Nickel 201 is the low-carbon counterpart to Nickel 200: the same commercially pure, 99.5%+ nickel base, but with carbon deliberately held to about 0.02% maximum instead of Nickel 200's 0.15% ceiling. That single change is the whole point of the alloy. Above roughly 600°F (315°C), the higher carbon content in standard Nickel 200 can precipitate as graphite at grain boundaries, causing embrittlement in service. Nickel 201 is specified whenever a nickel component will see sustained service above that temperature - furnace parts, high-temperature caustic evaporators, and similar equipment - without giving up any of pure nickel's corrosion resistance to alkalis or its electrical and thermal conductivity. It cross-references to UNS N02201, AMS 5553 (low-carbon nickel sheet and strip), and the DIN 17740 series (wrought nickel and nickel alloys), and like Nickel 200 it is not a superalloy despite sometimes being filed in the same general material-group bucket.

Typical applications include high-temperature caustic handling equipment, electronic and battery components, and any pure-nickel part that must avoid graphitization during elevated-temperature service or welding.

Nickel 201 machines essentially identically to Nickel 200 - the carbon difference that defines the alloy has no meaningful effect on chip formation or tool wear. This is a soft, ductile, ultra-high-conductivity metal, not a heat-resistant superalloy, and it should not be approached with superalloy tactics. Thermal conductivity is high enough that cutting heat dissipates into the chip and part reasonably well rather than concentrating destructively at the edge, so the dominant problem is not edge temperature - it is gumminess. The material shears reluctantly and tends to smear and weld onto any edge that is not sharp, which produces built-up edge (BUE), poor surface finish, and dimensional drift on finishing passes.

As with Nickel 200, work hardening under a dull or rubbing tool is a real risk, so maintaining a steady, adequate chip load matters more than running slow. Sharp, positive-rake cutting edges with polished rake faces and generous coolant (for BUE control and long, stringy chip evacuation) outperform the neutral-to-negative, heavily honed edge preparations used on true nickel-chromium superalloys. Because this alloy is frequently specified for parts that will later be welded or exposed to elevated temperature, finish quality from the initial machining pass matters - a clean, BUE-free surface reduces the risk of stress points that could contribute to cracking in service.