Importance of Reusing Metal Powders

Conversations about powder reuse often start with an aspiration to perform an all-encompassing design-of-experiment that reveals everything about powder reuse.

FREMONT, CA: Metal powders are costly, and depending on the geometry of the part, can be expensive as a result of unused and unrecycled powders. Not all metal powders are the same when it comes to reusability. Materials like Nickel alloys can be reused several times without much change to the powder particles' shape or other physical properties. Nickel alloys are usually non-reactive. Titanium alloy powders are reactive and accumulate oxygen with the rise in the number of reuse cycles, thereby, hurting the part strength. Besides, the process can impact the way that powders are contaminated. Electron Beam Melting (EBM) methods depend on a vacuum, and trace amounts of oxygen and moisture can stay in the system.

The print is first completed with virgin powder in the bin strategy, and the leftover powder that remains in the machine is unloaded and stored in a container labeled as reused.  Subsequent prints harness the remaining virgin powder from the same original batch, and any remaining powder goes into the reuse bin. When the virgin powder batch is depleted, the reuse powder is sieved and used to top up the machine. Any remainder of that already reused powder then goes into a second container. The process repeats until the particular number of reuses is reached, which will rely on the powder's contamination.

The virgin blend method uses virgin powder to top up used powder, therefore replenishing the missing elements in the used powder or diluting the levels of oxygen and other unwanted contaminants. This method is a combination of the bin method and the virgin blend method. The used powder is rejuvenated but low reuse powders are leveraged instead of virgin powder.

In a nutshell, there is no one-size-fits-all solution for experimenting with reusing metal powders. Experiments are costly and time-consuming, specifically when dealing with multiple factors and levels. Each experiment must be assessed, and the scope must be defined in advance to maximize effectiveness.