Frequently Asked Questions About Hastelloy C276

Hastelloy C276 raises the same handful of questions every time it is specified: how hot can it run, can it be welded without heat treatment, will it survive hydrochloric acid, is it approved for sour gas, and is it worth what it costs. This page answers all of them directly, with the numbers and the standard behind each answer. Every section is written to be quoted on its own, and each one links through to the deeper Hastelloy C276 ultimate guide spoke that owns that topic.

What Is Hastelloy C276, in One Sentence?

Hastelloy C276 is a wrought nickel-chromium-molybdenum-tungsten alloy (UNS N10276) built to resist both oxidising and reducing corrosives in the same piece of equipment, and it is still the broadest corrosion envelope available in a single readily fabricated alloy.

Most corrosion-resistant alloys are specialists. A high-chromium stainless grade handles oxidising acid and fails in hydrochloric acid. A high-molybdenum alloy does the reverse. C276 was designed to sit in the overlap, which is why it turns up in flue gas desulfurization scrubbers, hydrochloric acid plants and sour gas wells alike.

Two details make it practical rather than merely exotic. Carbon is capped at 0.01%, so welding does not precipitate chromium carbides at grain boundaries, and silicon is capped at 0.08% for the same reason. That is why C276 can be used in the as-welded condition, which is what makes large vessels and long pipe runs buildable at all. See What Is Hastelloy C276? for the full introduction.

What Is Hastelloy C276 Made Of?

Nickel is the balance at roughly 57%, with 15-17% molybdenum, 14.5-16.5% chromium, 3-4.5% tungsten, 4-7% iron, and carbon and silicon held to 0.01% and 0.08% maximum respectively.

The composition reads as a compromise until you map each element to the job it does. The high molybdenum plus tungsten is what buys resistance to reducing acids and chloride pitting. Chromium covers oxidising media. The ultra-low carbon and silicon exist purely to stop the heat-affected zone of a weld from sensitising.

Hastelloy C276 composition and what each element does

Full limits, product-form differences and the equivalent-grade cross-reference are in Hastelloy C276 chemical composition and equivalent grades of Hastelloy C276.

Why Is Hastelloy C276 so Corrosion Resistant?

Because no single mechanism is doing the work. Four independent defences - nickel against chloride cracking, molybdenum and tungsten against reducing acid and pitting, chromium against oxidising species, and near-zero carbon against weld sensitisation - overlap in one alloy.

This is the reason C276 keeps winning in streams whose composition drifts. Real process liquor is rarely one clean acid at one temperature. It carries chlorides from the feed, dissolved oxygen from a pump seal, ferric ions from corroding upstream steel. Each of those pushes the chemistry in a different direction, and C276 has an answer for each.

Corrosion threat and the C276 element that answers it

The trade-off is that C276 is a generalist. Where the chemistry is stable and known, a specialist often beats it on corrosion rate or on price, and the corrosion resistance guide and the comparison spokes at the end of this page set out exactly where.

What Is the PREN of Hastelloy C276 and Does It Matter?

About 65-70, which is among the highest of any commercial wrought alloy - but PREN ranks pitting resistance only, and it is a screening number, not a design value.

PREN is calculated as %Cr + 3.3 x %Mo + 16 x %N. For C276 the nitrogen term is negligible, so the number is driven almost entirely by molybdenum. That is why the formula flatters C276: it measures exactly the mechanism C276 was built for.

PREN comparison and what it does not tell you

PREN says nothing about reducing acids, oxidation at temperature, sulphide stress cracking or cost. Use it to shortlist, then decide on iso-corrosion data and the governing Code allowable. See Hastelloy C276 corrosion resistance for the acid-by-acid picture.

What Temperature Can Hastelloy C276 Withstand?

Three different numbers apply and quoting the wrong one is the most common specification error: 677 °C (1250 °F) is the ASME Section VIII Division 1 Code ceiling, about 1040 °C (1900 °F) is the oxidation limit in air, and 232 °C (450 °F) is the cap in NACE sour-gas listings.

The Code ceiling is the one that governs design. ASME Section VIII Division 1 tabulates allowable stress for C276 up to 677 °C, and above that there is no Code basis for a pressure boundary. The oxidation figure is a materials property, not a design limit: the alloy forms a protective scale and does not spall badly in air to about 1040 °C, but it is not creep-strong there and no Code lets you build to it.

In corrosive service the practical ceiling is set by the fluid, not the alloy. Concentrated hydrochloric acid attacks C276 well below 100 °C, whereas dry, clean service can run far hotter. That is why temperature questions always have to be answered together with chemistry.

The three temperature limits people confuse

Between roughly 600 and 1150 °C the alloy can precipitate mu phase and carbides. That band is exactly where a slow cool or an injudicious stress relief would put it, which is why solution annealing is followed by a water quench. Details in Hastelloy C276 temperature limits.

Is Hastelloy C276 Magnetic?

No. C276 is non-magnetic in the solution-annealed condition because it is a face-centred cubic austenitic alloy, with permeability effectively 1.0.

Heavy cold work can raise permeability slightly, but not enough to matter for practical purposes such as magnetic separation, MRI-adjacent equipment or downhole measurement-while-drilling tools. If a specification genuinely requires a permeability limit, state the maximum and the test method on the purchase order rather than relying on the general statement.

This is also a quick field check worth knowing: a magnet will not distinguish C276 from 316L. Positive material identification by spectrometer is the only reliable way to confirm the grade at receipt, and it is worth requiring on critical lines.

Can Hastelloy C276 Be Welded, and Does It Need Post-Weld Heat Treatment?

Yes to both - with a distinction. C276 welds readily by GTAW, GMAW, SMAW and SAW using ERNiCrMo-4 filler, and it does NOT need post-weld solution annealing for corrosion performance. It may still need a stress relief where a Code or a sour-service specification requires one.

The as-welded capability is the whole point of the 0.01% carbon limit. The original C alloy sensitised in the heat-affected zone and had to be annealed after welding, which is impractical for a 40 metre pipe run or a field repair. C276 removed that step.

Welding processes and matching filler metals

Two parameters do most of the work. Keep heat input between 0.5 and 1.5 kJ/mm, and hold interpass temperature at or below 150 °C. Stringer beads are preferred over weaving, no preheat is required, and an argon internal purge is mandatory for pipe root passes. Exceed the heat input and you risk microfissuring; dwell in the 600-1150 °C band and you precipitate mu phase.

Do not confuse fillers across the C family. C276 takes ERNiCrMo-4, while C22 takes ERNiCrMo-10, and they are not interchangeable. Full procedure detail is in Hastelloy C276 welding guide.

Is Hastelloy C276 Suitable for Hydrochloric Acid?

Yes, and this is the alloy's strongest territory. C276 resists hydrochloric acid at all concentrations at ambient temperature and in dilute acid up to the boiling point, which puts it ahead of every stainless grade and almost every nickel alloy.

Hydrochloric acid is the severest common test for a corrosion-resistant alloy because chloride defeats passivity. Stainless steel cannot form a stable film in it at any practical concentration. C276 survives because molybdenum and tungsten hold the surface in a reducing chloride environment where chromium oxide cannot.

Two caveats decide most real cases. Temperature matters enormously - rates climb steeply above about 40 to 50 °C in concentrated acid. And aeration or oxidising contaminants such as ferric ions raise the rate sharply, because dissolved oxygen is a strong enough oxidiser to disrupt the surface but not strong enough to repassivate it. Nitrogen-purged acid gives measurably lower rates than aerated acid at the same concentration.

Indicative C276 corrosion rates in hydrochloric and sulphuric acid

Treat these as screening numbers. The governing source is the Haynes International iso-corrosion diagram for your exact acid, and the presence of chlorides, oxidisers or aeration moves you between bands. See Hastelloy C276 for hydrochloric acid service and Hastelloy C276 for acid service before you commit.

Can Hastelloy C276 Handle Sulphuric, Nitric and Phosphoric Acid?

Sulphuric and phosphoric acid yes across wide ranges; nitric acid is the notable gap. C276 is not the right choice for concentrated or fuming nitric acid, where Hastelloy C22 or a high-chromium alloy performs far better.

The split follows the redox character of the acid. Sulphuric, phosphoric, formic and acetic acid are broadly reducing or mildly oxidising, and the molybdenum-tungsten pair handles them. Nitric acid is strongly oxidising and demands chromium; C276 carries only 14.5-16.5% chromium against 20-22.5% in C22, so the passive film is simply not stable enough.

C276 versus the common mineral and organic acids

Is Hastelloy C276 Good for Seawater and Marine Service?

Technically yes - it resists pitting and crevice corrosion in seawater very well - but it is usually poor value there. In clean seawater without a reducing acid, Inconel 625 or super duplex stainless steel gives you adequate performance for materially less money.

This is the most common over-specification we see. C276 earns its premium when the water carries something else: acid from a scrubber, chlorination chemistry, hydrogen sulphide, or a crevice geometry in a warm, low-flow zone. In plain aerated seawater the alloy's reducing-acid capability simply never gets used.

Marine and seawater selection

The seawater comparison is set out acid-by-acid in Inconel 625 vs Hastelloy C276 for seawater.

Is Hastelloy C276 Approved for Sour Gas Service under NACE MR0175?

Bottom line: Yes. C276 (UNS N10276) is pre-qualified under NACE MR0175 / ISO 15156-3 for sour service at any hydrogen sulphide partial pressure with no chloride limit, provided it is supplied in the solution-annealed condition and the standard listing temperature cap is respected.

Approval is conditional, not blanket. The listed envelope is generous on chemistry but specific on condition, and cold work is where compliance is usually lost: forming beyond the permitted cold-work limit raises both hardness and residual stress, the two variables that drive sulphide stress cracking. Anything formed past the limit needs a full solution anneal to restore compliance.

Sour-service envelope for C276 under NACE MR0175 / ISO 15156-3

Sources differ on the exact ceiling - some publish 40 HRC and 260 °C. The current edition of ISO 15156-3 governs, so confirm the table that applies to your product form before you specify. See Incoloy 825 vs Hastelloy C276 for sour gas for the comparison and ASTM standards for Hastelloy C276 for the specifications.

How Does Hastelloy C276 Compare with Inconel 625, Alloy 20 and 904L?

C276 has the broadest corrosion envelope of the four, but it is the most expensive, and in clean single-mechanism service each of the other three can be the better buy. Choose by the dominant mechanism, not by the headline corrosion rating.

C276 against the alloys it is most often compared with

The pattern is consistent: C276 wins when the chemistry is mixed or uncertain, and loses on value when it is clean and known. Each comparison is worked through in detail in Hastelloy C276 vs Inconel 625 , Hastelloy C276 vs Alloy 20 , Hastelloy C276 vs 904L and Hastelloy C276 vs Incoloy 825.

What Is the Difference Between Hastelloy C276 and Hastelloy C22?

C22 carries about 20-22.5% chromium against C276's 14.5-16.5%, and less molybdenum. That single swap makes C22 the better oxidising-acid alloy and C276 the better reducing-acid alloy. They are not drop-in substitutes and their filler metals differ.

This is the question most often asked and most often answered wrongly, because the two are priced similarly and share the same product specifications under ASTM B575. The temptation to substitute on availability is real, and the consequences show up in nitric acid service on one side and hydrochloric acid on the other.

C276 versus C22, side by side

Full selection logic is in Hastelloy C22 vs C276 key differences and selection guide and Hastelloy C22 vs Hastelloy C276.

How Hard Is Hastelloy C276 to Machine?

Harder than stainless but entirely manageable. C276 work-hardens rapidly, generates high cutting forces and tends to build up an edge on the tool, so the rules are sharp carbide, low speed, positive feed, plenty of coolant and a rigid set-up - and never let the tool rub without cutting.

The single most expensive machining mistake is dwelling. If a tool rubs against the surface instead of cutting, it work-hardens that spot to roughly HRC 40-50 and the next pass struggles or the insert chips. The same rule applies to sawing: never stop the feed mid-cut.

Starting parameters for machining Hastelloy C276

Low thermal conductivity, about 9.8 W/m-K against roughly 50 for carbon steel, means heat stays in the cutting zone rather than leaving with the chip. That is why flood coolant and modest speeds matter more here than on steel. Full troubleshooting is in Hastelloy C276 machining tips and cutting methods for nickel alloy pipe.

What Product Forms and ASTM Specifications Does Hastelloy C276 Come In?

Every common wrought form, each with its own ASTM specification: plate and sheet under B575, seamless pipe and tube under B622, welded pipe under B619, welded tube under B626, bar under B574, fittings under B366 and forgings under B564.

Product form to ASTM specification

Always specify the specification alongside the grade so the mill certificate matches what the Code expects. Sizes and wall thicknesses are covered by ASME B36.19 pipe dimensions , and the full list is in ASTM standards for Hastelloy C276.

How Much Does Hastelloy C276 Cost?

Indicatively six to eight times the price of 316L stainless by weight, with plate commonly quoted in the region of US$75-110 per kilogram. Nickel and molybdenum prices drive it, so treat any figure as a snapshot and ask for a live quotation.

Material is usually only part of the installed cost. On a nickel alloy line the fabrication, welding and inspection content can exceed the metal, which is why the as-welded capability matters commercially as well as technically: removing a post-weld solution anneal removes a furnace cycle, a handling step and a distortion risk.

Indicative cost positioning

For current pipe pricing by size and schedule see Hastelloy C276 pipe price per kg 2026.

How Do You Specify Hastelloy C276 on a Purchase Order?

Six things, and the fluid description matters more than the alloy name: the full stream chemistry, the real temperature and pressure envelope, the product form with its ASTM specification, the delivery condition, the certification level, and a documented check that a cheaper alloy will not do.

Most procurement failures are not metallurgical, they are informational. An order that says only 'C276 plate' can be filled with the right chemistry in the wrong condition, or with a certificate that does not satisfy the Code. Being specific costs a few lines and prevents a rejection at receipt.

1. Write the fluid, not just the alloy. Name every species in the stream: acid type, concentration range, chlorides, fluorides, oxidising contaminants such as ferric or cupric ions, and whether the stream is aerated. Aeration alone can move C276 from excellent to marginal in hydrochloric acid.

2. Fix the real temperature and pressure envelope. Give the operating range plus the upset range, not the design point only. Corrosion is exponential in temperature, and the upset case is what usually kills the cheaper alloy.

3. Choose the product form and the ASTM specification together. Plate is B575, seamless pipe and tube B622, welded pipe B619, welded tube B626, bar B574, fittings B366 and forgings B564. State the specification, not just the grade, so the mill certificate matches what the Code expects.

4. State the delivery condition. Require solution annealed at 1120-1175 °C and water quenched, with the annealing record on the certificate. Air cooling risks mu-phase precipitation and a measurable loss of corrosion resistance.

5. Add certification and traceability. Ask for EN 10204 3.1 with heat number traceable to the finished piece, plus PMI at receipt if the line is critical. For welded work, require the WPS, PQR and filler lot.

6. Decide whether you actually need C276. Compare against Alloy 20, Inconel 625, super duplex and C22 before you buy. C276 is the broadest envelope, not automatically the best value, and in clean single-acid service it is often beaten on cost.

Where Should You Not Use Hastelloy C276?

Four services stand out: boiling concentrated nitric acid, hot concentrated hydrochloric acid, anhydrous hydrogen fluoride at temperature, and clean seawater where a cheaper alloy is adequate. In each case there is a better-specified alternative.

Being explicit about the limits is what separates a specification from a sales pitch. C276 covers a wider envelope than any other single alloy, but it is not universal, and the failures are predictable enough to design around.

Services where C276 is the wrong answer

How Long Does Hastelloy C276 Last?

In well-matched service, decades - C276 absorber internals and bleach plant equipment commonly outlast the maintenance cycle of the plant around them, and field data from flue gas desulfurization outlet ducting shows wall loss below 0.05 mm per year against about 1.2 mm per year for rubber-lined carbon steel.

Service life is not a property of the alloy, it is a property of the match between alloy and environment. The same grade that lasts twenty years in a scrubber can fail in months in hot concentrated hydrochloric acid. What C276 buys you is tolerance of the upsets: a process excursion that would destroy a marginal alloy usually leaves C276 intact.

The practical implication for specification is that life-cycle cost, not material cost, is the right comparison. Where access is difficult, downtime is expensive, or the stream composition is not fully known, the premium is usually recovered several times over.

How Do I Decide Between Hastelloy C276 and a Cheaper Alloy?

Answer three questions in order: is there a reducing acid present, are there chlorides or oxidising contaminants alongside it, and can the stream composition change without warning. If all three are yes, C276. If none are, a cheaper alloy will almost always do.

A decision shortlist

If the answer is genuinely marginal, buy the corrosion coupon before you buy the alloy. A few weeks of immersion testing in the actual stream settles a question that no datasheet can, and it costs a fraction of a wrong material choice on a full line.

Related reading on Hastelloy C276

• Start at the Hastelloy C276 ultimate guide for the whole cluster

• The alloy itself: What is Hastelloy C276 , chemical composition , mechanical properties , corrosion resistance , temperature limits

• Fabrication: welding guide , machining tips , how to choose Hastelloy C276 pipes

• By industry: common applications , chemical plants , acid service , FGD systems , pulp and paper

• Comparisons: vs Inconel 625 , vs Alloy 20 , vs 904L , vs Incoloy 825 , vs Hastelloy C22

• Sourcing: Hastelloy C276 products , ASTM standards , equivalent grades , pipe price per kg

Key Facts About Hastelloy C276

Frequently Asked Questions About Hastelloy C276

What is Hastelloy C276?

Hastelloy C276 is a wrought nickel-chromium-molybdenum-tungsten corrosion-resistant alloy designated UNS N10276 and W.Nr 2.4819. It was developed to resist both oxidising and reducing corrosives in the same piece of equipment, and it remains the alloy with the broadest corrosion envelope that is still readily welded and fabricated.

What is the UNS number for Hastelloy C276?

UNS N10276. The German Werkstoff number is 2.4819 and the common trade-name equivalent is Hastelloy C-276. NiCrMo15W4 is the abbreviated European designation, and the full cross-reference is set out in the equivalent grades guide.

What is Hastelloy C276 equivalent to?

The direct equivalents are UNS N10276, W.Nr 2.4819 and NiCrMo15W4. Hastelloy is a Haynes International trademark, so other producers sell the same UNS number under their own names, which is why specifications should always cite the UNS number and the ASTM specification rather than the trade name alone.

Is Hastelloy C276 magnetic?

No. C276 has a face-centred cubic austenitic structure and is non-magnetic in the solution-annealed condition, with magnetic permeability effectively 1.0. Heavy cold work can raise permeability slightly, but not enough to affect practical applications.

What is the PREN of Hastelloy C276?

Approximately 65 to 70, calculated as %Cr + 3.3 x %Mo + 16 x %N. That compares with about 23 to 25 for 316L, 25 to 28 for Alloy 20, 42 to 45 for super duplex 2507 and 48 to 52 for Inconel 625. PREN ranks pitting resistance only and says nothing about reducing acids, so use it to shortlist rather than to design.

What is the maximum temperature for Hastelloy C276?

It depends on which limit you mean. ASME Section VIII Division 1 tabulates allowable stress to 677 °C (1250 °F), which is the design ceiling. The alloy resists oxidation in air to about 1040 °C (1900 °F) but is not creep-strong there. NACE sour-service listings cap it at 232 °C (450 °F). In corrosive service the fluid sets the practical limit well below any of these.

Can Hastelloy C276 be welded?

Yes. It is welded by GTAW, GMAW, SMAW and SAW using matching ERNiCrMo-4 filler, with ENiCrMo-4 covered electrodes for stick welding. Keep heat input between 0.5 and 1.5 kJ/mm and the interpass temperature at or below 150 °C. No preheat is required and an argon internal purge is mandatory for pipe root passes.

Does Hastelloy C276 need post-weld heat treatment?

Not for corrosion performance. The 0.01% maximum carbon content prevents heat-affected zone sensitisation, so C276 is used in the as-welded condition. A stress relief may still be required by the governing Code or by a sour-service specification, but it is a mechanical requirement rather than a corrosion one.

What filler metal is used for Hastelloy C276?

ERNiCrMo-4 for GTAW, GMAW and SAW, and ENiCrMo-4 for SMAW, both to AWS A5.14 and A5.11 respectively. Do not substitute ERNiCrMo-10, which is the C22 filler, or ERNiCrMo-3, which is the Inconel 625 filler. When welding C276 to a different alloy, the filler is normally chosen to match the more highly alloyed parent.

Can Hastelloy C276 be welded to stainless steel?

Yes, and it is routine for transition joints. Use a nickel-based filler, typically ERNiCrMo-4 or ERNiCr-3 depending on service, and control dilution so the weld metal does not pick up enough iron to form a brittle or less corrosion-resistant zone. Qualify the procedure under ASME Section IX and verify the heat-affected zone hardness for sour duty.

Is Hastelloy C276 good for hydrochloric acid?

Yes - hydrochloric acid is its strongest application. C276 resists all concentrations at ambient temperature and dilute acid up to the boiling point, with indicative rates around 0.08 mm per year in boiling 10% acid. Rates rise steeply above roughly 40 to 50 °C in concentrated acid, and aeration or ferric contamination raises them sharply.

Can Hastelloy C276 handle sulphuric acid?

Yes across a wide range, with indicative rates around 0.20 mm per year in boiling 50% acid. In hot concentrated acid, around 98% at 70 °C, the rate rises to roughly 0.50 mm per year and the choice becomes marginal. In clean non-aerated sulphuric acid below about 65-70%, Alloy 20 is frequently the cheaper and equally effective selection.

Is Hastelloy C276 resistant to nitric acid?

No, not in concentrated or fuming nitric acid. Nitric acid is strongly oxidising and its resistance is governed by chromium, where C276 carries only 14.5-16.5%. Specify Hastelloy C22 with 20-22.5% chromium, or another high-chromium alloy, for nitric acid service.

Is Hastelloy C276 suitable for seawater?

Technically yes - it resists pitting and crevice corrosion in seawater very well - but it is usually poor value. In clean aerated seawater without a reducing acid, super duplex stainless steel or Inconel 625 gives adequate performance for considerably less money. C276 earns its premium in seawater only when acid, chlorination chemistry or hydrogen sulphide is also present.

Is Hastelloy C276 NACE MR0175 approved for sour service?

Yes. C276 is pre-qualified under NACE MR0175 / ISO 15156-3 at any hydrogen sulphide partial pressure with no chloride limit, provided it is solution annealed and the hardness limit is met. Annealed C276 typically measures 85-95 HRB against a 35 HRC ceiling. The standard listing caps temperature at 232 °C (450 °F), and cold work beyond the permitted limit requires a full re-anneal.

What is the difference between Hastelloy C276 and Hastelloy C22?

C22 has roughly 20-22.5% chromium against C276's 14.5-16.5% and less molybdenum, 12.5-14.5% against 15-17%. C22 is therefore better in oxidising media including nitric acid, ferric and cupric chlorides, while C276 is better in reducing acids such as hydrochloric. Their filler metals differ - ERNiCrMo-10 for C22 and ERNiCrMo-4 for C276 - and are not interchangeable.

Which is better, Hastelloy C276 or Inconel 625?

C276 for corrosion, 625 for strength and value. C276's 15-17% molybdenum against 625's 8-10% makes it far better in reducing acids, wet chlorine and mixed acid streams. Inconel 625 has higher chromium and is niobium-stabilised, giving it higher strength and better value in clean chloride and sour gas service without acid. C276 typically costs 30-40% more.

Should I use Hastelloy C276 or Alloy 20?

Alloy 20 in clean non-aerated sulphuric acid up to about 65-70% and moderate temperature, where it is substantially cheaper and performs at least as well. C276 where hydrochloric acid, chlorides, oxidising contaminants or higher temperatures are involved. Alloy 20 is also capped at about 427 °C in ASME Section VIII Division 1 against 677 °C for C276.

How does Hastelloy C276 compare with 904L stainless steel?

C276 is far more capable and far more expensive. 904L has a PREN of roughly 33-35 against 65-70 for C276, handles dilute reducing acid at moderate temperature, and is limited by chlorides and by temperature. Specify 904L where the acid is dilute and cool, and C276 where it is concentrated, hot or chloride-bearing.

Is Hastelloy C276 difficult to machine?

Harder than stainless but manageable with the right approach. It work-hardens rapidly, generates high cutting forces and tends to build up an edge on the tool. Use sharp coated carbide, speeds of 30-60 m/min for turning, positive feed, flood coolant and a rigid set-up, and never let the tool rub without cutting, as that work-hardens the surface to about HRC 40-50.

What is the density of Hastelloy C276?

8.89 g/cm³, or 8890 kg/m³. That is about 13% heavier than carbon steel at 7.85 g/cm³, which matters for weight estimates on large plate fabrications, for lifting plans and for freight costs. Hastelloy C22 is slightly lighter at about 8.69 g/cm³.

What is the melting range of Hastelloy C276?

Approximately 1320-1370 °C (2410-2500 °F). The wide solidification range is one reason weld pool control matters: the alloy is sluggish and does not wet or flow like steel, so welders used to carbon steel often find it needs a different technique.

What is the annealing temperature for Hastelloy C276?

Solution anneal at 1120-1175 °C (2050-2150 °F) followed immediately by a water quench. Air cooling is not acceptable because slow cooling through roughly 600-1150 °C precipitates mu phase and carbides, measurably reducing corrosion resistance and ductility. The delay before quenching should be kept short.

What ASTM specifications cover Hastelloy C276?

B575 for plate, sheet and strip; B622 for seamless pipe and tube; B619 for welded pipe; B626 for welded tube; B574 for bar; B366 for fittings; and B564 for forgings and flanges. ASME SB- versions of the same numbers apply for Code-stamped construction.

What product forms does Hastelloy C276 come in?

Plate, sheet and strip; seamless and welded pipe and tube; round bar and rod; butt-weld fittings including elbows, tees, reducers and stub ends; forgings; and flanges in all common pressure classes. Special forms such as fastener stock and cladding for wallpaper-lined vessels are also produced.

How much does Hastelloy C276 cost?

Indicatively six to eight times the price of 316L stainless by weight, with plate commonly quoted around US$75-110 per kilogram. Nickel and molybdenum market prices drive the figure, so it moves with the LME. Ask for a live quotation and remember that fabrication and inspection can exceed the metal cost on a nickel alloy line.

How long does Hastelloy C276 last?

Decades in well-matched service. Field data from flue gas desulfurization outlet ducting shows wall loss below 0.05 mm per year for C276 against about 1.2 mm per year for rubber-lined carbon steel, and bleach plant equipment commonly outlasts the maintenance cycle around it. Life is a property of the match between alloy and environment rather than of the alloy alone.

Does Hastelloy C276 rust?

Not in the way steel does. It forms a thin, adherent chromium-rich passive oxide film rather than the flaking iron oxide scale that rust is, and it resists chloride pitting that would break that film down on stainless steel. It can still be attacked, by hot concentrated hydrochloric acid, concentrated nitric acid or high-temperature ferric chloride, so it is corrosion-resistant rather than corrosion-proof.

Can Hastelloy C276 be used at cryogenic temperatures?

Yes. It has no ductile-brittle transition because of its face-centred cubic structure, and Charpy impact energy remains above 100 J at -196 °C. That makes it usable down to liquid nitrogen temperature, which is why it appears in cryogenic and liquefied gas service as well as in high-temperature acid duty.

Where should Hastelloy C276 not be used?

Boiling concentrated nitric acid, hot concentrated hydrochloric acid above roughly 80 °C and 20%, anhydrous hydrogen fluoride at temperature, high-temperature ferric chloride, clean aerated seawater where super duplex or Inconel 625 is adequate, and creep-limited service above about 677 °C where no Code allowable stress exists.

How do I choose between Hastelloy C276 and a cheaper alloy?

Ask whether a reducing acid is present, whether chlorides or oxidising contaminants sit alongside it, and whether the stream composition can drift without warning. If all three are yes, C276. If none are, a cheaper specialist alloy will usually do. Where the answer is marginal, run a corrosion coupon in the actual stream before committing.

References & Standards

1. ASTM B575 / B575M - Standard Specification for Low-Carbon Ni-Cr-Mo, Low-Carbon Ni-Cr-Mo-Cu, Low-Carbon Ni-Cr-Mo-Ta and Low-Carbon Ni-Cr-Mo-W Alloy Plate, Sheet, and Strip. The plate and sheet specification for C276. Available from ASTM International.

2. ASTM B622 / B622M - Standard Specification for Seamless Nickel and Nickel-Cobalt Alloy Pipe and Tube. Available from ASTM International.

3. ASTM B619 / B619M and ASTM B626 / B626M - welded pipe and welded tube specifications for nickel alloys. Available from ASTM International.

4. ASTM B574 - Standard Specification for Low-Carbon Ni-Cr-Mo, Low-Carbon Ni-Cr-Mo-Cu and Low-Carbon Ni-Cr-Mo-W Alloy Rod. The bar specification for C276. Available from ASTM International.

5. ASTM B366 / B366M - Standard Specification for Factory-Made Wrought Nickel and Nickel Alloy Fittings. Available from ASTM International.

6. ASTM B564 / B564M - Standard Specification for Nickel Alloy Forgings. Covers C276 forgings and flanges. Available from ASTM International.

7. ASME Boiler and Pressure Vessel Code Section II Part D - Properties. The source of the allowable stress values tabulated for C276 up to 677 °C (1250 °F) in Section VIII Division 1. Available from ASME.

8. ASME B31.3 - Process Piping. Governs piping wall thickness, allowable stress and examination for chemical plant piping in C276. Available from ASME.

9. ASME Section IX - Welding, Brazing and Fusing Qualifications. Governs procedure and performance qualification for C276 fabrication. Available from ASME.

10. NACE MR0175 / ISO 15156-3 - Petroleum and natural gas industries, materials for use in H2S-containing environments in oil and gas production. Part 3 covers cracking-resistant corrosion-resistant alloys including C276 in Table A.26. Available from AMPP and ISO.

11. AWS A5.14 / A5.11 - Specification for Nickel and Nickel-Alloy Bare Welding Electrodes and Rods, and for Nickel and Nickel-Alloy Welding Electrodes for Shielded Metal Arc Welding. ERNiCrMo-4 and ENiCrMo-4 are the matching fillers for C276. Available from AWS.

12. Haynes International Hastelloy C-276 data sheet - the primary source for hydrochloric, sulphuric and hydrofluoric acid iso-corrosion diagrams, oxidation resistance to about 1040 °C, and the as-welded corrosion performance of the alloy.

13. Special Metals corrosion-resistant alloys handbook - supporting data on nickel alloy composition limits, physical properties and welding practice.

14. EN 10204 - Metallic products, types of inspection documents. Type 3.1 is the standard material certificate level requested for C276 pressure equipment.

Still unsure whether C276 is the right call? Send the fluid, concentration, temperature range, pressure and product form to JN Alloy for a metallurgical recommendation with EN 10204 3.1 certification and heat traceability.