Available fatigue models are analyzed to assess gas turbine nozzle life due to thermal fatigue cycles experienced in operation. A nozzle retired from service made of cobalt base alloy FSX-414 experienced fatigue cracks during its operation period. Nozzle thermal stresses and strains generated during gas turbine transitions; startups and shut downs, determined in previous investigations are used for fatigue analysis and life assessment. A specialized software nCode was used for fatigue analysis and the Rainflow method to account for fatigue cycles. The fatigue life models of Manson-Coffin-Basquin, Morrow and Smith-Watson-Topper were compared assessing nozzle life in different critical zones of the vane and its union to the internal and external shrouds. Some similarities and deviations found among fatigue models are analyzed. Diagrams of nozzle life distribution within its body are provided. It was found that the nozzle zones having shortest life are located in the vane cooling ducts and transitions/unions between vane and shrouds.

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