Non-Reactive Brazing of Silicon Carbide in Oxidizing Atmosphere
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Solution Overview
Problem
Current brazing techniques for silicon carbide materials are inadequate for producing components with complex shapes and large sizes that require high mechanical strength and sealing capabilities at temperatures up to 1250°C, as they involve reactive solder compositions that degrade under oxidizing atmospheres like air, and existing processes are either too expensive or result in fragile bonds.
Innovation Solution
A non-reactive brazing process using a solder composition of silica (SiO2), alumina (Al2O3), and calcium oxide (CaO) or alumina (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) with a silicon addition to the surfaces or within the solder, allowing brazing under an oxidizing atmosphere at moderate temperatures, ensuring strong and refractory bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional brazing techniques are used for silicon carbide materials, then assembly can be achieved, but the bonds become fragile and mechanical strength is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the brazing material by adding silicon to the oxide-based composition. This parameter change transforms the brazing material's properties, enabling it to form strong, reliable bonds with silicon carbide substrates while resisting oxidation at high temperatures, thereby resolving the contradiction between mechanical strength and bond reliability
Solution Approach 2:
The patent uses a composite brazing material consisting of multiple oxides (such as Al2O3, SiO2, MgO, CaO) combined with silicon. This composite composition provides both the refractory properties needed for high-temperature stability and the reactivity required to form strong bonds with SiC, thus achieving both high mechanical strength and reliable bonding
2Ease of manufacture
If reactive solder compositions are used, then brazing can be achieved, but degradation occurs under oxidizing atmospheres like air
Solution Approach 1:
The patent introduces an intermediary protective layer formed by silicon oxidation. The silicon in the brazing composition reacts with oxygen to form a stable oxide layer that protects the underlying reactive components from further oxidation, allowing the brazing to proceed in air while maintaining composition stability
Solution Approach 2:
The patent modifies the compositional parameters by incorporating silicon into the oxide-based brazing material. This change enables the material to withstand oxidizing atmospheres while maintaining ease of manufacture, as the silicon provides oxidative resistance without significantly complicating the brazing process
3Strength
If high temperatures are used for brazing, then mechanical strength is improved, but component degradation occurs at elevated temperatures
Solution Approach 1:
The patent optimizes the brazing temperature parameter to a moderate range (1000-1200°C) that is sufficient to achieve strong joints without causing thermal degradation of the silicon carbide components. The modified brazing composition enables strong bonding at these moderate temperatures, resolving the contradiction between joint strength and thermal stability
4Adaptability or versatility
If complex shaped parts are manufactured, then component functionality is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent applies the brazing composition to the surfaces of complex-shaped parts before assembly, allowing the material to flow and conform to intricate geometries. This preliminary application simplifies the manufacturing of complex structures by enabling reliable joining of parts with challenging shapes that would be difficult to machine or assemble using other methods
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 process achieves high mechanical strength and sealing capabilities for silicon carbide-based components, preventing degradation at elevated temperatures and enabling the assembly of complex and large structures with improved mechanical properties and reduced reactivity, while being cost-effective and adaptable to various geometries.
Implementation Method 1
the assembly formed by the parts and the brazing composition is heated to a brazing temperature sufficient to either melt the brazing composition totally or at least partially, or make the brazing composition viscous
Implementation Method 2
a non-reactive brazing process using a solder composition of silica (SiO2), alumina (Al2O3), and calcium oxide (CaO) or alumina (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) with a silicon addition to the surfaces or within the solder, allowing brazing under an oxidizing atmosphere
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
The invention relates to a method for assembling at least two parts (1, 2) made of silicon carbide materials by means of non-reactive brazing in an oxidizing atmosphere, each of the parts (1, 2) including a surface (4, 5) to be assembled, wherein the parts (1, 2) are placed in contact with a non-reactive brazing composition (3), the assembly formed by the parts (1, 2) and the brazing composition (3) are heated at a brazing temperature sufficient for completely or at least partially melting the brazing composition (3), or rendering the latter viscous, and the parts (1, 2) and the brazing composition (3) are cooled so as to form, after the cooling of the latter to ambient temperature, a moderately refractory gasket, wherein the non-reactive brazing composition (3) is a composition A consisting of silica (SiO2), alumina (Al2O3), and calcium oxide (CaO), or a composition B consisting of alumina (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO), and wherein, before heating the assembly formed by the parts (1, 2) and the brazing composition (3) at the brazing temperature, silica in a non-oxidized form is provided on the surfaces (4, 5) to be assembled of the parts (1, 2) to be assembled, and/or on the surface layers, including the surfaces (4, 5) to be assembled of the parts (1, 2) to be assembled, and/or in the brazing composition (3). The invention also relates to a brazing composition, to a refractory gasket, and to an assembly.