Researchers of Missouri S&T explored imaging and modelling techniques to prevent porosity in metal laser powder bed fusion (LPBF) such as surface pores. In their paper published under the titled ‘Pore elimination mechanisms during 3D printing of metals,’ the researchers describe their application of in-situ high-speed and high-resolution synchrotron x-ray imaging technology and multi-physics modelling to research and better understand porosity issues found in 3D printed metal parts.
They studied the effect of thermocapillary force on pore dynamics in different locations of the entire melt pool and developed a sophisticated force map. They discovered that pores move not only according to temperature and thermocapillary force but that they also drag force caused by the melt flow.
Even more impressive, they found that the high thermocapillary force can overcome the drag force, which prevents the forming of pores during printing. Furthermore, the researchers conducted experiments in non-powder-based 3D printing techniques to show that the pores behave similarly.
The researchers concluded that thermocapillary force could be used to eliminate pores while LPBF was in progress and that the process is not limited to a specific alloy system. The findings could also have positive implications for applications like laser polishing, laser cladding, welding, melt spinning, nuclear reactors and chemical reactors.