Elevated temperature compressive creep behavior of tungsten carbide-cobalt alloys

Abstract

The compressive creep deformation of two-phase tungsten carbide-cobalt alloys with 12 and 15% Co has been investigated at temperatures of 800, 900, and 1000°C for stresses of 10,000 to 110,000 psi. At each temperature studied, the WC-Co alloys showed a decreasing steady-state creep rate with increasing WC particle size for low creep-stress levels. At high stress levels, the steady-state creep rate was observed to increase with increased WC particle size. These observations, with additional considerations of the creep behavior, indicated that two mechanisms were rate determining during deformation of WC-Co alloys. To ascertain the rate-determining mechanisms during deformation, existing creep models were extended to include the high volume loading of dispersed WC particles present in these alloys. At high stresses, the mechanism postulated to describe steady-state creep deformation was the looping of dislocations in the Co matrix between WC particles and the climb of pinched-off loops. The diffusion of Co in the matrix around WC particles has been suggested as the rate-controlling steady-state creep mechanism at low stresses.