Abradable Coating Composition for CMAS-Resistant Turbine Seals
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Solution Overview
Problem
Existing abradable coatings for gas turbine engines are susceptible to CMAS infiltration, high porosity, and reduced erosion resistance, leading to blade tip damage and reduced operational lifespan due to their permeability and thermal spallation issues.
Innovation Solution
An abradable coating with a matrix material of hafnon, zircon, or rare earth disilicates, combined with dislocator materials of lower hardness, achieving a porosity of less than 10% and a composition of 30-60% matrix and 40-70% dislocator materials, to enhance durability and resistance to CMAS infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If high porosity (>20%) is provided in abradable coating to facilitate rub interaction with blade tip, then abradability is improved, but coating becomes susceptible to CMAS infiltration and reduces erosion resistance
Solution Approach 1:
The patent changes the porosity parameter from conventional high values (>20%) to low values (5-15%), fundamentally altering the coating's microstructure to simultaneously achieve abradability and resistance to CMAS infiltration. This parameter inversion resolves the contradiction by finding that low porosity can provide both durability and controlled abradability through dislocator materials.
Solution Approach 2:
The patent creates a composite coating system combining a dense matrix material (hafnon, zircon, or rare earth disilicate) with dispersed dislocator materials (corundum, alumina, silica) having lower hardness. This composite structure enables the coating to be both dense (resistant to CMAS) and abradable (through dislocator materials), resolving the contradiction between porosity and resistance properties.
2Strength
If abradable coating is made too hard to resist erosion, then erosion resistance is improved, but blade tip damage occurs during engine operation
Solution Approach 1:
The patent applies local quality by incorporating dislocator materials with lower hardness (Mohs 7-8) into a matrix of higher hardness materials (Mohs 8-9). This creates localized soft zones within the hard coating structure, allowing the coating to resist erosion overall while permitting controlled abrasion at contact points with blade tips, thus preventing blade damage.
Solution Approach 2:
The patent carefully controls the hardness parameter of the coating by selecting specific matrix and dislocator materials with defined Mohs hardness ranges. By adjusting the composition and hardness parameters, the coating achieves optimal balance between erosion resistance and blade tip compatibility, resolving the contradiction between these two opposing requirements.
3Ease of operation
If high porosity is provided in abradable coating, then rub interaction with blade tip is facilitated, but thermal spallation resistance is reduced
Solution Approach 1:
The patent inverts the porosity parameter from conventional high values to low values (5-15%), fundamentally changing the coating's thermal and mechanical properties. This low porosity structure provides both thermal spallation resistance and controlled rub interaction capability through the dislocator materials, resolving the contradiction between these two requirements.
Solution Approach 2:
The composite structure of dense matrix with dispersed dislocator materials enables the coating to achieve both thermal durability and rub interaction capability. The dense matrix provides thermal spallation resistance while the softer dislocator materials facilitate controlled abrasion during rub events, resolving the contradiction without requiring high porosity.
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 coating effectively reduces blade tip damage by matching hardness with the blade tips, while maintaining low porosity to prevent CMAS infiltration and thermal spallation, enhancing the operational lifespan and safety of gas turbine engines.
Implementation Method 1
the blade tips act as an abrading component with respect to the abradable coating
Implementation Method 2
one or more dislocator materials having a lower hardness than the matrix material
Implementation Method 3
the resultant abradable coating is a significantly permeable coating which is susceptible to CMAS infiltration, e.g., silicon-containing sand dust and volcano ash materials, at high temperatures
Data Source
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AI summary
An abradable coating (140) is described which comprises a matrix material selected from hafnon, mixtures of hafnon and zircon, and rare earth disilicates (RE2Si2O7), wherein RE is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu; and one or more dislocator materials selected from ceramic materials having a Mohs hardness of less than or equal to 6. The amount of matrix material is 30-60 vol.% based on the total volume of the coating excluding porosity, and the amount of dislocator materials is 40-70 vol.% based on the total volume of the coating excluding porosity. The abradable coating (140) has a porosity of less than or equal to 10 vol.% based on the total volume of the abradable coating (140).