Jet Engine Ceramic Coatings With Sintering Agents for Crack Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ceramic coatings for jet engine components in high-temperature environments suffer from microcracking during crystallization, leading to reduced effectiveness and operational lifespan due to oxidative species penetration and thermal protection failure.
Innovation Solution
Incorporation of specific metal oxides such as Al2O3, SiO2, Nb2O3, MgO, CaO, and BaO in the coating composition to act as sintering agents, minimizing crack formation during the crystallization process of ceramic coatings like EBCs and TBCs, thereby enhancing their protective properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic coatings are applied by thermal spray to form deposited layers on the substrate, then the coating can be applied to protect the substrate from high temperatures and corrosive gases, but the coating contains amorphous phases that require additional thermal exposure to sinter into stable crystalline ceramic phases
Solution Approach 1:
The patent incorporates sintering agents (metal oxides such as Al2O3, SiO2, MgO, CaO, BaO) into the coating composition before thermal spraying. These agents are preliminarily positioned in the coating to facilitate the sintering process during subsequent thermal exposure, enabling the amorphous phases to transform into stable crystalline ceramic phases more effectively and reducing the need for complex additional processing steps
Solution Approach 2:
The patent creates a composite coating material by combining ceramic particles (hafnium silicate, zirconium silicate, rare earth phosphates, rare earth oxides, alumina, aluminosilicates) with sintering agents (metal oxides). This composite structure allows the coating to maintain its protective functions while incorporating elements that promote crystallization and reduce microcrack formation during the sintering process
2Reliability
If the coating is made dense to minimize vapor permeability, then the coating can protect the substrate from corrosive water vapor, but the crystallization process involves notable shrinkage that can cause microcracking within the coating
Solution Approach 1:
The patent modifies the chemical composition parameters of the coating by adding metal oxide sintering agents. These agents change the physical and chemical parameters during sintering, affecting the shrinkage behavior and crystallization process. The presence of these agents helps control the transformation from amorphous to crystalline phases, reducing the abrupt volume changes that cause microcracking while maintaining coating density
Solution Approach 2:
The sintering agents (metal oxides) act as intermediaries during the crystallization process. They facilitate the transformation of amorphous phases into crystalline phases by providing nucleation sites and controlling the reaction kinetics. This intermediary role helps manage the shrinkage process, reducing stress concentration and preventing microcrack formation in the dense coating structure
3Stability of the object's composition
If microcracks are present in the coating, then the coating can accommodate shrinkage during crystallization, but microcracks provide a quick access path for oxidative species to reach the underlying material thus are detrimental to EBCs performance
Solution Approach 1:
The patent converts the potentially harmful shrinkage effect into a beneficial outcome by using sintering agents that control the crystallization process. Instead of allowing uncontrolled shrinkage to create microcracks, the metal oxide agents facilitate a more gradual and uniform phase transformation, turning the shrinkage phenomenon into a controlled process that maintains coating integrity while achieving stable crystalline structure
Solution Approach 2:
By changing the chemical composition parameters (adding metal oxide sintering agents), the patent modifies the physical behavior during crystallization. The agents alter the shrinkage characteristics and crystallization kinetics, enabling the coating to transform from amorphous to crystalline phases with minimal volume change and stress accumulation, thereby preventing microcrack formation that would allow oxidative species penetration
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 addition of these metal oxides reduces crack formation, improving the durability and operational lifespan of ceramic coatings by maintaining their integrity and protective functions against high temperatures and corrosive gases.
Implementation Method 1
an additional thermal exposure above the crystallization temperature is required to sinter the coating into a stable crystalline ceramic phase
Implementation Method 2
The crystallization process (amorphous-crystalline phase transformation) for ceramics, such as hafnon (hafnium silicate) and mullite
Implementation Method 3
Coatings such as EBCs, TBCs, and machinable coatings can be prepared by thermal spraying such as plasma spraying using powders to form deposited layers on the substrate being treated
Implementation Method 4
TBCs are ceramic coatings that exhibit very low thermal conductivity and thus protect the underlying substrate to which they are applied from excessive temperatures
Data Source
Figure 1
Figure 2~4
AI summary
A coated substrate is described for use as part of a jet engine component which includes a substrate and a coating system. The substrate can be a ceramic matrix composite or a superalloy substrate. The coating system is applied to the substrate by thermal spraying such as APS. The coating system includes a layer containing as hafnium silicate (hafnon), zirconium silicate (zircon), a rare earth phosphate (REPO4), rare earth oxides (RE2O3), alumina, an aluminosilicate, rare earth-stabilized zirconia, and HfO2-SiO2-rare earth (RE) oxide, hafnia (HfO2) stabilized (partially or fully) by the addition of another component, zirconia (ZrO2) coating stabilized (partially or fully) by the addition of another component, a rare earth zirconate (RE2Zr2O7), a rare earth hafnate (RE2Hf2O7), and combinations thereof, wherein RE is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. To mitigate crack formation during amorphous-crystalline phase transformation, the layer further contains 0.1 to 10 wt.% of a metal oxide selected from Al2O3, SiO2, Nb2O3, MgO, CaO, SrO, BaO, and combinations thereof, as a sintering agent.