Effect of prior oxidation on the creep behaviour of nickel and iron based superalloys

摘要

Effect of prior oxidation on the creep behavior of an iron based alloy (Fe-Ni-Cr-Al alloy) in comparison with three nickel base superalloys with different aluminium and titanium content was investigated. A significant oxidation induced creep strengthening has been observed in the Fe-Ni-Cr-Al alloy while prior exposure was reported to result in creep weakening in nickel base superalloys. Oxidation-induced creep strengthening in Fe-Ni-Cr-Al alloy can be attributed to the improved adherence of surface oxide caused by the presence of yttrium. The oxidation-induced creep strengthening, however, is accompanied by considerable drop in creep ductility in Fe-Ni-Cr-Al alloy. The embrittlement of grain boundaries caused by both surface oxide and oxygen diffused inwards along grain boundaries reduced the creep ductility of the Fe-Ni-Cr-Al alloy. In contrast, oxidation induced weakening and embrittlement of nickel base superalloys caused the premature onset and shortening of tertiary regime, respectively, and thereby reduced both time- and strain-to-rupture considerably.