Alloy 800 / UNS N08800 / 1.4876 Forgings

What is Alloy 800 (UNS N08800)?

Alloy 800 is a single-phase austenitic iron–nickel–chromium alloy containing 30–35 % nickel and 19–23 % chromium with a minimum of 39.5 % iron, stabilised by small, deliberate additions of aluminium and titanium (0.15–0.60 % each). It was developed to give the high-temperature oxidation and carburisation resistance of a nickel alloy at a cost much closer to stainless steel, by using iron for the bulk of the matrix and spending the nickel only where it buys resistance to chloride stress corrosion cracking.

Three properties define how the alloy behaves in a forge shop and in service. First, it is solid-solution strengthened only; there is no precipitation-hardening reaction to exploit, so no ageing cycle exists and no H-condition or quench-and-temper cycle applies. Strength comes from the alloy content and from grain size; the delivered condition is simply solution annealed. Second, the ~32 % nickel content puts it comfortably above the roughly 20–25 % nickel threshold at which austenitic alloys stop being susceptible to chloride stress corrosion cracking, which is the single most common reason engineers move up from Type 304 or 316. Third, the chromium forms a tenacious Cr₂O₃ scale, anchored by the aluminium and titanium, that resists both oxidation and carbon pickup in hot process gases.

What Alloy 800 does not have is molybdenum. That absence sets its limit: in wet, chloride-bearing or acidic liquids where pitting and crevice attack govern rather than cracking, Alloy 800 offers little more than a good stainless steel, and Alloy 825 or Alloy 625 is the correct step up. Alloy 800 earns its place on the hot side, not the wet side.

What are the equivalent designations for Alloy 800?

Alloy 800 appears under at least eight names, and all of them describe the same 32Ni–21Cr–Fe chemistry. Which one you write on the purchase order matters legally and commercially: specifying the trademark restricts you to one producer, while specifying UNS N08800 or ASTM B564 opens the order to any qualified forge.

Sister grades: Alloy 800H = UNS N08810 / 1.4958; Alloy 800HT = UNS N08811 / 1.4959. They share every specification number above but add grain-size, carbon and Al+Ti requirements.

What is the difference between Alloy 800, 800H and 800HT?

All three grades share one base chemistry and differ in exactly three controlled variables: carbon content, grain size and the aluminium-plus-titanium total. Those three variables buy one thing, creep strength above about 593 °C. Below that temperature the three are metallurgically interchangeable in practice and Alloy 800 is the economical choice. Above it, only 800H and 800HT carry the code allowable stresses.

The mechanism is straightforward. Creep resistance in a solid-solution alloy comes largely from grain-boundary area: coarse grains have less of it, so there are fewer paths for grain-boundary sliding. Alloy 800H therefore mandates ASTM grain size 5 or coarser and a solution anneal well above 1100 °C to produce it, and narrows carbon to 0.05–0.10 % so that carbides pin those coarse boundaries instead of nucleating fine recrystallised grains. Alloy 800HT adds one further control, holding Al + Ti between 0.85 and 1.20 %, which sharpens the carbide and carbonitride distribution and removes most of the scatter in rupture life that 800H still shows.

What is the chemical composition of Alloy 800?

Per ASTM B564 and ASTM B408 for UNS N08800: nickel 30.0–35.0 %, chromium 19.0–23.0 %, iron 39.5 % minimum, carbon 0.10 % maximum, manganese 1.50 % maximum, sulfur 0.015 % maximum, silicon 1.0 % maximum, copper 0.75 % maximum, aluminium 0.15–0.60 % and titanium 0.15–0.60 %. Iron is not a residual here; it is a specified major constituent with a floor, which is what makes this an Fe–Ni–Cr alloy rather than a nickel-base one.

Jiangyin Jiangnan Metal Co., Ltd. melts Alloy 800 forging stock by EAF + AOD/VOD + ESR, with vacuum routes available where a customer specification calls for them. Full ladle and product analysis is reported on the EN 10204 certificate against every specification named on the order.

What are the mechanical properties of Alloy 800 forgings?

In the solution-annealed condition, ASTM B564 requires a minimum tensile strength of 520 MPa (75 ksi), a minimum 0.2 % offset yield strength of 205 MPa (30 ksi) and a minimum elongation of 30 % for UNS N08800 forgings. Those are floors, not expectations, hot-finished annealed forgings normally test appreciably above them, and the certificate reports what the material actually did.

What are the physical properties of Alloy 800?

The density of Alloy 800 is 7.94 g/cm³ (0.287 lb/in³) and its melting range is 1357–1385 °C (2475–2525 °F). Two other numbers matter more than engineers expect: thermal conductivity is low, about 11.5 W/m·K at room temperature, and the coefficient of thermal expansion is high for a heat-resisting material at about 14.4 × 10⁻⁶/°C. Together they mean thick Alloy 800 sections build steep thermal gradients and correspondingly large thermal stresses during heating and quenching, which is exactly why forging and annealing practice for this alloy is written around soak times rather than surface temperature.

Values are published typical figures for wrought, annealed Alloy 800 and are given for engineering screening. For code design use the property tables of ASME BPVC Section II Part D or the applicable EN standard.

How does Alloy 800 behave at elevated temperature?

Alloy 800 keeps a protective oxide and useful short-term strength well beyond 800 °C, but its design strength collapses much earlier, because above roughly 593 °C the governing property stops being yield strength and becomes creep-rupture strength. That change of governing property, not any sudden metallurgical event, is what puts the 1100 °F line on every specification sheet in this family.

Oxidation and carburisation

The chromia scale on Alloy 800 remains adherent through thermal cycling because the aluminium and titanium additions form internal oxide pegs that key the scale to the substrate. This is why the alloy outperforms plain 20Cr–30Ni stainless steels such as AISI 330 in cyclic furnace duty even where their static oxidation rates look similar. The same scale is a barrier to carbon, which is the reason Alloy 800 and its H/HT variants dominate ethylene pyrolysis and steam-reformer hardware, where the process gas would carburise a stainless steel into brittle uselessness within a campaign.

Sensitisation and the 540–760 °C band

Held between about 540 and 760 °C, Alloy 800 will precipitate chromium carbides on grain boundaries and leave chromium-depleted zones behind them, exactly as an unstabilised austenitic stainless steel does. The titanium addition ties up much of the carbon as TiC and greatly reduces the effect, but it does not eliminate it. Where a part will see that band and a subsequent aqueous or acidic environment, specify a stabilising anneal and say so on the order.

Creep-rupture and the code ceiling

Time-dependent behaviour is where the grade split earns its keep. At 815 °C the 100 000-hour rupture strength of coarse-grained 800H is several times that of a fine-grained Alloy 800 heat from the same chemistry band. ASME therefore lists allowable stresses for N08810 and N08811 up to about 899 °C (1650 °F), while N08800 is normally used only to about 593 °C in pressure-retaining service. Outside code work, in furnace fixtures, retorts, muffles, radiant tube supports and heat-treatment baskets, plain Alloy 800 is used far hotter, because there the failure mode is scaling and distortion rather than creep rupture under a pressure load.

How corrosion-resistant is Alloy 800?

Alloy 800's corrosion case rests on two things it does exceptionally well and one it does not do at all: it resists chloride stress corrosion cracking and high-temperature oxidation and carburisation, and it has no molybdenum, so it offers only modest resistance to pitting, crevice attack and reducing acids. Selecting it correctly is mostly a matter of identifying which of those three is your governing threat.

Chloride stress corrosion cracking

This is the classic reason to move up from Type 304 or 316. Susceptibility to chloride SCC in austenitic alloys peaks around 8–12 % nickel and falls away steeply above roughly 20–25 %. At about 32 % nickel, Alloy 800 is substantially resistant in hot chloride waters and in the boiling magnesium chloride test that destroys 304 in hours. It is resistant, not immune: at high temperature with concentrating chlorides and high stress it can still crack, and caustic environments impose their own limits.

Aqueous and acid service

In oxidising acids such as nitric, Alloy 800 performs well thanks to its chromium. In reducing acids (sulfuric, phosphoric, hydrochloric) it performs poorly, because reducing conditions strip the passive film and there is no molybdenum to help repassivate. In chloride-bearing process liquids, pitting resistance is comparable to a plain 20Cr austenitic stainless. This is precisely the gap Alloy 825 was created to fill, by adding about 3 % molybdenum and 2 % copper to the same basic matrix.

High-temperature gases

In oxidising and carburising atmospheres Alloy 800 is a benchmark material. In strongly sulfidising gases it is less good: nickel-rich alloys form low-melting nickel–sulfur eutectics, and at high temperature a high nickel content becomes a liability rather than an asset. Where sulfur dominates, a higher-chromium, lower-nickel material is usually the better answer.

How is Alloy 800 forged and heat treated?

Alloy 800 is hot worked between roughly 1200 °C and 900 °C, with heavy reduction taken from 1200 down to about 1010 °C and finishing passes below that, and it is then solution annealed at 955–980 °C and cooled rapidly. The window is narrower than any carbon or alloy steel, and the two ends of it fail in different ways: too hot and the alloy tears at the grain boundaries, too cold and it work-hardens faster than the press can move it.

The hot-working window in practice

Alloy 800 is roughly twice as stiff to deform as a carbon steel at the same temperature, and it loses heat quickly into the dies because its own conductivity is low. Both facts push practice in the same direction: fewer, heavier blows, generous reheats, and dies preheated rather than cold. We schedule reheats so that no pass finishes below about 900 °C; below that the alloy work-hardens sharply and surface cracking becomes likely on the next blow rather than the current one, which is what makes the defect so easy to miss on the shop floor.

Grain size is a deliverable, not an accident

Because the alloy is not age-hardenable, everything the customer will measure (strength, ductility, creep behaviour, ultrasonic attenuation) traces back to the final grain size, and that is set by the amount of strain in the last passes and the annealing temperature that follows. A forging finished with very light passes and then annealed hot will come out coarse and quiet under ultrasound; one finished with heavy strain and annealed cold will come out fine and strong but noisy. For plain Alloy 800 we aim for a uniform fine-to-medium grain; for 800H and 800HT the deliverable inverts, and ASTM 5 or coarser becomes a pass/fail requirement.

Solution annealing

Alloy 800 is annealed at 955–980 °C, held long enough to bring the centre of the section to temperature, and cooled quickly enough to pass through the 760–540 °C carbide precipitation band without dwelling in it. Water quenching is normal for heavy sections; air cooling is acceptable for thin ones. Alloy 800H and 800HT are annealed far hotter, typically 1120–1180 °C, precisely to grow the grain that plain Alloy 800 is annealed to avoid.

How is Alloy 800 welded and machined?

Welding

Alloy 800 is readily welded by GTAW, GMAW, SMAW and SAW, and welding is not the difficult part of using it. The filler choice is, and the usual mistake is reaching for a matching composition. Over-alloyed nickel fillers are preferred: ERNiCr-3 (Alloy 82) for gas-shielded processes and ENiCrFe-3 (Alloy 182) for covered electrodes. They are used because a matching Fe–Ni–Cr weld metal is prone to hot cracking and gives away high-temperature strength at the joint. For service above about 550 °C, ERNiCrCoMo-1 (Alloy 617 filler) is sometimes specified where the joint must match the parent creep strength.

Preheat is not required. Interpass temperature is normally held below about 150 °C, heat input kept low, and weave restricted. Nickel alloys have sluggish weld pools that reward a stringer technique. Post-weld heat treatment is generally unnecessary for Alloy 800 unless the code or a subsequent corrosive service calls for stress relief or a stabilising anneal. Joint surfaces and 25 mm either side must be clean and free of sulfur-bearing contamination before striking an arc.

Machining

Alloy 800 machines like a tough austenitic stainless: it work-hardens, it is gummy, and it punishes hesitation. Cutting speeds around 15–30 m/min with carbide tooling are typical for turning in the annealed condition. The governing rules are positive rake, sharp edges, rigid setups, generous depth of cut so the tool stays under the work-hardened layer from the previous pass, heavy flood coolant, and never letting the tool dwell in the cut. Chip control needs deliberate breakers; the alloy produces long stringy chips otherwise. Where a part will be finish-machined by the customer, we normally supply it rough machined with allowance so that the hardened skin from forging and descaling has already been removed.

What forged forms of Alloy 800 are available?

Jiangyin Jiangnan Metal Co., Ltd. produces Alloy 800 as seamless rolled rings, contoured rings, forged discs and hubs, shafts and spindles, flanges, tube sheets, sleeves, bushings, hollow cylinders, blocks and bars, all to customer drawing and to ASTM B564 / ASME SB-564. The route is chosen by geometry: ring rolling wherever a circumferential grain flow helps, open-die forging for long or heavy sections, and upsetting for short, large-diameter blanks.

Production capability for Alloy 800 forgings

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory operating 1, 3, 5 and 9 tonne forging hammers, a 5 000 tonne hydraulic press and 3 m and 6 m seamless ring-rolling mills, staffed by around 460 people including 9 senior and 32 intermediate engineers. Across the grade range this covers diameters from 80 mm to 6 000 mm, lengths to 12 000 mm and single-piece weights to 15 000 kg.

Inspection and test equipment

Which standards and quality documents apply to Alloy 800 forgings?

For forgings the governing specification is ASTM B564 / ASME SB-564, UNS N08800. Everything else on a typical order, ultrasonic acceptance, certification level, supplementary testing, is layered on top of it, and each layer needs to be named explicitly or it will not be performed.

How do you specify an Alloy 800 forging order?

Seven lines make an Alloy 800 enquiry unambiguous. Miss any one of them and the quotation, the certificate and the delivered part can each be technically correct while still failing your receiving inspection.

1. State the grade generically. Write UNS N08800 / ASTM B564, not the INCOLOY trademark. Add W.Nr. 1.4876 for European projects and NCF 800 for Japanese supply chains, and any qualified forge can legally supply you.
2. Confirm 800 against 800H and 800HT. If any part of the duty sits above about 593 °C, or the part is code-stamped for creep service, specify N08810 or N08811 instead. This is the single decision that most often goes wrong.
3. Provide the drawing and name the forging route. Send a 2D drawing or 3D model with machining allowance, and say whether you want a seamless rolled ring, an open-die disc, an upset block or a bar. A ring-rolled part has circumferential grain flow that a disc sawn from bar cannot reproduce.
4. State the delivery condition. For Alloy 800 that is solution annealed; there is no ageing or tempering step to specify. Say whether the part ships as-forged with allowance, rough machined, or finish machined.
5. Define the NDE. Name the ultrasonic standard and acceptance class (ASTM A388, EN 10228-3 or SEP 1921) and add penetrant examination to ASTM E165 for machined sealing faces. For tube sheets, add ligament tolerance and hole-pattern requirements.
6. Specify certification. EN 10204 3.1 for a standard mill certificate, or 3.2 where a third party must witness. Name the inspection body at enquiry stage.
7. Give quantity, delivery terms and destination. Piece count, required date, Incoterms and destination port. Email it to sales@steelforgepieces.com and you will have a price and a lead time within 24 hours.

Ten specification errors that cost time on Alloy 800 orders

Compiled from enquiries and post-delivery reviews. Every one of them is free to fix at the specification stage and expensive to fix at receiving inspection.

Drawing callout template for Alloy 800

Copy this block into the material note of your drawing and adjust the bracketed values. It removes most of the ambiguity that generates technical queries.

MATERIAL   : UNS N08800 per ASTM B564 / ASME SB-564
             (also satisfies W.Nr. 1.4876 / X10NiCrAlTi32-20,
              DIN 17460, EN 10095, JIS NCF 800, BS NA 15)
CONDITION  : Solution annealed 955–980 °C, cooled rapidly through 760–540 °C
             Alloy is NOT age-hardenable, no hardness range is specified
MECHANICAL : Rm ≥ 520 MPa (75 ksi) · Rp0.2 ≥ 205 MPa (30 ksi) · A ≥ 30 %
             Test orientation: [longitudinal / tangential] per ASTM B564
FORGING    : Route [seamless rolled ring / open-die disc / upset block]
             Forging ratio ≥ 3:1 · finishing temperature ≥ 900 °C
GRAIN SIZE : [Not specified for N08800; mandatory ASTM 5 or coarser if 800H/800HT]
NDE        : UT per [ASTM A388 / EN 10228-3 / SEP 1921], class [ ]
             PT per ASTM E165 on machined sealing surfaces
             MT NOT APPLICABLE, material is non-magnetic
CERT       : EN 10204 3.1  //  3.2 witnessed by [Lloyd's / DNV / BV / ABS / TÜV]
SURFACE    : Ra ≤ [1.6] µm on sealing faces · Ra ≤ [3.2] µm elsewhere
MARKING    : Heat number, grade, specification, drawing number, low-sulfur,
             low-halide marking materials only

Where is Alloy 800 used?

Alloy 800 is specified wherever a stainless steel would fail by oxidation, carburisation or chloride stress corrosion cracking, but the temperature stays low enough that creep design is not yet the governing case. That description covers a surprisingly large slice of process industry hardware.

Glossary

Alloy 800

Common name for the solid-solution iron–nickel–chromium alloy designated UNS N08800, nominally 32 % Ni, 21 % Cr, balance Fe with Al and Ti additions.

UNS N08800

The generic Unified Numbering System designation. The correct thing to write on a drawing or purchase order.

W.Nr. 1.4876

German Werkstoff number for Alloy 800, designated X10NiCrAlTi32-20 in DIN 17460 and X8NiCrAlTi32-21 in EN 10095.

INCOLOY®

Registered trademark of Special Metals Corporation. Not a specification, and not a term any independent producer can sell under.

Solid-solution strengthening

Strengthening by dissolved alloying elements distorting the lattice, rather than by precipitates. It is why Alloy 800 has no ageing cycle and no H-condition.

Solution annealing

Heating to 955–980 °C for Alloy 800 and cooling rapidly, to dissolve carbides, recrystallise the forged structure and restore corrosion resistance.

Creep-rupture strength

The stress that causes fracture after a stated time at a stated temperature, normally quoted at 10 000 or 100 000 hours. It governs design above about 593 °C.

Sensitisation

Chromium carbide precipitation on grain boundaries between about 540 and 760 °C, leaving chromium-depleted zones open to intergranular attack.

Carburisation

Carbon pickup from a hot process gas, forming brittle internal carbides. Alloy 800 resists it through a chromia scale keyed to the metal by Al and Ti.

Chloride stress corrosion cracking

Branching transgranular cracking of austenitic alloys under tensile stress in hot chloride environments. Resistance rises steeply above about 25 % nickel, the reason Alloy 800 exists.

Seamless rolled ring

A ring produced by piercing an upset billet and expanding it on a ring mill, giving continuous circumferential grain flow and no weld seam.

Forging ratio

Starting cross-section divided by finished cross-section, a measure of how thoroughly the as-cast structure has been worked out.

Ruling section

The thickest part of a forging, which sets soak time in every heat-treatment calculation.

ASTM grain size 5

A grain-size number per ASTM E112; lower numbers mean coarser grains. "5 or coarser" is the mandatory requirement for 800H and 800HT.

EN 10204 3.1

A material certificate issued by the manufacturer's independent quality department, reporting tests on the delivered material.

EN 10204 3.2

The same certificate, countersigned by an independent third-party inspector who witnessed the testing.

Standards and references

Chemistry, mechanical property, heat-treatment and corrosion data on this page are drawn from the published standards and engineering references below. Test results reported on our material certificates are independent and traceable to our own calibrated equipment.

1. ASTM B564/B564M, Standard Specification for Nickel Alloy Forgings, ASTM International, West Conshohocken, PA.
2. ASTM B408, Standard Specification for Nickel-Iron-Chromium Alloy Rod and Bar, ASTM International.
3. ASTM B409, Standard Specification for Nickel-Iron-Chromium Alloy Plate, Sheet, and Strip, ASTM International.
4. ASTM B407, Standard Specification for Nickel-Iron-Chromium Alloy Seamless Pipe and Tube, ASTM International.
5. ASTM B163, Standard Specification for Seamless Nickel and Nickel Alloy Condenser and Heat-Exchanger Tubes, ASTM International.
6. ASTM B366, Standard Specification for Factory-Made Wrought Nickel and Nickel Alloy Fittings, ASTM International.
7. ASME Boiler and Pressure Vessel Code, Section II Part D (Properties) and Section VIII Division 1, latest edition, ASME, New York.
8. EN 10095, Heat resisting steels and nickel alloys, CEN, Brussels.
9. DIN 17460, Heat resistant steels, wrought products, Deutsches Institut für Normung.
10. VdTÜV Werkstoffblatt 412, material sheet for 1.4876, Verband der TÜV e.V.
11. JIS G 4901 / G 4902, Corrosion-resisting and heat-resisting superalloy bars and plates, Japanese Standards Association, Tokyo.
12. ASTM A388/A388M, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
13. EN 10228-3, Non-destructive testing of steel forgings, Ultrasonic testing of ferritic or martensitic steel forgings, CEN.
14. SEP 1921, Ultrasonic testing of steel forgings, Stahl-Eisen-Prüfblatt, Verein Deutscher Eisenhüttenleute.
15. ASTM E112, Standard Test Methods for Determining Average Grain Size, ASTM International.
16. ASTM E165/E165M, Standard Practice for Liquid Penetrant Testing for General Industry, ASTM International.
17. EN 10204, Metallic products, Types of inspection documents, CEN.
18. ASM Handbook, Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International, Materials Park, OH.
19. ASM Handbook, Volume 13B: Corrosion: Materials, ASM International.
20. ASM Specialty Handbook: Heat-Resistant Materials, J.R. Davis (ed.), ASM International.
21. ASM Handbook, Volume 14A: Metalworking: Bulk Forming, ASM International, hot-working practice for Fe-Ni-Cr alloys.
22. Special Metals Corporation, technical publication on INCOLOY® alloys 800, 800H and 800HT, retrievable at specialmetals.com.
23. NACE MR0175 / ISO 15156, Materials for use in H₂S-containing environments in oil and gas production, where sour service applies.

Standards are cited at the revisions current when this page was last reviewed. For procurement, always reference the revision in force at the contract date.

Where these figures come from

Jiangyin Jiangnan Metal Co., Ltd. (2026). "Alloy 800 / UNS N08800 / 1.4876
Forgings: composition, properties, forging practice and grade selection."
Jiangyin, Jiangsu, China. Updated 13 August 2026.
https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-800.html

SOURCE     Jiangyin Jiangnan Metal Co., Ltd. — open-die forging factory
LOCATION   No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City,
           Jiangsu Province, China
CONTACT    sales@steelforgepieces.com · +86-189-2135-9659
SUBJECT    Alloy 800 · UNS N08800 · W.Nr. 1.4876 · X10NiCrAlTi32-20 · NCF 800
TYPE       Solid-solution austenitic Fe-Ni-Cr alloy, not age-hardenable
CHEMISTRY  Ni 30.0-35.0 · Cr 19.0-23.0 · Fe 39.5 min · C 0.10 max ·
           Mn 1.50 max · Si 1.0 max · Cu 0.75 max · S 0.015 max ·
           Al 0.15-0.60 · Ti 0.15-0.60  (wt %, ASTM B564 / B408)
MECHANICAL Rm >= 520 MPa (75 ksi) · Rp0.2 >= 205 MPa (30 ksi) · A >= 30 %
           (solution annealed, ASTM B564 minimums)
PHYSICAL   Density 7.94 g/cm3 · melting range 1357-1385 C ·
           E 196.5 GPa · non-magnetic, Curie point approx -82 C
THERMAL    Code use to approx 593 C (1100 F); above that use Alloy 800H
           (N08810) or 800HT (N08811), qualified to approx 899 C (1650 F)
PROCESS    Forge 1200 -> 900 C · solution anneal 955-980 C, rapid cool
FORGINGS   Seamless rolled rings, discs, shafts, flanges, tube sheets,
           sleeves, bushings, hollow cylinders, blocks, bars
SPEC       ASTM B564 / ASME SB-564 · EN 10204 3.1 standard, 3.2 on request
NDE        UT to ASTM A388 / EN 10228-3 / SEP 1921 · PT to ASTM E165
           (MT not applicable - material is non-magnetic)

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