Nickel-Platinum Sheathed Wire Intermediate Layer Diffusion Annealing
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Solution Overview
Problem
Existing nickel-platinum sheathed wires require a high proportion of platinum to prevent nickel oxidation, leading to high material costs and uneven platinum layer thickness, limiting their application range and mechanical strength at elevated temperatures.
Innovation Solution
A method involving a nickel core and a platinum sheath with an intermediate layer of gold, silver, or their alloys, where the composite is diffusion annealed and drawn through dies to achieve a uniform and reduced platinum layer thickness, reducing platinum usage while maintaining mechanical strength and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick platinum layer is used to prevent nickel oxidation, then chemical resistance is improved, but material cost increases and layer thickness uniformity deteriorates
Solution Approach 1:
The patent divides the protective function into two segments: a thin platinum layer (0.5-5 μm) for oxidation prevention and an intermediate layer (5-20 μm) of gold, silver, or copper for adhesion and diffusion control. This segmentation allows the platinum layer to be much thinner while maintaining chemical resistance, reducing platinum content from 25-32 wt% to 15-25 wt%.
Solution Approach 2:
The patent introduces an intermediate layer between nickel and platinum that acts as a mediator. This layer controls nickel diffusion, enhances adhesion, and allows the platinum layer to be thinner while maintaining protection. The intermediate layer materials (gold, silver, copper) have appropriate diffusion characteristics that prevent excessive nickel migration into the platinum.
2Reliability
If a thick platinum layer is used to prevent nickel oxidation, then chemical resistance is improved, but manufacturing cost increases
Solution Approach 1:
By segmenting the protective function between platinum and intermediate layers, the platinum content is reduced from 25-32 wt% to 15-25 wt%, directly reducing material cost while maintaining chemical resistance through the combined system.
Solution Approach 2:
The patent changes the platinum layer thickness parameter from 6.3 μm (conventional) to 0.5-5 μm (invention), and introduces an intermediate layer parameter (5-20 μm). These parameter changes reduce platinum consumption and manufacturing cost while achieving the same protective function.
3Ease of manufacture
If conventional drawing process is used, then production is simplified, but platinum layer thickness uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-coating the nickel core with an intermediate layer before the drawing process. This preliminary coating ensures that during subsequent drawing and reduction, the platinum layer maintains uniform thickness because the intermediate layer provides a consistent base that controls material flow and prevents localized thinning.
Solution Approach 2:
The intermediate layer acts as a mediator during the drawing process, controlling the flow of materials and ensuring uniform deformation. This mediator layer prevents the platinum from thinning unevenly during reduction, maintaining manufacturing precision while using a conventional drawing process.
4Strength
If high temperature diffusion annealing is used to join nickel and platinum, then bondability is improved, but nickel oxidation and alloy zone formation increase
Solution Approach 1:
The intermediate layer serves as a mediator during diffusion annealing, allowing nickel and platinum to bond indirectly. This prevents direct contact between nickel and oxygen, reducing oxidation, while still enabling diffusion bonding through the intermediate layer at temperatures of 500-900°C.
Solution Approach 2:
The intermediate layer acts as a sacrificial or consumable element that controls the diffusion process. It allows bonding to occur while preventing harmful direct interactions between nickel and platinum or oxygen, effectively 'sacrificing' its own structural integrity to enable the bonding process without oxidation.
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 method allows for a cost-effective production of sheathed wires with a uniform platinum layer, reducing platinum usage by 17.6% and enhancing their application range by preventing nickel-platinum alloy zone formation and ensuring stable connections.
Implementation Method 1
The intermediate layer prevents nickel diffusion into the platinum sheath during high-temperature processing, forming a diffusion barrier
Implementation Method 2
diffusion annealing and drawing through dies to achieve a uniform and reduced platinum layer thickness
Data Source
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AI summary
The invention relates to a method for producing a sheathed wire (1) with a nickel core (2) and a platinum sheath (4) comprising the steps of: A) providing a nickel rod and a platinum tube; B) coating the rod and/or the tube with at least one intermediate layer (5) of at least one of the metals gold, silver, palladium, copper, iridium, ruthenium and rhodium or a base alloy thereof; C) inserting the coated rod into the tube; D) reducing the diameter of the tube with the rod therein by drawing it through a die, by rolling it, or by hammering it, thereby joining the tube to the rod, wherein the outer diameters of the tube and the rod are reduced during the reducing process; E) diffusion annealing of the joined assembly at a temperature between 550 °C and 900 °C; and F) drawing the diffusion-annealed assembly at least once through at least one further die, thereby reducing the outer diameter of the assembly.The invention also relates to a sheathed wire (1) produced by such a method.