Repairing Directionally Solidified Substrates via Volumetric Heating

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Solution Overview

Problem

Existing methods for repairing directionally solidified or single crystal substrates, such as turbine engine components, face challenges in controlling heating, cooling, and time at temperature due to heat source movement and variable geometries, leading to difficulties in forming desired crystalline structures without high angle grain boundaries.

Innovation Solution

A repair method that involves heating the entire volume of additive material and adjacent areas to a fusion temperature, holding for grain growth and orientation, and then cooling at a controlled rate to propagate epitaxial crystalline structures, using a uniform heat source and maintaining an inert atmosphere to minimize high angle grain boundaries.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a moving heat source is used to weld repair material onto directionally solidified or single crystal substrates, then the repair can be performed on variable geometries, but high angle grain boundaries form and desired crystalline structure propagation is difficult

Engineering Contradiction:

Improveability to repair variable geometriesVSAvoidcrystalline structure propagation

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

Instead of moving the heat source across the substrate surface, the invention inverts the approach by heating the entire volume of additive material and adjacent substrate simultaneously to fusion temperature, then controlling uniform cooling. This eliminates the moving heat source problem that causes thermal cycling and high angle grain boundaries, while still enabling repair of variable geometries through volumetric heating and controlled solidification.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If heating rate and time at temperature are not controlled, then the repair process is simpler, but high angle grain boundaries form and epitaxial crystalline structure propagation fails

Engineering Contradiction:

Improvesimplicity of repair processVSAvoidgrain boundary control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention changes the thermal parameters by heating the entire volume to fusion temperature and holding for a controlled time to allow grain growth and orientation, then ramping down at a predetermined controlled rate. This parameter control enables epitaxial crystalline structure propagation while maintaining relative process simplicity through uniform volumetric heating rather than complex moving heat source control.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the heat source is stopped and started during the repair process, then the repair can be performed in segments, but the thermal cycle is aggravated and crystalline structure control is lost

Engineering Contradiction:

Improveability to perform segmented repairVSAvoidthermal cycle stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention applies preliminary action by heating the entire volume of additive material and adjacent substrate to fusion temperature before any cooling occurs, and maintaining this state for a controlled time to establish grain growth and orientation. This preliminary heating and holding phase establishes the thermal conditions necessary for epitaxial crystalline structure propagation before the cooling and solidification process begins, avoiding the problems of starting and stopping heat source motion.

Inventive Principle:

Principle #10Preliminary action

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

This method effectively creates favorable thermal profiles for directionally solidified and single crystal structures, allowing their continuation into the repair material, while being cost-effective compared to other techniques like laser or plasma deposition.

Implementation Method 1

utilizing a heat source to heat an entire volume of the additive material and an area adjacent to the additive material to a fusion temperature

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

heat an entire volume of the additive material and an area adjacent to the additive material to a fusion temperature

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 3

ramping down the heat source at a predetermined controlled rate until solidification is complete

Methodology Applied

Scientific EffectSolidification: Freezing

Implementation Method 4

holding at the fusion temperature for a time sufficient to allow grain growth and orientation to occur

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 5

allow grain growth and orientation to occur

Methodology Applied

Scientific EffectCrystallisation: Crystallisation

Data Source

PatentUS7784668B2Repair method for propagating epitaxial crystalline structures by heating to within 0-100° f of the solidus

Publication Date: 2010.08.31 RTX CORP

AI summary

A repair method of propagating epitaxial crystalline structures is provided. The repair method broadly comprises the steps of providing a substrate to be repaired, placing an additive material as a preformed shape onto an area of the substrate to be repaired, utilizing a heat source to heat an entire volume of the additive material and an area adjacent to the additive material to within 0-100° F. of their solidus temperatures, holding at the fusion temperature for a time sufficient to allow grain growth and orientation to occur, and ramping down the heat source at a predetermined controlled rate until solidification is complete.