Alloy 205,Nickel 205 ,UNS N02205

Alloy 205,Nickel 205 Wire,UNS N02205

Introduction to Alloy 205 (Nickel 205 Wire, UNS N02205)

Alloy 205, commercially designated as Nickel 205 and classified under UNS N02205, is a high-purity nickel-copper alloy engineered for exceptional cryogenic toughness, resistance to hydrogen embrittlement, and stable mechanical performance in extreme low-temperature environments. Unlike standard nickel alloys, it features a tailored nickel-copper balance (with nickel as the dominant element) and ultra-low impurity levels, enabling reliable operation from cryogenic conditions (-269°C/-452°F, liquid helium temperatures) up to 315°C/600°F. Its fully austenitic microstructure, strengthened via solid-solution effects, delivers outstanding ductility and impact resistance even at near-absolute zero—eliminating the brittle-to-ductile transition common in many metals at low temperatures. Nickel 205 wire, a specialized form of this alloy, is widely used in industries such as cryogenic engineering, energy storage, aerospace, and medical research—excelling in components like superconducting magnet leads, liquid hydrogen transport lines, and low-temperature sensor wires that demand uncompromised performance in harsh, low-temperature environments.

1. Chemical Composition (Typical, wt%)

The chemical composition of UNS N02205 adheres to strict industry standards including ASTM B160 (for nickel and nickel-alloy rod, bar, and wire) and ASME SB160, with a focus on high nickel purity and controlled copper content to optimize cryogenic properties. The typical composition is as follows:

Element

Content Range (wt%)

Function

Nickel (Ni)

94.0 - 96.0

Serves as the primary matrix element, stabilizing the austenitic structure; eliminates brittle-to-ductile transition at cryogenic temperatures, ensuring exceptional toughness down to -269°C.

Copper (Cu)

2.0 - 3.0

A key alloying element that enhances solid-solution strengthening without compromising cryogenic ductility; improves resistance to hydrogen embrittlement in high-pressure hydrogen environments.

Iron (Fe)

≤ 0.5

Minimized to avoid forming ferromagnetic phases (which degrade cryogenic performance) and prevent intergranular embrittlement; limited to improve hot workability during wire production.

Manganese (Mn)

≤ 0.3

Aids in deoxidation during melting and improves cold workability for fine wire drawing; strictly controlled to avoid precipitating brittle intermetallic phases at low temperatures.

Silicon (Si)

≤ 0.1

Reduces oxide formation during hot processing; ultra-low content prevents oxide inclusions that act as stress concentrators in cryogenic service.

Carbon (C)

≤ 0.03

Minimized to prevent carbide precipitation at grain boundaries, which can cause intergranular cracking in cryogenic or hydrogen-rich environments.

Sulfur (S)

≤ 0.010

Strictly limited to avoid hot cracking during wire drawing and welding; reduces the risk of pitting corrosion in hydrogen sulfide (H₂S) environments.

Phosphorus (P)

≤ 0.010

Controlled to avoid grain boundary embrittlement, a critical concern for components subjected to cyclic loading at cryogenic temperatures.

Cobalt (Co)

≤ 0.5

Trace element that slightly enhances high-temperature strength; limited to avoid increasing alloy cost and preserving cryogenic ductility.

Oxygen (O)

≤ 0.015

Ultra-low content prevents forming oxide inclusions (e.g., NiO) that degrade fatigue life in cryogenic cyclic loading applications.

2. Physical Properties

Nickel 205 wire exhibits exceptional physical properties at cryogenic temperatures—its defining advantage—with stable performance across its operating range. Key properties (measured at specified temperatures) are:

Property

Value

Test Condition

Density

8.85 g/cm³

Room temperature (25°C)

Melting Point Range

1435 - 1455°C

-

Thermal Expansion Coefficient

13.4 × 10⁻⁶/°C

20 - 100°C; 4.2 × 10⁻⁶/°C (20 - -200°C)

Thermal Conductivity

90.9 W/(m·K)

25°C; 195 W/(m·K) (-200°C)

Electrical Resistivity

0.07 × 10⁻⁶ Ω·m

25°C; 0.015 × 10⁻⁶ Ω·m (-200°C)

Modulus of Elasticity

207 GPa

Room temperature (tensile); 230 GPa (-200°C)

Poisson’s Ratio

0.31

Room temperature; 0.33 (-200°C)

Curie Temperature

< -269°C

Remains non-ferromagnetic even at liquid helium temperatures (critical for superconducting applications).

Tensile Strength

≥ 480 MPa

Room temperature; ≥ 820 MPa (-200°C)

Yield Strength (0.2% Offset)

≥ 170 MPa

Room temperature; ≥ 650 MPa (-200°C)

Elongation

≥ 45%

Room temperature; ≥ 35% (-200°C)

Impact Toughness (Charpy V-Notch)

≥ 200 J

-200°C; No brittle fracture at -269°C

Hydrogen Embrittlement Resistance

No loss of ductility

100 MPa hydrogen pressure, room temperature (ASTM F1459)

3. Production Process of Nickel 205 Wire

The manufacturing of Nickel 205 wire requires ultra-precise control of impurity levels (especially oxygen, carbon, and iron) and processing to preserve its cryogenic properties. Key steps include:

3.1 Raw Material Melting & Casting (High-Purity Focus)

Melting: High-purity nickel (99.99% pure) and copper are melted via vacuum induction melting (VIM) followed by electron beam remelting (EBM). This dual process ensures ultra-low impurity levels (O₂ < 10 ppm, C < 20 ppm), eliminates gaseous inclusions (H₂ < 5 ppm), and ensures uniform nickel-copper distribution—critical for consistent cryogenic toughness.

Casting: Molten alloy is cast into small-diameter ingots (200 - 500 kg) to minimize segregation, which undergo homogenization annealing at 1050 - 1100°C for 6 - 8 hours. This step eliminates microsegregation of copper and impurities, refines the austenitic microstructure, and prepares the material for hot working.

3.2 Hot Working & Wire Rod Production

Hot Forging & Rolling: Ingots are hot-forged at 950 - 1050°C into billets, then hot-rolled into wire rods (diameter: 6 - 15 mm). Hot working is performed in a protective argon atmosphere to prevent oxidation (critical for maintaining low oxygen content); rods are water-quenched to room temperature to preserve the fine-grained austenitic structure.

Descaling: Hot-rolled rods undergo ultrasonic cleaning followed by acid pickling (dilute nitric acid) to remove any surface oxides—avoiding inclusions that could degrade cryogenic performance.

3.3 Cold Drawing (Wire Formation for Cryogenic Service)

Multi-Pass Cold Drawing: Wire rods are cold-drawn through diamond dies in 8 - 12 passes to achieve the desired diameter (typically 0.05 mm - 5 mm). Each pass reduces diameter by 10 - 15% (smaller reductions than standard alloys) to minimize work hardening and preserve ductility. Intermediate annealing (950 - 1000°C for 30 - 45 minutes, argon-cooled) is performed between passes to relieve residual stresses and restore cryogenic toughness.

Dimensional Control: Laser diameter monitoring is used throughout drawing to maintain ultra-tight tolerance (±0.005 mm for precision wire)—critical for components like superconducting magnet leads, where dimensional variations affect current-carrying capacity.

3.4 Final Heat Treatment (Cryogenic Optimization)

Nickel 205 wire undergoes a specialized heat treatment to maximize cryogenic performance:

Solution Annealing: Heating the wire to 1000 - 1050°C for 1 - 2 hours, followed by rapid water quenching. This step dissolves any residual precipitates, ensures a uniform austenitic microstructure, and eliminates work hardening from cold drawing.

Cryogenic Stabilization (Optional): For components used at temperatures below -200°C (e.g., liquid helium systems), the wire is cooled to -269°C for 24 hours and held, then slowly warmed to room temperature. This step relieves any residual thermal stresses and stabilizes the microstructure, preventing dimensional changes in service.

3.5 Surface Finishing & Quality Inspection

Surface Treatment:

Electropolishing: The wire undergoes electropolishing in a sulfuric-nitric acid solution to achieve a mirror-like surface finish (Ra ≤ 0.05 μm). This removes surface defects and reduces friction, critical for superconducting applications where surface roughness can cause current loss.

Passivation: Optional nitric acid passivation to enhance resistance to atmospheric corrosion during storage and handling.

Cleaning: Ultra-high-purity solvent cleaning (isopropyl alcohol) to remove all contaminants—essential for aerospace and medical applications where particle contamination is prohibited.

Quality Control:

Chemical Analysis: Glow discharge mass spectrometry (GDMS) to verify impurity levels (O₂, C, Fe) meet ultra-low specifications.

Mechanical Testing: Tensile and impact testing at room temperature and -200°C; fatigue testing (10⁹ cycles) at cryogenic temperatures to validate cyclic performance.

Cryogenic Performance Testing: Charpy V-notch impact testing at -269°C to confirm no brittle fracture.

Non-Destructive Testing: Eddy current testing (for surface defects) and ultrasonic testing (for internal flaws); magnetic flux leakage testing to confirm non-ferromagnetic properties.

Dimensional Inspection: Coordinate measuring machine (CMM) for precision wire to confirm diameter, straightness (≤0.05 mm/m), and roundness.

4. Product Applications

Nickel 205 wire’s exceptional cryogenic toughness, resistance to hydrogen embrittlement, and non-ferromagnetic properties make it indispensable in industries requiring performance at extreme low temperatures:

4.1 Cryogenic Engineering & Energy Storage

Superconducting Systems: Fine wire (0.05 - 0.2 mm) for superconducting magnet leads in MRI machines, particle accelerators (e.g., CERN), and fusion reactors—non-ferromagnetic properties avoid interfering with magnetic fields, and cryogenic toughness ensures reliability at -269°C.

Liquid Hydrogen (LH₂) Infrastructure: Wire for LH₂ transport line valves, pressure sensors, and storage tank fasteners—resists hydrogen embrittlement at 70 MPa (10,000 psi) and maintains ductility at -253°C.

LNG (Liquefied Natural Gas) Industry: Wire for LNG tank level sensors and cryogenic valve stems—withstands -162°C and resists corrosion from methane and ethane.

4.2 Aerospace & Defense

Space Exploration: Wire for rocket propulsion system components (e.g., LH₂ fuel line connectors) and satellite cryogenic coolers—maintains strength and ductility in space vacuum (-270°C) and resists hydrogen embrittlement.

Military Aviation: Wire for high-altitude aircraft environmental control systems—performs reliably at -60°C (stratospheric temperatures) and resists fuel vapor corrosion.

4.3 Energy & Chemical Processing

Hydrogen Energy: Wire for high-pressure hydrogen fuel cell stacks (e.g., automotive, industrial) and hydrogen pipeline sensors—resists hydrogen embrittlement at 35 MPa and maintains conductivity.

Chemical Processing: Wire for cryogenic reactor internals (e.g., pharmaceutical freeze-drying equipment) and liquid nitrogen (LN₂) transfer lines—resists corrosion from cold solvents and maintains toughness at -196°C.

4.4 Medical & Scientific Research

Medical Imaging: Wire for MRI machine gradient coils and cryogenic cooling loops—non-ferromagnetic properties ensure image clarity, and cryogenic durability supports long equipment lifespans.

Scientific Instruments: Wire for cryogenic sensors (e.g., temperature, pressure) in quantum computing and low-temperature physics research—operates reliably at near-absolute zero and provides accurate measurements.

4.5 Industrial & Specialized Applications

Low-Temperature Electronics: Wire for cryogenic semiconductor manufacturing equipment (e.g., wafer cooling stages)—maintains conductivity at -200°C and resists corrosion from cleaning chemicals.

Aerospace Fasteners: Wire for small-diameter rivets in cryogenic fuel tanks—combines light weight (density 8.85 g/cm³) with cryogenic strength and hydrogen resistance.

Conclusion

Alloy 205 (Nickel 205 Wire, UNS N02205) is a premier high-purity nickel-copper alloy wire, distinguished by its unmatched cryogenic toughness, resistance to hydrogen embrittlement, and non-ferromagnetic properties. Its ability to perform reliably at temperatures down to -269°C makes it a critical material for superconducting systems, space exploration, and hydrogen energy applications—where standard alloys fail due to brittleness or magnetic interference. The ultra-precise manufacturing process, focused on impurity control and microstructure optimization, ensures consistent performance across all applications. For custom requirements—such as ultra-fine wire (down to 0.01 mm diameter) for quantum computing, specialized electropolishing for superconducting leads, or large-diameter wire (up to 8 mm) for cryogenic structural components—manufacturers offer tailored solutions to meet the most demanding extreme low-temperature challenges.

Packing of Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 644 gallon liquid totes Special package is available on request.