Investigation of the oxide film on 308L weld surface produced during welding process

Some ASS welding are poor shielding by inert gas due to structural limitations, so the original passivation film may be destroyed. The inner surface of 308 L weld metal without shielding of inert gas would be oxidized under GTAW. The oxide film is double layer structure. The micro cracks are found on the surface of the outer layer oxide film, and there were nano-scale gaps scatter on the inner layer oxide film-WM interface. The outer layer oxide film was mainly composed of Fe2O3 oxide particles, and bind tightly. The inner layer oxide film was mainly composed of Fe3O4 and FeCr2O4 particles, and relative bind loosely. The Cr deficiency of oxide film related to the volatilization of CrO3 over 1000 °C.216