应力对316L在液态铅铋共晶合金中腐蚀行为的影响

Effect of Stress on Corrosion Behavior of 316L in Liquid Lead-bismuth Eutectic Alloy

目的研究应力对316L在高温液态铅铋合金(LBE)中腐蚀行为的影响。方法将316L制成C型环试样,加载应力后将其置于500℃的LBE中腐蚀2500 h,利用X射线衍射仪(XRD)、场发射扫描电镜(SEM)、能谱仪(EDS)等手段分析腐蚀程度。结果在应力作用下,316L在LBE中的腐蚀机制仍然为氧化腐蚀,且形成的氧化层结构和成分与无应力状态下的一致;材料表面氧化层总厚度显著增加,且内/外氧化层之间更容易产生裂纹,随腐蚀时间的延长,外氧化层有剥落的趋势。施加应力后,试样的氧化速率系数从0.1901μm/h增大至0.2781μm/h,其中内氧化层生长速率增加得更显著。EBSD分析表明,施加应力后,316L组织未发生改变,晶界附近的腐蚀加剧。结论在应力作用下,基体晶界缺陷密度增加,元素在晶界处的扩散速率增大,内氧化层的生长速度加快,腐蚀速度增加。

The work aims to study the effect of stress on the corrosion behavior of 316L in high temperature liquid lead-bismuth alloy(LBE).Several C-ring specimens of 316L were etched in LBE at 500℃up to 2500 h.XRD,SEM,EDS and other equipment were employed to evaluate the degree of corrosion.The results showed that 316L specimens underwent oxidative corrosion in LBE under two stress states.The structure and component of its oxide layer were consistent with that without stress.The total thickness of the oxide layer increased after applying tensile stress to the specimen.In the corrosion process,the outer oxide layer was prone to cracking and had a tendency to peel off on the specimen.The oxide layer growth rate increased from 0.1901μm/h to 0.2781μm/h after being loaded.The growth rate of the inner oxide layer increased more significantly.EBSD analysis showed that the organization of 316L did not change after applying the stress,and the degree of corrosion near the grain boundaries increased.The increase in corrosion rate under stress is mainly due to the increased density of defects at the grain boundaries of the substrate and the increased diffusion rate of elements at the grain boundaries,which accelerates the growth of the inner oxide layer.