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The effect of Hot corrosion on the mechanical behavior of high temperature alloys

Hot corrosion

Due to economical reasons or difficulty to find alternative, an increasing number of gas turbine operators are running on contaminated fuel. These contaminants have a deleterious effect on gas turbine components, and particularly on the turbine blades. Alkali salts (coming from the environment) associated with sulfur (coming from the fuel) form a melted compound that sticks onto the blade and destroys the internal structure of the material, leading to the failure of the blade by hot corrosion. The ejection of one blade means an exchange of the engine resulting in a costly downtime.

This work focus on the reproduction of the failing environment in order to 1) predict the lives of various coatings and 2) develop a suitable coating that will act as a protection of the blade surface.

In order to study the points mentioned above, a rig has been set-up to reproduce the failure environment. The turbine section of the engine is undergoing high temperature and due to centrifugal speed, also large stress. A furnace and a vertical actuator are reproducing these two factors. The sample are coated with salts while sulfur is injected in the chamber holding the sample. Experiment are typically lasting below 100h. Examination of the reaction layer is done with SEM with EDS and X-ray. Beam stiffness is experimentally assessed throughout the experiment.

The upper side of the rig is shown in the picture below.

Stress Corrosion Rig

 

Because the loading is made in 4-point bend, a non-uniform stress distribution requires the use of a finite element model to infer the relation with the reaction layer. Furthermore, the use of non isotropic material (SC) would help the interpretation of the results obtained. carousel

 

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