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.