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Material Specification

Alloy 800HT

Alloy 800HT Fasteners
Narrow Al+Ti Window Alloy 800 – Highest ASME Allowable Stresses of the 800 Family

Incoloy 800HT Fasteners

Buy Incoloy Alloy 800HT (UNS N08811 / Werkstoff 1.4959 / ASTM B408) bolts, stud bolts, heavy hex nuts, socket cap screws, and custom CNC fasteners from Exotic Alloy. Incoloy 800HT tightens the alloy 800H specification further — carbon 0.06–0.10%, aluminium plus titanium held between 0.85 and 1.20%, and ASTM grain size 5 or coarser — producing the most consistent and highest creep-rupture strength of the entire alloy 800 family.

Exotic Alloy manufactures Incoloy 800HT fasteners conforming to ASTM B408, ASME SB-408 and ASME Code Case 1987 in metric M6–M100 and imperial ¼"–4" sizes with full EN 10204 3.1 material test certificates for ethylene cracking furnaces, steam reformers and high-temperature petrochemical service.

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Product Range

Alloy 800HT Fasteners Available

Alloy 800HT Hex Bolts
Alloy 800HT
Hex Bolts
Alloy 800HT Heavy Hex Bolts
Alloy 800HT
Heavy Hex Bolts
Alloy 800HT Stud Bolts
Alloy 800HT
Stud Bolts
Alloy 800HT Threaded Rods
Alloy 800HT
Threaded Rods
Alloy 800HT Anchor Bolts
Alloy 800HT
Anchor Bolts
Alloy 800HT Hex Nuts
Alloy 800HT
Hex Nuts
Alloy 800HT Washers
Alloy 800HT
Washers
Alloy 800HT Cotter Pins
Alloy 800HT
Cotter Pins
Alloy 800HT Springs
Alloy 800HT
Springs
Alloy 800HT Circlips
Alloy 800HT
Circlips
Alloy 800HT Coated Fasteners
Alloy 800HT
Coated Fasteners
Alloy 800HT Custom Spacers
Alloy 800HT
Custom Spacers
Technical Data

Alloy 800HT Specifications

Chemical Composition — Incoloy 800HT (wt. %)
ElementNiCrFeCAlTiAl+TiMnSi
Min %30.0019.0039.500.060.250.250.85––
Max %35.0023.00Balance0.100.600.601.201.501.00
Mechanical Properties — Incoloy 800HT
ConditionUTS (MPa)YS 0.2% (MPa)Elongation (%)Hardness
Solution Annealed (ASTM B408 Minimum)≥ 450≥ 170≥ 30≤ 192 HB
Solution Annealed (Typical Bar)54023048130 HB
Hot Finished Forged Bar495–600205–27540–50≤ 175 HB
Cold Drawn / Stress Relieved620–790415–58515–25≤ 240 HB
Physical Properties
Density7.94 g/cm³
Melting Range1357–1385°C (2475–2525°F)
Specific Heat Capacity460 J/kg·K (0–100°C)
Thermal Conductivity11.5 W/m·K at 20°C
Thermal Expansion14.4 µm/m·°C (20–100°C)
Electrical Resistivity0.989 µΩ·m at 20°C
Equivalent Grades & Standards
UNSWerkstoff / DINEN DesignationCommon Name
N08811 1.4959 X8NiCrAlTi32-21 Incoloy 800HT

Key Specifications: ASTM B408 (Rod & Bar) / ASTM B409 (Plate & Sheet) / ASTM B407 (Tube) / ASTM B564 (Forgings) / ASTM B366 (Fittings) / ASME Code Case 1987

Machinability: Incoloy 800HT machines like alloy 800H — the coarse grain requires sharp tooling for a good finish. Use rigid setups, positive-rake carbide at 30–50 SFM, heavy positive feeds, generous depth of cut and continuous flood coolant. Thread rolling is preferred to cutting wherever section size allows.

Welding: Welded by GTAW, GMAW and SMAW using INCONEL Filler Metal 82 (ERNiCr-3) or INCO-WELD A electrodes. Where the joint must carry creep loads, filler metal is selected for matching rupture strength. Pre-heat is not required; keep interpass temperature moderate. Post-weld solution annealing may be specified for heavily restrained assemblies.

Forging: Hot forge between 1010–1205°C (1850–2200°F), finishing above 980°C (1800°F). As with 800H, finishing too cold refines the grain and forfeits the creep strength the grade is bought for.

Heat Treatment: Solution anneal at 1149°C (2100°F) minimum followed by air cool or water quench, to establish ASTM grain size 5 or coarser. Note that material certified to UNS N08810 cannot be re-certified as N08811 unless it also meets the narrower 0.85–1.20% aluminium-plus-titanium requirement; 800HT carries higher ASME maximum allowable design stresses than 800H for this reason.

Incoloy 800HT delivers the highest and most consistent creep-rupture strength of the alloy 800 family, which is why it carries higher ASME maximum allowable design stresses than alloy 800H under Code Case 1987. The narrow aluminium-plus-titanium window removes the heat-to-heat scatter that can occur within the wider 800H range. Oxidation, carburisation and nitriding resistance are equal to alloy 800, service is approved to 899°C (1650°F) under the ASME Code, and the high nickel content confers immunity to chloride-induced stress-corrosion cracking.

Key Characteristics

  • Aluminium plus titanium controlled to a narrow 0.85–1.20% window.
  • Highest ASME allowable design stresses in the alloy 800 family.
  • Most consistent heat-to-heat creep-rupture performance.
  • Approved for ASME Code service to 899°C (1650°F).
  • Excellent oxidation and carburisation resistance with stable structure.

Typical Applications

  • Ethylene cracking furnaces: tube support, hanger and header bolting.
  • Steam methane reformers: outlet manifold and pigtail fastener assemblies.
  • Petrochemical: high-temperature process heater structural fasteners.
  • Power generation: superheater and reheater support hardware.
  • Heat treatment: heavy-duty furnace retort and fixture bolting.