Abradable Coating Surface Roughness Reduction
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Solution Overview
Problem
Existing abradable coatings for turbomachines have surface roughness issues that lead to reduced aerodynamic performance and increased specific fuel consumption due to high Ra values (up to 12 μm), which are not adequately addressed by current materials like MCrAlY alloys.
Innovation Solution
A porous abradable coating with a smooth surface roughness (Ra < 6 μm) is achieved by using ceramic grains with small particle sizes, such as alumina, zirconia, or mullite, which are bonded through partial sintering at low temperatures, filling surface porosities without machining, and applied using a slip with a dispersing agent and organic binder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermal powder spraying technique is used to form an abradable coating, then the coating can withstand high temperatures up to 1200°C, but the surface roughness becomes relatively high (Ra=12 μm) which reduces aerodynamic performance
Solution Approach 1:
The invention changes the particle size parameter of the ceramic powder from conventional larger sizes to specifically small sizes (0.1-15 μm). This parameter change allows the powder to fill surface porosities effectively while maintaining the porous structure for abradability. The small particle size enables the coating to achieve low surface roughness (Ra < 6 μm) while preserving temperature resistance up to 1200°C through the MCrAlY alloy base material.
Solution Approach 2:
The invention creates a composite coating structure combining MCrAlY alloy matrix with dispersed ceramic grains (alumina, zirconia, mullite). This composite approach allows the metal matrix to provide temperature resistance and ductility, while the fine ceramic grains fill surface porosities to reduce roughness. The composite structure maintains both thermal stability and aerodynamic performance.
2Manufacturing precision
If the surface roughness of the abradable coating is reduced to improve aerodynamic performance, then specific fuel consumption decreases, but the coating may lose its abradable properties or become too fragile
Solution Approach 1:
The invention applies local quality by creating a coating with non-uniform ceramic grain distribution. The ceramic grains are concentrated in the surface region where they fill porosities to reduce roughness (Ra < 6 μm), while the underlying structure maintains the porous architecture necessary for abradability. This local concentration of ceramic material at the surface provides smoothness without compromising the bulk material's ability to deform and wear appropriately during operation.
Solution Approach 2:
The invention maintains a porous coating structure with controlled porosity (30-70%) throughout the coating thickness. The small ceramic grains (0.1-15 μm) fill the surface porosities to reduce roughness, but the internal porous structure is preserved to enable abradable behavior. The porosity allows the coating to deform and wear smoothly during rotor-stator contact while the fine surface grains provide the desired low roughness (Ra < 6 μm).
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 solution results in a coating with a smooth surface roughness of Ra < 1 μm, reducing specific fuel consumption by 0.4% compared to prior art, while maintaining temperature resistance up to 1200°C and avoiding abrasive or fragile behavior.
Implementation Method 1
les grains céramiques, formant le matériau de remplissage, pénètrent dans le matériau abradable et sont liés par frittage partiel
Implementation Method 2
applied using a slip with a dispersing agent and organic binder
Data Source
Figure 1~2
AI summary
The present invention relates to an abradable coating for a turbine engine part, characterized by the fact that said coating includes a layer made of an abradable material, the surface asperities of which are filled with thermally bonded ceramic grains, forming a smooth, free surface having a low roughness.