CMAS Penetration, Thermal Insulation Degradation, and Life Prediction of Thermal Barrier Coatings

Dear Colleagues,

The pervasive challenge of calcium–magnesium–aluminosilicate (CMAS) deposition and penetration has emerged as one of the most critical threats to the performance and durability of thermal barrier coatings (TBCs) in modern gas turbines and aero‑engines. When ingested siliceous debris (e.g., sand, dust, volcanic ash) melts under high‑temperature operations, the resulting CMAS melt can rapidly infiltrate the porous/columnar microstructure of TBCs, leading to severe degradation mechanisms such as premature coating stiffening, accelerated sintering, loss of strain tolerance, and ultimately, spallation failure. This phenomenon not only compromises the thermal insulation capability of TBCs but also significantly shortens their service life, imposing substantial limitations on engine efficiency, operational safety, and maintenance cycles.

Addressing the CMAS challenge requires a multidisciplinary effort that spans materials design, advanced processing, in‑depth characterization, and predictive modeling. Innovations in CMAS‑resistant coating architectures—including novel ceramic compositions, engineered porosity, sealed or sacrificial top layers, and functionally graded designs—are actively being explored to mitigate penetration. Concurrently, understanding the complex thermochemical interactions between CMAS melts and coating materials, as well as quantifying the consequent degradation of thermal conductivity and mechanical properties, is essential for developing robust life‑prediction frameworks. Advanced experimental techniques, such as in‑situ thermal testing, micro‑structural tomography, and high‑temperature corrosion simulation, combined with multi‑scale modeling approaches, are paving the way for more accurate assessment and forecasting of TBC performance in CMAS‑rich environments.

This Special Issue, entitled “CMAS penetration, Thermal Insulation Degradation, and Life Prediction of Thermal Barrier Coatings”, aims to consolidate the latest fundamental and applied research on the interrelated effects of CMAS attack  thermal property evolution, and coating lifetime. We invite original research articles, comprehensive reviews, and case studies that contribute to the following or related themes:

• Mechanisms of CMAS deposition, penetration, and thermochemical interaction with TBC materials.
• Design and development of CMAS‑resistant coating systems: novel ceramics, multilayer/graded structures, surface modifications, and hybrid coatings.
• Experimental characterization of thermal insulation degradation under CMAS exposure: evolution of thermal conductivity, emissivity, and thermal‑cycle performance.
• Micro‑structural, chemical, and mechanical evolution of TBCs subjected to CMAS penetration and high‑temperature exposure.
• Modeling and simulation of CMAS‑induced degradation, including penetration kinetics, stress generation, and property deterioration.
• Advanced life‑prediction methodologies: integration of damage models, sensor data, and machine learning approaches for reliability assessment under CMAS conditions.
• Field studies, engine‑test validations, and development of accelerated laboratory testing protocols for CMAS‑affected TBCs.

By bringing together contributions from academia, research institutes, and industry, this Special Issue seeks to advance the scientific understanding and engineering solutions needed to enhance the CMAS resistance and operational reliability of next‑generation thermal barrier coatings.

Dr. Li Shi
Prof. Dr. Qingbo Wen
Prof. Dr. Fan Zhang
Guest Editors

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• thermal barrier coatings
• thermal insulation degradation
• CMAS deposition and penetration
• life prediction