Thermal stability of residual stresses and work hardening of shot peened tungsten cemented carbide

Abstract

Tungsten cemented carbide of WC-10 wt.% Co with shot peening treatment was isothermal annealed at the temperatures ranging from 550 to 850°C for different time. The relaxation behavior of residual stresses and full width at half maximum (FWHM)11Full width at half maximum (FWHM). of the X-ray diffraction profiles was investigated using the X-ray stress analyzer. The variations of structure in the top surface layer were also determined via the X-ray diffractometer. The results showed that both the residual stresses and the FWHM reduced sharply in the initial stage, and then they gradually declined to the stable state. The thermal activation enthalpy of WC and Co phases calculated by Zener-Wert-Avrami function indicated that the predominant relaxation mechanism was thermally activated gliding of dislocations. The work hardening effect presented better resistance to thermal relaxation in comparison with the residual stresses. The microhardness also declined with the heating temperature and the annealing time, which was analogous to the changes of residual stresses and FWHM. The residual stresses in WC and Co phases remained at compressive state suggesting that the shot peened WC-Co composite has good thermal stability under the working temperature of up to 850°C.