Interface-Driven Fatigue Failure: Quantitative Assessment of Laser-Remanufactured Inconel 625 Coatings Under Dry Rolling/Sliding Contact

Remanufacturing damaged components with high-performance materials often produces heterogeneous coating–substrate interfaces, which can substantially influence the rolling contact fatigue performance of repaired components. In this study, the fatigue behavior of laser-remanufactured Inconel 625 (In625) coatings was systematically investigated using different substrate materials. Particular attention was paid to the effects of substrate selection and interfacial heterogeneity on crack initiation, interfacial damage accumulation, and cyclic contact failure under dry rolling-contact conditions. Two quantitative models were developed to evaluate the nominal strength and critical damage of the coating–substrate systems, respectively. The proposed models were validated against available interfacial failure and experimental data, and the relative fatigue performance of five In625/substrate systems was comparatively assessed. Rolling-contact-fatigue tests were subsequently conducted using different substrate materials, followed by detailed fractographic characterization of the coating surfaces and coating–substrate interfaces. The experimental results showed good agreement with the model predictions, confirming the effectiveness of the proposed evaluation framework. The results indicate that the fatigue failure behavior of laser-remanufactured In625 coatings is governed by the competition between fatigue damage accumulation induced by the maximum surface contact stress and interfacial damage accumulation associated with the maximum interfacial shear stress. Furthermore, the relationship between material-matching factors and interfacial critical damage was clarified. Based on the established interfacial fatigue-damage evolution model, the effects of material-matching factors on interfacial fatigue life were quantitatively determined. The findings demonstrate that substrate selection and heterogeneous interface properties play decisive roles in controlling crack initiation and cyclic contact failure in laser-remanufactured In625 coatings under the investigated dry-contact conditions.