Composite Abradable Layer Adhesion via Reactive Metal Oxidation
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Solution Overview
Problem
Existing abradable layers in gas turbine engines are expensive to manufacture due to high powder consumption during the plasma spray process, where the powder does not strongly adhere to the air seal, leading to inefficiencies in material deposition.
Innovation Solution
A composite layer comprising a metal phase, a first ceramic phase (such as boron nitride or graphite), and a second ceramic phase (like hydrous aluminium phyllosilicate or metal oxide with a small average particle size) is formed by thermally spraying the powders, where the second ceramic phase melts and agglomerates with the first ceramic phase within the metal phase, enhancing adherence and reducing material consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plasma spray process is used to deposit powder onto an air seal as the abradable layer, then the abradable layer can be formed to provide erosion protection and facilitate efficient engine operation, but the powder does not strongly adhere to the air seal during the spray process, leading to significant powder consumption without deposition and high manufacturing expense
Solution Approach 1:
The patent changes the chemical composition parameters of the abradable layer by incorporating reactive metal powders (aluminum, magnesium, calcium, or their alloys) that undergo exothermic reactions with oxygen during or after plasma spraying. This chemical transformation fundamentally alters the adhesion mechanism from purely physical to chemically bonded, resolving the adherence problem while reducing material loss through the reactive bonding process
Solution Approach 2:
The patent replaces the mechanical adhesion mechanism (physical bonding of powder to substrate) with a chemical reaction mechanism (exothermic oxidation of reactive metals). This substitution transforms the deposition process from a mechanically-dependent spray process to a chemically-driven bonding process, significantly improving adherence and reducing powder consumption
2Ease of manufacture
If conventional abradable layers are manufactured using plasma spray process with high powder consumption, then the abradable layer can be deposited, but the manufacturing cost increases significantly due to material waste
Solution Approach 1:
The patent modifies the material composition parameters by using reactive metal powders that chemically bond during spraying, improving deposition efficiency and reducing rework. This changes the manufacturing process from material-intensive to reaction-driven, enhancing both ease of manufacture and productivity by reducing material waste and simplifying the deposition process
Solution Approach 2:
The reactive metal powders perform dual functions: they serve as both the structural material for the abradable layer and as the bonding agent through exothermic reactions. This self-service mechanism eliminates the need for separate adhesive applications or complex surface preparation, improving ease of manufacture and overall manufacturing efficiency
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 method facilitates economic manufacturing by improving the bonding and adherence of the abradable layer, reducing material usage, and enhancing erosion resistance while maintaining efficient abradability, thus lowering production costs and engine density.
Implementation Method 1
the thermal spraying is conducted at a temperature that melts the metal phase and the second ceramic phase but is below the melting point of the first ceramic phase such that the first ceramic phase is unmelted
Implementation Method 2
a thermal spray composition for an abradable seal is disclosed
Data Source
Figure 1
Figure 2~4
AI summary
A composite article (30) includes a substrate (46) and a layer (50) attached to the substrate (46). The layer includes a metal phase (60), a first ceramic phase (62), and a second ceramic phase (64).