Understanding the pitting behavior of laser welds in different austenitic stainless steels: From the perspective of pitting initiation

The distinct pitting behavior between the fusion zone of QN2109 laser welds and that of 317 L is investigated. The segregation of Mn is different in the two fusion zones due to differences in composition and cooling rate. Both welds contain residual δ-ferrite, with QN2109 displaying higher δ-ferrite content owing to its elevated Mn and N levels. The two welded joints exhibit diverse pitting initiation sites. QN2109 produces a secondary austenite prone to pitting during laser welding, whereas in the 317 L fusion zone, M23C6 is dissolved, significantly reducing the number of pitting sites.