Enhancement of the mechanical properties of nickel-based single-crystal alloy based on near [001]-oriented growth microstructures via laser cladding

Abstract

To achieve crack repair in a Ni-based single-crystal alloy, a GH4738 repairing layer was cladded onto the surface of the single-crystal DD5 alloy using the laser cladding method. The effects of the laser power and scanning speed on the microstructures and mechanical properties of the repaired sample were studied. The results showed that the typical γ/γ′ phases and carbide were formed in both the repairing layer and substrate, and the carbide primarily belonged to the Ta-rich compound. An increase in the cladding power caused the repairing layer to crack. When the laser power was 1200 W and the cladding speed was 2 mm/s, the tensile strength and elongation of the repaired sample were 1126.1 MPa and 12.2 %, respectively. The fracture mechanism was primarily a cleavage fracture. The grain growth direction of the repairing layer tended toward the [001] direction, and no noticeable difference in the orientation from that of the substrate was observed. The lattice mismatch between the phase interface of the repairing layer and substrate was small. This indicated that the growth of the γ/γ′ phases between these two regions maintained a coherent relationship, which was the primary reason for the excellent mechanical properties of the repaired samples.