Modelling of metal-binder migration during liquid-phase sintering of graded cemented carbides

Sintering of cemented carbides with graded metal binder content is modelled in this article. Production of graded cemented carbides by traditional liquid-phase sintering is hampered by high rate of liquid-binder migration with inevitable subsequent homogenisation of binder content in specimens. The driving forces of the migration are analysed. It is shown that the migration is governed not only by capillary forces but also by additional stresses that arise due to surface tension at solid-liquid interfaces. As a result, the migration takes place even in pore-free graded specimens. A numerical approach for the prediction of binder flow with coupled deformation of the refractory skeleton during liquid-phase sintering is put forward. Calculations predict that complete densification of specimens with retention of graded-binder distribution can be achieved by sintering with long solid-state sintering stage ended by comparatively short high temperature liquid-phase stage.