The effect of grain growth on hardness in hot-pressed silicon carbides

Excerpt

Silicon carbide (SiC) ceramics are, of course, hard and brittle. Hardness and brittleness are typically inter-related in ionically or covalently bonded ceramics. In applications where resistance to contact-induced cracking is desirable, it may be desirable to compromise hardness to lessen brittleness. A coarser-grained, dense SiC may enable decreased hardness with increased grain size (as represented by a Hall-Petch relation) and greater energy absorption through a more ductile-like (or “quasi-plastic”) deformation mechanism. Such a ductile-like mechanism is orders of magnitude more effective in absorbing energy than fracture processes are [1]. Grain growth in SiC has been demonstrated [2‐5]; however, those efforts involved conventional sintering methods (without pressure assistance) and some residual porosity was always present, and porosity undesirably facilitates cracking, crushing, and fracture processes in ceramics. …