Cold compaction and solid-state sintering of WC-Co-based structures: Experiments and modeling

Cold compaction (200-1900 MPa) and sintering (1250 degrees-1350 degrees C) of cermets based on WC-Co were experimentally studied using die compaction, cold isostatic pressing, sintering, and creep tests. Two different-sized W C powders were used. The cobalt content varied over a range of 10-30 wt%. C old-compaction behavior has been described by using a Cam-Clay model. Die-w all friction was measured by using green powder compacts that had different aspect ratios. Friction coefficients were 0.28-0.85, depending on the WC p article size and cobalt content. Simple constitutive equations have been us ed to model the high-temperature behavior (sintering and creep). The consti tutive equations were implemented in a finite-element program to model the compaction, ejection, and sintering of bilayer structures that had differen t cobalt contents. The model can represent the effect of die-wall friction on the average density, as well as deformation inside the green compact. De nsity gradients were generated; they were revealed during sintering, becaus e the compact does not deform homogeneously. Simulation also can be used to evaluate deformations that are induced by sintering.