1990 Volume 76 Issue 5 Pages 767-774
The creep resistance of Nimonic 80A subjected to prior aging at 1 273 K for various periods of time between 30 and 3 000 h was measured by a constant stress creep test at 1 273 K-49 MPa, to confirm the existence of a so-called grain boundary precipitation strengthening due to γ' phase.
The minimum creep rate increased with prior aging time : from 3.1 × 10-2h-1for 30 h aging to 1.1 × 10-1 h-1 for 3 000 h aging. This increase in the minimum creep rate could not be correlated with a decrease in a density of intragranular precipitates of γ' phase. The minimum creep rate had a good correlation with the grain boundary area fraction covered with intergranular precipitates of γ' phase. The ratios of the minimum creep rate of the speciments subjected to prior aging to that of an idealized specimen without any intergranular precipitate were equal to the free grain boundary area fraction from the intergranular precipitates of γ' phase. This confirms the intergranular precipitation strengthening previously found in Ni-Cr-W based alloys due to α2-W precipitates (T. MATSUO et al.: J. Mater. Sci., 22 (1987), p. 1901).
