IN 738 LC microstructure optimization with heat treatment and simulation to improve mechanical properties of turbine blades

Boyraz, Mustafa Tarık
IN 738 LC is a Ni-based superalloy that is employed mostly in nozzle guide vanes and turbine blades in gas turbines. In these parts of gas turbines, material is exposed to high temperatures and the highly corrosive environment. Therefore, improvement in high temperature strength (yield strength, creep strength, tensile strength) and corrosion resistance are extremely important. In this study, effect of heat treatment and aluminide coating parameters to IN 738 LC microstructure were investigated. Both experimental and simulation studies were performed to improve materials microstructure and optimize its yield strength. Microstructure evolution during heat treatments and aluminide coating was simulated using JMAT PRO software and simulation results were compared to experimental results. The experimental microstructure information obtained from aluminide coating and heat treatment results were used as input to a physical model that was formed to estimate yield strength of IN 738 LC samples with different microstructures. The result of this model was compared with experimental tensile test literature findings and JMAT PRO yield strength estimations. Additionally, surface growth and diffusion during the aluminide coating were simulated using DICTRA software. The composition profile and coating thickness results of simulations were compared to experimental aluminide coating results. The purpose was to achieve a simulation model capable of estimating coating composition profile and thickness for given experimental conditions since experimental aluminide coating is a costly and time-consuming process.


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Citation Formats
M. T. Boyraz, “IN 738 LC microstructure optimization with heat treatment and simulation to improve mechanical properties of turbine blades,” M.S. - Master of Science, Middle East Technical University, 2018.