Toward developing remanufactured Ti6Al4V alloys with high fatigue crack growth resistance by in-situ cooling during laser remanufacturing

[Display omitted] •A novel approach to enhance the crack resistance in the inhomogeneous microstructure of remanufactured Ti6Al4V.•The crack resistance mechanism and the FCG behavior of inhomogeneous microstructure was investigated.•In-situ cooling process altered the fatigue crack propagation mechanism in RZ and HAZ, and diminish the anisotropy of RZ. The fatigue performance of remanufactured titanium alloy blade components has garnered significant attention in recent years. The repaired titanium alloy components using the direct energy deposition (DED) method exhibit structural differences, leading to an inhomogeneous microstructure that directly impacts the service life of the remanufactured component. The work presented here aimed to investigate novel approaches for enhancing the resistance to crack propagation and to gain a deeper insight into the fatigue crack propagation characteristics of the Ti6Al4V remanufactured interface with an inhomogeneous microstructure. The research focused on analyzing the microstructure evolution and fracture properties of remanufactured components using in-situ cooling. The results indicate that in-situ cooling has the potential to decrease the anisotropy of the repaired zone (RZ) and enhance the resistance to crack propagation in the heat-affected zone (HAZ) and base metal (BM). The high cooling rate associated with the in-situ cooling can elevate the presence of high-angle grain boundaries (HAGBs) in the RZ, diminish the phase transformation between the HAZ and BM, and decrease the size of the secondary α phase. The research contributes to a deeper comprehension of fatigue crack propagation in remanufactured components and provides a pathway for the improvement of fatigue performance of remanufactured titanium alloy.