Creep failure mechanisms and lifetime prediction of directionally solidified superalloy turbine blades

With the continuous increase in turbine speed and inlet temperature of aircraft engines, creep fracture has become one of the main failure modes of turbine blades under high-temperature service conditions. To accurately predict blade life, uniaxial tensile creep tests were conducted on a second-generation nickel-based directionally solidified superalloy at 860 °C, 950 °C, and 1050 °C. The fracture morphology and microstructure were examined using SEM and TEM, revealing that the dominant fracture mechanisms from the aspects of dislocation movement, microstructural rafting, and void growth. A creep damage constitutive model based on crystal plasticity theory was used to fit the creep curves, and temperature interpolation showed that the predicted life across a wide temperature range fell within a 1.5-times error band, demonstrating good accuracy. Additionally, a finite element model of a columnar crystal blade with random crystal orientations was established. The simulation revealed significant creep damage concentration in the U-shaped channel inside the blade. Using the bone point stress method to evaluate life in this region, it was found that changes in crystal orientation affected the bone point location, with stress ranging from 300.1 MPa to 334.5 MPa. The shortest predicted creep life was 1046 h, providing an important reference for blade life design.