Incoloy 800H (UNS N08810) – Nickel-Iron-Chromium Alloy for High-Temperature Creep Service

Short Description:

Incoloy 800H (UNS N08810 / W.Nr. 1.4958 / NS112) is a nickel-iron-chromium alloy specifically designed for high-temperature creep-resistant service above 815°C (1500°F). Womic Steel supplies Incoloy 800H in multiple product forms including seamless pipe, welded pipe, steel bar, steel plate, steel coil, strip, flanges, fittings, forgings, and valves for petrochemical processing, ethylene cracking, steam reforming, heat treating, and nuclear power generation applications.

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Incoloy 800H is the high-temperature variant of Incoloy 800 with controlled carbon content (0.05-0.10%) and a guaranteed fine grain structure (ASTM 5 or coarser) to optimize creep-rupture strength at elevated temperatures. The "H" designation signifies "High Temperature" creep service. Unlike standard Incoloy 800, which is suitable for general high-temperature service, Incoloy 800H provides significantly improved creep-rupture strength at temperatures above 815°C through precise chemistry control and grain size optimization. This makes it the preferred material for petrochemical reformer tubes, ethylene cracking furnace components, and other applications requiring long-term service at extreme temperatures.

Key characteristics include:

Superior creep-rupture strength at temperatures above 815°C
Excellent oxidation resistance up to 1093°C (2000°F)
Controlled carbon content (0.05-0.10%) for creep optimization
Guaranteed grain size (ASTM 5 or coarser) for improved creep resistance
Outstanding resistance to carburization and nitridation
Good resistance to nitric acid and chloride environments
Excellent weldability and fabricability

Chemical Composition

Element	Content (%)	Role
Nickel (Ni)	30.0 – 35.0	Corrosion resistance, austenite stabilizer
Chromium (Cr)	19.0 – 23.0	Oxidation resistance, forms protective Cr₂O₃ scale
Iron (Fe)	Balance (≥39.5)	Base element, cost-effective structural component
Carbon (C)	0.05 – 0.10	Creep strength, controlled to optimize high-temperature properties
Aluminum (Al)	0.15 – 0.60	Oxidation resistance, Al₂O₃ scale formation
Titanium (Ti)	0.15 – 0.60	Grain boundary strengthening, carbide former
Manganese (Mn)	≤ 1.50	Deoxidizer
Silicon (Si)	≤ 1.00	Deoxidizer
Copper (Cu)	≤ 0.75	Residual element
Sulfur (S)	≤ 0.015	Controlled impurity

Mechanical Properties

Room Temperature Properties (Annealed)

Property	ASTM Requirement	Typical Achieved
Tensile Strength	≥ 450 MPa (65 ksi)	450 – 510 MPa
Yield Strength (0.2% Offset)	≥ 170 MPa (25 ksi)	170 – 210 MPa
Elongation	≥ 30%	30 – 45%
Hardness	≤ 92 HRB	80 – 90 HRB
Density	7.94 g/cm³
Melting Range	1357 – 1385°C
Thermal Conductivity at 20°C	11.2 W/m·K
Coefficient of Thermal Expansion (20-100°C)	14.0 × 10⁻⁶/°C
Elastic Modulus	196 GPa

Creep-Rupture Strength – Incoloy 800H vs Standard 800

Temperature	Stress (MPa)	Rupture Life	Incoloy 800H	Incoloy 800 (Standard)
815°C	80	100 hours	✓	✓
815°C	60	1,000 hours	✓	✓
870°C	65	100 hours	✓	—
870°C	45	1,000 hours	✓	—
927°C	35	100 hours	✓	—
927°C	20	1,000 hours	✓	—
1000°C	20	100 hours	✓	—

Key Advantages of Incoloy 800H

Superior Creep-Rupture Strength – The "H" designation indicates Incoloy 800H has been specifically formulated for high-temperature creep service. With controlled carbon content (0.05-0.10%) and grain size (ASTM 5 or coarser), Incoloy 800H provides significantly improved creep-rupture strength compared to standard Incoloy 800 at temperatures above 815°C. At 870°C, the 1,000-hour creep-rupture strength is 45 MPa — substantially higher than standard 800.

Excellent Oxidation Resistance – Incoloy 800H forms a tightly adherent Cr₂O₃ oxide scale that provides excellent protection in oxidizing atmospheres up to 1093°C (2000°F). The aluminum addition (0.15-0.60%) further enhances oxidation resistance by contributing to a protective Al₂O₃ layer at the metal-oxide interface, improving scale adhesion and preventing spalling under thermal cycling conditions.

Controlled Grain Size – Incoloy 800H is produced with a guaranteed grain size of ASTM 5 or coarser. The coarser grain structure reduces grain boundary sliding at elevated temperatures, providing superior creep resistance. This is a key differentiator from standard Incoloy 800, which does not have specified grain size requirements.

Resistance to Carburization – In environments rich in carbon (ethylene cracking furnaces, steam reformers), Incoloy 800H resists carburization better than most other heat-resistant alloys. This prevents metal dusting and embrittlement, significantly extending tube life in petrochemical service where carbon steel tubes may fail within months.

Good Resistance to Nitric Acid and Chlorides – The high nickel content (30-35%) provides good resistance to chloride stress corrosion cracking, while the chromium content provides excellent resistance to nitric acid, making Incoloy 800H suitable for nitric acid plant equipment.

Excellent Weldability – Incoloy 800H can be readily welded using TIG, MIG, resistance welding, and other standard processes. Matching filler metal ERNiFeCr-1 (AWS A5.14) is recommended. Post-weld heat treatment is not required for most applications.

Incoloy 800H vs Incoloy 800 vs Incoloy 800HT

Property	Incoloy 800	Incoloy 800H	Incoloy 800HT
UNS	N08800	N08810	N08811
Werkstoff	1.4876	1.4958	1.4959
Carbon Content	≤ 0.10%	0.05 – 0.10%	0.06 – 0.10%
Grain Size	No specific	ASTM 5 or coarser	ASTM 5 or coarser
Ti/Al Ratio	No specific	No specific	≥ 5:1
Creep Strength	Good	Superior	Highest
Oxidation Resistance	Excellent	Excellent	Excellent
Primary Application	General high-temp	Creep-resistant	Highest creep-demanding

When to choose Incoloy 800H: Applications requiring long-term creep resistance at temperatures above 815°C, such as petrochemical reformers, ethylene cracking furnaces, and heat exchanger tubing where creep-rupture strength is critical.

When to choose Incoloy 800HT: Applications requiring the highest possible creep-rupture strength at elevated temperatures where the Ti/Al ratio ≥ 5:1 provides additional creep resistance beyond 800H.

Available Product Forms from Womic Steel

Seamless Pipe & Seamless Tube

Outside Diameter: 6mm – 350mm (1/4" – 14")
Wall Thickness: 1mm – 40mm (Schedule 5S to XXS)
Length: Up to 12m
Standards: ASTM B407, ASTM B829, ASME SB-407
Applications: Heat exchanger tubes, reformer tubes, furnace tubes, process piping, superheater tubing
Keywords: Incoloy 800H seamless pipe, UNS N08810 tube, 1.4958 pipe, alloy 800H seamless tube, reformer tube

Welded Pipe

Outside Diameter: 50mm – 1200mm (2" – 48")
Wall Thickness: 1.0mm – 25mm
Standards: ASTM B514, ASTM B515, ASME SB-514
Applications: Large-diameter process piping, furnace components, heat exchanger shells
Keywords: Incoloy 800H welded pipe, alloy 800H ERW pipe, large diameter nickel pipe

Steel Bar (Round, Square, Flat)

Diameter: 6mm – 400mm
Surface: Hot rolled, Bright (cold drawn), Ground, Turned
Standards: ASTM B408, ASME SB-408, AMS 5766
Applications: Valve stems, fasteners, shafts, machining stock, furnace rollers
Keywords: Incoloy 800H round bar, UNS N08810 bar stock, nickel alloy bar, AMS 5766

Steel Plate & Sheet

Thickness: 1mm – 100mm
Width: Up to 2500mm
Standards: ASTM B409, ASME SB-409, AMS 5871
Applications: Vessel shells, heat exchanger plates, structural components, flange blanks, furnace hearth plates
Keywords: Incoloy 800H plate, alloy 800H sheet, N08810 plate, high temperature alloy plate

Steel Coil & Strip

Thickness: 0.5mm – 6.0mm
Width: 10mm – 1500mm
Standards: ASTM B409
Applications: Formed components, bellows, expansion joints, thin-walled tubing
Keywords: Incoloy 800H coil, nickel alloy strip

Flanges & Pipe Fittings

Types: Weld Neck, Slip-On, Blind, Socket Weld, Threaded, Lap Joint
Sizes: 1/2" – 48" (DN15 – DN1200)
Pressure Rating: Class 150 – Class 2500
Standards: ASTM B564, ASME SB-564, ASME B16.5, ASME B16.47
Keywords: Incoloy 800H flanges, alloy 800H weld neck flange, N08810 fittings

Forgings

Types: Rings, disks, shafts, valve bodies, turbine components, custom geometries
Weight: Up to 5,000kg per piece
Standards: ASTM B564, ASME SB-564, AMS 5766
Keywords: Incoloy 800H forging, alloy 800H ring, forged block

Incoloy 800H Valves

Types: Ball valves, Gate valves, Globe valves, Check valves
Sizes: 1/2" – 24" (DN15 – DN600)
Pressure Rating: Class 150 – Class 2500
Temperature Range: -196°C to +815°C
Design Standards: API 608, API 6D, ASME B16.34
Seating: Stellite hardfaced, RPTFE
Actuation: Manual, Pneumatic, Electric
Applications: High-temperature process isolation, reformer feed lines, heat exchanger control

Applications of Incoloy 800H

Petrochemical Reforming and Cracking – Incoloy 800H is the standard material for reformer tubes in steam methane reformers (SMR), ethylene cracking furnace radiant tubes, pyrolysis furnace tubes, and outlet manifolds. At temperatures above 870°C, the alloy's creep-rupture strength extends tube life significantly compared to standard 800 or heat-resistant stainless steel.

Industrial Furnace Components – The alloy is used in radiant tubes, muffles, retorts, trays, baskets, hearth plates, furnace rollers, and thermocouple protection tubes in heat treating operations up to 1093°C.

Superheater and Reheater Tubing – Incoloy 800H is used in superheaters and reheaters for power generation and industrial processes requiring resistance to high-temperature oxidation and creep at temperatures above 815°C.

Nuclear Power – The alloy is used in nuclear steam generator tubing, intermediate heat exchangers, and reactor core components where high-temperature creep resistance and corrosion resistance are required.

Nitric Acid Plants – Incoloy 800H is used in nitric acid plant equipment where both high-temperature and acid resistance are required, including ammonia oxidizer tubes and tail gas heaters.

Ammonia Production – The alloy is used in ammonia synthesis converters and reformers requiring resistance to high-temperature hydrogen and nitrogen environments with creep resistance.

Standards & Specifications

Product Form	ASTM Standard	ASME Standard	AMS Standard
Seamless Pipe/Tube	ASTM B407	ASME SB-407	—
Welded Pipe	ASTM B514, ASTM B515	ASME SB-514, SB-515	—
Bar/Rod	ASTM B408	ASME SB-408	AMS 5766
Plate/Sheet/Strip	ASTM B409	ASME SB-409	AMS 5871
Forgings	ASTM B564	ASME SB-564	AMS 5766
UNS Designation	N08810
Werkstoff Number	1.4958
DIN Designation	NiCrFe
Chinese Equivalent	NS112

Frequently Asked Questions

Q: What is the difference between Incoloy 800 and Incoloy 800H?

A: Incoloy 800H has controlled carbon content (0.05-0.10%) and guaranteed grain size (ASTM 5 or coarser), providing significantly improved creep-rupture strength at temperatures above 815°C. Standard Incoloy 800 has ≤0.10% carbon with no grain size requirement, making it suitable for general high-temperature service but not optimized for creep resistance.

Q: What is the maximum service temperature for Incoloy 800H?

A: For oxidation resistance, Incoloy 800H can be used up to 1093°C (2000°F). For structural strength and creep resistance, continuous service up to 870-927°C is recommended depending on stress levels. At 1000°C, the alloy provides useful creep resistance for many applications.

Q: Is Incoloy 800H readily weldable?

A: Yes. Incoloy 800H can be welded using TIG, MIG, resistance welding, and other standard processes. Matching filler metal ERNiFeCr-1 (AWS A5.14) is recommended. Preheating is not required for thicknesses under 15mm. For thick sections, post-weld heat treatment may be considered to restore creep resistance.

Q: What is the Chinese equivalent of Incoloy 800H?

A: The Chinese equivalent is NS112. This grade conforms to GB/T 15007 standards for nickel-based alloys.

Q: What product forms are available for Incoloy 800H?

A: Womic Steel supplies Incoloy 800H in seamless pipe, welded pipe, steel bar, steel plate, steel coil, strip, flanges, pipe fittings, forgings, and valves. Complete product specifications and size ranges are listed in the product availability section.

Contact Womic Steel

Website: www.womicsteel.com

E-mail: sales@womicsteel.com

Tel / WhatsApp / WeChat:

Victor: +86 15575100681

Jack: +86 18390957568

Womic Steel – Your reliable partner for Incoloy 800H (UNS N08810) seamless pipe, welded pipe, steel bar, steel plate, steel coil, flanges, fittings, forgings, and valves for petrochemical reforming, ethylene cracking, furnace manufacturing, and high-temperature creep-resistant applications worldwide. Full traceability, classification society certification, and EN 10204 Type 3.1/3.2 documentation available.