Alloy 45TM — NiCr28FeSiCe / 2.4889 Metallurgical Guide
Key takeaways
- Names: Alloy 45TM = NiCr28FeSiCe = 2.4889 = UNS N06045 — one alloy, several standard designations.
- Chemistry: ≥ 45% Ni, 26–29% Cr, 21–25% Fe, 2.5–3.0% Si, 0.03–0.08% Ce.
- Why it works: silicon forms a silica diffusion barrier; cerium keeps the oxide scale from spalling during thermal cycling.
- Resists: oxidation, sulfidation and carburisation in hot, aggressive process gases.
- Temperature: continuous service to ~1000 °C, plus toughness toward cryogenic lows.
- Forms: forged bars, seamless rolled rings, discs, shafts, flanges and custom forgings.
A heat-resistant alloy defined by its oxide skin, not just its nickel
Most people classify high-temperature alloys by their nickel content, and Alloy 45TM does sit comfortably in the nickel-base family with a guaranteed minimum of 45% nickel. But that number alone misses the point. What separates NiCr28FeSiCe (2.4889) from a conventional 800-series or 600-series grade is not the base metal — it is the deliberate 2.5–3.0% silicon addition paired with a trace of cerium. Those two elements change how the alloy protects itself.
When a bare heat-resisting metal is heated in an aggressive gas, it grows an oxide scale on its surface. Whether that scale protects the metal or peels away and exposes fresh metal to attack decides the component's life. Alloy 45TM is formulated so the scale stays thin, dense and firmly anchored — even when the temperature swings up and down thousands of times over a plant's operating life. That single behaviour is why it is specified for the harshest thermal-process environments rather than a cheaper stainless.
In forged form, the alloy carries these properties into heavy, load-bearing sections — furnace rolls, hangers, rings, discs, valve bodies and pressure parts — where a thin-walled tube or sheet would not survive the mechanical duty. That combination of chemistry and forged integrity is the reason it appears on drawings for waste-to-energy plants and gasifiers worldwide.
Chemical composition of Alloy 45TM
Typical wt.% ranges to DIN EN 10095 / VdTÜV 519. Balance is nickel; iron and chromium form the structural backbone, while silicon and cerium do the protective work.
Values are nominal and for orientation only. Mill test certificates to EN 10204 3.1 (and 3.2 with third-party inspection) are available on request for each heat, confirming the actual analysis against the applicable standard and the customer specification.
Why silicon & cerium matter: the self-anchoring oxide layer
The whole performance story of Alloy 45TM plays out in a scale only a few micrometres thick. As the alloy heats, chromium diffuses to the surface and forms a chromium-oxide (Cr₂O₃) layer — the same starting point as most stainless steels. What is different here happens underneath it.
The high silicon content forms a thin, glass-like silica (SiO₂) sub-layer at the metal–oxide interface. This inner film slows diffusion in both directions, so the chromia scale grows far more slowly and stays thin. A thin scale is a scale that does not crack.
Cerium plays a smaller but decisive role. As a reactive rare-earth element it segregates to the oxide grain boundaries and dramatically improves scale adhesion. When a component thermally cycles, a poorly-adhered scale spalls off and the bare metal must re-oxidise, consuming chromium each time. Cerium keeps the scale attached, so the alloy stops burning through its own protection.
Together, silicon and cerium turn a good chromia-former into an alloy that keeps its skin intact across thousands of thermal cycles — the metallurgical reason a part in Alloy 45TM outlasts one in a plain 25-20 stainless in the same duty.
Key properties: what Alloy 45TM resists — and why
Non-scaling to high temperature
The slow-growing, adherent chromia/silica scale resists oxidation up to roughly 1000 °C, with minimal weight loss even under repeated heating and cooling.
Stable in SO₂-rich gases
Elevated nickel and chromium, plus the protective sub-layer, resist the sulfur-bearing combustion gases found in incinerators and refinery heaters.
Barrier to carbon ingress
The dense surface scale limits carbon diffusion into the metal, protecting components in reducing, carbon-rich atmospheres such as coal gasifiers.
Scale that stays put
Cerium-enhanced adhesion means the oxide does not spall during ramps and trips — the failure mode that shortens the life of lesser heat-resisting steels.
Stable austenite
A single-phase, solid-solution austenitic matrix gives predictable behaviour and good structural stability over long service exposures at temperature.
Forgeable & weldable
The alloy hot-forges into heavy sections and welds with matching or nickel-base fillers, allowing rings, discs and complex parts to be built and repaired.
Alloy 45TM vs. Alloy 800H vs. 310 stainless
A quick engineering comparison of three common heat-resisting grades. Alloy 45TM's higher nickel and much higher silicon are what set it apart in aggressive, cycling atmospheres. Figures are nominal; always confirm against the applicable standard.
| Property | Alloy 45TM | Alloy 800H | 310 Stainless |
|---|---|---|---|
| Nickel (nom.) | ≥ 45% | 30–35% | 19–22% |
| Chromium (nom.) | 26–29% | 19–23% | 24–26% |
| Silicon | 2.5–3.0% | ≤ 1.0% | ≤ 1.5% |
| Cerium (rare earth) | Yes | No | No |
| Oxidation resistance | Excellent | Good | Good |
| Sulfidation resistance | Excellent | Moderate | Moderate |
| Scale spalling on cycling | Very low | Moderate | Moderate |
| Relative cost | Higher | Medium | Lower |
Bottom line: choose Alloy 45TM where the gas is hot, sulfur- or chloride-bearing, and the temperature cycles; a leaner grade is enough only for milder, more stable oxidising duty.
Service temperature range
Alloy 45TM stays tough across a wide window — from cryogenic pressure-vessel service down toward -195 °C, up through the 500–750 °C band typical of coal gasification and waste incineration, and on to its high-temperature ceiling near 1000 °C where the protective scale does its most important work. Solution-annealed material is the standard delivery condition for these duties.
Standards & designations: the same alloy, many names
Procurement teams meet this material under different national systems. Confirm equivalence against the drawing — the nominal Ni-Cr-Fe-Si-Ce chemistry is the same.
| System | Designation | Note |
|---|---|---|
| EN material no. | 2.4889 | Werkstoffnummer |
| EN symbol | NiCr28FeSiCe | Short name |
| UNS (USA) | N06045 | Unified Numbering System |
| Common name | Alloy 45TM | Industry usage |
| Product standard | DIN EN 10095 | Heat-resisting steels & alloys |
| Material data sheet | VdTÜV 519 | Reference sheet for the grade |
Applications for forged Alloy 45TM
Waste-to-energy incineration
Grate bars, furnace internals, hangers and supports exposed to chloride- and sulfur-laden flue gas at fluctuating temperature.
Coal & biomass gasification
Reactor internals and pressure parts operating in reducing, carbon-rich atmospheres that would carburise ordinary alloys.
Refinery & petrochemical furnaces
Furnace fittings, tube sheets and flanges in sulfidizing combustion environments demanding heat and corrosion resistance.
Industrial furnace construction
Rolls, rings, discs and radiant-section hardware for heat-treatment and process furnaces cycling to high temperature.
Recuperators & heat exchangers
High-temperature gas-side components where a stable, non-spalling oxide scale extends maintenance intervals.
Pressure vessels & caustic service
Wetted parts in caustic-solution and process environments across a broad temperature range, forged to code.
Where to source forged Alloy 45TM
This article explains the metallurgy of Alloy 45TM. For available product forms, dimensional ranges, tolerances, delivery condition and pricing, please refer to the dedicated product page — that is where the commercial specifications and quotation details live. Jiangsu Liangyi manufactures Alloy 45TM (2.4889 / UNS N06045) to customer drawings.