Nickel 201
Nickel 201 is a low-carbon variant of commercially pure nickel, with carbon limited to 0.02% maximum. This low carbon content was developed specifically to prevent intergranular embrittlement (graphitisation) during service above 315°C. It is the preferred grade for sustained elevated-temperature use in alkaline environments.
1. Chemical Composition
The table below shows the elemental composition for Nickel 201. The main difference from Nickel 200 is the reduced carbon ceiling of 0.02%, which prevents graphitization at service temperatures above 315°C.
| GRADE | UNS Designation |
Standard (Pipe) |
Chemical Requirement (Max) | |||||||||||||
| C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Fe | Ti | Al | Co | ||||
| Nickel 201 | N02201 | B161 | 0.02 | 0.35 | 0.010 | 0.35 | min 99.0 | 0.25 | 0.4 | |||||||
2. Mechanical Properties
The values below are typical minimum mechanical requirements for Nickel 201 in the annealed condition per ASTM B161 and B163 product standards for pipe and tube.
| Grade | Condition & Size | Tensile Min, MPa (ksi) | Yield Min, MPa (ksi) | Elongation Min, % |
| Nickel 201 | Annealed: OD ≤ 127 mm | 345 (50) | 80 (12) | 35 |
| Nickel 201 | Annealed: OD > 127 mm | 345 (50) | 70 (10) | 40 |
| Nickel 201 | Stress-Relieved: All sizes | 415 (60) | 205 (30) | 15 |
3. Equivalent Grade
The table cross-references Nickel 201 with equivalent designations in major international standards, allowing engineers to confirm material equivalency across supply chains and regional code requirements.
| GRADE | UNS | GB | JIS | ISO | BS | GOST | |
| WERKSTOFF NR. | EN | ||||||
| Nickel 201 | N02201 | 2.4068 | LC-Ni 99 | NW 2201 | – | NA 12 | НП-2 |
4. Key Technical Advantages
- Graphitisation Prevention Above 315°C: The ≤0.02% C limit stops carbon precipitation at grain boundaries, which is what causes embrittlement in Nickel 200 at sustained high temperatures. This makes Nickel 201 the mandatory choice for caustic service above 315°C.
- Retained Caustic Resistance at High Temperature: Nickel 201 keeps its resistance to molten caustic alkalis (NaOH, KOH) at temperatures up to about 540°C. This allows it to be used in final-stage evaporator trains where caustic concentrations and temperatures are highest.
- Better Formability Than the Higher-Carbon Grade: The lower carbon content produces a slightly softer annealed condition compared to Nickel 200, which improves cold-drawing and forming characteristics for tubular product fabrication.
- Technical Note: Nickel 201 and Nickel 200 share identical corrosion resistance at ambient and moderately elevated temperatures. The selection between the two is governed solely by service temperature: below 315°C, either grade is acceptable; above 315°C, only Nickel 201 should be specified to avoid graphitisation-induced embrittlement.
5. Common Manufacturing Standards
- ASTM B161: Standard specification for nickel seamless pipe and tube, covering UNS N02201 (Nickel 201) for elevated-temperature pressure service applications.
- ASTM B163: Standard specification for seamless nickel and nickel alloy condenser and heat exchanger tubes, applicable to Nickel 201 in heat transfer service.
- DIN 2.4061 / ISO 6207: European standard for nickel alloy tubes; Nickel 201 is designated 2.4061 under EN material numbering.
- JIS H4552: Japanese Industrial Standard for nickel and nickel alloy tubes, covering NW2201 (Nickel 201) designation.
- GB/T 2882: Chinese national standard for pure nickel tubes, covering N6-1 designation equivalent to Nickel 201.
- GOST 14163: Russian standard for seamless tubes from nickel and nickel alloys, covering NP-2M designation.
Manufacturing Standards Comparison Table:
| Standard | GB | EN/DIN | JIS | GOST |
| ASTM B161 (Pipe) | GB/T 2882 | EN ISO 6207 (2.4061) | JIS H4552 | GOST 14163 |
| ASTM B163 (Tube) | GB/T 2882 | EN ISO 6207 (2.4061) | JIS H4552 | GOST 14163 |
6. Primary Applications
- High-Concentration Caustic Evaporators: Final-effect evaporator tubes in chlor-alkali plants where NaOH concentration exceeds 50%, and temperatures go above 315°C. Nickel 201's graphitisation resistance is required here.
- Sodium Hydroxide Storage and Transfer: Piping, vessels, and transfer lines for hot concentrated caustic storage in chemical plants use Nickel 201, as the higher carbon content of Nickel 200 creates a service life risk at sustained temperatures above 315°C.
- Fluorine and Hydrogen Fluoride Handling: Piping and reactor components in fluorochemical production, where pure nickel resists anhydrous hydrogen fluoride and fluorine gas in dry conditions.
- Alkaline Battery Components: Positive electrode tubes and structural elements in alkaline battery construction use Nickel 201 due to its electrical conductivity and caustic resistance.
- Neutral Salt Handling at Elevated Temperatures: Process piping in potash and soda ash production where hot neutral solutions require a material resistant to both the process chemistry and high temperatures.