Laser cladding of IN625 on Rene125 superalloy: Effect of tailored post- heat treatments on interfacial properties

• First three-stage solution specifically designed for IN625-on-Rene125 turbine blade repairs: Dissolves secondary phases at 1220°C, suppresses brittle precipitation via controlled air-cooling to 590°C, and relaxes interfacial stresses through dislocation recovery during slow cooling. • Directly addresses thermal expansion coefficient mismatch: Achieves complete dissolution of secondary phases while minimizing detrimental thermal/mechanical stresses at the interface, preventing cracking. • Enables uniform precipitate distribution: Establishes supersaturation conditions for aging without residual stress reaccumulation, bridging the gap between microstructural control and stress mitigation in superalloy repairs. This study systematically investigates the laser deposition of IN625 alloy onto the cast superalloy Rene125, with a focus on optimizing a tailored multi-stage heat treatment cycle to control microstructure, eliminate brittle phases, and mitigate residual stresses at the Interface. Post-deposition, samples underwent a heat treatment protocol comprising solutionizing at 1220°C for 2 hours, air-cooling to 590°C, and subsequent controlled furnace cooling. This targeted thermal cycle fully suppressed Nb and Mo segregation within the IN625 cladding, transforming the initial dendritic microstructure into a homogeneous structure. At 1220°C, metastable M₂₃C₆/M₆C carbides dissolved, while stable MC carbides (1–3 μm) precipitated at grain boundaries during furnace cooling. Residual stresses at the Interface were reduced from 253 MPa to 4 MPa (98% reduction), demonstrating the efficacy of the proposed approach. The findings underscore that appropriately designed post-deposition heat-treatment cycles can yield substantial improvements in metallurgical bond quality and potentially extend fatigue life by up to 3.96 times in superalloy systems, thereby providing a strategic pathway for optimizing additive manufacturing processes in high-temperature applications.