A new trick that helps re-create complex microscopic structures of some stainless steel gives its 3-D-printed sibling a huge shot in the arm.
Most metal 3-D printers use a process called laser sintering to make solid objects. A surface covered in metal powder is scanned by a laser to melt, and fuse, small grains into a solid 2-D shape. Then the surface drops, more powder is added, and the process repeats to build a 3-D object. The result is a piece of intricate metalwork, but one often lacking some of the properties seen in an item created using regular manufacturing techniques.
The reason, as Science notes, is that the approach doesn’t create the microstructure achieved through processes normally used to process alloys, like heat treatment. The result of such traditional techniques is a grain structure—a microscopic arrangement of the metallic crystals—with distinct boundaries that stop the propagation of flaws in the material, yet still allow it to be worked into shapes. In other words, it gives the material strength and ductility.
In the case of 316L stainless steel, which is used in marine applications, 3-D printing usually means trading off strength against ductility. Now, though, a team from Lawrence Livermore National Laboratory has developed an approach that lets it use a regular laser sintering printer, yet control the rapid heating and fusing so that those useful grains can be carefully grown.
Writing in Nature Materials, the team explains that they have such fine control over the growth of those structures that they can create custom grains unlike those seen after regular processing. That gives rise to components with similar ductility to regular stainless steel but twice the strength, and three times that of some previous 3-D-printed types.
It’s an exciting advance, and it could help improve the production of marine and aerospace components. But it’s also part of a wider set of developments that appear to be recasting 3-D printing as a truly useful manufacturing tool. To find out more about the other new breeds of metallic 3-D printing, read our recent feature on the startup Desktop Metal.