Plasma Transferred Wire Arc Thermal Spray Offset Stabilization
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Solution Overview
Problem
Existing plasma transferred wire arc (PTWA) thermal spray processes are prone to instabilities due to variations in secondary air flow, plasma gas pressure, wire feed rate, and electrode wear, leading to poorly atomized particles and non-uniform deposits.
Innovation Solution
The central axis of the consumable wire is offset relative to the axial centerline of the constricting orifice, and the plasma transferred wire arc apparatus is rotated in the same direction as the offset, stabilizing the plasma arc and improving the atomization of molten metal particles, which are then projected onto a target surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the plasma transferred wire arc process is operated at higher deposition rates, then productivity increases, but process stability deteriorates leading to poorly atomized particles and non-uniform deposits
Solution Approach 1:
The wire axis is deliberately offset asymmetrically from the plasma jet axis by 0.05-0.5mm. This asymmetric positioning creates a stable plasma arc attachment point on the wire surface, preventing wire tip wander and ensuring consistent atomization even at higher deposition rates, thereby resolving the contradiction between productivity and process stability
Solution Approach 2:
The invention changes the spatial parameter of wire positioning by introducing a controlled offset distance (0.05-0.5mm) between the wire axis and plasma jet axis. This parameter change stabilizes the plasma arc attachment and improves atomization consistency, allowing higher deposition rates without sacrificing process reliability
2Device complexity
If the wire axis is perfectly aligned with the plasma jet axis, then the apparatus structure is simple, but process instability occurs due to wire tip wander and poor atomization
Solution Approach 1:
Rather than maintaining perfect symmetry (alignment), the invention intentionally introduces asymmetry by offsetting the wire axis from the plasma jet axis. This asymmetric configuration prevents wire tip wander and stabilizes the plasma arc attachment, improving process reliability with only minimal additional positioning complexity
3Productivity
If the plasma arc is highly concentrated on the wire tip, then melting efficiency is high, but particle agglomeration occurs and globules form on the wire
Solution Approach 1:
The asymmetric offset of the wire axis from the plasma jet axis distributes the plasma energy distribution across the wire surface, preventing excessive concentration at a single point. This reduces particle agglomeration and globule formation while maintaining efficient melting, resolving the contradiction between melting efficiency and atomization quality
Solution Approach 2:
The offset positioning creates different local conditions across the wire surface where plasma contacts it. The plasma arc attaches at specific locations on the wire surface rather than uniformly, creating localized melting zones that improve particle atomization while maintaining overall melting efficiency
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 enhances the robustness of the PTWA process, allowing for higher deposition rates without compromising deposit quality, reducing the formation of large inclusions, and increasing productivity by up to 45% while maintaining stable operation.
Implementation Method 1
The arc and plasma jet provides the necessary thermal energy to continuously melt the wire tip
Implementation Method 2
The plasma is a high velocity jet of ionized gas which is desirably constricted and focused about a linear axis
Implementation Method 3
the plasma provides the dynamics to atomize the molten wire tip into finely divided particles
Implementation Method 4
accelerates the melted particles as a stream generally along the axis of the plasma
Implementation Method 5
Acceleration of the particles is assisted by use of highly compressed secondary gas, directed as a converging gas streams about the plasma-arc axis
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A method of thermally depositing metal onto a target surface using a plasma transferred wire are thermal spray apparatus., wherein the method includes the steps of offsetting the central axis of a consumable wire with respect to an axial centerline of a constricting orifice; and establishing and operating a plasma transferred wire arc between a cathode and a free end of the consumable wire; and melting and atomizing a continually fed free end of the consumable wire into molten metal particles and projecting the particles onto said target surface.