This work investigates the effects of various processing parameters (laser power, scanning speed, hatch distance and beam offset) on the resultant inclined up-facing surface roughness of AlSi10Mg alloys produced by laser powder bed fusion (LPBF). A two-step approach, orthogonal test followed by the Doehlert matrix design (DMD) test is used to efficiently optimize the up-facing surface and contour parameters. The former method aims to determine the significance of variables while the latter one facilitates a rapid optimization. The results show that the interaction and interdependency among the parameters are of great significance to the obtainable surface roughness. Using a rational design of experiments, the optimized up-facing surface roughness of Ra of 5.4 μm is achieved. This is attributed to the elimination of the laser partition track and the reduction in irregularities at the edges of the parts. This work demonstrates an effective approach of experimental processing parameter optimization to improve the surface finish of LPBF parts.

To improve the surface quality of an aluminum alloy manufactured by additive manufacturing (AM), mechanical attrition treatment (SMAT) has been applied to the as-fabricated surface of the alloy produced by selective laser melting (SLM). The morphology and properties of the SMAT-treated surfaces have been investigated and detailed friction and wear tests have been conducted to evaluate the tribological behavior of the SMAT specimens under both dry and oil-lubricated conditions. The results demonstrate that SMAT is effective in improving the surface finish of the alloy by up to 87%, which also results in an increase in surface hardness of 23% to 29%. Ball-on-disc reciprocating wear tests show that under dry sliding conditions, SMAT for 10 min is effective in improving the wear resistance of the alloy by 25% to 65%, while increasing the SMAT time to 20 min and 30 min results in deteriorated wear resistance as compared to the as-SLM surface. However, under oil-lubricated conditions, SMAT for various times from 10 min to 30 min is effective in improving the wear resistance of the alloy by a factor of 2 to 3.5, depending on the SMAT time and contact loads. The results are discussed considering surface finish enhancement, surface and subsurface hardening effects and surface damage caused by SMAT.