Metal Additive Manufacturing Conference 2018

Metal additive manufacturing (AM) processes like laser powder bed fusion (L-PBF) become a more and more frequently used fabrication method for complex shaped and highly functional metal parts in medical, aerospace and automotive industries. The feedstock used for these processes is atomized, spherically shaped metal powder which has to meet the highest requirements to ensure stability of the building process and consistent, reproducible product quality. Since the costs of powder materials are a significant cost factor of AM components, powder recycling strategies are an important opportunity to enhance the economic efficiency of the process. Primary feedstock characteristics (i.e. particle size distribution, morphology, bulk density, porosity) strongly depend on the powder manufacturer. Additionally, experiences has shown, that recycling strategies have a considerable influence on the characteristics and behaviour of the powder. VDI guideline 3405 (Page 2.3; Additive manufacturing processes, rapid manufacturing – Beam melting of metallic parts – Characterisation of powder raw material) is a basic procedure to characterise metal powders, but the recommended parameters do not provide sufficient information whether a powder is suitable for powder bed fusion processes or not. Powder rheology provides automated and reliable measurement methods of bulk material characteristics, which can point out also minor changes and establish a link to a predictable behaviour of metal powders. This study investigates powder rheology measurement methods (pressure drop method, weighted cohesion strength measurements, tensile strength measurements) and their possibility to predict proper behaviour of metal powders in AM processes.