Ceramic Hot Corrosion Coating for Turbine Disks Without Interdiffusion
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Solution Overview
Problem
Existing metallic coatings for gas-turbine engine components are unsuitable for turbine disks due to high processing temperatures that alter the microstructure and cause interdiffusion, leading to reduced fatigue life, while silicone-based and phosphate-containing coatings lack thermal stability and corrosion resistance in type II hot corrosion environments.
Innovation Solution
A multilayer coating system using silicate-based aqueous binders and ceramic matrices, free of chromate, phosphate, sodium, and potassium, with incorporated metal oxide and metallic particles, forming a thermally stable and adherent ceramic matrix for type II hot corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic coatings are applied to provide hot corrosion protection, then corrosion resistance is improved, but processing temperature exceeds 1500°F causing microstructure alteration and interdiffusion that reduce fatigue life
Solution Approach 1:
The patent changes the processing temperature parameter from above 1500°F (conventional metallic coatings) to below 1100°F (silicate-based ceramic coatings), enabling corrosion protection without microstructure alteration or interdiffusion that would reduce fatigue life
Solution Approach 2:
The patent uses composite ceramic coatings with silicate-based glassy matrix combined with corrosion-resistant particles (alumina, chromia, zirconia, rare earth oxides) to achieve both corrosion resistance and thermal stability without the drawbacks of conventional metallic coatings
2Ease of manufacture
If silicone-based coatings are used to lower processing temperature, then ease of manufacture is improved, but thermal stability and corrosion resistance deteriorate due to phase transformation and volume change
Solution Approach 1:
The patent replaces silicone-based binders with alkali-free silicate-based binders that maintain thermal stability up to 1400°F without phase transformation or volume change, while still enabling low-temperature processing below 1100°F
Solution Approach 2:
The patent creates a glassy ceramic matrix with controlled porosity that accommodates thermal expansion and prevents cracking, maintaining both ease of manufacture and thermal stability
3Ease of manufacture
If phosphate-containing coatings are applied to improve adhesion, then ease of manufacture is improved, but corrosion resistance deteriorates in type II hot corrosion environments
Solution Approach 1:
The patent replaces phosphate-containing adhesion promoters with alkali-free silicate-based binders that provide both adhesion and corrosion resistance by forming a stable glassy ceramic matrix that resists molten sulfate attack
Solution Approach 2:
The patent eliminates the need for separate adhesion promoter layers by integrating adhesion functionality into the silicate-based binder itself, simplifying the coating system while maintaining performance
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 multilayer coating system provides superior resistance to type II hot corrosion without interdiffusion, maintaining mechanical properties and adhesion at temperatures up to 1400°F, ensuring long-term protection and integrity.
Implementation Method 1
The binder is dried and cured to form a silicate-based ceramic matrix phase
Implementation Method 2
superior resistance to type II hot corrosion without interdiffusion, maintaining mechanical properties and adhesion at temperatures up to 1400°F
Data Source
AI summary
Novel multilayer aqueous slurries and coatings for hot corrosion protection of substrates are provided that exhibit improved resistance to type II hot corrosion while also being hexavalent chromium free. The compositions represent a notable departure and performance improvement from conventional coating systems utilized for hot corrosion protection.