Microstructural, compositional and residual stress evaluation of CO2 laser welded superaustenitic AISI 904L stainless steel

CO2 laser welding was performed on AISI 904L superaustenitic stainless steel sheets, with optimised processing parameters determined by means of melt run trial evaluations.X-ray diffraction phase identification and light microscopy confirmed that the weld structure is fully austenitic and dendritic. A hardness increase in the weld bead with respect to the parent metal occurred and was related to both the microstructural refinement induced by a rapid cooling of the fusion zone and the presence of nanometric scale precipitates observed by TEM in the weld bead.Residual stresses were determined by means of X-ray diffraction, exhibiting tensile stresses, close to the yield strength, in the longitudinal direction in the weld bead, while the stresses were compressive in the transverse direction and in the base material.Tensile tests showed that welded specimens retained strength and ductility values comparable to those of the base material.