Ceramic Coating CMAS Infiltration Resistance via Particle Size Control
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Solution Overview
Problem
Current anti-CMAS coatings for gas turbines face challenges in resisting infiltration and degradation from contaminants like CMAS at high temperatures, leading to issues such as stiffening, cracking, and delamination, especially when using SPS processes which can result in points of infiltration and poor mechanical properties.
Innovation Solution
A method involving the plasma projection technique using a suspension with ceramic compounds where at least 90% of the solid particles have a diameter less than 15 µm and at least 50% have a diameter greater than or equal to 1 µm, forming a lamellar microstructure with a tortuous porous network to slow down CMAS infiltration, using materials like rare earth zirconates or composite materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If SPS process is used to apply anti-CMAS coating, then thermal insulation properties are improved, but infiltration resistance deteriorates due to formation of points of infiltration
Solution Approach 1:
The patent changes the particle size parameters of the ceramic suspension from conventional fine particles to a specific distribution where at least 90% of particles have diameter less than 15 µm and at least 50% have diameter greater than or equal to 1 µm. This parameter change in particle size distribution modifies the coating microstructure to eliminate infiltration points while preserving thermal insulation properties through the resulting lamellar structure with controlled porosity.
Solution Approach 2:
The patent uses composite ceramic materials comprising multiple phases or compositions in the suspension, such as combinations of yttria-stabilized zirconia with other ceramic compounds. This composite approach creates a multi-phase coating structure that simultaneously provides thermal insulation and resistance to CMAS infiltration by forming stable reaction products at the coating-contaminant interface.
2Manufacturing precision
If fine particles are used in SPS suspension, then coating uniformity is improved, but mechanical properties deteriorate
Solution Approach 1:
The patent optimizes the particle size distribution parameters within a specific range (90% less than 15 µm, 50% greater than or equal to 1 µm) to achieve a balance between coating uniformity and mechanical strength. This controlled particle size distribution ensures sufficient fineness for uniform coating application while maintaining adequate particle strength and interparticle bonding for mechanical integrity.
3Reliability
If particle size is reduced to prevent infiltration, then infiltration resistance is improved, but vent hole functionality deteriorates due to obstruction
Solution Approach 1:
The patent establishes an optimal particle size range where particles are fine enough to provide infiltration resistance through tortuous paths but not so fine as to obstruct vent holes. The specification that at least 90% of particles are less than 15 µm while at least 50% are greater than or equal to 1 µm creates a size distribution that filters CMAS contaminants while allowing vent hole passage.
Solution Approach 2:
The patent utilizes the inherent porosity of plasma-sprayed coatings created by the lamellar microstructure of deposited particles. This porous structure provides tortuous paths that resist CMAS infiltration while maintaining open vent holes for thermal stress relief and manufacturing purposes, as the porosity is formed by the spray deposition process itself rather than by filling with fine particles.
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 method effectively creates a ceramic layer with increased resistance to CMAS infiltration and mechanical erosion while maintaining vent hole functionality, forming stable phases that block CMAS deep within the coating, enhancing the durability and performance of thermal and environmental barrier systems.
Implementation Method 1
a plasma spraying technique of suspensions 'SPS' in which at least one suspension of solid particles of at least one ceramic compound is injected into a plasma jet
Implementation Method 2
forming a lamellar microstructure with a tortuous porous network to slow down CMAS infiltration
Implementation Method 3
the ceramic compound is chosen from the compounds called anti-CMAS compounds... forming stable phases that block CMAS deep within the coating
Data Source
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AI summary
The invention relates to a method for coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound by a suspension plasma spraying (SPS) technique, in which at least one suspension of solid particles of at least one ceramic compound is injected into a plasma jet, and then the thermal jet that contains the solid particle suspension is sprayed onto the surface of the substrate, by means of which the layer comprising at least one ceramic compound is formed on the surface of the substrate; method characterised in that, in the suspension, at least 90 vol% of the solid particles have a larger dimension (referred to as d90), such as a diameter, smaller than 15 µm, preferably smaller than 10 µm, and at least 50 vol% of the solid particles have a larger dimension, such as a diameter (referred to as d50), no smaller than 1 µm. The invention also relates to a substrate coated with at least one layer that can be obtained by said method. The invention also relates to a part comprising said coated substrate. The invention further relates to the use of said layer in order to protect a solid substrate against degradations caused by contaminants such as CMAS.