喷丸强化对FGH96粉末高温合金疲劳性能应力集中敏感性的影响

为研究喷丸强化对FGH96粉末高温合金疲劳性能应力集中敏感性的影响,采用不同强度陶瓷丸喷丸强化对合金磨削表面进行了表面处理,并研究了疲劳性能和表面完整性状态。研究结果表明:在650℃下,当应力集中系数由Kt=1提高到Kt=1.7时,FGH96合金磨削状态疲劳极限由583MPa下降到465MPa;经过大强度喷丸强化后,Kt=1.7疲劳极限回复到530MPa;小强度喷丸强化对Kt=1.7疲劳极限无增益作用。大强度喷丸强化消除了加工刀痕,表面粗糙度略有增大,引入了深度达到100μm的残余应力场,在600MPa下疲劳源萌生于次表层,呈单源疲劳模式;小强度喷丸强化无法消除加工刀痕,在600MPa下疲劳源萌生于表层,呈多源疲劳模式。结果证明适宜的喷丸强化工艺可以缓解结构应力集中对粉末合金疲劳性能的削弱。

Effect of Shot Peening on Fatigue Performance Stress-Concentration Sensitivity of FGH96 Powder Metallurgy Superalloy

Ceramic shot peening using different intensities was applied on grinded surface of FGH96 powder metallurgy superalloy to research its effect on fatigue performance stress-concentration sensitivity.The fatigue tests and surface integrity statues were characterized.The results show that fatigue limit of grinding declines from 583MPa to 465MPa at 650 ℃ when the stress concentration factor increases from Kt=l to Kt=l.7.Shot peening using high intensity makes the Kt=l.7 fatigue limit edge up to 530MPa while low intensity has no gain for the Kt=l.7 fatigue limit.High intensity leads to the elimination of grinding marks,an increscent average roughness and an 100μm-depth residual stress profile,therefore the 600MPa fatigue cracks are initiated at the subsurface in a single source fatigue model.By contrast,low intensity hardly makes marks eliminated and the fatigue cracks are initiated at the surface in multiple sources fatigue model.The research proves that the suitable shot peening method can minish the weaken effect to fatigue performance by structural stress-concentration.