Texture of inclined up-facing surfaces in laser powder bed fusion of metals

Abstract Considerable surface texture is one of the typical drawbacks of laser powder bed fusion (LPBF). Especially up-facing inclined surfaces suffer from insufficient quality, due to the combination of the staircase effect (also called stair-stepping effect), attached powder particles and elevated edges (edge effect). In this work, the contribution of the edge effect to the topography of up-facing inclined surfaces is investigated in detail for the first time. Moreover, the effect of contour scanning was evaluated on up-facing surfaces over the whole range of inclinations, from horizontal to vertical. The edge effect was found to play a dominant role for surfaces with a low inclination angle, especially when contour scanning is used. A suitable scanning strategy can thus be determined for each surface inclination. In the present study, an optimization of scanning strategy allowed a significant improvement of the inclined surface quality. The arithmetical mean height of the roughness profile Ra could be reduced up to 52% for low inclinations, 20% for high inclinations and 32% for vertical walls.