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Types of nickel alloys

Nickel alloys sort two ways. By chemistry they fall into five groups: nickel-chromium, nickel-iron-chromium, nickel-molybdenum-chromium, nickel-copper and the high-strength superalloys. By strengthening they are either solid solution alloys, used annealed or cold worked, or age-hardenable alloys that need a heat treatment to reach full strength. The trade names Inconel, Incoloy, Hastelloy, Monel and Nimonic map onto these groups only roughly, so this page sorts by both.

The families at a glance

Temperature bands are typical service ranges from producer literature, an orientation rather than a design limit. Confirm grade data with the mill and your design code.

Family	Base chemistry	Strengthening	Typical service band	Common grades
Inconel	Nickel-chromium, often with molybdenum, niobium or iron	Both. 600, 601, 625 and 690 are solid solution; 718, X-750 and 725 age harden	Cryogenic to about 1,100 °C for oxidation, strength to about 650 to 700 °C for 718	600, 601, 617, 625, 690, 718, X-750, 725
Incoloy	Nickel-iron-chromium, more iron and less nickel than Inconel	Mostly solid solution; 925 ages	Ambient acid service (825) to creep service near 1,000 °C (800H, 800HT)	800H, 800HT, 825, 925
Hastelloy	Nickel-molybdenum-chromium, or nickel-chromium-iron-molybdenum for X	Solid solution	Ambient to boiling acids (C-276, C-22); oxidation to about 1,200 °C (X)	C-276, C-22, X
Monel	Nickel-copper	400 by cold work only; K-500 ages	Seawater and hydrofluoric acid at moderate temperature	400, R-405, K-500
Nimonic	Nickel-chromium, some with cobalt	Mostly age hardening; 75 is solid solution	Creep and relaxation service roughly 650 to 850 °C	75, 80A, 90
Haynes and Waspaloy	Nickel-chromium-cobalt or nickel-chromium-tungsten	282 and Waspaloy age; 230 is solid solution	Hot-section creep and oxidation, about 700 to 1,150 °C	230, 282, Waspaloy
Iron-nickel superalloys	Iron base with about 25 percent nickel	Age hardening	Fasteners and rings to about 650 to 700 °C	A-286

Map of the types of nickel alloys: solid solution and age-hardenable grades sorted by chemistry group, from nickel-copper Monel to nickel-chromium-cobalt superalloys — Grades placed by chemistry group and strengthening type. Typical classification, confirm the grade against its specification.

Why trade names do not sort the alloys cleanly

Inconel, Incoloy, Monel and Nimonic are trade names of Special Metals Corporation. Hastelloy and Haynes are trade names of Haynes International. Each brand grew over decades and holds alloys that behave very differently. Inconel 600 is a soft, annealed oxidation alloy; Inconel 718 is an aged superalloy with roughly three times the yield strength. Incoloy 800H is a creep alloy for furnaces; Incoloy 825 is an acid alloy for downhole tubing.

Other mills make the same chemistries under generic names such as alloy 625 or alloy C-276, or under their own brands. The UNS number is what fixes the chemistry. A drawing that says only "Inconel" is not a material callout.

Solid solution or age hardening

This split matters more to a buyer than the brand, because it decides what goes on the drawing besides the grade.

Point	Solid solution alloys	Age-hardenable alloys
Where strength comes from	Molybdenum, chromium, tungsten or niobium dissolved in the nickel matrix; cold work	Fine gamma prime or gamma double prime precipitates formed from aluminum, titanium and niobium during ageing
Supplied condition	Annealed or solution annealed, sometimes cold worked	Solution treated, or solution treated and aged
Typical annealed yield	About 170 to 520 MPa	About 700 to 1,100 MPa after ageing
Heat treatment after machining	Rarely, a stress relief at most	Often: rough, age, then finish critical features
Welding	Usually straightforward with matching filler	Weldable for 718; strain-age cracking risk for high gamma prime grades
Examples	600, 601, 617, 625, 690, 800H, 825, C-276, X, 230, Monel 400	718, X-750, 725, 925, K-500, 80A, Waspaloy, 282, A-286

For an age-hardenable part, write the condition and the ageing treatment, or the specification that fixes them, on the drawing. The comparison of precipitation-hardened and solid solution alloys covers the machining sequence, and the Inconel 718 page shows it for the most common aged grade.

The grades on this site by family

Where a grade has its own reference page, the name links to it. Werkstoff numbers are the German material numbers used on EN drawings.

Grade	UNS	W.Nr	Family	Strengthening
Inconel 600	N06600	2.4816	Inconel	Solid solution
Inconel 601	N06601	2.4851	Inconel	Solid solution
Inconel 617	N06617	2.4663	Inconel	Solid solution
Inconel 625	N06625	2.4856	Inconel	Solid solution
Inconel 690	N06690	2.4642	Inconel	Solid solution
Inconel 718	N07718	2.4668	Inconel	Age hardening
Inconel X-750	N07750	2.4669	Inconel	Age hardening
Inconel 725	N07725	none common	Inconel	Age hardening
Incoloy 800H / 800HT	N08810 / N08811	1.4958 / 1.4959	Incoloy	Solid solution
Incoloy 825	N08825	2.4858	Incoloy	Solid solution
Incoloy 925	N09925	none common	Incoloy	Age hardening
Hastelloy C-276	N10276	2.4819	Hastelloy	Solid solution
Hastelloy C-22	N06022	2.4602	Hastelloy	Solid solution
Hastelloy X	N06002	2.4665	Hastelloy	Solid solution
Monel 400	N04400	2.4360	Monel	Solid solution, cold work
Monel K-500	N05500	2.4375	Monel	Age hardening
Nimonic 80A	N07080	2.4952	Nimonic	Age hardening
Haynes 230	N06230	2.4733	Haynes	Solid solution
Haynes 282	N07208	none common	Haynes	Age hardening
Waspaloy	N07001	2.4654	Waspaloy	Age hardening
A-286	S66286	1.4980	Iron-nickel	Age hardening

Chemistry groups, and what each one is for

Nickel-chromium

Chromium gives oxidation resistance at heat and resistance to oxidizing media. Inconel 600 is the plain version. 601 adds aluminum for scale resistance, 690 raises chromium to about 30 percent for nuclear water, 625 adds molybdenum and niobium for strength and pitting resistance, and 617 adds cobalt and molybdenum for creep strength.

Nickel-iron-chromium

Iron lowers cost. Incoloy 800H and 800HT are controlled for carbon and grain size so they hold creep strength in furnaces and petrochemical heaters. Incoloy 825 adds molybdenum and copper for sulfuric and phosphoric acid and for chloride stress corrosion cracking resistance.

Nickel-molybdenum-chromium

The Hastelloy C family. High molybdenum, around 15 to 17 percent in C-276, resists reducing acids and pitting in hot chloride. Carbon and silicon are kept very low so weld heat does not ruin the corrosion resistance.

Nickel-copper

Monel 400 resists seawater, brines and hydrofluoric acid at moderate temperature and machines more easily than the other families. K-500 adds aluminum and titanium so it can be aged for pump shafts and fasteners.

Age-hardening superalloys

Inconel 718 dominates by volume. X-750, Nimonic 80A, Waspaloy and Haynes 282 carry more gamma prime for higher temperatures. 725 and 925 are aged corrosion alloys for oil and gas, where strength and sour service resistance are both needed.

How to pick a family

Start from the environment. Heat and air point to nickel-chromium or the superalloys; acids to nickel-molybdenum-chromium or 825; seawater to Monel or 625; wet H2S to the alloys listed in ISO 15156-3.
Then the load. If the part carries high stress, the age-hardenable grades come in, and with them a heat treat step and a condition on the drawing.
Then the paperwork. Aero parts follow AMS specs, process plant parts ASTM B and ASME SB, oil and gas parts API and ISO 15156. The alloy specifications hub maps them.
Then cost to buy and cut. Within the families that pass, nickel content and machinability set the price. The selection guide walks from service condition to grade.

The blog guide to Inconel, Monel, Hastelloy and Incoloy compares the four best-known brands in plain terms.

Frequently asked questions

What are the main types of nickel alloys?

Sorted by what is added to nickel: nickel-chromium (Inconel 600, 625, Nimonic), nickel-iron-chromium (Incoloy 800H, 825), nickel-molybdenum-chromium (Hastelloy C-276, C-22), nickel-copper (Monel 400, K-500) and the age-hardening superalloys (718, X-750, Waspaloy, 282). A second split runs across all of them: solid solution alloys versus age-hardenable alloys.

Is Inconel a type of nickel alloy or a brand?

Both. Inconel is a trade name of Special Metals Corporation for a group of nickel-chromium alloys. The same chemistries are made by other mills and sold as alloy 625, alloy 718 and so on. The UNS number, for example N06625, names the chemistry independent of the brand.

What is the difference between solid solution and age-hardenable nickel alloys?

Solid solution alloys get their strength from elements dissolved in the nickel matrix and are used annealed or cold worked. Age-hardenable alloys contain aluminum, titanium or niobium that form fine precipitates during an ageing heat treatment, which roughly doubles yield strength. The condition and the ageing cycle then belong on the drawing.

Which nickel alloy family is easiest to machine?

Monel 400, and especially the free-machining Monel R-405, cuts most easily. Incoloy 825 and Inconel 600 follow. Inconel 625, Hastelloy C-276 and aged 718 are harder on tools, and aged Waspaloy and 282 are among the slowest.

Are Incoloy alloys nickel alloys?

Most are. Incoloy 825 and 925 have more nickel than iron. Incoloy 800H and 800HT carry about 30 to 35 percent nickel and more iron than nickel, so some standards file them with iron-nickel-chromium alloys. A-286 is an iron-base superalloy with about 25 percent nickel.

Sources

Trade names belong to their owners. Figures are typical published values, not a promise from inconelcnc.com or any shop.

Reference hub · Last reviewed 22 October 2026

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