Incoloy 800HT Forgings UNS N08811 · W.-Nr. 1.4959 · X8NiCrAlTi32-21. Forged rings, flanges, bars, discs and shafts to ASTM B564.

§1 · Identification

What Incoloy 800HT is

Incoloy 800HT is the high-temperature variant of the alloy 800 family. Its base chemistry matches alloy 800 and 800H at about 32 % nickel, 21 % chromium, balance iron. Two things are then tightened. Carbon is held between 0.06 % and 0.10 %, and aluminium plus titanium is held between 0.85 % and 1.20 %. The alloy is solution annealed at 1149 °C (2100 °F) minimum, which coarsens the grain to ASTM No. 5 or coarser.

The coarse grain and the controlled Al + Ti give much better creep and stress-rupture behaviour above 593 °C than alloy 800. ASME allowable design stresses for N08811 are correspondingly higher. Below about 593 °C there is usually no benefit and alloy 800 is the cheaper buy.

Incoloy 800HT also resists oxidation, carburisation and nitriding. Unlike many austenitic stainless steels, it does not become embrittled after long exposure in the 650 to 870 °C range. Aqueous corrosion resistance is only moderate. It is a heat-resisting alloy, not a wet-corrosion alloy. For chloride or acid service, Incoloy 825 or Hastelloy C-276 are the usual alternatives.

Designations and equivalents

INCOLOY is a trademark of the Special Metals group of companies. Jiangyin Jiangnan Metal Co., Ltd. is an independent forging manufacturer and is not affiliated with the trademark holder. The designation is used here to identify the alloy specification only.

§2 · Chemistry

Chemical composition of Incoloy 800HT

The table below gives composition limits for UNS N08811 as specified in ASTM B564 and ASTM B408. Iron is determined arithmetically by difference. The two rows that distinguish 800HT from 800H are highlighted.

The individual Al and Ti ranges are common to the N08800, N08810 and N08811 family. The 0.85 to 1.20 % Al + Ti requirement applies to N08811 only, and in practice mills aim for the upper half of the Al and Ti bands to satisfy the sum. For contractual purposes, work from the current edition of the governing standard.

Jiangyin Jiangnan Metal Co., Ltd. melts Incoloy 800HT forging stock by EAF plus AOD or VOD refining, with ESR remelting available where a tighter inclusion rating or improved transverse ductility is specified.

§3 · Mechanical data

Mechanical properties

Room-temperature minimums for solution-annealed material to ASTM B564 and B408 are given below. Actual mill results on forged sections normally sit well above these minimums. For a creep-governed design it is the elevated-temperature and rupture data that decide the section, not the room-temperature tensile.

Behaviour at temperature

Strength falls progressively with temperature, as expected for an austenitic alloy. Short-term strength is much the same as alloy 800. Rupture life is not. At 815 °C the 100 000 hour rupture strength of 800HT is about double, and the ASME allowable stress tables follow. Rupture data are design-critical and edition-dependent, so take allowable stresses from the governing ASME BPVC edition. Do not take them from a supplier datasheet, this one included.

• Normal specification range is above 593 °C (1100 °F), where creep and rupture govern.
• ASME BPVC tabulates allowable stresses for N08811 up to approximately 899 °C (1650 °F), depending on section and edition.
• Oxidation resistance for non-pressure furnace hardware extends to about 1093 °C (2000 °F).
• No embrittlement after long exposure in the 650 to 870 °C band, unlike many austenitic stainless steels.

§4 · Physical data

Physical properties

Physical properties are typical values for the alloy 800 family and vary slightly between published sources. Use them for design estimation, not for acceptance.

§5 · Grade selection

Incoloy 800 vs 800H vs 800HT: which grade to specify

These three grades are confused on drawings and purchase orders more often than any other set in the nickel alloy range, and the wrong one in a reformer or cracking furnace can mean premature creep failure. The base composition is identical. Everything turns on carbon, Al + Ti, and the anneal temperature.

A practical note on purchasing. Much commercial stock is dual-certified 800H/800HT, because a heat that meets the tighter 800HT limits automatically satisfies 800H. The reverse is not true. If your design relies on 800HT allowable stresses, state N08811 explicitly on the purchase order and require the certificate to show the Al + Ti sum and the actual anneal temperature, not just the grade name.

§6 · Product range

Incoloy 800HT forged products

Jiangyin Jiangnan Metal Co., Ltd. produces the following Incoloy 800HT forms by open-die forging and ring rolling, in the solution-annealed condition, rough machined or finish machined to drawing. Dimensional limits are set by press and ring mill capacity, so send your sizes and we will confirm what can be made in one piece.

§7 · Manufacturing route

How we forge Incoloy 800HT

Alloy 800HT is awkward to forge. It work-hardens quickly and the hot working window is narrow. Everything then depends on finishing with a coarse, uniform grain. The sequence below is the route we follow.

1. Melting and ingot supply EAF plus AOD or VOD refined, with ESR remelting where specified. Heat chemistry is verified against the N08811 limits, including the Al + Ti sum, before the ingot is released to the forge.
2. Heating Soaked to 1180 to 1205 °C. Sulphur attacks nickel alloys at temperature, so furnace atmosphere and fuel sulphur are controlled and stock is kept clean of grease and marking paint.
3. Open-die forging Worked between about 1205 °C and a finishing temperature above 980 °C. Reheats are scheduled rather than improvised. Finishing too cold refines the grain and destroys the creep properties the grade was bought for.
4. Ring rolling For seamless rolled rings, the pierced blank is rolled radially and axially to section. This gives continuous circumferential grain flow with no weld seam.
5. Solution annealing 1149 °C (2100 °F) minimum, held to section, then cooled. Actual furnace temperature and hold time are recorded on the certificate. Alloy 800HT is not age-hardened, so any ageing step in a specification should be queried.
6. Rough machining Scale removal and machining to the agreed allowance, so ultrasonic examination is performed on a clean, representative surface.
7. Testing and certification Chemistry, tensile, grain size, ultrasonic and any additional customer-specified examination, issued under EN 10204 3.1 or third-party 3.2.

Open-die forging is used for this grade because it produces grain flow that follows the part contour and closes casting porosity. A part machined from plate has cut fibre across the highest-stressed section. A forging does not.

§8 · Compliance

Standards and certification

Third-party witness and certification by BV, SGS, LR, DNV, TÜV or a client-nominated inspector can be arranged on request.

§9 · Where it is used

Applications for Incoloy 800HT forgings

Petrochemical and refining

Steam methane reformer hardware, pigtail and outlet manifold components, ethylene cracking furnace fittings, hydrocarbon processing columns and towers, transfer-line exchanger parts, and forged nozzles and flanges on high-temperature vessels.

Heat exchangers and pressure equipment

Tube sheets, channel and shell flanges, forged shells, forged tubes and pipe sections, and nozzle reinforcement for shell and tube exchangers, air receivers, preheaters and process modules operating in the creep range.

Power generation

Superheater and reheater headers and supports, forged rings and discs for gas turbine and compressor auxiliaries, and hangers and fixtures inside high-temperature boiler enclosures.

Industrial furnaces and heat treatment

Retorts, muffles, radiant tube supports, carburising and nitriding fixtures, roller hearth components, quench fixtures and trays. This is service where repeated thermal cycling and carburising atmospheres would consume a stainless steel.

Valves and rotating equipment

Valve bodies, bonnets, stems, seat rings and blocks for ball, gate, globe, check and plug valves in high-temperature lines. Also forged shafts, spindles, gears and rings for chemical pumps, plunger pumps, gas compressors, turbines and gearboxes.

Other sectors

Nuclear steam generator components, coal gasification internals, cement and sugar mill hot-end hardware, pulp and paper digester components, and pharmaceutical and biochemical process equipment requiring high-temperature stability.

§10 · Fabrication

Machining, forming and welding notes

Machining

Alloy 800HT machines like a tough austenitic material and work-hardens rapidly. The same rules as 316 and 321 apply, only tighter. Rigid setups, sharp positive-rake tools, a heavy constant feed that stays under the hardened skin, and no dwelling. Speeds are lower and feeds heavier than for carbon steel. Use water-based coolant for turning, milling and grinding, and heavy sulphurised or chlorinated lubricant for drilling, tapping, boring and broaching. Degrease thoroughly afterwards, because residual sulphur embrittles nickel alloys at temperature. Against free-machining stainless grades such as 303 and 430F, expect materially lower metal removal rates and shorter tool life.

Forming

Both hot and cold forming are practical. Hot working range is about 870 to 1205 °C, and heavy reduction should be taken in the upper part of that range. Cold-formed parts should be re-annealed at 1149 °C minimum if the design depends on 800HT creep properties, since cold work refines grain and raises strength at the expense of rupture life.

Welding

Alloy 800HT is welded by GTAW, GMAW, SMAW and SAW. Filler selection depends on service temperature. ERNiCr-3 is the common choice, with ERNiCrCoMo-1 used for the hottest service. Keep heat input and interpass temperature low, avoid heavy weaving, and clean the joint of sulphur-bearing marker, grease and cutting fluid before striking an arc. Sulphur contamination is the usual cause of hot cracking in this alloy family. Where full creep performance is required across the joint, solution anneal after welding.

§11 · Quality

Testing and inspection

• Chemical analysis. Spectrometric verification of the heat, including the Al + Ti sum, reported on the certificate.
• Tensile testing. Room temperature to ASTM E8/E8M. Elevated-temperature tensile to ASTM E21 on request.
• Grain size. ASTM E112, confirming No. 5 or coarser as required for N08811.
• Ultrasonic examination. ASTM A388, EN 10228-3 or SEP 1921 to the agreed quality class.
• Liquid penetrant. ASTM E165 or EN 10228-2 on machined surfaces where specified.
• Hardness. Brinell to ASTM E10.
• Impact testing. Charpy V-notch to ASTM E23 when required by the design code.
• Intergranular corrosion. ASTM A262 practice as agreed, for aqueous-service applications.
• Dimensional report. Against the approved drawing, with machining allowance recorded.
• Positive material identification. Handheld XRF on request before shipment.

Every consignment ships with a mill test certificate to EN 10204 3.1, or 3.2 with third-party endorsement where the purchase order calls for it. Test reports record the actual solution-annealing temperature, which is the single most important process record for an 800HT forging.

§12 · Supplier

About the manufacturer

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, in the Yangtze River Delta forging cluster, some 150 km from the Port of Shanghai. The works produces open-die forgings and seamless rolled rings in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, and exports to engineering contractors, valve and pump builders, pressure vessel fabricators and OEMs worldwide.

For nickel alloys, the company forges the Incoloy, Inconel, Monel, Hastelloy, Nimonic and Waspaloy families, supplying rings, flanges, bars, discs, shafts, sleeves, tube sheets and machined components to ASTM, ASME, EN and DIN specifications.

§13 · Ordering

How to request a quotation

Send a drawing, or the rough dimensions, and we will quote. To price accurately at the first pass, include the following.

1. Grade and specification State UNS N08811 as well as the trade name, plus the governing standard (ASTM B564 / ASME SB-564) and any client specification.
2. Geometry Drawing in PDF, DWG or STEP. For simple shapes, OD × ID × height, or diameter × length, with the machining allowance you want on each face.
3. Delivery condition As-forged, solution annealed, rough machined or finish machined.
4. Quantity and schedule Piece count and required delivery date. Prototype and production quantities are both accepted.
5. Testing scope Ultrasonic class, impact testing, PMI, intergranular corrosion or any additional examination.
6. Certification EN 10204 3.1 or 3.2, and the name of the inspection body if third-party witness is required.
7. Commercial terms Incoterms and destination port for freight calculation.

Related grades

Other nickel alloys we forge

Same forging route, same certification. If 800HT is not the right grade for your service, these are the usual alternatives.

• Incoloy 800
• Incoloy 800H
• 1.4959
• 1.4958
• Incoloy 825
• Incoloy 901
• Incoloy 925
• Incoloy 926
• Incoloy 945
• Incoloy 890
• Inconel 600
• Inconel 601
• Inconel 617
• Inconel 625
• Inconel 690
• Inconel 693
• Inconel 706
• Inconel 718
• Inconel 725
• Inconel X-750
• 2.4816
• 2.4856
• Hastelloy C-276
• Hastelloy C-22
• Hastelloy C-4
• Hastelloy C-2000
• Hastelloy X
• Hastelloy B-2
• Hastelloy B-3
• Monel 400
• Monel K-500
• Monel R-405
• Nimonic 75
• Nimonic 80A
• Nimonic 90
• Nimonic 105
• Nimonic 115
• Nimonic 263
• Nimonic 901
• Waspaloy
• Haynes 230
• Haynes 188
• Haynes 25
• Rene 41
• Udimet 500
• Udimet 520
• Udimet 720
• MP35N
• MP159
• Multimet N155
• Alloy 59
• Alloy 602
• NI-SPAN-C 902
• UNS N07208
• UNS N07252
• UNS N07022
• Nimonic 81
• Nimonic 86

Product families: forged disks, forged components, all open-die forgings.