强流脉冲电子束作用下AISI 304L奥氏体不锈钢的微观结构与腐蚀性能

Microstructures and Corrosion Property of AISI 304L Austenitic Stainless Steel Irradiated by High-Current Pulsed Electron Beam

利用强流脉冲电子束(HCPEB)技术,对AISI 304L奥氏体不锈钢进行了表面辐照处理,详细考察了辐照前、后材料表面的微观结构和腐蚀性能。实验结果表明:经过HCPEB辐照后,材料表面的抗腐蚀性能有所改善;表面喷发形成熔坑实现清除夹杂物的净化作用,以及表面形成厚而致密的钝化膜可有效地阻碍点蚀,均是提高材料抗腐蚀性能不可忽视的因素。透射电子显微镜分析结果表明,HCPEB辐照材料表层时,诱发了大量的过饱和空位缺陷以及类型丰富且密度很高的线、面晶体缺陷,空位缺陷的凝聚形成了空位型位错圈和堆垛层错四面体等空位簇缺陷。这些缺陷有助于形成厚而致密的表面钝化膜,进而阻止阴离子穿过表面钝化膜,延迟腐蚀进程,提高受辐照材料的抗腐蚀性能。

High-current pulsed electron beam （HCPEB） with different pulses was utilized to irradiate AISI 304L stainless steel. The surface microstructures of the irradiated samples were characterized in detail. In particular, the corrosion behaviors of the stainless steel surface with and without HCPEB treatment were evaluated. The experimental results show that the corrosion resistance of the stainless steel after HCPEB treatment is remarkably improved compared with the original sample. Beside the surface purification effect of eliminating impurities due to the crater eruption, the formation of dense surface passive layer ,which effectively inhibits the pitting events, is also an important mechanism for the improvement of corrosion resistance of the irradiated materials. Transmission electron microscopy （TEM） observations suggest that a large amount of supersaturated vacancy defects combined with abundant line and planar defects are introduced when the material surface is subjected to the HCPEB irradiation. Furthermore, the agglomerations of the vacancy defects result in the formation of the vacancy cluster defects, such as vacancy dislocation loops and stacking fault tetrahedra （SFTs）. Those structural defects in the irradiated surface layer promote the formation of a thick and dense surface passive layer. It prevents corrosive anionic species from passing through the surface oxidation layer and delays the corrosion process, resulting in the improvement of corrosion performance of the irradiated materials.