Structural Braze Alloy for Crack-Free Superalloy Repair
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Solution Overview
Problem
Superalloy materials are difficult to repair due to susceptibility to weld solidification cracking and strain age cracking, and existing braze materials with boron or silicon as melting point depressants reduce ductility and create deleterious phases, limiting their use in high-stress and high-temperature applications.
Innovation Solution
Development of boron and silicon-free braze alloys using titanium, zirconium, and hafnium as melting point depressants, which are formulated to have melting temperatures compatible with solution heat treatment of superalloys, ensuring mechanical strength and ductility similar to the substrate material, and are tailored for specific superalloy compositions like Rene 80 and IN 939.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional braze materials with boron or silicon as melting point depressants are used, then the braze joint can be formed at lower temperatures, but the ductility of the joint and repaired region is reduced and deleterious phases are created
Solution Approach 1:
The patent changes the chemical composition parameters of the braze alloy by replacing boron and silicon melting point depressants with aluminum and titanium. This parameter substitution maintains the melting point depression function while eliminating the formation of deleterious phases that reduce ductility, thereby resolving the contradiction between achieving low-temperature brazing and maintaining joint ductility.
Solution Approach 2:
The patent employs aluminum and titanium as consumable melting point depressants that are intentionally added to the braze alloy. These elements serve their purpose of lowering the melting temperature and then remain in the joint as harmless constituents, replacing the need for boron or silicon while avoiding the creation of brittle phases.
2Reliability
If braze materials are used to repair superalloy materials, then repair can be performed without weld solidification cracking and strain age cracking, but the mechanical strength and operating temperature are limited compared to weld joints
Solution Approach 1:
The patent creates a composite braze alloy system combining nickel, cobalt, aluminum, and titanium. This composite composition leverages the high-temperature stability of nickel/cobalt base with the melting point depression and strength enhancement from aluminum and titanium, achieving a balance between crack resistance and mechanical strength that allows structural repair applications.
Solution Approach 2:
The patent modifies the mechanical properties of the braze joint by adjusting the aluminum and titanium content within specific ranges (0.5-5.0 wt% Al, 0.1-3.0 wt% Ti). These parameter optimizations enhance the strength and ductility of the braze joint, enabling it to achieve up to 80% of the substrate material properties and qualify for structural repair in high-stress regions.
3Strength
If boron and silicon free braze alloys incorporating hafnium and/or zirconium are used, then mechanical properties up to 80% of base superalloy properties are achieved, but the complexity of alloy formulation increases
Solution Approach 1:
The patent extracts and eliminates rare and expensive elements (hafnium and zirconium) from the braze alloy formulation while maintaining the mechanical properties through substitution with more common and cost-effective aluminum and titanium. This extraction simplifies the alloy formulation and reduces material costs while preserving the 80% strength target.
Solution Approach 2:
The patent replaces expensive rare earth elements with more abundant and economical aluminum and titanium as the primary alloying elements. This substitution maintains the desired mechanical properties while significantly reducing the complexity and cost of alloy formulation and processing.
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 braze alloys provide structural repairs with mechanical strength up to 80% of the substrate material properties, suitable for high-stress regions, and do not introduce new elements into the superalloy substrate, allowing for crack-free repairs in gas turbine components.
Implementation Method 1
the braze material to melt, to flow into the discontinuities and to fill around the alloy particles
Implementation Method 2
boron and silicon free braze alloys incorporating hafnium and/or zirconium have been developed... titanium as a melting point depressant material
Data Source
AI summary
Boron and silicon free braze alloys are useful for structural repair of superalloy gas turbine engine components. The braze alloy compositions include nickel, chromium, titanium, and at least one of zirconium and hafnium. All of the above elements are metallic and form ductile bonds within and across the braze interface when compared to non-metallic bonds of boron and silicon.