Pre-Sintered Abrasive Blade Tip Cap for Single-Crystal Turbine Blades
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Solution Overview
Problem
Existing methods for attaching abrasive tip caps to single crystal turbine rotor blades in gas turbines are unsuitable as they risk degrading the blade's microstructure and cannot withstand high temperatures without recrystallization, leading to diminished performance.
Innovation Solution
A pre-sintered abrasive material preform composed of a superalloy base material and braze alloy powders is coupled to the blade tip through a single heating and cooling cycle, using vacuum brazing to preserve the microstructure and ensure high-temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing methods for attaching abrasive tip caps are used, then abrasive properties are provided, but the single crystal microstructure of the blade is degraded and high-temperature stability is lost
Solution Approach 1:
The invention changes the temperature parameter of the attachment process by using a low-temperature braze alloy (melting point 900-1100°C) instead of high-temperature joining methods. This parameter change allows the abrasive tip cap to be attached without exceeding the recrystallization temperature of the single crystal blade material, thus preserving the microstructure while providing abrasive properties
Solution Approach 2:
The invention introduces a braze alloy as an intermediary material between the abrasive tip cap and the blade. This intermediary layer enables the attachment of the abrasive cap at lower temperatures that do not degrade the single crystal microstructure, while still providing strong bonding and maintaining abrasive functionality
2Strength
If high temperatures are used to attach abrasive material, then strong bonding is achieved, but the blade material recrystallizes and performance diminishes
Solution Approach 1:
The invention changes the temperature parameter by selecting a braze alloy with a melting point (900-1100°C) significantly lower than the recrystallization temperature of single crystal nickel-based superalloys. This allows strong bonding to be achieved through brazing at temperatures that preserve the blade's microstructure and high-temperature performance
3Productivity
If abrasive material is applied to blade tip, then tip clearance is reduced and efficiency increases, but the blade becomes vulnerable to high-temperature damage
Solution Approach 1:
The invention creates a composite structure consisting of the single crystal blade base material and an abrasive tip cap attached via low-temperature brazing. This composite structure allows the blade to achieve reduced tip clearance and increased efficiency through the abrasive cap, while the low-temperature attachment process ensures the base material maintains its high-temperature stability and reliability
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 maintains the integrity of the single crystal microstructure while providing effective abrasive properties, ensuring durability and efficiency at high temperatures.
Implementation Method 1
a pre-sintered abrasive material preform composed of a superalloy base material and braze alloy powders is coupled to the blade tip through a single heating and cooling cycle
Implementation Method 2
using vacuum brazing to preserve the microstructure and ensure high-temperature stability
Data Source
Figure 1~2
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AI summary
The disclosure concerns an abrasive gas turbine blade tip cap preform (11) for bonding to a blade tip to form an abrasive blade tip cap, the abrasive gas turbine blade tip cap preform (11) being formed of a bonding layer (12) and an abrasive layer (13), the bonding layer (12) being a metallic layer comprising powder size particles of a nickel braze alloy and a nickel base superalloy, and the abrasive layer (13) being a ceramic layer in a metal matrix comprising powder size particles of cubic boron nitride (cBN) and aluminum oxide (AI2O3) in a metal matrix of same composition of the bonding layer (12). The disclosure also concerns a method of manufacturing an abrasive gas turbine blade tip cap preform (11 ) and a method of bonding the abrasive gas turbine blade tip cap preform (11 ) to a blade tip to form an abrasive blade tip cap.