Investigation of Chromium Carbide Precipitation and Corrosion Behavior on Stainless Steel AISI 304 for Welding Process Development
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This research is aimed at investigating the amount of chromium carbide (Cr23C6) in stainless steel AISI 304 by electrochemical technique testing, in calculating the Pa values that corresponding to sensitization stage and the corrosion behavior. The results will carry on to developing the welding process. The specimens were produced with Shielded Metal Arc Welding method. Moreover, it was bending at the angle 0, 90 and 180 degree and the process finished on post-heat treatment with different cool down conditions are 800ºC annealed in air cooled, 1100ºC annealed in water cooled and annealed 1100ºC in air cooled respectively. The results show that: first conditional is appeared the maximum amount of Pa value (Pa > 0.4), indicating that more precipitation of Cr23C6 in heat affected zone (HAZ) of specimen. The second conditional is not found the sensitization stage because when the specimens were annealed at high temperature, the chromium carbide will break up and residual stress in HAZ will decrease. At last conditional is found the less amount of Pa value; the reason of using high temperature on annealing process will decrease chromium carbide, but slowly air-induced cooling must pass the critical temperature then some Cr23C6 will appear at grain boundary and cause of high corrosion rate. Concerning to the corrosion behavior, the second conditional present the lowest corrosion rate, corresponding to the better-quality of passive film. Whereas, the first conditional shown the highest corrosion rate and low quality of passive film. Thus, 1100ºC annealed with water cooled is excellent condition for developing the welding process.