The effect of work-hardening and thermal annealing on the early stages of the uranium-hydrogen corrosion reaction

Abstract

A B S T R A C TThe characteristics of hydride formation on metallic U at the early stages were investigated for three differently treated samples. The first sample reacted in its as-received state, the second was thermally annealed and the third sample underwent cold work-hardening prior to reaction with deuterium. From the analysis, the vacuum heat-treated sample was found to be more resilient to hydriding at the nucleation and growth stage, exhibiting a reduced number of nucleation points when compared to the as-cast uranium. The work-hardened sample was observed to be more susceptible to H 2 corrosion, displaying very dissimilar hydriding behaviour when compared to the other.

What is the Role of Nb on Preferential Hydriding of Double-Phased Uranium, Stabilizing γ-U, or Avoiding Hydrogen Aggregation?

“…17−20 Due to these deleterious consequences, it is technologically important to search for possible methods to improve corrosion resistances against hydriding. 21 Through decades of experimental and theoretical studies, it has been found that uranium hybridization can be affected by many factors, such as thermal conductivity external stress/ strain, 22 surface features, 23 oxide thickness, 24 alloy elements, 25 methods of work-hardening and thermal annealing, 26,27 and so on. Increasing the applied tensile stress shortens the nucleation and growth periods of the hydrides and facilitates the formation of hydride growth centers.…”

Early stages of Mg–Nb alloy corrosion in a balanced salt solution – STEM-HAADF and EIS study

“…The initial corrosion attracted a considerable attention due to a possibility to better understand the corrosion behaviour in a long run. Early stage corrosion of numerous metals has recently been investigated: tin [26], uranium [27], aluminium [28], magnesium and copper [29]. Corrosion of alloys has also been investigated at initial stages: steel [30][31][32][33][34][35][36], nickel and cobalt superalloys [37], copper-tin bronze [38] as well as zirconium [39], magnesium [40] and aluminum alloys [41,42].…”

Mechanism of surface uranium hydride formation during corrosion of uranium

“…The reaction between U and H are widely accepted to be governed by four stages: the induction period, nucleation and growth period, bulk reaction, and termination period. 1,2 The first two are thought to be the key periods, during which H aggregates and hydride sites nucleate and grow. In the induction period, hydrogen penetrates the surface passivation layer of oxide then gathers at the oxide-metal interface.…”

“…Hydriding pitting locations have been one of the key concerned issues of many studies. 1,[3][4][5][6][7] Previous work indicates that, the H solubility limit in α-U at room temperature (293 K, 20°C) and 1-atm pressure is approximately 0.04 wppm (weight parts per million, 1 μg/g). 8 The critical concentration required to form stoichiometric UH 3 throughout the metal bulk is approximately 12,700 wppm, 9 being six orders of magnitude higher than the dissolved H concentration.…”

“…Investigations of H-induced metallic U corrosion and its alloys have provided evidences that each of the above-mentioned defect types provides a corrosion initiation site for hydride. 1,5,6,12,13 Electron backscatter diffraction (EBSD) has been utilized by Bingert et al 5 to prove the significant finding that grain and twin boundaries strongly influence initial hydride site locations. 14 Harker et al 15 have found that inclusions have an effect on the initial location of the H attacks, based on focused ion beam (FIB) analysis.…”