4. Experimental procedures
In order to validate the predictive ability of the novel damage
constitutive model, creep experiments of nickel-based superalloy GH4169
were conducted. The creep specimens with 26.6mm gauge length and 5 mm
gauge diameter were fabricated from 22 mm as-received cylindrical bars.
The creep tests were performed under stress range of 515MPa-925MPa and
temperature range of 600℃-650℃. The specific experimental details are
listed in Table 1. Specimens 1-12 were used to calibrate the novel
damage constitutive model. Furthermore, in order to verify the
interpolation and extrapolation abilities of the model, specimens 13-18
were designed to perform the post-audit validation. It is worth noting
that the experimental conditions of specimens 13-15 are the same as
specimens 8-9. The purpose of this repeated trials is to further
illustrate the scatter of the creep data.
After the creep experiments, the
ruptured specimens at different temperature and stress levels were
prepared for microstructural observation by using scanning electron
microscope (SEM). The standard metallographic methods were adopted
including grind, polish and etch.
TABLE 1 Experimental details of
creep tests.