Abrasive Preforms for Gas Turbine Blade Tip Brazing
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Solution Overview
Problem
Existing methods for applying abrasive coatings to gas turbine blade tips often fail to achieve optimal clearance and efficiency due to inadequate bonding and environmental protection, leading to suboptimal performance and wear issues.
Innovation Solution
A pre-formed abrasive coating comprising a sintered mixture of low and high melting point alloys with embedded cubic boron nitride abrasive, which is applied to the blade tip surface and brazed using a self-braze material for secure bonding and environmental protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If direct plating or direct spraying methods are used to apply abrasive to blade tips, then the abrasive coating can be applied to the surface, but the bonding strength and environmental protection are inadequate leading to suboptimal performance and wear issues
Solution Approach 1:
The patent uses a composite preform structure combining self-braze material (MCrAlY alloy) with embedded abrasive particles (CBN or SiC). This composite structure provides both strong bonding to the substrate and effective abrasive function, resolving the contradiction between bonding strength and performance reliability.
Solution Approach 2:
The abrasive and self-braze material are pre-formed into an integrated preform structure before application to the blade tip. This preliminary formation ensures proper bonding characteristics and abrasive distribution are established before the brazing process, improving both bonding strength and environmental protection.
2Reliability
If conventional abrasive coating methods are used, then the coating can be applied to blade tips, but oxidation and corrosion resistance are insufficient leading to reduced service life
Solution Approach 1:
The self-braze material matrix (MCrAlY alloy) provides oxidation and corrosion resistance while embedding protective abrasive particles. This composite structure simultaneously protects the blade tip from environmental degradation and maintains abrasive functionality, extending service life.
Solution Approach 2:
The self-braze material acts as an intermediary layer between the substrate and the abrasive particles, providing environmental protection while securing the abrasive in place. This intermediate layer prevents direct exposure of the substrate to oxidizing and corrosive environments.
3Reliability
If pre-formed abrasive preforms are used with self-braze material, then bonding strength and environmental protection are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The abrasive and self-braze material are pre-formed into an integrated preform structure before application. This preliminary formation simplifies the application process by combining multiple functions (bonding, abrasive, protection) into a single component that is applied in one step, reducing overall manufacturing complexity despite the sophisticated preform structure.
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 provides improved oxidation and corrosion resistance, extended service life, and reduced wear, resulting in enhanced efficiency and performance by maintaining low radial clearance between blade tips and the BOAS segments.
Implementation Method 1
a self-braze material comprising a sintered mixture of at least one first alloy of low melting point relative to the tip surface to which the preform is to be applied, and at least one second alloy of high melting point relative to the first alloy
Implementation Method 2
heating to cause the self-braze material to braze to the tip surface or an intervening component
Implementation Method 3
heating to cause the self-braze material to braze to the tip surface or an intervening component
Data Source
Figure 1~2
Figure 3
AI summary
A method for applying an abrasive (42) comprises: applying, to a substrate (24), the integral combination (20, 100, 120) of: a self-braze material (40); and an abrasive (42) embedded in the self-braze material; and securing the combination to the substrate.