In-situ small angle neutron scattering and ex-situ electrical resistivity to nondestructively monitor Aging of a nickel-based superalloy

In-situ small angle neutron scattering (SANS) and ex-situ electrical resistivity measurements were used to nondestructively monitor the precipitation of γ' precipitates in a polycrystalline nickel-based superalloy used as disk rotor material for gas turbine engines. Disk rotors manufactured from this superalloy are precipitation hardened to maintain high strength and fatigue resistance at temperatures greater than 60% of the alloy melting temperature. SANS and electrical resistivity are both useful nondestructive techniques that are sensitive to the evolving precipitate phase, γ in the superalloy. SANS measurements were taken for both ex-situ and in-situ heat treatment of the superalloy at 998 K (725 °C). Electrical resistivity measurements were taken for samples given ex-situ heat treatment, and the data were compared to quantitative microstructural information obtained from in-situ SANS. The electrical resistivity was found to be especially sensitive to the precipitate volume fraction, showing inverse power-law dependence. Both SANS and electrical resistivity may be used in the future to monitor the progression in the strengthening precipitate phases in superalloys due to heat treatment or thermal exposure during service.