What are the grades and application areas of nickel-based alloys?
- August 18, 2024
- 10:04 pm
- 130
Huaxiao Metal talks about what grades of nickel-based alloys are available and their areas of application.
Nickel and nickel-based alloy family is huge and has many members. Common nickel-based alloy products on the market is also a wide variety of different forms, that nickel and nickel alloy is how to classify it? Generally we classify according to its main alloy composition, the following nickel and nickel alloy widely used in chemical equipment to do a brief introduction.
Pure nickel (201 UNS N02201)
- Corrosion resistance is good against primary acids and salts, but pure nickel is no match for strongly oxidising media such as nitric acid.
- The most outstanding advantage of pure nickel is its resistance to caustics, even to molten caustics.
- Although dry halogenated media are no match for pure nickel, it is not sufficiently corrosion resistant below the dew point of water.
- For applications up to 600°F, a sister grade to alloy 201, nickel 200 (UNS N02200) with a high carbon content, is also available.
The corrosion resistance of nickel-copper alloy 400 is as good as that of pure nickel under reducing media conditions, but the corrosion resistance decreases sharply in the presence of aerated and oxidising chemicals. Alloy 400 has very good resistance to corrosion by hydrohalic acids and halides, and is particularly resistant to hydrofluoric acid and high temperature gases containing fluorine or hydrogen fluoride. Alloy 400 is known to have been developed in 1905 and has been used for over a hundred years. Monel 400 can be regarded as the “ancestor” of all nickel alloys, which are widely used in the treatment of sulphuric acid solutions, seawater and brine. For applications requiring high strength, such as valves and pump components, alloy K-500 (NO5500) is often used, which is a precipitation hardening derivative of alloy 400.
Nickel-chromium-iron alloy 600 UNS N06600
Alloy 600 has chromium added to nickel to enhance its resistance to oxidising environments. Although Alloy 600 exhibits average corrosion resistance to inorganic acids, its corrosion resistance to organic acids is excellent, making Alloy 600 widely used in the production and warehousing of processed fatty acids, hydroxides, and alkaline chemicals. Alloy 600 has excellent heat and corrosion resistance, and can be used in high-temperature halogen environments, making it ideal for organic chlorination processes. Alloy 600 also has excellent resistance to high temperature degradation such as oxidation, carburisation and nitriding.
Nickel-chromium-iron alloy 600 UNS N06600
Alloy 600 has chromium added to nickel to enhance its resistance to oxidising environments. Although Alloy 600 exhibits average corrosion resistance to inorganic acids, its corrosion resistance to organic acids is excellent, making Alloy 600 widely used in the production and warehousing of processed fatty acids, hydroxides, and alkaline chemicals. Alloy 600 has excellent heat and corrosion resistance, and can be used in high-temperature halogen environments, making it ideal for organic chlorination processes. Alloy 600 also has excellent resistance to high temperature degradation such as oxidation, carburisation and nitriding.
Nickel-Chromium-Molybdenum Alloy 625 UNS N06625
The addition of molybdenum to nickel-chromium alloys gives them the ability to resist oxidising and reducing inorganic acids and salts. Molybdenum makes the alloys resistant to chloride pitting and crevice corrosion, and alloy 625 is such a high-strength material with excellent fatigue resistance. Alloy 625CF, a derivative of alloy 625, is mainly used for bellows, and has very good resistance to low-cycle fatigue and heat fatigue. Alloy 625 can be used as corrosion resistant and heat resistant materials as well as alloy 600. Alloy 625 is widely used in chemical and petrochemical equipment in harsh high-temperature environments due to its high-temperature resistance, halogen corrosion resistance, oxidation resistance and carburisation resistance.
Nickel-Chromium Alloy 690 UNS N06690
Alloy 690 is known for its high chromium content, so it is extremely resistant to oxygen and has better corrosion resistance. It can be effectively used as a medium for hot concentrated sulphuric, nitric and nitric/hydrofluoric acid mixtures as well as oxidising salts. The high chromium content also improves the material’s corrosion resistance in high-temperature vulcanisation environments.
Nickel-chromium-iron alloy 825 UNS N08825
Alloy 825 is sometimes included in the super austenitic stainless steel series because the alloy contains nearly 30 per cent iron. It performs well in sulphuric and phosphoric acid media conditions, similar to Alloy 20, for which they were developed primarily. Although alloy 825 is moderately resistant to hydrochloric acid corrosion, it is susceptible to chloride pitting and crevice corrosion, especially in non-flowing, non-aerated solutions. The high iron content of alloy 825 makes it less resistant to alkalis and halogens than alloys with higher nickel content.
Nickel-chromium-iron-molybdenum alloys of the "G" series
The corrosion resistance of alloy G-3 exceeds that of alloy 400, alloy 600 and alloy 825 in many applications; this alloy is particularly resistant to sulphuric and impure phosphoric acid, and is capable of withstanding both reducing and oxidising media. The later developed alloys G- and G-35 have better welding properties and an overall improved corrosion resistance, especially in the heat-affected zone of the weld.
Nickel-chromium-molybdenum alloy "C" series of alloys
Alloy C-276 is an excellent alloy used in the chemical industry to cope with the conditions of extremely corrosive media (beyond the capabilities of stainless steel), with outstanding resistance to corrosion in a wide range of acids, acidic salts and other types of corrosive chemicals. Alloy C-276 performs well in harsh environments such as wet chlorine gas and hypochlorite. Because of its high molybdenum content, alloy C-276 has excellent resistance to pitting and crevice corrosion caused by chloride ions. The search for materials with better metallurgical properties and corrosion resistance than Alloy C-276 has led to the development and commercialisation of several proprietary “C” series alloys, namely Alloys C-22, 622, 59, 686 and C-2000, which have approximately equal molybdenum content, and all have significantly higher chromium content than Alloy C-276. Some grades also contain tungsten or copper.
Nickel-molybdenum "B" series alloys
Alloy B-2 has outstanding corrosion resistance to reducing sulphuric, phosphoric and hydrochloric acids. It is particularly suitable for hydrochloric acid equipment in the full range of concentrations and temperatures up to the boiling point. Oxidising chemicals have a detrimental effect on the corrosion resistance of this alloy, especially strong oxidising agents such as iron and copper ions which are impurities in the solution. The later developed alloy B-3 and alloy B-4 perform better than alloy B-2, and one of the benefits of these new grades is that the formation of undesirable microstructures (which may cause embrittlement) during processing is minimised.
An example of a nickel-based alloy is Inconel 625. This alloy is known for its excellent resistance to oxidation and corrosion, making it suitable for extreme environments, such as aerospace, marine, and chemical processing industries. It retains high strength and stability across a wide temperature range.
Many alloys contain nickel, but Stainless Steel 304 is a common example. Stainless steel 304 contains approximately 8-10.5% nickel, which contributes to its corrosion resistance and makes it one of the most widely used stainless steels for kitchen equipment, chemical containers, and architectural applications.
A nickel alloy material is a metal composed primarily of nickel mixed with other elements such as chromium, iron, copper, and molybdenum. These alloys are designed to have specific properties like high corrosion resistance, heat resistance, and strength, making them ideal for applications in aerospace, chemical processing, and marine environments.
The “best” nickel alloy depends on the application, but Inconel 718 is often considered one of the most versatile nickel alloys. It offers high strength, excellent corrosion resistance, and good creep resistance at high temperatures, making it a popular choice in aerospace, gas turbines, and nuclear reactors.
Nickel-based superalloys are designed to withstand extreme conditions and include:
- Inconel 718
- Inconel 625
- Hastelloy C-276
- Nimonic 80A
- Waspaloy
- Rene 41 These alloys are used in high-temperature applications such as turbine engines, nuclear reactors, and chemical plants due to their excellent mechanical strength and resistance to thermal creep deformation.
Yes, Inconel is a nickel-based alloy. It is known for its ability to withstand extreme environments, particularly high temperatures and corrosive conditions. Inconel alloys, such as Inconel 600, 625, and 718, are widely used in aerospace, chemical processing, and marine industries for their outstanding performance in challenging environments.
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