Using surface roughness as an indicator of laser powder bed fusion part quality

Purpose Laser powder bed fusion additive manufacturing constructs layered parts, with each layer consisting of a series of laser tracks. Track and layer surface roughness are primarily governed by laser parameters, which also control the formation of other defects such as porosity. Despite this correlation, surface roughness is not used as an indicator of internal part quality. This study aims to link surface roughness and surface features to porosity content and melting behavior for multiple alloys. Design/methodology/approach Multiple materials were fabricated using diverse parameter sets altering laser power, scan speed and hatch spacing. The top surface of these parts was characterized ex situ using high-resolution laser scanning confocal microscopy. The scans were used to generate height maps and calculate surface roughness parameters. The surface metrics were correlated with porosity characteristics obtained using metallography and light optical microscopy. Findings The results of this study show that, in general, as surface roughness decreases, both maximum pore size and pore count decrease, while relative density increases. The height maps also reveal unique surface features linked to different melting behaviors. Originality/value This study provides evidence to support the causal and correlative relationship between surface condition and part quality. This study provides a deeper understanding of the interplay between surface roughness and internal defects than what has been previously studied. This study extends existing non-destructive part evaluation by linking surface and porosity formation mechanisms.