Silicon carbide (SiC) and Silicon nitride (Si3N4) are the most successful
engineering ceramics, owing to a favorable combination of properties,
including high strength, hardness, and freacture toughness and
low thermal expansion coefficient. However, the impact damage behavior
of SiC and Si3N4 ceramics has not been widely characterized.
In this work, ‘static’ sphere indentation and ‘dynamic’ explosive indentation
were conducted to characterize the impact damage behavior
of SiC and Si3N4 ceramics with various microstructures and sintering
additives. In SiC, the effect of rare-earth oxides, the typical
sintering additives, on subsurface damage upon static and dynamic
indentation was studied. In Si3N4, 3 grades with different grain size
and shapes (fine-equiaxed, medium and coarse-elongated) were prepared.
In order to observe the subsurface damage zone, a bonded-interface
technique was adopted. Subsurface evolution of the specimen
was then characterized extensively using optical microscopy, SEM,
and TEM. In case of static indentation, examination of subsurface
damage reveals the competition between brittle and ductile damage
modes. Dynamic indentation, however, induces a massive subsurface
yield zone that contains extensive micro-faults. It is suggested that the
grain boundary phase plays an important role in dynamic fracture as
well as in static fracture behavior of ceramics.