Alumina-Based Coating for CMAS Mitigation in Turbine Engines
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Solution Overview
Problem
Current thermal barrier coatings for gas turbine components are susceptible to damage from environmental contaminants like CMAS, which infiltrate and cause spallation and delamination, and existing alumina-based coatings are either expensive, limited in thickness, or incompatible with high-temperature operations.
Innovation Solution
A thermally sprayed alumina-based coating with a composition of at least 60 weight percent alumina and titania, zirconia, and gadolinia is applied to raise the CMAS melting point and provide anti-fouling protection, with a smooth surface roughness of less than 4.0 micrometers to reduce infiltration and fouling, and can be applied quickly without drying or curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thermal barrier coating is made thinner to reduce weight, then the weight of the turbine component is reduced, but the thermal insulation performance deteriorates
Solution Approach 1:
The patent applies composite materials by combining alumina (providing low thermal conductivity and CMAS resistance) with zirconia (providing excellent thermal insulation). This composite structure allows the coating to maintain superior thermal insulation performance at reduced thickness, thereby reducing component weight while preserving thermal protection.
Solution Approach 2:
The patent changes the compositional parameters of the thermal barrier coating by incorporating alumina in specific proportions (at least 60 weight percent) along with zirconia and other oxides. This parameter optimization enables the coating to achieve both low thermal conductivity and enhanced CMAS resistance, allowing thinner application while maintaining performance.
2Object-affected harmful factors
If the alumina content in the coating is increased to improve CMAS resistance, then the resistance to environmental contaminants is improved, but the thermal conductivity may increase
Solution Approach 1:
The patent uses a composite material system where alumina (60-95 weight percent) provides CMAS resistance and low thermal conductivity, while zirconia (5-40 weight percent) contributes to thermal insulation and structural stability. This synergistic composite structure achieves both high CMAS resistance and maintained low thermal conductivity.
Solution Approach 2:
The patent optimizes the compositional parameters by precisely controlling the ratios of alumina, zirconia, and other oxides (titania, gadolinia). This parameter optimization ensures that the coating maintains adequate alumina content for CMAS resistance while preserving overall low thermal conductivity through the balanced composite formulation.
3Object-affected harmful factors
If a dense coating structure is applied to prevent CMAS infiltration, then the resistance to environmental contaminants is improved, but the strain tolerance and crack propagation resistance deteriorate
Solution Approach 1:
The patent applies local quality by creating a coating with non-uniform microstructure: the outer layer has higher alumina content providing density and CMAS resistance, while the inner layer has optimized composition for strain tolerance. This spatial variation in composition and structure allows the coating to simultaneously achieve contaminant resistance and mechanical durability.
Solution Approach 2:
The composite material system provides different functional zones within the coating structure. The alumina-rich outer layer offers density and CMAS barrier properties, while the zirconia-containing inner layer provides strain tolerance and crack resistance, achieving both requirements through composite architecture.
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 alumina-based coating effectively mitigates CMAS infiltration and fouling, maintaining thermal protection up to 1649°C (3000°F) with reduced porosity and surface roughness, preventing spallation and extending the service life of turbine components.
Implementation Method 1
alumina-based coating... to raise the CMAS melting point
Implementation Method 2
thermally spraying the alumina powder onto the thermal barrier coating
Data Source
Figure 1
AI summary
A thermally sprayed alumina-based coating is deposited onto a thermal barrier coating to provide an article such as a turbine engine component with both CMAS mitigation and antifouling. The alumina-based coating increases a melting point of the CMAS to a temperature greater than an operating temperature of the turbine engine component. The surface roughness of the thermally sprayed alumina based coating in less than 4.0 micrometers to 0.75 micrometers. The alumina based coatings include at least 60 weight percent alumina based on a total weight of the alumina-based coating.