Creep crack growth in alloy 247LC‐DS

Creep crack growth experiments were performed at 750°C, 850°C, and 950°C on nominally 3 and 12.7 mm thick compact type specimens of alloy 247LC‐DS, a Ni‐base superalloy used for hot‐section gas turbine blades. The primary crack plane was transverse to the solidification direction. The crack path–microstructure interaction was characterized. Crack growth occurred in a creep‐ductile manner and data analyses utilized time‐dependent fracture mechanics. No measurable crack growth occurred at 750°C. Cracks grew by formation, growth, and coalescence of cavities on interdendritic carbides in both the primary crack plane and normal to said plane at 850°C and 950°C. The variability in the crack growth rate was higher in thicker specimens, but the mean creep crack growth rate versus C t relationship in 247LC‐DS was neither sensitive to test temperature ≥850°C nor specimen thickness. Quantitative relationships between da/dt and C t were derived for mean, upper, and lower bound creep crack growth rate trends.