Role of scan strategies in modulating micro and macro-cracking in CM247LC processed by powder bed fusion–laser beam

This study investigates the influence of different scan strategies, specifically scan rotation (0°, 67°, and 90°) and remelting (Double 67° and Double 90°), on the microstructure evolution, residual stress distribution, cracking behavior and mechanical properties of CM247LC superalloy fabricated by powder bed fusion–laser beam (PBF–LB). Scan strategy significantly impacts micro-cracking susceptibility, crystallographic texture, and residual stress distribution. The micro-cracking which is confirmed as solidification cracking occurred in high angle grain boundaries. The micro-cracking decreased progressively from ~2.50 mm/mm2 (0° strategy) to ~0.30 mm/mm2 (Double 90°), accompanied by improved strength-ductility synergy. The micro-cracking reduction was attributed to promotion of <100> crystallographic texture along build direction and a ~20% decrease in high angle grain boundary fraction. Post heat-treatment macro-cracking in cruciform geometry, was found to be influenced by residual stress distribution and as-built microstructure. Remelted samples with higher residual stress (808 MPa along build direction for Double 90°) exhibited severe macro-cracking (19.66 mm), whereas the 0° strategy with moderate residual stress (729 MPa along build direction) underwent minimal macro-cracking (2.15 mm). Macro-cracking in most strategies (67°, 90°, Double 67°, and Double 90°) occurred near stress concentrator notches of the cruciform, however the 0° strategy exhibited an anomalous cracking pattern, with macro-cracking occurring transverse to melt tracks at the top surface of the cruciform. This work demonstrates the critical importance of controlling residual stress formation through scan strategy optimization to obtain defect-free heat-treated CM247LC components produced by PBF–LB.