Rotating bending fatigue behaviour and quasi-static tensile properties of Wire Arc Additively Manufactured 308L stainless steel

Wire Arc Additive Manufacturing (WAAM) is a direct energy deposition method used to manufacture steel components by using an electric arc as a heat source to melt a metal wire and deposit it layer by layer. In this study, monotonic tensile tests, standardized Charpy impact tests, and rotating bending fatigue tests are executed to characterize the mechanical properties of WAAM 308L stainless steel using specimens extracted from additively manufactured plates. In particular, monotonic tensile properties are investigated in three directions: that is 0, 90, and 45 degrees with respect to the plane of deposition, whereas the fatigue strength is quantified for one direction only, i.e. 90 degrees since this is deemed to be the weakest.The mechanical characterization highlights that WAAM 308L SS shows an anisotropic behaviour, an enhanced strain-rate sensitivity, and an overall reduced yield strength as compared to the base material 308L. The anisotropic material behaviour is explained by the microstructure morphology since the austenite grains form anisotropic columnar zones due to an uneven heat profile during production. During the fatigue tests, the relatively high strain rate sensitivity causes susceptibility to self-heating at relatively low loading frequencies, i.e. below 100Hz