Correlations of laser scanning parameters and porous structure properties of permeable materials made by laser-beam powder-bed fusion

Laser-beam powder bed fusion (LB-PBF) of metals is an additive manufacturing (AM) method currently being pursued in numerous industries. In this study, the effect of scan strategy, laser spot size, and hatch distance on the pore structure of additively manufactured permeable stainless steel materials was systematically studied through the analysis of material permeability, pore size distribution, porosity, and surface morphology. When the hatch distance is wide and laser power is low, two kinds of pores are formed and were studied. The first one is pores located between laser-melted tracks, the second type is pores generated inside the laser-melted tracks. Scan strategy and laser spot size have no obvious effect on the porosity, but they affect the powder attached on the surface, the permeability, and the pore size of the permeable material. Hatch distance plays an important role in controlling the material properties. When the hatch distance is larger than 0.13 mm, the effect of powder attached on the surface on the pore structure of the permeable material is weakened, and the permeability increases significantly. By optimizing these parameters, permeable materials with pore sizes ranging from 2.6 to 13.7 µm and a thickness of 0.89 mm were fabricated. To illustrate the potential of the method, for the first time an additively manufactured planar permeable-dense metallic membrane substrate with internal flow channels was fabricated, which is a center piece of a new compact modular integrated membrane reformer system.