Erosion damage on solid boundaries in contact with liquid metals by impulsive pressure injection

The Japan Atomic Energy Research Institute is carrying out research and development to construct a spallation neutron source facility, which may bring innovative science fields. A high-power proton beam will be injected into a liquid-mercury target to produce neutrons. The mercury vessel will consequently be subjected to the pressure waves generated by rapid thermal expansion. The pressure waves will propagate from the liquid mercury into the vessel solid metal, and back again. The pressure waves may induce erosion at the interface between the solid metal vessel and the liquid mercury under certain loading conditions, e.g. impact. In order to investigate the impact erosion damage due to the pressure wave, we have carried out impact experiments using a modified conventional split Hopkinson pressure bar apparatus on mercury filling a small chamber. The chamber for the mercury consists of the input, the output bars and a collar. Disk specimens of 16 mm diameter and 5 mm thickness (A6061, 316SS, Inconel 600 and Maraging steel) were placed on the ends of both bars in contact with mercury. Surface degradation in the form of many pits was observed for pressure waves of 40 and 80 MPa, which are significantly lower than the yield stress of these metals. The ranking order of damage was found to be A6061>316SS≅Inconel 600>Maraging steel. In particular, A6061 fractured completely after 100 impacts.