Project Description
Hastelloy G-3 / UNS N06985 is a nickel-chromium-iron-molybdenum-copper superalloy engineered specifically for highly sour well environments — where concentrated H₂S, high chlorides, dissolved CO₂, and elevated temperatures combine to defeat standard austenitic stainless steels and lower-grade nickel alloys. Standardized under ASTM B581 for bar and B582 for plate, G-3 is classified as a Type 4d alloy under NACE MR-0175 / ISO 15156, carrying no H₂S partial-pressure restriction below 300°F (149°C).
Hastelloy G-3 — Overview
Hastelloy G-3 (UNS N06985, W.Nr. 2.4619, trade names INCONEL® Alloy G-3 / Nicrofer 4023 hMo) is a second-generation Ni-Cr-Fe-Mo-Cu alloy that extended the sour-service performance ceiling of nickel-based tubulars and bar components into HPHT well conditions. The deliberate inclusion of copper (1.5–2.5%) greatly enhances resistance to reducing acids — notably sulfuric and phosphoric acid — while the moderate molybdenum level (6–8%) and controlled iron content (18–21%) deliver cost-effective corrosion protection against H₂S-chloride brines.
Unlike pure Ni-Mo-Cr grades such as C-276, G-3’s iron-rich matrix reduces raw-material cost without sacrificing SCC resistance in sour service. The ultra-low carbon ceiling of ≤0.015% suppresses sensitization and carbide precipitation in the weld HAZ, allowing G-3 fabrications to be used in the as-welded condition in most oilfield environments.
Under NACE MR-0175 / ISO 15156, G-3 cold-worked bar achieves cold-hardened yield strengths of 110–140 ksi (758–965 MPa) with a maximum hardness of 35 HRC — fully qualifying it for the most demanding OCTG and downhole bar applications in acid-gas injection and saltwater injection wells.
N06985 Equivalent Grades & Standards
Hastelloy G-3 is covered by a broad set of material standards. The table below maps all common designations used globally by engineers and procurement teams.
| Standard Body | Designation / Grade | Applicable Form |
|---|---|---|
| UNS (USA) | N06985 | All wrought forms |
| ASTM / ASME | B581 / SB581 (Rod & Bar) B582 / SB582 (Plate / Sheet / Strip) B619 / SB619 (Welded Pipe) B622 / SB622 (Seamless Pipe & Tube) B564 / SB564 (Forgings) | Bar, Plate, Pipe, Tube, Forging |
| API | API 5CRA / ISO 13680 Group 4 Category 22-50-7 | OCTG tubulars & couplings |
| EN / DIN (Europe) | W.Nr. 2.4619 / NiCr22Mo7Cu DIN 17744 / DIN 17750–17754 | All wrought forms |
| ISO | NW 2.4619 | Wrought alloy identification |
| GB / YB (China) | NS3403 / YB/T 4323 | Bar, Plate, Pipe |
| Trade Names | INCONEL® Alloy G-3 (Special Metals) Nicrofer 4023 hMo (VDM Metals) | All forms |
| NACE | MR-0175 / ISO 15156 — Type 4d (sour service) | Downhole & wellhead components |
| AWS (Welding) | ERNiCrMo-2 (Wire) / ENiCrMo-2 (Electrode) | Weld consumables |
Oil & Gas Applications of Hastelloy G-3
G-3’s NACE Type 4d qualification and cold-hardening capability make it the alloy of choice for the following specific components in sour, high-chloride, and acid-gas well environments:
- Production tubing strings
- Casing & liner strings
- Base pipe for sand screens
- Expandable tubulars
- VIT (vacuum-insulated tubing) pipe
- Packer mandrels & slips
- Swell packer elements
- Perforating gun bodies
- Landing joints
- Extension subs & marker joints
- AGI wellhead valve bodies
- Injection tubing strings
- Wellhead connector spools
- Downhole check valve housings
- AGI packer assemblies
- Injection pump shafts & impellers
- Shroud assemblies
- Coiled tubing guide bends
- Wellhead adapters
- Subsurface safety valve stems
- Gate valve stems & seats
- Tubing hanger lock screws
- Casing head spool necks
- Choke valve trim sets
- High-pressure flange studs
- H₂S scrubber spray headers
- Amine unit heat exchanger tubes
- CO₂ capture vessel internals
- Geothermal wellhead components
- CCS injection well completions
Supply Forms & Size Range — Hastelloy G-3 Bar
SHUNFU METAL stocks Hastelloy G-3 in solution-annealed and cold-worked bar forms for direct machining of downhole components. Non-standard dimensions and rough-machined blanks are available on request.
| Form | Size Range | Condition | Standard |
|---|---|---|---|
| Hot-Rolled Round Bar | Ø 6 – 300 mm | Annealed & Pickled | ASTM B581 |
| Cold-Drawn Round Bar | Ø 4 – 100 mm | Cold-Worked (CW) / Bright Annealed | ASTM B581 / API 5CRA |
| Forged Round Bar | Ø 100 – 650 mm | Forged + Solution Annealed | ASTM B564 |
| Hot-Rolled Flat Bar | T 6–150 mm × W 15–500 mm | Annealed & Pickled | ASTM B582 |
| Forged Flat Bar / Block | T 20–350 mm × W 60–900 mm | Forged + Annealed | ASTM B564 |
| Hex Bar | AF 8 – 110 mm | Bright / Pickled | ASTM B581 |
Standard lengths: 1,000–6,000 mm. Cut-to-length and rough-machined blanks available. MTC 3.1 per EN 10204 issued with every delivery.
Chemical Composition — ASTM B581 / UNS N06985
Composition per ASTM B581 / UNS N06985 and EN W.Nr. 2.4619. SHUNFU METAL performs in-house OES verification on every incoming heat, with full ICP cross-check available on critical sour-service orders.
| Element | Ni | Cr | Fe | Mo | Cu | Co | W | Nb+Ta | Mn | Si | C | P | S |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min % | Bal. | 21.0 | 18.0 | 6.0 | 1.5 | — | — | — | 1.0 | — | — | — | — |
| Max % | Bal. | 23.5 | 21.0 | 8.0 | 2.5 | 5.0 | 1.5 | 0.5 | 1.0 | 1.0 | 0.015 | 0.040 | 0.030 |
Key differentiator: Cu (1.5–2.5%) enhances resistance to reducing acids (H₂SO₄, H₃PO₄) — absent in C-276 and C-22. High Fe (18–21%) provides cost advantages vs. low-iron Ni-Mo-Cr grades. Carbon cap of 0.015% ensures as-welded intergranular corrosion resistance without post-weld heat treatment.
Mechanical Properties — Hastelloy G-3 Bar
G-3 is available in both solution-annealed (1,150°C / 2,100°F, water quench) and cold-worked (CW) conditions. SHUNFU METAL tests tensile, yield, elongation, and hardness on every production lot; NACE-sour-service grades include hardness certification to ≤35 HRC.
| Condition | YS min (MPa / ksi) | UTS min (MPa / ksi) | Elongation (%) | Hardness max |
|---|---|---|---|---|
| Annealed Plate (t ≤ 19 mm) | 241 / 35 | 621 / 90 | ≥ 45 | 100 HRB |
| Annealed Plate (t > 19 mm) | 207 / 30 | 586 / 85 | ≥ 35 | 100 HRB |
| CW Grade 110 (NACE) | 758 / 110 | 793 / 115 | ≥ 13 | 35 HRC |
| CW Grade 125 (NACE) | 862 / 125 | 897 / 130 | ≥ 10 | 37 HRC |
| CW Grade 140 (NACE) | 965 / 140 | 1,000 / 145 | ≥ 9 | 38 HRC |
Physical constants: Density 8.22–8.31 g/cm³ · Elastic Modulus 200 GPa (29 × 10⁶ psi) · Thermal Expansion 14.6 × 10⁻⁶/°C · Thermal Conductivity ~10 W/m·K · Melting Range ~1,340–1,370°C.
How SHUNFU METAL Ensures Quality
SHUNFU METAL sources G-3 bar in both annealed and cold-worked conditions from AOD/VOD-refined heats. Cold-worked grades are verified to ≤35 HRC per NACE MR-0175 requirements, with hardness traverse tests at the bar center and surface documented on the MTC.
Every heat of G-3 received is analyzed by our in-house optical emission spectrometer before cutting. Key elements — Cr, Mo, Fe, Cu, Ni, C — are verified against ASTM B581 limits. Material mix-up with lower-grade alloys is eliminated.
Forged bars ≥ Ø100 mm are 100% UT-tested to ASTM A388 / EN 10228-3. Machined blanks for downhole tooling undergo surface inspection per ASTM E165 (PT) or ASTM E709 (MT) as specified.
All orders ship with EN 10204 Type 3.1 Mill Test Certificates covering chemical analysis, mechanical test results, heat treatment records, and dimensional inspection. API 5CRA traceability documentation available on OCTG orders upon request.
