Local Two-Layer Thermal Barrier Coating for Turbine Blades
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Solution Overview
Problem
Turbine blades experience local temperature peaks due to greater thermal stresses, leading to consumption or spalling of metallic protective layers and ceramic thermal barrier coatings, which reduces turbine efficiency and operational lifespan.
Innovation Solution
A two-layer thermal barrier coating system is applied locally in highly stressed regions, featuring a zirconium-based first layer and a porous, fully stabilized pyrochlore-based local reinforcement layer, such as gadolinium zirconate, to enhance thermal resistance without increasing the overall material thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If cooling air holes are used to reduce thermal stress, then thermal stress is reduced, but compressor air consumption increases and efficiency decreases
Solution Approach 1:
The patent applies a local two-layer coating structure specifically in highly stressed regions rather than uniformly across the entire component. The first layer (base TBC) provides general thermal protection, while the second layer (reinforcement layer with different thermal expansion coefficient) is applied locally to counteract thermal stress in critical areas, eliminating the need for cooling air holes.
2Reliability
If thermal barrier coating thickness is increased to protect against thermal stress, then thermal protection is improved, but material consumption increases and coating system becomes more complex
Solution Approach 1:
Instead of uniformly increasing coating thickness across the entire component, the patent applies a local two-layer structure only in highly stressed regions. The first layer provides base thermal protection, while the second layer with different thermal expansion properties is applied locally to enhance stress resistance, maintaining overall system simplicity while providing targeted protection.
Solution Approach 2:
The patent employs a composite coating system consisting of two distinct ceramic layers with different thermal expansion coefficients. The first layer (e.g., stabilized zirconia) provides base thermal barrier function, while the second layer (e.g., pyrochlore structure material) is applied locally to compensate for thermal stress, creating a composite structure that optimizes both protection and stress resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coating system effectively manages increased thermal stresses, reducing the risk of spalling and extending turbine operational lifespan by distributing thermal loads more efficiently without consuming compressor air.
Implementation Method 1
a porous, fully stabilized pyrochlore-based local reinforcement layer, such as gadolinium zirconate, to enhance thermal resistance
Data Source
AI summary
A turbine blade with a ceramic thermal barrier coating system has a substrate designed as a blade platform and as a blade airfoil. On the substrate is a first ceramic layer as a thermal barrier coating, which protects the substrate in the exposed high temperature region and there is locally an increase of the thermal barrier coating for locally reinforcing the thermal barrier. The increase includes a material that is different from the material of the first ceramic layer. The local reinforcement is arranged over the first ceramic layer, without the first ceramic layer having a reduced layer thickness. The local reinforcement is provided at most on 30% of the area of the blade airfoil and is arranged close to a platform extending over the entire pressure side in the direction of flow and with an extent thereto in the radial direction of the blade airfoil is at most 30%.