Spall damage of solution-treated hot-rolled Inconel 718 superalloy under plate impact

Abstract

Spallation of a solution-treated hot-rolled Inconel 718 superalloy is investigated via plate impact loading along with ultrafast free-surface velocity measurements. Microstructures of the initial and postmortem samples are characterized with scanning electron microscopy and electron backscatter diffraction. Incipient spallation occurs near a peak shock stress of 5.3 GPa at a tensile strain rate of 105 s−1. Spall strength increases slightly (3.2–3.9 GPa) with increasing peak stress in the explored peak stress range (5.3–17.2 GPa) and tensile strain rate range (1.1 × 105–1.7 × 105 s−1). Ductile fracture is the main damage mode, and void nucleation occurs mostly at grain boundaries and triple junctions. Both intergranular and intragranular voids tend to nucleate preferentially at grain boundaries with a misoriention of 45°–55°. Molecular dynamics simulations are conducted to explain the mechanisms of intergranular and intragranular damage as observed in the experiments.