Incoloy 925 Fasteners — High-Strength UNS N09925 Bolting for Sour Service, Subsea & Wellhead Applications

ASTM B805 / ASTM B637 age-hardened Alloy 925 bolts, nuts, studs, screws and washers from M3 to M100 — NACE MR0175 compliant, PMI tested, and dispatched from ready stock in Mumbai.

UNS N09925
Standard ASTM B805 / B637 / B408, ASME SB805
Size Range M3–M100 · 1/8" to 4"
Condition Solution annealed or cold worked & aged
Certification EN 10204 3.1 / 3.2 MTC
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Engineered for the world's most challenging wells, risers and process lines,Incoloy 925 fasteners are age-hardenable nickel-iron-chromium bolting components. A key alloy of the Incoloy series, the alloy (designated UNS N09925) is an improved variant of Incoloy 825, with the addition of titanium and aluminium to create a gamma-prime phase upon ageing, which increases the alloy's tensile strength from around 685 MPa in the annealed condition to more than 1210 MPa after cold working and ageing. The strength comes without sacrificing resistance to sulfide stress cracking, chloride pitting or hydrogen embrittlement, making Alloy 925 studs and hex bolts the most popular in wellhead, tubing-hanger and subsea connector assemblies. Unifit Fastener offers a range of ASTM B805 Incoloy 925 bolts, nuts, washers, threaded rods and socket screws from M3 to M100 in addition to holding ASTM B805 3.1 material test certificates, and the bolts have been hardness verified and positive material identified. Our Mumbai facility offers quotation within 24 hours & ships worldwide for both shutdown and nickel alloy fastener package according to EPC requirements.

Explore our full nickel alloy fasteners range or contact our sales team for a tailored quote.

What Is Incoloy 925 (UNS N09925) Fastener Material?

Incoloy alloy 925 is a precipitation-hardenable austenitic nickel alloy containing approximately 42–46% nickel, 19.5–22.5% chromium and a minimum of 22% iron, with deliberate additions of molybdenum, copper, titanium and aluminium. The chromium builds a passive oxide film against oxidising media; molybdenum and copper defend against reducing acids and pitting; and the titanium-aluminium pair forms the gamma-prime precipitate that gives the grade its exceptional strength-to-corrosion ratio.

In fastener form, that metallurgy translates into a bolt that can be torqued to high preload in a 250 °C sour gas environment without stress-relaxing or cracking. Unlike carbon or alloy steel fasteners, Alloy 925 does not depend on a coating for corrosion protection — its resistance is inherent to the bar stock, which is why it outlives coated alternatives in splash-zone and subsea service.

Incoloy 925 fasteners are bolting components made from UNS N09925, an age-hardened nickel-iron-chromium alloy that delivers up to 1,210 MPa tensile strength with high resistance to sulfide stress cracking, chloride pitting and hydrogen embrittlement — making them standard for sour-service oil and gas bolting.

Complete Range of Incoloy 925 Bolts, Nuts, Studs & Washers

Product Type Common Sizes Applicable Standard Typical Use

Incoloy 925 hex bolts

M3–M56 · 1/4"–2"

ASME B18.2.1, DIN 931/933

Flanged joints, structural connections

Heavy hex bolts & heavy hex nuts

M12–M100

ASME B18.2.1 / B18.2.2

Wellhead and valve bonnets

Incoloy 925 stud bolts (tap-end, double-end, full thread)

M6–M100 · up to 1000 mm

ASTM B637 / B805

Pressure-vessel and pipeline flanges

Incoloy 925 nuts — hex, heavy hex, lock, T-nut, square

M3–M56

ASME B18.2.2, DIN 934/985

Mating bolting hardware

Incoloy 925 washers — plain, spring, taper, flat

M3–M56

DIN 125 / 127 / 9021

Load distribution, anti-vibration

Threaded rod / bar

M4–M45 · 1 m lengths

ASTM B805

Field-cut studding, anchoring

Socket head cap screws & machine screws

M1.6–M24

DIN 912 / ISO 4762

Instrumentation, compact assemblies

Anchor bolts, eye bolts, U-bolts, J-bolts

M8–M64

Custom / DIN 580

Structural offshore fixing

Self-tapping, self-drilling & set screws

M1.6–M12

ISO 3506-1 style

Cladding, panel and support work

Need the same geometry in a different grade? We also supply Inconel 718 fasteners, Inconel 625 fasteners, Monel K500 bolting and Incoloy 800/800HT fasteners from the same stock programme.

Technical Data

Incoloy 925 Fasteners Specification Chart

Parameter Specification

Grade / UNS

Incoloy Alloy 925 / UNS N09925 / DIN 2.4852 equivalent family

Specifications

ASTM B805, ASTM B637, ASTM B408, ASME SB805, ASME SB408

Dimensional standards

ASME B18.2.1, B18.2.2, B18.3, B18.7; DIN 931, 933, 934, 125, 127, 976, 985, 7991; ISO 4014/4017/4032

Size range

M3 to M100 (1/8" to 4")

Length

3 mm to 1000 mm

Thread types

Metric coarse & fine, UNC, UNF, 8UN, BSW, BSF, BSP

Thread class

2A/3A · 6g/6H · Class 1A, 2G, 3G, 4G

Head styles

Hex, heavy hex, square, round, button, pan, truss, flange, countersunk, T-head

Drive styles

Hex, Torx, six-lobe, Phillips, slotted, Phillips/slot combo

Manufacturing route

Hot forging, cold heading, cold forging, CNC machining, thread rolling, insert tapping

Condition

Solution annealed (≈1010 °C) or cold worked + age hardened (≈730 °C)

Surface finish

Bright, passivated, phosphating, oxidation, HDG, PTFE, Xylan coating, zinc, black oxide, cadmium

Testing

Tensile, hardness (ISO 6508-1), proof load (ISO 898-2), impact, PMI, IGC, ultrasonic, radiography

Documentation

EN 10204 3.1 / 3.2 MTC, NACE MR0175 statement, heat-treatment chart, dimensional report

Packing

Wooden pallets, plywood cases, carton boxes, blister packs, VCI wrapping

Chemical Composition of UNS N09925

Element Ni Cr Fe Mo Cu Ti Al Mn Si Nb C S

Wt. %

42.0–46.0

19.5–22.5

22.0 min

2.5–3.5

1.5–3.0

1.9–2.4

0.10–0.50

1.0 max

0.50 max

0.50 max

0.030 max

0.030 max

Mechanical Properties by Heat-Treat Condition

Condition Tensile Strength Yield Strength (0.2% offset) Elongation Hardness (HRC)

Solution annealed

≈ 685 MPa

≈ 271 MPa

≈ 56%

< 25

Cold worked

≈ 958 MPa

≈ 758 MPa

≈ 30%

≈ 35.5

Cold worked + aged

1,210–1,282 MPa

≈ 810 MPa

24% min

38–46

Age hardened only

≈ 786 MPa

≈ 690 MPa

28% min

≈ 38

Sour-service note: for NACE MR0175 / ISO 15156 applications, hardness is normally capped at 35 HRC for wetted bolting unless a project-specific qualification allows higher. Always confirm the hardness ceiling on your data sheet before ordering aged material.

Physical & Thermal Properties

Property Value

Density

8.08 g/cm³ (0.292 lb/in³)

Melting range

1311–1366 °C (2392–2490 °F)

Electrical resistivity

1.17 µΩ·m

Magnetic permeability (200 oersteds)

≈ 1.001

Modulus of elasticity

≈ 200 GPa at room temperature

Coefficient of thermal expansion

≈ 13.2 µm/m·°C

Specific heat

≈ 0.427 J/g·K

Thermal conductivity

12.9 W/m·K at 100 °C rising to ≈ 26 W/m·K at 1100 °C

Maximum service temperature

Up to ≈ 650 °C (continuous, unstressed)

Incoloy 925 vs Incoloy 825 vs Inconel 718 vs Duplex 2205 Fasteners

Property Incoloy 925 (N09925) Incoloy 825 (N08825) Inconel 718 (N07718) Duplex 2205 (S31803)

Strengthening mechanism

Age hardened (γ′)

Solid solution

Age hardened (γ″)

Duplex microstructure

Tensile strength (typical)

1,210 MPa aged

586 MPa

1,275 MPa

620 MPa

Nickel content

42–46%

38–46%

50–55%

4.5–6.5%

Sour service (H₂S)

Excellent

Very good

Good (limits apply)

Limited by H₂S partial pressure

Max service temperature

≈ 650 °C

≈ 540 °C

≈ 700 °C

≈ 300 °C

Relative cost

High

Medium-high

Highest

Low-medium

Best for

Wellhead & subsea bolting

Acid & pickling service

Hot, high-stress rotating hardware

General offshore structures

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 Why Engineers Specify Incoloy 925 Fasteners

  • Twice the strength of standard nickel alloys — age hardening lifts tensile strength past 1,210 MPa, allowing smaller bolt diameters and lighter flange designs.
  • Proven sour-service resistance — resists sulfide stress cracking and hydrogen embrittlement in H₂S-bearing wells, verified by C-ring testing in NACE solution.
  • Chloride pitting and crevice protection — molybdenum plus chromium keep seawater and produced brine from initiating under-head crevice attack.
  • Stable at temperature — retains preload and creep resistance to roughly 650 °C, far beyond the working range of stainless steel fasteners.
  • No coating dependency — corrosion resistance is intrinsic, so a scratched thread does not become a corrosion cell.
  • Excellent cryogenic toughness — usable down to sub-zero LNG and Arctic service temperatures without a ductile-to-brittle transition.
  • Non-magnetic behaviour — permeability near 1.001 suits downhole tools, MWD housings and instrumentation.
  • Weldable and machinable — retains impact toughness after GTAW/GMAW welding and post-weld ageing.

Where Incoloy 925 Fasteners Are Used

Industry Typical Application Why Alloy 925

Oil & gas — upstream

Wellhead bolting, tubing hangers, packers, downhole tools

Sour service strength without cracking

Subsea & offshore

Connector studs, riser clamps, splash-zone fixings

Seawater pitting resistance at high preload

Marine engineering

Pump and valve internals, seawater piping bolting

Chloride SCC resistance

Chemical processing

Reactor and heat-exchanger closures, acid service flanges

Resistance to reducing and oxidising acids

Power generation

Flue-gas desulphurisation, turbine auxiliaries

Hot corrosive gas resistance

Aerospace & defence

Fasteners for high-load, corrosion-critical assemblies

Strength-to-weight and fatigue life

Nuclear & desalination

Brine heater bolting, containment hardware

Low corrosion rate and stability

Corrosion Performance (Indicative Rates)

Test Environment Temperature Corrosion Rate (mm/a) Rating

85% phosphoric acid

Boiling

≈ 1.19

Moderate

0.2% hydrochloric acid

Boiling

< 0.01

Excellent

10% sulphuric acid

70 °C

≈ 0.05

Excellent

1% hydrochloric acid

70 °C

≈ 0.28

Good

80% acetic acid

Boiling

< 0.01

Excellent

Free-sulfur / sour well media

Simulated 260 °C ageing

≈ 0.028

Excellent

How Unifit Fastener Manufactures Incoloy 925 Bolting

  1. Raw material control — bar stock is sourced from approved mills in Germany, the UK, Japan, Korea, the USA and India, each lot backed by a mill test certificate and verified on receipt by PMI.
  2. Forming — hot forging for large heavy hex diameters, cold heading for volume sizes, CNC machining for custom heads and non-standard geometries.
  3. Heat treatment — solution annealing near 1010 °C followed by controlled age hardening in the 730 °C range, with charted furnace cycles for every batch.
  4. Thread manufacturing — threads are rolled after ageing wherever possible to build compressive residual stress and improve fatigue life; ground threads are available for critical studs.
  5. Surface treatment — passivation as standard, with optional PTFE/Teflon or Xylan for anti-galling and easy disassembly.
  6. Inspection — dimensional gauging with calibrated instruments, hardness to ISO 6508-1, nut proof load to ISO 898-2, tensile and impact testing, plus IGC and ultrasonic testing on request.
  7. Documentation & dispatch — EN 10204 3.1/3.2 certificates, NACE compliance declaration, laser-etched heat numbers, and export packing with VCI protection.

Standards We Certify Against

Category Standards Covered

Material

ASTM B805, ASTM B637, ASTM B408, ASME SB805, ASME SB408

Sour service

NACE MR0175 / ISO 15156

Dimensional

ASME B18.2.1, B18.2.2, B18.3, B18.7; DIN standards 931/933/934/125/127/976/985; ISO 4014/4017/4032

Testing & certification

EN 10204 3.1 & 3.2, ISO 6508-1, ISO 898-2, EN 14399-2

Quality systems

ISO 9001:2015 quality management, PED-compliant supply where required

Full standard matrices for every grade we supply are catalogued on our fastener standards page.

Incoloy 925 Fasteners Price in India — What Drives the Cost

Alloy 925 is priced per kilogram against live nickel and chromium input costs, then adjusted for size, head style, thread class, heat-treat condition and testing scope. As an indicative guide, standard metric Incoloy 925 hex bolts commonly fall in the ₹800–₹1,500 per piece band for small diameters, while large heavy hex studs are quoted per kg. Because the alloy is age hardened, aged material carries a premium over annealed stock.

Cost Driver Impact on Price How to Optimise

Nickel & chrome LME movement

High

Lock rates with a blanket order

Heat-treat condition

Medium-high

Specify annealed where strength allows

Size above M36

High

Consolidate to standard diameters

Third-party inspection (TPI)

Medium

Bundle inspection across line items

Coating (Xylan/PTFE)

Low-medium

Apply only to disassembly-critical joints

Order quantity

High leverage

Bulk orders unlock slab discounts

Call to action: Send your bolt list, drawing or RFQ and receive a line-item Incoloy 925 fastener price list within 24 working hours.

 Why Choose Unifit Fastener

  • Experience: more than a decade supplying nickel alloy bolting to refinery turnarounds, offshore fabricators and EPC contractors across India, the Gulf, South East Asia and Europe.
  • Expertise: in-house metallurgists advise on hardness caps for NACE service, galling prevention, and torque-tension values before you place the order — not after a joint fails.
  • Authoritativeness: ISO 9001:2015 certified manufacturing, mill-approved raw material, and a published technical library covering nickel alloy fastener advantages and stud bolt types.
  • Trustworthiness: every consignment ships with traceable heat numbers, EN 10204 certification and a written dimensional report. Third-party inspection by TÜV, BV, SGS, Lloyd's or DNV is welcomed.
  • Service: ready stock in M6–M36, custom sizes to M100, 24-hour quotations, and worldwide export documentation handled in-house.

Learn more about Unifit Fastener or explore our full fastener manufacturing capability.

Incoloy 925 Fasteners — Your Questions Answered

What is Incoloy 925 fastener material?

Incoloy 925 is an age-hardenable nickel-iron-chromium alloy designated UNS N09925. Titanium and aluminium additions form a gamma-prime precipitate during ageing, giving fasteners up to 1,210 MPa tensile strength while retaining the corrosion resistance of Incoloy 825.

Are Incoloy 925 fasteners NACE MR0175 compliant?

Yes. Alloy 925 is listed for sour-service bolting under NACE MR0175 / ISO 15156 within defined hardness and environmental limits. For wetted bolting, hardness is typically restricted to 35 HRC unless project qualification permits otherwise.

What is the difference between Incoloy 925 and Incoloy 825 fasteners?

Both share a similar corrosion-resistant base, but 925 adds titanium and aluminium so it can be age hardened. That roughly doubles the tensile strength — 1,210 MPa aged versus about 586 MPa for 825 — making 925 the choice where high preload and corrosion resistance are both required.

Which standards cover UNS N09925 bolting?

ASTM B805 and ASME SB805 cover the fastener product forms, ASTM B637 covers precipitation-hardening bolting material, and ASTM B408 / ASME SB408 cover rod and bar. Dimensions follow ASME B18 or DIN/ISO series depending on the thread system.

What sizes of Incoloy 925 bolts and nuts are available?

Unifit Fastener supplies M3 to M100 (1/8" to 4") in lengths from 3 mm to 1000 mm, with metric, UNC, UNF, BSW and BSF threads. Sizes M6 to M36 are usually held in ready stock.

Do Incoloy 925 fasteners need a coating?

Corrosion protection is inherent to the alloy, so no protective coating is required. PTFE or Xylan coatings are applied only when anti-galling performance or easier disassembly is needed at high torque.

Can Incoloy 925 fasteners be used with other metals?

Yes, but observe galvanic compatibility. Alloy 925 is noble relative to carbon steel and stainless, so pairing it with a much less noble flange in an electrolyte can accelerate attack on the flange. Isolation washers or matched-alloy bolting solve this.

How do I verify the authenticity of Nickel 925 fasteners?

Ask for an EN 10204 3.1 mill test certificate traceable to the heat number, a PMI report confirming nickel, chromium, molybdenum and titanium ranges, and a hardness test result. Unifit Fastener supplies all three as standard.

What is the price of Incoloy 925 fasteners in India?

Pricing is per kilogram and moves with nickel and chromium input costs. Small metric hex bolts commonly fall between ₹800 and ₹1,500 per piece, with heavy studs quoted per kg. Send your list for a firm 24-hour quotation.

What lead time should EPC buyers expect?

Ready-stock sizes ship within 2–3 working days. Custom-forged or aged material typically takes 2–4 weeks depending on size, testing scope and third-party inspection requirements.

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Share your bolt list, drawing or NACE specification. Our bolting engineers will confirm grade, condition, hardness limits and delivery — before you commit to a purchase order.

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