Toughening and strengthening response in Ni3Al-Bonded titanium carbide cermets

Nickel aluminide (Ni3Al) was used as a binder phase to fabricate dense TiC cermets with Ni3Al contents of up to 60 vol. % and TiC grain sizes of ?5 to ?0.8 £gm by either sintering of mixed powders or a melt-infiltration sintering process. These-Ni3Al cermets exhibit high fracture toughness together with exceptional flexure strengths (> 1 GPa), which are retained at temperatures of ? 1000¢XC. While the flexure strength exhibited a modest increase as the Ni3Al content was raised, both the Weibull modulus (up to ?20) and the toughness (up to ?18 MPa¡Ôm) exhibited substantial increases. The increased toughness was found to result from a combination of interface debonding and grain cleavage that combined to enhance plastic deformation of the Ni3Al ligaments in the crack wake. Crack opening displacement measurements reveal a blunted crack profile and suggest a bridging zone length in excess of 100 microns.