This SBIR Phase II effort will continue to develop and then scale up a novel manufacturing process based on severe plastic deformation (SPD) to refine and enhance the microstructure-properties of bulk tungsten. Tungsten, with its many unique characteristics, plays an important role in nuclear reactors including for the nuclear thermal propulsion (NTP) engine. The refractory metal, however, still has a number of shortcomings which still need to be addressed. These include a high ductile-to-brittle transition temperature (DBTT), low ductility and poor fracture toughness, low machinability and fabricability, low-temperature brittleness, radiation-induced brittleness, and a relatively low recrystallization (RX) temperature compared to its operation temperature. The use of W above its RX temperature interminably can be unsafe because its mechanical properties decrease in such an environment. Low-temperature brittleness also imposes restrictions on the application of W as a structural material. And, given its high hardness, high brittleness, and poor machinability, W parts can be very costly and time-consuming to manufacture. Past efforts to increase the ductility of W were primarily directed on alloying, grain refinement, extreme working, area reductions, impurity reductions, and heat treatments. While ductile W currently exists in wire form (e.g., filaments) through extensive working and area reduction, this approach is clearly not practical for applications where bulk size parts are needed. Thus, a compaction deformation method under both controlled pressure and temperature along with compressive and shear deformation in a hot die system will be demonstrated here to "ductilize" W.
This program should result in higher performance, more affordable manufacture of very high temperature hot zone structures and components such reactor fuel elements, radiation shields, hot gas path nozzles, and thrusters for diverse spacecraft and rocket propulsion systems including the nuclear thermal propulsion (NTP) engine made from more ductile bulk tungsten. Other NASA applications include hot structures and heat shields (i.e., thermal protection system) for reusable launch vehicles and/or aircraft engines.
Better, more affordable manufacture of: 1) very high temperature (hot zone) structure/parts for spacecraft/rocket propulsion, gas turbines, power generation (nuclear, fossil), and chemical process/industrial furnace equipment; 2) armaments and munitions (e.g., kinetic energy penetrators); and 3) tooling for semiconductors, sputtering targets (e.g., flat panel displays), and medical imaging.