According to the Lianyi Chen, assistant professor of mechanical engineering who is leading the research, “using metal 3D printing, we haven’t been able to consistently produce parts with the same high quality and reliability as those made by conventional methods, which means we have big concerns about using 3D-printed parts for critical or load-bearing applications where failure isn’t an option.”
In laser powder bed fusion, as the laser interacts with the powdered material, the powder surface heats to boiling temperature and creates hot vapor. This vaporization creates pressure that pushes down on the pool of melting material causing droplets to splash out. These droplets can cause unpredictable defects in the printed part, he said.
The new technique involves using ceramic nanoparticles to control instabilities in the laser powder bed fusion additive manufacturing process that cause defects. By coating the metal powder with ceramic nanoparticles, the researchers could control these defects. Using both high-speed synchrotron x-ray imaging and theoretical analysis, the researchers found that the nanoparticle coating stabilized the melt pool, preventing liquid droplets from spraying out and forming the larger spatters.
“When we introduced the nanoparticles, we found that they made the liquid droplets almost have an armor on the surface, so that when they collided, they didn’t merge together,” says Minglei Qu, a graduate student and lead author of the study.
According to Chen, the technique could lead to improvements in other processes such as laser polishing, laser cladding, welding, casting, and fluid stability control, among others.
