Hot corrosion failure in the first stage nozzle of a gas turbine engine

• A failure analysis of the first stage nozzle in a gas turbine engine is presented.
• Fractography studies showed that fractures are occurred due to HTHC and thermal fatigue mechanisms.
• FEM results showed good agreement between the high stress region and the broken place.
• Intergranular fracture occurred in the trailing edge of blade.
• The blade surface had a greenish-tone oxide layer resulted from the NiO formation.

First-stage nozzles of gas turbines, which are the first elements after the combustion chamber, encounter hot gases from the combustion process and have the task of directing the fluid path and increasing the velocity of combustion products. This paper reports on the incidence and failure of the first-stage nozzles of a gas turbine in September 2013 at a seaside pump-house located in the South-West of Iran. The nozzle was made of nickel-based superalloy Nimonic105. Due to nozzle failure, the turbine was damaged severely. The cause of nozzle failure was investigated. The results of visual inspection, XRD analysis of deposits on the blade airfoil, SEM images and EDAX analysis showed the characteristics of hot corrosion. Finite-element analysis (FEM) revealed that the cause of blade trailing edge failure was thermal stress leading to thermal fatigue, which accelerated nozzle blade failure in addition to the hot corrosion.