Design Framework for Optimized Multifunctional Coatings

Overall: This work shows an enhanced ICME (Integrated Computational Material Engineering) and lifing model/method used for Optimizing Multifunctional Coatings for high temperature thermal/environmental Barrier Coatings (TBC/EBC).  Extended durability/reliability and life was achieved by minimizing thermal conductivity and residual stresses/strains.  Maintenance and part replacement was also determined.

Method: A multiphysics-based multi-objective topology optimization methodology, and virtual design of experiment (DOE), random sampling methodology was developed to design multifunctional materials including high temperature special technology coatings for use in engine/aircraft high temperature exhaust regions.  The innovation centers around:  1) Thermal Modeling (Zeroth Order Model) predicting material thermal history profile, voids, densities, conductivities for each layer of the TBC during coating process for Plasma Spraying and Electron Beam-Physical Vapor Deposition (EB-PVD); 2) Material Modeling of Coating, Bond, and Substrate predicted material performance (strength, stiffness, residual stresses and strains) vs. temperature considering the effect of defects; 3) Structural Analysis and Durability and Damage Tolerance predicting coating and substrate life, failure type such as spallation, oxidation/corrosion, and mass loss during thermo-mechanical in-service loading;  and 5) Single or Multiple Objective Optimizations to maximize durability, minimize residual stress, and enhance coating life.  Verification was performed using test data on TBC systems under thermal mechanical loading.

Findings: Thermal conductivity and residual strains were minimized 41% and 27%, respectively for APS 8YSZ TBC with MCrAlY bond over Waspaloy and Inconel substrate considering as variables Yttria (mol.%), number of layers, total thickness, substrate initial temperature, and coating initial temperature.  The life and maintenance of optimized coupons and F15/F16 Seals and Flaps were also predicted and optimized.

KEYWORDS: 1) TBD Coating Design, 2) Thermal/Environmental Barrier Coating (TBC/EBC), 3) ICME computational models; 4) Effect of defects, 5) Multi-Physics Progressive Damage Analysis durability/reliability; 6) Thermal history profile, 7) Extended life, Retirement for Cause.