Study of Filler Metal Mixing and its Implication on Weld Homogeneity of Laser-Hybrid and Laser Cold-Wire Welded Thick Austenitic Stainless Steel Joints

Austenitic stainless steel AISI 316L grade base material with butt joint thickness of 15 mm and different root gap preparation was single pass welded using both laser-GMA hybrid and laser cold-wire feeding process. The aim was to be able to study the filler metal mixing in thick section laser welding and the effect of processing parameters on it. Particular interest was to examine how homogenous filler metal mixing is across the whole weld cross-section from the weld surface to the root portion. Avesta 2205 duplex stainless steel filler wire was used in order to produce an over-matched weld metal composition differing from the base metal. Chromium was used as a trace-element as its distribution and quantity within the weld cross-section was identified using SEM and EDS analysis. Moreover, micro- and macroscopic metallography was carried out to examine emerged weld microstructures and their features. In the technical paper the effect of influencing parameters on the amount and homogeneity of filler metal mixing such as root gap preparation, wire feeding orientation (leading vs. trailing) and welding process (hybrid vs. cold wire) are compared and discussed.