Porous Abradable Ceramic Coating for Turbine Erosion
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Solution Overview
Problem
Conventional abradable coatings for turbomachines, especially in high-pressure turbines, face premature wear due to extreme thermal and physicochemical conditions, leading to reduced performance and increased risk of deflagration, which complicates the cooling system and increases production costs.
Innovation Solution
A porous abradable ceramic coating is manufactured using a process involving the partial filling of a mold with hollow glass or thermosetting polymer beads, followed by filtration and sintering heat treatment to create a ceramic layer with high porosity, reducing the risk of deflagration and enhancing erosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal barrier coating is used to protect the stator ring against erosion and corrosion, then the protection against extreme thermal and physicochemical conditions is improved, but the abradability deteriorates and the clearance between rotor and stator must be increased
Solution Approach 1:
The patent applies porous materials by incorporating hollow beads (glass or ceramic) into the coating matrix, creating a porous structure with controlled porosity (30-70%). This porous structure allows the coating to be abradable while maintaining protection against thermal and physicochemical conditions, resolving the contradiction between protection and abradability.
Solution Approach 2:
The patent uses composite materials by combining different materials (ceramic matrix with hollow beads, organic binder) to create a coating that simultaneously provides thermal barrier protection and abradability. The composite structure allows the coating to exhibit both protective and erodible characteristics.
2Ease of operation
If conventional abradable coatings are used in high-pressure turbines, then the abradability is improved, but the wear resistance deteriorates due to extreme thermal and physicochemical conditions
Solution Approach 1:
The porous structure formed by hollow beads provides controlled porosity that enables abradability while the ceramic matrix material provides wear resistance under extreme conditions, allowing both properties to coexist in the same coating.
Solution Approach 2:
The patent changes material parameters by selecting ceramic materials with high melting points and chemical stability, and controlling porosity within specific ranges (30-70%), to achieve both abradability and wear resistance simultaneously under extreme thermal and physicochemical conditions.
3Ease of operation
If aluminum-based abradable coatings are used, then the abradability is improved, but the risk of deflagration increases
Solution Approach 1:
The patent changes the chemical composition parameter by replacing aluminum-based materials with ceramic materials that have high chemical stability and do not undergo deflagration, while maintaining abradability through the porous structure formed by hollow beads.
Solution Approach 2:
The hollow beads act as sacrificial elements that are consumed during abrasion, creating the desired abradable surface while the ceramic matrix remains stable and non-flammable, eliminating deflagration risk.
4Ease of manufacture
If thermal spraying is used to manufacture porous ceramic coatings, then the manufacturing process is simplified, but the total porosity is limited to about 30% by volume
Solution Approach 1:
The patent applies preliminary action by pre-forming hollow beads with controlled internal voids before incorporating them into the coating matrix. This pre-prepared porosity allows achieving higher total porosity (30-70%) than conventional thermal spraying alone, while maintaining manufacturing simplicity.
Solution Approach 2:
The use of hollow beads as porosity generators enables achieving higher total porosity (30-70%) compared to conventional thermal spraying methods that are limited to about 30% porosity, while keeping the manufacturing process relatively simple.
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 high-porosity ceramic coating effectively mitigates wear and deflagration risks, maintaining performance while reducing production complexity and costs by ensuring the integrity of turbine components.
Implementation Method 1
a maximum sintering temperature of the ceramic part green body being either higher than the melting temperature of the hollow glass beads so that at the end of the sintering heat treatment, the hollow glass beads are melted
Implementation Method 2
higher than the decomposition temperature of the hollow thermosetting polymer beads so that at the end of the sintering heat treatment the hollow thermosetting polymer beads are decomposed
Implementation Method 3
sintering heat treatment of the green body of the ceramic part to obtain the ceramic layer with pores
Data Source
AI summary
A process for manufacturing a porous abradable coating includes: filling a mold with hollow glass or thermosetting polymer beads and a slurry; and sintering heat treatment to obtain a ceramic layer with pores. A maximum sintering temperature of the green body of the ceramic part is either higher than the melting temperature of the hollow glass beads so that at the end of the sintering heat treatment the hollow glass beads are melted, or higher than the decomposition temperature of the hollow thermosetting polymer beads so that at the end of the sintering heat treatment the hollow thermosetting polymer beads are decomposed.