1 Overview: What Is 2.4854 (NiFe33Cr25Co)?
The designation 2.4854 — written as NiFe33Cr25Co under the DIN/EN naming convention — identifies a solid-solution reinforced Fe-Ni-Cr heat-resistant superalloy engineered specifically for continuous service in extreme high-temperature, carburizing, and sulfidizing environments. It belongs to the iron-nickel-chromium alloy family that balances elevated-temperature mechanical strength with exceptional resistance to multiple simultaneous corrosion mechanisms — a combination that is surprisingly rare among commercially available alloys.
Unlike precipitation-hardened nickel superalloys that rely on γ′ (Ni₃Al/Ti) or γ″ (Ni₃Nb) strengthening phases, 2.4854 achieves its high-temperature performance through solid-solution strengthening — primarily from cobalt, silicon, and manganese additions into the austenitic Fe-Ni-Cr matrix. This mechanism delivers more stable long-term creep properties without the risk of overaging or phase instability that can affect precipitation-hardened alloys above 850°C.
2.4854 is not simply "an upgraded stainless steel." Its nominal composition — approximately 33% Fe, 25% Cr, 20% Ni, with cobalt additions — places it in a unique performance zone between conventional heat-resistant stainless steels and high-cost premium nickel superalloys, delivering a cost-performance ratio that makes it the preferred material for many ultra-high-temperature structural applications where both carburization and sulfidation occur simultaneously.
In the industrial supply chain, 2.4854 is procured primarily as 2.4854 (NiFe33Cr25Co) forging parts, bars, discs, and custom machined components. Its proven service life exceeds 4 years at 1095°C in real power generation environments, as documented in Jiangsu Liangyi's project case portfolio. Jiangsu Liangyi supplies 2.4854 forging parts globally to customers in the United States, Germany, Norway, the United Kingdom, France, the Netherlands, Saudi Arabia, the UAE, Singapore, Australia, Japan, South Korea, India, and Canada, with 24-hour RFQ response and EN 10204 3.1 mill test certificates supplied as standard.
2 Chemical Composition
The chemical composition of 2.4854 is tightly controlled under EN 10095 to ensure consistent high-temperature performance. The nominal ranges are as follows:
| Element | Symbol | Min % | Max % | Function in the Alloy |
|---|---|---|---|---|
| Chromium | Cr | 24.0 | 26.0 | Primary oxidation & sulfidation barrier — forms Cr₂O₃ protective scale |
| Nickel | Ni | 19.0 | 22.0 | Stabilizes austenitic matrix; base for corrosion resistance |
| Iron | Fe | Balance (~33%) | Cost-effective matrix filler; improves forgeability | |
| Silicon | Si | 1.0 | 2.5 | Critical SiO₂ sub-scale — blocks carburization where Cr₂O₃ fails |
| Cobalt | Co | — | 3.0 | Solid-solution strengthener; improves creep resistance at 900°C+ |
| Manganese | Mn | — | 2.0 | Deoxidizer; stabilizes austenite; aids hot workability |
| Carbon | C | — | 0.15 | Controlled to limit sensitization risk (Cr₂₃C₆ precipitation) |
| Phosphorus | P | — | 0.030 | Tramp element — causes grain boundary embrittlement if excess |
| Sulfur | S | — | 0.015 | Strictly controlled — excess S accelerates sulfidation attack |
Why Silicon (1.0–2.5%) Is the Critical Differentiator
The elevated silicon specification is not incidental. Silicon forms a thin, adherent SiO₂ sub-scale beneath the primary Cr₂O₃ oxide layer. In carburizing atmospheres — where carbonaceous gases (CO, CH₄) at high temperature drive carbon into the alloy lattice — this SiO₂ layer acts as a diffusion barrier that Cr₂O₃ alone cannot provide. Without sufficient Si, catastrophic internal carburization can destroy component cross-sections within months of service. This dual-layer oxide mechanism is a defining engineering feature of 2.4854 and distinguishes it from lower-Si Fe-Ni-Cr alloys.
Elemental Breakdown — Visual Reference
3 Mechanical & Physical Properties
The following data represents minimum room-temperature mechanical properties for 2.4854 in the solution-annealed condition (1050–1120°C, water quenched or air cooled), consistent with EN 10095 requirements. Actual values from certified mill test certificates (EN 10204 3.1) may vary by product form and section size.
Elevated-Temperature Tensile Data
The primary engineering justification for specifying 2.4854 over conventional stainless steels is its retention of strength and creep resistance at temperatures above 900°C. The following table presents typical elevated-temperature tensile data:
| Test Temp. | Rp0.2 (MPa) | Rm (MPa) | Elongation (%) | Design Note |
|---|---|---|---|---|
| 20°C | ≥ 210 | ≥ 450 | ≥ 30 | Room temperature baseline |
| 400°C | ~170 | ~390 | ~32 | Good strength retention |
| 600°C | ~150 | ~340 | ~35 | Suitable for moderate structural loads |
| 800°C | ~110 | ~260 | ~40 | Adequate; creep starts to govern |
| 1000°C | ~60 | ~140 | ~55 | Creep is now the design-limiting factor |
| 1095°C | ~40 | ~100 | ~65 | Upper service limit — proven in turbine use |
Above 900°C, creep — not tensile strength — governs component life. Always use creep rupture data (stress-to-rupture for 100,000 hours at operating temperature) rather than short-term tensile values when dimensioning structural 2.4854 components at elevated service temperatures.
4 Corrosion Resistance Performance
2.4854's corrosion resistance profile is multidimensional. It is specifically engineered to provide reliable, simultaneous resistance across three distinct corrosion mechanisms that commonly coexist in industrial process environments — a combination no single-mechanism alloy can match at this price point.
4.1 — High-Temperature Oxidation Resistance
The 24–26% chromium content ensures rapid and complete formation of a continuous, adherent Cr₂O₃ protective scale upon first thermal exposure. This scale is self-healing under cyclic thermal conditions, provided minimum oxygen partial pressure is available. Tested per ISO 21608, 2.4854 exhibits negligible mass loss (< 0.15 mg/cm²) after 1,000 hours at 1050°C in dry air — significantly better than AISI 310S at identical conditions.
4.2 — Carburization Resistance
In carburizing atmospheres (carbon activities ac > 1), the silicon sub-scale provides the critical second line of defense. When the primary Cr₂O₃ layer is locally disrupted, the underlying SiO₂ prevents carbon ingress at the grain boundary level. Field data from ethylene cracking furnace components confirm that 2.4854 tubes maintain wall thickness within specification after 4+ years of continuous service at 950–1050°C in high-ac cracking gas environments.
4.3 — Sulfidation Resistance
Sulfidizing environments (H₂S, SO₂, polysulfides) are particularly destructive because sulfur preferentially attacks chromium, consuming the protective oxide from within. The high Cr content of 2.4854 provides a large chromium reservoir that delays scale breakdown. The nickel-based austenitic matrix is also intrinsically more resistant to sulfide penetration than iron-based ferritic alloys. 2.4854 is fully compliant with NACE MR0175 / ISO 15156-3 composition limits for sour service.
When comparing 2.4854 against 2.4663 (NiCr23Co12Mo) or Alloy 601 (2.4851): 2.4854 excels where carburization and sulfidation coexist. 2.4663 has a higher oxidation ceiling but lower sulfidation resistance in strongly reducing atmospheres. The right choice depends on your specific process gas chemistry — contact our team for a free application-specific recommendation.
5 International Equivalent Grades & Standards
Procurement of 2.4854 forgings requires specifying the correct standard for your compliance framework. The following table maps 2.4854 across major international standards systems:
| Standard System | Designation | Document | Product Forms |
|---|---|---|---|
| DIN / EN | 2.4854 / NiFe33Cr25Co | EN 10095 | Strip, sheet, plate, rod, bar, wire |
| EN (Forgings) | NiFe33Cr25Co | EN 10273 / EN 10269 | Pressure-bearing forgings, fasteners |
| ASTM (nearest) | UNS N06025 (similar) | ASTM B564 / B166 | Forgings, rod & bar — verify composition |
| GB/T (China) | 2Cr25Ni20Si2 | GB/T 1221 | Bars — verify against project spec |
| ASME (Power Gen.) | Per project specification | ASME Section II Part D | Material property tables for code calculations |
For API 6A, NACE MR0175, ASME, or nuclear-adjacent applications, always specify the exact standard, product form standard, and applicable clause in your purchase order. Do not rely solely on trade names. Jiangsu Liangyi supplies EN 10204 3.1 mill test certificates as standard with every shipment. EN 10204 3.2 third-party witnessed inspection is available on request. Note: API 6A product certification (monogram licence) is held by the end equipment manufacturer, not by Jiangsu Liangyi as the material/forging supplier.
6 Forging & Fabrication Characteristics
One of 2.4854's most valuable engineering advantages is its excellent manufacturability. Unlike many precipitation-hardened superalloys that demand tightly controlled forging temperatures and very high forging forces, 2.4854 offers a wide hot-working window combined with moderate flow stress — making it well-suited for large, complex near-net-shape forgings at competitive lead times.
Billet Heating — 1100 to 1200°C
Ingots are heated uniformly in gas-fired or electric furnaces. Soak time is calculated per cross-section thickness to ensure full thermal equilibration to the core. Temperatures above 1230°C risk incipient melting at grain boundaries — a critical process control point that our thermal monitoring system enforces automatically.
Open Die Forging — Finish Temperature ≥ 950°C
Using 2,000–6,300-ton hydraulic presses, the alloy is worked to achieve a minimum forging reduction ratio of 3:1 for bars and discs, and 4:1 for rings. Jiangsu Liangyi produces custom 2.4854 open die forgings and seamless rolled rings from 30 kg to 30,000 kg per piece. This ensures complete breakdown of the as-cast dendritic structure and achieves uniform grain size (typically ASTM 4–6 for most applications).
Seamless Ring Rolling — Up to 6,000 mm OD
For rings, seamless ring rolling produces near-net-shape components with superior circumferential grain flow orientation vs. cut-from-plate alternatives. This grain alignment significantly improves hoop stress fatigue life — critical for turbine guide rings, pressure vessel flanges, and seal rings.
Solution Annealing — 1050–1120°C, Rapid Cooling
Post-forging solution annealing dissolves any carbides or secondary phases precipitated during working, restoring a fully austenitic microstructure with optimal corrosion resistance. Cooling must be rapid enough to prevent sensitization (Cr₂₃C₆ precipitation at grain boundaries between 650–900°C).
NDT & Final Inspection — 100% Ultrasonic Testing
All 2.4854 forgings undergo 100% UT per EN 10228-3 or ASTM A388, plus surface inspection by liquid penetrant (PT) or magnetic particle testing (MT) where geometry permits. Final dimensional inspection and hardness verification complete the acceptance protocol before shipment.
Welding & Machinability
2.4854 exhibits good weldability using matching composition fillers or matching or compatible nickel-base filler metals (such as AWS ERNiCr-3 class) for dissimilar joints. Preheat is generally not required for sections below 25mm. Interpass temperature should be controlled below 150°C to minimize heat-affected zone width and sensitization risk.
In the annealed condition, 2.4854 machines comparably to austenitic stainless steels with the characteristic work-hardening behavior of FCC alloys. Sharp tooling, high feed rates, and adequate coolant are essential to prevent built-up edge and excessive tool wear.
7 Industrial Applications
2.4854 forging parts are deployed in the most demanding thermal environments across multiple major industries. Its application space is defined by the coincidence of three conditions: sustained high temperature (>800°C), aggressive gas atmosphere (carburizing or sulfidizing), and long-term structural integrity requirements without scheduled replacement.
Power Generation
Gas and steam turbine guide rings, seal rings, labyrinth rings, rotor end rings, casing rings, and turbine shafts for AUSC power plants operating continuously at 1000–1095°C.
Oil & Gas / Refining
Valve bodies, valve seat rings, pump casings, impellers, pressure vessel shells, and heat exchanger components for sour service, NACE-compliant petrochemical environments.
Nuclear Power (Adjacent)
Flow limiter Venturi forgings, pressurizer surge line tubes, reactor nozzles, and primary pump flywheels requiring full material traceability from heat to finished part.
Industrial Furnaces
Thermocouple protection tubes, radiant tubes, retorts, recuperators, and chemical reactor parts for carburizing furnaces, annealing lines, and sintering equipment.
Chemical Processing
Reactor internals, reformer tube supports, catalyst grid structures, and heat exchanger components for ammonia synthesis, ethylene cracking, and methanol production.
Waste-to-Energy
Grate supports, boiler tube shields, flue gas treatment components exposed to aggressive combustion atmospheres containing SOₓ, HCl, and alkali deposits.
8 Proven Project Cases
660MW Thermal Power Plant — Gas Turbine Components
Jiangsu Liangyi supplied 2.4854 turbine parts for a 660MW thermal power plant in Southeast Asia. Components including turbine guide rings, seal rings, and labyrinth rings were required to operate continuously at 1095°C in a combined oxidizing and locally carburizing atmosphere created by combustion byproducts.
After more than 4 years of continuous operation, all components have maintained stable performance with no material failures, no measurable dimensional deviation beyond design tolerances, and no oxide scale spallation events requiring unplanned maintenance. This project demonstrated the alloy's superior thermal fatigue resistance under cyclic temperature variations during plant start-up and shutdown cycles.
Standards met: Material properties per ASME standards for high-temperature power generation equipment. EN 10204 3.1 MTC supplied with every shipment.
Large Refinery Expansion — Valve & Pump Components, Saudi Arabia
For a major refinery project in Saudi Arabia requiring components for combined carburization and sulfidation service, Jiangsu Liangyi supplied 2.4854 valve bodies, valve seat rings, pump casings, and heat exchanger parts. The environment involved hydrogen sulfide at elevated partial pressure combined with high-temperature hydrocarbon streams — one of the most aggressive corrosion scenarios in the industry.
All products passed the customer's full pressure testing protocol. Material chemical composition and mechanical properties were verified against NACE MR0175 / ISO 15156-3 hardness and composition requirements, with API 6A alignment confirmed through third-party inspection.
9 Alloy Comparison: How 2.4854 Stacks Up
Choosing the right alloy for a high-temperature application requires comparing performance across multiple axes simultaneously. The following assessment is based on Jiangsu Liangyi's 25+ years of production and application engineering experience:
| Alloy | Max Temp. | Oxidation | Carburization | Sulfidation | Forgeability | Cost |
|---|---|---|---|---|---|---|
| 2.4854 (NiFe33Cr25Co) | 1095°C | ●●●●● | ●●●●● | ●●●●● | ●●●●● | Medium |
| AISI 310S (1.4845) | 1050°C | ●●●●○ | ●●●○○ | ●●●○○ | ●●●●● | Low |
| 2.4663 (NiCr23Co12Mo) | 1150°C | ●●●●● | ●●●●○ | ●●●○○ | ●●●●○ | High |
| Alloy 601 (2.4851) | 1200°C | ●●●●● | ●●●●○ | ●●○○○ | ●●●●○ | High |
| 1.4828 (NiCr20Si2Al) | 1050°C | ●●●●○ | ●●●●○ | ●●○○○ | ●●●●● | Low–Med |
The table shows 2.4854's core competitive advantage: it is the only alloy in this group achieving top-tier ratings in all three corrosion mechanisms simultaneously, while maintaining excellent forgeability and a medium (not premium) material cost. For applications where carburization and sulfidation coexist — common in petrochemical reforming, waste incineration, and combustion systems — 2.4854 is typically the most cost-effective specified solution.
10 How to Specify & Source 2.4854 Forgings
To ensure you receive compliant, traceable 2.4854 forging parts that meet your design intent, the purchase order or RFQ should specify the following minimum information:
| Specification Item | What to State | Why It Matters |
|---|---|---|
| Material Designation | 2.4854 per EN 10095 | Prevents substitution with lower-grade alloys |
| Product Form Standard | EN 10273 / EN 10269 / ASTM B564 | Governs required mechanical properties & testing |
| Heat Treatment Condition | Solution annealed (specify temp range) | Ensures correct microstructure & corrosion resistance |
| MTC Certificate Type | EN 10204 3.1 (standard) or 3.2 (TPI witnessed) | Defines traceability and inspection authority |
| NDT Requirements | 100% UT per EN 10228-3 + PT/MT on machined surfaces | Detects subsurface inclusions and surface defects |
| Service Standard | NACE MR0175, API 6A, ASME, etc. | Triggers correct composition/hardness limits |
| Dimensional Tolerance | Per drawing + applicable forging standard | Prevents oversize/undersize delivery |
Jiangsu Liangyi has supplied 2.4854 forging parts to projects in Southeast Asia, the Middle East, Germany, and 50+ countries. Standard lead time is 3–6 weeks depending on complexity and weight. We respond to all technical RFQs within 24 hours. Contact: sales@jnmtforgedparts.com · view full 2.4854 forging parts specifications →