铀材及铀合金氢蚀影响因素分析

Analysis of Factors Influencing Hydrogen Attack of Uranium and Its Alloy

为了提高和改善铀合金材料的抗氢蚀性能,必须深入了解其氢蚀机理及影响因素。利用带显微镜的气固反应系统,采用PVT法结合显微镜原位表征铀材及其合金氢蚀初期形貌和动力学特征,研究了合金元素、热处理方式以及晶界对铀合金材料氢蚀的影响。结果显示,U-2.5%Nb合金更易发生氢蚀,孕育期短,反应速度快;U材与U-2.5%Nb合金氢蚀初期成核形貌不同,U材氢化物核点尺寸明显分为大小2种,U-2.5%Nb氢化物核点尺寸较为一致;热处理形式显著影响U-2.5%Nb合金氢蚀孕育期大小;对于铀合金的氢蚀,晶界并不是成核的优先选择,氢化物在表面尖角处和粗糙处优先成核。

A gas-solid reaction apparatus equipped with an optical microscope for in-situ characterization was performed to analyze the morphology and kinetic character of uranium and its alloy in early stage of hydrogen attack. The effects of alloying element,pre-heat treatment and grain boundary on the hydrogen attack performance of uranium alloy were investigated. Results show that U-2.5%Nb alloy is susceptible to hydrogen corrosion,showing a shorter induction stage and a faster reaction speed. U and U-2.5%Nb alloy showed different nucleation morphologies in early stage of hydrogen attack. Namely,hydride scales with large and small sizes were formed on U,while hydride scales with a relatively uniform size were generated on U-2.5%Nb alloy. Moreover,pre-heat treatment evidently affected the induction time of U-2.5%Nb alloy subjected to hydrogen attack. In terms of the hydrogen attack behavior of uranium alloy,nucleation did not take place preferentially at the grain boundary but at sharp corner and roughened zones.