Cobalt-nickel multiphase alloy · Open-die forgings

MP35N Forgings: UNS R30035 / ASTM F562 / AMS 5758, 5844, 5845

Jiangyin Jiangnan Metal Co., Ltd. manufactures MP35N, the Co-35Ni-20Cr-10Mo multiphase alloy specified as UNS R30035, ASTM F562, AMS 5758, AMS 5844 and AMS 5845 and listed for sour service in NACE MR0175 / ISO 15156-3. We supply it as open-die forgings, seamless rolled rings, forged bars, discs, flanges, shafts, sleeves, bushings and tube sheets, to customer drawing, with EN 10204 3.1 or 3.2 certification.

GenericUNS R30035 · ASTM F562

AerospaceAMS 5758 / 5844 / 5845

ImplantISO 5832-6 · BS 7252-6

Sour serviceNACE MR0175 · MR0103

Published 8 March 2016 · Last updated 15 August 2026 · Technically reviewed by the Jiangyin Jiangnan Metal Co., Ltd. Metallurgical Engineering Team · Jiangyin, Jiangsu, China

MP35N at a glance

MP35N is a non-magnetic cobalt-nickel-chromium-molybdenum multiphase alloy of nominal composition 35 % cobalt, 35 % nickel, 20 % chromium and 10 % molybdenum. It reaches 2 068 MPa (300 ksi) tensile strength while staying ductile, and it resists chloride stress-corrosion cracking and hydrogen embrittlement at hardness levels that crack conventional high-strength steels. That strength does not come from the chemistry on its own. It is produced by cold work followed by ageing, which is what separates the three AMS specifications. An order that does not name the condition cannot be quoted or certified.

Generic designations: UNS R30035 · ASTM F562 · ATI 35N
Nominal chemistry: Co 35 % · Ni 35 % · Cr 20 % · Mo 10 %
Tensile range: 930 to 2 068 MPa (135 to 300 ksi) by condition
Hardness range: 8 to 60 HRC by condition
Density: 8.43 g/cm³ (0.305 lb/in³)
Melting range: 1 315 to 1 440 °C (2 400 to 2 625 °F)
Magnetic response: Non-magnetic, µ below 1.01 in all conditions
Service temperature: Cryogenic to about 454 °C (850 °F)
Melting route: VIM + VAR for AMS and F562 work; EAF + VOD + ESR for industrial
Certification: EN 10204 3.1 standard, 3.2 on request
Manufacturer: Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China

R30035UNS

F562ASTM

5844/45AMS

2 068Max UTS MPa

300Max UTS ksi

8.43Density g/cm³

60 HRCMax hardness

454 °CMax service

Trademark notice. MP35N® is a registered trademark of SPS Technologies, Inc. ATI 35N® is a registered trademark of ATI Inc., and CarTech® of Carpenter Technology Corporation. Material produced and sold by those companies under those brands is theirs. Material manufactured by Jiangyin Jiangnan Metal Co., Ltd. is correctly described as UNS R30035 / ASTM F562, the same generic chemistry produced independently. We are not affiliated with, sponsored by or endorsed by any of the trademark holders named above. Use UNS R30035 on drawings and purchase orders. It is unambiguous and it is not a trademark.

What is MP35N?

MP35N is a multiphase alloy. In the solution-annealed condition the structure is face-centred cubic (FCC), soft and very ductile. Cold work by drawing, rolling, swaging or extrusion drives a partial transformation to a hexagonal close-packed (HCP) structure. The fine platelets this produces obstruct dislocation movement. Ageing afterwards precipitates Co₃Mo and locks the structure in place. Together these two steps take the alloy far beyond what precipitation hardening alone can reach.

The alloy was developed for high-strength aerospace fasteners. It was then adopted wherever the same combination was needed: extreme strength, no magnetic signature, and corrosion resistance in environments that destroy conventional high-strength steels. Cobalt and nickel each sit near 35 %, chromium provides the passive film, and molybdenum contributes both solid-solution strength and the ageing precipitate.

Strength is not a fixed property of MP35N. The same UNS R30035 forging can be 930 MPa or 2 068 MPa depending on how much cold work and ageing it has received. This has two practical effects. The AMS condition has to appear on every enquiry and purchase order. And heavy sections are harder to strengthen than thin ones, because the cold work has to reach the centre of the part.

Equivalent designations and specifications

With MP35N the trade name is far better known than the generic designation, which causes confusion on drawings. The table below maps every designation you are likely to meet.

Table 1. MP35N designations, specifications and equivalents
System	Designation	Covers
UNS	R30035	The generic, non-trademarked designation. Use this on drawings.
ASTM	F562	Wrought 35Co-35Ni-20Cr-10Mo alloy for surgical implant applications
SAE AMS	5758	Bar, VIM-VAR, solution heat treated
SAE AMS	5844	Bar, VIM-VAR, solution heat treated and work strengthened
SAE AMS	5845	Bar, VIM-VAR, solution heat treated, work strengthened and aged
ISO	5832-6	Implants for surgery, wrought cobalt-nickel-chromium-molybdenum alloy
BS	7252-6	British equivalent of ISO 5832-6
NACE / ISO	MR0175 / 15156-3	Listed for H₂S service, conditional on the environment
NACE	MR0103	Listed for refinery sour service
Trade names	MP35N® · ATI 35N® · CarTech® MP35N	Proprietary names for the same chemistry, owned by their respective holders
MP35N® is a registered trademark of SPS Technologies, Inc. Jiangyin Jiangnan Metal supplies material to the UNS R30035 chemistry and to the ASTM and AMS specifications listed above.

What is the chemical composition of MP35N?

Composition limits are common to ASTM F562, AMS 5758, AMS 5844 and AMS 5845. Those specifications differ in condition, not in chemistry. All values are weight percent.

Table 2. MP35N / UNS R30035 chemical composition limits, wt %
Element	Symbol	Min	Max	Function in the alloy
Cobalt	Co	Balance (nom. 35)		Base element. Drives the FCC to HCP transformation that produces the strength
Nickel	Ni	33.00	37.00	Stabilises the FCC phase. Supplies toughness and ductility
Chromium	Cr	19.00	21.00	Forms the passive film. General, pitting and crevice corrosion resistance
Molybdenum	Mo	9.00	10.50	Solid-solution strengthening, Co₃Mo on ageing, crevice resistance in chlorides
Titanium	Ti	n/a	1.00	Residual. Contributes minor precipitation strengthening
Iron	Fe	n/a	1.00	Residual, controlled
Manganese	Mn	n/a	0.15	Residual, controlled
Silicon	Si	n/a	0.15	Residual, controlled
Carbon	C	n/a	0.025	Held very low. Carbides would cut ductility and fatigue life
Boron	B	n/a	0.015	Grain-boundary control
Phosphorus	P	n/a	0.015	Impurity limit
Sulfur	S	n/a	0.010	Impurity limit. Critical for hot workability during forging
Limits per ASTM F562 and AMS 5758 / 5844 / 5845. Certified ladle and product analysis for the delivered heat appears on the EN 10204 material test certificate.

Because cobalt and nickel contents are so close, MP35N is catalogued inconsistently across the industry. Cobalt is the balance element, so it is strictly a cobalt-base alloy, yet many distributors list it under nickel alloys or simply as a superalloy. The label makes no practical difference. The UNS R30035 designation removes the ambiguity.

The condition system: one alloy, three strengths

Tensile strength rises with cold reduction, and ageing adds a further increment on top of that. The chart below shows the shape of the relationship, with the three AMS specifications marked at their anchor points.

Solution treated + work strengthened Solution treated + work strengthened + aged Solution treated only

Schematic. The three labelled anchor points are the specification values for AMS 5758, AMS 5844 and AMS 5845. The curve shape between them is indicative of the published behaviour of the alloy family and is drawn for engineering intuition, not for design calculation. Certified values for a delivered heat appear on that heat's material test certificate.

Section size matters. Cold work has to reach the centre of the section to strengthen it. Thin bar and wire reach the top of the curve easily. Heavy forged sections do not. For large rings, discs and shafts, state the required properties and the section thickness at which they must be met, and expect the achievable strength to fall below thin-section values. This is the most common cause of a rejected MP35N forging.

Tool 1 of 7

MP35N condition and property selector

Pick an AMS condition, or a target strength, and see the full property set, the processing route behind it, and what it means for machining and section size.

Select by

Target tensile strength

Target unit

Section thickness (mm, optional)

Typical published values for the UNS R30035 chemistry, given for engineering screening. Heavy sections may not reach thin-section properties because cold work does not penetrate uniformly. The section-size note in the output is a warning to verify, not a calculated derating. Order to the AMS specification for guaranteed minima.

Tool 2 of 7

Strength and hardness converter

Convert between MPa, ksi and the hardness scales, and see which MP35N condition the value corresponds to. Useful when a drawing calls out hardness but the specification calls out strength.

Value

Unit / scale

Hardness-to-hardness conversions follow the general shape of ASTM E140, which is established for steels and approximate for cobalt-base alloys. Hardness-to-tensile correlation is looser still and is shown only to locate the value on the MP35N condition curve. Never use a converted value where the specification requires a measured one. Test on the scale the drawing calls out.

What are the mechanical properties of MP35N?

These three rows are why the condition has to be specified. Values are typical for forged and bar product at room temperature. The governing specification carries the guaranteed minima for your order.

Table 3. MP35N typical room-temperature mechanical properties by condition
Condition	Spec	Tensile MPa (ksi)	0.2 % yield MPa (ksi)	Elong. %	R of A %	Hardness
Solution heat treated	AMS 5758	930 (135)	415 (60)	50	65	8 to 20 HRC
Solution treated + work strengthened	AMS 5844	1 760 (255)	1 550 (225)	12	50	45 HRC
Solution treated + work strengthened + aged	AMS 5845	1 790 to 2 068 (260 to 300)	1 725 to 1 965 (250 to 285)	8 to 10	35 to 45	55 to 60 HRC
Between the softest and hardest condition, tensile strength changes by a factor of 2.2 and elongation falls from 50 % to under 10 %. Fatigue strength and stress-corrosion behaviour move with them.

MP35N has no ductile-to-brittle transition, so it keeps its toughness at cryogenic temperature. That is one reason it appears in liquefied-gas and space hardware. Fatigue strength is exceptionally high for an alloy at this strength level, and that property is what makes it a fastener material rather than simply a strong one.

Physical properties

Table 4. MP35N / UNS R30035 typical physical properties
Property	Metric	Imperial
Density	8.43 g/cm³	0.305 lb/in³
Melting range	1 315 to 1 440 °C	2 400 to 2 625 °F
Modulus of elasticity	233 GPa	33.8 × 10⁶ psi
Coefficient of thermal expansion, 20 to 200 °C	12.8 × 10⁻⁶ /K	7.1 × 10⁻⁶ /°F
Magnetic permeability	below 1.01	Non-magnetic, all conditions
Maximum service temperature	about 454 °C	about 850 °F
Low-temperature limit	Cryogenic	No ductile-to-brittle transition
Aerospace fastener practice commonly limits MP35N to about 316 °C (600 °F) even though the alloy keeps useful properties higher. Confirm the temperature limit against your own design code.

Density matters when you are substituting. MP35N at 8.43 g/cm³ is about 3 % heavier than Inconel 718 at 8.19 g/cm³, a modest weight penalty for roughly 50 % more tensile strength. Against 17-4PH at 7.78 g/cm³ the penalty is 8 %, but 17-4PH is magnetic and far more limited in sour service.

Heat treatment, cold work and ageing

Solution heat treatment

Bar and forgings are solution treated at 1 038 to 1 052 °C (1 900 to 1 925 °F) for 4 to 8 hours, then air cooled. This dissolves the precipitates, restores a fully face-centred-cubic structure and returns the material to its softest, most ductile state ready for cold working or forming.

Cold work (work strengthening)

Strength is developed by cold reduction through drawing, rolling, swaging or extrusion. The reduction drives the partial FCC to HCP transformation described above. AMS 5844 material is supplied in this condition. The practical limit is section size, because cold work must reach the centre of the part. Thin sections strengthen far more readily than heavy forged sections.

Ageing

Ageing at 538 to 649 °C (1 000 to 1 200 °F) for 4 to 4.5 hours, then air cooled, precipitates Co₃Mo and adds roughly 170 to 210 MPa on top of the work-strengthened value. AMS 5845 material is supplied in this condition. Ageing without prior cold work produces very little strengthening. The two steps work together, not independently.

Table 5. MP35N processing parameters
Operation	Temperature	Time	Cooling
Hot working / forging	1 065 to 1 175 °C (1 950 to 2 150 °F)	Frequent reheats	Air
Solution heat treatment	1 038 to 1 052 °C (1 900 to 1 925 °F)	4 to 8 h	Air cool
Cold work	Ambient	To required reduction	n/a
Ageing	538 to 649 °C (1 000 to 1 200 °F)	4 to 4.5 h	Air cool
Stress relief (annealed material)	Below 538 °C	By section	Air cool

Tool 3 of 7

Strengthening route planner

Enter the tensile strength or hardness your part must reach and get the processing route that produces it: solution treatment, approximate cold reduction, ageing schedule and the matching AMS specification to write on the order.

Required property value

Property

Product form

Governing section thickness (mm)

Indicative route planning for enquiry purposes. The cold reduction figure is estimated from the published strength-versus-reduction behaviour of the alloy family and assumes the reduction reaches the governing section. Real production routes are set against the delivered heat and qualified by test coupon. Use this to frame the enquiry, not to write a work instruction.

Corrosion resistance and sour service

MP35N combines chromium for passivity with molybdenum for chloride resistance, on a cobalt-nickel base that is inherently resistant to hydrogen embrittlement. The result is unusual. The alloy keeps its corrosion resistance at hardness levels where conventional high-strength steels crack. In seawater it is effectively immune to pitting and crevice attack even in the fully aged condition.

Table 6. MP35N corrosion behaviour by environment
Environment	Behaviour
Seawater, chlorides	Effectively immune to pitting, crevice corrosion and chloride stress-corrosion cracking, at full strength
H₂S sour service	Highly resistant to sulfide stress cracking. Listed in NACE MR0175 / ISO 15156-3 and NACE MR0103, conditional on the environment
Hydrogen	Strongly resistant to hydrogen embrittlement, a principal reason it replaces high-strength steel fasteners
Mineral acids	Resistant to most mineral acids including hydrochloric. Consult data for concentration and temperature
Sulfidation, oxidation	Good resistance to sulfidation and high-temperature oxidation within its service range
Body fluids	Biocompatible. Qualified as an implant alloy under ASTM F562 and ISO 5832-6

The NACE listing is conditional, not blanket. UNS R30035 appears in NACE MR0175 / ISO 15156-3, but acceptance depends on the specific combination of hardness, cold-work level, temperature, H₂S partial pressure, chloride content and the presence of elemental sulfur. The governing table in the standard sets the envelope. Do not treat "MP35N is NACE approved" as a qualification for your service. It is not, and the standard says so.

Tool 4 of 7

Sour-service parameter check

Assemble the environment data that ISO 15156-3 requires for a UNS R30035 selection, see which parameters fall outside common listing envelopes, and produce a checklist to confirm against the standard and to send with your enquiry.

H₂S partial pressure (kPa)

Maximum service temperature (°C)

Chloride concentration (mg/L)

Specified maximum hardness (HRC)

Elemental sulfur present

In-situ pH

This tool does not qualify a material for sour service and does not issue an approval. It organises the parameters ISO 15156-3 requires and flags values that commonly sit outside standard listing envelopes so they get checked. Only the current revision of NACE MR0175 / ISO 15156-3, read against your specific environment, or a documented qualification under Annex B, can qualify a material. Sour-service selection must be signed off by the responsible materials engineer on your project.

Forging practice

MP35N is among the more demanding alloys to open-die forge. It work-hardens faster than stainless steel or Inconel 718, so the hot-working window is narrow and reductions have to stay light and controlled. Pushing the reduction per blow produces surface tearing, not a shorter cycle.

We plan 30 to 40 % more forging operations and reheats for an MP35N part than for the same geometry in Inconel 718. This is worth knowing when you compare quotations. A supplier pricing MP35N on nickel-alloy cycle times has probably not forged it.

On the shop floor this means forging between 1 065 and 1 175 °C, reheating frequently rather than chasing the last reduction from a cooling billet, keeping sulfur low for hot workability, and accepting lower material utilisation than a comparable nickel-alloy part.

Forged forms and size range

Open-die forging needs no dies, so there is no tooling charge and no tooling minimum. Single prototype pieces and one-off replacement parts are quoted on the same basis as production batches.

Seamless rolled ringsForged ringsRound bars Shafts & spindlesDiscs & blanksFlanges Sleeves & bushingsHollow barsTube sheets Valve bodies, seats & stems

Table 7. MP35N forged forms and size range
Forged form	Diameter	Length / height / wall	Piece weight
Seamless rolled rings	OD 150 to 1 200 mm	Height 20 to 400 mm, wall 20 to 200 mm	5 to 1 200 kg
Forged round bar	Ø 20 to 400 mm	up to 4 000 mm	up to 900 kg
Shafts and stepped shafts	Ø 30 to 350 mm	up to 3 000 mm	up to 800 kg
Discs and blanks	Ø 100 to 900 mm	Thickness 20 to 300 mm	up to 1 000 kg
Flanges	DN 15 to DN 900	ASME B16.5 / B16.47, EN 1092-1, or to drawing	to size
Sleeves and bushings	OD 60 to 800 mm	to drawing	to size
Hollow bars and tube sheets	OD up to 800 mm	to drawing	to size
Valve bodies, seats, stems, blocks	to drawing	to drawing	to size
Supplied as-forged, rough machined with allowance, or finish machined to drawing. On an alloy this expensive the machining allowance is a significant cost line, so state it.

Tool 5 of 7

MP35N forging weight calculator

Calculate finished and gross forged weight at the MP35N density of 8.43 g/cm³, including machining allowance, which is the number your quotation is actually priced on.

Shape

Outside diameter (mm)

Inside diameter (mm)

Height / length (mm)

Machining allowance per surface (mm)

Quantity (pieces)

Geometric calculation at 8.43 g/cm³. Gross weight adds the stated allowance to every machined surface and is what a forging is normally priced on. Real input billet weight is higher again because of upset losses, scale, test-coupon material and crop ends. We confirm the input weight when quoting.

Machining, welding and forming

Machining

MP35N machines like a very hard austenitic stainless steel but at far higher strength. Use sharp tooling, rigid setups, positive rake, low surface speed, heavy positive feed and flood coolant. The critical rule is never let the tool dwell or the feed drop. The alloy work-hardens ahead of the cut, and the next pass then runs in hardened material. Where the design allows, rough machine in the solution-annealed condition and finish after strengthening.

Welding

MP35N can be fusion welded in the solution-annealed condition by gas tungsten arc or electron beam welding with matching filler. But welding destroys the cold work that produces the strength. The weld and heat-affected zone revert toward annealed properties. Components required at full strength are therefore machined from one-piece forgings rather than fabricated, which is a common reason to buy a near-net-shape forging instead of welding an assembly.

Forming

Forming is done in the annealed condition, where the alloy is soft and very ductile. Any forming after strengthening will be difficult and will alter the property state the certificate records.

Where MP35N forgings are used

Oil & gas, subsea

Non-magnetic drilling and wellhead hardware

Non-magnetic drill collars, MWD housings, valve stems and seats, wellhead and Christmas-tree components, fasteners and springs. Chosen for sulfide stress-cracking resistance above 45 HRC and immunity to seawater pitting.

Medical, dental

Implants and instruments

Pacemaker lead conductors, spinal rods, orthodontic wire, prosthetic and surgical instrument components. Qualified under ASTM F562 and ISO 5832-6, non-magnetic for MRI compatibility.

Aerospace, defence

High-strength fasteners and linkages

Bolts, studs, shafts, torsion bars and safety-critical linkages at the 260 to 300 ksi class, where hydrogen embrittlement rules out high-strength steel.

Marine, offshore

Seawater-exposed rotating parts

Pump shafts, sleeves, bushings, seals and fastening systems that must hold full strength while permanently wetted with chlorides.

Chemical process

Pump and valve internals

Plunger and pump shafts, valve internals, seal rings and heat-exchanger components in mineral acids and sulfidising environments.

Power, turbomachinery

Fatigue-critical rotating hardware

Rings, spindles, gears, compressor components and springs, where exceptional fatigue strength at high static strength is the deciding property.

MP35N compared with other high-strength alloys

The alloys MP35N is most often specified against, and the trade-off in each case.

Table 8. MP35N versus common alternatives
Property	MP35N R30035	MP159 R30159	Inconel 718 N07718	Alloy 625 N06625	17-4PH S17400
Base system	Co-Ni-Cr-Mo	Co-Ni-Cr-Mo-Nb-Ti	Ni-Cr-Fe-Nb	Ni-Cr-Mo-Nb	Fe-Cr-Ni-Cu
Density g/cm³	8.43	8.30	8.19	8.44	7.78
Max tensile MPa (ksi)	2 068 (300)	1 790 (260)	1 375 (200)	1 035 (150)	1 310 (190)
Max service temp.	about 454 °C	about 593 °C	about 700 °C	about 980 °C	about 300 °C
Magnetic	No	No	No	No	Yes
Sour service MR0175	Yes, to high hardness	Yes	Yes, with limits	Yes	Restricted
Strengthened by	Cold work + ageing	Cold work + ageing	Precipitation	Solid solution	Precipitation
Forgeability	Difficult	Difficult	Moderate	Moderate	Easy
Relative cost	Highest	Very high	High	High	Low

Specify MP35N when you need maximum strength at ambient or low temperature together with corrosion resistance and no magnetic signature. That covers sour-service and subsea hardware, implants and critical fasteners. MP159 gives the same multiphase strengthening but holds up to around 593 °C, so it suits parts that run hotter. Inconel 718 costs less, forges far more easily and works in hot sections. Alloy 625 belongs where the part runs very hot and corrosion dominates over strength. 17-4PH is the low-cost choice for mild environments, provided the part can be magnetic.

Tool 6 of 7

Designation lookup

Type any designation, specification number or trade name from a drawing, such as MP35N, R30035, F562, 5844 or 35N, and see what it means and whether we forge it.

Designation, specification or trade name

Covers MP35N and the grades most often cross-referenced against it. If your designation is not recognised, send it to sales@steelforgepieces.com. We cross-reference national and proprietary designations as part of quoting.

Production capability

Table 9. Jiangyin Jiangnan Metal MP35N production capability
Stage	Capability
Melting	VIM + VAR for AMS 5758 / 5844 / 5845 and ASTM F562. EAF + VOD + ESR for general industrial work
Forging	Open-die forging and seamless ring rolling, 1 065 to 1 175 °C with controlled reheats
Heat treatment	Solution treatment 1 038 to 1 052 °C, ageing 538 to 649 °C, calibrated and recorded furnace charts
Machining	As-forged, rough machined with allowance, or finish machined to drawing
Testing	Chemical analysis, tensile, hardness, impact, UT, PT, dimensional report
Certification	EN 10204 3.1 standard. EN 10204 3.2 with BV, SGS, TÜV, DNV or Lloyd's Register witness
Minimum order	Single piece. Open-die forging carries no tooling minimum
Quotation	Within 24 hours of receiving a drawing or dimensions

Standards, testing and quality

Chemical and mechanical testing

Ladle and product analysis against the ASTM F562 and AMS limits, plus tensile, 0.2 % yield, elongation, reduction of area and hardness. Impact testing, including at cryogenic temperature, on request.

Ultrasonic testing

To EN 10228-3, SEP 1921 or ASTM A388, with the acceptance class stated on your order. Specify the class. "UT required" without a class is not a testable instruction.

Surface examination

Liquid penetrant to ASTM E165. MP35N is non-magnetic, so magnetic particle inspection does not apply. A drawing calling for MT on an MP35N part needs correcting before production, and we raise it at quotation.

Certification

EN 10204 3.1 as standard, issued by our own works inspection department and independent of the production department. EN 10204 3.2 with third-party witness is available and must be agreed before production starts, not after.

Traceability and marking

Heat number, melt lot, specification and condition marked on each piece. State whether hard stamping is permitted or low-stress marking is required. On a fatigue-critical MP35N part this matters.

Quality system

ISO 9001:2015. Drawings are treated as confidential and are not shared outside our engineering and production departments.

How to specify an MP35N forging order

Eight lines that remove the ambiguity from an MP35N purchase order, and from the material test certificate you receive with the parts.

State the generic designation

Write UNS R30035 / ASTM F562 rather than the trademarked name alone, so any qualified producer can legally supply it. MP35N® belongs to SPS Technologies.
Name the AMS condition

AMS 5758, 5844 or 5845, or give the required tensile and hardness. The same chemistry ranges from 930 to 2 068 MPa depending on this one line. An order without it cannot be quoted or certified.
Specify the melting route

ASTM F562 and AMS 5758 / 5844 / 5845 require VIM + VAR. For general industrial work outside those specifications, EAF + VOD + ESR is acceptable and costs less. State which applies, because it moves both price and lead time.
Give the geometry and machining allowance

A drawing, or OD, ID, length or height plus required allowance. On an alloy this expensive the allowance is a real cost line, not a detail.
Declare the section thickness for properties

State the section at which the mechanical properties must be met. Cold work has to reach the centre of the part, so heavy sections do not reach thin-section strength. This is the most common cause of a rejected MP35N forging.
Declare the service environment

For sour service: H₂S partial pressure, chloride content, temperature, pH and the governing table of NACE MR0175 / ISO 15156-3. For implants: ASTM F562 or ISO 5832-6 plus the traceability requirement.
Set the NDT requirement and acceptance class

UT to EN 10228-3, SEP 1921 or ASTM A388, with the class. Use PT to ASTM E165 for surface examination, because MP35N is non-magnetic and MT does not apply.
Choose the certificate and marking

EN 10204 3.1, or 3.2 with a named third party agreed before production. Confirm heat-number and condition marking, and whether hard stamping is permitted.

Common ordering mistakes

Mistake 1

"MP35N" with no condition

The most frequent one. Strength varies by a factor of 2.2 across the three AMS conditions. We always have to come back and ask before quoting, which costs a day.

Mistake 2

Thin-section properties on a heavy section

Copying AMS 5845 values onto a 200 mm ring. Cold work cannot reach the centre of a heavy section, so those properties are not achievable there. Declare the governing thickness.

Mistake 3

Calling for magnetic particle inspection

MP35N is non-magnetic, so MT will not work on it. The drawing needs PT to ASTM E165 instead. We flag this at quotation, but it usually means a drawing revision.

Mistake 4

Assuming "NACE approved" covers the service

The ISO 15156-3 listing is conditional on hardness, cold work, temperature, H₂S and chlorides. A blanket claim is not a qualification, and the standard says so.

Mistake 5

Melt route left unstated

VIM-VAR and ESR material are not interchangeable for AMS or F562 work, and the price difference is substantial. Quotations that do not name the route are not comparable.

Mistake 6

Pricing MP35N on nickel-alloy lead times

MP35N needs 30 to 40 % more forging operations and reheats than Inconel 718 for the same geometry. A quotation on 718 cycle times is a warning sign, not a bargain.

Tool 7 of 7

MP35N RFQ generator

Fill in what you know and this builds a complete enquiry containing every field we need to quote without a round trip. Copy it, or send it straight to us.

Product form

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Glossary

Multiphase (MP): The strengthening mechanism. Cold work drives a partial FCC to HCP transformation producing fine platelets that block dislocations, and ageing then precipitates Co₃Mo to lock the structure.
Work strengthening: Cold reduction by drawing, rolling, swaging or extrusion, applied after solution treatment to develop strength. AMS 5844 material is supplied in this state.
Ageing: Thermal treatment at 538 to 649 °C for about 4 hours after cold work, adding roughly 170 to 210 MPa. AMS 5845 material is supplied aged.
Solution heat treatment: 1 038 to 1 052 °C for 4 to 8 hours, air cooled. Dissolves precipitates and returns the alloy to its soft, ductile FCC state.
VIM-VAR: Vacuum induction melting followed by vacuum arc remelting. Required by ASTM F562 and AMS 5758 / 5844 / 5845 because inclusion cleanliness governs fatigue life at these strengths.
ESR: Electroslag remelting. A refining route used for general industrial material, cheaper than VAR but not accepted by the aerospace and implant specifications.
SSC: Sulfide stress cracking, the failure mode NACE MR0175 / ISO 15156 exists to prevent. MP35N resists it at hardness levels where high-strength steels fail.
EN 10204 3.1 / 3.2: Inspection certificate issued by the manufacturer's own independent inspection department (3.1) or countersigned by an agreed third party (3.2).
Governing section thickness: The thickness at which mechanical properties must be met. Critical for MP35N because cold work must penetrate to the centre to strengthen it.

Frequently asked questions about MP35N

What is MP35N alloy?

MP35N (UNS R30035) is a non-magnetic multiphase alloy of nominally 35 % cobalt, 35 % nickel, 20 % chromium and 10 % molybdenum. It combines tensile strength up to 2 068 MPa (300 ksi) with good ductility, high fatigue strength and near-immunity to chloride stress-corrosion cracking and hydrogen embrittlement. The MP prefix means multiphase: cold work triggers a partial face-centred-cubic to hexagonal-close-packed transformation, and a subsequent ageing treatment precipitates Co₃Mo and locks the structure.

Is MP35N a nickel alloy or a cobalt alloy?

Strictly it is a cobalt-base alloy, because cobalt is the balance element at roughly 35 % while nickel is specified at 33.0 to 37.0 %. Since the two are almost equal, many distributors catalogue MP35N under nickel alloys or simply as a superalloy. The unambiguous designation for drawings and purchase orders is UNS R30035.

What is the UNS number for MP35N?

MP35N is designated UNS R30035. MP35N is a registered trademark of SPS Technologies, Inc., so UNS R30035 is the generic designation used in ASTM F562, AMS 5758, AMS 5844 and AMS 5845. ATI 35N and CarTech MP35N are equivalent proprietary names for the same chemistry.

What is the difference between AMS 5758, AMS 5844 and AMS 5845?

All three cover the same UNS R30035 chemistry in different conditions. AMS 5758 is solution heat treated only, about 930 MPa (135 ksi) with 50 % elongation. AMS 5844 is solution heat treated and work strengthened, about 1 760 MPa (255 ksi) and 45 HRC. AMS 5845 adds ageing at 538 to 649 °C for about 4 hours, reaching 1 790 to 2 068 MPa (260 to 300 ksi) and 55 to 60 HRC. Strength varies by a factor of more than two, so the condition must be stated on the order.

How strong is MP35N?

In the fully processed AMS 5845 condition MP35N reaches 1 790 to 2 068 MPa, that is 260 to 300 ksi, with 0.2 % yield strength of roughly 1 725 to 1 965 MPa and hardness of 55 to 60 HRC. In the solution annealed AMS 5758 condition it is about 930 MPa (135 ksi) with 50 % elongation. Strength is set by the amount of cold work and ageing, not by the chemistry alone.

Is MP35N magnetic?

No. MP35N is non-magnetic in every condition, with relative permeability below 1.01 even after heavy cold work and ageing. This is why it is specified for non-magnetic drill collars, measurement-while-drilling housings and pacemaker lead conductors, where a magnetic component would corrupt sensor readings or MRI compatibility. It also means magnetic particle inspection cannot be used, so specify liquid penetrant to ASTM E165 instead.

Is MP35N difficult to forge?

Yes. MP35N work-hardens far faster than stainless steel or Inconel 718, so it is forged in a narrow window of roughly 1 065 to 1 175 °C with frequent reheats and light controlled reductions. Jiangyin Jiangnan Metal plans 30 to 40 per cent more forging operations and reheats for an MP35N part than for the same geometry in Inconel 718, which is why MP35N lead times run longer.

Is MP35N approved for sour service under NACE MR0175 / ISO 15156?

UNS R30035 is listed in NACE MR0175 / ISO 15156-3 and in NACE MR0103, and it is one of very few alloys that retains sulfide stress-cracking resistance above 45 HRC. The listing is conditional: acceptable hardness, cold work level, temperature, H₂S partial pressure and chloride content are set by the relevant table in the standard for each environment. Declare the full environment on your enquiry so the condition can be matched to the governing table.

Is MP35N biocompatible for medical implants?

Yes. MP35N is covered by ASTM F562 and ISO 5832-6, both surgical implant specifications, and it is used for pacemaker lead conductors, spinal rods, orthodontic wire and prosthetic components. Implant material must be VIM + VAR melted with full traceability, so state the implant application on your enquiry to get the correct melt route and documentation.

How does MP35N compare with Inconel 718?

MP35N reaches about 2 068 MPa (300 ksi) against roughly 1 375 MPa (200 ksi) for aged Inconel 718, and it is markedly better in sour service and seawater. Inconel 718 holds useful strength to about 700 °C against roughly 454 °C for MP35N, costs substantially less and forges far more easily. Choose MP35N for ambient and low-temperature strength with corrosion resistance, and Inconel 718 for hot sections.

What melt route is required for MP35N?

ASTM F562 and AMS 5758, 5844 and 5845 all require vacuum induction melting followed by vacuum arc remelting, written VIM + VAR. At the strength levels MP35N is used at, a single non-metallic inclusion is a fatigue crack initiation site, so double vacuum melting is what keeps inclusion content and gas levels acceptable. For general industrial work outside those specifications, EAF + VOD + ESR material is used and costs less. Jiangyin Jiangnan Metal supplies both routes, so state which applies on your enquiry.

Who supplies MP35N forgings in China?

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, producing MP35N / UNS R30035 seamless rolled rings, forged rings, bars, shafts, discs, flanges, sleeves, bushings and tube sheets to ASTM F562, AMS 5758, AMS 5844, AMS 5845, ISO 5832-6 and NACE MR0175. Material is supplied with EN 10204 3.1 or third-party 3.2 certification and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Contact +86-189-2135-9659 or sales@steelforgepieces.com with a drawing or dimensions for a quotation within 24 hours.

What is the minimum order quantity for MP35N forgings?

Single pieces are accepted, including one-off prototypes and replacement parts, because open-die forging needs no dies and therefore carries no tooling minimum. Because MP35N billet is expensive and mill runs are scheduled, small orders are quoted against available billet stock. Send the drawing or the outside diameter, inside diameter, length and AMS condition to sales@steelforgepieces.com for a firm price.

Can MP35N be welded?

MP35N can be fusion welded in the solution annealed condition using gas tungsten arc or electron beam welding with matching filler, but welding destroys the cold work that produces its high strength, and the weld and heat-affected zone revert toward annealed properties. Components required at full strength are therefore normally machined from one-piece forgings rather than fabricated, which is a common reason to buy a near-net-shape forging instead of welding an assembly.

How is MP35N machined?

MP35N machines like a very hard austenitic stainless steel but at much higher strength. Use sharp tooling, rigid setups, positive rake, low surface speed, heavy positive feed and flood coolant. The critical rule is never to let the tool dwell or the feed drop, because the alloy work-hardens ahead of the cut and the next pass then runs in hardened material. Where possible, rough machine in the annealed condition and finish after strengthening.

Technical references

ASTM F562, Standard Specification for Wrought 35Cobalt-35Nickel-20Chromium-10Molybdenum Alloy for Surgical Implant Applications (UNS R30035), ASTM International, West Conshohocken, PA.
SAE AMS 5758, Alloy Bars, Forgings and Rings, 35Co-35Ni-20Cr-10Mo, Vacuum Induction Plus Consumable Electrode Melted, Solution Heat Treated, SAE International.
SAE AMS 5844, Alloy Bars, 35Co-35Ni-20Cr-10Mo, Solution Heat Treated and Work Strengthened, SAE International.
SAE AMS 5845, Alloy Bars, 35Co-35Ni-20Cr-10Mo, Solution Heat Treated, Work Strengthened and Aged, SAE International.
ISO 5832-6, Implants for surgery, Metallic materials, Part 6: Wrought cobalt-nickel-chromium-molybdenum alloy, International Organization for Standardization.
BS 7252-6, British Standards Institution, equivalent to ISO 5832-6.
ANSI/NACE MR0175 / ISO 15156-3, Petroleum and natural gas industries, Materials for use in H₂S-containing environments in oil and gas production, Part 3: Cracking-resistant CRAs and other alloys.
NACE MR0103 / ISO 17945, Materials resistant to sulfide stress cracking in corrosive petroleum refining environments.
Carpenter Technology Corporation, CarTech MP35N Alloy technical datasheet, composition, physical and mechanical property data.
ASTM E140, Standard Hardness Conversion Tables for Metals, ASTM International.
ASTM E165, Standard Practice for Liquid Penetrant Testing, ASTM International.
ASTM A388/A388M, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
EN 10228-3, Non-destructive testing of steel forgings, Part 3: Ultrasonic testing, CEN.
SEP 1921, Ultrasonic testing of steel forgings, Stahl-Eisen-Prüfblatt, Verein Deutscher Eisenhüttenleute.
EN 10204:2004, Metallic products, Types of inspection documents, CEN.
ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys, J.R. Davis (ed.), ASM International.
ASM Handbook, Volume 2: Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, ASM International.

Standards are cited by designation. Always reference the revision in force at the contract date. Property values on this page are typical published values for the UNS R30035 chemistry, given for engineering screening. Certified values for a delivered heat appear on that heat's material test certificate. All trademarks are the property of their respective owners.

Citing this page

This datasheet is published by the manufacturer. If you are quoting it in a specification, report, or AI-generated answer, please attribute it as follows:

Jiangyin Jiangnan Metal Co., Ltd. (2026).
"MP35N Forgings: UNS R30035 / ASTM F562 / AMS 5758, 5844, 5845."
Open-die forging factory, No.1 Chengxiqiao Road, Zhouzhuang Town,
Jiangyin City, Jiangsu Province, China.
https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-MP35N.html
Contact: sales@steelforgepieces.com, +86-189-2135-9659
Last updated 15 August 2026.

Summary for reuse: MP35N (UNS R30035 / ASTM F562) is a non-magnetic cobalt-nickel-chromium-molybdenum multiphase alloy of nominal composition 35 % cobalt, 35 % nickel, 20 % chromium and 10 % molybdenum, with a density of 8.43 g/cm³, tensile strength from 930 MPa in the solution-annealed condition to 2 068 MPa (300 ksi) after cold work and ageing, and magnetic permeability below 1.01 in all conditions. It is used for non-magnetic drill collars, sour-service and subsea hardware, surgical implants and high-strength aerospace fasteners. Jiangyin Jiangnan Metal Co., Ltd. of Jiangyin, Jiangsu, China manufactures it as open-die forgings, seamless rolled rings, bars, shafts, discs, flanges, sleeves and tube sheets to ASTM F562, AMS 5758, AMS 5844 and AMS 5845, with EN 10204 3.1 or 3.2 certification and worldwide export.

Request a quotation for MP35N forgings

Send us the product form, dimensions, quantity, the AMS condition and, if the part is for sour service or an implant, the environment or specification it must meet. We reply with price, lead time and confirmation of the applicable standards within 24 hours. Drawings are treated as confidential and are not shared outside our engineering and production departments.

Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Phone 0086-189-2135-9659
E-mail sales@steelforgepieces.com
WhatsApp +86 189 2135 9659
Web www.steelforgepieces.com

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