ODS钢在600和700℃静态Pb-Bi共晶中的腐蚀行为及机理

Corrosion Behaviors and Mechanisms of ODS Steel Exposed to Static Pb-Bi Eutectic at 600 and 700℃

以一种极具潜力的先进核能候选氧化物弥散强化(ODS)钢为研究对象,以不控制氧浓度的液态金属PbBi共晶(LBE)为腐蚀介质,研究了静态下高温(600和700℃)不同腐蚀时间对ODS钢腐蚀行为的影响及其微观机制。结果表明,600℃腐蚀至2000 h,ODS钢表面生成总厚度约为10μm的典型双层氧化膜,同时在内氧化层下方形成了一层较薄的富Al氧化层。基于致密的尖晶石内氧化层及富Al氧化层的保护作用有效减缓了腐蚀氧化速率,ODS钢显示优异于其它材料的耐LBE腐蚀性能。ODS钢在700℃腐蚀所形成的氧化膜结构及厚度与600℃明显不同:腐蚀100 h主要形成了厚度约为500 nm的Al2O3保护膜,大幅降低了腐蚀速率;腐蚀时间延长至500 h,大部分区域Al2O3氧化膜仍然存在,但同时出现的少量"疖状氧化物"破坏了Al2O3保护膜的连续性,从而成为了腐蚀的突破口。

With good neutron properties, anti-irradiation performances, heat transfer properties and inherent safety characteristics, liquid lead or Pb-Bi eutectic(LBE) has been a primary candidate coolant for accelerator driven system and advanced nuclear reactors. However, corrosion of structural materials is a critical challenge in the use of liquid lead and LBE in high temperature nuclear reactors. Therefore, research on corrosion compatibility of structural materials with LBE at elevated temperatures is of great significance. In this work, the long-term corrosion experiments in static LBE for a oxide dispersion strengthened(ODS) steel were carried out at 600 and 700 ℃. The temperature effects on different corrosion behaviors were studied by the analyses of XRD, SEM and EDS, and the underlying mechanisms were clarified. After exposing to LBE at 600 ℃ for up to 2000 h, a typical double-layer oxide scale with the thickness of about 10 μm was formed on the surface of ODS steel, which was composed of outer layers of PbFe-O and Fe3O4 and inner layer of Fe-Cr-Al spinal. In addition, a thin Al-rich layer was also formed under the inner layer. Due to the protective effect of the relatively dense inner layer and the Al-rich layer, ODS steel showed excellent resistance to LBE corrosion at 600 ℃ with a significantly lower corrosion rate. On the contrary, when exposed to LBE at 700 ℃, the structure and thickness of the oxide scale formed on the surface of the ODS steel were obviously different. After exposure for 100 h, a dense protective Al2O3 oxide layer with a thickness of about 500 nm was formed, greatly reducing the corrosion rate. With the corrosion time prolonging to 500 h at 700 ℃, most of Al2O3 layer was still remained. However, a few of nodular-like oxides were formed originated from local weak areas, which broken off the continuity of protective Al2O3 and led to deeper corrosion by LBE.