Intergranular Corrosion Characteristics of Super Duplex Stainless Steel at various Interpass Temperatures

摘要

The effect of second phase formation on intergranular corrosion at the weldment in super duplexstainless steel was investigated using various interpass temperatures. Using the same alloycompositions and welding process, welding was carried out at interpass temperatures of 50 C, 150 C,and 250 C. As the interpass temperature was increased, the fraction of second phase formationincreased, due to increased time spent at the precipitation temperature of the second phase (, ).Potentiodynamic polarization testing and double loop electrochemical potentiokinetic reactivation(DL-EPR) testing were conducted in order to evaluate the corrosion resistance. In the case ofpotentiodynamic polarization testing, the Epit and Ipit values varied according to the interpasstemperature, and both the Epit and Ipit values decreased as the fraction of the second phase in theweldment increased. Furthermore, the intergranular corrosion resistance was evaluated using DL-EPRtesting, and the degree of sensitization increased with increasing interpass temperature. This effect wasbecause the size of surrounding regions containing reduced amounts of Cr increased with increasingsecond phase fraction.