Fan Blade Laser Cladding for Equiaxed Titanium Repair
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Solution Overview
Problem
Repairing titanium components in gas turbine engines, such as fan blades, is challenging due to the difficulty in producing weld clad layers with equiaxed grain microstructures, which are essential for matching material properties, as conventional methods often result in columnar microstructures with directional properties, leading to potential fractures under external forces.
Innovation Solution
A method involving laser spot deposition to form a weld clad layer with a substantially equiaxed grain microstructure by depositing multiple layers of titanium or titanium alloy spots, where each spot solidifies before the next is deposited, ensuring at least 70% of the area has an aspect ratio of 6 to 1 or less, thereby mimicking the substrate's material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional weld cladding is used to repair titanium components, then the repair process is simple and fast, but the resulting weld clad layer forms columnar microstructures with directional material properties that do not match the substrate
Solution Approach 1:
The continuous weld cladding process is segmented into discrete laser deposition spots arranged in patterns. Each spot is deposited and allowed to solidify independently before the next spot is deposited, breaking the continuous thermal field into discrete thermal cycles that prevent columnar grain formation and promote equiaxed microstructure.
Solution Approach 2:
The laser deposition process uses periodic pulsed energy input rather than continuous heating. The laser deposits energy in periodic pulses that create discrete molten spots which solidify between pulses, creating repeated thermal cycles that interrupt directional heat flow and promote equiaxed grain growth.
2Reliability
If weld cladding is used to repair fan blades, then the repair capability is provided, but the directional material properties of columnar microstructures may lead to fractures under external forces
Solution Approach 1:
The process changes the thermal parameters by using intermittent pulsed laser deposition with controlled spot spacing and deposition rates. This creates a thermal regime where each spot solidifies before the next is deposited, changing the heat flow pattern from continuous directional cooling to intermittent multi-directional cooling, which produces equiaxed grains with isotropic mechanical properties.
Solution Approach 2:
The process exploits phase transitions by controlling the melting and solidification cycles of each deposition spot. Each spot undergoes complete melting followed by controlled solidification before the next spot is deposited, ensuring that the phase transition occurs in isolation and promotes equiaxed grain formation rather than columnar growth.
3Manufacturing precision
If multiple layers of laser deposition spots are deposited to form equiaxed grain microstructure, then material properties are improved, but the deposition time and process complexity increase
Solution Approach 1:
The process uses multiple layers of deposition spots, applying more deposition cycles than a single continuous pass would require. However, by allowing partial solidification between spots and using overlapping patterns, the process achieves superior microstructure control while managing the increased time investment through efficient multi-layer construction.
Solution Approach 2:
The deposition process uses nested layering where subsequent layers are deposited over and between previous layers. The spots are arranged in patterns where outer spots may overlap or nest with inner spots from previous layers, creating a dense equiaxed grain structure through multiple nested cycles of deposition and solidification.
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 produces a weld clad layer with material properties equal in all directions, enhancing the durability and reducing the risk of fracture, as it effectively avoids columnar grain microstructures, thereby improving the repair of titanium components in aerospace applications.
Implementation Method 1
a laser spot deposition process is used to form a weld clad layer
Implementation Method 2
an energy source may be applied to liquefy a solid filler metal
Implementation Method 3
each spot solidifies before the next is deposited
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A weld clad layer having a substantially equiaxed grain microstructure may be formed by forming a repair area (304) in a substrate (201), by depositing a first layer of laser deposition spots (320) in the repair area (304), and depositing a second layer of laser deposition spots (320) over the first layer of laser deposition spots (320). The first layer of laser deposition spots (320) comprises a first laser deposition spot (320) and a second laser deposition spot (320) adjacent to the first laser deposition spot (320). The first laser deposition spot (320) solidifies prior to deposition of the second laser deposition spot (320). The first layer of laser deposition spots (320) comprises titanium or titanium alloy.