Diffusion Blocking Layer in Exhaust Treatment Units
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Solution Overview
Problem
Existing methods for producing exhaust gas treatment units with metallic honeycomb bodies face challenges in precisely forming soldered connections while avoiding undesirable diffusion connections, which complicates the manufacturing process, increases costs, and reduces flexibility under varying temperatures and pressures.
Innovation Solution
A method involving the application of a metal oxide surface layer, such as cobalt or nickel oxide, on a metal sheet with a heat treatment process to form a diffusion barrier layer of aluminum oxide, preventing unwanted diffusion of elements and allowing controlled soldered connections only at predetermined points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soldering process is applied to join metallic components, then connection strength is improved, but undesirable diffusion connections form between components
Solution Approach 1:
The surface of the metallic component is divided into two distinct zones: a first zone with a metal oxide layer that prevents diffusion connections, and a second zone without the oxide layer that allows soldered connections. This spatial segmentation enables selective control over connection behavior at different locations on the same component surface.
Solution Approach 2:
Different surface properties are applied to different regions of the component. The first zone receives a metal oxide coating that creates diffusion barrier properties, while the second zone maintains the original metallic surface that enables solderability. This local differentiation allows the component to exhibit different connection characteristics in different areas.
2Object-generated harmful factors
If passivation layer is applied to prevent undesired solder connections, then diffusion connection prevention is improved, but solderability at contact points is reduced
Solution Approach 1:
The passivation layer (metal oxide) is applied selectively only to the first zone where diffusion prevention is needed, while the second zone remains free of the passivation layer to maintain solderability. This segmented application resolves the contradiction by providing protection only where required.
Solution Approach 2:
The component surface exhibits local quality differentiation: the first zone has passivated surface properties for diffusion prevention, while the second zone has active metallic properties for soldering. This local quality approach ensures that solderability is preserved at contact points while preventing unwanted diffusion elsewhere.
3Manufacturing precision
If targeted introduction of solder material is used to form connections only at specific points, then connection precision is improved, but process complexity increases
Solution Approach 1:
The metal oxide layer is applied in advance to the first zone before the soldering process. This preliminary passivation action simplifies the subsequent soldering step, as the selective connection formation is already prepared by the pre-applied oxide layer that prevents diffusion in the first zone while allowing it in the second zone.
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 precise and defined soldered connections while preventing undesirable diffusion connections, enhancing the durability and flexibility of exhaust gas treatment units by maintaining metallic properties for solderability and preventing chromium carbide formation.
Implementation Method 1
a heat treatment process is carried out with the metal sheet, as a result of which, in the at least one partial area, a diffusion barrier layer is formed comprising aluminum oxide, formed mainly by reduction of the metal oxide to a metal and (simultaneous) oxidation of aluminum diffusing out of the base material to aluminum oxide
Implementation Method 2
oxidation of aluminum diffusing out of the base material to aluminum oxide
Implementation Method 3
reduction of the metal oxide to a metal
Implementation Method 4
undesired diffusion connections, in particular chromium carbide connections, at contact points with adjacently arranged components are prevented
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a method for generating a diffusion blocking layer (1), comprising aluminum oxide (8) on a metal plate (2), which consists of a base material (3), which comprises at least iron (Fe), chromium (Cr) and aluminum (Al). The invention further relates to integrating said method into the production of an exhaust treatment unit (12), wherein the exhaust treatment unit (12) has a honeycomb body (13) and a housing (14) and at least the honeycomb body (13) or the housing (14) is formed with a metal plate (2) and the metal plate (2) consists of a base material (3) which comprises at least iron (Fe), chromium (Cr) and aluminum (Al). The metal plate (2) thus comprises, at least in a sub-region (5), a surface layer (7) which comprises at least aluminum oxide (8) and a metal (9) from the group consisting of cobalt (Co) and nickel (Ni).