Intergranular creep fracture in aggressive environments

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

“…The factors reported to be responsible for creep weakening in nickel-based superalloys are: γ′ (Ni 3 Al) depleted zone [5][6][7][8][9][10][11][12][13] in the near surface region and/or formation of CO/CO 2 gas bubbles [5][6][7][8]12,18,19] along the grain boundaries. The γ′ depleted zone is a consequence of oxidation of γ′ forming elements in the near-surface zone to form respective-oxides at the surface or along grain boundaries close to the surface.…”

Some selected topics in creep cavitation

“…[29] Hydrogen attack has been observed in a number of carbideComparatively fewer studies have addressed the role of containing steels, at temperatures in excess of around 300 ЊC, oxygen on the formation and growth of cavitation in nickeland at external hydrogen partial pressures in excess of based alloys. Two early studies by Raj [30] and Dyson [31] 2 MPa. [20,21] The resulting grain-boundary fissuring can subanalyzed the chemistry of oxygen/carbon reactions in nickel stantially reduce the lifetime of the affected component.…”

Effect of prior oxidation on the creep behavior of NiAl-hardened austenitic steel

“…Most of the studies reported in the literature [1,3,[5][6][7][9][10][11][12][13][14][15][16][17][18][19][20][21][22] with regard to prior-oxidation effects on creep behavior are on nickel-based superalloys. Further, the chromium and aluminum contents of the present Fe-Ni-Cr-Al alloy are closer to those of most of the nickel-based superalloys studied.…”

“…[16][17][18]21,22] The two important factors reported to be responsible for the creep weakening in nickel-based superalloys are the ␥Ј (Ni 3 Al)-depleted zone [16,17,21,22] just below the surface-oxide layer and the formation of CO/CO 2 gas bubbles [11,[13][14][15]19,20] along the grain boundaries. The ␥Ј-depleted zone is a consequence of the oxidation of ␥Ј-forming elements in the near-surface zone to form respective oxides at the surface or along grain boundaries close to the surface.…”

“…Some of these studies were directed toward understanding the dynamic effects of oxygen interaction during creep testing, [1][2][3][4][5][6][7] while others concentrated on the effect of prior oxidation at high temperatures on the creep behavior at relatively lower temperatures. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Most of these studies were on pure nickel [2,4,8] and nickel-based superalloys [1,3,[5][6][7][9][10][11][12][13][14][15][16][17][18][19][20][21][22] and have shown that the effect of oxygen is a sensitive function of alloy chemistry, oxidizing temperature, testing temperature, microstructure, and oxygen partial pressure. Other alloy systems that are of interest for high-temperature applications are austenitic stainless steels, precipitation-hardenable steels, or iron-based super-alloys.…”