Chiang Mai Journal of Science

Residual stresses at the surface and in near-surface regions were intentionally generated by near-surface plastic deformation called deep rolling process. X-ray diffraction (XRD) technique was used to measure the residual stresses. Specimens with generated residual stresses at the surface were stress relieved by mean of heating at a temperature range of 300–600 °C with different soaking times of 0.1–10,000 min. It was found that generated residual stress of about -650 MPa was detected at the surface after the deep rolling process. Residual stresses decreased with increasing temperature and soaking time. A decrease of residual stresses during the stress-relief annealing was analyzed using the Zener-Wert-Avrami function. The activation enthalpy of residual stress relief was 2.64 eV, which was closed to the activation enthalpy of the iron self-diffusion. The results clearly indicated that the predominant relief mechanism was most likely the volume diffusion-controlled climbing of edge dislocations. Finally, simulation diagram of residual stress relief was shown with an overall error about 15%.   Keywords: Residual stress; Stress relief; Heat treatment; Stainless steel