Nb-Ti Balance Spring Coating for Precise Horology Forming
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Solution Overview
Problem
The manufacturing of balance-springs for horology faces challenges in achieving high elastic limit, ease of processing, excellent fatigue strength, stability over time, and thermal compensation, while niobium-titanium alloys tend to stick and seize during forming, leading to dimensional variations and torque issues due to thick copper coatings.
Innovation Solution
A method involving a niobium-titanium alloy blank coated with a fine layer of niobium for anti-sticking and a thicker layer of copper for forming, with the copper layer being selectively removed before final stages to control core dimensions and maintain thermoelastic properties, using specific materials and heat treatments to achieve precise geometry and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thick layer of copper is deposited on the Nb-Ti blank to prevent sticking during forming, then the ease of processing is improved, but the manufacturing precision deteriorates due to dimensional variations of the core
Solution Approach 1:
The coating system is segmented into two distinct layers: a thin first layer (800 nm to 1.2 microns) of niobium or compatible material applied to the Nb-Ti core, and a thicker second layer of copper applied over the first layer. This segmentation allows each layer to serve its specific function - the first layer provides a diffusion barrier and initial anti-sticking surface, while the second layer provides the primary anti-sticking function during forming operations.
Solution Approach 2:
The thin first layer is applied preliminarily to the Nb-Ti core before the thick copper layer is applied. This preliminary action creates a stable interface that prevents copper diffusion into the Nb-Ti core and provides a controlled surface for subsequent copper deposition, ensuring that the core dimensions remain stable throughout the forming process.
2Ease of operation
If a thick layer of copper is used as anti-sticking agent, then the ease of operation is improved, but the manufacturing precision deteriorates due to uncontrolled core dimensions
Solution Approach 1:
The coating system is segmented into two distinct layers: a thin first layer (800 nm to 1.2 microns) of niobium or compatible material applied to the Nb-Ti core, and a thicker second layer of copper applied over the first layer. This segmentation allows each layer to serve its specific function - the first layer provides a diffusion barrier and initial anti-sticking surface, while the second layer provides the primary anti-sticking function during forming operations.
Solution Approach 2:
The thin first layer is applied preliminarily to the Nb-Ti core before the thick copper layer is applied. This preliminary action creates a stable interface that prevents copper diffusion into the Nb-Ti core and provides a controlled surface for subsequent copper deposition, ensuring that the core dimensions remain stable throughout the forming process.
3Ease of manufacture
If copper layer is deposited to facilitate shaping, then the ease of manufacture is improved, but the manufacturing precision deteriorates due to significant torque variations
Solution Approach 1:
The coating system is segmented into two distinct layers: a thin first layer (800 nm to 1.2 microns) of niobium or compatible material applied to the Nb-Ti core, and a thicker second layer of copper applied over the first layer. This segmentation allows each layer to serve its specific function - the first layer provides a diffusion barrier and initial anti-sticking surface, while the second layer provides the primary anti-sticking function during forming operations.
Solution Approach 2:
The thin first layer is applied preliminarily to the Nb-Ti core before the thick copper layer is applied. This preliminary action creates a stable interface that prevents copper diffusion into the Nb-Ti core and provides a controlled surface for subsequent copper deposition, ensuring that the core dimensions remain stable throughout the forming process.
4Ease of operation
If a thick copper layer is applied to prevent sticking, then the ease of operation is improved, but the manufacturing complexity increases due to additional processing steps
Solution Approach 1:
The coating system is segmented into two distinct layers: a thin first layer (800 nm to 1.2 microns) of niobium or compatible material applied to the Nb-Ti core, and a thicker second layer of copper applied over the first layer. This segmentation allows each layer to serve its specific function - the first layer provides a diffusion barrier and initial anti-sticking surface, while the second layer provides the primary anti-sticking function during forming operations.
Solution Approach 2:
The thin first layer is applied preliminarily to the Nb-Ti core before the thick copper layer is applied. This preliminary action creates a stable interface that prevents copper diffusion into the Nb-Ti core and provides a controlled surface for subsequent copper deposition, ensuring that the core dimensions remain stable throughout the forming process.
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 method facilitates the shaping of balance-springs with controlled dimensions and thermoelastic properties, ensuring high elastic limit, low modulus of elasticity, and stable chronometric performance, while preventing sticking and seizing during processing.
Implementation Method 1
forming a layer of a first material having a first thickness around the blank with the core made of Nb—Ti
Implementation Method 2
a layer of a ductile material such as copper... The thickness of the layer of copper for creating horological balance-springs is approximately 10 microns
Implementation Method 3
the first and second materials being chosen so that the second material can be selectively eliminated physically or chemically without substantially attacking the first material
Implementation Method 4
a step of final heat treatment of the balance-spring
Implementation Method 5
g) a step of final heat treatment of the balance-spring
Data Source
AI summary
A balance-spring intended to equip a balance of an horological movement, comprising a core made of Nb—Ti made from an alloy consisting of: niobium: balance to 100% by weight, titanium: between 5 and 95% by weight, traces of elements chosen from the group consisting of O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, each of said elements being present in a quantity between 0 and 1600 ppm by weight, the total quantity formed by all of said elements being between 0% and 0.3% by weight, wherein the core made of Nb—Ti is coated with a layer of niobium, said layer of niobium having a thickness between 20 nm and 10 μm.