Pyrochlore Thermal Barrier Coating for CMAS Resistance
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Solution Overview
Problem
Thermal barrier coatings used in high-temperature applications, such as turbine components, are susceptible to damage from environmental contaminants like CMAS, leading to premature failure due to infiltration, cracking, and delamination, which increases maintenance and operational costs.
Innovation Solution
Development of a thermal barrier coating composition with a nominal oxide structure of AxB1-yDyOz, where A includes a rare-earth element, B includes tantalum or niobium, and D includes zirconium or hafnium, providing low thermal conductivity and reactivity with CMAS, thereby functioning as both a thermal barrier and a CMAS-reactive protective coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional rare earth stabilized zirconia (YSZ) is used as thermal barrier coating, then good phase stability and high temperature capability are achieved, but thermal conductivity is relatively high (2.2 W/m-K) and coating thickness/weight cannot be reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the thermal barrier coating by incorporating pyrochlore-phase oxides with specific stoichiometry (A2B2O7 or A2B2O6.5) where A is a rare earth element and B is a transition metal. This compositional parameter change results in lower thermal conductivity (1.5-2.0 W/m-K) compared to conventional YSZ, allowing thickness reduction while maintaining thermal barrier performance at high temperatures
Solution Approach 2:
The patent creates a composite coating system combining pyrochlore-phase oxide materials with specific rare earth and transition metal combinations. This composite approach leverages the low thermal conductivity of pyrochlore structure while maintaining phase stability through careful selection of constituent elements, achieving both reduced material quantity and sustained high-temperature capability
2Reliability
If thermal barrier coating is applied to protect substrate, then protection against high temperature is achieved, but susceptibility to CMAS contamination and infiltration damage occurs
Solution Approach 1:
The patent converts the harmful effect of CMAS contamination into a beneficial protective mechanism by selecting pyrochlore-phase oxide materials that react with CMAS to form stable, protective reaction products. The low thermal conductivity materials resist thermal shock that would otherwise accelerate CMAS infiltration, and any CMAS reaction products formed create a protective layer that prevents further degradation, thus converting the harmful contamination into a protective barrier
Solution Approach 2:
The patent changes the chemical composition parameters of the coating to include specific rare earth-transition metal oxide combinations with controlled stoichiometry. These compositional changes create materials with optimized thermal properties and chemical stability that resist CMAS infiltration while maintaining thermal barrier function, addressing both thermal protection and contamination resistance simultaneously
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 composition effectively reduces thermal conductivity and protects against CMAS damage, offering improved durability and reduced material usage, thus enhancing the performance and lifespan of high-temperature components.
Implementation Method 1
Rare earth stabilized zirconia materials have a thermal conductivity of about 2.2 W/m-K when evaluated as a dense sintered compact. The YSZ is widely used as a TBC material in gas turbines, in part, because of its high temperature capability, low thermal conductivity
Implementation Method 2
these environmental contaminants can adhere to the heated or hot thermal barrier coating surface, and thus cause damage to the thermal barrier coating. For example, CMAS can form compositions that are liquid or molten at the operating temperatures of the turbines. The molten CMAS composition can dissolve the thermal barrier coating, or can infiltrate its porous structure
Data Source
AI summary
An article for high temperature service is presented. The article includes a substrate and a plurality of coatings disposed on the substrate. At least one coating in the plurality of coatings includes an oxide of nominal composition AxB1-yDyOz, wherein A includes a rare-earth element, B includes tantalum or niobium, D includes zirconium or hafnium, 2≤x≤3, 0<y<1, and 6≤z≤7.