Microwave Plasma Spheroidization of Recycled Metal Powder Feedstock
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Solution Overview
Problem
Conventional spheroidization methods for metal powders, such as thermal arc plasma and radio-frequency inductively coupled plasma, suffer from non-uniform temperature profiles, electrode degradation, and inefficient energy coupling, leading to non-uniform spheroidization and contamination, while methods like gas atomization and Hydride-Dehydride processes are complex and costly.
Innovation Solution
A method using microwave plasma processing to spheroidize metallic particles from scrap or used metal parts, involving milling to specific sizes and aspect ratios without embrittling, and applying microwave plasma to form spheroidized powders with controlled particle size distribution and uniform temperature profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal arc plasma is used for spheroidization, then high temperature melting is achieved, but electrode degradation occurs causing contamination and non-uniform temperature distribution
Solution Approach 1:
The patent removes the electrodes from the plasma generation system entirely, replacing them with an inductively coupled plasma source that generates plasma through electromagnetic induction in a gas stream, eliminating electrode degradation and contamination while maintaining high plasma temperatures for effective spheroidization
Solution Approach 2:
The patent replaces the mechanical/electrical arc-based plasma generation system with an electromagnetic induction-based plasma system, where radio frequency fields induce currents in the plasma gas to sustain high temperatures without physical electrodes, thereby eliminating contamination
2Shape
If thermal arc plasma with side injection is used, then powder melting occurs, but non-uniform temperature exposure results in inconsistent spheroidization
Solution Approach 1:
The patent segments the plasma processing zone into multiple regions with different temperature characteristics, allowing particles to experience staged heating and spheroidization, ensuring uniform exposure throughout the plasma cloud through controlled gas flow and particle injection patterns
Solution Approach 2:
The patent creates a more uniform temperature distribution throughout the plasma processing zone by using inductive coupling to generate plasma throughout the gas volume rather than concentrated at an arc point, ensuring all particles experience similar thermal conditions for consistent spheroidization
3Temperature
If radio-frequency inductively coupled plasma is used, then plasma generation occurs, but low coupling efficiency and non-uniform magnetic field result in temperature gradients
Solution Approach 1:
The patent optimizes plasma generation parameters including radio frequency power levels, gas composition and flow rates, and magnetic field strength to improve energy coupling efficiency, adjusting these parameters to achieve uniform plasma distribution and consistent spheroidization results
Solution Approach 2:
The patent implements process monitoring and control systems that measure plasma characteristics and adjust input parameters in real-time to maintain optimal energy coupling efficiency and uniform temperature distribution throughout the plasma processing zone
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
Produces spheroidized powders with consistent shape, porosity, and composition, suitable for additive manufacturing, while avoiding contamination and reducing process complexity and cost.
Implementation Method 1
applying microwave plasma to form spheroidized powders
Implementation Method 2
Surface tension of the melt pulls it into a spherical shape
Implementation Method 3
where it is melted by the high temperature of the plasma
Data Source
AI summary
Disclosed herein are embodiments of methods, devices, and assemblies for processing feedstock materials using microwave plasma processing. Specifically, the feedstock materials disclosed herein pertains to scrap materials, dehydrogenated or non-hydrogenated feed material, and recycled used powder. Microwave plasma processing can be used to spheroidize and remove contaminants. Advantageously, microwave plasma processed feedstock can be used in various applications such as additive manufacturing or powdered metallurgy (PM) applications that require high powder flowability.