Silicon nitride is one of the most successful engineering ceramics, owing to a favorable combination of properties, including high strength, high hardness, low thermal expansion coefficient, and high fracture toughness. However, the impact damage
behavior of Si3N4 ceramics has not been widely characterized. In this study, sphere and explosive indentations were used to characterize
the static and dynamic damage behavior of Si3N4 ceramics with different microstructures. Three grades of Si3N4 with different
grain size and shape, fine-equiaxed, medium, and coarse-elongated, were prepared. In order to observe the subsurface
damaged zone, a bonded-interface technique was adopted. Subsurface damage evolution of the specimens was then characterized
extensively using optical and electron microscopy. It was found that the damage response depends strongly on the microstructure
of the ceramics, particularly on the glassy grain boundary phase. In the case of static indentation, examination of subsurface
damage revealed competition between brittle and ductile damage modes. In contrast to static indentation results, dynamic
indentation induces a massive subsurface yield zone that contains severe micro-failures. In this study, it is suggested that the
weak glassy grain boundary phase plays an important role in the resistance to dynamic fracture.