Rejuvenation Heat Treatment of Nickel Base Superalloy Grade GTD111 after Long-Term Service via the Taguchi Method for Optimization

This research describes an optimization and rejuvenation of the heat treatment process for a nickel base superalloy grade GTD111 after long-term service. The aging heat treatment variables examined in this study included primary aging temperature, primary aging time, secondary aging temperature, and secondary aging time. The resulting materials were examined using Taguchi method design of experiments to determine the resulting material hardness test and observed with the hot tensile test, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The experimental results showed what happens following optimization with the heat treatment parameters of a primary aging temperature of 1120 °C, primary aging time of 3 h, secondary aging temperature of 845 °C, and secondary aging time of 24 h. The material, after rejuvenation heat treatment via optimization with γ′ particle characteristics, had a coarse square shape, spherical shape of γ′, and fine γ′ precipitate distributed on the parent phase, which affects the mechanical properties of the material. fine γ′ precipitate distributed on parent phase, which affects the mechanical properties of the material.