Gas Turbine Blade Repair Using Dual-Material Overlay Welding
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Solution Overview
Problem
Brazing repair methods for gas turbine blades often result in insufficient strength, leading to the potential reoccurrence of cracks due to the low strength of brazing materials.
Innovation Solution
A blade repair method involving the formation of a notched portion with distinct regions, where the first region is filled with a welding material of higher weldability and the second region, closer to the end surface, is filled with a material of higher high-temperature strength, using overlay welding techniques to suppress crack generation during operation and welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If brazing repair is performed using brazing material, then the repair process can be completed, but the strength of the repaired portion is insufficient and cracks may occur again
Solution Approach 1:
The notched portion is divided into a first region and a second region, with each region filled with different welding materials having different properties. The first region uses material with high weldability to prevent welding cracks, while the second region uses material with high high-temperature strength to prevent operational cracks.
Solution Approach 2:
Different regions of the notched portion are assigned different material qualities based on their functional requirements. The first region (deeper portion) requires high weldability, while the second region (shallower portion) requires high high-temperature strength, creating local optimization of material properties.
2Reliability
If welding material with high high-temperature strength is used, then crack resistance during operation is improved, but weldability decreases and cracks may occur during welding work
Solution Approach 1:
The welding material selection is segmented by region: the first region uses material optimized for weldability (lower susceptibility to welding cracks), while the second region uses material optimized for high-temperature strength (lower susceptibility to operational cracks).
Solution Approach 2:
Each region of the notched portion receives material with locally optimized properties. The first region gets high-weldability material, and the second region gets high high-temperature strength material, matching material properties to functional requirements of each location.
3Device complexity
If a single welding material is used for the entire notched portion, then the repair process is simplified, but it is impossible to simultaneously achieve high weldability and high high-temperature strength
Solution Approach 1:
The notched portion is segmented into two regions that are filled with different welding materials in sequence. This segmentation allows the repair process to achieve both high weldability (in the first region) and high high-temperature strength (in the second region), which cannot be achieved with a single material.
Solution Approach 2:
The repair structure becomes a composite of two different welding materials, each contributing its superior properties. The first welding material provides excellent weldability, while the second welding material provides superior high-temperature strength, creating a composite repair structure with balanced performance.
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 method effectively prevents the reoccurrence of cracks in the repaired portion by leveraging materials with optimal weldability and high-temperature strength, ensuring structural integrity during gas turbine operation and welding processes.
Implementation Method 1
filling the first region with a first welding material by overlay welding using the first welding material; and filling the second region with a second welding material by overlay welding using the second welding material
Data Source
AI summary
This blade repair method has: a first welding step in which overlay welding in which a first welding material is used is performed to form a notched part and a bury a first region positioned on a blade-body side with a first welding material; and a second welding step in which, after the first welding step, overlay welding in which a second welding material is used is performed to form a notched part and bury a second region positioned on a front-surface side of a platform with the second welding material. The high-temperature strength of the second welding material is higher than the high-temperature strength of the first welding material, the weldability of the first welding material is higher than the weldability of the second welding material, and the second region is located in a range from 1.0 mm to 3.0 mm (inclusive) from the front surface of the platform toward the blade body.