Porous Interlayer Bonding via Electrical Resistance Heating
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Solution Overview
Problem
Existing diffusion bonding methods face limitations in bond strength due to localized heat spikes from electrical arcing, leading to weakened bonds, especially when using symmetrical primitive geometry and powder metal interlayers with limited porosity.
Innovation Solution
A method involving a porous interlayer with 10-30% porosity, locally heated by electrical resistance to prevent arcing and promote mechanical interlocking, using additive manufacturing or power beam processing to create a textured surface for improved bonding between articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If electrical resistance heating is used to heat the articles and interlayer to the required temperature, then heating efficiency is improved, but electrical arcing between protrusions causes localized heat spikes that weaken the bond
Solution Approach 1:
The patent applies a porous interlayer with controlled porosity (10-30%) to eliminate electrical arcing during resistance heating. The porous structure provides multiple current paths through the interlayer, preventing concentration of current at surface protrusions that would cause arcing and localized heat spikes. This resolves the contradiction by maintaining heating efficiency while eliminating the reliability issue of bond weakness caused by arcing.
Solution Approach 2:
The patent changes the physical parameters of the interlayer by introducing controlled porosity and specific surface roughness characteristics. These parameter changes modify the electrical and thermal behavior of the interlayer, allowing it to conduct current uniformly without arcing while still enabling effective heat transfer for bonding, thus resolving the contradiction between heating efficiency and bond strength.
2Shape
If a powder metal interlayer is used to provide improved alignment, then alignment between articles is improved, but the interlayer has limited porosity resulting in limited bond strength
Solution Approach 1:
The patent optimizes the porosity parameter of the interlayer to a specific range (10-30%), which is higher than conventional dense interlayers but controlled to maintain structural integrity. This parameter change enables both improved alignment functionality and enhanced bond strength by allowing better diffusion bonding while maintaining geometric stability during the bonding process.
Solution Approach 2:
The patent creates a composite structure where the porous interlayer combines metallic phases with controlled void spaces. This composite architecture provides both the alignment function (through geometric configuration) and enhanced bond strength (through optimized porosity that facilitates diffusion bonding), resolving the contradiction between alignment capability and bond strength.
3Strength
If the interlayer porosity is increased to prevent arcing, then bond strength is improved, but excessive porosity may lead to voids in the bonded article
Solution Approach 1:
The patent precisely controls the porosity parameter within the optimal range of 10-30%, avoiding both excessive porosity (which would create voids) and insufficient porosity (which would cause arcing). This optimized parameter range ensures that the interlayer is sufficiently porous to prevent arcing and enhance bond strength, while maintaining enough material density to eliminate voids in the final bonded article.
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 achieves enhanced bonding strength and mechanical interlocking, preventing voids and thermal disruption, resulting in a stronger and more uniform bond without excessive material loss or imprecision.
Implementation Method 1
The step of locally heating the interlayer comprises electrical resistance heating of the interlayer by passing an electrical current through the interlayer region
Implementation Method 2
Diffusion bonding is a solid state welding technique, in which heat and high pressure is applied to the components to be bonded in a direction normal to the bond interface at high temperatures, such that atoms of respective bonding surfaces of the articles intermingle over time to form a bonded article
Data Source
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Figure 3a~3b
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AI summary
A method of bonding a first article (12) to a second article (26), each article (12, 26) having a respective bond surface (14, 28). The method comprises interposing a porous interlayer region (16) between the bond surfaces (14, 28) of the first and second articles (12, 26) and subsequently using electrical resistance heating to locally heat the interlayer region (16) under contact pressure to a bonding temperature below the melting temperature of the interlayer (16) and the first and second articles (12, 26) to thereby bond the interlayer (16) to the first and second articles (12, 26) to form a bonded article. The interlayer (16) has a porosity of between approximately 10% and 30%