Cast Component Surface Preparation for Crack-Free DED Repair
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Solution Overview
Problem
Welding techniques for repairing cast superalloy components often create a heat affected zone (HAZ) with microcracking, which can lead to component failure due to high stresses and liquation cracking during the repair process.
Innovation Solution
A surface preparation operation is performed on the cast component to impart a pre-selected level of compressive residual stress, followed by a directed energy deposition repair, which forms a fine recrystallized grain structure at the interface, preventing microcrack formation in the HAZ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If welding techniques are used to repair cast superalloy components, then the component can be restored and reused, but microcracking occurs in the heat affected zone leading to potential component failure
Solution Approach 1:
The patent applies preliminary surface preparation operations (shot peening, laser shock peening, or grit blasting) to the cast component surface before directed energy deposition repair. This preliminary action imparts compressive residual stress to the surface, creating a protective state that prevents microcrack formation during the subsequent welding repair process, thereby resolving the contradiction between enabling repair and preventing failure
Solution Approach 2:
The patent introduces compressive residual stress through surface preparation as a preliminary anti-action that counteracts the tensile stresses and microcracking tendency that will occur during the welding process. This pre-applied compressive stress acts as a protective measure against the harmful effects of the repair operation itself
2Manufacturing precision
If directed energy deposition is performed on the repair zone, then material is deposited to restore the component, but microcracks form in the adjacent heat affected zone
Solution Approach 1:
The surface preparation operation is performed as a preliminary action before directed energy deposition to modify the surface state. This preliminary treatment creates compressive residual stress that remains present during the DED process, preventing the thermal stresses from causing microcracks in the heat affected zone while allowing precise material deposition
Solution Approach 2:
The patent changes the physical state and stress parameters of the substrate surface through surface preparation treatments. By transforming the surface from a stress-free or tensile-stressed state to a compressively-stressed state, the material properties in the heat affected zone are modified to resist crack formation during the thermal cycling of DED
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 prevents microcracking in the HAZ, resulting in a more robust interface and limiting crack propagation, ensuring the integrity of the repaired cast component.
Implementation Method 1
A surface preparation operation is performed on the repair zone to impart a pre-selected level of compressive residual stress to the repair zone
Implementation Method 2
which forms a fine recrystallized grain structure at the interface
Implementation Method 3
The directed energy deposition repair operation is performed on the repair zone
Data Source
Figure 1~2
AI summary
A method of weld repairing a cast component (22) includes identifying a repair zone on the cast component (22). The repair zone represents a region of a cast substrate (24) of the cast component (22) requiring a directed energy deposition repair operation. A surface preparation operation is performed on the repair zone before performing the directed energy deposition repair operation. The surface preparation operation imparts a pre-selected level of compressive residual stress to the repair zone. The directed energy deposition repair operation is performed on the repair zone without formation of microcracks in a heat affected zone (10) adjacent to the repair zone. The directed energy deposition repair operation includes formation of a directed energy deposition deposit on the cast substrate (24).