Nickel alloy grade data sheet
UNS N06635 Forgings Hastelloy® S alloy. Rings, flanges, discs, shafts and bars
Forged to customer drawing at our works in Jiangyin, China. Finished weights from 5 kg to 8 t, solution treated, ultrasonically tested and certified to EN 10204 3.1 or 3.2.
UNS N06635 Also called Hastelloy® S / Alloy S Updated 30 Aug 2026 By Jiangyin Jiangnan Metal Co., Ltd.
Summary
UNS N06635 is a wrought nickel-chromium-molybdenum high-temperature alloy, sold under the trade name HASTELLOY® S alloy and also called Alloy S. Nominal composition is 67 % nickel, 14.5–17 % chromium and 14–16.5 % molybdenum, with a lanthanum addition of 0.01–0.10 % that improves oxidation resistance. The alloy has good thermal stability, a low coefficient of thermal expansion and oxidation resistance to 1093 °C (2000 °F). It holds strength, ductility and dimensional stability through repeated heating cycles, so it is specified for gas turbine seal rings and other close-clearance hot section parts.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We forge UNS N06635 into rings, flanges, discs, shafts, sleeves, bushings, tube sheets and bars in finished weights from 5 kg to 8 t, and export worldwide against EN 10204 3.1 or 3.2 certification.
- UNS number
- N06635
- Trade name
- Hastelloy® S
- Alloy system
- Ni-Cr-Mo
- Density
- 8.75 g/cm³
- Melting range
- 1335–1380 °C
- Max oxidation service
- 1093 °C
- Forging window
- 871–1145 °C
- Solution anneal
- 1066 °C, air cool
- Specifications
- AMS 5711 / 5838 / 5873
- Certification
- EN 10204 3.1 / 3.2
What is UNS N06635?
UNS N06635 is the Unified Numbering System designation for a wrought nickel-base high-temperature alloy developed for service under severe thermal cycling. The main characteristics are:
- Thermal stability. The alloy keeps its strength and ductility after long exposure at 427–871 °C (800–1600 °F).
- Low thermal expansion. The coefficient of thermal expansion is low for a nickel alloy, so clearances in assemblies such as turbine seal rings stay predictable as the machine heats and cools.
- Lanthanum addition. A rare-earth addition of 0.01–0.10 % lanthanum improves adherence of the protective oxide scale. This is the main contributor to oxidation resistance at 1093 °C.
N06635 is a heat-resisting grade. For wet acid corrosion service the C-series alloys are normally specified instead. See the comparison in section 7.
Designations and equivalents
| UNS number | N06635 |
|---|---|
| Common trade name | HASTELLOY® S alloy (Haynes International) |
| Short name | Alloy S |
| Bar | AMS 5711 |
| Sheet, strip, plate | AMS 5838, ASTM B434 |
| Welding wire | AMS 5873 |
| Fittings | ASTM B366 |
| Forgings | Normally ordered to ASTM B564-type forging requirements or to a customer specification. Confirm the exact specification and edition at enquiry. |
No widely published EN or DIN Werkstoff equivalent exists for this grade. If a drawing calls for a European number, send it with the enquiry and we will confirm the match before quoting.
Chemical composition
Nominal composition, weight percent. Single values are maximums. Nickel is the balance. Actual heat analysis is reported on the mill certificate supplied with every forging.
| Element | Symbol | Content, % | Function |
|---|---|---|---|
| Nickel | Ni | 67 (bal.) | Base, austenitic matrix |
| Chromium | Cr | 14.5 – 17.0 | Oxidation resistance |
| Molybdenum | Mo | 14.0 – 16.5 | Solid-solution strength |
| Iron | Fe | 3.0 max | Residual |
| Cobalt | Co | 2.0 max | Residual |
| Tungsten | W | 1.0 max | Solid-solution strength |
| Copper | Cu | 0.35 max | Residual |
| Manganese | Mn | 0.30 – 1.0 | Deoxidiser |
| Silicon | Si | 0.20 – 0.75 | Deoxidiser |
| Aluminium | Al | 0.10 – 0.50 | Deoxidiser, scale adherence |
| Lanthanum | La | 0.010 – 0.10 | Oxide scale adherence |
| Carbon | C | 0.020 max | Kept low for stability |
| Phosphorus | P | 0.020 max | Impurity |
| Boron | B | 0.015 max | Grain-boundary control |
| Sulfur | S | 0.015 max | Impurity |
Mechanical and physical properties
Room temperature, solution annealed
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min. | 835 MPa | 121 ksi |
| Yield strength, 0.2 % offset, min. | 445 MPa | 64.5 ksi |
| Elongation, min. | 49 % | 49 % |
| Elastic modulus | 212 GPa | 30 700 ksi |
| Charpy V-notch, solution treated | 190 J | 140 ft·lb |
Values are typical for the solution-annealed condition and are given for design guidance. Acceptance is against the specification stated on the order. Certified values appear on the mill test report.
Elevated temperature, thin section
| Property | Test temperature | Value |
|---|---|---|
| Tensile strength | 1093 °C / 1999 °F | 110 MPa (16 000 psi) |
| Yield strength, 0.2 % offset | 1093 °C / 1999 °F | 52 MPa (7 540 psi) |
| Elongation at break, in 50.8 mm | 982 °C / 1800 °F | 46 % |
Strength falls sharply between room temperature and 1093 °C. This is normal for the grade. N06635 is selected for stability and low expansion at the top of its range rather than for load-bearing capacity there. For structural duty above 900 °C, Alloy 617 and Alloy 230 are the usual alternatives.
Physical properties
| Density | 8.75 g/cm³ (0.316 lb/in³) |
|---|---|
| Melting range | 1335 – 1380 °C (2435 – 2516 °F) |
| Maximum oxidation service temperature | 1093 °C (2000 °F) |
| Structure | Face-centred cubic, austenitic, non-magnetic |
Forging window and heat treatment
Temperature control is critical with this alloy. Working below the range causes cracking. Finishing too hot coarsens the grain and can cause rejection at ultrasonic inspection. The working bands are:
UNS N06635 process temperature bands
Open-die forging, final reduction and solution annealing, plotted against the oxidation limit of the alloy.
Heat treatment
The standard delivery condition is solution annealed at 1066 °C (1950 °F) followed by air cooling. N06635 is metallurgically stable, so cooling rate from slow furnace cooling through to an ice-brine quench has little effect on the finished mechanical properties. Where a particular balance of tensile and impact properties is required, an ageing treatment between 538 °C and 871 °C is applied. Furnaces are calibrated and charts are supplied with the certificate on request.
Machining and welding
- Machining. The alloy work-hardens. Use a rigid setup, positive rake tooling and a heavy constant feed, and avoid dwelling in the cut. Forgings can be supplied rough-machined to an agreed allowance.
- Welding. GTAW and GMAW are both suitable, with matching filler. Pre-weld and post-weld heat treatment are not normally required.
- Cold work. Ductility is high and the alloy cold works readily. It hardens by cold work rather than by precipitation.
UNS N06635 forgings we produce
All items are produced open-die or as seamless rolled rings, to customer drawing. N06635 is not held as standard stock. Parts are forged from certified billet against each order.
| Form | Size range | Typical use |
|---|---|---|
| Seamless rolled rings | OD 200 – 3000 mm | Seal rings, casing rings, bearing races |
| Forged rings | OD 100 – 1500 mm | Retainers, spacers, flange blanks |
| Flanges | DN 15 – DN 1200 | Vessel and pipework connections |
| Discs and blanks | Ø 100 – 2000 mm | Turbine discs, valve bodies, blind flanges |
| Round bars | Ø 60 – 800 mm | Shafts, stems, machining stock |
| Shafts and spindles | Ø 80 – 700 mm, L to 6000 mm | Pump and compressor rotors |
| Sleeves and bushings | OD 80 – 1200 mm | Wear surfaces, liners |
| Hollow bars | OD 120 – 900 mm | Cylinders, bored components |
| Tube sheets | to 2500 mm | Shell and tube heat exchangers |
| Blocks and squares | to 800 mm section | Valve blocks, manifolds, dies |
| Weight range | 5 kg – 8 t | Finished forging weight |
Also produced in N06635 on request: forged nozzles, valve stems, valve seat rings, gears, eccentric shafts, crankshafts, rolls, wheels and manifolds.
Where UNS N06635 forgings are used
| Industry | Components | Reason for selection |
|---|---|---|
| Gas turbines and aero engines | Seal rings, combustor hardware, transition ducts, exhaust components | Low thermal expansion keeps running clearances stable through start and stop cycles |
| Power generation | Turbine casings, preheater parts, generator components | Retains ductility after long service at 427 to 871 °C |
| Chemical and petrochemical | Pressure vessel flanges, tube sheets, forged pipe, nozzles, column and tower internals | Combined heat and oxidation resistance in process service |
| Oil and gas, offshore | Subsea and deepwater production hardware, wellhead parts, Christmas tree components | Stability under thermal cycling in critical hardware |
| Valves and flow control | Bodies, seat rings, stems and blocks for ball, gate, globe, check and plug valves | Dimensional stability of sealing faces at temperature |
| Rotating equipment | Compressor and pump shafts, spindles, gears, gearbox parts | Toughness with high-temperature fatigue strength |
| Heavy industry | Furnace rolls, mill parts, mixers, calciner and crystalliser components | Resists cyclic heating without distortion |
Most N06635 enquiries reaching us are driven by clearance control rather than by corrosion resistance. A seal ring that grows unpredictably after several thermal cycles will take a machine out of service. For that reason we record and control the finish-forging temperature on every part, together with the start temperature.
Production engineering, Jiangyin Jiangnan Metal Co., Ltd.
UNS N06635 compared with other high-temperature nickel alloys
These grades are often considered together. They are not interchangeable, and each is specified for a different service condition.
| UNS | Common name | Nominal Ni / Cr / Mo | Oxidation limit | Specified for |
|---|---|---|---|---|
| N06635 | Hastelloy® S | 67 / 15.5 / 15.5 | 1093 °C | Thermal stability with low expansion. Seal rings, close-clearance parts |
| N06002 | Hastelloy® X | 47 / 22 / 9 | approx. 1200 °C | Oxidation resistance with good fabricability. Combustors, ducting |
| N06617 | Inconel® 617 | 52 / 22 / 9 | approx. 1100 °C | Creep rupture strength at the top of the temperature range |
| N06601 | Inconel® 601 | 61 / 23 / n/a | approx. 1200 °C | Scaling and carburisation resistance in furnace hardware |
| N10276 | Hastelloy® C-276 | 57 / 16 / 16 | approx. 1040 °C | Wet corrosion, chlorides and acids. Not a heat-cycling grade |
| N08810 | Incoloy® 800H | 32 / 21 / n/a | approx. 1090 °C | Lower-cost creep service where nickel content can be reduced |
Oxidation limits are indicative continuous-service figures for comparison and are not design allowables. Composition figures are nominal midpoints.
Melting, testing and certification
Melt route
N06635 forging stock is supplied from double-melted material, either VIM plus ESR or EAF plus VOD followed by ESR, according to the specification ordered. Inclusions show as ultrasonic indications in heavy sections, so the melt route is stated on the certificate.
Non-destructive testing
- Ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921, to the quality class specified on the order
- Liquid penetrant testing to ASTM E165 where surface integrity is critical
- Dimensional inspection against the drawing, with a report
- Positive material identification by portable XRF on request
Certification
Every forging ships with a mill test report to EN 10204 3.1 covering heat number, chemical analysis, heat treatment record, mechanical test results and NDT results. Where independent witness is required, we supply EN 10204 3.2 with a third party such as TÜV, SGS, BV or Lloyd's Register attending. Country of origin certificates and export documentation are prepared in house.
Ordering and quotation
Send a drawing in PDF, DWG or STEP format, or the finished dimensions. Quotations are normally returned within one working day when the enquiry includes:
- Shape and finished dimensions, or the drawing.
- Quantity, and whether repeat orders are expected.
- Specification to certify against: AMS 5711, ASTM B564, a customer specification, or supplier standard.
- Delivery condition: as forged, rough machined with allowance, or finish machined.
- Testing required: UT class, impact testing, PMI, and whether 3.1 or 3.2 certification.
- Destination port, for freight and documentation.
Incomplete drawings are accepted. We will confirm the missing details before quoting. If N06635 is not suitable for the service conditions described, we will say so and propose an alternative grade.
Typical lead time for a first N06635 order is 30–45 days from drawing approval, depending on section size and heat treatment scheduling. Repeat parts run faster.
Frequently asked questions
What is UNS N06635?
UNS N06635 is a wrought nickel-chromium-molybdenum high-temperature alloy. Nominal composition is 67 % nickel, 14.5 to 17 % chromium and 14 to 16.5 % molybdenum, with a lanthanum addition that improves oxidation resistance. It has good thermal stability, a low coefficient of thermal expansion and oxidation resistance to 1093 °C (2000 °F).
Is UNS N06635 the same as Hastelloy S?
Yes. UNS N06635 is the Unified Numbering System designation for the alloy sold under the trade name HASTELLOY® S alloy, a registered trademark of Haynes International, Inc. It is also called Alloy S. Jiangyin Jiangnan Metal Co., Ltd. supplies forgings to this chemistry under the UNS designation.
At what temperature is UNS N06635 forged?
Between 1145 °C (2100 °F) and 871 °C (1600 °F). The final 20 % of cross-section reduction is carried out in the narrower band of 1038 °C (1900 °F) down to 816 °C (1500 °F) to control grain size in the finished forging.
What heat treatment is used for UNS N06635 forgings?
The standard condition is solution annealed at 1066 °C (1950 °F) followed by air cooling. The alloy is metallurgically stable, so cooling rate has little effect on mechanical properties. Ageing between 538 °C and 871 °C is applied where a specific balance of tensile and impact properties is required.
What is the maximum service temperature of UNS N06635?
The alloy has oxidation resistance to 1093 °C (2000 °F). It retains strength and ductility after long exposure at 427 to 871 °C (800 to 1600 °F), which is why it is specified for components subject to severe thermal cycling such as gas turbine seal rings. Load-bearing capacity at 1093 °C is low, and the grade is selected for stability rather than for strength at that temperature.
Which standards cover UNS N06635?
SAE aerospace specifications AMS 5711 for bar, AMS 5838 for sheet, strip and plate, and AMS 5873 for welding wire, together with ASTM B366 for fittings and ASTM B434 for plate, sheet and strip. Forgings are normally ordered to ASTM B564-type forging requirements or to a customer specification. Confirm the exact specification and edition at enquiry.
What shapes and sizes can you produce?
Seamless rolled rings, forged rings, flanges, discs, blocks, shafts, sleeves, bushings, tube sheets, hollow bars and round bars. Finished weights run from 5 kg to 8 t, with rolled ring outside diameters to approximately 3000 mm and forged bar diameters from 60 mm to 800 mm.
What testing and certification do you supply?
Every forging comes with a mill test report to EN 10204 3.1, or EN 10204 3.2 with third-party witness by TÜV, SGS, BV or Lloyd's Register. Ultrasonic testing is performed to ASTM A388, EN 10228-3 or SEP 1921 as specified. Chemical analysis, tensile, hardness and impact results are reported against the ordered specification.
Where can I buy UNS N06635 forgings?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, manufacturing UNS N06635 (Hastelloy S) forgings to drawing for export worldwide. Enquiries: sales@steelforgepieces.com or +86 189 2135 9659.
How is UNS N06635 different from Hastelloy X or Alloy 617?
All three are nickel-base high-temperature alloys specified for different service conditions. N06635 is specified for thermal stability and a low coefficient of thermal expansion, which suits close-clearance parts such as seal rings. Hastelloy X (N06002) is specified for oxidation resistance with good fabricability in combustor hardware. Alloy 617 (N06617) is specified for creep strength at the top of the temperature range. See the comparison table in section 7.
About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We forge to customer drawing in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, and supply engineering companies, OEMs and stockists worldwide.
This page covers what we produce in UNS N06635. For other grades, see the nickel alloy index and the full product range.
Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel: +86 189 2135 9659
Email: sales@steelforgepieces.com
Standards referenced
- AMS 5711, nickel alloy bar, UNS N06635 (SAE International)
- AMS 5838, nickel alloy sheet, strip and plate, UNS N06635 (SAE International)
- AMS 5873, nickel alloy welding wire, UNS N06635 (SAE International)
- ASTM B366, factory-made wrought nickel alloy fittings
- ASTM B434, nickel-molybdenum-chromium-iron alloy plate, sheet and strip
- ASTM B564, nickel alloy forgings
- ASTM A388, EN 10228-3, SEP 1921, ultrasonic examination of forgings
- EN 10204, types of inspection document, 3.1 and 3.2
Property data on this page is compiled from published alloy producer data and our own production records, and is given for guidance. It does not constitute a warranty. Acceptance criteria are those of the specification stated on the purchase order.