Integrally Bladed Rotor Forging Fatigue Strength via Linear Friction Welding
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Solution Overview
Problem
Conventional methods for manufacturing integrally bladed rotors, particularly those made from titanium alloys, face challenges in enhancing fatigue and tensile properties, which are critical for high-performance applications like gas turbine engines.
Innovation Solution
The method involves solution heat treating, water quenching, and aging a stub-containing rotor hub forging, followed by linear friction welding of airfoils onto stubs, with concurrent stress relieving within a predefined area to maintain specific temperature constraints, optimizing mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional solution heat treating and quenching is used, then basic mechanical properties are achieved, but fatigue and tensile properties are insufficient for high-performance applications
Solution Approach 1:
The patent applies parameter changes by implementing a multi-stage heat treatment process with specific temperature and time parameters: solution heat treating at 900-950°F for 1-4 hours, aging at 1000-1100°F for 4-8 hours, and stress relieving at 150-250°F for 1-4 hours. These precisely controlled parameter changes transform the material properties to achieve both high fatigue strength and performance reliability simultaneously.
Solution Approach 2:
The patent applies preliminary action by performing solution heat treating and aging operations on the rotor hub forging before the linear friction welding process. This preliminary heat treatment establishes the base mechanical properties and microstructure in the hub and stubs, which then guides the subsequent welding and stress relieving operations to achieve the final enhanced fatigue strength and reliability.
2Productivity
If linear friction welding is used to join airfoils to stubs, then manufacturing efficiency is improved, but residual stresses and distortion are introduced
Solution Approach 1:
The patent applies the taking out principle by extracting and separately treating the residual stress problem through a dedicated stress relieving operation. After linear friction welding introduces residual stresses, the patent implements a specific stress relieving heat treatment at 150-250°F for 1-4 hours that targets and removes these unwanted stresses without compromising the welding efficiency or joint strength.
3Stress or pressure
If hub inner diameter is heated during stress relieving, then weld stresses are reduced, but material properties near the flow path may be compromised
Solution Approach 1:
The patent applies local quality by implementing spatially differentiated temperature control during stress relieving. The hub inner diameter region is maintained below 1000°F to preserve material strength near the flow path, while other regions of the rotor hub forging are heated to 150-250°F for stress relief. This localized temperature differentiation allows stress reduction in critical areas without compromising the material properties where high strength is required.
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 significantly enhances high cycle fatigue strength by up to 30% and tensile strength by 15%, enabling improved performance or reduced weight for existing designs.
Implementation Method 1
solution heat treating a stub-containing rotor hub forging
Implementation Method 2
water quenching the solution heat treated stub-containing rotor hub forging
Implementation Method 3
aging the water quenched stub-containing rotor hub forging
Implementation Method 4
linear friction welding airfoils onto each of a multiple of stubs
Implementation Method 5
concurrently stress relieving the linear friction welds
Data Source
AI summary
A method for producing an enhanced property integrally bladed rotor includes solution heat treating a stub-containing rotor hub forging; water quenching the solution heat treated stub-containing rotor hub; aging the water quenched stub-containing rotor hub forging; linear friction welding airfoils onto each of a multiple of stubs of the stub-containing rotor hub forging; and concurrently stress relieving the linear friction welds of each of the multiple of stubs within a predefined area while ensuring that a hub inner diameter does not exceed a predetermined temperature.