A model of residual stress distribution is presented for ion-nitrided specimen. The model account for contributions for nitrogen concentration gradient and stress relaxation near the specimen surface. The former is obtained from thermoelasticity theory by considering an analogy for internal stress due to point defect from nonuniform concentration and due to temperature gradient. The second contribution from stress relaxation is due to plastic strain by moving misfit dislocation and de-nitriding phenomena during nitriding process.
Several measurements for SM15C, SM45C, and SCM4 by blind hole drilling method were performed and the results compared with those of analytical prediction. The proposed analytical model was able to describe the dip-off in the measured residual stress distribution near the surface, which was not possible by other existing models.
