Cast Component Surface Preparation for HAZ Crack-Free DED Repair
Find Innovative SolutionsGenerate Solutions
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 repair zone of cast components 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 to prevent microcracking in the HAZ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If welding techniques are used to repair cast superalloy components, then repair operations-related wear and damage can be addressed, but microcracking in the heat affected zone is created leading to component failure
Solution Approach 1:
The patent applies preliminary surface preparation operations (shot peening, laser shock peening, or grinding) to the repair zone before directed energy deposition repair. This preliminary action imparts compressive residual stress to the substrate surface, creating a beneficial stress state that prevents microcrack formation during the subsequent welding repair process, thereby resolving the contradiction between repair capability and component reliability
Solution Approach 2:
The patent introduces compressive residual stress through surface preparation operations as a preliminary anti-action that counteracts the tensile stresses and microcracking that would normally occur in the heat affected zone during welding repair. This pre-applied compressive stress acts as a protective measure that prevents the harmful microcracking phenomenon, enabling reliable repair of cast superalloy components
2Productivity
If directed energy deposition repair is performed without surface preparation, then repair operation can proceed directly, but microcracks form in the heat affected zone adjacent to the repair zone
Solution Approach 1:
The patent introduces a preliminary surface preparation step that imparts compressive residual stress to the repair zone before directed energy deposition. This preliminary action modifies the substrate's stress state and microstructure, creating conditions that prevent microcrack formation during the repair process, thereby achieving both efficient repair and precise control over microcrack formation
Solution Approach 2:
The patent changes the physical and mechanical parameters of the substrate surface through surface preparation operations (shot peening, laser shock peening, or grinding). These parameter changes include imparting compressive residual stress and modifying surface microstructure, which fundamentally alter the substrate's response to thermal cycling during repair, preventing microcrack formation in the heat affected zone while maintaining repair efficiency
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 inhibits the formation and propagation of microcracks in the HAZ, resulting in a more robust interface and reducing the risk of component failure during service.
Implementation Method 1
A surface preparation operation is performed on the repair zone to impart a pre-selected level of compressive residual stress
Implementation Method 2
forms a fine recrystallized grain structure at the interface to prevent microcracking in the HAZ
Implementation Method 3
The directed energy deposition repair operation includes formation of a directed energy deposition deposit on the cast substrate
Data Source
AI summary
A method of weld repairing a cast component includes identifying a repair zone on the cast component. The repair zone represents a region of a cast substrate of the cast component 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 adjacent to the repair zone. The directed energy deposition repair operation includes formation of a directed energy deposition deposit on the cast substrate.