NCF 825 forgings: rolled rings, flanges, bars, discs and shafts

Published by Jiangyin Jiangnan Metal Co., Ltd. Last reviewed 22 August 2026

What NCF 825 is

NCF 825 is a Japanese Industrial Standard designation. In JIS notation the NCF prefix covers the nickel-chromium-iron corrosion and heat resisting alloys, and 825 identifies this particular composition. The grade appears in JIS G 4901 for bars, G 4902 for plate, sheet and strip, G 4903 for seamless pipe and G 4904 for heat exchanger tube. Outside Japan the same material is usually ordered as UNS N08825, or by the trade name Incoloy 825.

Metallurgically it sits between the austenitic stainless steels and the higher nickel grades. Nickel at roughly 40 per cent gives resistance to chloride stress corrosion cracking that 304 and 316 do not have. Chromium handles oxidising acids. Molybdenum resists pitting and crevice attack. The copper addition covers the reducing acids, sulphuric above all. Titanium goes in as a stabiliser, so hot worked and welded sections keep their resistance to intergranular attack without a further solution treatment.

The alloy is single phase and solid solution strengthened. There is no strengthening precipitate, which means it cannot be age hardened. Strength comes from composition, from cold work and from grain size. For forgings this has a practical consequence: the annealed properties are the properties you get, and any requirement above them has to be met through section design rather than through heat treatment.

Equivalent grades and governing standards

NCF 825 is one of the more heavily cross-referenced nickel alloys, since most standards bodies list it under a different name. The table below gives the designations covering the same composition.

Cross-references are given for guidance. National specifications differ in acceptance limits, test requirements and permitted product forms, so the grades are not always fully interchangeable. State the governing specification and its revision on both the enquiry and the order.

Forged rings, flanges, discs, shafts and tube sheets in this grade are normally ordered to ASTM B564 / ASME SB-564.

Chemical composition of NCF 825

Composition limits in weight per cent. Iron is the balance, subject to a 22.0 per cent minimum.

The titanium range of 0.60 to 1.20 per cent is the stabilising addition. Some specifications additionally require titanium to be at least five times the carbon content. Sulphur and phosphorus limits are not identical across standards: ASTM B425 permits up to 0.03 per cent sulphur. Check the limits that apply under your governing specification.

Mechanical properties

Minimum room temperature properties in the annealed condition.

Hardness here is a ceiling, not a floor. Typical annealed material runs between 120 and 180 HB. Heavy forged sections can show slightly lower proof stress than bar of the same grade, so where a section-specific guarantee matters, call it out on the order and it will be tested on a sacrificial prolongation.

Physical properties

Typical published values for annealed material, given for design guidance. They are not acceptance criteria and do not replace the values in the governing specification.

Melting, forging and heat treatment

Melting route

NCF 825 stock is melted by electric arc furnace followed by argon-oxygen or vacuum-oxygen decarburisation. Where a cleaner structure and tighter segregation control are called for, on thick sections, sour service parts or critical pressure boundary components, the heat is electroslag remelted. State the required melt route on the enquiry, because it affects both price and lead time.

Hot working

The alloy is forged from a maximum of about 1150 °C and finished above 900 °C. Heavy reduction is taken between 1150 and 1040 °C, with light finishing passes from 1040 down to 900 °C. Working below roughly 900 °C risks cracking and leaves residual strain that the later anneal will not remove. Sections are reheated between passes rather than forged down into the cold end of the range.

Heat treatment

NCF 825 is not hardenable by heat treatment. The standard treatment for forgings is a stabilise anneal at 925 to 980 °C, most often around 940 °C, held for a time proportional to section thickness and then cooled quickly. Heavy sections are water quenched, thin ones air cooled. Chromium carbides go into solution and carbon combines with titanium, so resistance to intergranular attack survives the heat treatment. If an application needs the corrosion behaviour of 825 together with higher strength, the age hardenable alternative is Incoloy 925.

Machining and welding

• Machines like a work hardening austenitic alloy. Positive rake, rigid setup, heavy positive feed, and no dwelling, since letting the tool rub will glaze the surface.
• Readily welded by GTAW, GMAW and SMAW. Matching filler is ERNiFeCr-1 to AWS A5.14. Alloy 625 filler (ERNiCrMo-3) is common on dissimilar joints and where extra pitting margin is wanted.
• Titanium stabilisation means a post-weld solution anneal is usually unnecessary for corrosion service.
• Keep interpass temperature low and heat input moderate to limit sensitisation and distortion.

Corrosion resistance

NCF 825 earns its place in mixed acid and chloride environments: stainless steels fail there, and a fully nickel based alloy is hard to justify on cost.

• Sulphuric acid. Resists both dilute and concentrated solutions across a wide temperature band. Credit for that goes to the copper addition.
• Phosphoric acid. Used in evaporators and in wet process phosphoric acid plant.
• Chloride stress corrosion cracking. The nickel content of around 40 per cent puts it well beyond 304 and 316.
• Pitting and crevice corrosion. Resisted through the molybdenum addition.
• Intergranular attack. Resisted through titanium stabilisation, including in the as-welded condition.
• Sour service. Widely used in H₂S bearing oil and gas environments. NACE MR0175 / ISO 15156 compliance can be confirmed on request.
• Nitric and organic acids, caustic, seawater. Good general resistance.

On service temperature, corrosive duty normally keeps the alloy below about 540 °C. Long exposure above that band can precipitate secondary phases that cut both corrosion resistance and ductility. Where higher continuous temperature is part of the duty, Incoloy 800H, Incoloy 800HT or Inconel 625 is the more suitable grade.

Forged product forms and size range

Available forms

• Seamless rolled rings. Plain, stepped and contoured profiles, ring rolled from a pierced and upset preform.
• Forged flanges. Weld-neck, blind, slip-on, orifice, long weld-neck and special bore.
• Round bars and billets. Forged, peeled or rough turned.
• Discs and blanks. Upset forged for closure heads, blind covers and machining blanks.
• Shafts and spindles. Plain, stepped and flanged.
• Sleeves, bushings and hollow bars. Forged and bored.
• Tube sheets and tube plates. For shell and tube heat exchangers.
• Valve components. Bodies, bonnets, stems, seat rings and blocks.
• Nozzles, manifolds, pipe and tube. Forged and bored to drawing.

Size and weight envelope

Delivery condition is as forged, rough machined or finish machined to drawing. Standard supply condition is stabilise annealed. Send the drawing to sales@steelforgepieces.com and the forged weight and price come back with the quotation.

Applications by industry

NCF 825 forgings get specified where a component sees acid, chloride or sour service, and where a stainless steel would be at risk of stress corrosion cracking or pitting.

Testing, inspection and certification

Every NCF 825 forging leaves the works with a material certificate traceable to the melt number. Standard scope and options are listed below.

Third party inspection by BV, SGS, TÜV, Lloyd's Register or the client's own inspector can be arranged. Sour service parts can be supplied with NACE MR0175 / ISO 15156 compliance confirmation.

Frequently asked questions about NCF 825

About the manufacturer

Page maintained by Jiangyin Jiangnan Metal Co., Ltd. Last reviewed 22 August 2026. Data compiled from JIS G 4901 and G 4902, ASTM B564 and ASTM B425, and from published typical values for UNS N08825. Values are given for guidance and do not replace the governing specification.

Closely related grades

Buyers comparing NCF 825 usually evaluate the following as well. Each links to its own datasheet.

• Incoloy 825 forgings, the same composition under its trade name.
• Incoloy 925 forgings, age hardenable, for higher strength with similar corrosion behaviour.
• Incoloy 800H and Incoloy 800HT, for creep service above 540 °C.
• Inconel 625 forgings, higher molybdenum, for more severe pitting and crevice conditions.
• Hastelloy C-276 forgings, for the most aggressive mixed acid service.
• Incoloy 945 forgings, a high strength sour service alternative.