PHASE REACTIONS IN Ti(C,N)/(Ti,W)C, Ti(C,N)/(Ti,Mo)C, (Ti,W)(C,N)/Co AND (Ti,W)(C,N)/Ni DIFFUSION COUPLES

摘要

In order to investigate interactions of (Ti,W)(C,N) and Ti,Mo)(C,N) with binder metals solid/solid diffusion couples were annealed. These two-dimensional arrangements provide good access to phase reactions occurring upon sintering already in the solid state. It was found in (Ti,W)(C,N)/Co- and (Ti,W)(C,N)/Ni-based couples that the reaction zone is thinner in contact with Co than with Ni. It was also observed that the reaction rate with both Co and Ni is lower if nitrogen is added to the hard phases. Beside a thickness variation of the diffusion zones a change in the micostructure was found. At the interface of nitrogen-free hard phases in contact with Co elongated microstructural constituents are formed with the main axis perpendicular to the interface, while at the interface of nitrogen-containing hard phases these elongated microstructural constituents were found in contact with Ni. Also phase reactions and the diffusion behaviour between the different hard phases were studied by means of solid/solid diffusion couples of the type Ti(C,N)/(Ti,W)C and Ti(C,N)/(Ti,Mo)C with various concentrations. After 1008h inside the Ti(C,N) phase of the Ti(C,N)/(Ti,W)C diffusion couple W-rich rims were found around Ti-rich cores. The thickness of these rims did not change with time. If W is exchanged by Mo it was observed that the well known core-rim structure is built by diffusion of Mo into the Ti(C,N) grains. But with time the Mo diffuses into the core of Ti(C,N) phase showing that the structure is not stable.