Modeling and Optimization of Creep Behavior of Ni-Based Superalloys GTD-111 and IN-738LC Using Central Composite Design

In this study, the effects of temperature, stress, and type of materials and their interactions on the creep rate and rupture time were investigated by using central composite design (CCD). An experimental plan for CCD with two numerical factors, one categorical factor, and two levels was used to optimize the required number of experiments. Temperatures of 800 and 900 °C and stresses of 250 and 450 MPa were selected as factors for GTD-111 and IN-738LC superalloys, respectively. Experimental and numerical results showed that the main effects of factors and their interactions are significant on the creep rate and rupture time. Among all factors, the effects of temperature and stress dominated other factors. Moreover, it was indicated that the combination between temperature and stress is much more effective on creep rate response than on rupture time. The high creep rate and the low rupture time values were obtained at the highest stress and temperature for IN-738LC. With the same experimental condition, creep rate values were the most and rupture time values were the least for IN-738LC in comparison with GTD-111.