Microstructure and properties of 316L stainless steel fabricated by speed arc wire arc additive manufacturing

The 316L stainless steel component was manufactured by speed arc wire arc additive manufacturing(WAAM) under constant current. The formation of the component was explored, and the microstructure and mechanical properties at different regions of the component was compared under the scanning electron microscopes and the metallurgical microscope. The results indicate that the primary dendrites(PD) transform from acicular dendrites, strip dendrites to columnar dendrites along the deposition direction in single layer. The dimensions of secondary dendrites(SD) increases with the deposition height. The secondary dendrite arms sizes(SDAS) are 11.54, 12.50 μm and 15.52 μm at the bottom, middle and top of the sample, which are mainly affected by heat accumulation. In addition, the tensile strength of the sample along the deposition direction and scanning direction is 517 MPa and 527 MPa,exceeding the strength of forging. The percentage elongation after fracture of the sample is 22.5% and 15.0%. And the fracture mode of tensile samples is ductile fracture. However, the plasticity and the ductility of samples adopted along the scanning direction is better than that of the samples in the deposition direction.