Thermal Barrier Coatings (TBCs): Advanced Heat Protection for Industrial Applications

Microstructure of EBPVD (Electron Beam Physical Vapor Deposition) thermal barrier coating produced by Linde Advanced Material Technologies for aircraft engine blades and vanes.

Thermal Barrier Coatings (TBCs) are critical for industries reliant on high-performance coatings to safeguard components under extreme thermal stress. TBCs advance industrial efficiency, enhance component performance, and help promote environmental sustainability. Application methods include Electron Beam Physical Vapor Deposition (EBPVD) and Air Plasma Spray (APS) technology. It also highlights the critical role of these coatings in various sectors, including aerospace, power generation, automotive, and advanced manufacturing.

What are Thermal Barrier Coatings?

Thermal Barrier Coatings (TBCs) are coatings that insulate metal components (such as in gas turbine blades or aircraft diesel engines) and allow them to operate under extremely high temperatures. TBCs exhibit excellent thermal insulation properties, which are crucial for improving thermal efficiency and reducing thermal stresses during operation.

Understanding Thermal Barrier Coating Fundamentals

Thermal barrier coatings are multilayer, consisting of a metallic bond coat and a ceramic top coat applied on the substrate of interest. The ceramic topcoat, crucial for providing thermal protection, is characterized by its low thermal conductivity (<2 W/m/K), strain-compliant, and ceramic structure. Meanwhile, the bond coat not only acts as an oxidation and corrosion resistance barrier but also enhances adhesion between TBCs and substrate.

This is particularly vital in managing thermal cycling and stresses common in high-temperature applications such as gas turbines and turbine blades used in power generation.

Key Properties and Performance Characteristics

Several properties make thermal barrier coatings extremely effective in their function, offering a multitude of benefits:

• Excellent thermal insulation properties: TBCs help reduce heat transfer from high-temperature areas by providing low thermal conductivity, ensuring efficient exhaust heat management.
• Thermal cycling and phase stability: Able to withstand repeated changes in temperature, TBCs maintain phase stability even under extreme thermal cycling.
• Thermal shock resistance: They exhibit strong resistance to sudden temperature changes, minimizing the risk of material failure due to thermal shock.
• Corrosion resistance: TBCs provide a barrier against corrosive elements at high temperatures, enhancing component durability.

Key Functions in High-Temperature Applications

Thermal barrier coatings provide invaluable utility in high-temperature applications. Their excellent thermal insulation properties and low thermal conductivity ensure that turbine engines can operate at higher temperatures without damaging the turbine blades, increasing their efficiency and lifespan.

Coatings with lower thermal expansion mismatch with substrate can help manage thermal stresses induced by temperature fluctuations.

Thermal Barrier Coating Application Methods

Electron Beam Physical Vapor Deposition (EBPVD)

Linde is adept at fabricating thermal barrier coatings (TBCs) that exhibit superior durability and thermal shock resistance, which are vital for turbine engines, using EBPVD (Electron Beam Physical Vapor Deposition) technology.

This method precisely deposits yttria-stabilized zirconia (YSZ), the predominant material for TBCs, known for its exceptional thermal insulation capabilities and resilience in high-temperature corrosive environments. The resulting fine columnar microstructures, which optimally orient in a <100> direction perpendicular to the substrate, significantly enhance the coatings' mechanical and thermal performance.

Adjusting EBPVD process parameters, including substrate temperature, deposition rate, and chamber pressure, allows for meticulous control over the microstructure and porosity, thereby tuning the thermal conductivity and durability of the TBCs. Moreover, advancements such as dual electron beam deposition further refine these microstructures, boosting the longevity of TBCs under thermal cycling conditions.

Related: What is Physical Vapor Deposition (PVD)?

Air Plasma Spray (APS) Technology

Air Plasma Spray (APS) technology heats gases to extreme temperatures, creating plasma — an ultra-hot, electrically charged gas that can bond thermal barrier coating materials to surfaces with extraordinary precision and strength. This method can be used to spray both metallic and ceramic coatings. The high melting point of the sprayed material allows for operation at high temperatures, making it a viable solution across many high-temperature applications.

Suspension Plasma Spray (SPS) Technology

SPS utilizes a liquid suspension of fine ceramic particles as feedstock, enabling the deposition of coatings with unique microstructures, such as columnar or porous structures, that are difficult to achieve with conventional air plasma spray. These microstructures contribute to improved properties like higher strain tolerance, better thermal shock resistance, and potentially longer lifetimes compared to traditional TBCs. 

Industries

Thermal barrier coatings feature across diverse industries, providing invaluable heat protection capabilities for various high-temperature components.

Aerospace Engine Components and Turbine Protection

TBCs play an integral role in protecting the vital components of gas turbine engines found in aircraft. By effectively managing the excessive heat generated, these coatings ensure that turbine blades and other high-temperature components operate optimally even under extreme conditions. This prolongs component lifespan and reduces the need for recurrent maintenance.

Power Generation and Energy Sector Applications

In the power generation industry, TBCs are extensively used to ensure the efficiency and safety of high-temperature operations. Their application on turbine blades and other components helps mitigate the risks of high-temperature operations, ultimately promoting sustainable and more efficient power generation.

Automotive and Advanced Manufacturing Solutions

In the automotive sector, TBCs help manage high-temperature conditions within the engine, ensuring more efficient performance and extending the duration between maintenance intervals. In advanced manufacturing scenarios, such as additive manufacturing processes, TBCs help manage and maintain optimal temperatures, protecting the equipment and ensuring superior output.

Linde's Thermal Barrier Coating Solutions

Linde AMT specializes in efficiency-boosting solutions with state-of-the-art thermal barrier coatings. Based on superior ceramic materials, our TBC offers excellent thermal insulation properties and low thermal conductivity.

Our ceramic-based thermal barrier coatings are especially designed for high-temperature applications in gas turbine engines, providing increased resistance against thermal cycling and thermal stresses.

These coatings have a high melting point, which ensures durability and longevity in extreme conditions. We employ an air plasma spray technique to apply our TBC, producing thermal barrier coatings with high thermal shock resistance. The outcome is a superior performance at elevated temperatures. Exhaust heat management and phase stability at high temperatures are additional benefits these coatings provide.

Coating Services

When finding the best solution, we first choose the optimal process for your part’s geometry and material composition, considering the challenges of thermal stress and the operating temperature range. We then select a coating material that meets your specifications and exhibits low thermal conductivity, thermal shock resistance, and oxidation resistance tailored for high-temperature turbine engines, combustion chambers, and other components.

Our tailored solutions aim to maximize thermal efficiency, reduce NOx emissions, and ensure optimal mechanical properties and chemical stability under your specific operating conditions. Our thermal barrier coatings include:

• Aluminide and Platinum Aluminide- Bond coat for enhanced oxidation and corrosion resistance for prolonged component life
• MCrAlY - Bond coat for enhanced oxidation and corrosion resistance for prolonged component life
• EBPVD Thermal Barrier Coatings (TBCs) - Low weight and high strain tolerance for advanced turbine blades and vanes in gas turbine engines
• High-temperature abradable coatings - Excellent thermal insulation properties in high-temperature environments with gas path sealing
• Low-density TBCs - Superior thermal insulation for lower temperature applications
• ZIRCOAT™ - Exceptional thermal insulation, strain tolerance, and erosion resistance for turbine engine components

Materials

Our ceramic materials, particularly the plasma-sprayed rare-earth zirconates, are distinguished in the industry for their low thermal conductivity (low-k) and high-temperature stability. These materials, including gadolinium zirconate (GZO) and yttrium zirconate (Y2Zr2O7) with phase stability up to 2600°C, are innovatively used as topcoats in thermal barrier coatings (TBCs), enhancing the performance of turbine blades in power generation sectors.

The unique microstructures developed through the plasma spray process, featuring porosity and vertical cracks, notably improve thermal insulation performance. The effectiveness and durability of these coatings are finely tuned by adjusting plasma spray parameters such as power, distance, and powder feed rate, catering to demanding applications like solid oxide fuel cells (SOFCs) where chemical stability and ionic conductivity at high temperatures are crucial.

FAQs

What are the specific advantages of your Thermal Barrier Coatings (TBCs)?
Our TBC solutions offer enhanced protection against high temperatures and thermal stresses. They also display superior oxidation and corrosion resistance, ensuring the longevity and durability of parts and components in manufacturing, aerospace, automotive, and energy sectors.

How does the thermal conductivity of your coatings contribute to performance enhancement?
Our coatings have low thermal conductivity, which ensures effective insulation, minimizes thermal energy transfer and ensures superior component performance at higher temperatures.

What is the significance of a higher thermal expansion coefficient in your materials?
Our ceramic materials' higher thermal expansion coefficient leads to greater compatibility with metallic layers and reduces thermal stresses. It also improves the coating's overall thermal resistance, contributing to component longevity and reliability.

Which industries primarily benefit from your TBC solutions?
Our TBC solutions are extensively used in manufacturing, aerospace, automotive, and energy sectors. They are particularly valuable in improving the efficiency and durability of gas turbine engines.