The rotating bending fatigue strength of JIS-SCM415 steels after austenitic nitriding was evaluated to find the surface phase that gave the highest strength. Nitriding was performed at 903 K under conditions of K_N = 0.15, 0.25 and 0.35 atm^−1/2. In addition, specimens which were tempered at 523 K for 7.2 ks after nitridings with K_N = 0.15 and 0.25 atm^−1/2 were prepared. A specimen prepared by nitrocarburizing at 853 K was also evaluated as a comparison. Specimens nitrided at 903 K at K_N = 0.15 atm^−1/2 showed the highest fatigue limit because the 10 μm thick surface layer was a dual phase of austenite and martensite that might have a fine microstructure which inhibited initial crack generation and growth. Specimens nitrided at 903 K at K_N = 0.35 atm^−1/2 showed the second highest fatigue limit because the ε compound layer that was 20 μm thick had a high compressive residual stress. Specimens nitrides at 903 K at K_N = 0.25 atm^−1/2 showed the third highest fatigue limit because of the formation of a 6 μm thick compound layer which was a dual phase of ε and γ’ that had few voids and a high toughness (low hardness) in addition to its compressive residual stress. Tempered specimens showed a lower fatigue limit than that of non-tempered specimens. This was because the surface layer became brittle in tempered specimens. Specimens other than the tempered specimen in K_N = 0.25 atm^−1/2 showed a fatigue strength higher than that of a sample nitrocarburized at 853 K.

对奥氏体渗氮后的JIS-SCM415钢的旋转弯曲疲劳强度进行了评估，以找到给出最高强度的表面相。在903 N下，在K _N  = 0.15、0.25和0.35 atm ^-1/2的条件下进行氮化。另外，制备了在以K _N  = 0.15和0.25 atm ^-1/2氮化后在523 K下回火7.2 ks的样品。还比较了在853 K时通过氮碳共渗制备的样品。标本在903 K，K _N  = 0.15 atm ^-1/2时氮化由于10μm厚的表面层是奥氏体和马氏体的双相，可能具有良好的微观结构，从而抑制了初始裂纹的产生和扩展，因此具有最高的疲劳极限。在903 K下以K _N  = 0.35 atm ^-1/2氮化的样品显示出第二高的疲劳极限，这是因为20μm厚的ε复合层具有较高的压缩残余应力。标本氮化物在903 K时的K _N  = 0.25 atm ^-1/2由于形成了6μm厚的化合物层，该层是ε和γ'的双相，除了压缩残余应力外，几乎没有空隙且具有高韧性（低硬度），因此显示出第三高的疲劳极限。回火试样的疲劳极限比非回火试样低。这是因为表层在回火的试样中变脆。在K _N  = 0.25 atm ^{-1/2的情况}下，除回火试样外的试样的疲劳强度高于在853 K下进行了氮碳共渗的试样的疲劳强度。