INVESTIGATION OF SILICON-NITRIDE COMPOSITES TOUGHENED WITH PRENITRIDED TIB2

Titanium diboride, which was prenitrided in various conditions, was incorporated into Si3N4 before hot pressing. The TiN coating substantially reduced the chemical reaction between TiB2 and the Si3N4 matrix. The thickness of TiN coating played an important role in the chemical stability of TiB2 in the Si3N4 matrix and the strain compatibility at interfaces. The fracture toughness of Si3N4 was enhanced 33% with prenitrided-TiB2 particles (20% by volume). Crack deflection was the major toughening mechanism, but the microcracking mechanism could also play a role.