Synergistic crack suppression mechanism of high-temperature preheating assisted laser cladding for MAR-M247 turbine blades

MAR-M247, a Hf-rich nickel-based superalloy, is widely used for turbine blades, but its high thermal cracking sensitivity limits laser cladding repair, which traditionally requires preheating above 1000 °C. To address this, a synergistic strategy combining process parameter control and induction preheating was proposed to achieve crack-free laser cladding. The effects of preheating temperature and linear energy density on crack formation, microstructure evolution, and dendritic spacing were investigated using optical microscopy, SEM, EDS, and industrial CT. The solidification path and elemental segregation were analyzed to reveal the thermal cracking mechanism. A random forest model with interval-based data augmentation was developed to predict crack probability for small sample sets. Results indicate that thermal cracks include both solidification and liquation cracks, initiated by segregation at grain boundaries forming MC carbides and γ/γ′ eutectic phases, which reduce cohesion. Preheating temperature shows a non-monotonic effect on substrate dendritic spacing, with optimal crack suppression at 948–990 °C and linear energy density of 23.1–27.8 J/mm. This study clarifies the micro-mechanisms of thermal cracking and provides a reliable intelligent prediction method for process parameter optimization in MAR-M247 laser cladding.