Ceramic Coating Sintering Agents to Reduce Crystallization Cracks
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Solution Overview
Problem
Existing ceramic coatings for jet engine components in high-temperature environments suffer from microcracking during crystallization, which compromises their protective effectiveness and operational lifespan due to oxidative species penetration and thermal protection failure.
Innovation Solution
Incorporation of a low amount (0.1 to 10 wt.%) of metal oxides such as Al2O3, SiO2, Nb2O3, MgO, CaO, or BaO as sintering agents in the coating composition to mitigate crack formation during crystallization, enhancing the stability and adhesion of environmental barrier and thermal barrier coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic coatings are applied to jet engine components to protect from high temperatures and corrosive environments, then the protective effectiveness is improved, but microcracking occurs during crystallization which compromises the coating's durability and leads to oxidative species penetration
Solution Approach 1:
The patent modifies the chemical composition parameters of the coating by incorporating specific metal oxides (Al2O3, SiO2, Nb2O3, MgO, CaO, BaO) as sintering agents. These additives change the crystallization behavior and phase transformation characteristics of the coating, enabling it to form a dense, crack-free microstructure while maintaining protective properties against high temperatures and corrosive environments.
Solution Approach 2:
The patent creates a composite coating system by combining traditional ceramic coating materials with specific metal oxide sintering agents. This composite approach leverages the protective properties of the base ceramic while the metal oxide additives provide sintering functionality, resulting in a unified coating structure that achieves both protection and structural integrity without microcracking.
2Ease of manufacture
If thermal spraying is used to apply ceramic coatings, then the coating can be deposited on substrate surfaces, but the crystallization process causes notable shrinkage that leads to microcracking and larger cracks
Solution Approach 1:
The metal oxide sintering agents act as intermediary substances that facilitate the crystallization process. These additives mediate between the amorphous deposited state and the final crystalline structure, enabling controlled phase transformation that minimizes shrinkage and prevents crack formation while maintaining the coating's protective functionality.
Solution Approach 2:
The patent changes the thermal and chemical parameters of the coating system by introducing sintering agents that modify the crystallization kinetics and phase transformation temperature. This parameter modification allows for controlled crystallization that reduces shrinkage-induced cracking while maintaining manufacturing feasibility through thermal spraying.
3Object-affected harmful factors
If the coating is made dense with low porosity to minimize vapor permeability, then protection from corrosive gases is improved, but crack formation during crystallization compromises this density and allows oxidative species penetration
Solution Approach 1:
The patent modifies the microstructural parameters of the coating by incorporating sintering agents that control crystallization behavior. This results in a dense coating microstructure with low porosity that prevents corrosive gas infiltration, while the controlled crystallization process eliminates microcracks that would otherwise compromise coating integrity and 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
Reduces crack formation and improves the durability and longevity of ceramic coatings by stabilizing the crystalline phase, thereby protecting jet engine components from high temperatures and corrosive environments.
Implementation Method 1
The crystallization process (amorphous-crystalline phase transformation) for ceramics, such as hafnon (hafnium silicate) and mullite, involves notable shrinkage.
Implementation Method 2
Once deposited, an additional thermal exposure above the crystallization temperature is required to sinter the coating into a stable crystalline ceramic phase.
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.
Data Source
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.