Fig. 1. Laser working state (a), schematic diagram of the laser scanning path, (b) repaired DD32 alloy sample (c) and specimen geometry for tensile test (d).

Fig. 2. Microstructures of the repaired DD32 single superalloy (a), dendrites at the deposited area (b), at the joint area (c) and at the substrate area (d). (b), (c) and (d) are taken from the area of box ①, ② and ③ in (a). Green thin lines in (a) represent the pool line. The area between green dotted lines in (a) draw HAZ. The green dotted line in (c) represents the pool line.

Fig. 3. SEM images of γ′ (a, b) and the MC carbide (c, d, e, f). (a) and (c) at the substrate area, (b) and (d) at the deposited area, (e) at the molten pool line between deposited and substrate, (f) at high cladding layer of the deposited area.

Fig. 4. SEM images of the eutectic at the bottom of molten pool line (a, b), at first layer (c), at Nth cladding layer (d, e), on both sides of the molten pool line (f). The magnification of the area with orange boxes in (a) and (d) is shown in (b) and (e).

Fig. 5. SEM images of porosity at substrate area (a) and deposited area (b).

Fig. 6. SEM images of γ′ in the core-dendrit (a, c, e) and inter-dendrite region (b, d, f). (a) and (b) are at HAZ close to the molten line, (c) and (d) are at the middle of the HAZ, (e) and (f) are at substrate area.

Fig. 7. Tensile results of repaired DD32 single crystal at various temperatures: (a) typical tensile true stress-strain curves; (b) tensile strength; (c) elongation; (d) strain-hardening exponent.

Fig. 8. SEM images of tensile fractured surface at (a) 660 °C, (b) 760 °C, (c) 900 °C, (d) 1000 °C and (e) 1100 °C.

Fig. 9. SEM images of the vertical section of tensile-ruptured samples at 660 °C (a, a1, a2) and 760 °C (b, b1, b2) of substrate area. (a1) and (b1) show the broken MC carbide. (a2) and (b2) show the MC distributed along the fracture surface.

Fig. 10. SEM images of the vertical section of tensile-ruptured samples at 900 °C (a, a1, a2), 1000 °C (b, b1, b2) and 1100 °C (c, c1, c2) of deposited area. (a1, b1, c1) show the pore. (a2, b2, c2) show the γ′ networks.

Fig. 11. TEM images of deformation microstructures of the repaired DD32 single crystal at (a) 760 °C, (b) 900 °C and (c) 1100 °C.

Fig. 12. Illustration of the formation mechanism of stacking fault (a) and formation mechanism of dislocation network (b).

Fig. 13. SEM image of the joint area (a) and EPMA image of Re element distribution in the joint area (b).

Fig. 14. (a) Schematic of the evolution of the cooling rate and volume fraction of (γ+ γ′) eutectic and (b) illustration of the distribution of the (γ+ γ′) eutectic with the increase of deposited height.

Fig. 15. Illustration of the fracture mechanism at different temperatures.