EBSD-Based quantitative correlation between microstructural features and hydrogen-induced cracking susceptibility in L415MS linepipe steels

The study examines hydrogen-induced cracking (HIC) susceptibility in two API L415MS steels processed under different thermomechanical conditions. Both steels were reheated at 1200 ± 20°C and finish rolled at 850 ± 20°C, but cooled at different rates: Specimen A at 20–22°C/s and Specimen B at 15–17°C/s. HIC testing showed no cracking in A, whereas B exhibited severe damage. EBSD analysis revealed that A had a higher recrystallized fraction (46% vs. 14.3%), greater high-angle grain boundary density (74.5% vs. 64.1%), dominant {101} texture, finer grain size (12 μm vs. 20 μm), and fewer deformed regions (18.4% vs. 34%). These features reduced hydrogen trapping and crack initiation, demonstrating that optimized processing significantly improves HIC resistance and sour-service pipeline integrity.