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Strengthened Inconel 718 reduces porosity and cracking in AM


Inconel 718 is capable of withstanding the extreme application environments of aerospace and energy generation

A team of MIT-led engineers have developed an inexpensive method for strengthening Inconel 718 powder, a key additive manufacturing (AM) material used in the aerospace and energy industries.

Parts made using the strengthened powder have significantly less porosity and fewer cracks than parts made from standard Inconel 718.

Reported in Additive Manufacturingthe new method could also be used to improve many other materials, according to the researchers.

Inconel 718 is a popular “superalloy” key to many important applications in aerospace and energy generation due to being able to withstand extreme conditions such as high temperatures (e.g. 700°C) and tensile stresses without failing.

The new strengthening method sees commercial Inconel 718 powders milled with a small amount of ceramic nanowires, resulting in “the homogeneous decoration of nano-ceramics on the surfaces of Inconel particles,” according to the research team – comprising engineers from MIT, University of Massachusetts, UMass Amherst and Istanbul Technical University.

Xu Song, an assistant professor at the Chinese University of Hong Kong who was not involved in the work, explained: “In this paper, the authors propose a new method for printing metal matrix composites of Inconel 718 reinforced by [ceramic] nanowires. The in-situ dissolution of the ceramic that is induced by the laser melting process has enhanced the thermal resistance and strength of Inconel 718. Moreover, the in-situ reinforcements reduced the grain size and got rid of flaws.”

Shapes made with the new material

Beavers and other shapes were created using the newly strengthed version of Inconel 718 (Image: Alexander O’Brien)

The researchers found that parts built via laser powder bed fusion (LPBF) using the upgraded material exhibited considerably less porosity and fewer cracks than parts made of Inconel 718 alone. Such parts were in turn significantly stronger, more ductile, and had much better resistance to radiation and high-temperature loading.

The ceramic nanowire strengthening method could also be used to improve many other materials in the future: “Future 3D printing of metal alloys, including modification for high-reflectivity copper and fracture suppression for superalloys, can clearly benefit from this technique,” confirmed Song. 

What’s more, the strengthened powder works with existing 3D printing machines, meaning no additional integration efforts are required by industrial AM users to deploy it in their processes. 

Remarking on what’s next for the research team, Emre Tekoğlu, one of the lead authors of the Additive Manufacturing paper, said, “This composition was one of the first ones we decided on…there is still a vast exploration space. We will keep exploring new Inconel composite formulations to end up with materials that could withstand more extreme environments.”

Alexander O’Brien, another lead author, added: “Our results here are an exciting early step in a process that will surely have a major impact on design for nuclear, aerospace, and all energy generation in the future.”

The work was supported by Eni S.p.A. through the MIT Energy Initiative, the National Science Foundation, and ARPA-E.

Image: Shutterstock/MarinaGrigorivna

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