Research on laser gradient modified destressing restoration of aerial titanium alloy impairment

Abstract

To realise laser gradient modified distressing restoration of aerial titanium alloy impairment, experiments of functionally gradient reparative layers (FGRLs) and non-functionally gradient layers (N-FGLs) on Ti600 substrate by pulsed Nd:YAG had been carried out. The microstructures, phase composition and elementary distribution regularities of FGRL were investigated. The microhardness, thermal shock and thermal fatigue properties of FGRL and N-FGL were examined contrastively. It is found that a rapidly solidified microstructure consisting of in situ synthesised TiC reinforced phase distributed on FGRL substance evenly and dispersedly 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. The distribution of main alloy components is gradient and continuous, presenting the same composition and regularity to the originally preset alloy powder. FGRL has an average Vickers diamond hardness (HV) of ∼1450, 4·5–5 times of Ti600 substrate (310 HV), attributed to TiC primary dendrites. With the increasing of original Cr3C2 content, the number, size of arborescent crystal and microhardness increase obviously. Resisting thermal shock and thermal fatigue properties indicate that gradient transitional components and microstructure of FGRL can relax thermal stress effectively.