CMAS-Reactive Thermal Barrier Coating for Gas Turbines

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Solution Overview

Problem

Conventional thermal barrier coatings (TBCs) in gas turbine engines are susceptible to degradation by calcium-magnesium-alumino-silicate (CMAS) contaminants at elevated temperatures, leading to reduced strain tolerance and spallation, as the molten CMAS infiltrates the porous TBC, compromising its mechanical stability.

Innovation Solution

A CMAS-reactive thermal barrier coating system comprising a ceramic coating with a CMAS-reactive overlay that forms a stable high melting point crystalline precipitate when reacted with molten CMAS, reducing infiltration kinetics, and includes a concentrated rare earth overlay to enhance the reaction rate and maintain strain tolerance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional porous TBC is used to protect substrate, then strain tolerance is improved, but CMAS infiltration resistance deteriorates

Engineering Contradiction:

Improvestrain toleranceVSAvoidCMAS infiltration

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The coating is segmented into two distinct functional layers: a porous ceramic coating layer that provides strain tolerance, and a dense CMAS-reactive overlay layer that blocks CMAS infiltration. This segmentation allows each layer to optimize its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining porous ceramic material (for strain tolerance) with a dense CMAS-reactive overlay material (for infiltration resistance). The composite nature allows simultaneous achievement of both strain tolerance and CMAS resistance through complementary material properties.

Inventive Principle:

Principle #40Composite materials

2Power

If operating temperature is increased to improve engine efficiency, then power output is improved, but TBC durability deteriorates

Engineering Contradiction:

Improveengine efficiencyVSAvoidTBC durability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The CMAS-reactive overlay layer provides preliminary protection by reacting with and blocking CMAS contaminants before they can infiltrate the porous ceramic coating. This preemptive action prevents the degradation that would otherwise occur at elevated operating temperatures, thereby maintaining TBC durability.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The invention converts the harmful effect of CMAS infiltration into a beneficial protective mechanism. The CMAS-reactive overlay deliberately reacts with CMAS to form a protective barrier, transforming the previously harmful infiltration process into a beneficial self-protecting mechanism that enhances coating durability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-affected harmful factors

If dense overlay is applied to block CMAS infiltration, then CMAS resistance is improved, but strain tolerance deteriorates

Engineering Contradiction:

ImproveCMAS infiltration resistanceVSAvoidstrain tolerance

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the coating have different properties optimized for their specific functions: the ceramic coating layer has high porosity for strain tolerance, while the overlay layer has low porosity for CMAS blocking. Each layer's local quality is tailored to its specific protective role.

Inventive Principle:

Principle #3Local quality

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 CMAS-reactive overlay coating effectively suppresses further CMAS ingress by forming a high melting point crystalline precipitate at a rate competitive with CMAS infiltration kinetics, maintaining the strain tolerance of the TBC and extending its durability at higher temperatures.

Implementation Method 1

comprises a compound that forms a stable high melting point crystalline precipitate when reacted with molten CMAS

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 2

forms a stable high melting point crystalline precipitate when reacted with molten CMAS

Methodology Applied

Scientific EffectPrecipitation: Precipitation

Implementation Method 3

At elevated temperatures, CMAS can melt and infiltrate the porous TBC

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS12196109B2Reactive thermal barrier coating

Publication Date: 2025.01.14 RTX CORP

AI summary

A calcium-magnesium-alumino-silicate (CMAS)-reactive thermal barrier coating includes a ceramic coating and a CMAS-reactive overlay coating, wherein the CMAS-reactive overlay coating conforms to a surface of the ceramic coating and comprises a compound that forms a stable high melting point crystalline precipitate when reacted with molten CMAS at a rate that is competitive with CMAS infiltration kinetics into the thermal barrier coating. The ceramic coating phase is stable with the CMAS-reactive overlay coating.