Braze Joint Cooling Control to Prevent Porosity and Hot Cracking
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Solution Overview
Problem
Conventional braze processes for metal alloys, such as those used in rotary machines, often result in solidification defects like porosity and hot cracking due to differential cooling and solidification shrinkage, which reduce the tensile strength and creep life of braze joints, leading to increased wear and potential component failure.
Innovation Solution
A system and method for creating braze joints that involves a component with a recess and a cap of braze material, where a thermal insulation layer is applied to the exposed braze surface and heat is extracted from a location closer to the inner edge of the recess than the cap, controlling the cooling process to minimize solidification defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional braze processes are used to repair cracks or defects in metal alloys, then the defect can be filled and the component can be salvaged, but solidification defects such as porosity and hot cracking occur due to differential cooling and solidification shrinkage, reducing tensile strength and creep life
Solution Approach 1:
The patent applies different cooling rates to different regions of the braze joint. The surface region is cooled faster than the interior region, creating a controlled temperature gradient. This local differentiation in cooling behavior prevents solidification defects by ensuring the surface solidifies first, supporting the interior as it solidifies, thereby eliminating porosity and hot cracking while maintaining braze joint integrity
Solution Approach 2:
The patent employs a multi-stage cooling process with distinct phases: initial rapid cooling of the surface, followed by controlled cooling of the interior. This periodic application of different cooling rates allows the braze material to solidify in a controlled sequence, preventing defect formation while ensuring complete solidification, thus improving both reliability and manufacturing precision
2Device complexity
If the braze material cools uniformly, then the cooling process is simple, but the braze material closer to the surface cools faster than the braze material deeper into the defect, inducing solidification defects
Solution Approach 1:
The patent implements non-uniform cooling by applying cooling conditions differently to surface and interior regions. The surface receives faster cooling while the interior receives slower cooling, creating a controlled temperature gradient. This local quality differentiation resolves the contradiction by preventing solidification defects through strategic cooling rate variation, achieving defect-free braze joints without excessive complexity
Solution Approach 2:
The patent changes the cooling rate parameter spatially and temporally during the cooling process. By varying the cooling rate from fast at the surface to slow in the interior, and adjusting these rates during different stages of solidification, the patent prevents solidification defects while maintaining a manageable cooling process, thus improving reliability without proportionally increasing device complexity
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 approach reduces or eliminates solidification defects in the braze joint, enhancing its tensile strength and creep life, thereby extending the component's lifespan and reliability, especially in high-stress environments like the hot flow path of rotary engines.
Implementation Method 1
an insulation layer that at least partially covers the exposed braze surface
Implementation Method 2
heat is extracted from a location closer to the inner edge of the recess than to the cap
Implementation Method 3
as the braze material begins to cool after the braze material has filled the defect in the component, solidification shrinkage occurs within the joint
Data Source
AI summary
A system for creating a braze joint within a component. The system includes an environment operable to reach a braze temperature sufficient to melt at least a portion of a braze material. The system also includes a component within the environment, the component including a base having a base surface, a recess depending from the base surface into the base to an inner edge, and a braze material within the recess and forming a cap above the base surface. The braze material fills the recess from the cap to the inner edge. The cap has an exposed braze surface. The system also includes an insulation layer that at least partially covers the exposed braze surface.