Microstructural characterization and mechanical properties of a novel TiC-based cermet bonded with Ni3(Al,Ti) and NiAl duplexalloy

A novel TiC/Ni-3(Al,Ti)-NiAl composite has been designed and synthesized by in-situ reactive hot-pressing a mixture of Ti3AlC2 and Ni powders. After hot-press sintering at 1500 degrees C and 30 MPa, almost fully dense composite was obtained and the in-situ formed TiC grains were well-bonded with Ni-3(Al,Ti) and NiAl alloys. Due to the nanolaminated structure in Ti3AlC2 materials that weakly bonded Al layers are more prone to be out-diffused from Ti3AlC2 lattice than that of Ti atoms. The deintercalated Al-Ti atoms would react with Ni to give rise to the formation of Ni-3(Al,Ti) and NiAl alloys, and meanwhile a crystal lattice structure transformation happened from hexagonal Ti3AlC(2) to cubic lattice TiC. The formation of phases, grains morphologies, sintering behavior and mechanical properties were associated with sintering temperature. The as prepared TiC/Ni-3(Al,Ti)-NiAl composite under 1500 degrees C exhibited superior mechanical properties comparing with the counterparts fabricated under 1350 degrees C and 1400 degrees C because of the enhanced microstructures and eliminations of pores. Hardness, flexural strength and fracture toughness of the TiC/Ni-3(Al,Ti)-NiAl composite at room temperature were determined as 9.9 +/- 0.35 GPa, 665 +/- 26 MPa and 10.23 +/- 0.4 MPam(1/2), respectively. Interestingly, the flexural strength and fracture toughness increases with temperature rising from 600 to 800 degrees C, the maximum of flexural strength and fracture toughness could reach 775 +/- 25 MPa and 11.6 +/- 0.4 MPa.m(1/2) at 800 degrees C.