Gas Turbine Coating Diffusion Barrier for Crack Prevention

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Solution Overview

Problem

Gas turbine engine components experience fatigue failure due to diffusion bonding of abrasive coatings at high temperatures, leading to crack propagation and reduced functional lifespan.

Innovation Solution

A protective coating with an inner diffusion barrier layer, composed of elements like platinum, palladium, tantalum, tungsten, or hafnium, prevents diffusion bonding by limiting mutual solubility and element transfer, thereby inhibiting crack propagation into the component.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an abrasive coating is applied to seal fins to reduce clearance and improve sealing, then sealing performance is improved, but diffusion bonding occurs at high temperatures leading to crack propagation and reduced component lifespan

Engineering Contradiction:

Improvesealing performanceVSAvoidcomponent lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

A nickel separation layer is introduced as an intermediary between the abrasive coating and the seal fin body. This separation layer acts as a diffusion barrier that prevents direct diffusion bonding between the coating and the nickel-based superalloy substrate, thereby stopping crack propagation while maintaining the sealing function of the abrasive particles.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The coating system is designed as a composite structure with multiple layers: an entrapment layer of nickel, a separation layer of nickel, and an infill material containing hard cubic boron nitride particles. This composite structure provides both the abrasive sealing function and the diffusion barrier function simultaneously.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the clearance between seal fin and runner surface is reduced to improve sealing, then sealing performance is improved, but stress concentration increases leading to crack initiation

Engineering Contradiction:

Improvesealing performanceVSAvoidcoating strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The coating is designed with different local functions: the entrapment layer provides mechanical support and particle anchoring, the separation layer provides diffusion barrier functionality, and the infill contains the abrasive particles. This local differentiation allows the coating to maintain strength while providing sealing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The nickel separation layer is positioned beforehand to cushion and deflect cracks before they can propagate into the component body. This pre-positioned protective layer absorbs stress concentrations that would otherwise lead to crack initiation and propagation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If hard particles are embedded in the coating to provide abrasive sealing, then sealing performance is improved, but regions of high stress concentration are created adjacent to particle points

Engineering Contradiction:

Improvesealing performanceVSAvoidstress concentration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The nickel separation layer acts as an intermediary between the hard particles and the component body, absorbing and distributing the stress concentrations created by the embedded particles. This mediator layer prevents stress concentration from reaching critical levels that would cause crack initiation.

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 diffusion barrier layer increases the component's functional lifespan by preventing diffusion bonding and crack propagation, while also facilitating coating removal during repair and overhaul.

Implementation Method 1

an inner diffusion barrier layer including any one or any combination of elements selected from the group consisting of platinum, palladium, tantalum, tungsten, hafnium and iridium

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

The diffusion barrier layer may reduce or prevent diffusion bonding of the outer layer to the component by providing a limited mutual solubility between itself and one or more elements for immobilisation

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 3

the boron nitride particles abrade the softer material of the runner surface such that the seal fin forms a groove in the runner surface

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentUS10934860B2Gas turbine engine component with protective coating

Publication Date: 2021.03.02 ROLLS ROYCE PLC

AI summary

A gas turbine engine component made of a nickel-based superalloy, the gas turbine engine component comprising a protective coating. The protective coating includes an inner diffusion barrier layer including any one or any combination of elements selected from the group consisting of platinum, palladium, tantalum, tungsten, hafnium and iridium, and an outer layer of hard material formed of hard particles embedded in a matrix.