三种典型发动机用材料疲劳极限应力集中敏感性及喷丸的影响

摘要

Fatigue curves of C250 steel,TA29 titanium alloy and FGH96 powder metallurgy (PM) superalloy with stress concentration coefficients Kt ＝ 1 and Kt =1.7were investigated,and the effect of shot peening on the fatigue curve under the stress concentration con dition was also studied.The results show that the 107 conditional fatigue limits of C250 steel,TA29 titanium alloy and FGH96 PM su peralloy decrease from 757 MPa,366 MPa and 566 MPa to 526 MPa,240 MPa and 465 MPa respectively while the stress concentration coefficients increase from Kt =1 to Kt =1.7,indicating that the three kinds of high-strength materials have the stress concentration sensitivity of fatigue limit obviously.Moreover,after shot peening,fatigue limits rise to 597 MPa,297 MPa and 530 MPa respectively when the Kt is 1.7,which indicates that shot peening can mitigate fatigue limit stress concentration sensitivity of high-strength alloys from a technological point of view.On the other hand,the 105-cycle and 107-cycle strength difference of titanium alloy and PM superalloy is reduced with the increase of stress concentration coefficient,showing that shot peening can reduce the dispersion of fatigue test data.%针对发动机用C250钢、TA29钛合金和FGH96粉末合金,开展应力集中系数Kt=1和Kt=1.7条件下疲劳曲线研究,并研究喷丸对应力集中条件下疲劳极限的影响.结果表明:当应力集中系数由Kt=1提高到Kt=1.7时,C250钢、TA29钛合金和FGH96粉末合金的10 7周次疲劳极限分别从757 MPa,366 MPa和566 MPa降低到526 MPa,240 MPa和465 MPa,说明上述三个高强度合金都存在明显的疲劳极限应力集中敏感性;喷丸强化后,Kt=1.7条件下的疲劳极限提高至597 MPa,297 MPa和530 MPa,说明喷丸有助于从工艺角度缓和高强度合金的疲劳极限应力集中敏感性;随着应力集中系数增加,TA29钛合金和FGH96粉末合金的105周次和107周次对应疲劳强度差也随之减小,喷丸处理能够使疲劳性能数据的分散性有所降低.