EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In the past decade, the industrial interest for Laser Powder Bed Fusion (LPBF) additive manufacturing (AM) process has significantly grown and the technology is on track for full scale production. Yet some key mechanisms of the process are not fully understood. To create a new layer, the powder is deposited on a previously solidified layer. This volume of powder defines the available amount of material for the next solidified layer. The particle size distribution of the powder is an important parameter as it influences not only the laser/material interaction but also the spreading behaviour of the powder. In this study we investigate the use of different particle size distribution of an AISI 420 martensitic stainless steel using powder characterization tools as a rotating drum, a tapped density analyser and an experimental bench for spreading behaviour. This bench allows controlled recoating speed and layer height. The effect of the particle size distribution on the spreading behaviour and the properties of the formed layer has been investigated. A finer powder has shown an aggravating cohesive behaviour resulting in inhomogeneous powder layers. Powder blends has been developed as a proposal for improved layer homogeneity, density and spreading behaviour. This powder blend results from the mixture of two powders with different particle size distribution. The sizes of constitutive powders have been varied in order to study the effect of size ratio. It is shown that, in the blend, the density increases with the weight percentage of fine powder until 40 wt%. Beyond this value, the increase of fine powder doesn’t further increase the density. By changing the weight percentage of fine powder in the blend, a transition has been found between cohesive and non-cohesive behaviour. The requirements for design of a powder blend are discussed according to a part manufacturing perspective.