Thermal Cycling Behavior of Thin WC-Co Sintered Pellets

Abstract

Hexagonal WC crystal phase, with a and c axis slightly larger than expected is obtained for thin sintered (at 1 400 ºC under vacuum) WC-20wt% Co samples having no extra carbon added. This effect can be associated with the elastoplastic hysteretic thermal expansion behavior detected in the thin disks and to the associated observed anisotropy showing a higher expansivity in the axial compared to the in-plane direction. By using a two phase model where the matrix is WC and the second phase is Co, it can be computed (from expansion data) that tensile forces are acting at room temperature in both directions for the examined specimen. By heating to about 50–80 ºC the strains/stresses become compressive as expected for WC-20wt% Co.