Tailoring and investigation of defined porosity properties in thin-walled 316L structures using laser-based powder bed fusion

Process engineering applications, which require a defined mass transport, call for thin-walled structures with a defined open porosity. Powder bed fusion by a laser beam (PBF-LB) is investigated as a potential manufacturing method using stainless steel 316L to produce such structures. The total porosity was determined by weighing and volume measurement. The influence of the process parameters laser power, scan speed and hatch distance on porosity was investigated by means of a design of experiments (DoE) approach using a central composite design (CCD). A statistically significant regression model was developed to allow a prediction of the porosity values within the design space. To determine the distribution and size of porous sections, computed tomography and a microscope in transmitted light mode were used as well. Permeability was also analyzed. Within the design space, a permeability coefficient of 2258.26 E-12 m(2) was achieved with a maximum porosity value of 19.00%. With the help of the CT analysis, it was determined that for area laser energy densities between 0.625 and 0.744 J/mm(2), the average pore size from 4728.57 to 9841.38 mu m(2) can be adapted.