Toughening and Strengthening Response in Ni3Al-Bonded Titanium Carbide Cermets

Abstract

Abstract 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 μm by either sintering of mixed powders or a melt-infiltration sintering process. These TiC–Ni3Al cermets exhibit high fracture toughness together with exceptional flexure strengths (> 1 GPa), which are retained at temperatures of ~ 1000 °C. While the flexure strength exhibited a modest increase as the Ni3Al content was raised, both the Weibull modulus (up to ~20) and the toughness ~ 18 MPa m $\sqrt m $ 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.