Reactive Brazing Alloy Composition for Alumina-Metal Sealing
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Solution Overview
Problem
Reactive brazing methods face challenges in achieving strong, reliable bonds between alumina ceramics and metals, particularly in vacuum interrupters, due to poor wettability and mechanical strength issues when the composition of the braze is poorly adapted to the metal, leading to visual defects and reduced mechanical strength.
Innovation Solution
A method using a brazing alloy with a specific composition of AgCuTi, where the titanium content is adjusted to form a thick and stable reaction layer on the alumina surface, minimizing non-wetting areas and maintaining intermetallic compounds below a certain value to enhance mechanical strength, without the need for preliminary metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive brazing alloys are used to improve wettability of alumina, then wettability is improved, but mechanical strength decreases and sealing defects occur
Solution Approach 1:
The invention changes the chemical composition parameters of the brazing alloy, specifically limiting reactive elements (Ti, V, Zr, Nb) to 0.1-5 wt% and intermetallic formers (Al, Fe, Ni, Cu) to 45-95 wt%, to achieve optimal balance between wettability and mechanical strength without excessive chemical activity that causes defects
Solution Approach 2:
The brazing alloy is designed as a composite system combining multiple elements with complementary functions: reactive elements for wettability enhancement, intermetallic formers for strength, and base metals for ductility, creating a balanced material that avoids the extremes of purely reactive or non-reactive alloys
2Strength
If metallization of alumina surface is performed to achieve strong bonds, then mechanical strength is improved, but process complexity and cost increase
Solution Approach 1:
The invention merges the brazing alloy composition design with the metallization function, incorporating reactive elements directly into the brazing alloy that can chemically bond to alumina surface during the brazing process itself, eliminating the need for separate metallization steps while achieving comparable or superior bond strength
Solution Approach 2:
The invention extracts the metallization function from the separate preprocessing step and integrates it into the brazing alloy composition, allowing the alloy itself to provide the chemical bonding capability previously requiring separate surface treatment operations
3Strength
If high chemical activity of reactive element with metal is used to improve bonding, then bonding is enhanced, but non-wetting areas and sealing defects increase
Solution Approach 1:
The invention precisely controls the concentration parameter of reactive elements within 0.1-5 wt% range, which is sufficient to enhance bonding through controlled chemical activity while remaining below the threshold that causes excessive reactivity, non-wetting areas, and sealing defects
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
This approach enables good wettability and mechanical strength in assemblies where reactive brazing was previously inadequate, allowing for reliable bonding and improved sealing without the complexity and cost of metallization, as demonstrated by the thickness of the reaction layer and probability of rupture graphs.
Implementation Method 1
The quality of the wetting is characterized by the wetting angle θ. If θ < 55°, the wetting is good and an intimate bond at the atomic scale will succeed in forming at any point of the interface.
Implementation Method 2
The reactive alloys developed to achieve brazing between oxide ceramics such as alumina and metals are mainly based on AgCu and most often contain titanium as a reactive element
Implementation Method 3
The brazing technique consists in a manner known per se in assembling two materials using a metal or a so-called 'filler' alloy whose melting point is lower than that of the materials to be assembled.
Data Source
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AI summary
A reactive brazing of primary metallic element with secondary element containing ion-covalent oxide is performed using alloy designed to constitute liquid brazing alloy designed to wet two metallic and ion-covalent oxide surfaces of two elements. The content of titanium in brazing alloy is 2-5 wt.%, when the content of metal which can form intermetallic compounds with titanium is less than 20 wt.%. The content of titanium is 5-10 wt.%, when the content of metal which can form intermetallic compounds with titanium metal is 20-50 wt.%. Thus, assembly method is enabled. A reactive brazing of primary metallic element with secondary element containing an ion-covalent oxide on the surface is performed using alloy designed to constitute liquid brazing alloy designed to wet the two metallic and ion-covalent oxide surfaces of the two elements. The brazing alloy contains titanium and metallic element contains nickel. The content of titanium in the brazing alloy is 2-5 wt.%, when the content of the metal which can form intermetallic compounds with titanium is less than 20 wt.%. The content of titanium is 5-10 wt.%, when the content of the metal which can form intermetallic compounds with titanium metal is 20-50 wt.%. The content of titanium is 2-5 wt.%, when the content of metal which can form intermetallic compounds with titanium is more than 50 wt.%. The content of silver is less than 60 wt.%, such that the non-wettability area on the surface of the secondary element obtained from ion-covalent oxide with thickness and stable reaction layer at the interface of the element is minimized, and the formation of intermetallic compounds in the brazed joint is minimized. Thus, assembly method is enabled. An independent claim is included for vacuum cartridge, which has cylindrical component and two end cover plates, in which at least one is assembled to the cartridge component.