Engineers at NASA's Marshall Space Flight Center in Huntsville, Ala., tested NASA's first 3D printed rocket engine prototype part made of two different metal alloys through an innovative advanced manufacturing process. NASA has been making and evaluating durable 3D printed rocket parts made of one metal, but the technique of 3D printing, or additive manufacturing, with more than one metal is more difficult.
“It is a technological achievement to 3D print and test rocket components made with two different alloys,” says Preston Jones, director of the Engineering Directorate at Marshall. “This process could reduce future rocket engine costs by up to a third and manufacturing time by 50 percent.”
Engineers at Marshall, led by senior engineer Robin Osborne, of ERC, Inc. of Huntsville, supporting Marshall's Engine Components Development and Technology branch, low-pressure hot-fire tested the prototype more than 30 times during July to demonstrate the functionality of the igniter. The prototype, built by a commercial vendor, was then cut up by University of Alabama in Huntsville researchers who examined images of the bi-metallic interface through a microscope. The results showed the two metals had inter-diffused, a phenomenon that helps create a strong bond.
A rocket engine igniter is used to initiate an engine’s start sequence and is one of many complex parts made of many different materials. In traditional manufacturing, igniters are built using a process called brazing which joins two types of metals by melting a filler metal into a joint creating a bi-metallic component. The brazing process requires a significant amount of manual labor leading to higher costs and longer manufacturing time.
For this prototype igniter, the two metals — a copper alloy and Inconel — were joined together using a unique hybrid 3-D printing process called automated blown powder laser deposition. The prototype igniter was made as one single part instead of four distinct parts that were brazed and welded together in the past. This bi-metallic part was created during a single build process by using a hybrid machine made by DMG MORI in Hoffman Estates, Illinois. The new machine integrated 3D printing and computer numerical-control machining capabilities to make the prototype igniter.