Hastelloy C22 VS Hastelloy C276

What is Hastelloy C22?

Hastelloy C22, also known as alloy C22, is a versatile austenitic nickel-chromium-molybdenum-tungsten alloy with enhanced resistance to pitting, crevice corrosion and stress corrosion cracking. Alloy C22 is a nickel-chromium-molybdenum solution-strengthened superalloy with a nominal chemical composition of 56% nickel, 22% chromium, and 13% molybdenum, with additions of iron, tungsten, and cobalt. It is commonly referred to by the trade name Hastelloy C22 and the generic name UNS N06022. C22 offers excellent corrosion and oxidation resistance, outstanding mechanical properties over a wide temperature range, and good fabrication properties.

The high chromium content provides good oxidizing media resistance, while the molybdenum and tungsten content provides good reducing media resistance. This nickel steel alloy is also resistant to oxidizing aqueous media such as wet chlorine and mixtures of nitric acid or oxidizing acids containing chlorine ions.The high chromium content provides good resistance to oxidizing media while the molybdenum and tungsten content give good resistance to reducing media.Other corrosives Hastelloy C-22 has resistance to are oxidizing acid chlorides, wet chlorine, formic and acetic acids, ferric and cupric chlorides, sea water, brine and many mixed or contaminated chemical solutions, both organic and inorganic.

Alloy C22 was developed following the expiration of the patent on C276. Increased chromium with an optimised balance of chromium, molybdenum and tungsten yielded an alloy with superior corrosion resistance and thermal stability, in highly oxidizing environments.Although ductile enough to be formed by cold working, intermediate annealing may be necessary due to work hardening. Forging should be performed between 1750-2050° F followed by rapid cooling. Annealing can be performed at a temperature range between 2020-2150° F followed by a rapid quench. Cooling at an accelerated rate avoids the formation of detrimental phases which form between 1400-1800° F. Welding can be done by gas tungsten-arc, gas metal-arc and shielded metal-arc processes.

What is Hastelloy C276?

Alloy C276 is a nickel-chromium-molybdenum solution-strengthened super alloy, considered the most versatile corrosion-resistant alloy, with a nominal chemical composition of 57% nickel, 16% chromium, and 16% molybdenum, with additions of iron, tungsten, and cobalt. It is commonly referred to by the trade name Hastelloy C276 and the generic name UNS N10276, Alloy C276 is commonly used in extremely corrosive environments that other alloys cannot withstand. Hastelloy C276 has excellent resistance to strong solutions of oxidizing salts, such as ferric chloride and copper chloride. Although there are several variations of the Hastelloy nickel alloy, Hastelloy C276 is by far the most widely used.

The high nickel and molybdenum contents make the nickel steel alloy especially resistant to pitting and crevice corrosion in reducing environments while chromium conveys resistance to oxidizing media. Hastelloy C276 can be successfully fabricated by many methods. The alloy tends to work harden but with the proper care, the alloy is readily hot and cold formed. Complete information on welding, machining and forming is available This nickel alloy is resistant to the formation of grain boundary precipitates in the weld heat-affected zone, thus making it suitable for most chemical process application in an as welded condition.

It has outstanding resistance to a wide variety of chemical process environments including ferric and cupric chlorides, hot contaminated mineral acids, solvents, chlorine and chlorine contaminated (both organic and inorganic), dry chlorine, formic and acetic acids, acetic anhydride, sea water and brine solutions and hypochlorite and chlorine dioxide solutions. Alloy C276 also has excellent resistance to pitting, stress-corrosion cracking and oxidizing atmospheres up to 1900°F. Alloy C276 has exceptional resistance to a wide variety of chemical environments.

The difference between Hastelloy C22 and C276 alloy

The main difference between Alloy C22 and Alloy C276 is their chemical composition. Alloy C22 contains 22% chromium, 12% molybdenum, 3% tungsten, and less than 3% nickel. Alloy C276 contains 27% chromium, 16% molybdenum, 4% tungsten, and 5% nickel.

Precisely because of their different chemical compositions, different production processes must be used when making various products. Because the main alloying elements of C276 are chromium, molybdenum and tungsten, the Material of C276 must be fully solution annealed and have been subjected to quenching or air cooling processes to minimize the formation of intermetallic phases (mu phase), metallic carbides precipation at the grain boundaries , and the risk of sensitization (intergranular corrosion attack).

Although the main alloying elements of C22 are also chromium, molybdenum and tungsten, in order to make this alloy more corrosion-resistant than C276 in highly oxidizing media, it has a higher chromium content and a lower molybdenum content, so the carbon content during processing Must be kept below 0.015% to minimize the formation of intermetallic phases and the risk of precipitation of metal carbides at grain boundaries and sensitization (intergranular corrosion attack).

The biggest difference between Hastelloy C-22 and Hastelloy C-276 is the corrosion resistance. Because Hastelloy C-22 has better control of trace elements, it has better resistance to crevice corrosion at high temperatures than Hastelloy C-276.Though very effective in reducing environments, Hastelloy C22  increase performance in highly oxidizing environments like concentrated Sulfuric acid, Nitric Acid, Phosphoric Acids. Hastelloy C22 alloy has better overall corrosion resistance in oxidizing corrosives than C276 due to the higher chromium content. Below is a table of published industry accepted corrosion rates for C276 and C22.

In terms of mechanical properties, the primary difference also between these two alloys lies in their chemical composition; Alloy C22 contains lower levels of chromium and molybdenum than Alloy C276, making it less resistant to corrosion but easier to weld. Additionally, Alloy 276 has higher tensile strength than Alloy 22, which makes it better suited for applications where high mechanical strength is required, such as turbine blades or valve components. On the other hand, because of its lower levels of chromium and molybdenum, welds on Alloy 22 are generally smoother than those on Alloy 276 due to its reduced susceptibility to hot cracking during welding operations.C22 is normally supplied under annealed conditions with a minimum yield strength of 45. however, C22 can be cold-worked to higher strength levels.

Hastelloy C22 and C276 application areas

Hastelloy C22 vs C276: both made for tough conditions. These alloys are often used in processing that places heavy demands on equipment – involving harsh chemicals, high temperatures, and the need for continuous cleaning to ensure product purity and prevent contamination. Sanitary processing, whether it be for food and beverages, personal care and cleaning products, or pharmaceuticals, falls squarely in the “demanding” category. It has to do with the chemistry of the products used in and made by the equipment, and the chemistry of the materials used to construct the processing system.

Alloy C276 is widely used in the oil and gas industry and is a mainstay of the chemical processing industry because of its resistance to corrosion in a wide range of aggressive substances. In upstream oil and gas, C276 is used as tubing, casing, or liner pipe in corrosive sour service environments characterized by high levels of H2S, CO2, and chlorides. It is also used in other industries that encounter harsh environments, including the pharmaceutical and paper industries. c276 is used in valves for cryogenic applications and has been used in superconductors for temperatures as low as -455°F (-271°C).

Alloy C22’s excellent corrosion resistance facilitates its use in many different markets, wherever harsh environments are encountered, including the chemical process, pharmaceutical, food processing, oil and gas, power generation, and paper industries. Hastelloy C22 Hastelloy C276 has a very similar range of applications. In practical applications, we should consider more details, such as the specific working environment of the material. We need to select corresponding materials according to different corrosive substances.

How to choose between Hastelloy C22 and C276?

Hastelloy C22 and C276 are two of the most machinable alloys available on the market today. Both have exceptional machinability but there are some distinctions between them. Hastelloy C22 offers better corrosion resistance than C276, is easy to cut and drill, and has a strong weldability. In comparison, C276 has higher levels of chromium which improves strength, yet can make it more complex to machine. Despite this, both alloys feature qualities that make them suitable for use in many machining applications and both can be used interchangeably in some cases.

Deciding which alloy is best for your needs depends on the specific application you have in mind. If you need a material that can withstand highly corrosive environments, then you should opt for the superior corrosion resistance offered by Alloy 276; if you are looking for a material that can be easily welded, then you might want to go with the smoother welds provided by Alloy 22 instead. Ultimately though, both alloys provide excellent performance characteristics, so it’s important that you carefully consider your options before deciding which one works best for your project’s needs!