Thin-Wall Blade Repair Paste for Crack-Free Diffusion Bonding
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Solution Overview
Problem
Existing repair methods for thin-wall defects in nickel-based superalloy blades of gas turbines, such as fusion welding and large-gap brazing, face challenges including poor weldability, deformation, and air passage blockage due to low-melting-point filler metals, making it difficult to effectively repair these components under high-temperature conditions.
Innovation Solution
An activator comprising specific percentages of elements like Cr, Co, Al, W, Ti, Ta, Mo, Ru, Hf, Zr, C, and Sc, in powder form, is used to create a pre-made paste and part that, when sintered and shaped, forms a repair area with a microstructure similar to the base material, avoiding high heat-induced cracking and air passage blockage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fusion welding repair is used, then the repair area can be joined, but the thin wall deforms due to high heat input
Solution Approach 1:
The invention changes the fundamental repair parameter from high-heat fusion welding to low-heat diffusion bonding. The activator powder reacts at 900-1100°C to form a metallurgical bond, compared to the >1500°C required for fusion welding. This parameter change in bonding temperature prevents thin wall deformation while achieving sufficient joint strength
Solution Approach 2:
The invention replaces the mechanical fusion welding process with a chemical diffusion bonding process. The activator powder facilitates atomic diffusion between the repair material and base metal at lower temperatures, substituting the high-heat mechanical fusion process that causes deformation
2Reliability
If large-gap brazing is used, then welding cracks are avoided, but low-melting-point brazing filler metal flows into the air passage causing blockage
Solution Approach 1:
The invention changes the filler metal melting point parameter from low (conventional brazing) to high (matching base metal). The activator-based diffusion bonding occurs at 900-1100°C, above the base metal melting point, ensuring the repair material and base metal fuse together without low-melting-point filler metal that would flow into air passages
Solution Approach 2:
The invention achieves homogeneous material composition in the repair area. The activator powder reacts with both the repair material and base metal to form a unified metallurgical bond with composition matching the base metal, eliminating the heterogeneous low-melting-point filler metal layer that causes air passage blockage
3Strength
If high heat input is applied, then the repair area achieves strong bonding, but the thin wall cracks due to thermal stress
Solution Approach 1:
The invention changes the bonding temperature parameter from high (fusion welding >1500°C) to moderate (diffusion bonding 900-1100°C). This moderate temperature parameter achieves sufficient bonding strength through diffusion while avoiding the thermal stress that causes cracking in thin walls
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 repair process maintains high mechanical strength and compatibility with high-temperature environments, preventing deformation and air passage blockage, thus effectively addressing the difficulties in repairing thin-wall defects in nickel-based superalloy blades.
Implementation Method 1
the pre-made paste is made into a pre-made part by using a mold... Place the pre-made paste in the ceramic mold and spread it evenly... then place the ceramic mold with the pre-made paste in a vacuum furnace with a vacuum degree better than 1×10^-3
Data Source
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AI summary
The present invention relates to the field of the repairing of high-temperature blades of gas turbines. Disclosed are an activating agent,prefabricated paste, prefabricated member and process for repairing thin-wall-penetrating defects.The activating agent at least comprises the following elements in percentage by mass: 7.1-9.8%of Cr,15.2-19.8%of Co,2.5-4.3%of Al,0.2-1.7%ofW, 6.2-8.7%of Ti, 5.6-7.8%of Ta,5.6-8.8%of Mo,2.7-4.2%of Ru,5.6-7.8%of Hf,0.07-0.15%of Zr, 0.10-0.15%of C,and 0.01-0.05%of Sc.The prefabricated paste is prepared by blending the activating agent,a curing agent and a binding agent.The prefabricated member is made of the prefabricated paste.The processcomprises the steps of polishing of a defect,forming of a prefabricated member,trimming of the prefabricated member,aditive-manufacturing-based repairing of the defect,and post-treatment.In the present invention,a repair area has a structure close to that of a substrate and can adapt to the high-temperature working environment of a blade,and the mechanical strength of ajoint is high;therefore,the cracking and deformation of the thin wall of the blade caused by a high heat input are effectively avoided,an air channel is prevented from being blocked,and the problem of a thin-wall-penetrating defect of a nickel-based high-temperature alloy blade being difficult to repair is solved.