溶解氧对P92钢超临界水环境中应力腐蚀开裂的影响

Effect of dissolved oxygen on stress corrosion cracking of P92 heat resistant steel in supercritical water

在600℃/25 MPa超临界水（SCW）环境下采用慢拉伸试验（SSRT）与断口形貌分析技术研究了溶解氧（DO）对国产P92钢应力腐蚀开裂的影响规律。SSRT结果表明,P92钢在0~500μg/L溶氧溶度范围具有应力腐蚀开裂敏感性,且随溶氧溶度升高敏感性增强。通过扫描电镜（SEM）对试样断口截面及侧面形貌进行分析,结果表明随着溶氧溶度的升高,材料表面氧化层厚度增大,裂纹扩展速率增大;断口扩展区在高溶解氧含量下出现沿氧化物颗粒边界扩展的二次裂纹,其形成可能由氧化层内部萌生的微裂纹扩展至表面所致。

Effect of the dissolved oxygen（DO） on stress corrosion cracking of a P92 steel in supercritical water（SCW） was investigated by slow strain rate tensile（SSRT） test and fracture morphology analysis.The results of the SSRT test show that the P92 steel has SCC sensitivity in supercritical water with the dissolved oxygen content（DOC） in the range of 0-500 μg /L and the sensitivity increases with the increase of the DOC.The observation by SEM shows that the oxide layer thickness and the crack growth rate is enhanced with the increasing DOC.Secondary cracks growing along the boundary of oxide particles are observed on the fracture of the tensile specimen in SCW with high DOC,which is likely induced by the microcracks nucleated in the oxide layer and propagated to the surface of the layer.