304和316H不锈钢在LiF-NaF-KF熔盐中的腐蚀行为研究

Corrosion Behavior of 304 and 316H Stainless Steels in Molten LiF-NaF-KF

通过静态腐蚀及SEM/EDS、EPMA等分析表征技术,研究了304和316H不锈钢在700℃LiF-NaF-KF(FLiNaK)熔盐中的腐蚀行为。结果表明,这两种不锈钢在FLiNaK熔盐中的主要腐蚀形式是表面和近表面晶界处Cr的选择性流失。316H不锈钢由于含有Mo,腐蚀深度及失重均低于304不锈钢。腐蚀后,两种不锈钢的表面均出现了富集Ni和Fe的腐蚀层,而近表面区域均出现了大量的纳米级析出相。EDS分析结果显示,这些析出相是Cr和Al的氮化物或碳氮化物,析出相显著提高了材料的硬度。

The corrosion behavior of 304 and 316H stainless steels in molten LiF-NaF-KF(FLiNaK)salt at 700 ℃ was studied by static immersion test, followed by SEM/EDS and EPMA analyses. Results show that the corrosion characteristics of the two stainless steels in molten FLiNaK salt are mainly selective depletion of Cr from the surface and grain boundaries underneath the surface. The corrosion depth and weight loss of 316H stainless steel are lower than those of 304 stainless steel, which may be ascribed to the Mo addition in 316H steel. After corrosion, the two steels show surface corrosion layers enriched in Ni and Fe, as well as nano-sized precipitates in the steel matrix near the surface. EDS analyses suggest these precipitates to be Cr and Al nitrides or carbonitrides. The formation of these precipitates significantly increases the hardness of the materials.