How to Choose Between Twin Pure Nickel Grades? A Comprehensive Comparison of Ni02200 and Ni02201 - Blog

Among the grades of commercially pure nickel, Ni02200 (Nickel 200, UNS N02200) and Ni02201 (Nickel 201, UNS N02201) are a pair of "twins" that are most easily confused. Both are nominally commercially pure nickel with a nickel content of ≥99%; their chemical composition specifications appear nearly identical, and their mechanical property data largely overlap.

However, in high-temperature operating environments, selecting the wrong grade can lead to equipment embrittlement and cracking within just a few months. This article provides a comprehensive breakdown of these two grades-covering their chemical composition, mechanical properties, physical properties, and application areas-and offers practical, actionable guidance for material selection.

01 Chemical Composition:

The only key difference is carbon. If you compare the composition standards for the two grades side by side, you will find that, with the exception of carbon content, the upper limits for all other elements are nearly identical.

Typical chemical composition (wt%) for Ni02200 (UNS N02200): Ni + Co: ≥ 99.0% (some standards require ≥ 99.2%); C: ≤ 0.15%; Mn: ≤ 0.35%; Fe: ≤ 0.40%; Si: ≤ 0.35%; Cu: ≤ 0.25%.
Typical chemical composition (wt%) for Ni02201 (UNS N02201): Ni + Co: ≥ 99.0%; C: ≤ 0.02% (approximately 7 times stricter than for N02200); Mn: ≤ 0.35%; Fe: ≤ 0.40%; Si: ≤ 0.35%; Cu: ≤ 0.25%.
In other words, the essential difference between the two grades lies in the upper limit for carbon content: N02200 allows up to 0.15%, while N02201 is restricted to below 0.02%. Ni02201 is not "higher-purity nickel," but rather a "low-carbon version of pure nickel."

Nickel 201 tubes and bars

02 Mechanical Properties:
Nearly identical at room temperature; differences only emerge at high temperatures. In an annealed state at room temperature, the typical mechanical properties for both grades fall within the same range:
Ultimate Tensile Strength (UTS): 380–550 MPa (approx. 55–80 ksi)
Yield Strength (0.2% offset): 105–275 MPa (approx. 15–40 ksi)
Elongation after fracture (50 mm / 2 in): 40%–60%
Hardness: approx. HB 90–140, or HRB 45–73
At room temperature, the two can generally be used interchangeably without issues-which is why many procurement staff and field engineers perceive "no difference" between them.

03 Physical Properties:
The two are almost identical. Since both consist of over 99% nickel, and differences in carbon content have a negligible impact on macroscopic physical properties, a single set of typical values can be used for the physical parameters of both grades:
Density: 8.89 g/cm³ (20°C)

Melting point range: 1435–1446°C
Thermal conductivity: ~70 W/(m·K) at 100°C (approximately 4 times that of 316L stainless steel)
Electrical resistivity: ~9.5–9.6 μΩ·cm at 20°C
Electrical conductivity: ~14%–15% IACS (approximately 1/5 to 1/6 that of pure copper)
Specific heat capacity: ~456 J/(kg·K)
Mean coefficient of linear thermal expansion: ~13.3×10⁻⁶/K (20–100°C)-similar to that of borosilicate glass, making it suitable for glass-to-metal sealing
Curie temperature: ~360°C-the material is ferromagnetic below this temperature and becomes paramagnetic above it. In other words, if your primary concerns are weight, thermal conductivity, electrical conductivity, thermal expansion matching, and the magnetic transition temperature, the two grades can be considered the same material.

04 Application Areas: Select Based on Temperature, Not Just "Purity Level"
When selecting materials, avoid relying on vague intuitions-such as assuming "N02201 is simply better"-and instead use long-term service temperature as the definitive criterion.
Ni02200 (N02200) - The primary grade of pure nickel for use from ambient temperature up to 315°C
Caustic Soda/Soda Ash Industry: Storage tanks, piping, pumps, valves, and neutralization vessels for alkaline solutions at ambient to moderate temperatures.
Food Processing and Organic Acids: Equipment for handling fatty acids, synthetic fibers, and dilute organic acids; meets corrosion-resistance requirements for food-contact applications.
Chemical Industry and Environmental Protection: Heat exchanger components used in fresh water, seawater, or reducing atmospheres.
Electronics and Power: Anodes for vacuum electronic devices, glass-to-metal sealing leads, and battery tabs/strips (for ambient-temperature applications).
Typical Service Temperature: Recommended for long-term use at temperatures up to 315°C.
Ni02201 (N02201) - Pure nickel specialized for high-temperature applications (above 315°C)
High-Temperature Caustic Concentration: Caustic soda evaporators, vessels for molten alkalis, open evaporation coils, and process piping for concentrated alkalis at high temperatures (typically 300–500°C).
Salt Distillation and Molten Salt Environments: Salt distillation vessels and molten alkali tanks.
High-Temperature Reducing Atmospheres: Components requiring resistance to graphitization and hydrogen embrittlement.
Batteries and Vacuum Electronics: Low-carbon nickel is preferred for battery tabs and structural components in vacuum electronic devices that are sensitive to carbon content-even when used at ambient temperatures.
Typical Service Temperature: Suitable for long-term use up to approximately 600°C, with the capacity to withstand even higher temperatures for short durations.

Ni200 Ni201 Pure Nickel Seamless Tube manufacturers