Nd: YAG Pulsed Laser Dissimilar Welding of UNS S32750 Duplex with 316L Austenitic Stainless Steel

Abstract

Duplex stainless steels (DSSs), a particular category of stainless steels, are employed in all kinds of industrial applications where excellent corrosion resistance and high strength are necessary. These good properties are provided by their biphasic microstructure, consisting of ferrite and austenite in almost equal volume fractions of phases. In the present work, Nd: YAG pulsed laser dissimilar welding of UNS S32750 super duplex stainless steel (SDSS) with 316L austenitic stainless steel (ASS), with different heat inputs, was investigated. The results showed that the fusion zone microstructure observed consisted of a ferrite matrix with grain boundary austenite (GBA), Widmanstätten austenite (WA) and intragranular austenite (IA), with the same proportion of ferrite and austenite phases. Changes in the heat input (between 45, 90 and 120 J/mm) did not significantly affect the ferrite/austenite phase balance and the microhardness in the fusion zone.

Autogenous Fiber Laser Welding of 316L Austenitic and 2304 Lean Duplex Stainless Steels

“…However, its decrease in the HAZ on 2304 steel side (average value 197 HV0.2) was observed, which is a result of the structural changes shown in the microscopic studies. Due to the different morphology and austenite arrangement between weld metal and lean duplex, the microhardness of the autogenous weld metal was higher (about 20 HV0.2) than microhardness of the lean duplex steel [33]. The results are distinctive for dissimilar austenitic-duplex stainless steel welded joints-which was also demonstrated by other authors [33,52,54].…”

“…Due to the different morphology and austenite arrangement between weld metal and lean duplex, the microhardness of the autogenous weld metal was higher (about 20 HV0.2) than microhardness of the lean duplex steel [33]. The results are distinctive for dissimilar austenitic-duplex stainless steel welded joints-which was also demonstrated by other authors [33,52,54]. For 316L austenitic stainless steel microhardness value was in a range of 186-209 HV0.2, which corresponds well to the literature [38,50].…”

“…Existence of an unmixed zone that originated from each base material was stated by Chun et al [53]. The approximately 50:50 ferrite/austenite microstructural balance can be reached with solution annealing in the range of 1050-1100 • C, and it is especially important in autogenous welds [33]. Saravanan et al stated that the higher microhardness of the weld zone is attributed by the formation of finer and uniform grains following high cooling rate [54].…”

“…Despite the fact that duplex steels are considered sensitive to high cooling rate, they can be successfully welded in conditions of large negative temperature gradients, e.g., under water and using concentrated heat sources [32][33][34]. In addition, a significant problem during welding is the risk of chromium nitride precipitation, as well as the occurrence of micro-areas depleted in Cr and Ni.…”

Quantitative Correlation between Thermal Cycling and the Microstructures of X100 Pipeline Steel Laser-Welded Joints

“…Zhou et al [11], Chen et al [12], and Casalino et al [13] studied the laser welding-brazing process of Titanium-Aluminum dissimilar metals. Silva Leite et al [14] and Hipp et al [15] discussed the laser welding process and mechanism of various stainless steels.…”