<p>Cobalt-based superalloys are widely employed in high-temperature applications, such as gas turbines, owing to their exceptional mechanical properties and resistance to corrosion and creep. However, these alloys are prone to microstructural degradation during service, which can lead to a reduction in strength, ductility, and creep resistance. Heat treatment is a valuable strategy for rejuvenating the microstructure of degraded cobalt-based superalloys, restoring their original properties and extending their service life. This study investigated the impact of heat treatment on the microstructure and mechanical properties of damaged first stage gas turbine nozzles fabricated from ECY768 cobalt-based superalloy. The blades were subjected to heat treatment at 1100°C for 3, 4, and 6 hours. Microstructural characterization was conducted using optical microscopy, scanning electron microscopy, and X-ray diffraction (XRD). Mechanical properties were assessed through microhardness testing. The results indicated that the secondary carbides were dissolved and uniformly dispersed within the matrix following 6 hours of heat treatment at 1100°C. This resulted in a decrease in hardness from 420 ± 16 to 316 ± 12&#xa0;HV. XRD analysis confirmed the dissolution of secondary carbides into the matrix after 6 hours of heat treatment. The findings of this study demonstrate that heat treatment at 1100°C for 6 hours followed by air cooling is an effective method for rejuvenating the microstructure and mechanical properties of damaged first stage gas turbine nozzles composed of ECY768 cobalt-based superalloy. This heat treatment cycle results in the dissolution of secondary carbides, leading to a decrease in hardness but also enhancing the strength and ductility of the alloy.</p>