Refinement and Experimental Validation of a Vacancy Model of Pore Annihilation in Single‐Crystal Nickel‐Base Superalloys During Hot Isostatic Pressing

Initially as-cast and homogenized single-crystals of nickel-base superalloy CMSX-4 were subjected to hot isostatic pressing at temperature of 1288 °C. Two series of experiments were performed: under the same pressure of 103 MPa but with different durations, between 0.5 and 6 h, and under different pressures, between 15 and 150 MPa, but for the same time of 0.5 h. The porosity annihilation was investigated metallographically and by high resolution synchrotron X-ray tomography. The obtained experimental results were compared with the predictions of the vacancy model proposed recently in our group. In this work the model was further refined by coupling with X-ray tomography. The model describes the evolution of the pore arrays enclosed in the 3D synchrotron tomograms during hot isostatic pressing and properly predicts the time and stress dependences of the pore annihilation kinetics. The validated model and the obtained experimental results can be used for selecting the optimal technological parameters such as applied pressure and processing time.