Materials data is a moving target in additive manufacturing. New alloys and compounds are still being tested, and existing materials often perform in very different ways after being passed through a 3D printing process than they did using traditional manufacturing methods.
In some cases, 3D printing developments have helped improve existing materials. We reported a few weeks ago on research that will not only make it possible to print with high-strength aluminum, but that could actually allow the previously unweldable material to be welded.
Now, scientists at Lawrence Livermore National Laboratory in California have developed a way to 3D print with stainless steel that results in materials that are up to three times stronger than steels created using traditional techniques.
“In order to make all the components you’re trying to print useful, you need to have this material property at least the same as those made by traditional metallurgy,” said LLNL materials scientist and lead author Morris Wang. “We were able to 3D print real components in the lab with 316L stainless steel, and the material’s performance was actually better than those made with the traditional approach. That’s really a big jump. It makes additive manufacturing very attractive and fills a major gap.”
Stainless steel is a popular material for manufacturing across many different industries. Creating a printable version of the alloy has proven difficult, however, because the final material is so porous that it is much weaker and likely to fracture.
Lawrence Livermore had previously developed a process that combined lasers and rapid cooling to fuse metal alloy particles densely together. A computer-driven version of that process allows them to control the material from the nanoscale to micron scale, including structures in the steel that can prevent fractures. The team was able to print a low-carbon steel called 316L.
Tests have shown that under some conditions the material is three-times stronger than conventionally made steel.
“This microstructure we developed breaks the traditional strength-ductility tradeoff barrier,” Wang said. “For steel, you want to make it stronger, but you lose ductility essentially; you can’t have both. But with 3D printing, we’re able to move this boundary beyond the current tradeoff.”
The next phase of research will involve more simulation and applying these techniques to other alloys. According to Lawrence Livermore:
The eventual goal … is to use high-performance computing to validate and predict future performance of stainless steel, using models to control the underlying microstructure and discover how to make high-performance steels, including the corrosion-resistance. Researchers will then look at employing a similar strategy with other lighter weight alloys that are more brittle and prone to cracking.
The Lawrence Livermore team worked with engineers from Ames National Laboratory, Georgia Tech, and Oregon State. You can read more about this work in the journal Nature Materials.