Effect of laser incidence angle on surface roughness and fatigue properties of PBF-LB/316L

Powder bed fusion using a laser beam (PBF-LB/M) is a widely utilized additive manufacturing technique known for its ability to produce complex geometries with high precision. However, there are numerous factors that can influence the properties of components manufactured by this process. One scarcely investigated factor is the laser incidence angle, which refers to the orientation and positioning of a component relative to the direction from which the laser interacts with the layer to be melted. This study examines the effect of the laser incidence angle on surface roughness and fatigue properties of 316L components. Although the laser incidence angle varies during layer-by-layer deposition, two initial part orientations were investigated. IA specimens were oriented toward the laser, while IT specimens were oriented away from it. This initial orientation establishes a trend in the effective incidence angle throughout the build. Results confirmed that the tendency of the laser incidence angle significantly affects surface roughness and can contribute to the formation or reduction of internal defects. Increased surface roughness and internal defects, particularly the latter, adversely impact fatigue strength, with internal defects playing a primary role in crack initiation in this study. Given that the initial part orientation establishes the effective laser incidence angle trend, careful positioning of components on the build plate is crucial for optimizing surface quality and fatigue properties of additively manufactured parts.