SBIR Phase I: Highly Processable High Performance Ni Superalloys for Heat Exchanger Applications

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This Small Business Innovation Research Phase I project will design and develop a new high performance Ni superalloy material for high temperature heat exchanger applications. The alloy design will leverage existing QuesTek efforts on Ni superalloy modeling, design, and prototyping, including multicomponent thermodynamic and kinetic models of microstructural stability and precipitation behavior. The key microstructural design concept is based around achieving the superior strength, high thermal conductivity, and elevated thermal-mechanical strength (fatigue resistance) required of high performance heat exchanger materials via a combination of L12-type and DO22-type precipitation. In Ni superalloys these two types of precipitates nucleate and grow in a highly interactive manner ("compact morphology"). QuesTek will harness this "self-assembly" behavior by understanding the detailed chemical (thermodynamic) and elastic (stress) interactions during the controlled co-evolution of these precipitates. The goal is a breakthrough in heat exchanger material temperature capability with significantly higher service temperature capabilities (and thermal efficiencies) than previously achievable.The broader impact/commercial potential of this project is to keep pace with improving system technology by producing higher-temperature and lower-weight heat exchangers that are increasingly in demand. State-of-the-art heat exchangers are fundamentally limited by the availability of next generation superalloys in two ways. First, the weight of heat exchangers is limited by the thickness of existing materials. Current operating temperatures require thick gauge material to withstand severe thermal cycle stresses resulting in a heavy component. Materials that could withstand higher stresses at elevated temperatures would enable thinner sheets resulting in weight savings in addition to better heat transfer across thinner sections. In addition, thermal conductivity and thermal efficiency are enhanced at higher operating temperatures. The life and operating temperature of heat exchanger components are limited by the temperature capability of currently-available materials in sheet form. Improvements in material performance would have direct benefits to high temperature heat exchanger performance.