组织老化对P92钢在超临界水中氧化行为影响研究

Influence of Thermal Aging on Corrosion Behavior of Ferritic-martensitic Steel P92 in Supercritical Water

实验研究了P92耐热钢的组织老化规律及其在超临界水环境中的氧化行为,讨论了微观组织老化对其腐蚀行为的影响机理。在800℃下进行了200和400 h的老化实验,之后在600℃、25 MPa超临界水环境下进行了最长1500 h腐蚀实验。利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)对金相组织、氧化膜微观形貌、物相成分等进行了分析。结果表明:组织老化特征表现为板条马氏体粗化、M23C6的析出熟化及亚晶的形成和长大。在超临界水中氧化动力学曲线均介于抛物线和立方规律之间,氧化增重随老化时间的增加而增加;氧化物主要为Fe_(3)O_(4)、(Fe,Cr)_(3)O_(4)以及Cr_(2)O_(3);与未经老化的试样相比,组织老化后的试样更容易出现裂纹和剥落现象。

Ferritic-martensitic steel P92 was themally aged at 800℃for 200 and 400 h,respectively.Then corrosion behavior of the aged P92 steels was investigated in supercritical water at 600℃,25 MPa up to 1500 h.The microstructure,oxidation kinetics of the steels,morphology and phase composition of oxide scales were characterized by means of SEM,TEM and XRD.The results indicate that after thermal ageing at 800℃,the P92 steel presented microstructure composed of coarsened martensitic lath,Ost-wald ripening of M23C6 carbides and sub-grains.Furthermore,the oxidation kinetics curves of the aged P92 steels at 600℃are between parabolic and cubic curves,while the weight gain increased with the in-creasing ageing time.The oxide scales are composed of Fe_(3)O_(4),(Fe,Cr)_(3)O_(4)and Cr_(2)O_(3).It is also discov-ered that there is more cracks on oxide scales of the aged steels,which led to spallation of oxide scales,whereas no signs of spallation were found on the not aged steel.