College - Author 1

College of Engineering

Department - Author 1

Materials Engineering Department

Degree Name - Author 1

BS in Materials Engineering

College - Author 2

College of Engineering

Department - Author 2

Materials Engineering Department

Degree - Author 2

BS in Materials Engineering



Primary Advisor

Blair London, College of Engineering, Materials Engineering Department


Aerojet Rocketdyne is investigating the use of directed energy deposition (DED), an additive manufacturing process, to reduce cost and lead time for manufacturing complex rocket engine components for their RS-25 engines. JBK-75 and NASA-HR-1, two Fe-Ni-base, age-hardenable (γ′) superalloys, are used for nozzle structural jackets and hot gas manifolds. Currently, these parts are produced using traditional forging or casting methods followed by intensive machining operations. Additionally, these alloys were designed for use in the wrought condition and require a different set of post-processing heat treatments when produced using DED due to their dendritic, segregated microstructure in the as-built condition. Homogenization heat treatment is necessary to transform the dendritic structure into an equiaxed, homogenous structure prior to aging to achieve optimum properties. The team characterized a set of homogenization heat treatments with varying parameters to better understand how homogenization affects the alloys’ room temperature mechanical properties and microstructure. Characterization techniques used include metallography and tensile testing at room temperature. The heat treated JBK-75 DED samples all met or were close to the yield strength of wrought, heat treated JBK-75. Homogenization heat treatment time and temperature did not have a significant effect on the yield or tensile strength of JBK-75. The NASA-HR-1 DED samples were sensitive to artifacts of the DED process such as porosity and surface finish, as samples with high porosity and poor surface finish displayed poor ductility. All NASA-HR-1 samples exhibited poor strength and did not meet the strength of the wrought material. All homogenization heat treatments were successful in producing a homogeneous, equiaxed microstructure, but considerable grain growth occurred, which caused lower strengths for both alloys.