Ceramic Coating Durability via Molten Droplet Deposition
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Solution Overview
Problem
Thick ceramic coatings used in high-temperature turbine applications suffer from deterioration and cracking due to sintering shrinkage, which causes planar tensile stresses and mudflat cracks, leading to reduced durability.
Innovation Solution
A process involving the deposition of fully molten ceramic droplets using thermal or plasma spray techniques, with preheating of the substrate and adjustment of plasma spray parameters to reduce micron-scale defects and sintering shrinkage, utilizing larger particles and a fugitive pore former to minimize porosity and stress concentrations, and achieving a fully graded compositional structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick ceramic coating is applied to substrate, then protective barrier is formed, but sintering shrinkage causes planar tensile stresses and cracking
Solution Approach 1:
The patent changes the particle size parameter from conventional fine particles to larger particles (10-50 microns), which fundamentally alters the sintering behavior and stress distribution in the coating, eliminating cracking while maintaining protective functionality
Solution Approach 2:
The substrate is preheated to 500-1500°F before coating deposition, which prepares the substrate to accommodate the thermal and mechanical stresses of the coating process, preventing crack initiation and improving overall coating durability
2Manufacturing precision
If conventional spray parameters are used, then coating is deposited, but micron scale defects and porosity increase
Solution Approach 1:
The patent modifies plasma spray parameters including increased power density (40-100 kW), adjusted gas flow rates, and optimized particle size distribution, which collectively reduce micron-scale defects and porosity while maintaining coating uniformity
Solution Approach 2:
The substrate is preheated before deposition, which reduces thermal shock and minimizes defect formation during the spraying process, resulting in a more uniform coating with fewer micron-scale imperfections
3Reliability
If larger particles are used, then sintering rate and shrinkage are reduced, but coating thickness control becomes more difficult
Solution Approach 1:
The patent employs dynamic control of spray parameters including adjustable power density, gas flow rates, and particle size distribution during the deposition process, which enables precise control of coating thickness while maintaining the benefits of larger particles
Solution Approach 2:
The patent optimizes the particle size distribution parameters to include a higher proportion of larger particles (10-50 microns) while controlling the overall feed rate and spray parameters to achieve desired coating thickness, balancing sintering stability with thickness control
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 process results in a ceramic coating with significantly reduced sintering shrinkage, minimized microcracking, and improved durability by reducing stress concentrations and maintaining neutral stress conditions at operating temperatures, enhancing the longevity of turbine engine components.
Implementation Method 1
electricity produces a plasma in a flowing gas that generates a jet of heated and ionized gas into which a powder feedstock is injected, heated, and propelled
Implementation Method 2
the powder feed stock can transfer less porosity to the coating by being fully melted during deposition
Implementation Method 3
When the fully molten particles impinge on the surface of the substrate, they flatten out, solidify, and stick to the surface
Implementation Method 4
When the fully molten particles impinge on the surface of the substrate, they flatten out, solidify, and stick to the surface
Implementation Method 5
Depositing the molten droplets onto a preheated surface: (a) reduces defects by reducing the amount of adsorbed gas that is driven off of the surface during deposition
Implementation Method 6
Sintering shrinkage causes planar tensile stresses which cause the cracking. Sintering shrinkage as a function of time shows rapid initial densification that is associated with the elimination of the smallest porosity and microstructural defects
Data Source
Figure 1
AI summary
A process for forming a ceramic coating on a substrate, such as a turbine engine component includes the steps of providing a substrate, creating a plasma which preheats the substrate, and forming a ceramic coating by injecting a powder feedstock into the plasma. The ceramic coating forming step comprises depositing ceramic particles having a mean size in the range of from 100 to 150 microns at constant particle morphology.