Surface texture and form characterization for powder bed additive manufacturing

Abstract

The surface quality obtained after laser powder bed additive manufacturing is one of the factors that limits the use of part without any surface treatment. The main reason of this situation is the stair effect form as a result of the layered nature of the process. Geometric and form errors on a component surface with a stair effect bring numerous risks, especially in terms of assembly operations, flow performance and fatigue resistance decrease. For this reason, the characterization of stair effect and the resultant surface texture is of critical importance. In this study, innovative test artifacts with flat, angled and curved faces were designed and produced with laser powder bed additive manufacturing of Inconel 625 material. Surface texture and form characterization studies were performed on the artifacts. By presenting the results for different features and dimensions, surface texture and form change trends due to geometric properties were obtained and the effects of the parameters were discussed. It has been observed that the contact measurements on curved surfaces caused by radius values are not sufficient to characterize the change in the entire surface at the short sampling and evaluation distance of the probe. Therefore, studies were performed with an optical profilometer for curved surfaces and stair effect was clearly examined. It was determined that the surface quality improved with increasing inclination angle, and also it worsened in convex and concave surfaces with increasing radius value. This can be explained as a result of the change in the inclination angle with the increased radius value. Furthermore, the effect of the inclination angle on the surface quality in additive manufacturing was found to be higher in convex geometry than in concave geometry.