Abstract: This investigation clearly indicates the compressive residual stresses, which set up during carburizing and quenching treatment, play a major or dominant role in increasing the fatigue strength, the resistance against repeated impact, the fatigue fracture toughness, the fatigue macrocrack initiation and propagation lifes, and in reducing the fatigue sensitivity to notch as well as in restraining the quenching brittleness etc. for carburized steels. There is an interrelation between the residual stress and the strength or hardness of carburized layer, of which high hardness or strength can reduace the relaxation of compressive residual stresses. It helps develop the favourable role of compressive residual stress in the fatigue properties. It was confusing whether microstructure or compressive residual stress playing the leading role in the improvement of fatigue strength for case hardened steels. Now it has been clarified.

Key words: 残余应力, 裂纹扩展, 裂纹萌生, 疲劳强度, 渗碳