Inconel G-3 is a nickel-chromium-iron corrosion-resistant alloy with additions of molybdenum and copper. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
A nickel-chromium-iron alloy with molybdenum and copper additions, Inconel G-3 has several minor elements controlled to give increased resistance to heat-affected-zone (HAZ) corrosion and improved weldability. It offers excellent corrosion resistance to oxidizing chemicals and atmospheres, while its nickel and copper contents provide resistance to reducing chemicals; the nickel gives exceptional stress-corrosion-cracking resistance in chloride environments, the high molybdenum gives very good pitting and crevice resistance, and the low carbon prevents sensitisation and intergranular corrosion. It is particularly suited to reducing acids such as phosphoric and sulfuric, and to flue-gas desulfurisation. Its relatively high iron content makes it a cost-effective choice among nickel corrosion-resistant alloys. It is supplied in the solution-annealed condition, and in the cold-worked-and-aged condition for high-strength oilfield use.
Typical applications include flue-gas desulfurisation scrubbers (quenchers, dampers, ducting), phosphoric and sulfuric acid handling, and oil-and-gas country tubular goods (OCTG), packers and downhole equipment in sour, high-chloride wells.
| Property | Value | Unit |
|---|---|---|
| Density | 8.31 | g/cm³ |
| Melting range | 1330–1370 | °C |
| Elastic modulus | 199 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 13.5 | µm/m·°C |
| Thermal conductivity (20 °C) | 9.8 | W/m·K |
| Specific heat (20 °C) | 460 | J/kg·K |
| Structure | Austenitic (FCC), single phase | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | Balance | — | Base element; SCC / reducing-media resistance |
| Chromium | Cr | 21.0 | 23.5 | Oxidizing-media / pitting resistance |
| Iron | Fe | 18.0 | 21.0 | Base alloying; cost-effectiveness |
| Molybdenum | Mo | 6.0 | 8.0 | Pitting / crevice resistance |
| Copper | Cu | 1.50 | 2.50 | Reducing-acid resistance |
| Cobalt | Co | — | 5.0 | Residual |
| Tungsten | W | — | 1.50 | Minor; localized-corrosion resistance |
| Niobium | Nb | — | 0.50 | Stabiliser |
| Carbon | C | — | 0.015 | Low; prevents sensitisation |
Solution-annealed condition, typical values for UNS N06985.
| Condition | Property | Value |
|---|---|---|
| Solution annealed | Tensile strength (UTS) | ≥620 MPa (90 ksi) |
| Solution annealed | 0.2% yield strength | ≥240 MPa (35 ksi) |
| Solution annealed | Elongation at break | ≥45 % |
| Cold-worked (OCTG) | Yield strength | higher; to ~110 ksi grades |
| — | Elastic modulus | 199 GPa |
Confirm against the mill test report. High-strength oilfield product is supplied cold-worked; the low carbon content preserves corrosion resistance in the weld heat-affected zone.
| Environment | Performance | Notes |
|---|---|---|
| Oxidizing chemicals / atmospheres | Excellent | High chromium content |
| Reducing acids (phosphoric, sulfuric) | Excellent | Nickel + copper + molybdenum |
| Pitting / crevice corrosion | Very Good | High molybdenum |
| Chloride stress-corrosion cracking | Excellent | High nickel content |
| Intergranular / HAZ corrosion | Excellent | Low carbon; controlled minor elements |
The balance of chromium, molybdenum, copper and nickel gives broad resistance to both oxidizing and reducing media — notably phosphoric and sulfuric acids and flue-gas environments — with excellent resistance to chloride stress-corrosion cracking and to intergranular attack in the as-welded condition.
A single-phase solid-solution alloy; not hardenable by precipitation. Properties are set by solution annealing; high strength is obtained by cold work.
Solution Anneal Solution anneal at approximately 1120 °C (2050 °F) and rapidly quench (water or rapid air cool) to dissolve secondary phases and restore corrosion resistance. The alloy is not strengthened by heat treatment; cold work raises strength for oilfield products.
Good weldability; readily welded by the gas-tungsten-arc and gas-metal-arc processes with matching filler, and resistant to intergranular corrosion in the as-welded condition owing to its low carbon content. No post-weld heat treatment is normally required.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching G-3 filler (ERNiCrMo-9) |
| GMAW / MIG | Good | Matching filler |
| SMAW / stick | Good | Matching electrode (ENiCrMo-9) |
Weld with matching filler and clean surfaces; the alloy may be used as-welded without post-weld heat treatment.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Difficult; work-hardens, rigid setups, sharp tooling |
| Speeds | Slow speeds, positive feeds, no dwelling |
| Coolant | Ample coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Good; work-hardens; cold work also used to raise strength |
| Hot forming | 1010–1175 °C; solution anneal afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Pollution control | FGD scrubbers, quenchers, dampers, ducting | Acid + flue-gas resistance |
| Acid production | Phosphoric / sulfuric acid equipment | Reducing-acid resistance |
| Oil & gas | OCTG tubulars, packers, downhole equipment | Sour-service + chloride resistance |
| Chemical process | Reactors, heat exchangers | General + localized corrosion resistance |
| Product Form | ASTM Standard | ASME |
|---|---|---|
| Plate, sheet and strip | ASTM B582 | ASME SB-582 |
| Bar, rod and forgings | ASTM B581 | ASME SB-581 |
| Seamless pipe and tube | ASTM B622 | ASME SB-622 |
| Welded pipe and tube | ASTM B619 / B626 | ASME SB-619 |
Nickel-chromium-iron corrosion-resistant alloy with molybdenum and copper. UNS N06985.
| Alloy | Cr % | Mo % | Fe % | Best Used For |
|---|---|---|---|---|
| Inconel G-3 | 21–23.5 | 6–8 | 18–21 | Ni-Cr-Fe-Mo-Cu; reducing acids, FGD, sour OCTG |
| Hastelloy G-30 | 28–31.5 | 4–6 | 13–17 | Higher-chromium G-family; phosphoric acid |
| Incoloy 825 | 19.5–23.5 | 2.5–3.5 | balance | Ni-Fe-Cr-Mo-Cu; sulfuric / phosphoric acid |
| Inconel 625 | 20–23 | 8–10 | ≤5 | General Ni-Cr-Mo-Nb corrosion / strength |
| Hastelloy C-276 | 14.5–16.5 | 15–17 | 4–7 | Reducing media, wet chlorine |




