航空钛合金激光3D梯度改性去应力修复研究

Research on Laser Gradient Modified Destressing Restoration of Aerial Titanium Alloy Impairment

为实现航空钛合金关键结构的改性去应力修复，在钛合金表面Nd：YAG激光制备了梯度改性修复层，扫描电镜（SEM）观察了微观组织，用能谱分析仪（EDAX）分析了元素成分和含量，测量了抗热震和热疲劳性能。结果表明，修复层微观组织主要为粗大和不完整的树枝晶、相对较细小的等轴和近等轴晶及细小短纤维状形态；随Cr3C2含量增加，树枝晶的数量、大小均呈上升趋势。梯度修复层比传统复合涂层具有更优异的抗热疲劳和热震性能。修复层表面氧化膜均匀致密，主要为连续的短纤维状组织，Ti600基体的氧化膜主要为疏松的金红石结构的颗粒状TiO2晶粒，以多面体规则形状堆垛，且晶粒粗大。

To realize laser gradient modified destressing restoration of aerial titanium alloy impairment, experiments of functionally gradient reparative layers （FGRL） and non functionally gradient layers （N-FGL） on Ti600 substrate by pulsed Nd：YAG have been carried out. The microstructures and elementary distribution regularities of FGRL are investigated. The thermal shock and thermal fatigue properties of FGRL and N-FGL are examined contrastively. It is found that a rapidly solidified microstructure consisted of in situ synthesized TiC reinforced phase distributed on FGRL in the form of globular grains has three main different shapes： bulky or imperfect arborescent crystal, fine or approximately equiaxial crystal and chopped fibriform crystal. With the increasing of original Cr3C2 content, the number and size of arborescent crystal increase obviously. Resisting thermal shock and thermal fatigue properties indicate that gradiently transitional components of FGRL can relax thermal stress effectively. The main surface oxidation morphology of FGRL possesses densely fine fibrous crystal. Otherwise, that is uniformly polygonal and crassitude TiO2 crystal to Ti600.