Characterization of Directed Energy Deposition Additively Manufactured GRCop-42 Alloy

GRCop is an alloy family constructed of copper, chromium, and niobium and was developed by NASA for high heat flux applications. The first of its kind, GRCop-84, was specifically designed for the environments seen by channel cooled main combustion chamber liners. To further increase thermal conductivity while maintaining material strength characteristics, the percentage of alloying elements were cut in half and GRCop- 42 was developed. In recent years, NASA has successfully additively manufactured GRCop with comparable material characteristics to wrought GRCop using a Laser Powder Bed Fusion (L-PBF) process. Benefits of this process include fabrication of intricate cooling channels as well as a decrease in manufacturing lead times. However, there are some disadvantages in using this process. The nature of the powder bed process imposes a strict volume constraint and requires an excessive amount of material inventory. A Directed Energy Deposition (DED) process addresses these limitations while also speeding up the manufacturing process. With little data on how DED performs manufacturing GRCop-42, an investigation into the mechanical properties was conducted. More specifically, Blown Powder Deposition (BPD, a DED process), was used to compare material properties to that of the PBF manufactured GRCop-42. Through porosity and density testing, comparable material was produced by both the DED and L-PBF process with the DED manufactured material having slightly more porosity. However, comparing at similar developmental stages, the DED well outperformed the L-PBF. Tensile testing concluded that L-PBF produced significantly stronger parts over the DED material in the “as-printed” form. Among all testing, more variation was seen in the DED material pointing to a more inconsistent process. However, with further development, DED demonstrates the capability of producing material of the same quality of that of L-PBF at lower material costs, faster build speeds, and provides an AM method better suited for large-scale applications