UNS N19909 (Alloy 909) Forgings

UNS N19909 at a glance

Grade

Alloy 909 (also written Incoloy® 909, 909 alloy, VAR 909)

UNS number

N19909

Alloy family

Nickel-cobalt-iron, precipitation hardenable, low expansion

Aerospace specifications

AMS 5884 · AMS 5892 · AMS 5893

Nominal composition

38 Ni · 14 Co · 4.7 Nb · 1.5 Ti · 0.4 Si · balance Fe

Chromium

1.0% max, so the alloy is effectively chromium free

Coefficient of expansion

7.7 µm/m·°C (4.3 × 10⁻⁶ in/in·°F), 20 °C to inflection point

Inflection (Curie) point

400–455 °C (750–850 °F)

Density

8.19 g/cm³ (0.296 lb/in³)

Melting range

1395–1430 °C (2540–2610 °F)

Young's modulus

159 GPa (23.0 × 10³ ksi), nearly constant to 650 °C

Tensile strength, aged

1276 MPa (185 ksi) typical at room temperature

Yield strength, aged

1034 MPa (150 ksi) typical at room temperature

Service ceiling

About 650 °C (1200 °F); coating usually required for oxidation

Delivery condition

Solution treated, or solution treated + double aged

Certification

EN 10204 3.1 standard; 3.2 third-party witnessed on request

Forged by

Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China

Related grades

Alloy 903 (N19903), Alloy 907 (N19907), Inconel 783, Inconel 718

Table 1. Summary compiled by Jiangyin Jiangnan Metal Co., Ltd. from Special Metals technical bulletin SMC-077 and the SAE AMS specifications listed above.

What UNS N19909 is, and when to specify it

Specify UNS N19909 when a rotating or static gas-turbine part has to keep a tight clearance across a wide temperature swing and still carry load. Ordinary superalloys such as Inconel 718 grow roughly twice as much per degree, so a seal or shroud made from them opens up as the engine warms. Alloy 909 was designed so the expansion curve stays flat to about 425 °C and only then climbs, which lets a designer hold running clearances, raise power output and improve fuel efficiency.

The alloy is one of a family of low-expansion superalloys. Alloy 903 came first and suffered from notch brittleness caused by stress-accelerated grain-boundary oxidation (SAGBO): a notched bar failed far earlier than a smooth bar at the same stress. Alloy 907 improved on it, and Alloy 909 added 0.25–0.50% silicon, which restores notch-rupture strength using conventional processing and heat treatment rather than long over-ageing cycles. Creep crack-growth rates for Alloy 909 tested at 540 °C in air are much lower than for Alloy 903, and its notched low-cycle fatigue life is far better.

The penalty is oxidation. Chromium raises thermal expansion, so it is held to 1.0% maximum and the alloy carries no protective chromia scale. In cyclic oxidation at 650 °C, Alloy 909 loses weight steadily where Inconel 718 with 19% chromium does not. In sustained hot-gas paths a diffusion or overlay coating is normally applied. Where the coating is unwanted, Inconel® 783 is the usual successor: oxidation resistance to 704 °C, SAGBO resistance close to alloy 718, about 5% lower density, at a higher price.

Two other properties matter at the design stage. Alloy 909 resists embrittlement by high-pressure hydrogen, which is unusual for a material of this strength and is why it appears in rocket-engine hardware. Its modulus of elasticity also barely moves: Young's modulus changes by about +3.5% at 480 °C and −1.8% at 650 °C against the room-temperature value, so spring rates and natural frequencies stay predictable.

Chemical composition of UNS N19909

The composition of UNS N19909 is 35.0–40.0% nickel, 12.0–16.0% cobalt, 4.3–5.2% niobium, 1.3–1.8% titanium, 0.25–0.50% silicon, 0.15% max aluminium, 0.06% max carbon and the balance iron (about 42%). Every heat we forge is supplied with a ladle analysis on the mill certificate; product analysis on the finished forging can be added on request.

Sources: Ni, Co, Nb, Ti, Si, Al, C and Fe limits are the limiting chemical composition published by Special Metals for INCOLOY alloy 909 (bulletin SMC-077). Cr, Mn, Cu, B, P and S are the residual limits commonly written into aerospace purchase specifications for the grade. Order to the AMS specification and revision shown on your drawing; we certify to whichever limits the order states.

Melting practice matters as much as the analysis. Alloy 909 is normally vacuum induction melted and then vacuum arc remelted (VIM + VAR), which is where the designation VAR 909 comes from. For aerospace rotating hardware, double or triple melt is usually mandatory; for industrial gas-turbine static parts, VIM + ESR is sometimes accepted. State the melt route in your enquiry, because it changes both price and lead time.

Thermal expansion of UNS N19909

UNS N19909 has a mean coefficient of thermal expansion of about 7.7 µm/m·°C (4.3 × 10⁻⁶ in/in·°F) from room temperature up to the inflection point near 425 °C (800 °F), which is roughly half the rate of alloys of comparable strength. At the inflection point the alloy changes from ferromagnetic to paramagnetic and the coefficient begins to climb; by 650 °C the mean value has risen to about 10.3 µm/m·°C. Below that knee, a 909 seal ring grows about 0.4 mm across a 500 mm diameter when heated 100 °C; an Inconel 718 ring of the same size grows about 0.7 mm.

Values are nominal and intended for design screening and clearance estimates, not for final stress analysis. Confirm against the material specification and the mill certificate for the heat supplied.

Mechanical properties of UNS N19909 forgings

Age-hardened UNS N19909 typically develops 1276 MPa (185 ksi) tensile strength, 1034 MPa (150 ksi) yield strength at 0.2% offset, 15% elongation and 30% reduction of area at room temperature, and retains 1034 MPa tensile and 862 MPa yield at 650 °C (1200 °F). All values below are for material given the standard cycle: solution treat 980 °C for 1 hour, air cool, then age 720 °C for 8 hours, furnace cool at 55 °C per hour to 620 °C, hold 8 hours, air cool.

Source: Special Metals technical bulletin SMC-077 for INCOLOY alloy 909. Typical values, not specification minimums. AMS purchase specifications state their own minima; the mill test certificate issued with each forging governs acceptance.

Stability after long exposure

Room-temperature properties are retained after 1000 hours at temperature, which shows that no embrittling phase forms in service. Strength actually rises slightly after exposure at 595 °C, then falls away once the exposure reaches 705 °C.

Source: Special Metals technical bulletin SMC-077. The drop after 705 °C exposure is the practical reason the alloy is limited to about 650 °C in sustained service.

Rupture, fatigue and notch behaviour

Notch-bar rupture tests at 540 °C give strengths comparable with smooth-bar tests. That is what the silicon addition buys, and where the grade parts company with Alloy 903. Notched low-cycle fatigue life at 540 °C is much longer than Alloy 903 under the same net stress. Stress-rupture results for low-expansion superalloys are sensitive to specimen alignment during testing, so compare data only where the test method matches.

Physical and thermal properties

UNS N19909 has a density of 8.19 g/cm³, melts between 1395 °C and 1430 °C, and has a Young's modulus of 159 GPa that stays within about 3.5% of its room-temperature value all the way to 650 °C. That constant modulus, combined with low expansion and relatively high thermal conductivity, is what makes the alloy resistant to thermal fatigue and thermal shock.

Source: Special Metals technical bulletin SMC-077, values for age-hardened material. Curie temperature varies within the range shown according to the exact heat chemistry.

Source: Special Metals technical bulletin SMC-077, dynamic method on age-hardened material.

Heat treatment of UNS N19909 forgings

The standard heat treatment for UNS N19909 is a solution anneal at 980 °C (1800 °F) for 1 hour followed by air cooling, then a double age: 720 °C (1325 °F) for 8 hours, furnace cool at 55 °C per hour (100 °F per hour) to 620 °C (1150 °F), hold 8 hours, air cool. The controlled furnace cool between the two ageing steps is not optional. It develops the precipitate distribution that gives the alloy its strength.

1. Solution anneal at 980 °C (1800 °F), 1 hour minimum. Allow roughly one hour per 25 mm of ruling section. Air cool. Rough machining should be done in this condition, since the alloy is far more tractable before ageing.
2. First age at 720 °C (1325 °F) for 8 hours. Charge into the furnace at or below temperature and hold at heat, counting time from when the load reaches temperature.
3. Controlled furnace cool at 55 °C/h (100 °F/h) to 620 °C (1150 °F). That is about 1 hour 50 minutes of ramp. Cooling faster loses strength; the ramp rate should be recorded on the furnace chart.
4. Second age at 620 °C (1150 °F) for 8 hours, then air cool. Total cycle at temperature is about 18 hours, excluding heating and loading time.

Forgings are commonly bought in the solution-treated condition so the buyer can rough machine, then age after machining to keep distortion out of the finished dimensions. We can supply either condition: solution treated only, or solution treated and fully aged with mechanical test results at the aged hardness. State which you need on the purchase order, because it changes the test certificate.

Forging practice for UNS N19909

UNS N19909 is hot worked between 870 °C and 1120 °C (1600–2050 °F) in a three-stage sequence, and must be air cooled rather than quenched. The sequence matters: a warm-work and reheat step in the middle refines the grain, lowers the recrystallisation temperature and lifts the properties of the finished part.

Source: hot forming recommendations published by Special Metals for INCOLOY alloy 909, as practised by Jiangyin Jiangnan Metal Co., Ltd. Cool in air. Never water quench a hot-formed Alloy 909 part.

UNS N19909 forgings we produce

Jiangyin Jiangnan Metal Co., Ltd. forges UNS N19909 to the customer's drawing as open-die work and seamless ring rolling. There is no fixed catalogue, no die cost and no minimum piece quantity. The forms below are the ones most often ordered in this grade.

Capability for this grade specifically. Nickel-cobalt low-expansion alloys are melted in limited ingot sizes, so very large single pieces should be checked with us before you design around them. Machining allowance is normally 6–20 mm per surface depending on section; we also supply finish-machined parts to print.

How we make a UNS N19909 forging

1. Melt stock. Alloy 909 is supplied as VIM + VAR material as standard, since the grade is normally specified for aerospace and turbine hardware. VIM + ESR + VAR triple melt is available where the specification demands it. Melt route is stated on the certificate.
2. Billet verification. Heat chemistry is checked by spectrometer against the ordered AMS limits before any metal is heated, with particular attention to the 0.25–0.50% silicon window that defines Alloy 909.
3. Open-die forging or ring rolling. Forged on hydraulic presses and hammers with a controlled reduction ratio, following the three-stage temperature sequence above. Rings are rolled seamless with no weld.
4. Solution treatment. 980 °C, air cool. Parts intended for machining before ageing are shipped in this condition.
5. Rough or finish machining. Turned, bored, drilled and faced with an agreed allowance, or finish machined to print.
6. Double ageing. 720 °C / 8 h, controlled furnace cool at 55 °C/h to 620 °C / 8 h, air cool, with a recorded furnace chart supplied on request.
7. Testing and NDT. Tensile, hardness, grain size, ultrasonic examination and penetrant inspection to the class you nominate.
8. Certification and despatch. EN 10204 3.1 mill test certificate as standard; 3.2 witnessed by TÜV, BV, LR, SGS or DNV on request. Hard stamped, preserved and packed for sea or air freight.

Machining, welding and fabrication

Machine UNS N19909 with the practices used for high-strength nickel alloys: rigid setups, positive rake, heavy-duty tooling, steady feed and no dwelling. The alloy work hardens during cutting and has a gumminess that steels do not, so a tool that rubs instead of cutting will harden the surface ahead of the edge. Rough machining is done in the solution-treated condition wherever the design allows.

Starting values for the solution-treated condition. Reduce speed for the fully aged condition and for interrupted cuts. Carbide suits continuous turning; high-speed steel suits interrupted cuts and close-tolerance finishing. Tools should carry a positive rake angle.

• Drilling. Keep the feed steady so the drill never dwells and work hardens the hole bottom. Use short stub drills with a heavy web in a rigid setup. Feeds run from about 0.018 mm/rev for holes under 1.6 mm, to 0.08 mm/rev at 6 mm, to 0.25 mm/rev at 22 mm diameter.
• Milling. Rigid machines, rigid fixtures, sharp cutters. M2 or M10 high-speed steel cutters at 9–12 m/min (30–40 sfm) with 0.10–0.15 mm per tooth.
• Grinding. Grind wet. Aluminium oxide wheels or belts are preferred.
• Coolant. Water-based coolant for high-speed operations such as turning, grinding and milling; heavy lubricant for drilling, tapping, broaching and boring.
• Welding. Readily welded by the gas-tungsten-arc process using the procedures normal for nickel alloys; behaviour is close to Inconel 718. Confirm filler metal and post-weld heat treatment with the design authority, because a weld in the hot gas path is also an oxidation site in an alloy with no chromium.

Specifications, designations and equivalents

UNS N19909 is covered by SAE aerospace material specifications AMS 5884, AMS 5892 and AMS 5893, and is the same material sold under the trade name Incoloy® 909. Product-form coverage differs between sources, so order to the specification number and revision printed on your drawing.

Special Metals bulletin SMC-077 assigns AMS 5884 to billets, AMS 5892 to bars and forgings and AMS 5893 to sheet and strip. Several stockists publish the assignment differently. We do not treat the two as interchangeable: tell us the AMS number and revision on your drawing and we certify to that document. There is no DIN, EN, JIS or GB equivalent for this grade, so order by UNS number.

How UNS N19909 compares with neighbouring grades

Nominal chemistry and mean CTE values compiled by Jiangyin Jiangnan Metal Co., Ltd. for screening. CTE values are means from 20 °C to the alloy's normal working range. We forge every grade in this table.

Where UNS N19909 forgings are used

UNS N19909 is used wherever a component must not change size as it heats: gas-turbine seal rings, shrouds, casings, vanes and shafts, rocket-engine thrust chamber hardware, high-temperature bolting and gauge blocks.

Application list compiled from the published uses of the alloy and from parts forged by Jiangyin Jiangnan Metal Co., Ltd. Every part is made to the customer's drawing and specification.

Testing, inspection and certification

Every UNS N19909 forging leaves our works with an EN 10204 3.1 mill test certificate showing heat number, melt route, chemical analysis, heat-treatment record, mechanical results and NDT results. EN 10204 3.2 certification witnessed by a third party is available on request at the time of order.

• Chemical analysis. Spectrometric ladle analysis on every heat; product analysis on the finished forging on request.
• Mechanical testing. Room-temperature tensile, yield, elongation, reduction of area and hardness. Elevated-temperature tensile, stress rupture and notched-bar testing to your specification.
• Thermal expansion testing. Dilatometer measurement of the coefficient of expansion over your stated temperature range, where the drawing calls for it. The property that justifies the grade is the one worth verifying.
• Grain size. Determined to ASTM E112.
• Ultrasonic examination. ASTM A388, EN 10228-3, SEP 1921 class C/D/E or your nominated aerospace class.
• Surface NDT. Liquid penetrant to ASTM E165 or ASME V Article 6; magnetic particle is not applicable above the Curie point but can be applied at room temperature where specified.
• Dimensional inspection. Full dimensional report against the drawing, with CMM where required.
• Traceability. Hard stamping with heat number and part number, retained test material, and a certificate that names the melt source.

Frequently asked questions about UNS N19909

Request a quotation for UNS N19909 forgings

Send a drawing, a sketch, or simply the dimensions and quantity. We quote open-die forgings and seamless rolled rings in UNS N19909 with no tooling charge and no piece minimum. Useful details, if you have them: the AMS specification and revision, product form, dimensions with machining allowance, quantity, delivery condition (solution treated or aged), melt route, NDT class, certificate type and the date you need it.

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UNS N19909 by product form

• Forged and rolled rings
• Seamless rolled rings
• Forged discs and disks
• Forged disc capability
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