利用电化学动电位再活化法, 研究了经650 ℃时效处理Super304H不锈钢晶间腐蚀敏感性的变化。结果表明, 时效处理Super304H晶间腐蚀的主要原因是M23C6沿晶析出; M23C6在晶界的析出速度和析出量均随时间而变化, 时效初期M23C6析出最快, 晶间腐蚀敏感性快速增大, 随时效时间延长M23C6析出数量增加, 晶间腐蚀敏感性不断增大, 增大速度与M23C6相对析出量增速有关。此外, M23C6不仅沿晶析出引发贫Cr型晶间腐蚀, 在晶内析出也会导致周围贫Cr, 促进腐蚀发生。

Double loop potentiokinetic reactivation method was used to investigate the intergranular corrosion susceptibility of super 304H steel which was subjected to aging treatment at 650 ℃. The results showed that intergranular corrosion occured due to the precipitation of M23C6 along grain boundaries. With the change of aging time, the precipitating rate and amount of M23C6 precipitated along grain boundaries varied accordingly. M23C6 precipitated rapidly at the initial stage, which led to the rapid increase of intergranular corrosion susceptibility. With the increas of aging time, the amount of M23C6 precipitates increased accordingly. This resulted in the increase of intergranular corrosion susceptibility. The increasing rate of intergranular corrosion susceptibility is related to the increasing rate of M23C6 precipitates. Depletion of Cr caused by precipitation of M23C6 along grain boundaries leads to the occurrence of intergranular corrosion, and the precipitation of M23C6 inside the grains also results in the formation of Cr-depleted zone and the subsequent corrosion.