Hastelloy C 276Edit
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Hastelloy C 276 is a versatile nickel-based alloy known for exceptional corrosion resistance across a broad range of chemical environments. Developed for demanding service, it remains a staple in the chemical processing, pharmaceutical, and energy sectors. The alloy’s performance derives from its solid-solution-strengthened matrix, which incorporates chromium, molybdenum, and tungsten to resist both reducing and oxidizing media. It is marketed under the Hastelloy brand and is widely referenced as UNS N10276 in material specification catalogs. For readers exploring related materials, see Nickel alloy and Hastelloy for broader context, as well as corrosion-focused discussions in Corrosion and Seawater.
Composition and microstructure
Hastelloy C 276 is a nickel-based alloy with a high chromium-molybdenum-tungsten alloying package. Typical composition (by weight) is approximate and may vary slightly by manufacturer: - Nickel (Ni): ~57–63% - Chromium (Cr): ~14–16% - Molybdenum (Mo): ~15–17% - Tungsten (W): ~3–5% - Iron (Fe) and other elements: balance, with trace amounts of other constituents
This composition yields a single-phase austenitic solid solution that remains relatively stable over a wide temperature range. The absence of discrete hardening phases means Hastelloy C 276 does not require age hardening; its corrosion resistance is achieved through its stable matrix and high alloying content. See also Alloy and UNS N10276 for additional specification details.
Corrosion resistance
The standout feature of Hastelloy C 276 is its resistance to aggressive media, including: - Broad acids, both oxidizing and reducing, such as hydrochloric acid, sulfuric acid, and mixtures like aqua regia under certain conditions - Hot oxidizing media and chlorides, where resistance to pitting and crevice corrosion is enhanced by the Mo-W combination - Seawater, hypochlorites, and other oxidizing chloride environments
This makes C 276 a common choice for equipment exposed to mixed acid streams, salt-containing processes, and waste treatment scenarios. It typically performs well in environments where many other nickel-based alloys may experience significant corrosion. For broader corrosion concepts, consult Corrosion, along with Pitting corrosion and Crevice corrosion to understand failure modes and mitigation strategies in chloride-containing systems.
Fabrication and processing
Hastelloy C 276 can be formed and fabricated using conventional methods for nickel-based alloys, including rolling, drawing, punching, bending, and welding. The alloy’s good weldability supports the construction of complex components such as tubes, fittings, and process vessels. When welding, standard techniques (e.g., GTAW/TIG, GMAW, or SMAW) are commonly applied, with attention to maintaining proper fit-up and avoiding contamination. Post-weld heat treatment is not strictly required to retain corrosion resistance, but solution annealing in the range of approximately 1100–1150°C (followed by quenching) is sometimes performed to restore uniformity after substantial work, or to optimize mechanical properties for specific applications. See also Welding for general welding considerations and Heat treatment for related processes.
Mechanical properties and service temperature
As a solid-solution strengthened nickel-based alloy, C 276 combines good toughness with strength suitable for many high-temperature applications. Mechanical properties are typically sufficient for service in elevated temperatures encountered in chemical processing and related industries. The alloy maintains structural integrity at temperatures where many stainless steels would degrade, though exact values depend on the product form and processing history. For discussions of how nickel-based alloys perform under thermal stress, see Nickel alloy and Thermal expansion discussions in related material entries.
Applications and industry use
Hastelloy C 276 is favored for equipment and components that confront hostile chemical environments, including: - Chemical processing equipment such as reactors, heat exchangers, and piping in acid and chloride-rich streams - Waste treatment systems where aggressive oxidizers and chlorides may be present - Pharmaceutical and biotech processing equipment requiring stringent corrosion resistance - Pulp and paper processing environments with chemical pulping chemicals - Offshore oil and gas applications where seawater exposure and chlorides are relevant - Marine and chlorinated-water systems, including some cooling and water treatment setups
The alloy’s combination of corrosion resistance and fabricability makes it a go-to choice in fields where reliability and long service life are valued. See related topics in Oil and gas industry and Pharmaceutical industry for context on typical equipment and process requirements.
Standards and specifications
Hastelloy C 276 is specified and supplied under various standards and specifications common to nickel-based alloys. It is closely associated with the designation UNS N10276, and has widely used forms in the metallurgical and engineering communities. General references to standards include ASTM and ASME specifications that cover nickel-based alloys in sheet, plate, tube, pipe, and fitting forms. For product-specific documentation, consult supplier datasheets and standards references such as UNS N10276 and Hastelloy documentation.