Te诱导纯Ni脆化的时效研究

Investigation on diffusion behavior of Te into nickel

熔盐实验堆中的裂变产物碲(Te)会导致堆内镍基合金结构材料晶间开裂,引起合金部件的失效,危害熔盐堆的安全运行。简化研究体系,在Ni基体上电镀Te薄膜,然后在700℃下对样品进行不同时间的真空热扩散,分析扩散后界面反应产物、合金微观结构、拉伸性能及断口形貌等变化。结果表明,界面反应产物Ni_3Te_2在700℃下具有很好的热稳定性;有Te扩散的纯镍样品拉伸性能下降更明显,拉伸断口为混合型断口;随着扩散时间的延长,Te在纯镍中的扩散深度逐渐加深。

Molten-salt reactor(MSR),one of the most promising next generation reactors,has incomparable advantages:inherent safety,fission fuel sustainable utilization,producing less long-lived wastes,excellent heat transfer characteristics and so on.Thorium-based molten salt reactor technology is an important way to supply long-term nuclear energy for the future.Hastelloy N alloy used as the structural material in MSR directly contacts with fluoride salts.Fission product Te leads to intergranular embrittlement of Hastelloy N alloy,which seriously affects the service life of Hastelloy N.There are many kinds of element in Hastelloy N alloy and the reaction products of Te and Hastelloy N are complicated.Therefore,it is difficult to analyze the intergranular embrittlement caused by Te.In the present study,the effect of diffusion time on the intergranular embrittlement of Te into nickel(Ni)was investigated to reveal the relations between Ni and Te.The electroplating method was used for preparing samples and the research was mainly concerned on varieties and stability of surface reaction products,tensile property,fracture morphology,trend of cracking and intergranular diffusion depth analysis.This study is helpful to improve Hastelloy N alloy to resist intergranular embrittlement.The results indicate that the main product was Ni 3Te 2 at 700℃,which had good thermal stability.Compared with samples of nickel without Te,the ultimate tensile strength(UTS)of samples with Te dramatically decreased,whereas the elongation was not obviously changed in the diffusion time range from 24 h to 1000 h.Fracture of the alloy with Te exhibited brittle fracture with intergranular section near the surface and transgranular fracture in the center.The depth of diffusion of Te into nickel and intergranular fracture gradually increased with time extension.