Effect of process parameters on the surface topography formation in precision additive metal manufacturing

Abstract

The typical surface topography of parts produced by additive manufacturing differs from those produced by conventional manufacturing. During the powder bed fusion process, spatter particles may eject from the melt pool due to multi-physics phenomena. These spatter particles can have an impact on the part quality as large spatter particles that land on the top of the powder layer may shield the powder from the laser beam, resulting in lack of fusion porosity and increases surface roughness. The measurement of spatter is important to understand the process and to predict the performance of parts. In this study, the effect of laser power and scan speed on the surface topography of the top surface of Maraging steel grade 300 is investigated. The parts were produced by an in-house powder bed fusion machine LM-Q with a powder size distribution of 15 µm to 45 µm. A surface topography comparison was made between several samples which were produced by different process parameters regarding laser power and laser speed, leading to different Archimedes' densities. The surface topography was measured by a confocal microscope. The topography data were pre-processed with bi-cubic interpolation and least square plane subtraction. For the parameter evaluation, Sand F-filters with appropriate nesting index settings were used. Several conventional and surface texture parameters are evaluated in order to investigate the correlation with the production parameters.