LLNL found liquid metal ejection via PBFAM

High-speed images of a common laser-based metal 3D printing process, coupled with newly updated computer models, have revealed the mechanisms behind material redistribution, a phenomenon that leads to defects in printed metal parts.

In a study published by Scientific Reports (link is external), Lawrence Livermore National Laboratory (LLNL) scientists combined ultrafast imaging of melt-pool dynamics with high-resolution simulations, finding that particles of liquid metal ejected from the laser’s path during the powder-bed fusion additive manufacturing (PBFAM) process — commonly called “spatter” — is caused by the entrainment of metal particles by an ambient gas flow.

When spatter particles fly out of the laser’s path and land back on the parts, they can contaminate the powder bed and affect the build quality of a layer, thereby leading to roughness, porosity and lack of fusion in finished metal parts.

The high-speed video images were captured with three kinds of cameras, including a sensor capable of up to 10 million frames per second.

The video images were compared to high-fidelity simulations that were previously validated for other additive manufacturing applications, revealing that the incline of the melt pool influenced the direction of the spatter.

The Laboratory Directed Research and Development (LDRD) program funded the study.