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 microstructure and electrochemical corrosion was investigated. The initial addition of nitrogen to the shielding gas was found to decrease the pitting resistance of the clad as compared to that obtained without nitrogen addition. Subsequent additions of nitrogen, however, gradually enhanced the pitting resistance. Microstructural examination showed that secondary austenitic phase formed along the interdendritic cell boundaries of the primary austenite, 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 austenite occurred making the clad inferior to pitting corrosion resistance. Subsequent additions of N decreased the formation of secondary austenite, enhanced pitting resistance of the weld clad by stabilizing the passivity of the interdendritic cell boundaries. (C) 1998 .