Effects of additive manufacturing on spall fracture in shock-loaded Ni-based superalloys

Although additive manufacturing rapidly expands to various application areas, some of which may involve high rate deformation, very limited data can still be found on its potential effects on the dynamic behavior of the materials thus produced. In this context, we have carried out an experimental study of the shock response of high performance Ni-based superalloys widely used in aeronautics, either additively manufactured (AM) by laser powder bed fusion or cast and wrought for comparison. In order to explore a wide range of pressures and strain rates, up to about 4×10⁶ s^-1, two loading techniques were used: planar impact of a laser-accelerated flyer and direct laser irradiation at high intensity. Hugoniot elastic limit and spall strength values inferred from time-resolved velocity measurements are high, typically about 2.5 GPa and 7 GPa, respectively. They are found to be similar in the AM material and its wrought counterpart within the scatter. On the other hand, extensive post-recovery observations including X-ray micro-tomography and Electron Back-Scattering Diffraction reveal a strong dependence of the initiation and propagation of spall damage on the rich and complex microstructures inherited from the manufacturing routes.