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

• Published in: Journal of materials processing technology Vol. 311; p. 117817
• Main Authors: Yamaguchi, Mitsugu, Kushima, Kotaro, Ono, Yushi, Sugai, Tomohiro, Oyama, Tomohiro, Furumoto, Tatsuaki
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2023
• Subjects: Additive manufacturing; Humidity; Laser-based powder bed fusion; Oxygen concentration; Reusability; Titanium alloy; Titanium alloy; Laser-based powder bed fusion; Oxygen concentration; Reusability; Additive manufacturing; Humidity
• ISSN: 0924-0136
• DOI: 10.1016/j.jmatprotec.2022.117817

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 effectively help understand the building aspects under slightly different building environments. This study demonstrates that maintaining the oxygen and humidity conditions below 10 ppm is indispensable for building chambers. [Display omitted] •The reusability of Ti–6Al–4V powders and the quality of built parts under different building environments were evaluated.•Low oxygen concentration and humidity resulted in high circularity and narrow size distribution of spatter particles.•Oxidation of spatter particles was accelerated at high oxygen concentration and humidity.•Mechanical properties of the built parts were significantly affected by oxygen content in the built parts.•Oxygen and humidity levels below 10 ppm in the building chamber are indispensable to ensure the quality of the built parts.