Effects of scanning direction and remelting on surface morphology and wettability of laser powder bed fusion Ti6Al4V mono- and bi-layers

Abstract

Laser powder bed fusion manufactured (LPBF-ed) porous Ti6Al4V materials have attracted much attention in the biomedical industry due to their functional properties. In this study, mono- and bi-layer LPBF-ed surfaces were prepared to better understand the dynamics of pore formation and the impact of one layer on the next. The powder spreading direction was regarded as the direction here, and then LPBF-ed surfaces could be defined as x- and y- scanned ones. As for LPBF-ed monolayers, the y-scanned surface was rougher than the x-scanned surface, in good agreement with the surface profile of the powder layer extracted from the numerical work. The finding indicates that the morphology of LPBF-ed layers is affected by the relationship between the powder spreading direction and the laser scanning direction. Besides, surfaces scanned with varying laser numbers were used to analyze the effect of the remelting phenomenon, which confirmed that additional laser scans prone to reshaping the pore distribution. The wettability was further studied to investigate their biocompatibility initially. No obvious changes were observed between the CAs of the x- and y-scanned surfaces, whereas the remelting accelerated the surface stabilization of LPBF-ed monolayers. LPBF-ed bilayers were much rougher and more hydrophilic compared to monolayers, and the same result could be verified on xy- and yx-scanned surfaces. The study contributes to better control pores and even performance within LPBF-ed samples by investigating the surface morphology and wettability of LPBF-ed layers.