Copper Alloys Find Their Niche in Metal AM

A GRCop-42 heat exchanger

Due to its superior thermal conductivity, copper is one of the “hottest” metals for research and development in additive manufacturing. This is desirable in rockets and industrial applications such as electronics, where heat exchange is critical. Second only to silver among metals in its ability to conduct heat, copper is pound-for-pound significantly less expensive. Copper alloys provide enhanced mechanical properties along with that valuable conductivity.

Common copper alloys for AM include GRCop-42 and GRCop-84 (both are copper chromium niobium), C18150 (copper, chromium, zirconium), C18200 (copper chromium), and GlidCop (copper and alumina). The color of copper alloy powders is a soft pink, with finished AM parts displaying that classic, copper-color glow.
 
NASA pioneered the use of copper alloys forged components in the 1970s on the Space Shuttle Main Engine. GRCop (copper chromium niobium) metal powder was developed by NASA metallurgist David Ellis as an improvement on the earlier forged alloys and used with vacuum plasma spraying, a form of Direct Energy Deposition (DED) additive-manufacturing process that produces relatively simple, large structures.

When laser powder bed fusion (LPBF) became available, copper powder found its ideal match in advanced AM technology. Carried out in an airtight build chamber, LPBF is the manufacturing process that can deliver the extremely complex internal geometries being developed for the latest rocket combustion-chamber designs, or for cold-plate applications in electronics.
 
These AM-enabled complex geometries are of particular interest to engineers designing lighter-weight rockets with novel propulsion configurations for launch vehicles, hypersonics, and other applications. A rocket’s thrust chamber needs to have material properties that can withstand the thermal and pressure extremes of ignition. But because it is essentially functioning as a heat exchanger, the chamber must also withstand a surrounding flow of super-chilled rocket propellant. Such a fluctuating environment can be balanced with extreme precision by AM intricate cooling channels in the surrounding walls of the thruster—with geometries that cannot be achieved via any other type of manufacturing.
 

An internal segment of a GRCop-42 heat exchanger. The part showcases the design and print quality of the internal cooling channels used in the heat exchanger.

NASA is continuing to advance the technology for AM using copper alloys for combustion chambers. Several U.S. vendors have been established to provide these designs as a commercial printing service, and NASA is using vendor-supplied chambers as part of development testing under various programs.