Novel Ni-TaC nanocrystalline cermets

Cermets of Ni and TaC with nm-scale microstructures are made by devitrification of sputter-deposited amorphous thin films. The microstructures of these novel cermets show remarkably good thermal stability, with some grain sizes remaining less than 5 nm even after annealing for 1 hr at 700 degreesC. Hardnesses of up to 20 GPa have been achieved, comparable with single-phase TiN, but in materials with < 50 % (by volume) of ceramic phase. In this way, improved combinations of properties may be achieved, including toughness, thermal-expansion matching and adhesion to substrates.