Alloy 201,Nickel 201 ,UNS N02201

Alloy 201,Nickel 201 Wire,UNS N02201

Introduction to Alloy 201 (Nickel 201 Wire, UNS N02201)

Alloy 201, commercially known as Nickel 201 and classified under UNS N02201, is a low-carbon, high-purity nickel alloy engineered for exceptional cryogenic toughness, superior resistance to hydrogen embrittlement, and excellent thermal/electrical conductivity. As a modified version of the classic Nickel 200, its defining feature is a ultra-low carbon content (≤0.02 wt%), which eliminates carbide precipitation at grain boundaries—critical for preventing intergranular corrosion (IGC) and hydrogen-induced cracking (HIC) in harsh environments. This alloy operates reliably from cryogenic temperatures (-269°C/-452°F, liquid helium conditions) up to 315°C/600°F, leveraging a fully austenitic microstructure to deliver outstanding ductility and stability even at near-absolute zero. Nickel 201 wire, a specialized form of this alloy, is widely 

used in industries such as chemical processing, cryogenic engineering, electronics, and aerospace—excelling in components like low-temperature sensor wires, hydrogen storage system connectors, and high-purity chemical handling equipment that demand uncompromised performance in corrosive, low-temperature, or high-purity environments.

1. Chemical Composition (Typical, wt%)

The chemical composition of UNS N02201 adheres to strict industry standards including ASTM B160 (for nickel and nickel-alloy rod, bar, and wire) and ASME SB160, with a focus on ultra-low carbon and high nickel purity to optimize cryogenic and anti-corrosion properties. The typical composition is as follows:

Element

Content Range (wt%)

Function

Nickel (Ni)

99.0 min.

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.

Carbon (C)

≤ 0.02

The defining ultra-low carbon feature—prevents carbide (Ni₃C) precipitation at grain boundaries, eliminating intergranular corrosion (IGC) and hydrogen-induced cracking (HIC) in hydrogen-rich or corrosive environments.

Iron (Fe)

≤ 0.4

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

Copper (Cu)

≤ 0.2

Trace element that slightly enhances solid-solution strengthening without compromising cryogenic ductility; controlled to avoid reducing thermal conductivity.

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.

Sulfur (S)

≤ 0.010

Strictly limited to avoid hot cracking during wire drawing and welding; reduces the risk of pitting corrosion in sulfur-containing environments (e.g., H₂S).

Phosphorus (P)

≤ 0.010

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

Cobalt (Co)

≤ 0.2

Trace element with minimal impact on properties; limited to maintain high nickel purity and preserve 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 201 wire exhibits exceptional physical properties, particularly at cryogenic temperatures, with thermal and electrical conductivity superior to many nickel alloys. Key properties (measured at specified temperatures) are:

Property

Value

Test Condition

Density

8.89 g/cm³

Room temperature (25°C)

Melting Point Range

1435 - 1455°C

-

Thermal Expansion Coefficient

13.5 × 10⁻⁶/°C

20 - 100°C; 4.3 × 10⁻⁶/°C (20 - -200°C)

Thermal Conductivity

91.4 W/(m·K)

25°C; 198 W/(m·K) (-200°C)

Electrical Resistivity

0.068 × 10⁻⁶ Ω·m

25°C; 0.014 × 10⁻⁶ Ω·m (-200°C)

Modulus of Elasticity

208 GPa

Room temperature (tensile); 232 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 and magnetic applications).

Tensile Strength

≥ 485 MPa

Room temperature; ≥ 830 MPa (-200°C)

Yield Strength (0.2% Offset)

≥ 175 MPa

Room temperature; ≥ 660 MPa (-200°C)

Elongation

≥ 45%

Room temperature; ≥ 35% (-200°C)

Impact Toughness (Charpy V-Notch)

≥ 210 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 201 Wire

The manufacturing of Nickel 201 wire requires ultra-precise control of carbon content and impurity levels, alongside specialized processing to preserve its cryogenic properties and high purity. Key steps include:

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

Melting: High-purity nickel (99.99% pure) is melted via vacuum induction melting (VIM) followed by electron beam remelting (EBM). This dual process ensures ultra-low carbon content (≤0.02 wt%), eliminates gaseous impurities (H₂ < 5 ppm, O₂ < 10 ppm), and removes non-metallic inclusions—critical for consistent cryogenic toughness and anti-hydrogen embrittlement performance.

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 impurities, refines the austenitic microstructure, and dissolves any residual trace carbides—preparing 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 and avoid carbide formation.

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 or contaminate high-purity applications.

3.3 Cold Drawing (Wire Formation for Cryogenic & High-Purity 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, restore cryogenic toughness, and ensure no carbide precipitation.

Dimensional Control: Laser diameter monitoring is used throughout drawing to maintain ultra-tight tolerance (±0.005 mm for precision wire)—critical for components like sensor wires and electronic connectors, where dimensional variations affect performance.

3.4 Final Heat Treatment (Cryogenic & Corrosion Optimization)

Nickel 201 wire undergoes a specialized heat treatment to maximize its key properties:

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

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, reduces friction, and eliminates contamination—essential for high-purity chemical and electronic applications.

Passivation: Optional nitric acid passivation to enhance resistance to atmospheric corrosion during storage and handling, without compromising purity.

Ultra-High-Purity Cleaning: For semiconductor or pharmaceutical applications, the wire is cleaned with ultra-pure solvents (isopropyl alcohol, deionized water) to remove all contaminants, meeting ISO 14644 Class 5 cleanroom standards.

Quality Control:

Chemical Analysis: Glow discharge mass spectrometry (GDMS) to verify carbon content (≤0.02 wt%) and impurity levels (Fe, O₂, H₂) 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.

Corrosion Testing: Intergranular corrosion testing (ASTM A262 Practice E) and hydrogen embrittlement testing (ASTM F1459) to confirm resistance to IGC and HIC.

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 201 wire’s exceptional combination of cryogenic toughness, anti-hydrogen embrittlement, high purity, and thermal/electrical conductivity makes it indispensable in diverse industries:

4.1 Chemical Processing & High-Purity Applications

High-Purity Chemical Handling: Wire for valves, pumps, and sensor probes in semiconductor chemical vapor deposition (CVD) systems—resists corrosion from ultra-pure acids (e.g., hydrofluoric acid) and avoids contamination of process fluids.

Pharmaceutical Manufacturing: Wire for mixer blades and filter screens in drug production—complies with FDA standards (21 CFR Part 177) for food/drug contact, and ultra-low carbon content prevents leaching.

Chlor-Alkali Industry: Wire for electrolyzer components (e.g., cathode connectors)—resists corrosion from brines and chlorine gas, and anti-HIC performance ensures longevity in hydrogen-generating environments.

4.2 Cryogenic Engineering & Energy Storage

Liquid Hydrogen (LH₂) Infrastructure: Wire for LH₂ storage tank sensors, fuel line connectors, and pressure relief valves—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.

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

4.3 Electronics & Semiconductor Industry

Low-Temperature Electronics: Wire for cryogenic semiconductor cooling systems (e.g., quantum computing processors)—excellent thermal conductivity (198 W/(m·K) at -200°C) efficiently transfers heat, and high purity avoids electron contamination.

High-Conductivity Connectors: Wire for high-performance electrical connectors in aerospace and defense electronics—low electrical resistivity (0.014 × 10⁻⁶ Ω·m at -200°C) ensures stable current transmission.

4.4 Aerospace & Defense

Space Exploration: Wire for rocket propulsion system components (e.g., LH₂ fuel line sensors) 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.

4.5 Medical & Scientific Research

Medical Imaging: Wire for MRI machine gradient coils and cryogenic cooling loops—non-ferromagnetic properties ensure image clarity, and high purity avoids patient contamination.

Low-Temperature Research: Wire for cryogenic sensors (temperature, pressure) in quantum physics and material science labs—operates reliably at near-absolute zero and provides accurate measurements.

Conclusion

Alloy 201 (Nickel 201 Wire, UNS N02201) is a premier low-carbon, high-purity nickel alloy wire, distinguished by its unmatched cryogenic toughness, resistance to hydrogen embrittlement, and high thermal/electrical conductivity. Its ultra-low carbon design eliminates intergranular corrosion and hydrogen-induced cracking, making it a critical material for high-purity chemical processing, cryogenic energy storage, and advanced electronics—where standard alloys fail due to contamination, brittleness, or corrosion. 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, ultra-high-purity cleaning for semiconductor use, or large-diameter wire (up to 8 mm) for cryogenic structural components—manufacturers offer tailored solutions to meet the most demanding low-temperature, high-purity, or corrosive environment 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 630 gallon liquid totes Special package is available on request.