Hydrogen degradation of pre-oxidized zirconium alloys

Abstract

The presence of the oxide layers on Zr alloys may retard or enhance the hydrogen entry and material degradation, depending on the layer features. This research has been aimed to determine the effects of preoxidation of the Zircaloy-2 alloy at a different temperature on hydrogen degradation. The specimens were oxidised in laboratory air at 350ºC, 700ºC, and 900ºC. After, some samples were tensed at 10-5 strain rate and simultaneously charged with hydrogen under constant direct voltage in 1 N sulfuric acid at room temperature. Other specimens were charged without any tension, then annealed at 400ºC for 4 h and finally tensed at above strain rate. The SEM examinations were performed on the cross-sections and fracture faces of specimens. The obtained results demonstrate the effects of the oxide layer on the cathodic current and hydrogen entry, mechanical properties and the appearance of hydrides and fracture behaviour.

Oxidation and Hydrogen Behaviur in Zr-2Mn Alloy

“…There is no clear whether the oxide layer formed at a temperature of the breakaway phenomenon may be still efficient against hydrogen entry and what is the effect of descaling on the hydrogen absorption. Moreover, the oxide phase transformation and descaling may appear at a lower temperature and in a shorter time, comparing to those shown above, in the presence of high stresses [5].…”

Hydrogen Embrittlement and Oxide Layer Effect in the Cathodically Charged Zircaloy-2

“…Despite this knowledge, the influence of the oxide layer characteristics on hydrogen absorption was not often investigated. The applied cathodic charging in cold or heated electrolytes was already utilized [14,20,38,50,56,57,60,[84][85][86][87], resulting in the appearance of hydrogen within a thin subsurface layer, mainly as the hydrides and saturated or oversaturated hydrogen interstitial solution. The further annealing (here called homogenizing heat treatment) resulted in a uniform hydrogen concentration.…”