Investigations on induced residual stresses, mechanical and metallurgical properties of CO2 laser beam and pulse current gas tungsten arc welded SMO 254

Abstract

This research article focuses on the joining of SMO 254 stainless steel by autogenous CO2 Laser beam welding and pulsed current gas tungsten arc welding (PCGTAW) with ERNiCrMo3 filler. The studies proved that full penetration could be achieved on the weld joint of a 5 mm thick plate with a reduced heat input of 120 J/mm in the laser welding while in the case of PCGTAW it was 3032 J/mm. An attempt is made to do a comparative evaluation of the microstructure changes which have occurred owing to welding and thereby the mechanical properties. The studies revealed the lack of deleterious phases in both welding techniques. Presence of grain boundary thickening near the fusion zone and elemental segregation was observed in PCGTAW joints. The residual stress measurements by X-ray diffraction method were executed over the cross-section of the two different weldments. An attempt is made to represent the stresses variation along the weld region, heat affected zone and the base metal graphically. The tensile test validated that in every case the rupture ensued at the base metal and the higher weldment hardness than base metal proves the soundness of the joint.