Turbine Component Weld-Brazing to Minimize Repair Cracking
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Solution Overview
Problem
Current methods for repairing gas turbine components with hard-to-weld materials are costly and time-consuming, and traditional welding or brazing can cause thermal stress and residual stress issues, leading to defects like hot cracking or strain age cracking.
Innovation Solution
A weld-brazing technique involving a plate with an easy-to-weld material over a recessed portion of the gas turbine component, where a braze material is placed between the recessed surface and the plate's inner surface, and a filler material is applied to the plate's outer surface to heat the braze material to the brazing temperature, bonding it to both the plate and the component without the need for specialized equipment like furnaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If welding processes are used directly to repair defects in hard-to-weld materials, then the repair can be performed, but thermal stress and residual stress are generated leading to hot cracking or strain age cracking
Solution Approach 1:
The repair process is segmented into two distinct stages: first brazing the plate to the component at lower temperature, then welding the filler material to the plate. This segmentation allows each joining method to operate under optimal conditions, avoiding the harmful effects of direct high-temperature welding on the hard-to-weld component material.
Solution Approach 2:
The plate made of easier-to-weld material serves as an intermediary between the hard-to-weld component and the welding process. The plate absorbs the thermal stress and acts as a buffer, preventing stress transmission to the component that would cause cracking.
2Reliability
If brazing is used with a vacuum furnace, then the braze material can be heated to bonding temperature, but the furnace has limited space and extensive heating times
Solution Approach 1:
The brazing operation is extracted from the vacuum furnace environment and performed in situ on the component. The plate is brazed directly to the component using localized heating, eliminating the need for extensive furnace heating cycles and reducing overall repair time.
Solution Approach 2:
The braze material is pre-positioned between the plate and component before the heating process begins. This preliminary preparation allows the brazing to proceed efficiently once heating starts, without requiring additional setup time in the furnace.
3Reliability
If vacuum furnaces are used for brazing, then the braze material can be heated, but extensive heating times and subsequent heat treatment are required increasing cost and time
Solution Approach 1:
The heating process is made dynamic and localized rather than static and global. Heating is applied locally to the brazing joint area using the filler material as a heat source, allowing rapid heating and cooling cycles that eliminate the need for prolonged furnace exposure and subsequent heat treatment.
Solution Approach 2:
The filler material serves a dual function: it provides the necessary heat for brazing through its application process, and it acts as a thermal insulator during cooling to control the thermal cycle. This self-service approach eliminates the need for external furnace equipment and subsequent heat treatment operations.
4Ease of manufacture
If non-uniform heating and cooling during welding occurs, then the welding process can be completed, but thermal stress and residual stress are generated
Solution Approach 1:
The thermal process is segmented into distinct phases: brazing at lower temperature followed by welding at higher temperature. Each phase is localized to specific areas, allowing controlled heat distribution that minimizes thermal stress accumulation in the hard-to-weld component material.
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 reduces repair costs and time, eliminates the need for subsequent heat treatment, and effectively repairs load-bearing components with hard-to-weld materials while minimizing thermal stress, providing improved mechanical properties.
Implementation Method 1
Application of the filler material to the outer surface of the plate is configured to heat the braze material to the brazing temperature
Implementation Method 2
The braze material is configured to bond the recessed surface of the recessed portion with the inner surface of the plate when the braze material is heated to a brazing temperature
Data Source
AI summary
A method includes positioning a braze material along a defect of a component of a turbine system, positioning a cover over the braze material, and focusing a heat source on the cover to melt the braze material along the defect.