Incoloy® – nickel, iron and chromium alloys
Characteristics of Incoloy® alloys
Incoloy® is a family of high-alloy iron-nickel-chromium materials designed for demanding industrial environments. Depending on the grade, these alloys may also contain molybdenum, copper, titanium, aluminum, niobium, and other alloying elements that modify their corrosion resistance, mechanical properties, and behavior at high temperatures.
Incoloy alloys are primarily used where the material must maintain adequate durability in contact with aggressive chemical media, at high temperatures or under the simultaneous effects of temperature, corrosion and mechanical loads.
The Incoloy family includes materials with very different properties and applications. Incoloy 800, 800H and 800HT are widely used in high-temperature installations, while Incoloy 825 is an alloy designed primarily for use in aggressive chemical environments. Other grades, such as Incoloy 925, 945, and 945X, combine high corrosion resistance with enhanced mechanical properties achieved, among other things, through precipitation hardening.
Corrosion resistance of Incoloy® alloys
One of the key characteristics of Incoloy alloys is their high resistance to various types of corrosion. The carefully selected content of nickel, chromium, and additional alloying elements allows these materials to be used in environments much more aggressive than those typical of standard stainless steels.
Chromium is primarily responsible for resistance to oxidation and the formation of a protective passive layer on the material surface. Nickel stabilizes the austenitic structure and improves resistance in many corrosive environments. In alloys containing molybdenum resistance to local corrosion, including pitting and crevice corrosion, is increased.
Dodatek copper, found in Incoloy 825, among others, increases resistance to certain reducing environments, particularly those containing sulfuric acid. The combination of nickel, molybdenum, and copper also gives this alloy high resistance to many environments containing phosphoric acid.
However, the corrosion resistance of individual Incoloy grades can vary significantly. When selecting a material, consider not only the alloy's trade name but also the chemical composition of the medium, its concentration, temperature, pH, chloride content, flow conditions, and stresses.
High temperature resistance
Some Incoloy alloys have been specifically developed for long-term operation at high temperatures. These alloys are particularly important here. Incoloy 800, 800H and 800HT.
Their basic composition is based on iron and approximately 30–35% nickel and 19–23% chromiumThis combination ensures a stable austenitic structure and high resistance to oxidation and carburization at elevated temperatures.
Incoloy 800H and 800HT are characterized by higher creep strength and sustained high-temperature load resistance than the basic Incoloy 800. This is achieved by controlling the carbon, aluminum and titanium content and appropriate heat treatment and material structure.
Thanks to these properties, 800 series alloys are used in petrochemical installations, heat treatment equipment, industrial furnaces, heat exchangers and components of energy installations.
Incoloy 800, 800H and 800HT – basic differences
Incoloy 800 – UNS N08800 is an iron-nickel-chromium alloy characterized by good resistance to oxidation, carburization, and many corrosive environments. It is used in process equipment and components operating at elevated temperatures.
Incoloy 800H – UNS N08810 It has a controlled carbon content of 0,05–0,10% and specific grain size requirements. This allows it to exhibit higher creep resistance and sustained high-temperature loading than the standard Incoloy 800.
Incoloy 800HT – UNS N08811 has an even more precisely controlled composition. The carbon content is 0,06–0,10%, while the combined aluminum and titanium content is maintained in the range of 0,85–1,20%. This alloy is primarily intended for demanding high-temperature applications where high creep strength is essential.
Incoloy 825 – an alloy for aggressive chemical environments
Incoloy 825 – UNS N08825, W.Nr. 2.4858 is a nickel-iron-chromium alloy with added molybdenum, copper, and titanium. Its composition was developed to provide high resistance to a wide range of corrosive environments.
Nickel increases resistance to chloride ion stress corrosion cracking, while the combination of nickel, molybdenum and copper provides high resistance in many reducing environments, including those containing sulfuric and phosphoric acids.
Molybdenum also improves resistance to pitting and crevice corrosion, while chromium increases resistance to oxidizing environments. The addition of titanium, combined with appropriate heat treatment, stabilizes the alloy and reduces its susceptibility to intergranular corrosion associated with sensitization.
Incoloy 825 is used in the chemical industry, acid production and processing installations, the Oil & Gas industry, pollution control equipment and installations operating in aggressive water environments, among others.
Incoloy 925 and precipitation-strengthened alloys
Incoloy 925 – UNS N09925 It belongs to a group of alloys that combine high corrosion resistance with excellent mechanical properties. It is a precipitation-strengthened material, which allows it to achieve significantly greater strength than Incoloy alloys supplied in an annealed or solution-annealed condition.
These types of materials are used, among others, in the oil and gas industry, in elements of mining equipment, fittings, shafts, fasteners and other components operating simultaneously under high mechanical load and in corrosive environments.
The high-strength Incoloy alloys also include grades 945 and 945X, developed for demanding Oil & Gas applications, among others.
Properties of Incoloy® alloys
Due to significant differences in the chemical composition and strengthening method of individual grades, it is not possible to provide a single range of mechanical properties for the entire Incoloy family.
The properties of a particular material depend on, among other things:
- alloy type and chemical composition,
- delivery condition and heat treatment applied,
- product form,
- operating temperatures,
- high temperature exposure time,
- environmental conditions,
- the strengthening mechanism used.
For alloys intended for high temperatures, creep strength, oxidation resistance, and structural stability during long-term service are particularly important. For alloys intended for the chemical and oil & gas industries, resistance to general, localized, and stress corrosion, as well as adequate mechanical strength, may be more important.
Typical Applications of Incoloy® Alloys
Chemical and petrochemical industry – reactors, tanks, heat exchangers, process pipelines, acid installations, refinery equipment components and equipment operating in aggressive chemical media.
Energetics – superheaters, heat exchangers, high-temperature pipelines and components of power equipment operating under long-term load.
Furnace industry and heat treatment – radiant tubes, retorts, muffles, furnace equipment and structural elements exposed to high temperature, oxidation and carburization.
Oil & Gas Industry – elements of mining installations, fittings, drilling tools and components, fasteners and parts of devices operating in aggressive operating environments.
Maritime and offshore industry – installation components exposed to seawater, chlorides and other aggressive environments.
Environmental protection and industrial installations – heat exchangers, gas purification system components, waste processing equipment and components exposed to high temperatures and corrosion at the same time.
Selecting the right Incoloy® grade
The individual Incoloy grades are not directly interchangeable. Alloy selection should be based on actual operating conditions.
The following should be taken into account in particular:
- operating temperature and exposure time,
- type and concentration of the corrosive medium,
- presence of chlorides and other aggressive compounds,
- oxidizing or reducing conditions,
- pressure and mechanical loads,
- required creep resistance,
- risk of pitting, crevice and stress corrosion,
- welding technology and further processing,
- requirements of material and design standards.
In high-temperature installations, the primary criteria may be resistance to creep, oxidation, and carburization, while in chemical installations, the resistance of a specific grade to a given medium is crucial. Therefore, the selection of an Incoloy alloy should always be based on the specific grade and actual operating parameters.
Delivery methods for Incoloy® alloys
Depending on the grade, manufacturing standard and availability, Incoloy alloys can be supplied as, among others:
- sheets and plates,
- tapes,
- round bars,
- flat bars,
- wires,
- seamless and welded pipes,
- forgings,
- semi-finished products intended for further processing.
The availability of specific dimensions, material conditions and product forms depends on the grade and technical requirements of the order.
Species available in Alfa-Tech's offer:
- Incoloy 800, Incoloy 800 H/HT creep resistance and stability up to 1000°C,
- Incoloy 825 – exceptional resistance to acids (sulfuric, phosphoric), used in chemical and offshore applications,
- Incoloy 925 – an alloy for use in the oil and gas industry,
- Incoloy DS – for combustion installations, furnaces and high-temperature sulfur corrosion,
- Incoloy 330 – heat-resistant and corrosive alloy for furnaces and the metallurgical industry,
- Incoloy A-286 – high-strength, precipitation hardened, used in aviation and energy.
Division of nickel alloys
Nickel alloys can be divided into several main families, differing in chemical composition, properties, and typical applications. Below are the most important groups, along with examples of grades available from Alfa-Tech:
Nickel alloys
Inconel® – nickel and chromium superalloys
Alloys with very high resistance to oxidation and creep at high temperatures. Used in the energy, aviation, and chemical industries.
Grades: Inconel 600, Inconel 601, Inconel 625, Inconel 686, Inconel 718, Inconel X-750, Inconel HX.
Incoloy® – nickel, iron and chromium alloys
They combine corrosion resistance with good structural stability. They are particularly valued in the chemical and petrochemical industries.
Species: Incoloy 800 H/HT, Incoloy 825, Incoloy 925, Incoloy DS, Incoloy 330, Incoloy A-286.
Nimonic® – high-temperature superalloys
Precipitation-strengthened materials used in aviation and gas turbines are characterized by high resistance to creep and thermal fatigue.
Types: Nimonic 75, Nimonic 80A, Nimonic 90, Nimonic 263, Nimonic 901.
Udimet® / Waspaloy® – superalloys for extreme loads
Used in aircraft engines and the energy industry, where the highest resistance to creep and thermal fatigue is required.
Species: Udimet 188, Udimet L-605, Waspaloy.
Monel® and pure nickel – chemical and marine resistance
Monel (nickel-copper alloys) and pure nickel are materials resistant to seawater, acids, and alkalis. They are frequently used in the marine, chemical, and specialized equipment industries.
Grades: Monel 400, Monel K-500, Nickel 200, Nickel 201.
Special alloys – Invar®, Kovar®, Permalloy
Materials with unique physical properties—low coefficient of thermal expansion, dimensional stability, or controlled magnetic permeability. Used in electronics, optics, and precision instruments.
Species: Invar 36, Kovar, Permalloy, Nilomag 77.
Hastelloy® / Haynes® – corrosion and high temperature resistant alloys
Alloys with high resistance to aggressive chemical environments, oxidation, and creep. Used in the chemical, energy, and aviation industries.
Grades: Hastelloy B-2, B-3, C-276, C-22, C-4, C-2000, G-30, G-35, X, N; Haynes 214, 230, 242, 282, HR-160.
Inconel®, Incoloy®, Nimonic®, Monel® and Udimet® are registered trademarks of Special Metals Corporation. Waspaloy® is a trademark of ATI Allvac / Precision Castparts, Hastelloy® is a trademark of Haynes International, Invar® and Kovar® are owned by Imphy / ArcelorMittal.