Effect of the Surface State on the Mechanical Properties and Fracture Kinetics of 316L Steel Samples Obtained by Selective Laser Melting

The effect of the surface state of 316L steel samples, which were obtained by selective laser melting, on the mechanical characteristics, stages and fracture mechanisms, acoustic emission parameters, and the strain-state characteristics, which were estimated by the digital image correlation method, has been studied. A decrease in the static and fatigue strength of as-built samples in the region of low loading amplitudes and an increase in the elongation at fracture have been revealed compared to these characteristics for machined samples. For as-built samples, the appearance of high-amplitude acoustic emission signals indicating the nucleation of surface microcracks at an earlier deformation stage has been detected. It is assumed that knee point on the fatigue curves and amplitude dependences of the characteristic zones size at fracture surfaces are associated with the transition from a plane stress state to a plane strain state of the material with a decrease in the stress amplitude.