Transient liquid phase bonding of DD5 superalloy using a designed interlayer: microstructure and mechanical properties

Nickel based single crystal superalloy is currently widely used as the material for turbine blades in aerospace engines. However, metallurgical defects during the manufacturing process and damage during harsh environmental service are inevitable challenges for turbine blades. Therefore, bonding techniques play a very important role in the manufacturing and repair of turbine blades. The transient liquid phase (TLP) bonding of DD5 Ni-based single crystal superalloy was performed using the designed H1 interlayer. A new third-generation Ni-based superalloy T1 powder was mixed with H1 powder as another interlayer to improve the mechanical properties of the bonded joints. The results show that, such a designed H1 interlayer is beneficial to the improvement of shear strength of DD5 alloy bonded joints by adjusting the bonding temperature and the prolongation of holding time. The maximum shear strength at room temperature of the joint with H1 interlayer reached 681 MPa when bonded at 1 260 ℃ for 3 h. The addition of T1 powder can effectively reduce holding time or relatively lower bonding temperature, while maintaining relatively high shear strength. When 1 wt.% T1 powder was mixed into H1 interlayer, the maximum room temperature shear strength of the joint bonded at 1 260 ℃ reached 641 MPa, which could be obtained for only 1 h. Considering the bonding temperature and the efficiency, the acceptable process parameter of H1 + 5 wt.% T1 interlayer was 1240 ℃/2 h, and the room temperature shear strength reached 613 MPa.