Single Layer Bond Coat for Gas Turbine Substrates
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Solution Overview
Problem
Conventional bi-layer bond coats for gas turbine components are time-consuming and costly due to the need for separate processes and equipment, with the coarse powder layer being unsuitable as a protective coating system and prone to oxidation damage, while the fine powder layer lacks adequate adhesion for ceramic materials.
Innovation Solution
A single layer bond coat is applied using a homogeneous powder composition with a specific particle size distribution, applied via HVOF process, achieving comparable properties to bi-layer coats, including surface roughness, density, and tensile strength, and optionally followed by a ceramic thermal barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bi-layer bond coat is applied with separate fine and coarse powder layers, then the protective properties and adhesion are improved, but the process complexity and time consumption increase
Solution Approach 1:
The patent combines the fine powder layer and coarse powder layer into a single homogeneous powder composition with a specific particle size distribution (10-100 μm). This single layer achieves both the protective properties of the fine layer and the adhesion benefits of the coarse layer, eliminating the need for separate deposition processes and equipment configurations.
Solution Approach 2:
The single layer bond coat performs multiple functions simultaneously: it provides oxidation and corrosion protection like the fine powder layer, creates adequate surface roughness for ceramic adhesion like the coarse powder layer, and maintains density and mechanical properties. This universal layer replaces the specialized functions of two separate layers.
2Reliability
If a coarse powder layer is deposited to achieve surface roughness for ceramic adhesion, then adhesion is improved, but the protective properties deteriorate due to porosity and oxidation susceptibility
Solution Approach 1:
The single layer bond coat has non-uniform particle size distribution within the layer, creating local variations in density and roughness. The finer particles (10-30 μm) provide dense protective regions, while coarser particles (40-100 μm) create surface roughness for adhesion, with both present throughout the layer rather than in separate layers.
Solution Approach 2:
The bond coat uses a composite powder composition containing particles of different sizes (10-100 μm range) within a single layer. This composite structure provides both the density and protection of fine particles and the surface roughness and adhesion of coarse particles, eliminating the need for separate layers with conflicting properties.
3Object-affected harmful factors
If a fine powder layer is deposited to provide oxidation protection, then protective properties are improved, but the surface roughness is insufficient for adequate ceramic adhesion
Solution Approach 1:
The single layer bond coat has non-uniform particle size distribution within the layer, creating local variations in density and roughness. The finer particles (10-30 μm) provide dense protective regions, while coarser particles (40-100 μm) create surface roughness for adhesion, with both present throughout the layer rather than in separate layers.
4Manufacturing precision
If separate HVOF and APS processes are used for bi-layer bond coat deposition, then the desired properties are achieved, but the equipment requirements and inventory complexity increase
Solution Approach 1:
The patent combines the fine powder layer and coarse powder layer into a single homogeneous powder composition with a specific particle size distribution (10-100 μm). This single layer achieves both the protective properties of the fine layer and the adhesion benefits of the coarse layer, eliminating the need for separate deposition processes and equipment configurations.
Solution Approach 2:
The single layer bond coat performs multiple functions simultaneously: it provides oxidation and corrosion protection like the fine powder layer, creates adequate surface roughness for ceramic adhesion like the coarse powder layer, and maintains density and mechanical properties. This universal layer replaces the specialized functions of two separate layers.
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 single layer bond coat provides improved adhesion and durability, reducing oxidation and increasing the effective life of thermal barrier coatings by maintaining mechanical properties and thermal insulation, while simplifying the application process and reducing material inventory.
Implementation Method 1
The bond coat is applied in a thermal spray process, for example a high velocity oxy-fuel (HVOF) process
Implementation Method 2
high velocity oxy-fuel (HVOF) spray processes
Implementation Method 3
thermal barrier coating (TBC) systems formed on the exposed surfaces of high temperature components have found wide use
Implementation Method 4
The bond coat is typically formed from an oxidation-resistant aluminum-containing alloy to promote adhesion of the ceramic layer to the component
Implementation Method 5
the bond coat having oxidation resistance, adequate surface roughness, and density
Data Source
AI summary
A protective coating system for metal components includes a superalloy metal substrate, such as a component of a gas turbine. A single layer bond coat is applied to the superalloy metal substrate in a thermal spray process from a homogeneous powder composition having a particle size distribution wherein about 90% of the particles by volume are within a range of about 10 μm to about 100 μm. The percentage of particles within any 10 μm band within the range does not exceed about 20% by volume, and the percentage of particles within any two adjacent 10 μm bands within the range does not deviate by more than about 8% by volume.