Thermal damage evaluation of nickel-based superalloys based on ultrasonic nondestructive testing

Ultrasonic nondestructive technique was used to assess the thermal degradation in a nickel-based superalloy in this research. Thermal exposure tests were carried out at an elevated temperature of 1050 °C to introduce controlled levels of damage, while the linear ultrasonic parameters (sound velocity and attenuation coefficient) and nonlinear ultrasonic parameters were observed. The evolution of the microstructure and the subsequent degradation in macro-mechanical properties of the material were quantitatively researched. The results suggest that the nonlinear parameters show hypersensitivity and high-credibility compared with the traditional linear parameters. The monotonic increase of the ultrasonic nonlinear parameters was explained by the evolution of the lattice mismatch and the volume fraction of the γ′ and carbide precipitated phase based on the dislocation precipitation interaction model.