Identifying main contamination factors of laser powder bed fusion oxidation-sensitive powders

Recycling and reusing powders in the laser powder bed fusion (LPBF) process can reduce production costs, but may cause unintended oxidation, and in some cases, the oxygen content exceeds the standards. In a first study, oxygen levels of AlSi10Mg samples manufactured from powders which suffered different manipulations inside and outside the LPBF system were compared. Powders were used in closed-loop up to 5 cycles. Some samples were manufactured with powders which have been heated by their proximity with the scanning zones, and recycled multiple times, although other samples were manufactured from solely recycled powders. A clear rise in oxygen levels (+ 120 ppm in five productions) was observed for samples from powders which have previously suffered from heat, compared to non-multiple heated powders (+ 10 ppm). It demonstrates the major role of the laser scanning heat in the oxidation of the surrounding powder during the parts manufacturing. A second study evaluates the ability of two strategies to reduce the number of generated spatters with Ti6Al4V powders. The first strategy consisted in reducing the scanned surface, and the second strategy increased the dwell time between two successive layers. Reducing the scanned surface seems to reduce significantly the number of spatters, but further quantitative studies are needed. Interesting behaviours regarding spatters landing were observed and discussed.

Automated summary

Recycling and reusing powders in the LPBF process can reduce production costs, but may lead to unintended oxidation. The oxygen content of AlSi10Mg samples manufactured from different manipulated powders was compared in a study. It was found that powders heated by proximity with scanning zones had higher oxygen levels compared to non-heated powders. Another study evaluated strategies to reduce spatter generation with Ti6Al4V powders, and reducing the scanned surface was found to significantly reduce the number of spatters.