MAX Phase Protective Coating for Thermal Barrier CMAS Resistance

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Solution Overview

Problem

High-pressure turbines face degradation due to infiltration of molten CMAS, which weakens thermal barrier systems and reduces their operational lifespan, as existing anti-CMAS materials lack mechanical toughness and are prone to flaking and erosion.

Innovation Solution

A protective coating comprising MAX phases, such as (ZrxTi1-x)2AlC or (CrxTi1-x)2AlC, with a second region of Ti2AlC, forms a dense alumina layer that prevents CMAS infiltration and enhances chemical compatibility and mechanical toughness, accommodating thermal expansion differences and improving resistance to erosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If rare earth zirconate based ceramic layers are used as anti-CMAS coating, then chemical resistance to CMAS is improved, but mechanical toughness deteriorates leading to progressive flaking and erosion

Engineering Contradiction:

Improvechemical resistance to CMASVSAvoidmechanical toughness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent uses a composite coating structure combining a metallic substrate, thermal barrier coating, and protective MAX phase coating. The MAX phase coating itself has a layered structure (Mn+1AXn phases) that combines ceramic-like chemical stability with metallic-like toughness and ductility, resolving the contradiction between chemical resistance and mechanical strength

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the material parameters by using MAX phases with specific stoichiometry (n=2 or 3) and composition ratios (x values), where the layered structure and bonding characteristics provide both chemical inertness to CMAS and mechanical toughness through strong in-plane bonding and weak out-of-plane van der Waals forces

Inventive Principle:

Principle #35Parameter changes

2Reliability

If CMAS reacts with anti-CMAS material to form sealed barrier layer, then protection against CMAS infiltration is improved, but mechanical strength deteriorates due to penetration depth requirements

Engineering Contradiction:

Improveprotection against CMAS infiltrationVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The MAX phase coating is applied in advance as a protective layer before CMAS exposure. The coating is designed to react with CMAS at its surface to form a sealed barrier layer, preventing deeper infiltration while maintaining the underlying coating's mechanical integrity through its inherently tough layered structure

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful CMAS infiltration into a beneficial surface reaction. The CMAS reacts with the MAX phase at the coating surface to form a protective sealed barrier layer (calcium aluminosilicate phases), transforming the harmful molten infiltration into a protective surface layer that prevents further damage

Inventive Principle:

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

3Productivity

If thermal barrier is subjected to higher temperatures to improve turbine efficiency, then productivity is improved, but durability deteriorates due to oxidation and corrosion

Engineering Contradiction:

Improveturbine efficiencyVSAvoiddurability against oxidation and corrosion

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The MAX phase coating acts as a sacrificial protective layer that can oxidize and form protective scales at high temperatures. This outer layer protects the underlying expensive thermal barrier and metallic substrate from direct exposure to oxidizing environments, allowing the system to operate at higher temperatures for improved efficiency while the coating absorbs the environmental attack

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 MAX phase-based protective coating significantly extends the lifespan of thermal barriers by preventing CMAS infiltration, enhancing resistance to oxidation, corrosion, and thermal cycling, and improving mechanical durability.

Implementation Method 1

A protective coating comprising MAX phases, such as (ZrxTi1-x)2AlC or (CrxTi1-x)2AlC, with a second region of Ti2AlC, forms a dense alumina layer that prevents CMAS infiltration

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

accommodating thermal expansion differences and improving resistance to erosion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12195857B2Coated part comprising a protective coating based on MAX phases

Publication Date: 2025.01.14 SAFRAN SA

AI summary

A coated part includes a metallic substrate, a thermal barrier comprising a ceramic material and covering the metallic substrate, wherein the coated part further includes a protective coating covering the thermal barrier, the protective coating including, in a first region, a first MAX phase, denoted PZ2, of formula (ZrxTi1-x)2AlC or a first MAX phase, denoted PC2, of formula (CrxTi1-x)2AlC with x non-zero and less than or equal to 1 in the MAX phases PZ2 and PC2, and the protective coating includes, in a second region covering the first region, a second MAX phase of formula Ti2AlC.