Mechanical Properties in GTD-111 Alloy in Heavy Frame Gas Turbines

Nickel-based superalloys are extensively used in manufacturing hot gas path components in industrial gas turbines used for power generation. Specifically, GTD-111 DS is one of the widely used alloys used in manufacturing the hot gas path rotating components. These components are subjected to extreme operating environments resulting in creep, oxidation, and fatigue of the components during operation. After continued operation, these damage modes need to be repaired and the components go through extensive repair processes, which include several heat treatments to recover the mechanical properties of the base material (GTD-111 DS) lost during operation. The heat treatments used during repair by the different repair vendors can vary widely in terms of temperature, time and the sequence as well. This study focuses on understanding the differences in the effects of the heat treatments (partial solution, full solution, HIP and full solution) to the base material in terms of microstructure-mechanical property relationships. Results indicate that HIP and full solution resulted in refined microstructures and improved mechanical properties compared to the heat treatments involving partial solution or full solution only. Microstructuremechanical property relationships suggest that components that need to be repaired beyond OEM recommended repair intervals benefit from the HIP and full solution heat treatments.