Modelling of microstructural evolution in multi-layered overlay coatings

Area of Science:

• Materials Science and Engineering
• Surface Engineering
• Computational Materials Science

Background:

• Industrial gas turbines require robust materials for high-temperature corrosion protection.
• Multi-layered coatings offer enhanced performance but their microstructural evolution is complex.
• Understanding coating degradation is crucial for extending turbine lifespan.

Purpose of the Study:

• To develop and validate a computational model simulating microstructural evolution in functionally graded, multi-layered coatings.
• To predict phase and concentration profiles within coating systems under operational conditions.
• To assess the model's utility for designing advanced coatings for industrial gas turbine aerofoils.

Main Methods:

• Development of a simulation model integrating diffusion, equilibrium thermodynamics, and oxidation.
• Application of the model to a multi-layered coating system (Al-rich outer, Cr-enriched middle, MCrAlY inner) on a superalloy substrate.
• Comparison of model predictions with experimental data from the coated system.

Main Results:

• The model successfully predicted concentration distributions within the multi-layered coating.
• Key microstructural features observed experimentally were accurately reproduced by the simulation.
• The model demonstrates a strong capability to forecast coating behavior.

Conclusions:

• The developed model is a valuable tool for predicting the microstructural evolution of multi-layered coatings.
• This predictive capability can guide the design and optimization of protective coatings for industrial gas turbines.
• The findings support the use of such advanced coatings on gas turbine aerofoils for improved durability.