Influence of High Laser Scanning Speed on Macro-form, Microstructure, and Tensile Properties of Austenitic Stainless Steel Made by Oscillating Laser-PTA Additive Manufacturing

Oscillating laser-assisted plasma transfer arc (Laser-PTA) additive manufacturing technology using coaxial feeding powder was proposed in this paper. To improve the surface accuracy, microstructure and mechanical properties of the formed thin-walled structure, a transverse linear scanning path laser beam oscillation (LBO) process was used. Considering that the interlaminar region is the weak region of the multilayer additive manufacturing structure, this paper focused on the influence of the laser scanning speed on the microstructure and mechanical properties of the interlaminar region. The results show that compared with Laser-PTA process, the LBO process improved the surface accuracy of the formed structure, and achieved shorter and finer dendrite growth morphologies. In particular, the LBO process with high laser scanning speed had a positive influence on the geometric dislocation density and high angle grain boundary in the interlaminar region, which improved the plasticity of the interlaminar region. In addition, the LBO process with high laser scanning speed reduced the  〈111〉 and 〈101〉 crystallographic textures and improved the strength of the interlaminar region. The optimization of the microstructure in the interlaminar region had a favorable effect on the overall mechanical properties of the thin-walled structure, and the tensile test results showed that the LBO process with high laser scanning speed significantly improved the ultimate tensile strength and elongation in the vertical and horizontal directions.[graphic not available: see fulltext]