中文摘要：

为了探讨喷丸、喷砂与HVOF WC-17Co涂层表面完整性对Ti5A15Mo5V1Cr1Fe（TC18）钛合金疲劳性能的影响规律和作用机制,利用X射线衍射仪（XRD）、表面粗糙度仪、显微硬度计、扫描电子显微镜（SEM）以及X射线应力测试仪等分析了喷丸、喷砂及其复合超音速火焰喷涂（HVOF）WC-17Co涂层的表面完整性,利用旋转弯曲疲劳试验机研究了上述表面处理对TC18钛合金疲劳性能的影响规律.结果表明,喷丸预处理比喷砂预处理能够使TC18钛合金表面获得更好的表面完整性,因而显著提高了TC18钛合金的疲劳抗力,而喷砂处理对TC18钛合金疲劳抗力无明显影响.喷丸后进行HVOF WC-17Co涂层处理使TC18钛合金疲劳寿命提高6倍,原因归于喷丸层内仍保留数值较大、分布较深的残余压应力,有效延缓疲劳裂纹的萌生和早期扩展.喷砂后进行HVOF WC-17Co涂层处理使TC18钛合金疲劳抗力显著降低,原因是HVOF过程的高温效应使喷砂层内残余压应力场松弛,使喷砂表面缺口效应和损伤的不利影响作用突显,加之WC-17Co涂层韧性低、表面粗糙度大、存在孔洞型缺陷,不利于抗疲劳性能.

英文摘要：

In order to investigate the effect of surface integrity of shot peening（SP）,grit blasting（GB）and HVOF sprayed WC-17Co coating on the fatigue behavior of Ti5Al5Mo5V1Cr1Fe（TC18）alloy,the surface integrity of the surface treatment was evaluated by using X-ray diffraction （XRD）,surface roughness meter,microscopic hardness tester,scanning electron microscopy （SEM）and X-ray stress test instrument.The fatigue property of TC18 alloy influenced by above surface treatment was studied by using rotating bending fatigue test machine.The result indicates that the surface integrity after SP treatment is better than that after GB process.Therefore,the fatigue life of TC18 titanium alloy increases dramatically by SP,but there is no significant change of fatigue life by GB treated TC18 alloy.The fatigue life of HVOF WC-17Co coated TC18 alloy with SP pretreatment is increased six times larger than that of the alloy substrate.This is attributed to the retained large residual compressive stress in the SP layer.The crack initiation and earlier propagation are delayed by the residual compressive stress.However,the fatigue life of HVOF WC-17Co coated TC18 alloy with GB pretreatment is obviously decreased.This is due to the low toughness,large surface roughness,and pore defects of WC-17Co coating.The relaxation of residual compressive stress influenced by the HVOF high temperature process and the notch effect in GB layer are also the reasons.