The proposed technology, if developed would enable lower cost, more reliable shapes to be made. Also should vacuum plasma spray forming be developed as a viable manufacturing technique, other applicationsusing difficult to form materials, such as refractory metals or graded structures could be realized. Applications for such spray formed parts include rocket thrusters, fuel cells, batteries and other power cell applications.