Porosity reduction by co-axial laser shock modulation of molten pool in powder-bed selective laser sintering: take widely-used stainless steel as an example

Powder-bed metal additive manufacturing is often troubled by high porosity issues resulted from gas trapping and keyhole instability. Here, this work is the first to propose a breakthrough approach: in-situ molten pool modulation by low-pulse-energy Co-axial laser shock. An additional pulsed laser beam is coupled to a selective laser sintering system to achieve low-porosity high-quality manufacturing of metal parts. In-situ monitoring shows the used laser shock method inhibits severe splashing and weakens materials ejection. Computed Tomography quantifies the volume, diameter, and sphericity of pores. Results show the porosity of the printed 316L stainless steel block is significantly reduced by 86 percent, achieving less than 0.016%. Meanwhile, the shape and size of pores are beneficially controlled. Under optimal process parameters, three-dimensional lattice structures were fabricated. Compression test results shows Co-axial laser shock effectively enhanced the geometric integrity of 3D structure, increasing the yield strength by 28.5% and energy absorption by 14%.