Portal de Periódicos da CAPES

Steady state creep deformation of superalloy inconel 718

1987; Elsevier BV; Volume: 89; Linguagem: Inglês

10.1016/0025-5416(87)90246-1

1873-4928

Yafang Han, M.C. Chaturvedi,

Microstructure and mechanical properties

The creep deformation mechanism of Inconel 718 superalloy strengthened by coherent ordered disc-shaped body-centred tetragonal (DO22)γ″ phase and coherent spherical f.c.c. (L12) γ′ phase precipitates has been studied in the stress range 620–840 MN m−2 and the temperature range 853–943 K. Constant-stress tensile creep tests were used to measure the values of steady state creep rate ϵdots and the consecutive stress reduction method was used to determine the values of back stress. Transmission electron microscopy was used to measure the particle size of the γ″ and γ′ phases and to observe the dislocation structures of crept specimens. It has been found that the values of effective stress exponent ne and activation energy Qe expressed by the creep rate equation εs=A∗σa−σoGneGbkTexp−QeRT were between 1.2 and 5.9 and between 250 and 310 kJ mol−1 respectively. The values of ne and Qe suggest that the creep deformation mechanism changes from diffusional creep at 853–873 K to dislocation power law creep at 943 K in the stress range 620–720 MN m−2. However, at the temperature of 873 K the creep mechanism changes from diffusional or linear creep at applied stresses below 720 MN m−2 to dislocation power law creep in the stress range 765–840 MN m−2.