CMAS-Resistant Gas Turbine Coating via Reactive Topcoat
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Solution Overview
Problem
Gas turbine engine components face challenges in thermal and oxidative stability due to high temperatures, corrosive, and oxidative conditions, which existing coatings fail to adequately address.
Innovation Solution
A composite barrier layer is applied, comprising a bond coat with silicon dioxide matrix and gettering particles, and a topcoat reactive with calcium-magnesium-alumino-silicate (CMAS), using thermal spray methods to enhance durability and protect against CMAS deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If existing protective barrier coatings are applied to gas turbine engine components, then thermal stability is improved, but oxidative stability and resistance to CMAS deposits are insufficient
Solution Approach 1:
The patent applies a composite barrier coating system consisting of a bond coat layer containing gettering particles (such as aluminum, silicon, or their compounds) and a topcoat layer with CMAS-reactive constituents (such as rare earth oxides, hafnium oxide, or zirconium oxide). This composite structure combines the oxidation-resistant properties of the bond coat with the CMAS-resistance of the topcoat, thereby simultaneously improving both oxidative stability and CMAS deposit resistance while maintaining thermal stability.
Solution Approach 2:
The bond coat layer acts as an intermediary between the substrate and the topcoat, providing oxidation protection to the substrate while the topcoat serves as an intermediary that reacts with CMAS deposits to protect the underlying structure. This two-layer intermediary system effectively addresses both oxidative and CMAS-related degradation mechanisms that single-layer coatings cannot adequately prevent.
2Duration of action of stationary object
If a protective barrier coating is applied to improve thermal stability, then component durability is enhanced, but the coating fails to adequately protect against corrosive and oxidative conditions
Solution Approach 1:
The dual-layer composite coating structure combines materials with complementary properties: the bond coat uses aluminum-based or silicon-based gettering particles that provide superior oxidation resistance, while the topcoat employs rare earth oxides or other CMAS-reactive materials that resist corrosive attacks. This composite approach extends component durability by protecting against multiple harmful factors simultaneously.
Solution Approach 2:
The topcoat layer is designed to react beneficially with CMAS deposits, converting the harmful corrosive action into a protective reaction layer. The CMAS-reactive constituents (such as gadolinium oxide, terbium oxide, or hafnium oxide) chemically react with CMAS to form stable, protective compounds that prevent further corrosive penetration, thereby converting the harmful corrosive environment into a beneficial protective mechanism.
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 solution significantly improves the thermal and oxidative stability of gas turbine engine components by forming a protective barrier that reacts with CMAS deposits, reducing damage and extending component lifespan.
Implementation Method 1
a topcoat including a constituent that is reactive with calcium-magnesium-alumino-silicate (CMAS)
Implementation Method 2
depositing a topcoat onto a bondcoat by thermal spray
Data Source
AI summary
An article according to an exemplary embodiment of this disclosure, among other possible things includes a substrate and a barrier layer on the substrate. The barrier layer includes a bond coat comprising a matrix, diffusive particles disposed in the matrix, and gettering particles disposed in the matrix; and a topcoat including a constituent that is reactive with calcium-magnesium-alumino-silicate (CMAS). An article and a method applying a calcium-magnesium-alumino-silicate (CMAS)-resistant topcoat are also disclosed.