残余元素锡对齿轮钢疲劳性能的影响

摘要

The effect ofresidualelementtinon fatigue crack growth rate(FCGR)and fatigue life(FL)of 20CrMnTi steel has been studied using fatigue machine,and fracture morphology was observed by SEM.The re-sults show that when ΔK<33.35 MPa· m1/2,FCGR of 20CrMnTi containing 0.05%Sn is a bit high,while ΔK>33.35MPa· m1/2,FCGR of 20CrMnTi without Sn is a bit high;however,there is no significant difference in FCGR and could be considered equal.Both of the fracture morphologies of fatigue crack growth are quasi-cleav-age fracture+a small amount of dimples and there is no big difference between w(Sn)=0 and 0.05%.The FL of the tested steel without Sn and with 0.05%Sn is,respectively,4.0×104cycles and 4.1×104cycles.Fracture analysis shows that,in the two samples,fatigue source is on the specimen surface,no fatigue striations appears on fatigue zone,morphology of transient fracture zone is dimple and thereare no significant differences between the two tested steels.Namely,there is no obvious effect on fatigue property of 20CrMnTi steel when residual ele-ment Sn content is less than 0.05%.%利用疲劳试验机,研究了残余元素Sn对20CrMnTi钢疲劳裂纹扩展速率以及疲劳寿命的影响,同时利用扫描电镜分析断口形貌,结果表明:当ΔK<33.35 MPa· m1/2、w(Sn)为0.05%时裂纹扩展速率稍高,当ΔK>33.35 MPa· m1/2、w (Sn)为0时裂纹扩展速率稍高,然而两者扩展速率总体差别不大,可认为一致;w(Sn)为0或0.05%时,疲劳裂纹扩展断口形貌均为准解理断裂+少量韧窝,无明显差别.不含Sn及含0.05%Sn时,疲劳寿命分别为4.0×104周次、4.1×104周次,断口分析表明,疲劳源区均在试样表面,疲劳区均未出现疲劳条纹,瞬断区均呈韧窝状断口形貌,无明显区别.即当w(Sn)≤0.05%时,对20CrMnTi钢疲劳性能没有明显影响.