MACROKINETICS OF SHS INFILTRATION

ABSTRACT

The regimes of Ni infiltration during combustion of a sample comprising layers of the Ti-C reactant mixture and Ni have been studied. Ni spreading during the layer-by-layer combustion of the mixture was found to proceed in two qualitatively different limiting modes. These modes differed in the direction of the metal flow upon melting: a thin Ni layer flowed toward the combustion front, while the thick one moved in the direction of the combustion front propagation. The characteristic times of the main stages of the SHS infiltration process, i.e., heating, combustion and infiltration, have been estimated. The type of infiltration has been determined from the ratio of the characteristic times of the Ni layer heating to the combustion of the respective mixture layer. A symmetrical Ni distribution across the sample thickness has been observed during the simultaneous combustion of the reactant layers. The Ni distribution in the final product was found to be connected with the infiltration inertia regime.

Key Words:

• SHS
• Hard alloy
• Infiltration
• FGM