Prevention and reversal of oxygen embrittlement in nickel

Abstract Attempts to reverse the oxygen embrittlement caused by high temperature air exposure of nickel of various purities are described. It is shown that reversal can be effected in certain reducing environments in those grades of nickel having very low concentrations of metallic impurities, except in regions where heavy cavitation has occurred owing to gas formation. Oxygen embrittlement can similarly be prevented by prior annealing in hydrogen, but again only in the absence of significant metallic impurities. These results are explained on the basis of three distinct phenomena leading to embrittlement, and their implications are considered for the similar embrittlement observed in superalloys.