| Popis: |
Previous studies have shown that oxygen increased the rates of crack growth in Ni base superalloys at high temperatures (> 800 K) by up to four orders of magnitude over those observed in an inert environment for alloys such as inconel 718, Rene-95 and x 750. In this study, high temperature oxidation studies of pure Nb, NbC and Ni{sub 3}Nb using XPS were undertaken (a) to provide direct confirmation of the oxidation of NbC, (b) to explore the possible role of Ni{sub 3}Nb and (c) to assess the relative reactivity of the latter two phases, along with Nb, with oxygen. Nb, NbC and Ni{sub 3}Nb were oxidized as a function of temperature and constant oxygen exposure, and the results are presented in this communication. |
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