Investigation and Control of Smoke Phenomenon in Electron Beam Powder Bed Fusion of a Novel γ-TiAl alloy

Abstract

Powder smoke phenomena – a cloud of metallic powder created by electrostatic repulsion – is an inherent issue that has been observed in many high temperature alloys processed by Electron Beam Powder Bed Fusion (EPBF). To date the majority of research addressing this issue has focused on machine modification and process manipulation to prevent overcharging of powder particles, but little has investigated the effects of controlling powder characteristics. A recent body of work from the University of Tohoku has proposed ball milling as a method for mechanically working the surfaces of gas atomized IN718 and TiAl4822 powders to alter their surface oxide layers, thus improving their electrical conductivity. Utilizing microscopy, thermophysical and electrical property analysis, an assessment of the ball milling mechanisms responsible for smoke mitigation have been investigated using a novel γ-TiAl – Ti-48Al-2Nb-3Zr-0.2B – with superior oxidation resistance.