Guides / Materials

Inconel, Monel, Hastelloy or Incoloy: How to Pick the Right Nickel Alloy

September 27, 2026

Inconel, Monel, Hastelloy and Incoloy are all nickel-based, and buyers researching “nickel alloy” often land on content about one of them and assume it applies to all four. It does not. Each family was developed to resist a different failure mode, and specifying the wrong one does not usually show up until the part is already in service.

Why these four get grouped together

All four are registered trademarks or trade names tied to specific alloy families, all built on a nickel base, and all marketed as “corrosion resistant” or “high performance” in generic supplier copy. That is where the similarity ends. The element added alongside nickel, chromium, copper, molybdenum or iron, is what actually determines what each family is good at, and it is also what determines how each one cuts on a machine.

What separates the four families

Family	Base composition	Built to resist	Typical service
Inconel	Nickel-chromium, often with molybdenum or niobium	Oxidation and loss of strength at high temperature	Turbine hardware, exhaust systems, aerospace fasteners
Hastelloy	Nickel-molybdenum-chromium	Severe chemical corrosion, particularly acids	Chemical processing, flue gas desulfurization, pharma equipment
Monel	Nickel-copper	Seawater and chloride corrosion at moderate temperature	Marine shafts, valves, pumps, fasteners
Incoloy	Nickel-iron-chromium	Oxidation at high temperature, at lower cost than full nickel superalloys	Furnace components, heat-treatment fixtures, some process equipment

None of these is a universal upgrade over the others. A shop that machines Inconel well is not automatically the right shop for Hastelloy, since the two alloys work-harden and wear tooling differently even though both sit in the “hard to machine nickel alloy” category.

Inconel: strength and oxidation resistance at high temperature

Inconel is the alloy most buyers mean when they say “superalloy.” Grades like 625 and 718 hold strength at continuous high temperature that steel and stainless cannot approach, which is why they dominate aerospace and gas turbine work. Inconel 718 reaches its strength through age hardening; Inconel 625 through solid-solution strengthening. Both work-harden fast under the tool, which drives most of the machining cost. The Inconel 718 machining guide covers properties, tolerances and the RFQ checklist for the most requested grade in our network, and the 625 vs 718 comparison covers how to choose between the two most common Inconel grades.

Hastelloy: built for acid, not heat

Hastelloy adds molybdenum to a nickel-chromium base, which is what gives it standout resistance to reducing acids, oxidizing acids and mixed chemical environments that would attack Inconel over time. It shows up in chemical processing equipment, flue gas desulfurization systems and pharmaceutical hardware where the part sits in aggressive chemistry rather than extreme heat. Hastelloy work-hardens and wears tooling in a similar way to Inconel, but the specific tool wear pattern and cutting parameters differ enough that a shop’s Inconel experience does not automatically transfer. If your part is Hastelloy, say so specifically on the RFQ rather than describing it as “a nickel superalloy,” since the two families are not interchangeable in either performance or machining approach.

Monel: seawater over high temperature

Monel trades chromium for copper, which is the opposite direction from Inconel and Hastelloy. That composition gives it strong resistance to seawater and chloride-rich wet environments at moderate temperature, plus unusual resistance to hydrofluoric acid, but it has nothing like Inconel’s high-temperature performance. It also machines noticeably easier than Inconel, cutting faster with less tool wear, though it is still a gummy, work-hardening material compared with steel. The Monel vs Inconel guide covers where buyers most often confuse the two.

Incoloy: a lower-cost middle ground

Incoloy grades carry more iron and less nickel than a true Inconel, which lowers raw material cost and generally eases machining somewhat, at the cost of some high-temperature strength and oxidation resistance compared with full nickel superalloys. That makes Incoloy a reasonable choice for furnace components, heat-treatment fixtures and process equipment where the environment is demanding but not extreme enough to justify Inconel’s cost. It is not a substitute for Inconel on a part that genuinely needs Inconel’s temperature range, and treating it as one is a common way buyers end up with a part that underperforms in service.

How to decide, in practice

Describe the actual service condition rather than reaching for an alloy family name out of habit or an old drawing:

• Sustained high heat, oxidizing atmosphere, or a hot rotating section: Inconel, or Hastelloy if acid resistance also matters.
• Aggressive acid or mixed chemical exposure at moderate temperature: Hastelloy.
• Seawater, chlorides, or hydrofluoric acid, at moderate temperature: Monel.
• High-temperature service where cost matters more than peak performance, such as furnace hardware: Incoloy.

If the alloy has not been finalized, state the temperature range, what the part is exposed to, and whether it is wet or dry in service. That gets a shop to the right family faster than naming an alloy based on what a similar-looking part used before. Once the family is clear, the guide to nickel alloy selection walks from the service condition to a grade and a UNS callout.

Getting a quote across any of the four

Our network is built around Inconel and nickel superalloy work, and the RFQ form includes an “other nickel alloy” option for Monel, Hastelloy, Incoloy and related grades so we can match a shop that actually runs the alloy your part needs, not just one that runs Inconel. State the grade if you know it, or the service environment if you do not, and we will confirm fit before matching you with a shop.

Frequently asked questions

Keep reading

• Waspaloy and Rene 41 Machining: The Harder Superalloys Compared With Inconel
• Inconel X-750 vs 718: Which Alloy for Springs and High-Temperature Fasteners