Borescope-Guided Braze Plug Repair for EDM Backwall Strikes

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Solution Overview

Problem

Electrical discharge machining (EDM) in gas turbine engines often results in backwall strikes due to the formation of recast layers, leading to extended holes and stress concentrations in hot gas path components, which can compromise the structural integrity and efficiency of the engine.

Innovation Solution

A repair process involving the identification of backwall strikes using borescopes or CT scans, followed by the insertion of a custom-made repair rod with a crimped plug, and deposition of braze paste to fill and solidify the void, effectively addressing the structural issues caused by EDM.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If EDM is used to form cooling holes in hot gas path components, then cooling passages can be created, but backwall strike occurs causing extended holes and stress concentrations

Engineering Contradiction:

Improvecooling hole formationVSAvoidhole depth control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by first identifying the backwall strike void using a borescope or CT scan, then determining its physical configuration before inserting the repair rod. This preliminary assessment allows for proper sizing and shaping of the repair rod to match the void, ensuring precise repair without creating additional manufacturing issues.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The repair rod serves as an intermediary element between the backwall strike void and the final braze repair. The rod is inserted into the void, and braze material is deposited over it, creating a multi-stage repair process that ensures proper filling and structural restoration of the damaged area.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If EDM drilling is extended to compensate for recast layer formation, then hole configuration is improved, but backwall strike occurs in internal cooling passages

Engineering Contradiction:

Improvehole configurationVSAvoidbackwall strike damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful backwall strike damage into a benefit by using the void created by the strike as a target for repair. The repair rod is specifically sized to fit the backwall strike void, and braze material is deposited to restore the structural integrity, effectively transforming the damaged area into a reinforced repair zone.

Inventive Principle:

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

Solution Approach 2:

The patent applies parameter changes by modifying the physical state of the repair materials through heating. The braze paste is heated to melt and flow into the void, then cooled to solidify and form a strong repair. This phase change ensures proper filling and bonding of the repair materials to the surrounding component structure.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If backwall strike is repaired using braze paste, then structural integrity is restored, but the repair process complexity increases

Engineering Contradiction:

Improvestructural integrityVSAvoidrepair process steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the repair process into distinct sequential steps: identification of the void, determination of its configuration, insertion of the repair rod, and deposition of braze paste. This segmented approach ensures each step is properly executed and allows for quality control at each stage, ultimately ensuring reliable repair despite the increased process complexity.

Inventive Principle:

Principle #1Segmentation

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 repair process mitigates stress concentrations and maintains the structural integrity of hot gas path components, enhancing the engine's efficiency and longevity by preventing further damage from EDM-induced backwall strikes.

Implementation Method 1

inserting borescope into the component in order to view the void

Methodology Applied

Scientific EffectOptical detection: Reflection

Implementation Method 2

identifying a backwall strike formed by EDM of a hole in the hot gas path component

Methodology Applied

Scientific EffectX-ray imaging: X-Ray

Implementation Method 3

depositing braze paste over the repair plug in the void

Methodology Applied

Scientific EffectBrazing: Brazing

Data Source

PatentUS11524350B1Backwall strike braze repair

Publication Date: 2022.12.13 GE INFRASTRUCTURE TECH LLC

AI summary

A process of repairing a component includes identifying a void in a component; determining at least one approximate physical configuration of the void; inserting borescope into the component in order to view the void; providing a repair rod approximately equivalent to at least one of the least one approximate physical configuration of the void; inserting the repair rod into component; confirming insertion of the repair rod in the void; separating the repair rod to leave a repair plug in the void; and depositing braze paste over the repair plug in the void.