Nickel 201 is a commercially pure wrought nickel alloy (99.6 percent minimum nickel) with a controlled low carbon content (maximum 0.02 percent). It is a low-carbon version of Nickel 200, specifically designed for use at elevated temperatures where graphite precipitation could embrittle higher-carbon grades. The alloy retains the excellent corrosion resistance, good mechanical properties, and fabricability of Nickel 200, but is suitable for continuous service above 315°C (600°F).

The nominal chemical composition is: nickel 99.6 percent minimum, carbon up to 0.02 percent, iron up to 0.40 percent, manganese up to 0.35 percent, silicon up to 0.35 percent, copper up to 0.25 percent, and sulfur up to 0.01 percent.

Key mechanical properties (typical, annealed condition):

● Tensile strength: 345–480 MPa

● Yield strength (0.2% offset): 80–240 MPa

● Elongation: 40–50 percent

● Density: 8.89 g/cm³

Nickel 201 offers excellent resistance to caustic alkalis (sodium and potassium hydroxide) across a wide temperature and concentration range, even at high temperatures where Nickel 200 would suffer from embrittlement. It also resists many reducing acids, neutral and alkaline salt solutions, and dry gases. The alloy is not recommended for oxidizing acids (e.g., nitric) or high-temperature sulfur-containing atmospheres. It maintains good ductility and mechanical properties from cryogenic temperatures up to about 650°C (1,200°F) for short-term exposure, and is suitable for long-term service at 315–600°C.

Common standards: ASTM B162 (plate, sheet, strip), B160 (rod, bar, wire), B161 (seamless pipe and tube), B163 (seamless tube for heat exchangers), ASME SB-162, SB-160, SB-161.

Typical applications include:

● Chemical processing: equipment handling caustic alkalis at elevated temperatures, such as evaporators, piping, pump shafts, and heat exchangers.

● Synthetic fiber production: spinnerets and other components in high-temperature caustic environments.

● Electronics and aerospace: components requiring pure nickel properties above 315°C.

● Food processing: high-temperature equipment handling fatty acids and other products.

Comparison with Nickel 200: Nickel 200 has a higher carbon limit (0.15 percent) and is suitable for service below 315°C. Above 315°C, Nickel 200 can form graphite at grain boundaries, leading to embrittlement. Nickel 201, with its low carbon (0.02 percent max), resists this phenomenon and is the correct choice for elevated-temperature applications. At room temperature, the two alloys have similar corrosion resistance and mechanical properties.

Selection guidance: Choose Nickel 201 for service above 315°C, especially in caustic alkalis at high temperatures. For applications below 315°C, Nickel 200 is generally more economical. For ultra-high-purity requirements (e.g., semiconductor), consider Nickel 270. For oxidizing acid environments, select a nickel-chromium alloy such as Inconel 600.