Use of DICTRA? simulations to support carbide particle growth study in NbC-Ni cemented carbide

Carbide particle growth observed in a NbC-12%Ni (mass percent) sample sintered at 1420 degrees C was discussed using DICTRA (R) simulation of spherical particles immersed in a Ni matrix. It is possible to describe the liquid formation during sintering using a model that assumes a spherical region of NbC, with radius equivalent to the NbC particle distribution, surrounded by nickel. NbC volume fraction was obtained for different simulation times allowing the evaluation of the dissolution behavior in different particle sizes. Small carbides (around 1 mu m in diameter) suffered total dissolution, while major carbides (10 mu m in diameter) did not dissolve during the simulation. Chemical content evidenced that Nb and C from carbide dissolution segregated to liquid phase reaching levels up to 15 and 2%, respectively, showing the availability of this elements to re-precipitate in non-dissolved carbides during cooling from sintering temperature. The simulations indicate that carbide particle growth observed in NbC-12%Ni sintered sample can be a result of dissolution and re-precipitation mechanism.