Powder Bed Charging during Electron Beam Additive Manufacturing

Abstract

Electrons injected into the build envelope during powder-bed electron-beam additive manufacturing can accumulate on the irradiated particles and cause them to repel each other. These electrostatic forces can grow so large that they drive the particles out of the build envelope in a process known as “smoking”. In the present work, a model of powder bed charging is formulated and used to develop criteria that predict the conditions under which the powder bed will smoke. These criteria suggest dependences on particle size, pre-heat temperature, and process parameters that align closely with those observed in practice.