Synchrotron 3D μ-Tomography of Porosity during Hot Isostatic Pressing of a Single-Crystal Nickel-Base Superalloy

Abstract

The evolution of microporosity in single-crystal nickel-base superalloy CMSX-4 during hot isostatic pressing has been investigated by high resolution tomography at the European Synchrotron Radiation Facility in Grenoble. The kinetic dependencies of microporosity annihilation in the superalloy in initially as-cast and homogenized conditions were obtained. It was shown that smaller homogenization pores of about 5-10 μm in size are rapidly annihilate during hot isostatic pressing, while annihilation of larger solidification pores of size up to a few hundred micrometer takes a long time. After commercial hot isostatic pressing at 1288 °C, 103 MPa, 4 h only rare pores smaller than 20 μm remain, which are not critical for fatigue strength.