U-2.5Nb氢蚀初期动力学试验研究

Hydriding Kinetics at Early Stage for U-2.5Nb Alloy

利用带显微镜的气固反应系统,在线观察了U-2.5Nb氢蚀初期氢化物成核和生长过程,表征了U-2.5Nb氢蚀初期的动力学特征和反应速度,研究了温度、压力和膜厚对U-2.5Nb氢蚀初期行为特征的影响。结果表明,U-2.5Nb比未合金化铀的氢化速度大很多,抗氢蚀性能更差。在低温(<125℃)下,孕育期随反应温度的升高而变短,遵从Arrhenius关系,超过125℃,孕育期随反应温度的升高而变长,孕育期存在一最小值;孕育期随反应压力升高而变短,与反应氢压力成反比关系;膜厚对孕育期的影响极其明显,孕育期随氧化膜厚度增加而变长。孕育期越长的氢蚀,其表面的成核点越少,成核越不均匀,且易在局部形成大的氢化物,氢化速度亦越低。

The nucleation and growth of hydride on U-2.5Nb alloy was characterized utilizing a Sievert ＇ s-type apparatus with an optical microscope, and the kinetics of hydriding was calculated from the measured decreases in pressure. The effect of temperature and pressure and oxide thickness on the behavior of hydriding was studied. The hydriding rate of U-2.5Nb alloy is higher much than that of U. Hydriding induction time decreases as the temperature increases, which follows the Arrhenius law under a temperature of about 125 ℃, but beyond 125 ℃, induction time increases sharply with temperature increasing. Induction time varies as the inverse of the hydrogen pressure, which follows the reciprocal relation. The oxide thickness on U-2.5Nb surface affects the induction time clealy, and induction time increases with the increasing of oxide thickness. In the case of hydriding with long induction time, reaction site is fewer, and nucleation distribution is asymmetrical that is apt to local corrossion.