Abstract
The brittleness caused by heating in hydrogen gas was examined on several kinds of nickel specimens containing oxygen from 0.004% to 0.024%. It was clarified that this hydrogen embrittlement depends on the oxygen content, and by eliminating oxygen by preannealing at high temperature, it decreases considerably. Such a finding is similar to the hydrogen brittleness in copper. Also the brittleness attributed perhaps to the effect of residual hydrogen in nickel was observed. Namely, the recovery of brittleness and the so-called delayed failure phenomenon which occur in steels during atmospheric-temperature aging were observed. And, as a special characteristic, the embrittlement was obvious only in the case of rapid cooling and especially when tested by reverse bending. From these results it was concluded that the hydrogen embrittlement in nickel is due to the formation and growth of micro-cracks along grain boundaries by the reduction of oxide and the effect of residual hydrogen accumulated along them.
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