经不同表面改性处理的钛合金的微动疲劳和微动磨损行为对比研究

对比研究了钛合金微动疲劳(FF)和微动磨损(FW)失效行为,考察了表面喷丸强化和氮化等表面处理对钛合金微动疲劳和微动磨损性能的影响,探讨了钛合金微动磨损和微动疲劳性能的相关性.结果表明,钛合金微动疲劳和微动磨损损伤表面形貌特征相似;当微动位移幅较大、微动区发生整体滑动时,微动接触区磨损有利于延缓微动疲劳裂纹萌生;而在小位移幅、部分滑移情况下,局部磨损促进微动疲劳裂纹萌生.利用喷丸强化在钛合金表面引入残余压应力,可以在降低摩擦系数的同时,提高钛合金抗微动疲劳和微动磨损失效的能力;氮化处理后钛合金表面硬度提高,有利于改善其微动磨损性能,但表面韧性降低导致抗微动疲劳能力降低.因此,在提高表面硬度的同时,不应忽视表层韧性的降低对钛合金微动疲劳性能的不利影响.

Comparative Study on the Fretting Fatigue and Fretting Wear Behaviors of Titanium Alloy Subject to Various Surface Modifications

The fretting fatigue (FF) and fretting wear (FW) behaviors of a Ti alloy were comparatively investigated. The effects of shot peening and nitriding on the fretting wear and fretting fatigue behaviors of the Ti alloy were examined. And the correlation between the fretting wear and fretting fatigue behaviors of the Ti alloy was explored. It was found that the FF Ti alloy surface had similar morphology to that of the FW Ti alloy surface. The fretting wear at the fretted contact region contributed to delay the FF crack initiation as the fretting amplitude was large enough and the fretted zone was characterized by complete slip. While in the mixed stick and slip regime corresponding to a small fretting amplitude, the localized fretting wear accelerated the FF crack initiation. The shot-peening induced surface residual compressive stress of the Ti alloy was beneficial to decreasing the friction coefficient and increasing the fretting fatigue resistance and fretting wear resistance. Nitriding of the Ti alloy led to the increase of the surface hardness, which was beneficial to increasing the fretting wear resistance. However, the decreased surface toughness of the Ti alloy after the nitriding was harmful to the fretting fatigue resistance. Therefore, it was imperative to get rid of the negative effect of the decreased surface toughness on the fretting fatigue resistance of the Ti alloy when using surface modification techniques to increase its surface hardness and fretting wear resistance.