Humidity control in laser powder bed fusion using titanium alloy powder for quality assurance of built parts and reusability of metal powder

This study investigated the influence of oxygen concentration and humidity in a laser power bed fusion system on the building aspects of titanium alloy powder for the quality assurance of built parts and the reusability of metal powders. Controlling the humidity inside the building chamber was found to be more important than controlling the oxygen concentration to prevent the oxidation of the built part and metal powder. Low oxygen concentration and humidity resulted in high circularity and a narrow size distribution of spatter particles. The oxidation of spatter particles was accelerated with an increase in the oxygen and humidity levels within the building chamber, particularly with an increase in humidity. High oxygen concentration and humidity caused a change in the Marangoni convection, resulting in the formation of defects inside the built part. Oxygen was captured by spatter particles or built parts during the liquid phase, and the degrees of influence of the oxygen concentration and humidity in the building chamber on the capture of oxygen were similar. The oxygen content of the built part had a greater effect on the mechanical properties of the built part, as compared with the hydrogen content. The Charpy impact strength was sensitive to the capture of oxygen and humidity by the built part and could effec-tively help understand the building aspects under slightly different building environments. This study demon-strates that maintaining the oxygen and humidity conditions below 10 ppm is indispensable for building chambers.

Automated summary

This study investigated the influence of oxygen concentration and humidity on the building aspects of titanium alloy powder in a laser power bed fusion system. It found that controlling humidity in the building chamber is more important than controlling oxygen concentration to prevent oxidation. Low oxygen concentration and humidity resulted in high circularity and narrow size distribution of spatter particles. High oxygen concentration and humidity caused defects in the built part due to changes in Marangoni convection. Maintaining oxygen and humidity levels below 10 ppm is crucial for building chambers.