304NG在超临界水中的腐蚀增重随温度的异常关系

研究了奥氏体不锈钢304NG在550、600和650℃超临界水环境下的腐蚀行为。采用扫描显微镜、X射线能谱仪、X射线衍射仪分析了氧化膜的腐蚀形貌、组织结构和成分分布。实验结果表明,试样在3种不同温度下经1000h腐蚀实验后的增重均符合幂函数规律,但650℃时的腐蚀增重与600℃时的相比大幅下降,其主要原因为在较高温时,Cr的扩散速度快,试样表面氧化膜能够维持保护性从而使疖状腐蚀分布数量减少所致。

Abnormal Weight Gain Behavior of 304NG Stainless Steel in Supercritical Water

The corrosion behavior of 304NG stainless steel was investigated in supercritical water (SCW) at 550, 600 and 650 ℃. The SEM, EDS and XRD were used to analyze the corrosion morphology, structure and chemical composition of oxide film. The experiment results show that the oxidation of 304NG stainless steel approximately follows power function growth kinetics after exposure to supercritical water for 1 000 h, while the weight gain decreases drastically at 650 ℃. The possible mechanism of the anomalous temperature dependence of oxidation kinetics is ascribed to the rapid diffusion of Cr at higher temperature, maintaining protectiveness of oxide film on the sample surface, and finally resulting in the decrease of the nodular corrosions.