MIT researchers develop Inconel 718-ceramic nanowires powder for AM

A team of MIT-led engineers found a simple, inexpensive way to strengthen Inconel 718 with ceramic nanowires to be used in metal PBF AM processes. The team believes that their general approach could be used to improve many other materials. “There is always a significant need for the development of more capable materials for extreme environments. We believe that this method has great potential for other materials in the future,” said Ju Li, the Battelle Energy Alliance Professor in Nuclear Engineering and a professor in MIT’s Department of Materials Science and Engineering (DMSE).

Li, who is also affiliated with the Materials Research Laboratory (MRL), is one of three corresponding authors of a paper on the work that appeared in the April 5 issue of Additive Manufacturing. The other corresponding authors are Professor Wen Chen of the University of Massachusetts at Amherst and Professor A. John Hart of the MIT Department of Mechanical Engineering.

Co-first authors of the paper are Emre Tekoğlu, an MIT postdoc in the Department of Nuclear Science and Engineering (NSE); Alexander D. O’Brien, an NSE graduate student; and Jian Liu of UMass Amherst. Additional authors are Baoming Wang, an MIT postdoc in DMSE; Sina Kavak of Istanbul Technical University; Yong Zhang, a research specialist at the MRL; So Yeon Kim, a DMSE graduate student; Shitong Wang, an NSE graduate student; and Duygu Agaogullari of Istanbul Technical University. The study was supported by Eni S.p.A. through the MIT Energy Initiative, the National Science Foundation, and ARPA-E.

Better performance

The team’s approach began with Inconel 718, a popular “superalloy,” used in AM for applications that need to withstand extreme conditions such as temperatures of 700 degrees Celsius (about 1,300 degrees Fahrenheit). They mill commercial Inconel 718 powders with a small amount of ceramic nanowires, resulting in “the homogeneous decoration of nano-ceramics on the surfaces of Inconel particles,” the team wrote.

The resulting powder is then used to create parts via laser powder bed fusion. The researchers found that parts made this way with their new powder have significantly less porosity and fewer cracks than parts made of Inconel 718 alone. And that, in turn, leads to significantly stronger parts that also have a number of other advantages. For example, they are more ductile — or stretchable — and have much better resistance to radiation and high-temperature loading.

Plus, the process itself is not expensive because “it works with existing 3D printing machines. Just use our powder and you get much better performance,” said Li.

Huge new space

Li said the work “could open a huge new space for alloy design” because the cooling rate of ultrathin 3D-printed layers of metal alloys is much faster than the rate for bulk parts created using conventional melt-solidification processes. As a result, “many of the rules on chemical composition that apply to bulk casting don’t seem to apply to this kind of 3D printing. So we have a much bigger composition space to explore for the base metal with ceramic additions.”

Emre Tekoğlu, one of the lead authors of the Additive Manufacturing paper, added, “This composition was one of the first ones we decided on, so it was very exciting to get these results in real life. 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, concluded, “The precision and scalability that comes with 3D printing has opened up a world of new possibilities for materials design. 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.”