A WAAM benchmark: From process parameters to thermal effects on weld pool shape, microstructure and residual stresses

A two-dimensional experimental setup has been designed to investigate the influence of process parameters during WAAM operation. This experimental study has been also designed as a WAAM benchmark for numerical investigations such as thermal-mechanical ones. Indeed, several measurements have been done in-situ such as welding current and voltage, temperature, weld pool images and local displacement. Some measurements have been realized ex-situ: micro-structure and residual stresses. Residual stresses were investigated by neutron diffraction technique on two specimens. The experiments consisted in the deposition of 5 successive layers of 316L stainless steel filler-wire. 3 sets of process parameters were investigated based on variations of travel speed and linear energy from 147.1 to 189.7 J/mm. The welding thermal cycle was clearly visible on the time evolution of the displacement, also varying cyclically by a few tenths of a millimetre, as well as on the weld pool size. The weld pool size increased (up to 5 mm) with the number of layer increasing as the initial temperature of the specimen was higher due to the previous deposited layer. The micro-structure is textured with columnar dendrites of few millimetre long. The effect of studied process parameters on the residual stresses is slightly perceptible in the melted zone.