Effect of powder recycling on anisotropic tensile properties of selective laser sintered PA2200 polyamide

Abstract

During the process of selective laser sintering (SLS) Polyamide-12 (PA12), most powders are not sintered and just support the printed parts. It is an economic way to reuse the un-sintered powders. In this work, it is to investigate the effects of powder recycling on uniaxial tensile properties of PA2200 samples printed in XY/Y, YZ/Y and YZ/Z building orientations, as well as on the resulting microstructural characteristics and crystal structures of the PA2200 powders. The results show that the powder shape, size and distribution have little difference between the virgin and recycled powders, but more fractured, small and smooth sphere powders are distributed in adhered powders. The crystal structures of the powders do not change but the thickness of the crystallite first increase and then decrease with increasing recycling times. The tensile strength and Young’s modulus of the SLS samples display no significant anisotropy, and first increase and then decrease with the increase of powder recycling times. With powder recycling times increasing, the elongation at break of the samples built in XY/Y and YZ/Y directions first increases and then decreases, but decreases for the all samples in YZ/Z direction. The pores and torn dimples occur depicted in the fracture surface, and pores increase with increasing recycling times. There are more un-molten powders distributed on the fractured surfaces of the parts in YZ/Z direction in comparison to those of other directions.