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 800H vs Inconel 625, UNS N08810 vs UNS N06625
Verdict in one sentence: Inconel 625 wins on dual corrosion-plus-temperature service (FGD scrubbers, flare tips, halogenated chemical process exchangers); Incoloy 800H wins on cost-per-creep-life in plain high-temperature oxidation service to 815 deg C with no aggressive corrosion. Inconel 625 (UNS N06625) is a Ni-Cr-Mo-Nb solid-solution-strengthened alloy with 58 percent Ni minimum, 20 to 23 percent Cr, 8 to 10 percent Mo and 3.15 to 4.15 percent Nb+Ta. The molybdenum and niobium strengthen the matrix via solid-solution and gamma-double-prime (gamma'') precipitation, giving higher tensile and yield strength than Incoloy 800H at every test temperature. Incoloy 800H (UNS N08810) is a Ni-Fe-Cr alloy with 30 to 35 percent Ni, balance Fe and no Mo or Nb, qualified to ASME Section VIII allowable-stress envelope at lower mill price. This page lays out the chemistry side-by-side, mechanical floors, decision rules and welding-filler differences.
At a Glance Comparison
| Property | Incoloy 800H (N08810) | Inconel 625 (N06625) |
|---|---|---|
| Matrix base | Ni-Fe-Cr (iron-base) | Ni-Cr-Mo-Nb (nickel-base) |
| Nickel (Ni) | 30.0 to 35.0 percent | 58.0 percent min |
| Chromium (Cr) | 19.0 to 23.0 percent | 20.0 to 23.0 percent |
| Molybdenum (Mo) | n/a | 8.0 to 10.0 percent |
| Niobium (Nb+Ta) | n/a | 3.15 to 4.15 percent |
| Iron (Fe) | balance, ~39.5 percent | 5 percent max |
| Max ASME design temp | 815 deg C (1500 deg F) | 815 deg C (Section VIII Div 1) |
| Indicative mill price | baseline | ~ 60 to 100 percent higher per kg |
Chemistry Side-by-Side
| Element | Incoloy 800H | Inconel 625 | Functional role |
|---|---|---|---|
| Nickel (Ni) | 30.0 to 35.0 | 58.0 min | Matrix base + chloride SCC resistance |
| Chromium (Cr) | 19.0 to 23.0 | 20.0 to 23.0 | Cr2O3 passive film; oxidation + acid |
| Molybdenum (Mo) | n/a | 8.0 to 10.0 | Solid-solution strength + pitting + crevice |
| Niobium (Nb+Ta) | n/a | 3.15 to 4.15 | Gamma'' (Ni3Nb) precipitation hardening |
| Iron (Fe) | balance | 5 max | Solution strength on 800H |
| Carbon (C) | 0.05 to 0.10 | 0.10 max | Creep carbide control |
| Al + Ti combined | 0.30 to 1.20 | 0.40 + 0.40 max | Carburization defence on 800H |
Mechanical Properties Side-by-Side
| Property at RT | Incoloy 800H | Inconel 625 (annealed) |
|---|---|---|
| Tensile strength (Rm) | >= 450 MPa (65 ksi) | >= 760 MPa (110 ksi) |
| 0.2 percent proof stress | >= 170 MPa (25 ksi) | >= 345 MPa (50 ksi) |
| Elongation A5 | >= 30 percent | >= 30 percent |
| Tensile at 540 deg C | ~ 415 MPa | ~ 690 MPa |
| Tensile at 815 deg C | ~ 200 MPa | ~ 415 MPa |
[All values are indicative; verify against ASME Section II Part D Table 1A and Special Metals high-temperature datasheets.]
When to Specify Incoloy 800H Over Inconel 625
- Plain high-temperature oxidation service to 815 deg C with no aggressive corrosion (no halogenated streams, no chloride above ppm, no sulfide above NACE limit)
- ASME Section VIII Division 1 pressure vessels for hydrogen plant, methanator, hydrocracker and hydrotreater service where mill-price saving over Inconel 625 is material
- Fired-heater radiant tubes and reformer pigtails where the operating envelope sits within the Incoloy 800H creep floor
- Petrochemical convection bundles to API 660 in non-corrosive service
- ASME Section VIII vessels above 540 deg C with thermal cycling that fatigues 321 / 347 stainless
When Inconel 625 Wins
- FGD (flue-gas desulfurization) scrubbers: hot acid + chloride combination defeats Incoloy 800H
- Flare tips and burner sleeves: cyclic high temperature + combustion products
- Halogenated chemical process exchangers: chlorinated and fluorinated streams above 200 deg C
- Subsea production hardware: chloride seawater + high-pressure + cyclic stress
- NACE MR0175 sour service above 5 ppm H2S at elevated temperature where Incoloy 800H is out of envelope
- Bellows and expansion joints: gamma'' precipitation gives the fatigue floor required for cyclic flex
Migration Notes
The two grades are NOT direct substitutes. Inconel 625 has 60 to 100 percent higher mill price; using it where Incoloy 800H would suffice doubles material cost. Conversely, substituting 800H where 625 is specified can lead to corrosion failure in the first months of service. Engineering review of the corrosion + temperature envelope is mandatory before substitution. The qualified ASME specifications differ (Incoloy 800H is P-No. 45; Inconel 625 is P-No. 43) and the welding-procedure qualification under Section IX must be redone for each base metal. Dual certification is impossible because the chemistry windows do not overlap (Inconel 625 requires Mo above 8 percent which is outside any Incoloy 800H heat).
Welding Filler Differences
| Process | Incoloy 800H filler | Inconel 625 filler |
|---|---|---|
| GTAW | ERNiCr-3 (Inconel 82) | ERNiCrMo-3 (Inconel 625 filler) |
| GMAW | ERNiCr-3 spool | ERNiCrMo-3 spool |
| SMAW | ENiCrFe-2 (Inconel 182) | ENiCrMo-3 |
| SAW | ER NiCr-3 wire + flux | ER NiCrMo-3 wire + flux |
Price and Availability Differential
Inconel 625 mill price tracks roughly 60 to 100 percent above Incoloy 800H per kilogram, driven by the 58 percent minimum nickel plus 8 to 10 percent molybdenum plus 3 to 4 percent niobium chemistry. Niobium is itself a strategic-metal commodity with volatile pricing. Where the service envelope permits Incoloy 800H, the cost saving over Inconel 625 is material to project economics and is the primary driver for specifying 800H on hydrocarbon-service exchangers. TorqBolt stocks both grades across the form-factor range; for project pricing across pipe, tube, bar, plate, forgings, flanges, fittings and fasteners, contact TorqBolt sales.
TorqBolt Incoloy 800H Forms
- Seamless pipe + seamless tube to ASTM B407
- Round bar to ASTM B408
- Plate + sheet to ASTM B409
- Forgings + flanges + fittings to ASTM B564
- ASME Section VIII pressure vessels + API 660 heat exchangers
Related Comparison Pages
- Incoloy vs Inconel: family disambiguation
- Incoloy 800H vs Inconel 600: carburization service diff
- Incoloy 800H vs Incoloy 825: creep vs corrosion variant
- Incoloy 800 vs 800H vs 800HT: internal grade family
Frequently Asked Questions
Q. What is the headline difference between Incoloy 800H and Inconel 625?
Inconel 625 is a Ni-Cr-Mo-Nb solid-solution-strengthened alloy with 58 percent Ni minimum, 20 to 23 percent Cr, 8 to 10 percent Mo and 3.15 to 4.15 percent Nb+Ta. It wins in dual corrosion-plus-temperature service such as flare tips, FGD scrubbers and chemical-process exchangers handling halogenated streams. Incoloy 800H wins on cost-per-creep-life in plain high-temperature oxidation service up to 815 deg C with no corrosive atmosphere.
Q. Which is stronger at temperature?
Inconel 625 is stronger at temperature. The molybdenum and niobium strengthen the matrix via solid-solution and gamma-double-prime (gamma'') precipitation, giving higher 0.2 percent yield and tensile strength than Incoloy 800H at every test temperature from room temperature to 815 deg C. The trade-off is significantly higher mill price.
Q. Which is the cheaper grade?
Incoloy 800H by a wide margin. Inconel 625 carries 8 to 10 percent molybdenum and 3.15 to 4.15 percent niobium plus 58 percent minimum nickel; on London Metal Exchange spot prices, the mill price differential is typically 60 to 100 percent over Incoloy 800H per kilogram.
Q. When is Incoloy 800H NOT enough and Inconel 625 the answer?
When the service envelope combines high temperature (above 540 deg C) with aggressive corrosion (chloride, sulfide, halogenated process streams, sour gas above NACE limits). Incoloy 800H is qualified for plain oxidation; it is not qualified for corrosive process streams above NACE MR0175 sour-service limits without engineering review.
Q. Are 800H and 625 dual-certified?
No. They are different alloy classes with non-overlapping chemistry windows. A single heat can never satisfy both UNS N08810 (Incoloy 800H) and UNS N06625 (Inconel 625) chemistry limits simultaneously.
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