Overview & Designation
Alloy 2.4816 — designated NiCr15Fe or NiCr15Fe8 under European standards — is a solid-solution-strengthened nickel-chromium-iron alloy that has served as the baseline workhorse of high-temperature and corrosion-critical engineering since the 1930s. Its composition of high nickel (≥72 wt%), moderate chromium (14–17%), and controlled iron (6–10%) delivers three simultaneous performance advantages: oxidation resistance above 900°C, complete immunity to chloride-induced stress corrosion cracking (SCC), and excellent tensile strength retention up to 700°C under creep loading.
The designation 2.4816 is the Werkstoff-Nummer (W.Nr) defined in DIN 17742 and EN ISO 6208. The chemical symbol names NiCr15Fe and NiCr15Fe8 reflect its principal additions — approximately 15% chromium and 8% iron. In North American practice, this alloy is universally traded as Inconel 600, the registered trade name of Special Metals Corporation, classified under UNS N06600.
Minor compositional differences between producers exist within standard tolerances. Always compare the certified Mill Test Report (MTR) against the applicable procurement standard (ASTM B564, EN 10272, etc.) before final material acceptance. Citing multiple designations — e.g., "W.Nr 2.4816 / UNS N06600" — on purchase orders eliminates sourcing ambiguity globally.
Chemical Composition
The composition window for 2.4816 / NiCr15Fe is tightly defined across EN, ASTM, and ASME standards. The high nickel floor (≥72%) provides matrix stability underpinning corrosion immunity, while chromium forms a protective Cr₂O₃ oxide scale at elevated temperatures. Iron acts as a solid-solution strengthener and cost modifier without degrading corrosion performance.
| Element | Min % | Max % | Typical % | Primary Function |
|---|---|---|---|---|
| Nickel (Ni) | 72.0 | — | 74.0 | Matrix; immunity to SCC and pitting in alkaline media |
| Chromium (Cr) | 14.0 | 17.0 | 15.5 | Oxidation resistance; Cr₂O₃ scale formation above 900°C |
| Iron (Fe) | 6.0 | 10.0 | 8.0 | Solid-solution strengthener; cost modifier |
| Carbon (C) | — | 0.15 | 0.08 | Carbide formation; sensitisation risk if >0.08% |
| Manganese (Mn) | — | 1.0 | 0.5 | Deoxidiser during melting |
| Silicon (Si) | — | 0.5 | 0.2 | Deoxidiser; minor oxidation resistance benefit |
| Copper (Cu) | — | 0.5 | 0.1 | Residual element — controlled |
| Sulfur (S) | — | 0.015 | 0.003 | Tightly controlled; hot shortness risk above 0.015% |
For service environments where sensitisation is a concern — intergranular corrosion in caustic media, or stress corrosion in high-purity water — specify carbon ≤0.08% on the purchase order. This significantly reduces the risk of grain-boundary Cr₂₃C₆ precipitation during post-weld heat treatment or slow cooling through the 427–760°C sensitisation window.
Global Equivalents & Cross-References
The most common procurement error with 2.4816 is misidentification due to the variety of international designations. The table below is a verified twelve-system cross-reference. When issuing an international RFQ — particularly to suppliers in China, Europe, Japan, or North America — always cite at least two designations to eliminate sourcing ambiguity.
| Standard System | Designation | Standard Reference | Region |
|---|---|---|---|
| Werkstoff-Nummer (W.Nr) | 2.4816 | DIN 17742 / EN ISO 6208 | Europe / Global |
| DIN Chemical Symbol | NiCr15Fe | DIN 17742 | Germany / Europe |
| EN Chemical Symbol | NiCr15Fe8 | EN 10095 / EN 10272 | Europe |
| UNS Number | N06600 | ASTM / SAE UNS System | North America |
| Trade Name | Inconel 600 | Special Metals Corporation (SMC) | Global |
| ASTM (product forms) | — | B163 / B166 / B167 / B168 / B516 / B517 / B564 (forgings) | North America |
| ASME (boiler & pressure vessel) | — | SB-163 / SB-166 / SB-167 / SB-168 / SB-564 (forgings) | North America |
| British Standard (BS) | NA14 | BS 3072–3076 | United Kingdom |
| AFNOR (French) | NC15Fe | NF A05-051 | France |
| JIS (Japanese) | NCF 600 | JIS G4901 / G4902 | Japan |
| ISO | NW 6600 | ISO 6208 | International |
| Russian GOST (approx.) | ХН75МБТЮ | Verify by full composition comparison | Russia / CIS |
Recommended PO specification text: "Material shall conform to ASTM B564 / EN 10272, UNS N06600 / W.Nr 2.4816 (NiCr15Fe). Mill Test Reports to EN 10204 Type 3.1 minimum (3.2 via third-party inspection for nuclear / PED Category III applications, to be agreed at enquiry). Chemical analysis to include all elements per the applicable standard. Delivery condition: solution-annealed."
Mechanical Properties
Mechanical properties of 2.4816 forgings depend on the delivery condition (solution-annealed, mill-annealed, or as-forged), the forging reduction ratio, and part geometry. Values below represent the minimum guaranteed properties for solution-annealed forged product per ASTM B564 / EN 10272. Actual certified results typically exceed these minima.
High-Temperature Strength Retention
A defining advantage of 2.4816 over austenitic stainless steels is its superior strength retention at elevated temperature. At 700°C, 2.4816 retains approximately 90% more UTS than duplex 2205 and 60% more than 316L:
Elevated Temperature Mechanical Data
| Temperature (°C) | UTS (MPa) | 0.2% Proof Stress (MPa) | Elongation (%) |
|---|---|---|---|
| 21 (Room Temp) | 600 – 700 | 250 – 350 | 35 – 50 |
| 300 | 540 – 620 | 190 – 260 | 35 – 45 |
| 500 | 490 – 570 | 170 – 230 | 30 – 40 |
| 700 | 260 – 310 | 140 – 190 | 30 – 38 |
| 900 | 110 – 160 | 80 – 120 | 28 – 40 |
| 1,000 | 55 – 90 | 40 – 70 | 35 – 55 |
Physical Properties
| Property | Value | Unit | Condition / Notes |
|---|---|---|---|
| Density | 8.47 | g/cm³ | Room temperature |
| Melting range | 1,354 – 1,413 | °C | Solidus – Liquidus |
| Specific heat capacity | 444 | J/(kg·K) | Room temperature |
| Thermal conductivity | 14.9 | W/(m·K) | RT; increases to ~19 W/(m·K) at 500°C |
| Thermal expansion coefficient | 13.3 | ×10⁻⁶/K | 20–100°C; increases with temperature |
| Electrical resistivity | 1.03 | μΩ·m | Room temperature |
| Magnetic permeability | ~1.010 | — | Essentially non-magnetic (μ < 1.1) |
| Poisson's ratio | 0.29 | — | Room temperature |
Thermal conductivity of 2.4816 (≈15 W/m·K) is approximately one-third that of carbon steel. For thick-section forgings, this directly extends heat treatment equalisation soak times and affects quench rate calculations. Jiangsu Liangyi's standard practice allows a minimum of 1 hour per 25 mm of ruling section at soak temperature to ensure microstructural uniformity through the full cross-section.
Corrosion Resistance
Corrosion performance is the most commercially decisive attribute of 2.4816. Its high nickel content confers resistance mechanisms unavailable to iron-base alloys, making it the default specification in several demanding service environments.
Alkaline & Caustic Environments (NaOH / KOH)
2.4816 is the benchmark material for service in hot concentrated sodium hydroxide (NaOH) and potassium hydroxide (KOH). High-nickel alloys are uniquely resistant to caustic stress corrosion cracking — a failure mode that eliminates both austenitic and duplex stainless steels at NaOH concentrations above approximately 10% at elevated temperatures. The alloy is the standard specification for chlor-alkali industry evaporators and heat exchanger tube sheets operating in 50% NaOH at 120–150°C.
High-Purity Water — Nuclear Service
In nuclear power plants, 2.4816 / N06600 has been the primary material for steam generator tubing and structural components in contact with primary-circuit water. Its low corrosion rate in high-temperature deaerated water at pH 6.9–7.4 is compatible with primary coolant chemistry specifications. However, susceptibility to primary water stress corrosion cracking (PWSCC) in the sensitised condition has driven the nuclear industry to require mill-annealed (MA) or thermally treated (TT) conditions — always confirm the required heat treatment state with the nuclear system designer.
Oxidising Atmospheres at High Temperature
Up to approximately 1,175°C in air, 2.4816 forms a tightly adherent Cr₂O₃/NiO duplex oxide scale that resists spalling through thermal cycling. The alloy outperforms most stainless steel grades in cyclic oxidation testing at 1,000°C. For service temperatures consistently above 1,050°C, the higher-aluminium grade 2.4851 (NiCr23Al / Inconel 601) provides superior oxidation performance.
Environments Requiring Caution
2.4816 is not the primary recommendation in strongly oxidising acids (e.g., HNO₃, HClO₄), where the high nickel content accelerates attack. It also performs poorly in sulfur-bearing gases above 500°C (hot corrosion / sulfidation) and polythionic acid environments. For aggressive acid service, evaluate 2.4856 (Inconel 625) or 2.4819 (Hastelloy® C-276, trade name of Haynes International).
| Environment | Rating | Key Notes |
|---|---|---|
| Hot NaOH / KOH (caustic) | Excellent | Industry-standard specification; immune to caustic SCC |
| Chloride stress corrosion cracking | Excellent | Fully immune; major advantage vs all stainless grades |
| High-purity water — nuclear | Good | MA or TT condition required; PWSCC risk if sensitised |
| Oxidising atmosphere ≤ 1,000°C | Excellent | Tight adherent oxide; good cyclic oxidation resistance |
| Carburising gas atmospheres | Good | Superior to most stainless grades |
| Dilute HCl at ambient temperature | Moderate | Acceptable short-term; not a primary specification driver |
| Strong oxidising acids (HNO₃) | Poor | Not recommended; consider 316L or titanium |
| Sulfidising gas above 500°C | Poor | Sulfidation attack; consider alloy 625 or alloy 556 |
Heat Treatment
2.4816 is a solid-solution-strengthened alloy — it cannot be hardened by precipitation (age) hardening. All heat treatment is directed at stress relief, carbide dissolution, or grain refinement following hot or cold working operations.
Solution Annealing / Full Anneal
Heat to 980 – 1,050°C, hold 1 hour per 25 mm of ruling section, then rapid air cool or water quench. Dissolves intergranular carbides and homogenises the microstructure. The preferred condition for all corrosion-critical and nuclear applications. Specified per ASTM B564 and EN 10272.
Mill Anneal (MA)
Lighter anneal at 870 – 980°C, retaining some cold-work strengthening while partially dissolving carbides. Used for tubing product requiring a balance between strength and corrosion resistance. For nuclear steam generator tubing, MA condition is typically combined with thermal treatment (TT).
Thermal Treatment (TT) — Nuclear-Grade Condition
A controlled precipitation treatment at approximately 700 – 715°C following mill annealing. Designed to precipitate Cr carbides preferentially on grain faces rather than grain boundaries, improving resistance to PWSCC. Specified for nuclear steam generator tubes and structural reactor components. Requires close temperature control and documented records.
Stress Relief (Post-Welding)
Hold at 870 – 930°C for 1–4 hours depending on section thickness. Avoid slow cooling through the sensitisation window (760–427°C) on higher-carbon heats. For corrosion-critical weldments, full solution annealing is preferable to stress relief alone.
Slow cooling or isothermal exposure between 427°C and 760°C causes intergranular Cr₂₃C₆ precipitation in heats with carbon >0.05%. This sensitised microstructure is susceptible to intergranular corrosion (IGC) and primary water stress corrosion cracking (PWSCC). Always specify post-forging solution anneal with rapid cooling when delivering into corrosive service. IGC testing per ASTM A262 Practice C or E is available from Jiangsu Liangyi on request.
Forging Characteristics
2.4816 is a well-established forging material with predictable hot working behaviour, but demands more precise process control than carbon steel or even austenitic stainless grades. Understanding the forming window is essential for defect-free closed-die forgings, open-die components, and seamless rolled rings.
Hot Working Temperature Window
The recommended hot forging temperature range for 2.4816 is 1,050–1,200°C. Starting at the upper end (1,180–1,200°C) maximises workability and allows more reduction per heat without reheating. Work must not continue below approximately 930°C to prevent excessive work hardening and surface cracking. Material cooled below 900°C must be returned to full soak temperature before resuming deformation.
Forging Reduction Ratio Requirements
For critical components requiring through-thickness mechanical properties — pressure vessel flanges, nuclear tube sheets, pump impellers — a minimum forging reduction ratio of 4:1 from the ingot or bloom cross-section is generally specified. Higher reductions (6:1 or above) are preferred for parts requiring ultrasonic inspection to fine grain acceptance criteria (FBH 1.6 mm flat-bottomed hole equivalent). Insufficient reduction risks retained cast-dendrite structure and associated anisotropy in mechanical properties.
Grain Size Control
Proper temperature management and reduction rate control produces a uniform ASTM grain size of 3–5 (typical for annealed condition), offering the optimum balance of strength, toughness, and ultrasonic inspectability. Coarser grains (ASTM 1–2) increase UT attenuation and scatter, and may be rejected for ASME Section III or RCC-M nuclear applications requiring enhanced UT acceptance criteria.
"Grain boundary engineering through controlled thermomechanical processing produces 2.4816 forgings with measurably improved resistance to intergranular attack — a result that Jiangsu Liangyi controls through documented work procedure specifications (WPS) and fully traceable post-forge anneal process records." — Jiangsu Liangyi Technical Process Documentation, Jiangsu, China
For a complete product range of 2.4816 forged components — rings, flanges, discs, shafts, tube sheets, and custom closed-die shapes — visit the 2.4816 / NiCr15Fe forged rings, flanges, tube sheets and custom shapes.
Applications by Industry
2.4816 / NiCr15Fe forgings serve a remarkably broad range of industries. The table below maps primary application segments to the specific corrosion or thermal mechanism driving the specification, and the typical forged components involved.
| Industry | Typical Forged Components | Primary Specification Driver |
|---|---|---|
| Nuclear Power | Steam generator rings, tube sheets, reactor internals, vessel flanges, nozzles | PWSCC resistance; Components can be manufactured to support ASME III / RCC-M procurement packages; EN 10204 3.2 via third-party inspection |
| Chlor-Alkali / Chemical Processing | Evaporator tube sheets, valve bodies, pump casings, heat exchanger covers, fittings | Hot caustic (NaOH/KOH) immunity; chloride SCC resistance |
| Oil & Gas / Petrochemical | Wellhead components, valve trim, flanges, downhole tool bodies in H₂S service | NACE MR0175 / ISO 15156 sour service compliance; H₂S resistance |
| Aerospace & Gas Turbine | Combustion liner hardware, transition duct clips, exhaust components, furnace fixtures | Oxidation and thermal fatigue resistance above 900°C |
| Industrial Heat Treatment | Furnace muffle supports, retorts, fixtures, roller hearth components, baskets | Cyclic oxidation resistance; carburisation resistance above 700°C |
| Pulp & Paper | Digesters, liquor heaters, wash drum components, evaporator shells | Polysulfide liquor resistance; high-pH service compatibility |
| Food & Pharmaceutical | High-temperature process vessels, heat exchanger plates, fittings | Corrosion resistance in steam/organic acid service; cleanliness |
Selection Guide: When to Choose 2.4816
2.4816 is not a universal nickel alloy — it is the optimal choice for a specific cluster of service conditions. The decision matrix below identifies when 2.4816 is the logical specification and when a competing alloy should be evaluated instead.
- Service is in hot concentrated caustic (NaOH >10%, T >80°C)
- Chloride-induced SCC must be definitively excluded
- Operating temperature is 500–1,175°C in oxidising atmosphere
- Nuclear-grade components are required (ASME III / RCC-M procurement package; EN 10204 3.2 via third-party inspector)
- Carburising gas atmospheres are present above 700°C
- Long-term creep resistance is needed at 600–750°C
- NACE MR0175 / ISO 15156 sour service compliance is required
- Strong oxidising acids (HNO₃, HClO₄) → 316L or titanium
- Reducing chloride acids (HCl, H₂SO₄+Cl⁻) → 2.4819 (Hastelloy® C-276, trade name of Haynes International)
- Pitting / crevice corrosion in seawater → 2.4856 (Inconel 625) or super-duplex
- Continuous service above 1,050°C → 2.4851 (NiCr23Al / Inconel 601)
- Sulfidising atmosphere above 500°C → alloy 556 or HR-160
- Budget-constrained; manageable chloride SCC risk → duplex 2205 or 904L
Alloy Comparison Table — 2.4816 vs Competing Nickel Grades
| Property | 2.4816 (N06600) | 2.4856 (N06625) | 2.4819 (N10276) | 2.4851 (N06601) |
|---|---|---|---|---|
| Ni content | ≥72% | 58% min | 57% min | 60% min |
| Cr content | 14–17% | 20–23% | 14.5–16.5% | 21–25% |
| Key alloying addition | Fe | Mo + Nb | Mo + W | Al |
| Caustic (NaOH) resistance | Excellent | Very Good | Good | Good |
| Chloride SCC immunity | Excellent | Excellent | Excellent | Excellent |
| Pitting resistance (PREN) | Moderate | Excellent | Excellent | Moderate |
| Oxidation limit in air | ~1,175°C | ~980°C | ~1,040°C | ~1,230°C |
| Relative material cost | 1.0× | ~2.2× | ~2.8× | ~1.3× |
When you have identified 2.4816 as the right material for your application, view the full range of 2.4816 / NiCr15Fe forged components — including open-die, closed-die, and rolled ring forgings — available from Jiangsu Liangyi Co., Limited.
Frequently Asked Questions
The following answers address the most common technical and procurement questions about 2.4816 / NiCr15Fe / UNS N06600 alloy forgings, optimised for both search engines and AI assistant retrieval.