CMAS-Resistant Thermal Barrier Coating for Gas Turbines

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Solution Overview

Problem

High-temperature gas turbine engines face damage from calcia-magnesia-alumina-silicate (CMAS) deposits, which infiltrate porous thermal barrier coatings (TBCs), increasing thermal conductivity and reducing their effectiveness and lifespan.

Innovation Solution

A CMAS-resistant TBC layer is developed, comprising a combination of TBC compositions like yttria-stabilized zirconia and CMAS-resistant compositions such as alumina and rare earth oxides, which react with CMAS to form a solid or highly viscous reaction product, preventing infiltration and maintaining thermal insulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a porous TBC structure is used to reduce thermal conductivity and improve strain tolerance, then thermal insulation performance is improved, but resistance to CMAS infiltration deteriorates

Engineering Contradiction:

Improvethermal conductivityVSAvoidCMAS resistance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies local quality by creating a TBC structure with different porosity levels in different regions. The bulk TBC maintains high porosity for thermal insulation, while the surface region has reduced porosity or contains CMAS-resistant materials to prevent infiltration. This spatial variation in properties resolves the contradiction between thermal insulation and CMAS resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining YSZ with CMAS-resistant materials such as alumina, silica, or rare earth oxides in the surface region. This composite structure provides both the thermal insulation properties of porous YSZ and the CMAS resistance of the added materials, resolving the contradiction between these two requirements.

Inventive Principle:

Principle #40Composite materials

2Power

If turbine inlet temperature is increased to improve efficiency, then energy output is improved, but TBC stability at high temperature deteriorates

Engineering Contradiction:

Improveenergy outputVSAvoidTBC stability

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition parameters of the TBC by incorporating CMAS-resistant materials with high melting points and stable crystal structures. This compositional modification enables the TBC to maintain stability at higher operating temperatures, allowing increased turbine inlet temperatures for improved efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potentially harmful interaction between CMAS and TBC into a beneficial outcome by designing a TBC that reacts with CMAS to form a stable, protective reaction layer. This reaction layer, rather than degrading the TBC, actually enhances its resistance to CMAS infiltration and improves overall stability at high temperatures.

Inventive Principle:

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

3Loss of energy

If YSZ TBC is used to provide thermal insulation, then thermal conductivity is reduced, but resistance to CMAS infiltration deteriorates

Engineering Contradiction:

Improvethermal conductivityVSAvoidCMAS infiltration

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent introduces CMAS-resistant materials as an intermediary layer or component within the TBC structure. This intermediary prevents direct contact and harmful interaction between CMAS and the porous YSZ, while maintaining the thermal insulation function. The intermediary reacts with CMAS to form a protective barrier, preserving the underlying YSZ structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

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-resistant TBC layer enhances the durability and thermal insulation of high-temperature components by preventing CMAS infiltration and reducing thermal conductivity, thus extending the lifespan and improving the performance of gas turbine engine components.

Implementation Method 1

a CMAS-resistant TBC layer... which react with CMAS to form a solid or highly viscous reaction product

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

The thermal barrier coating may include a thermally insulative ceramic topcoat... low thermal conductivity

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentUS9194242B2Thermal barrier coatings including CMAS-resistant thermal barrier coating layers

Publication Date: 2015.11.24 ROLLS ROYCE CORP

AI summary

An article may include a superalloy substrate and a calcia-magnesia-alumina-silicate (CMAS)-resistant thermal barrier coating (TBC) layer overlying the superalloy substrate. In some embodiments, the CMAS-resistant TBC layer includes between about 50 wt. % and about 90 wt. % of a TBC composition and between about 10 wt. % and about 50 wt. % of a CMAS-resistant composition. In some examples, the TBC composition includes at least one of yttria-stabilized zirconia, yttria-stabilized hafnia, zirconia stabilized with at least three rare earth oxides, or hafnia stabilized with at least three rare earth oxides. In some examples, the CMAS-resistant composition includes alumina, silica, and an oxide of at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, or Lu.