UNS N08120 Nickel Alloy
UNS N08120 (Alloy HR-120, 1.4898) is a nickel‑iron‑chromium alloy with tungsten and niobium. Its ~33% iron content lowers cost compared to full‑nickel alloys, while still providing strong performance in oxidising and carburising environments up to 1100°C. Engineers choose it for continuous high‑temperature service in furnaces, thermal cracking tubes, and incinerators when austenitic stainless steels are inadequate, and Inconel 617/601 is too expensive. It is supplied as ASTM B622 seamless pipe worldwide.
1. Chemical Composition
N08120 chemical composition per ASTM B622. All values shown as weight percentage (wt%).
| Grade | Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulphur (S) | Silicon (Si) | Chromium (Cr) | Nickel (Ni) | Iron (Fe) | Molybdenum (Mo) | Tungsten (W) | Niobium (Nb) | Aluminium (Al) | Cobalt (Co) | Boron (B) | Nitrogen (N) |
| N08120 | 0.05 max | 1.00 max | 0.030 max | 0.010 max | 1.00 max | 23.0 -- 27.0 | 35.0 -- 39.0 | Balance (~33%) | 2.50 max | 2.50 max | 0.10 -- 0.60 | 0.10 -- 0.50 | 3.00 max | 0.003 max | 0.10 -- 0.20 |
The defining feature of this alloy is the combination of high chromium (25% nominal), iron balance in place of expensive nickel, and W + Nb additions that stabilise the matrix at elevated temperatures and resist creep.
2. Mechanical Properties
Minimum mechanical properties for N08120 seamless pipe in the annealed condition per ASTM B622.
| Property | Condition | Tensile Strength (Min) | Yield Strength 0.2% Offset (Min) | Elongation in 50 mm (Min) | Hardness (Max) | PREN (calculated) | Service Temperature Range |
| Value | Solution Annealed + Quenched | 650 MPa / 94 ksi | 295 MPa / 43 ksi | 35% | 223 HBW | ~46 | -196 °C to +300 °C (cryogenic to moderate high-temp) |
3. Equivalent Grade
Cross-reference for UNS N08120 across major international standards and trade names.
| Grade / Trade Name | UNS | GB/T | JIS | DIN / EN (W.Nr.) | GOST |
| Alloy HR-120 | N08120 | -- | -- | 1.4898 | -- |
| Nicrofer 3520 Co | -- | -- | -- | 1.4898 | -- |
| Haynes HR-120 | N08120 | -- | -- | -- | -- |
3. Key Technical Advantages
N08120 has several technical properties that set it apart from lower-cost heat-resistant grades and justify its use in demanding thermal applications.
- High-Temperature Oxidation Resistance up to 1100°C: With 25% chromium, N08120 forms a strong Cr2O3 film that slows oxidation, outperforming 310S stainless steel and showing about 40–50% less metal loss at 1093°C in cyclic tests.
- Creep Resistance via W and Nb Additions: Tungsten and niobium strengthen the alloy at high temperatures by stabilising grain boundaries and dislocations, giving creep resistance similar to Incoloy 800HT at the same stress but with lower nickel cost.
- Resistance to Carburisation and Sulphidation: In high-carbon pyrolysis and cracking conditions, aluminium and chromium in N08120 create a protective oxide layer, limiting carbon penetration and reducing sulphur gas attack versus lower-chromium alloys without aluminium.
- Lower Cost than Inconel 601 and 617: With about 33% iron, N08120 costs much less than Inconel 601 and 617, giving major savings on large high‑temperature tube projects without noticeably reducing performance below 1100°C.
- Good Weldability and Fabricability: N08120 welds easily with matching filler and no preheat. Post‑weld solution annealing restores full strength. It can be hot or cold formed in standard tube mills, giving predictable delivery times.
4. Common Manufacturing Standards
N08120 seamless pipe is manufactured and tested to the following standards.
- ASTM B622: Seamless nickel and nickel-cobalt alloy pipe and tube -- primary product standard
- ASME SB-622: ASME equivalent of ASTM B622 for pressure vessel and piping code compliance
- ASTM B829: General requirements for nickel and nickel alloy seamless pipe and tube
- ASTM E8/E8M: Tensile testing of metallic materials
- ASTM E112: Grain size determination for wrought nickel alloys
- EN 10216-5: Seamless steel tubes for pressure purposes -- stainless and nickel alloy (European)
- NACE MR0175 / ISO 15156: Sulphide stress cracking resistance requirements for sour service environments
5. Primary Applications
N08120 seamless pipe is used in the following services.
- Petrochemical Ethylene Cracker Radiant Coil Tubes: Furnace tubes in steam cracking units that operate continuously above 900°C and require resistance to both oxidation and carburisation from hydrocarbon feed gases.
- Direct-Fired Industrial Furnace Radiant Tubes and Retorts: Heat treatment and annealing furnaces in steel and non-ferrous metalworking plants where tube metal temperatures exceed 1000°C under oxidising atmospheres.
- Municipal and Hazardous Waste Incineration Superheater Tubes: High-temperature sections of waste-to-energy boilers where flue gases contain sulphur, chlorides, and heavy metal compounds that attack conventional stainless grades.
- Reformer and Syngas Furnace Transfer Line Components: Primary and secondary reformer outlet manifolds and crossover piping in ammonia and methanol plants, where process temperatures run between 850°C and 1050°C under reducing conditions.
- Power Generation High-Temperature Combustion Air Preheater Tubes: Heat recovery systems in gas turbine combined cycle plants where preheater outlet temperatures push the limits of standard austenitic stainless pipe materials.