Influence of nitrogen on the pitting corrosion behavior of 904L weld clad

The effect of nitrogen on the weld cladding of 904L filler metal towards mi crostructure and electrochemical corrosion was investigated. The initial ad dition of nitrogen to the shielding gas was found to decrease the pitting r esistance of the clad as compared to that obtained without nitrogen additio n. Subsequent additions of nitrogen, however, gradually enhanced the pittin g resistance. Microstructural examination showed that secondary austenitic phase formed along the interdendritic cell boundaries of the primary austen ite, in the absence of nitrogen addition to the shielding gas, offered good resistance to the pitting corrosion of the interdendritic cell boundaries. On initial introduction of N, reduction in the formation of secondary aust enite occurred making the clad inferior to pitting corrosion resistance. Su bsequent additions of N decreased the formation of secondary austenite, enh anced pitting resistance of the weld clad by stabilizing the passivity of t he interdendritic cell boundaries. (C) 1998 Elsevier Science Ltd. All right s reserved.