Effect of pulsed laser energy on grain morphology and texture characteristics of stainless steel fabricated by laser-PTA additive manufacturing

This study proposes a pulse laser-assisted plasma transfer arc (Laser-PTA) additive manufacturing process. By using this process, the tensile strength and elongation of stainless steel are increased by 11.3% and 21.59% respectively. Using electron backscatter diffraction (EBSD) technique to study the microstructure and texture characteristics of the deposited layers. Further, the mechanism of the pulsed laser energy regulating the microstructure is revealed. The experimental results showed that the continuous growth of coarse columnar crystals in multi-layers deposition structures can be blocked by pulsed laser energy. Compared with the PTA process, the grain size of the multi-layers deposition structure obtained by the laser-PTA process is smaller, and the trend of preferred orientation is weakened. Moreover, increasing the laser pulse power can make this effect more significant. The result of texture analysis showed that the improvement of mechanical properties of laser -PTA samples is the result of grain refinement in deposition layers, inhibition of preferred orientation, and in-crease of volume fraction of high angle grain boundaries. The surface oscillation and thermal convection in the molten pool break the growth of columnar dendrites, destroy the original temperature gradient and affect the growth morphology and orientation of grains, which is the main mechanism to improve the process of laser-PTA additive manufacturing.