材料期刊网

利用多种分析手段深入分析了打磨处理的690TT合金在模拟压水堆一回路高温高压水环境中经不同时间浸泡后表面生长的氧化膜的微观结构. 结果表明, 从短期氧化到长期氧化, 氧化膜表面形貌变化不明显; 氧化膜主要由尖晶石结构的氧化物和单质Ni构成. 浸泡96和1440 h后, 氧化膜主要由富含Cr的氧化物构成. 浸泡720, 1440和2160 h后, 氧化膜均由外层、中间层和内层构成: 外层是分散的富含Ni和Fe的尖晶石结构的大颗粒氧化物; 中间层是致密的富含Cr的尖晶石结构的小颗粒氧化物; 内层是均匀连续的富含Cr的氧化物. 中间层和内层氧化物能对基体起到良好的保护作用; 随着氧化时间的延长, 保护层的平均生长速率逐渐降低. 打磨处理促进了690TT合金表面保护性氧化膜的生长.

The morphologies and structures of surface oxide films grown on ground Ni base alloy 690TT after immersion in the simulated hydrogenated primary water of pressured water reactors (PWRs) for different times were analyzed by various methods. After immersion for 35 h,\linebreak the ground alloy 690TT was covered with compact oxide particles. With the increase of the immersion time, the sample surfaces were covered with scattered big oxide particles and compact small oxide particles. Regardless of the immersion time, the grown oxide films are composed of spinel oxides and metallic Ni. After immersion for 720, 1440 and 2160 h, the oxide films are composed of three layers: the outmost layer is the separated big oxide particles which are rich in Fe and Ni; the intermediate layer is the compact small oxide particles rich in Cr, Fe and Ni; the inner layer is the continuous Cr oxides. The peak decompositions of the XPS results revealed that the Cr oxides in the inner layer are probably Cr₂O₃. The intermediate and inner layers in the oxide films could restrain the outward diffusion of metal atoms and also the inward diffusion of the oxygen atoms and then protect the matrix from further corrosion well. The average corrosion rate of the intermediate and inner layer decreased gradually with the immersion time increasing. Grinding treatment accelerated the growth of protective oxide film on alloy 690TT in the studied solution.