UNS R30155 forgings: Multimet N-155 rings, discs, shafts and bars

Q: What is the maximum service temperature of UNS R30155?

Approximately 816 C (1500 F) under high stress, and up to approximately 1093 C (2000 F) under moderate stress. Oxidation resistance is acceptable to approximately 980 C (1800 F). Above that temperature, Haynes 556 (UNS R30556) is the normal substitute, offering comparable creep-rupture strength with better oxidation resistance.

Q: How is UNS R30155 heat treated?

Solution heat treatment at 1177 C (2150 F) followed by a water quench for bar, plate and forgings, or a rapid air cool for thin sheet. Ageing is optional: four hours at 816 C (1500 F) followed by air cooling raises Brinell hardness to approximately 192-241 HB. Aged bar is difficult to straighten, so ageing is normally carried out after final fabrication.

Technical datasheet prepared by the metallurgy team at Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory in Jiangyin, Jiangsu, China. Last reviewed 31 August 2026.

Summary

UNS R30155, supplied under the trade name Multimet N-155, is a solid-solution-strengthened iron–nickel–cobalt–chromium superalloy containing nominally 21% Cr, 20% Ni, 20% Co, 3% Mo, 2.5% W and 0.15% N, with approximately 30% iron as the balance. It retains useful strength under high stress to approximately 816 °C (1500 °F) and under moderate stress to approximately 1093 °C (2000 °F). Strength is not developed by age hardening.

Jiangyin Jiangnan Metal Co., Ltd. forges UNS R30155 to drawing as rings, seamless rolled rings, discs, shafts, flanges, sleeves, bushings, tube sheets and bars, in weights from 10 kg to 15,000 kg and diameters from 100 mm to 6,000 mm, certified to EN 10204 3.1 or 3.2. Quotations: sales@steelforgepieces.com or +86-189-2135-9659.

Material identification summary for UNS R30155
UNS number	R30155
Common names	Multimet N-155, alloy N-155, AISI 661, SAE 661
Werkstoff number	1.4974
Weld filler UNS	W73155
Alloy family	Fe–Ni–Co–Cr solid-solution superalloy
Forging specifications	AMS 5768, ASTM B639
Bar and ring spec	AMS 5769
Density	8.20 g/cm³ (0.296 lb/in³)
Melting range	1288–1354 °C (2350–2470 °F)
Solution treatment	1177 °C (2150 °F), water quench
Service ceiling	816 °C high stress; 1093 °C moderate stress

What UNS R30155 is

Production of UNS R30155 dates from the late 1940s. The alloy provides useful strength at high temperature at lower cost than a precipitation-hardened nickel alloy, and requires no ageing treatment.

Three mechanisms provide the strength: a heavily alloyed austenitic matrix, carbides formed by molybdenum, tungsten and niobium, and dissolved nitrogen held between 0.10% and 0.20%. None of them depend on ageing. Forgings leave the solution heat treatment furnace with properties fully developed and do not lose them to over-ageing in service.

Iron is the largest single element in R30155 at approximately 30%, followed by chromium at 21%, then nickel and cobalt at approximately 20% each. The alloy is therefore iron-base rather than nickel-base. The R prefix in the UNS number groups it with the reactive and refractory metals rather than the N-series nickel alloys. Most suppliers list it with the nickel grades because it competes with them in the same applications.

Oxidation limit. Oxidation resistance is acceptable to approximately 980 °C (1800 °F) and declines rapidly above that temperature. In 1008-hour flowing-air tests at 1095 °C, R30155 lost approximately 226 µm of metal compared with approximately 38 µm for Haynes 556. For continuous service above 980 °C, alloy 556 (UNS R30556) is the normal substitute.

Chemical composition

UNS R30155 chemical composition limits, weight percent, per AMS 5768 / AMS 5769 / AMS 5532
Element	Symbol	Min %	Max %	Nominal %
Carbon	C	0.08	0.16	0.12
Manganese	Mn	1.00	2.00	1.50
Silicon	Si	—	1.00	≤1.00
Phosphorus	P	—	0.040	—
Sulfur	S	—	0.030	—
Chromium	Cr	20.00	22.50	21.0
Nickel	Ni	19.00	21.00	20.0
Cobalt	Co	18.50	21.00	20.0
Molybdenum	Mo	2.50	3.50	3.0
Tungsten	W	2.00	3.00	2.5
Niobium + tantalum	Nb+Ta	0.75	1.25	1.0
Nitrogen	N	0.10	0.20	0.15
Iron	Fe	Balance		≈30

Niobium is written as columbium (Cb) in older specifications. Nb+Ta and Cb+Ta denote the same limit. Iron is determined arithmetically by difference. Nitrogen is a deliberate strengthening addition rather than a residual, and heats below 0.10% N will not develop the specified high-temperature strength.

Mechanical properties

Room-temperature properties, solution heat treated

Typical room-temperature tensile properties of UNS R30155 by product form
Form and condition	Tensile strength	0.2% yield strength	Elongation
Forged bar, 25–50 mm, 1185 °C water quench	765 MPa (111.0 ksi)	384 MPa (56 ksi)	55%
Forging, dia. 533 × 83 mm, stress relieved 2 h at 649 °C	811 MPa (117.6 ksi)	493 MPa (72 ksi)	30%
Hot-rolled bar, 13–50 mm, 1185 °C water quench	767 MPa (111.3 ksi)	372 MPa (54 ksi)	57%
Sheet, 1.6 mm, 1177 °C rapid air cool	814 MPa (118.1 ksi)	400 MPa (58 ksi)	49%
Plate, 13 mm, water quench, tested at −78 °C	949 MPa (137.7 ksi)	513 MPa (74 ksi)	63%
Acceptance minimum commonly specified for forgings	550 MPa (80 ksi) min	310 MPa (45 ksi) min	18% min

The final row is the acceptance minimum commonly written into forging purchase orders. It is not a typical value; production forgings normally test above it. Confirm the acceptance minimum against the current revision of AMS 5768 or the customer specification named on the order.

Elevated-temperature tensile properties

Short-time tensile properties of UNS R30155 sheet, solution heat treated at 1177 °C
Temperature	Tensile strength	Yield strength	Elongation
Room temperature	814 MPa	400 MPa	49%
427 °C (800 °F)	676 MPa	292 MPa	54%
538 °C (1000 °F)	647 MPa	274 MPa	54%
649 °C (1200 °F)	507 MPa	259 MPa	28%
760 °C (1400 °F)	403 MPa	247 MPa	12%
871 °C (1600 °F)	268 MPa	207 MPa	15%
982 °C (1800 °F)	170 MPa	117 MPa	51%
1093 °C (2000 °F)	90 MPa	58 MPa	38%
1204 °C (2200 °F)	33 MPa	21 MPa	29%

Elongation falls to 12–15% between approximately 760 °C and 871 °C before recovering at higher temperatures. This affects hot forming and thermal-cycling service through that range.

Impact toughness and hardness

Charpy impact energy and hardness, solution annealed condition
Property	Condition	Value
Charpy impact	816 °C (1500 °F)	94 J (69 ft-lb)
Charpy impact	Room temperature	153 J (113 ft-lb)
Charpy impact	−196 °C (−321 °F)	76 J (56 ft-lb)
Hardness, bar	Solution annealed	89 HRBW (≈190 HB)
Hardness, bar	Aged 4 h at 816 °C, air cool	192–241 HB

Impact energy remains high down to cryogenic temperatures.

Creep and stress-rupture strength

For components under sustained load at temperature, rupture strength governs the design rather than tensile strength. The chart gives the initial stress producing rupture in 1,000 hours.

Approximate initial stress to produce rupture in 1,000 hours, solution-annealed sheet. Load-carrying capability falls by a factor of approximately fifteen between 649 °C and 982 °C, so a design margin established at one temperature does not transfer to another.

Approximate initial stress to produce 1% creep or rupture, solution-annealed UNS R30155
Temperature	1% creep in 1,000 h	Rupture in 100 h	Rupture in 1,000 h
649 °C (1200 °F)	200 MPa	331 MPa	276 MPa
704 °C (1300 °F)	145 MPa	259 MPa	200 MPa
760 °C (1400 °F)	97 MPa	179 MPa	131 MPa
816 °C (1500 °F)	66 MPa	128 MPa	90 MPa
871 °C (1600 °F)	41 MPa	83 MPa	52 MPa
927 °C (1700 °F)	23 MPa	54 MPa	32 MPa
982 °C (1800 °F)	11 MPa	32 MPa	18 MPa

Published values indicate test results and are not guaranteed minima. Use them for material screening and design against the data set named in the governing code.

Physical properties

Physical properties of UNS R30155 (Multimet N-155)
Property	Condition	Metric	Imperial
Density	Room temperature	8.20 g/cm³	0.296 lb/in³
Melting range	—	1288–1354 °C	2350–2470 °F
Thermal conductivity	200 °C	14.6 W/m·°C	101 Btu·in/ft²·h·°F
Thermal conductivity	600 °C	20.0 W/m·°C	143 Btu·in/ft²·h·°F
Mean thermal expansion	20–100 °C	14.1 µm/m·°C	8.2 µin/in·°F
Mean thermal expansion	20–600 °C	16.7 µm/m·°C	9.1 µin/in·°F
Mean thermal expansion	20–1000 °C	18.1 µm/m·°C	10.1 µin/in·°F
Electrical resistivity	200 °C	101.7 µΩ·cm	40.1 µΩ·in
Electrical resistivity	1000 °C	122.7 µΩ·cm	48.2 µΩ·in
Specific heat	22–100 °C	435 J/kg·°C	0.104 Btu/lb·°F
Poisson's ratio	Room temperature	0.298
Poisson's ratio	816 °C	0.339
Emissivity, oxidised	1090 °C	0.88

Solid UNS R30155 round bar weighs approximately 6.44 kg per metre for each 1,000 mm² of cross-section. A 200 mm diameter bar is approximately 202 kg/m.

Equivalents, specifications and cross-references

UNS R30155 designations and governing specifications by product form
Designation or spec	System	Covers
R30155	UNS	Wrought alloy
W73155	UNS	Weld filler metal
1.4974	Werkstoff / DIN	European equivalent designation
Multimet N-155	Trade name	Haynes International
AISI 661 / SAE 661	Legacy grade number	Wrought alloy
AMS 5768	SAE Aerospace	Bars, forgings and rings, solution heat treated
AMS 5769	SAE Aerospace	Billet, rod and bar
AMS 5532	SAE Aerospace	Sheet, strip and plate
AMS 5794	SAE Aerospace	Bare welding rod and wire
AMS 5795	SAE Aerospace	Coated electrodes, AWS A5.4 class E3155
ASTM B639	ASTM	Precipitation-hardening and cold-worked bar and forgings

Cross-reference designations are near-equivalents given for procurement convenience and are not automatically interchangeable. Order against the specification and revision named on the drawing.

Forging and heat treatment practice

R30155 forges by conventional methods. The working temperature range is narrow, and forging outside it reduces high-temperature strength in a way that later heat treatment cannot correct.

Melt and refine

EAF + VOD + ESR is the standard route. VIM + ESR + VAR is used where the customer specification requires double- or triple-melted material. Nitrogen must be controlled within 0.10–0.20%.
Soak the ingot at 1204 °C

Soak thoroughly at approximately 1204 °C (2200 °F). Higher temperatures cause surface rupture and heavy oxidation. A fully soaked ingot accepts a fast forging rate and does not require light hammer blows to break down the cast structure.
Forge above 927 °C

Finish temperature must not fall below 927 °C (1700 °F). Lower finishing temperatures reduce high-temperature strength, particularly for parts operating above 704 °C. Reheat and re-soak between passes.
Ring roll where the part is a ring

Upset, punch, then expand the pierced blank on a ring rolling mill. Ring rolling produces circumferential grain flow that machining from solid cannot, which is why rolled rings are specified for rotating and pressure-containing duty.
Solution heat treat at 1177 °C

Hold at 1177 °C (2150 °F) for a time determined by section thickness, then water quench. Thin sections may be rapid air cooled. This is the standard supply condition.
Stress relieve heavy or intricate shapes

Two to four hours at the maximum intended service temperature. Without stress relief, heavy or intricate forgings distort during machining. The treatment also produces a mild precipitation-hardening effect.
Machine to drawing

Rough or finish machining in-house. The alloy work-hardens significantly. Machining requires rigid setups, positive rake, sharp tooling and a constant heavy feed that keeps the cutting edge below the work-hardened layer.
Test, inspect and certify

Ultrasonic examination to ASTM A388, EN 10228-3 or SEP 1921, mechanical testing, then an EN 10204 3.1 certificate or a 3.2 certificate countersigned by a third-party body.

Welding. GTAW, GMAW, SMAW and resistance welding are all applicable. Submerged arc welding is not recommended because high heat input and slow cooling promote cracking. Preheat is not required, interpass temperature should remain below 93 °C (200 °F), and post-weld heat treatment is not generally required. R30155 has a known tendency toward heat-affected-zone cracking, so joint design and restraint require attention in thick sections.

UNS R30155 forgings we supply

All items are made to drawing. No stock sizes are held. Send dimensions or a drawing for pricing.

Open-die forging capability at Jiangyin Jiangnan Metal
Parameter	Range
Piece weight	10 kg to 15,000 kg
Diameter	100 mm to 6,000 mm
Length	100 mm to 12,000 mm
Hydraulic press	4,500 tonnes
Forging hammers	1 t, 3 t, 6 t and 9 t
Ring rolling mills	3 m and 6 m
Melting routes	EAF+VOD+ESR; ESR+VAR; VIM+ESR+VAR
Machining	Rough or finish machined to drawing
Certification	EN 10204 3.1 or 3.2

Where UNS R30155 forgings are used

Aero engines and airframes

Tailpipes, tail cones, exhaust manifolds, afterburner components, combustion chambers, turbine blades and buckets, and nozzles. High-temperature bolting is a long-established application where hot strength is required at lower cost than a nickel superalloy.

Industrial furnaces and heat treatment

Structural parts, fixtures, baskets, jigs and retorts. The alloy requires no ageing cycle and tolerates repeated thermal cycling without loss of strength.

Power generation and turbomachinery

Forged rings, discs, shafts, spindles and gear blanks for turbines, generators, gas compressors and gear boxes operating below the oxidation limit.

Oil, gas and process plant

Forged valve bodies, bonnets, stems and seat rings for ball, gate, globe, check and plug valves. Flanges, tube sheets and nozzles for columns, towers, reactors, preheaters and heat exchangers. Shafts for chemical and plunger pumps. Wellhead and Christmas tree components under combined thermal and mechanical load.

UNS R30155 compared with alternative alloys

UNS R30155 compared with alloys specified for similar duty
Alloy	Base	Strengthening	Practical ceiling	Selected when
UNS R30155Multimet N-155	Fe–Ni–Co	Solid solution + N + carbides	≈980 °C oxidation	Hot strength required at lowest cost, with no ageing cycle
UNS R30556Haynes 556	Fe–Ni–Co	Solid solution + rare earth	>1095 °C oxidation	Creep strength comparable to R30155 but service above 980 °C
UNS N06002Hastelloy X	Ni	Solid solution	≈1200 °C oxidation	Combustor and ducting work requiring better oxidation and formability
UNS N06625Inconel 625	Ni	Solid solution Nb–Mo	≈980 °C	Aqueous and chloride corrosion resistance governs selection
UNS N07718Inconel 718	Ni–Fe	Gamma double-prime age hardening	≈650 °C	High strength required below 650 °C and ageing is acceptable
UNS R30605Haynes 25 / L-605	Co	Solid solution + carbides	≈1100 °C	Wear resistance with hot strength, or sulphidation resistance

Ceilings are practical oxidation limits for continuous service, not absolute maxima. Selection for a specific component depends on stress, atmosphere, thermal cycle and cost.

Testing, inspection and certification

Standard test and documentation package for UNS R30155 forgings
Item	Standard
Ultrasonic examination	ASTM A388, EN 10228-3, SEP 1921
Chemical analysis	Ladle and product analysis, spectrographic
Mechanical testing	Tensile, hardness, impact as ordered
Surface examination	Liquid penetrant on request
Dimensional report	Against customer drawing
Material certificate	EN 10204 3.1
Third-party certificate	EN 10204 3.2, countersigned by SGS, BV, TÜV or Lloyd's

Ultrasonic acceptance classes are set on the order. Quote the class called on the drawing in the enquiry so that achievability in the required section thickness can be confirmed before pricing.

How to order UNS R30155 forgings

A drawing produces the fastest firm price. Without a drawing, the following six items are sufficient to quote from:

Grade and specification. UNS R30155, plus the governing specification and revision: AMS 5768, ASTM B639, or a customer specification.
Shape and dimensions. Outside diameter, inside diameter, height or length, and wall, with tolerances. State whether the size is finished or rough.
Machining state. As-forged, rough machined with a stated allowance, or finish machined to print.
Heat treatment condition. Solution treated is standard. State any requirement for stress relief or ageing.
Testing and certification. Ultrasonic class and standard, mechanical tests required, EN 10204 3.1 or 3.2.
Quantity and destination port. Both affect price and lead time.

Send the enquiry

Email a drawing in PDF, DWG or STEP to sales@steelforgepieces.com, or send dimensions to +86-189-2135-9659. Enquiries are answered in English or Chinese.

Email the sales team

Frequently asked questions

What is UNS R30155?

UNS R30155 is a solid-solution-strengthened iron–nickel–cobalt–chromium superalloy, supplied under the trade name Multimet N-155 and also designated alloy N-155, AISI 661 or Werkstoff 1.4974. Nominal composition is 21% Cr, 20% Ni, 20% Co, 3% Mo, 2.5% W, 1% Nb+Ta and 0.15% N, with approximately 30% iron as the balance. Strength at temperature is not developed by age hardening, so the alloy is supplied and used in the solution heat treated condition.

Is UNS R30155 a nickel alloy or a cobalt alloy?

Neither. Iron is the largest single element at approximately 30%, followed by chromium at 21% and nickel and cobalt at approximately 20% each, which makes R30155 an iron-base superalloy. The UNS R prefix groups it with the reactive and refractory metals rather than the N-series nickel alloys. Most distributors list it with nickel and cobalt superalloys because it competes with them in the same applications.

What is the maximum service temperature of UNS R30155?

Approximately 816 °C (1500 °F) under high stress, and up to approximately 1093 °C (2000 °F) under moderate stress. Oxidation resistance is acceptable to approximately 980 °C (1800 °F). Above that temperature, Haynes 556 (UNS R30556) is the normal substitute, offering comparable creep-rupture strength with better oxidation resistance.

Which specifications cover UNS R30155 forgings?

AMS 5768 and ASTM B639 cover forgings. AMS 5769 covers billet, rod, bar and rings. AMS 5532 covers sheet, strip and plate. AMS 5794 covers bare welding wire and AMS 5795 covers coated electrodes, which carry the weld-filler designation W73155 and the AWS classification E3155.

How is UNS R30155 heat treated?

Solution heat treatment at 1177 °C (2150 °F) followed by a water quench for bar, plate and forgings, or a rapid air cool for thin sheet. Ageing is optional: four hours at 816 °C (1500 °F) followed by air cooling raises Brinell hardness to approximately 192–241 HB. Aged bar is difficult to straighten, so ageing is normally carried out after final fabrication.

What is the difference between UNS R30155 and Haynes 556?

Haynes 556 (UNS R30556) was developed to address three limitations of Multimet N-155: oxidation resistance above 1800 °F, a tendency toward heat-affected-zone cracking during welding, and a wide scatter band in mechanical properties. Creep-rupture strength is comparable. In 1008-hour flowing-air tests at 1095 °C, R30155 lost approximately 226 µm of metal compared with approximately 38 µm for alloy 556. R30155 remains the lower-cost option below approximately 980 °C.

Can UNS R30155 be welded?

Yes. GTAW, GMAW, SMAW and resistance welding are all applicable. Submerged arc welding is not recommended because high heat input and slow cooling promote cracking. Preheat is not required and interpass temperature should remain below 93 °C (200 °F). Post-weld heat treatment is not generally required. Filler is Multimet wire to AMS 5794 or coated electrodes to AMS 5795.

What size UNS R30155 forgings can Jiangyin Jiangnan Metal produce?

Jiangyin Jiangnan Metal Co., Ltd. produces open-die forgings and seamless rolled rings weighing from 10 kg to 15,000 kg, with diameters from 100 mm to 6,000 mm and lengths from 100 mm to 12,000 mm. Plant equipment includes a 4,500-tonne hydraulic press, 1 t, 3 t, 6 t and 9 t hammers, and 3 m and 6 m ring rolling mills. Contact sales@steelforgepieces.com or +86-189-2135-9659 with a drawing for a quotation.

What certification and testing is supplied with UNS R30155 forgings?

Material certificates are issued to EN 10204 3.1, or to EN 10204 3.2 countersigned by a third-party inspection body such as SGS, BV, TÜV or Lloyd's. Ultrasonic examination is performed to ASTM A388, EN 10228-3 or SEP 1921 to the acceptance class stated on the order.

Where is UNS R30155 used?

Aircraft tailpipes, tail cones, exhaust manifolds, afterburner parts, combustion chambers, turbine blades and buckets, and nozzles. It is also used for high-temperature bolting and as a structural material for heat-treating furnace fixtures, baskets and jigs. In process industries it is used for forged valve components, flanges, tube sheets and shafts operating at temperature.

About the supplier

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. It manufactures forged rings, seamless rolled rings, discs, shafts, flanges, bars, sleeves, bushings, tube sheets, nozzles and valve components in carbon steel, alloy steel, tool steel, stainless steel, nickel alloys and cobalt-bearing superalloys, including UNS R30155 (Multimet N-155).

Production covers piece weights from 10 kg to 15,000 kg, diameters from 100 mm to 6,000 mm and lengths from 100 mm to 12,000 mm, using a 4,500-tonne hydraulic press, 1 t, 3 t, 6 t and 9 t forging hammers, and 3 m and 6 m seamless ring rolling mills. Material is melted by EAF+VOD+ESR, ESR+VAR or VIM+ESR+VAR according to specification. Forgings are supplied as-forged, rough machined or finish machined to drawing, ultrasonically examined to ASTM A388, EN 10228-3 or SEP 1921, and certified to EN 10204 3.1 or 3.2.

Company Jiangyin Jiangnan Metal Co., Ltd.
Address
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Phone +86-189-2135-9659
Email sales@steelforgepieces.com
Website www.steelforgepieces.com
Languages English, Chinese

Related grades we forge

References

Haynes International, MULTIMET alloy: principal features, composition, tensile, creep-rupture, oxidation and physical property data. haynesintl.com
SAE International, AMS 5768: Alloy bars, forgings and rings, 21Cr–20Ni–20Co–3.0Mo–2.5W–1.0Cb, solution heat treated.
SAE International, AMS 5769: Alloy billet, rod and bar, same nominal composition.
SAE International, AMS 5532: Alloy sheet, strip and plate.
ASTM International, ASTM B639: Precipitation-hardening and cold-worked nickel alloy bars, forgings and forging stock.
ASTM International, ASTM A388; CEN, EN 10228-3; VDEh, SEP 1921: ultrasonic examination of forgings.

Data disclaimer. Property values on this page are typical published results, not guaranteed minima, and are given for material screening only. Design against the specification and data set named in the governing code, and confirm acceptance values against the current revision of the applicable AMS or ASTM standard.