Study of Sensitization in Gas Tungsten Arc Welded 304 Stainless Steel Joints Using 308L Filler Metal

Austenitic stainless steels tend to form chromium depletion zones during welding. The chromium combines with available carbon around the grain boundaries to produce chromium-deficient areas, thus becoming susceptible to intergranular corrosion. The sensitization phenomenon of 304 stainless steel during gas tungsten arc welding (GTAW) process has been investigated. In this experiment, there were four welded samples observed. Two welded samples were cooled in air and cooled in oil immediately after welding, respectively. Meanwhile, another two welded samples were normalized by heated to 800 and 900 °C and held for 0.5 h before cooled in air. The welded samples were analyzed using optical microscopy, scanning electron microscopy and energy dispersive microscopy (SEM-EDS), and a Vickers hardness testing machine. The results show that normalizing affects significant changes in the microstructure due to the sensitization phenomenon. It can be seen that there is more carbide deposition in the welded sample with cooled in air and welded samples which normalized by heated to 800 °C and 900 °C and held for 0.5 h before being cooled in air. Meanwhile, the sample that was cooled in oil immediately after welding showed fewer chromium carbides. Normalizing the welded samples to 800 and 900 °C and holding it for 0.5 h before cooling in air triggers the sensitization process. Sensitization looks less occur in 304 stainless steel welds which were rapidly cooled in oil.