Hastelloy and High-Nickel Alloy Forging for Chemical and Process Industry

August 11, 2026


Hastelloy C-276 (UNS N10276), Hastelloy C-22 (UNS N06022), Alloy 400 (Monel, UNS N04400), and Alloy 200/201 (commercially pure nickel) are the specialty nickel alloys used in the most aggressive chemical processing, pharmaceutical, flue gas desulphurisation, and nuclear fuel reprocessing environments. Indian forging manufacturers with high-nickel alloy capability controlled-atmosphere heating, alloy-specific die materials, and NABL testing to ASTM B574/B462 specifications are positioned to supply the global chemical process industry at meaningful cost advantage over European and North American specialty forge shops.

AlloyUNSKey ResistancePrimary Application
Hastelloy C-276N10276Oxidising + reducing acids, chloridesFlue gas scrubbers, pharmaceutical reactors, chemical piping
Hastelloy C-22N06022Higher oxidising resistance than C-276Pharmaceutical, nuclear fuel reprocessing
Alloy 400 (Monel)N04400Seawater, hydrofluoric acid, alkalisMarine, HF acid service, salt plant equipment
Alloy 200/201N02200/201Caustic alkalis, very high purity serviceChlor-alkali, food processing, nuclear
Hastelloy B-3N10675Reducing hydrochloric acid, sulphuric acidHCl handling, chemical synthesis reactors

Hastelloy C-276 the most widely used corrosion-resistant nickel alloy in the chemical process industry contains 57% nickel, 15.5% chromium, 16% molybdenum, and 4% tungsten. The molybdenum-tungsten combination (total 20%) provides unprecedented resistance to both oxidising and reducing acid environments C-276 is one of very few alloys that resists both concentrated sulphuric acid and concentrated hydrochloric acid simultaneously. Flue gas desulphurisation (FGD) scrubbers which treat power plant stack gases containing SO₂, hydrochloric acid, and chlorides use C-276 for the most severe internal components.

Alloy 400 (Monel) a copper-nickel alloy (approximately 67% nickel, 32% copper) is the standard material for marine service in seawater, hydrofluoric acid handling equipment, and chemical plant components where both nickel and copper provide corrosion benefits. For HF (hydrofluoric acid) alkylation units in petroleum refineries where hydrofluoric acid is used as a catalyst Monel is the mandatory material because HF rapidly attacks all stainless steels but does not significantly corrode Monel. All pressure-containing components in the HF acid section of an alkylation unit must be Monel or higher-nickel alloys.

Alloy 200 and 201 (commercially pure nickel, 99%+ Ni) are specified for the most caustic service: concentrated sodium hydroxide at temperatures above 60°C, where stainless steel and most other alloys experience rapid stress corrosion cracking. Chlor-alkali plants use Alloy 200 for caustic handling piping flanges and valve body forgings. Alloy 201 (low-carbon version, 0.02% max C) is preferred for service above 315°C where high-carbon nickel may experience graphite sensitisation.

Forging high-nickel alloys requires specific process adaptations: the forging temperature window is narrower (Hastelloy C-276 should be forged at 1,065–1,175°C deviating above creates incipient melting risk; below creates excessive flow stress); sulphur contamination during heating must be prevented (sulphur compounds react with nickel grain boundaries creating embrittlement sulphur-free furnace linings or inert gas atmosphere are required); and die materials must resist higher contact pressures from nickel alloy flow stress.

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Vinir Engineering — Capability for this Market

  1. AS9100D.
  2. Hastelloy C-276 (N10276) and C-22 (N06022) forgings per ASTM B574 solution annealed with rapid quench.
  3. Alloy 400 (Monel, N04400) forgings per ASTM B564.
  4. Alloy 200/201 forgings per ASTM B564.
  5. Sulphur-free furnace environment for all nickel alloy heat treatment.
  6. NABL OES chemistry to ASTM B574/B564 specified elemental ranges including Mo, W, Cu verification.
  7. 100% UT with alloy-specific calibration standards.
  8. FPI per ASTM E165.
  9. PMI 100% on all nickel alloy deliveries.
  10. Closed die forgings 1–500 kg; open die forgings 500–5,000 kg.

Frequently Asked Questions

1. What is the difference between Hastelloy C-276 and C-22 for chemical processing applications?+–
Both are nickel-chromium-molybdenum alloys with similar corrosion resistance, but C-22 has higher chromium (22% versus 15.5% in C-276) and lower molybdenum (13% versus 16%). The higher chromium in C-22 gives better resistance to oxidising acid environments (concentrated nitric acid, oxidising conditions in mixed acid service). C-276’s higher molybdenum gives better resistance to reducing acid environments (hydrochloric acid, sulphuric acid below the oxidising threshold). For service alternating between oxidising and reducing conditions common in pharmaceutical batch reactors C-22 is often preferred for its more balanced performance in both regimes.
2.What is flue gas desulphurisation (FGD) and why does it require Hastelloy C-276 forgings?+–
FGD is the pollution control process used at coal-fired power plants to remove sulphur dioxide from stack gases. In wet FGD scrubbers, the gas is contacted with limestone slurry the scrubber internal environment contains dilute sulphuric acid, chlorides, fluorides, and temperatures of 40–80°C a combination that causes rapid corrosion of stainless steel and even super duplex. Hastelloy C-276 is specified for the most severely exposed FGD components: spray nozzle forgings, absorber vessel internal structural fittings, and slurry recirculation valve bodies. The corrosion cost of using a less resistant alloy is unscheduled plant shutdowns which cost much more than the Hastelloy premium.
3.Why is Monel the mandatory material for HF alkylation unit forgings in petroleum refineries?+–
HF alkylation uses anhydrous hydrofluoric acid as a catalyst to produce high-octane alkylate blendstock. HF rapidly attacks iron-containing alloys including all grades of carbon steel, alloy steel, and stainless steel through dissolution of the iron component. Nickel and copper-based alloys resist HF corrosion because neither nickel nor copper dissolves in HF. Monel (67% Ni, 32% Cu) provides excellent HF resistance at lower cost than commercially pure nickel. This is a regulatory requirement under refinery safety codes using incorrect materials in an HF acid unit is a major process safety event risk.
4.What is sulphur embrittlement in nickel alloys and how is it prevented during forging heat treatment?+–
Nickel and nickel-base alloys are uniquely susceptible to embrittlement by sulphur compounds at elevated temperatures. Even traces of sulphur react with nickel at grain boundaries to form nickel sulphide (NiS), which has a melting point of 645°C below most nickel alloy processing temperatures. Liquid NiS at grain boundaries causes intergranular cracking during forging or heat treatment. Prevention requires sulphur-free furnace atmospheres, cleaning all forging surfaces to remove sulphur-containing lubricant residues before heat treatment, and inspecting all fixtures and tooling for sulphur contamination.
5.When is Alloy 201 required instead of Alloy 200 for high-temperature caustic service?+–
Alloy 200 is commercially pure nickel with maximum 0.15% carbon. Alloy 201 is the same alloy with maximum 0.02% carbon. At service temperatures above 315°C, Alloy 200’s carbon content can cause carbon segregation to grain boundaries in the form of graphite a phenomenon called graphite sensitisation that reduces ductility and creep resistance. Alloy 201’s ultra-low carbon content prevents graphite sensitisation, making it the preferred alloy for elevated-temperature caustic service above 315°C. In chlor-alkali plants where caustic evaporators operate at temperatures up to 400°C, Alloy 201 is specified; below 315°C, Alloy 200 may be used.