Ytterbia-Stabilized Zirconia Silicate Coating for Thermal Stress
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Solution Overview
Problem
High-temperature ceramic composites used in aircraft engines and gas turbines face issues with heat-shielding coating delamination due to thermal expansion mismatch and inadequate steam resistance, leading to coating damage and erosion.
Innovation Solution
A zirconia-dispersed silicate coating layer is formed on a substrate using a mixture of rare earth disilicates and monosilicates, with ytterbia-stabilized zirconia as a dispersed phase, to reduce thermal expansion mismatch and enhance steam resistance, thereby preventing delamination and erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If ytterbia-stabilized zirconia is used as a heat-shielding coating layer, then phase stability at high temperature is improved, but thermal expansion mismatch with the substrate causes coating delamination
Solution Approach 1:
The invention uses a composite coating layer comprising ytterbia-stabilized zirconia particles dispersed in a rare earth silicate matrix. This composite structure combines the phase stability of zirconia with the thermal expansion compatibility of rare earth silicates, resolving the contradiction between phase stability and coating adhesion.
Solution Approach 2:
The invention changes the thermal expansion parameter by selecting rare earth silicates (such as Y2SiO5, Yb2Si2O7, Lu2Si2O7) as the matrix material, which have thermal expansion coefficients matching the substrate. This parameter adjustment eliminates thermal stress while maintaining the phase stability benefits of ytterbia-stabilized zirconia.
2Reliability
If rare earth disilicate is used as a coating material, then thermal expansion compatibility with substrate is improved, but steam resistance is insufficient leading to erosion
Solution Approach 1:
The invention creates a composite coating where rare earth disilicate provides thermal expansion compatibility while ytterbia-stabilized zirconia dispersed throughout the matrix provides enhanced steam resistance and erosion protection, resolving the contradiction between adhesion and steam resistance.
Solution Approach 2:
The invention applies local quality by dispersing ytterbia-stabilized zirconia particles throughout the rare earth silicate matrix, creating regions with different properties: the matrix provides thermal expansion compatibility while the zirconia particles provide steam resistance and erosion protection.
3Temperature
If yttria-stabilized zirconia is used as a heat-shielding coating, then thermal conductivity is reduced, but phase transformation at high temperature damages the coating
Solution Approach 1:
The invention changes the chemical composition parameter by replacing yttria (Y2O3) with ytterbia (Yb2O3) as the stabilizer for zirconia. This substitution maintains the low thermal conductivity required for heat-shielding performance while providing superior phase stability at high temperatures, preventing detrimental phase transformations.
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 layer provides excellent heat-shielding properties, suppresses thermal stress, and improves steam resistance, ensuring durability and longevity in high-temperature environments.
Implementation Method 1
A thermal expansion coefficient of ytterbia-stabilized zirconia is 10.3×10−6/K... a thermal expansion coefficient of an Al2O3 fiber-reinforced Al2O3 matrix composite is 6×10−6/K to 8×10−6/K... such that the thermal expansion coefficients of these materials are significantly smaller than that of the ytterbia-stabilized zirconia
Implementation Method 2
The yttria-stabilized zirconia has a low thermal conductivity of 1.5 W/mK
Implementation Method 3
since in a gas turbine combustion environment, a gas turbine is operated in a high-temperature and high-pressure steam oxidation environment, the silicon-based ceramic or the ceramic fiber-reinforced ceramic matrix composite becomes corroded and thinned due to steam while being oxidized
Data Source
AI summary
A coated member includes a heat-shielding coating layer made of a zirconia-dispersed silicate in which ytterbia-stabilized zirconia is precipitated as a dispersed phase in a matrix phase which is any one of a rare earth disilicate, a rare earth monosilicate, and a mixed phase of the rare earth disilicate and the rare earth monosilicate. The rare earth disilicate is a (Y1-a[Ln1]a)2Si2O7 solid solution wherein Ln1 is any one of Sc, Yb, and Lu, or a (Y1-c[Ln2]c)2Si2O7 solid solution wherein Ln2 is any one of Nd, Sm, Eu, and Gd. The rare earth monosilicate is Y2SiO5, [Ln1′]2SiO5, a (Y1-b[Ln1′]b)2SiO5 solid solution wherein Ln1′ is any one of Sc, Yb, and Lu, or a (Y1-d[Ln2′]d)2SiO5 solid solution wherein Ln2′ is any one of Nd, Sm, Eu, and Gd.