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Table of Contents
Hastelloy C276 is a nickel-based corrosion-resistant alloy whose chemistry is nickel, molybdenum, chromium, and tungsten.
The alloy is identified by UNS N10276 and W.Nr. 2.4819. The composition ranges are:
Element | Composition, wt.% | Primary Metallurgical Role |
|---|---|---|
Nickel (Ni) | Balance | Matrix, ductility, corrosion resistance |
Molybdenum (Mo) | 15.0–17.0 | Reducing-acid and localized-corrosion resistance |
Chromium (Cr) | 14.5–16.5 | Oxidizing-environment resistance |
Iron (Fe) | 4.0–7.0 | Alloy balance and metallurgical control |
Tungsten (W) | 3.0–4.5 | Solid-solution strengthening and corrosion resistance |
Cobalt (Co) | 2.5 max. | Controlled residual/alloying element |
Manganese (Mn) | 1.0 max. | Deoxidation and processing control |
Vanadium (V) | 0.35 max. | Minor alloying element |
Silicon (Si) | 0.08 max. | Kept low to control precipitation |
Carbon (C) | 0.01 max. | Kept very low to limit carbide precipitation |
Copper (Cu) | 0.50 max. | Controlled residual element |
Phosphorus (P) | 0.04 max. | Controlled impurity |
Sulfur (S) | 0.03 max. | Controlled impurity |
These values are consistent with published C276 composition data and the chemical requirements listed for UNS N10276 in ASTM B575. ASTM B575 covers C276 plate, sheet, and strip and specifies composition requirements for the alloy.
The key point is that C276 is not simply a high-nickel alloy. Its performance comes from the interaction of several major alloying elements and the deliberate restriction of carbon and silicon.
For quick reference, the most important elements are
Nickel: balance
Molybdenum: 15.0–17.0%
Chromium: 14.5–16.5%
Tungsten: 3.0–4.5%
Iron: 4.0–7.0%
Cobalt: maximum 2.5%
Manganese: maximum 1.0%
Vanadium: maximum 0.35%
Carbon: maximum 0.01%
Silicon: maximum 0.08%
The combination of approximately 15–17% molybdenum, 14.5–16.5% chromium, and 3–4.5% tungsten is particularly important. These elements work with the nickel to give C276 its broad resistance to aggressive chemical environments.
Haynes International publishes essentially the same principal composition ranges for C276-related welding products, including 14.5–16.5% chromium, 15.0–17.0% molybdenum, 4.0–7.0% iron, and 3.0–4.5% tungsten.
Nickel is the balance element in Hastelloy C276.
Rather than specifying nickel as a narrow percentage range, material standards generally define it as the remainder after the other specified elements are accounted for. Some published product data identify nickel as approximately 57% minimum, while the actual amount varies with the chemistry of the individual heat.
Nickel provides the alloy's continuous austenitic matrix and contributes to:
General corrosion resistance
Ductility
Toughness
Resistance to certain reducing environments
Metallurgical stability
The nickel matrix also allows substantial amounts of chromium, molybdenum, and tungsten to be incorporated without transforming C276 into a conventional stainless-steel-type alloy.
This is one reason C276 behaves differently from stainless steels such as 316L or 904L.
Molybdenum is one of the defining elements of Hastelloy C276.
C276 contains 15.0–17.0% molybdenum, which is a substantial concentration for an engineering alloy.
Molybdenum is particularly important for resistance to reducing acids and localized corrosion.
Its presence helps C276 perform in environments containing aggressive species such as hydrochloric acid and other reducing chemical media.
Molybdenum is also important when chloride exposure is combined with temperature and mechanical stress.
This does not mean that molybdenum alone makes C276 corrosion resistant. Rather, its effectiveness comes from its interaction with nickel and chromium, along with tungsten and the alloy's low levels of carbon and silicon.
For this reason, the molybdenum content should be considered one of the defining fingerprints of C276.
Hastelloy C276 contains 14.5–16.5% chromium.
Chromium contributes strongly to resistance in oxidizing environments and helps broaden the alloy's corrosion envelope beyond that provided by nickel and molybdenum alone.
The distinction between chromium and molybdenum is useful when understanding C276:
Chromium → particularly important for oxidizing environments
Molybdenum → particularly important for reducing acids and localized corrosion
The two elements complement each other.
This balanced chemistry is one reason C276 can be considered for chemical environments that may fluctuate between reducing and oxidizing conditions.
The alloy should nevertheless be evaluated against the actual process chemistry. No alloy should be described as universally corrosion-proof.
Hastelloy C276 contains 3.0–4.5% tungsten.
Tungsten contributes to solid-solution strengthening and complements molybdenum in severe corrosion environments.
The presence of tungsten is one of the characteristics that separates C276 from several other nickel-chromium-molybdenum alloys.
From a materials-engineering perspective, tungsten is not present merely to increase strength. It forms part of the alloy's carefully engineered corrosion-resistant chemistry.
The combined presence of:
Ni + Cr + Mo + W
is therefore more significant than any one element considered in isolation.
The specified iron content of Hastelloy C276 is 4.0–7.0%.
Iron is not the principal corrosion-resistance element in C276, but it is intentionally controlled as part of the alloy's overall chemistry.
Because nickel is the balance element, the alloy does not require the very high chromium-to-iron relationship found in some stainless steels.
Iron also influences phase stability and manufacturing chemistry.
When reviewing a material certificate, the iron value should therefore be compared with the applicable product specification rather than judged against an arbitrary "ideal" percentage.
Carbon is limited to 0.01% maximum in commonly specified wrought C276 compositions.
This is one of the most important details in the alloy's chemistry.
Carbon can combine with chromium and other alloying elements to form carbides, particularly under certain thermal conditions. Excessive carbide precipitation can reduce the corrosion resistance of grain boundaries and become especially important during welding and heat treatment.
Keeping carbon extremely low helps reduce this risk.
This feature is particularly important because Hastelloy C276 is frequently fabricated into:
Chemical-process piping
Pressure vessels
Heat exchangers
Scrubbers
Tanks
Welded fittings
Process equipment
Low carbon does not mean that welding can be performed without procedure control. Welding parameters, filler metal, cleanliness, heat input, and applicable fabrication requirements still matter.
Haynes identifies C276 as a weldable corrosion-resistant alloy and supplies matching C276 filler products under AWS A5.14 ERNiCrMo-4.
For a detailed treatment of fabrication, see Hastelloy C276 Welding Guide.
Silicon is limited to approximately 0.08% maximum in commonly specified wrought C276 chemistry.
Silicon can be useful as a deoxidizing element during metallurgy, but excessive silicon in highly alloyed nickel systems can contribute to undesirable phases or precipitation.
The low silicon specification therefore forms part of C276's broader strategy of maintaining a clean, corrosion-resistant microstructure.
The combination of:
Low carbon
Low silicon
Controlled phosphorus
Controlled sulfur
helps maintain the metallurgical characteristics required for demanding corrosion service.
Not every element in C276 exists at a high concentration.
Several elements are deliberately kept at low levels.
Cobalt
Cobalt is typically limited to 2.5% maximum.
It is not the primary reason for C276's corrosion resistance, but it is controlled as part of the alloy chemistry.
Manganese
Manganese is limited to 1.0% maximum and can contribute to deoxidation and processing control.
Vanadium
Vanadium is limited to 0.35% maximum.
Its concentration is relatively small compared with molybdenum, chromium, or tungsten.
Copper
Copper is limited to 0.50% maximum.
It is not a principal alloying element in C276 and is therefore tightly controlled.
Phosphorus and Sulfur
Phosphorus and sulfur are impurity elements that are controlled at low levels.
Typical limits are:
Phosphorus: ≤0.04%
Sulfur: ≤0.03%
The exact limits can vary by product specification, so the governing ASTM or ASME specification should always be used for purchasing and acceptance.
The most important lesson is that C276's corrosion performance comes from the combined chemistry, not from a single "magic" element.
A simplified way to understand the alloy is:
Element | Main Contribution |
Nickel | Corrosion-resistant matrix and ductility |
Chromium | Resistance to oxidizing environments |
Molybdenum | Reducing-acid and localized-corrosion resistance |
Tungsten | Additional corrosion resistance and solid-solution strengthening |
Iron | Controlled matrix and compositional balance |
Carbon | Kept low to reduce carbide-related corrosion concerns |
Silicon | Kept low to control undesirable precipitation |
This gives C276 a broad corrosion-resistance profile.
That profile is particularly valuable when the process environment contains more than one corrosive mechanism.
For example, a chemical-processing system may simultaneously involve:
Chlorides
Acids
Water
Oxidizing species
Elevated temperature
Welded joints
Flow-related effects
An alloy designed around only one corrosion mechanism may therefore be unsuitable.
C276's multi-element chemistry is intended to address a broader range of conditions.
For detailed corrosion data, refer to Hastelloy C276 Corrosion Resistance.
The low-carbon chemistry is particularly relevant to welded fabrication.
During welding, the heat-affected zone experiences a thermal cycle that can change microstructure.
If susceptible carbides or other precipitates form excessively at grain boundaries, local corrosion resistance can deteriorate.
C276's low carbon and controlled silicon chemistry helps reduce this concern.
This is one reason the alloy has become important for welded chemical-processing equipment.
However, chemical composition is only one part of weldability.
Successful C276 fabrication also depends on:
Welding process
Filler metal
Heat input
Interpass temperature
Joint preparation
Surface cleanliness
Shielding gas
Welding procedure qualification
For example, Haynes specifies ERNiCrMo-4 for GTAW/GMAW C276 filler-metal applications and ENiCrMo-4 for shielded-metal-arc applications.
One useful way to understand C276 chemistry is to compare it with 316L stainless steel.
C276 contains much higher levels of nickel, molybdenum, and tungsten, while its carbon and silicon levels are tightly controlled.
The result is a fundamentally different alloy design.
Characteristic | Hastelloy C276 | 316L Stainless Steel |
Alloy family | Nickel-based | Austenitic stainless steel |
Nickel | Balance | Much lower |
Chromium | 14.5–16.5% | Approximately 16–18% |
Molybdenum | 15.0–17.0% | Approximately 2–3% |
Tungsten | 3.0–4.5% | Not a principal alloying addition |
Carbon | ≤0.01% | ≤0.03% |
Main design objective | Severe corrosion resistance | General corrosion resistance and fabrication economy |
The comparison illustrates an important point:
C276 does not achieve its performance simply by increasing chromium.
Instead, it uses a nickel-rich matrix combined with high molybdenum, tungsten, chromium, and very low carbon and silicon.
Hastelloy C276 and Inconel 625 are both nickel-based corrosion-resistant alloys, but their chemistry is not identical.
C276 is characterized by:
15.0–17.0% Mo
14.5–16.5% Cr
3.0–4.5% W
4.0–7.0% Fe
Inconel 625, by comparison, uses a different alloying balance, notably with substantial niobium and molybdenum additions.
This difference in chemistry affects how the two alloys are selected.
C276 is particularly associated with severe chemical corrosion service, while Inconel 625 is widely used where a combination of corrosion resistance, mechanical strength, and elevated-temperature performance is required.
For a full engineering comparison, see Hastelloy C276 vs Inconel 625.
The fundamental alloy identity remains the same, but the applicable composition requirements depend on the product specification.
Hastelloy C276 is supplied in forms such as:
Pipe
Tube
Plate
Sheet
Strip
Bar
Forgings
Fittings
Welding products
ASTM B575, for example, covers plate, sheet, and strip made from low-carbon nickel-chromium-molybdenum alloys, including UNS N10276.
Other product forms are covered by different specifications.
Therefore, engineers should not assume that one generic C276 chemistry table replaces the requirements of every product standard.
When purchasing material, verify:
UNS designation
Product form
Applicable ASTM/ASME specification
Heat number
Chemical analysis
Mechanical properties
Heat-treatment condition
Required testing
Material certification
What is the main element in Hastelloy C276?
Nickel is the main element and forms the balance of the alloy. C276 also contains significant amounts of molybdenum, chromium, and tungsten.
How much molybdenum is in Hastelloy C276?
Hastelloy C276 contains 15.0–17.0 wt.% molybdenum under commonly specified wrought-alloy chemistry requirements.
How much chromium is in Hastelloy C276?
The specified chromium range is generally 14.5–16.5 wt.%.
How much tungsten is in Hastelloy C276?
C276 contains approximately 3.0–4.5 wt.% tungsten.
What is the carbon content of Hastelloy C276?
The carbon content is generally limited to 0.01 wt.% maximum for wrought C276 material.
Why is carbon kept low in Hastelloy C276?
Low carbon helps reduce the formation of carbide precipitates that can adversely affect corrosion resistance, particularly around welded regions.
Is Hastelloy C276 a nickel-chromium-molybdenum alloy?
Yes. More precisely, C276 is a nickel-chromium-molybdenum-tungsten corrosion-resistant alloy.
What is the UNS designation for Hastelloy C276?
The UNS designation is N10276.
Does Hastelloy C276 contain tungsten?
Yes. Tungsten is specified at approximately 3.0–4.5 wt.% in C276.
Is Hastelloy C276 composition the same as Inconel 625?
No. Both are nickel-based alloys, but their alloying systems differ. C276 is characterized by substantial molybdenum and tungsten, whereas Inconel 625 uses a different balance of alloying elements, including niobium.
For the broader technical picture, continue to the Ultimate Guide to Hastelloy C276, which connects composition with mechanical properties, corrosion resistance, temperature limits, welding, machining, applications, standards, and material selection.
