"Additive Manufacturing of GRX-810 for Calcium Hydride Based Thermal Management Systems" 

Kyle Petrosky, MSE PhD Candidate 

Advisor: Professor Mike Titus

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ABSTRACT

At elevated temperatures, metal hydrides undergo desorption and release hydrogen gas while absorbing large amounts of heat. This highly endothermic reaction removes significant thermal energy from surrounding structures and creates strong potential for metal hydrides in thermal management systems (TMS). Several challenges limit their practical use. Metal hydrides have poor thermal conductivity, which restricts heat transfer and reduces system performance. System designs must also accommodate hydrogen gas produced during desorption, which requires complex internal geometries and controlled flow paths. Many hydrides also react readily with air and water, which complicates handling and system integration. This thesis investigates calcium hydride (CaH₂) as the metal hydride and GRX-810 as the structural material for a metal hydride thermal management system. GRX-810 is an oxide dispersion strengthened (ODS) nickel-based superalloy that NASA developed for powder based additive manufacturing. This work evaluates different additive manufacturing methods to produce structures that address the challenges associated with metal hydride systems. The research quantifies the geometric capabilities and limitations of laser powder bed fusion (LPBF) of GRX-810, investigates processing parameters for GRX-810 using directed energy deposition (DED), and evaluates metal extrusion as a potential manufacturing approach. Metal extrusion produced components with a maximum relative density of 95.3 percent, which proved insufficient to contain reactive hydrogen producing metal hydrides without leakage when compared with the greater than 99 percent relative densities achieved with LPBF and DED. The study also evaluates methods to mix additives such as aluminum and zinc with CaH₂ to increase thermal conductivity. These additives increased thermal conductivity but also increased system mass and reduced desorption enthalpy, which limited their benefit. The results show that the most effective approach reduces the thickness of bulk metal hydride powder through complex container geometries that additive manufacturing processes such as LPBF and DED can produce.