Ceramic-Metal Joint via Electrical Heating
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Solution Overview
Problem
Existing methods for joining ceramic and metal bodies, such as furnace brazing, are not suitable for high-temperature applications due to creep weakness in brazing materials and the risk of cracks in ceramics when directly heated.
Innovation Solution
A method involving electrical heating of the abutment surface between ceramic and metal bodies, with specific temperature and time control steps to achieve a diffusion region that prevents cracks and ensures high joining strength, including a first heating step to T1 within (Tr-220)° C. to (Tr-50)° C., a second step to T2 between Tm×0.3° C. and Tm×0.45° C., and a third step above Tm×0.48° C. but below Tm×0.6° C., to create a stable joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If furnace brazing is used to join ceramic and metal bodies, then the joining process is simple and widely applicable, but the brazing material has weakness in creep resistivity under high temperature environment making it unsuitable for high-temperature applications
Solution Approach 1:
The invention removes the brazing material from the joining system entirely, achieving direct bonding between ceramic and metal bodies through electrical heating. This eliminates the creep weakness inherent in brazing materials while maintaining ease of manufacture through a streamlined process that requires only electrical heating without intermediate brazing layers.
Solution Approach 2:
The invention introduces an intermediate diffusion layer formed in-situ at the ceramic-metal interface through controlled electrical heating. This diffusion layer acts as a mediator that facilitates strong bonding between ceramic and metal while withstanding high-temperature creep stresses, replacing the need for external brazing materials.
2Reliability
If direct heating is used to join metal and ceramic together, then brazing material is eliminated, but cracks may occur in the ceramic due to uncontrolled thermal stress
Solution Approach 1:
The invention applies preliminary controlled heating in stages before final high-temperature bonding. The multi-stage electrical heating process gradually increases temperature and forms a diffusion layer in advance, preventing sudden thermal shock that would cause ceramic cracks while achieving reliable high-temperature resistance in the final bond.
Solution Approach 2:
The invention dynamically controls the heating process through multiple stages with different temperature profiles and durations. The heating parameters are adjusted in real-time based on the bonding progress, allowing the system to adapt to the ceramic's thermal tolerance and prevent crack formation while achieving complete bonding.
3Strength
If multi-stage electrical heating is applied with specific temperature control, then joining strength and crack prevention are achieved, but the process complexity increases
Solution Approach 1:
The invention employs self-heating through resistive heating where the ceramic and metal bodies themselves generate heat when electrical current passes through them. This eliminates the need for external heating devices and complex temperature control systems, achieving high joining strength through simple electrical power application while the materials self-regulate the heating process.
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 a high joining strength and prevents cracks in the ceramic body, making the joint suitable for high-temperature applications like vehicle-mounted parts, with a stable diffusion region and controlled thermal expansion.
Implementation Method 1
applying a voltage between the ceramic body and the metal body to pass a current to an abutment surface between the ceramic body and the metal body to thereby heat the abutment surface
Implementation Method 2
heating the abutment surface for a period longer than 10 seconds... heating the abutment surface for a period longer than 5 seconds... heating the abutment surface for a period longer than 3 seconds to create a stable joint with a diffusion region
Data Source
AI summary
A method of manufacturing a joint body of a ceramic body and a metal body includes a step of joining them together by passing a current to an abutment surface between them. The joining step includes a step of heating up the abutment surface to a temperature T1 within a temperature range between (Tr-220)° C. and (Tr-50)° C. in a period longer than 10 seconds, Tr being a recrystallization temperature of the metal body, a step of heating the abutment surface for a period longer than 5 seconds at a temperature T2 within a temperature range between Tm×0.3° C. and Tm×0.45° C., Tm being a melting point of the metal body, and a step of heating the abutment surface for a period longer than 3 seconds at a heating temperature higher than Tm×0.48° C. and lower than Tm×0.6° C.