Precipitation phenomena in MC-Ni-Co cermet systems

摘要

Ti(CN)-Ni-Co, WC-Ni-Co, and TaC-Ni-Co cermets were prepared, in order to understand the effect of carbide dissolution during the heating and sintering stages of the precipitation phenomena. Magnetic properties, such as magnetic saturation (4πσ) and coercive force (H c), were measured and related to the observed changes in the microstructure. There is evidence in the TaC-Ni-Co system that early precipitation occurs during the heating stage. But they do not influence the final microstructure. Most of the dissolved carbides tend to re-precipitate on the growing particles during sintering while the remaining solutes in the melt precipitate in the binder during cooling, thus affecting the coercive force of cermets. The TEM analysis identified the precipitates as TiNi(TiCo), Ti(CN) in the Ti(CN)-Ni-Co cermet, Co3W, WC in the WC-Ni-Co cermet, and Co2Ta, TaC in the TaC-Ni-Co cermet.