Influence of beam diameter on Laser Powder Bed Fusion (L-PBF) process

Abstract

The use of large beams in the Laser Powder Bed Fusion (L-PBF) process has been receiving increasing attention for the past few years and may widen the dissemination of this technology in the industry, as well as help increase the production volume. In this paper, a detailed comparison is presented between a usual 80 μm diameter Gaussian laser spot and a 500 μm diameter top-hat laser beam. The following benefits of a large and homogeneous beam could be demonstrated: (1) a moderate increase of productivity by reducing the number of scan lines, (2) a nearly total suppression of spatters and powder bed degradation (local loss of powder homogeneity caused by the redeposition of spatters) due to the low volume energy densities carried out and the limitation of deleterious vaporization effects, (3) the manufacturing of near fully dense Inconel 625 parts, especially in the hatching zones. Last, the occurrence of larger thermal effects induced by the large beam L-PBF was discussed by comparing two distinct definitions of the laser energy density: at a local (melt pool) scale, and at a global (the whole manufactured part) level.