Processing and properties of Ti (C, N)-WC-based materials

Two Ti(C,N)-WC powder mixtures, one containing 0.88 wt% Co and the other 6. 2 wt% Ni + 2.9 wt% Co, were fabricated by different routes: pressureless an d gas-pressure sintering in argon and nitrogen, and hot-pressing under vacu um. The microstructures of all the sintered samples consisted of grains wit h a core/rim structure, the core being Ti(C,N) and the rim (Ti,W)(C,N). An inner rim also was present at the core/rim interface. The more highly doped materials also had an intergranular Ni-Co-Ti-W binder phase. The compositi ons and cell parameters of the hard phases, as well as of the binder, were analyzed. The nitrogen partial pressure in the sintering furnace was the ma in factor that influenced grain growth and phase composition. In fact, sint ering under argon enhanced grain growth and was accompanied by a lower tung sten content in the rim. The influence of the microstructure on some mechan ical properties (hardness, flexural strength, toughness, and Young's modulu s) also was investigated. Flexural-strength values up to 1550 MPa at room t emperature and 1200 MPa at 800 degreesC, and fracture-toughness values up t o 8 MPa(.)m(1/2) were measured, depending on the starting composition and p rocessing conditions.