ORNL Combines 3D Printing and Metal Casting to Create Stronger Components

As the hype over 3D printing begins to die down a bit, expectations of its potential have changed and become more realistic. It’s still going to change manufacturing, and indeed it already has. But it’s now less trumpeted as the magical new technology that’s going to wipe out all other manufacturing methods – instead, it’s being looked at more frequently as a technology that can be used alongside other technologies, strengthening them instead of replacing them.

Hybrid machines that combine 3D printing with CNC machining are becoming more common, but CNC is far from the only manufacturing method that has been combined with 3D printing to create new processes. Investment casting is an ancient manufacturing method; in fact, it’s one of the oldest methods still in existence. Its effectiveness has kept it widely in use, but it too has been enhanced by 3D printing in a number of cases.

A recent example of the two technologies working together involved the creation of an airplane seat frame that was far more lightweight than those created using more typical manufacturing methods. The process was also faster than casting alone – although casting is an effective process, it’s a time-consuming one with several steps, including the creation of a wax model, the coating of that model with ceramic, and the burning out of the original model in an oven to create a mold – followed by the pouring of molten metal into the mold to create the final part.

3D printing makes the creation of the initial mold cheaper and faster, and as Oak Ridge National Laboratory (ORNL) recently discovered, the combination of 3D printing with traditional casting also results in stronger, more damage-tolerant components. In a recently published paper entitled “Damage-tolerant metallic composites via melt infiltration of additively manufactured preforms,” a team of ORNL researchers details how they used a two-step process to fabricate strong composite metal parts.

The process involved 3D printing a steel lattice and then pouring an aluminum alloy over it, in a variation of traditional metal casting. Tension tests on parts with 39 vol% steel showed an order of magnitude improvement over the strain to failure of the aluminum alloy alone.

“Inspection of the as-tested tensile specimens suggested that this exceptional damage tolerance is a result of the interpenetrating structure of the constituents,” the researchers state. “These results together demonstrate that this infiltration processing route avoids problems with intermetallic formation, cracking, and poor resolution that limit current fusion-based additive manufacturing techniques for printing metallic composites.”

The process was developed for automotive and other applications that require simultaneous optimization of both thermal and mechanical properties.

“This scalable processing strategy can be used to fulfill specific component functions, giving materials designers unprecedented control over both microstructure and material properties,” said Amit Shyam of ORNL, an author on the paper.

In this case, additive manufacturing and traditional casting strengthen each other while strengthening the parts they create. Authors of the study, from ORNL as well as Rice University, include Alexander E. Pawlowski, Zachary C. Cordero, Matthew R. French, Thomas R. Muth, J. Keith Carver, Ralph B. Dinwiddie, Amelia M. Elliott, Amit Shyam, and Derek A. Splitter. Discuss in the ORNL forum at 3DPB.com.

[Source/Images: ORNL]