Crack suppression and directional grain growth in M247 nickel-based superalloy via synchronous induction-assisted laser directed energy deposition

• Synchronous induction heating enables crack suppression of M247 superalloy. • Preheating and slow-cooling effects reduce thermal gradients and suppress crack. • Synchronous induction heating achieves directional growth length > 31 mm. • Numerical simulations predict directional growth capability for process optimization. Additive manufacturing of nickel-based superalloys, particularly for aeroengine blade repair, faces challenges such as cracking and uncontrolled microstructure due to high thermal gradient and rapid cooling. This study presents a synchronous induction-assisted laser directed energy deposition (SIA-LDED) method to address these issues in M247 superalloy. By integrating a moving disk-shaped induction coil with the laser heat source, precise control of the local temperature field was achieved, enabling crack suppression and enhancing directional grain growth. Numerical simulation uncovered that preheating and slow-cooling effects induced by synchronous induction heating effectively reduced thermal gradients, thereby suppressing crack formation. It can also be employed to predict directional grain growth capability for process parameters optimization. The optimized induction parameters (268 A, 10 kHz) promoted the directional grain growth with the length exceeding 31 mm. The numerical simulation revealed that the synchronous induction heating minimized the solidification rate and enhanced the directional grain growth capability. It breaks through the inherent limitation of LDED in achieving directional grain growth on the ordinary substrate (non-directional grain). Mechanical testing showed that the SIA-LDED can prevent premature fracture of the sample, which primarily originates from the defect elimination and γ′ phase refinement.