Abstract
In order to study on surface modification of SCM415 steel by carbonitriding and fine particle peening. The characteristics of fatigue crack propagation were investigated for three-point bending tests. Fine particle peening was used two different shot sizes of 50 and 100μm. The three-point bending fatigue tests were conducted at 20Hz and two stress ratios R=0.1 and 0.3. It was found that the fatigue strength of fine particle peening materials yielded high compressive residual stress was improved, and also showed extreme delay of the crack propagation in the carburized case. And crack propagation rate was correlated with stress intensity factor range ⊿K and effective stress intensity factor range ⊿K_<eff>.
