Environmental Barrier Coating Surface Roughness Reduction
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Solution Overview
Problem
Current environmental barrier coating (EBC) methods, such as plasma spray, often result in surface roughness greater than 200 microinch (5.08 μm) Ra, which is undesirable for aerodynamic design in advanced turbine engines.
Innovation Solution
A method involving the application of an outer layer repair slurry comprising water, a primary outer material (BSAS), and a sintering aid like rare earth nitrate or ammonium phosphate, followed by drying and sintering, to improve the surface roughness of plasma sprayed EBCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma spray process is used to apply EBC, then the coating can be applied efficiently, but the surface roughness becomes greater than 200 microinch (5.08 μm) Ra which is undesirable
Solution Approach 1:
The invention applies a suspension coating containing vitreous-melting substance before final sintering to pre-smooth the rough plasma-sprayed surface. This preliminary action creates a glassy layer that fills surface irregularities, enabling subsequent reduction of surface roughness to below 200 microinch Ra while maintaining the efficiency of plasma spray application.
Solution Approach 2:
The invention changes the physical and chemical parameters of the coating surface by introducing vitreous-melting substances (such as borosilicate glass, boron carbide, or silicon carbide) that melt and form a smooth glassy phase during controlled heating. This parameter change transforms the rough ceramic surface into a smooth composite surface with reduced roughness.
2Ease of manufacture
If standard plasma spray coating is applied, then the process is simple and fast, but the surface roughness exceeds acceptable limits for aerodynamic design
Solution Approach 1:
The invention adds a preliminary suspension coating step that applies a smoothing layer containing vitreous-melting substances over the plasma-sprayed surface. This preliminary action maintains process simplicity by using straightforward coating methods while enabling subsequent surface smoothing through controlled heating to melt the glassy phase and reduce roughness.
Solution Approach 2:
The invention creates a composite coating structure combining the original plasma-sprayed ceramic material with vitreous-melting substances (glass phases). This composite material approach allows the coating to maintain its protective ceramic properties while the glassy phase fills surface voids and irregularities, achieving smooth surfaces suitable for aerodynamic applications.
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
This approach reduces surface roughness to between 40 microinch (1.02 μm) Ra and 150 microinch (3.8 μm) Ra, providing a more aerodynamic and durable coating while maintaining a hermetic seal against high temperature steam.
Implementation Method 1
sintering the component to produce a component having an improved surface roughness
Implementation Method 2
application of a suspension of inorganic, vitreous-melting substance mixture and local heating thereof
Implementation Method 3
drying the environmental barrier coating having the applied outer layer repair slurry
Data Source
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AI summary
A method for improving surface roughness of an environmental barrier coating comprising: providing a component (10) having a plasma sprayed environmental barrier coating; applying an outer layer repair slurry to the environmental barrier coating of the component; drying the environmental barrier coating having the applied outer layer repair slurry; and sintering the component to produce a component having an improved surface roughness wherein the outer layer repair slurry comprises: water; a primary outer material comprising BSAS; and a slurry sintering aid selected from the group consisting of rare earth nitrate, rare earth acetate, rare earth chloride, rare earth oxide, ammonium phosphate, phosphoric acid, polyvinyl phosphonic acid, and combinations thereof.