Materials critical to many important applications in aerospace and energy production must be able to withstand extreme conditions such as high temperatures and tensile stress without failure. Now, an MIT-led team of engineers reports a simple, inexpensive way to enhance one of the key materials used in such applications today.
Additionally, the team believes their general approach, which involves 3D printing of metal powders reinforced with ceramic nanowires, could be used to improve many other materials. “There is always an urgent need to develop more robust materials suitable for extreme environments. We believe this approach has great potential for other materials in the future.” Battelle Energy Alliance Professor of Nuclear Engineering, MIT Department of Materials Science and Engineering (DMSE) Professor Ju Li said.
Li, who is also affiliated with the Materials Research Laboratory (MRL), is one of three corresponding authors of a paper on this work published April 5. Additive manufacturing. The other corresponding authors are Professor Wen Chen from the University of Massachusetts Amherst and Professor A. John Hart from the Department of Mechanical Engineering at the Massachusetts Institute of Technology.
The paper’s co-first authors are Emre Tekoğlu, a postdoc in the Department of Nuclear Science and Engineering (NSE) at MIT; Alexander D. O’Brien, a graduate student at NSE; and Jian Liu of the University of Massachusetts Amherst. Other authors include Baoming Wang, DMSE postdoc at MIT; Sina Kavak, Istanbul Technical University; Yong Zhang, MRL research specialist; So Yeon Kim, DMSE graduate student; Shitong Wang, NSE graduate student; and Duygu Agaogullari, Istanbul Technical University.
Towards better performance
The team’s approach started with Inconel 718, a popular “superalloy,” a metal that can withstand extreme conditions such as 700 degrees Celsius (about 1,300 degrees Fahrenheit). The team wrote that they milled commercial Inconel 718 powder with a small amount of ceramic nanowires to “uniformly decorate the nanoceramics on the surface of the Inconel particles.”
The resulting powder is then used to create parts through laser powder bed fusion, a form of 3D printing. The process involves printing thin layers of powder, each of which is exposed to a laser that passes through the powder, melting it into a specific pattern. Another layer of powder is then laid on top and the process is repeated, with the laser moving to melt the pattern of the new layer and bond it to the layer below. The entire process can produce complex 3D parts.
The researchers found that parts made with the new powder had significantly less porosity and cracks than parts made with Inconel 718 alone. This, in turn, results in the parts becoming stronger, along with many other advantages. For example, they are more malleable (or stretchable) and have better resistance to radiation and high temperature loading.
Additionally, the process itself is not expensive because “it can be used with existing 3D printers. Just use our powder and you get better performance,” Li said.
Xu Song, an assistant professor at the Chinese University of Hong Kong who was not involved in this work, commented: “In this paper, the authors propose a new method for printing metal matrix composites reinforced with Inconel 718. [ceramic] Nanowires. The in-situ dissolution of the ceramic caused by the laser melting process increases the heat resistance and strength of Inconel 718. Additionally, in-situ reinforcement reduces grain size and eliminates defects. Future 3D printing of metal alloys, including modification of high-reflectivity copper and fracture suppression of high-temperature alloys, could clearly benefit from this technology. “
huge new space
Li said the work “could open up huge new space in alloy design” because the ultra-thin 3D printed metal alloy layers cool much faster than bulky parts made using traditional melt-solidification processes. As a result, “many of the chemical composition rules that apply to batch casting don’t seem to apply to this kind of 3D printing. So we have a much larger compositional space to explore adding ceramics to the base metal.”
Emre Tekoğlu, one of the main authors of the book Additive manufacturing The paper states: “This work was one of the first we decided on, so it is very exciting to get these results in real life. There is still a lot of room for exploration. We will continue to explore new Inconel composite material formulations , ultimately developing materials that can withstand more extreme environments.”
Alexander O’Brien, another lead author, said: “The precision and scalability of 3D printing opens up new possibilities for materials design. Our results are an exciting early step in this process and will certainly have important implications for the future of nuclear energy.” , aerospace, and the design of all energy generation.”
This work was supported by Eni SpA through the MIT Energy Initiative, the National Science Foundation, and ARPA-E.