Ceramic Topcoat Segmentation Cracking for Gas Turbine Coating

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Solution Overview

Problem

Conventional abradable ceramic coatings in gas turbine engines are vulnerable to erosion and spalling due to elevated temperatures causing sintering and internal stresses, leading to delamination and reduced efficiency.

Innovation Solution

A method of manufacturing ceramic topcoats with controlled sintering and air impingement cooling to induce segmentation cracking, allowing for tailored crack spacing, depth, and number per unit surface area, reducing internal stresses and enhancing mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional thermal spray processes are used to form coatings with stress relief cracks, then spalling and delamination resistance is improved, but the coating mechanical properties (hardness, density, porosity) and abrasion characteristics deteriorate

Engineering Contradiction:

Improvespalling and delamination resistanceVSAvoidcoating mechanical properties and abrasion characteristics

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The coating is segmented into multiple layers with different functions: a dense, hard topcoat layer for abrasion resistance and a separate stress relief layer with controlled cracks for spalling resistance. This segmentation allows each layer to optimize its properties independently without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the coating have different properties: the topcoat layer has high hardness and low porosity for abrasion resistance, while the stress relief layer has controlled crack patterns for stress management. This local differentiation resolves the contradiction by assigning different quality requirements to different functional zones.

Inventive Principle:

Principle #3Local quality

2Reliability

If process parameters (nozzle travel speed, flame temperature) are controlled to induce stress relief cracks, then delamination resistance is improved, but coating density and hardness deteriorate

Engineering Contradiction:

Improvedelamination resistanceVSAvoidcoating hardness and density

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The stress relief cracks are pre-formed in a dedicated stress relief layer during the coating application process, before the topcoat is applied. This preliminary action ensures stress management capability is built in advance without compromising the subsequent topcoat quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A bond coat layer acts as an intermediary between the substrate and the topcoat, providing a transition zone that facilitates stress relief crack formation while protecting the topcoat from direct stress exposure. This intermediary layer allows the topcoat to maintain high hardness and density.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the ceramic coating is made thicker to improve erosion resistance, then durability is improved, but internal stresses from sintering increase, leading to more severe delamination

Engineering Contradiction:

Improveerosion resistanceVSAvoidinternal sintering stresses

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The thick coating is segmented into multiple layers: a thick topcoat for erosion resistance, an intermediate bond coat, and a stress relief layer with controlled cracks. This segmentation allows the total thickness to be maintained for erosion protection while distributing and managing internal stresses through the layered structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The thermal and mechanical properties are changed across different layers: the topcoat is designed for high erosion resistance, the bond coat for intermediate properties, and the stress relief layer for crack formation. This parameter differentiation allows thick coating application without proportional increase in delamination risk.

Inventive Principle:

Principle #35Parameter changes

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 method effectively reduces spalling and delamination, maintaining turbine efficiency by dissipating energy through pre-formed stress relief cracks, thereby improving the durability and abrasion resistance of the ceramic coatings.

Implementation Method 1

controlled sintering of at least a portion of the ceramic topcoat to induce segmentation cracking in the ceramic topcoat

Methodology Applied

Scientific EffectSintering: Sintering

Implementation Method 2

establish a predetermined thermal gradient through the ceramic topcoat to induce segmentation cracking

Methodology Applied

Scientific EffectThermal gradient: Temperature Gradient

Implementation Method 3

cooling the article by air impingement cooling

Methodology Applied

Scientific EffectImpingement cooling: Cooling

Data Source

PatentEP1985723B1Method for improved ceramic coating

Publication Date: 2015.03.25 UNITED TECH CORP

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AI summary

A method of manufacturing an article having a ceramic topcoat (50) includes the steps of forming the ceramic topcoat (50) on the article, heating the ceramic topcoat (50), and establishing a desired thermal gradient (82) through the ceramic topcoat (50) to induce segmentation cracking in the ceramic topcoat (50)