Evaluation of 316L deposition parameters for the reducing stair-case effect of laminated parts by coaxial laser powder deposition

The time reduction to manufacture tools is a requirement, especially those that due to their operating conditions are subjected to stress, abrasion and wear, as well as having to adapt to new design requirements such as complex shapes and internal cooling channels, which are difficult to machine by conventional processes. In consequence, laminated tools might be a solution, nevertheless, the staircase effect in curved contours appears. This study analyzes the reduction of the staircase effect by coaxial laser deposition of 316L metal powder. Using previously cut sheets with thicknesses of 0.5, 1 and 2 mm, these are stacked to make samples with a 14 mm radius contour. An experiment is then designed, based on Taguchi, to determine the optimal multilayer deposition parameters of the molten metal powder. Parameters such as laser power, overlap, feed rate, substrate thickness and mass flow are considered to determine the lowest roughness measured mechanically and optically. Residual stresses are also analyzed and stacking and deposition strategies are proposed to achieve the desired curvature. Finally, the staircase effect is reduced and the optimal parameters are obtained, which include higher laser power and feed rate but low mass flow and overlap. In addition, lower roughness is obtained with lower mass flow rate and higher feed rate. Residual tensile stresses are also obtained due to the high cooling rates.