Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Incoloy 800 vs 800H vs 800HT
Verdict in one sentence: Incoloy 800 (UNS N08800) is the baseline 650 deg C grade, Incoloy 800H (UNS N08810) is the controlled-carbon plus grain-size variant qualified to 815 deg C under ASME Section VIII Division 1, and Incoloy 800HT (UNS N08811) is the wider Al + Ti window variant qualified to 982 deg C. The three share the same Ni-Fe-Cr chemistry base (30 to 35 percent Ni, 19 to 23 percent Cr, balance Fe) but differ in carbon content and Al + Ti window in ways that control creep-rupture strength and ASME service-temperature qualification on the heat. Dual-certified 800H / 800HT material is now the most common procurement form in petrochemical and refinery service. This page lays out the chemistry diffs, mechanical diffs, decision tree for which grade to specify, and migration notes when a project drawing calls for one and the mill can supply the other.
At a Glance Comparison
| Property | Incoloy 800 | Incoloy 800H | Incoloy 800HT |
|---|---|---|---|
| UNS designation | N08800 | N08810 | N08811 |
| Werkstoff | 1.4876 | 1.4876 | 1.4959 |
| Carbon (C), percent | 0.10 max | 0.05 to 0.10 | 0.06 to 0.10 |
| Al + Ti combined, percent | 0.30 to 1.20 | 0.30 to 1.20 | 0.85 to 1.20 |
| ASTM grain size requirement | none | 5 or coarser | 5 or coarser |
| Max ASME design temperature | 650 deg C (1200 deg F) | 815 deg C (1500 deg F) | 982 deg C (1800 deg F) |
Chemistry Side-by-Side
| Element | N08800 | N08810 (800H) | N08811 (800HT) |
|---|---|---|---|
| Carbon (C) | 0.10 max | 0.05 to 0.10 | 0.06 to 0.10 |
| Manganese (Mn) | 1.50 max | 1.50 max | 1.50 max |
| Sulfur (S) | 0.015 max | 0.015 max | 0.015 max |
| Silicon (Si) | 1.00 max | 1.00 max | 1.00 max |
| Copper (Cu) | 0.75 max | 0.75 max | 0.75 max |
| Nickel (Ni) | 30.0 to 35.0 | 30.0 to 35.0 | 30.0 to 35.0 |
| Chromium (Cr) | 19.0 to 23.0 | 19.0 to 23.0 | 19.0 to 23.0 |
| Aluminium (Al) | 0.15 to 0.60 | 0.15 to 0.60 | 0.25 to 0.60 |
| Titanium (Ti) | 0.15 to 0.60 | 0.15 to 0.60 | 0.25 to 0.60 |
| Al + Ti combined | 0.30 to 1.20 | 0.30 to 1.20 | 0.85 to 1.20 |
| Iron (Fe) | balance | balance | balance |
Mechanical Properties Side-by-Side
| Property at RT | Incoloy 800 | Incoloy 800H | Incoloy 800HT |
|---|---|---|---|
| Tensile strength (Rm) | >= 520 MPa (75 ksi) | >= 450 MPa (65 ksi) | >= 450 MPa (65 ksi) |
| 0.2 percent proof stress | >= 205 MPa (30 ksi) | >= 170 MPa (25 ksi) | >= 170 MPa (25 ksi) |
| Elongation A5 | >= 30 percent | >= 30 percent | >= 30 percent |
| Creep rupture stress 10,000 hr at 815 deg C | n/a (out of envelope) | ~ 35 MPa (5 ksi) | ~ 45 MPa (6.5 ksi) |
| Max sustained oxidation temp | 815 deg C (envelope) | 982 deg C | 1093 deg C |
[Cross-verify creep-rupture floors against ASME Section II Part D Table 1A and Special Metals high-temperature datasheet.]
When to Specify Each Grade, Decision Tree
- Specify Incoloy 800 (N08800) when: sustained operating temperature is below 650 deg C (1200 deg F), creep is not the controlling failure mode, and the cost saving over 800H is material to the project economics. Typical use: low-temperature heat exchangers, marine evaporator tubes, paper-mill digester components.
- Specify Incoloy 800H (N08810) when: sustained operating temperature is 650 to 815 deg C (1200 to 1500 deg F), ASME Section VIII Division 1 qualification is required, and creep-rupture strength controls the wall-thickness selection. Typical use: reformer pigtails, hydrocracker feed-effluent exchangers, pressure vessels above 540 deg C.
- Specify Incoloy 800HT (N08811) when: sustained operating temperature exceeds 815 deg C (1500 deg F), highest creep-rupture floor is required, and the project specification permits the wider Al+Ti window. Typical use: final-stage steam superheaters, ethylene cracker convection bundles, furnace hearth plates at 900 deg C.
Migration Notes Between Grades
Substituting Incoloy 800 with Incoloy 800H is always permissible because 800H meets all chemistry and mechanical floors of 800 plus the additional carbon and grain-size envelope. The reverse (using 800 where 800H is specified) is NOT permissible above 650 deg C because 800 does not carry the ASME Section VIII allowable-stress qualification for the higher service temperature. Substituting 800H with 800HT is permissible above 815 deg C if the wider Al+Ti window is acceptable to the welding-procedure qualification; ASME Section IX permits the substitution under P-No. 45 to P-No. 45 procedures with re-qualification of the all-weld-metal chemistry. Dual-certified 800H / 800HT material is now the most common procurement form and avoids the substitution question entirely.
Welding Considerations Across the Three Grades
All three grades are P-No. 45 under ASME Section IX with the same qualified consumables: ERNiCr-3 (Inconel 82) for gas-tungsten and gas-metal arc, ENiCrFe-2 (Inconel 182) for shielded-metal arc and ER NiCr-3 wire plus matching flux for submerged arc. Welding-procedure qualification (PQR) tests tensile strength, side-bend ductility, all-weld-metal chemistry and Charpy impact at the agreed test temperature. The procedure qualified on Incoloy 800H is transferable to 800HT under P-No. 45 to P-No. 45 substitution rules with re-qualification of all-weld-metal chemistry on the agreed filler heat. Post-weld heat treatment is not mandatory for thickness below 38 mm under ASME Section VIII Division 1 paragraph UCS-56; solution-anneal at 1149 deg C minimum is the qualified PWHT for thicker sections.
Certification and Test Reporting
TorqBolt supplies all three grades with EN 10204 type 3.1 mill test certificate by default. The certificate carries heat number, ladle and check-analysis chemistry, solution-anneal cycle (time and temperature), room-temperature tensile and yield, elongation, hardness, ASTM grain size (for H and HT), hydrostatic or eddy-current test result, and dimensional report. EN 10204 type 3.2 with Lloyds Register, DNV, BV, SGS or TUV witness is supplied on call-out and is standard practice on refinery, petrochemical and pressure-vessel procurement. NACE MR0175 / ISO 15156 compliance for sour service is supplied where the operating envelope permits, with Rockwell B hardness verification on every heat.
Forms TorqBolt Supplies in All Three Grades
- Seamless pipe to ASTM B407
- Seamless tube to ASTM B407
- Welded pipe to ASTM B514 / B515
- Round bar to ASTM B408
- Plate + sheet to ASTM B409
- Forgings + flanges + fittings to ASTM B564
- Fasteners: stud bolts, hex bolts, heavy hex bolts, nuts, washers
- ASME Section VIII pressure-vessel material for hydrocarbon + chemical service
- API 660 heat-exchanger tube + tubesheet for refinery and petrochemical exchangers
Frequently Asked Questions
Q. What is the headline difference between Incoloy 800, 800H and 800HT?
Carbon range and Al+Ti window. Incoloy 800 (UNS N08800) is the baseline alloy with carbon 0.10 percent maximum, qualified to 650 deg C. Incoloy 800H (UNS N08810) carries controlled carbon 0.05 to 0.10 percent plus ASTM grain size 5 or coarser, qualified to 815 deg C under ASME Section VIII. Incoloy 800HT (UNS N08811) adds the combined Al + Ti window of 0.85 to 1.20 percent, qualified to 982 deg C.
Q. Can Incoloy 800 be substituted for 800H?
No. The two are NOT interchangeable. Incoloy 800 has no ASTM grain-size requirement and no controlled-carbon floor, so it does not meet the ASME Section VIII allowable-stress envelope for service above 650 deg C. Field-substituting 800 for 800H invalidates the code qualification.
Q. Is 800HT always better than 800H?
Not always. 800HT is preferred when sustained service exceeds 815 deg C; below that envelope, 800H delivers identical creep performance at lower mill price. The Al + Ti window of 800HT tightens forging-shop practice and slightly raises mill cost.
Q. Are 800H and 800HT dual-certified routinely?
Yes. Most mills now cast heats that meet both 800H and 800HT chemistry windows simultaneously, producing dual-certified material stamped 800H / 800HT. This is the common procurement form for refinery and petrochemical service.
Q. Which 800-series grade is specified for ethylene cracker tubes?
Centrifugally cast tubes for ethylene crackers above 1000 deg C use HP-Modified (35Cr-45Ni) or HK-Modified (25Cr-20Ni) cast alloys, not wrought Incoloy 800H. Incoloy 800H wrought tube is the qualified form for the convection-section bundles and outlet headers below 815 deg C, where the centrifugally cast tubes connect via pigtails.
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