Braze Joint Gap Control via Microstructural Elements
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Solution Overview
Problem
In industrial gas turbines, the brazing or soldering process for connecting turbine blade sections to base members is prone to quality deviations and reproducibility issues due to thermal and mechanical stress, as well as differences in heat capacity and grain size, leading to inconsistent braze joint gaps and mechanical properties.
Innovation Solution
The method involves adding microstructural elements to the connecting surfaces of the parts to be joined, using electro-chemical machining (ECM) or precise electro-chemical machining (PECM) to create corresponding features on the opposing surfaces, ensuring precise alignment and minimizing relative movement during the brazing or soldering process, thereby achieving a consistent braze joint gap and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional brazing or soldering is used to connect turbine blade sections to base members, then the joining process can be performed in batch mode with relatively simple equipment, but quality deviations and reproducibility issues occur due to thermal and mechanical stress, differences in heat capacity, and relative movement during heating and cooling
Solution Approach 1:
The patent applies preliminary action by creating microstructural elements (protrusions and recesses) on the connecting surfaces before the brazing process. These elements are formed through ECM/PECM machining or additive manufacturing, ensuring that the braze joint gap maintains a predetermined uniform width throughout the heating and cooling phases, thereby preventing quality deviations caused by thermal expansion and relative movement.
Solution Approach 2:
The patent implements local quality by introducing microstructural elements with specific geometries (protrusions and recesses) at the connecting surfaces. These localized features ensure that the braze joint gap width remains consistent in critical areas, addressing the uniformity problem locally without requiring complete redesign of the entire joining process.
2Adaptability or versatility
If generative manufacturing methods such as 3D printing are used to create replacement coupons, then production flexibility and customization are improved, but quality variance increases due to differences in grain size of metallic powder and non-optimum braze alloy distribution
Solution Approach 1:
The patent addresses the quality consistency issue by introducing microstructural elements with controlled geometries on the connecting surfaces of generatively manufactured parts. These localized features ensure uniform braze joint gap width, compensating for the inherent variability in additive manufacturing processes and ensuring consistent braze alloy distribution.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the dimensions and geometries of microstructural elements through ECM/PECM machining or additive manufacturing parameters. By adjusting these parameters, the braze joint gap width is maintained within tight tolerances, overcoming the quality variance associated with generative manufacturing.
3Strength
If welding is used to join turbine blade sections to base members, then single-piece construction is achieved, but the process is unsuited for thin-walled and extended sections and significantly increases production time compared to batch brazing
Solution Approach 1:
The patent applies preliminary action by creating microstructural elements on the connecting surfaces before joining. This preparation enables brazing to achieve joint strength comparable to welding, while maintaining the productivity advantage of batch processing for thin-walled and extended sections.
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 results in a high-quality, reproducible braze joint with enhanced mechanical properties, reduced risk of residual stress and void formation, and improved fatigue lifetime by ensuring precise fit and isothermal solidification, making it suitable for thermally and mechanically loaded areas in industrial gas turbines.
Implementation Method 1
electro-chemically machining (ECM) or precise electro-chemically machining (PECM) a second connecting surface of the second part by polarizing the first part as a cathode and the second part as an anode
Implementation Method 2
relative movement between the coupon and the base section of the IGT part during the heating up and cooling down phase of the brazing process due to the fact that the areas to be connected have different heat capacities
Data Source
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AI summary
Method for manufacturing a braze joint gap for connecting a first part to a second part via brazing or soldering, comprising the steps of: adding microstructural elements to a first connecting surface of the first part to be connected to the second part via brazing or soldering; aligning the second part and the first part or an electrode part having a tool contour, which is identical to the contour of the first connecting surface; electro-chemically machining (ECM) or precise electro-chemically machining (PECM) a second connecting surface of the second part by polarizing the first part or the electrode part as a cathode and the second part as an anode.