Nickel-Based Diffusion Bonding Using SPS to Limit Interface Precipitates
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Solution Overview
Problem
Conventional diffusion welding of INCONEL 617 for compact heat exchangers results in limited grain boundary migration due to extensive precipitation at the bonding interface, leading to degraded elevated-temperature mechanical properties and microstructural discontinuities, which hinder the achievement of desired material properties.
Innovation Solution
A material joining process using spark plasma sintering (SPS) or electric-field-assisted sintering (EFAS) is employed, where a high current density is applied between adjacent nickel-based materials under pressure to form a bond, minimizing precipitate formation and promoting grain boundary migration, thereby achieving improved material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional hot pressing diffusion welding is used to join INCONEL 617 materials, then a bond is formed between the materials, but extensive precipitation at the bonding interface hinders grain boundary migration and degrades elevated-temperature mechanical properties
Solution Approach 1:
The patent applies spark plasma sintering with specific parameter combinations (current density, pressure, temperature, time) to achieve diffusion bonding without extensive precipitation. The process uses high current density (e.g., 100-1000 A/cm²), pressure (e.g., 5-50 MPa), and temperature (e.g., 1000-1200°C) for short durations (e.g., 5-60 minutes) to promote grain boundary migration while minimizing harmful precipitate formation at the interface.
2Productivity
If conventional hot pressing diffusion welding is used to join INCONEL 617 materials, then a bond is formed between the materials, but the process requires long periods of time and high energy consumption
Solution Approach 1:
The patent replaces conventional thermal conduction heating with direct electrical current heating through spark plasma sintering. The electrical energy is converted to heat directly at the bonding interface through resistive heating and spark discharge, enabling rapid heating and bonding in minutes rather than hours, significantly reducing both processing time and overall energy consumption.
3Reliability
If a nickel interlayer is used to bond INCONEL 617 plates, then bonding is achieved, but microstructural discontinuities and secondary phase particles are still seen at the interface
Solution Approach 1:
The patent eliminates the nickel interlayer entirely by using spark plasma sintering to achieve direct diffusion bonding between INCONEL 617 plates. The process conditions promote clean interface formation without the need for intermediate layers, resulting in microstructural continuity and absence of secondary phase particles at the bonding interface.
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 process results in a bond with enhanced creep, elevated-temperature fatigue, and creep-fatigue properties, comparable to or exceeding those of the wrought product form, while reducing energy usage and processing time, and minimizing porosity and precipitate formation at the interface.
Implementation Method 1
A first material and a second material are placed in a die of a direct current sintering apparatus. An electric current and pressure are applied to the first material and the second material
Implementation Method 2
Diffusion welding is a solid-state joining technique where atomic diffusion across contacting surfaces forms a bond between components. This is induced by high temperatures and pressures.
Data Source
AI summary
A method of forming an article comprises placing a first material and a second material in a die of a direct current sintering apparatus. The second material directly contacts the first material. An electric current and pressure are applied to the first material and the second material to form an article. An additional method comprises placing a nickel-based material in direct contact with one or more other nickel-based materials to form a stack of nickel-based materials. An electric current and pressure are applied to the stack of nickel-based materials to join the nickel-based material and the one or more other nickel-based materials. Related articles are also disclosed.