Analysis of the Recovery Potential Through Repair of Key Tensile Properties for a Second Generation Ni-Based SX Superalloy Exposed to Simulated Routine Service Conditions

Nickel-based single-crystal turbine components used for aero-engine turbine bladesTurbine blades are exposed to cycles of temperature and stress during routine service. High temperatureHigh temperature exposure (exceeding about 950 °C) results in a transformation of the precipitationPrecipitation from cuboidal to coarsened morphology. The coarsened microstructureMicrostructure has a detrimental effect on the mechanical propertiesMechanical properties and, therefore, lifespan of the component. In the present study, simulated service conditions (approximated by non-isothermal creepCreep tests) were applied to SC2000 specimens. The effects of the non-isothermal creepCreep deformation and a rejuvenationRejuvenation heat treatmentHeat treatment on the alloy’s microstructureMicrostructure and tensile and creep propertiesCreep properties were analyzed. Non-isothermal creepCreep tests were performed with a base temperature of 900 °C and a peak temperature of 1100 °C. SEMScanning Electron Microscopy (SEM) analysis confirmed a quick deterioration of the microstructureMicrostructure exposed to the simulated service coupled with a marked dislocations activity around the precipitatesPrecipitates. In order to restore the initial properties, a super-solvus rejuvenationRejuvenation heat treatmentHeat treatment was applied after deformation. The rejuvenationRejuvenation process successfully restored the initial precipitatesPrecipitates morphology and the yield strength, while no improvement in creep propertiesCreep properties was observed. Hypotheses and investigations are presented to explain this effect.