2026-09-21 Materials & Coatings

Inconel & Nickel Alloy Fasteners Manufacturer: Inconel 625, 718, Monel and Hastelloy Bolts

When the joint sees 600°C, seawater, sour gas or concentrated chemicals, a stainless fastener stops being an option — the material selection moves to nickel alloys. Yuanpai manufactures Inconel, Monel and Hastelloy fasteners — hex bolts, double end studs, nuts and washers — for high-temperature, sour and marine service, with traceability and certification that match project review.

Yuanpai — Nickel Alloy Fasteners Quick Reference:

- Grades: Inconel 625 (UNS N06625 / DIN 2.4856), Inconel 718 (UNS N07718 / DIN 2.4668), Monel 400 (N04400 / 2.4360), Monel K500 (N05500 / 2.4375), Hastelloy C276 (N10276 / 2.4819)

- Products: hex bolts, double end studs, nuts and washers in ASME B16.5 and metric sizes

- Standards: ASTM B446 (625), B637 (718), B164 (Monel 400), B865 (K500), B574 (C276)

- Sizes: M8 – M64 (5/16" – 2-1/2"), lengths per project BOM

- Service: high-temperature, sour service (NACE MR0175 / ISO 15156), seawater and chemical service

- Certification: EN 10204 3.1, PMI verification, hardness and tensile reports

Based on our supply records to global EPC and OEM projects, nickel alloy fastener acceptance usually hinges on three practical details: correct grade and condition selection, hardness control for sour service, and complete certification.

Nickel Alloy Grades: What Each One Is For

Grade	UNS	Key property	Typical service
Inconel 625	N06625	Solid-solution strengthened, excellent corrosion and oxidation resistance	Sour gas, seawater, chemical processing, high temperature
Inconel 718	N07718	Precipitation hardened, very high strength	High-strength bolting, aerospace-adjacent industrial service
Monel 400	N04400	Nickel-copper, seawater and caustic resistance	Marine, caustic, HF service
Monel K500	N05500	Age-hardened Monel, high strength	Pump shafts, valve trim, sour marine service
Hastelloy C276	N10276	Nickel-molybdenum-chromium, extreme corrosion resistance	Aggressive chemicals, flue gas desulfurization

Selection is driven by the service condition, not by price. Inconel 625 is the workhorse for corrosive high-temperature bolting; Inconel 718 is chosen where the joint needs higher strength; Monel K500 covers sour marine service where hardness limits allow; C276 is specified where no other grade survives the chemistry.

Inconel 625 vs 718: Which for Your Bolting

The two most requested Inconel grades behave differently:

Inconel 625 — solid-solution strengthened, typically supplied in the solution-annealed condition. Excellent pitting and crevice corrosion resistance in chloride and sour environments, with good strength to about 650°C. The default choice for corrosive service where a wide operating window is needed.
Inconel 718 — precipitation hardened through solution treatment plus aging, delivering substantially higher tensile and yield strength. Used where clamp load is critical at elevated temperature. Hardness and strength come with tighter processing control; specify the condition (Grade 1 solution annealed or Grade 2 solution treated and aged, per ASTM B637).

For flange bolting in sour service, 625 is the more common selection; for high-clamp-load applications, 718. The project material specification decides. For projects where standard stainless grades are sufficient, see our Stainless Steel Fasteners guide for A2/A4 options. For the complete stud bolt configuration and flange bolting set details, refer to our Stud Bolts page.

Monel and Hastelloy Service Windows

Monel 400 and K500 — nickel-copper alloys with excellent resistance to seawater, marine atmospheres and caustic solutions. K500 achieves high strength through age hardening; in sour service the hardness must be verified against NACE MR0175 / ISO 15156 limits.
Hastelloy C276 — the most corrosion-resistant grade we machine, specified for aggressive chemical service where pitting and stress corrosion cracking resistance beyond stainless is mandatory. Higher cost and longer lead time; only specified when the service demands it. Note: Hastelloy C276 has specific NACE MR0175 / ISO 15156 restrictions — it is approved for sour service within defined temperature and hardness limits. Confirm the project-specific NACE compliance requirements at RFQ stage.

For sour service limits across the nickel family, the NACE MR0175 / ISO 15156 material and hardness requirements apply — see our Custom Fastener Engineering Guide for how we handle sour service selection.

Manufacturing and Certification for Alloy Fasteners

Nickel alloy fasteners are manufactured with controlled processing:

Material control — bar stock from certified mills with heat numbers, PMI verified on receipt; chemical composition documented per heat
Heat treatment — solution annealing (625, Monel) or solution treatment and aging (718, K500) per standard, with hardness and tensile verification
Machining and threading — turned or cold-formed to size; thread fit verified with calibrated gauges; galling control on stainless and nickel threads
PMI verification — positive material identification on finished parts per lot, with reports included in the certificate package
Traceability — heat number traceability from raw bar to finished batch, supported by EN 10204 3.1 certificates and test reports

For hex bolt and nut configurations in nickel alloys, explore our Hex Bolts, Nuts & Washers range. Yuanpai supplies nickel alloy fasteners to global EPC contractors and international distributors across the Middle East, Southeast Asia, Europe and the Americas, with worldwide delivery and full documentation support.

Common Specification Mistakes in Nickel Alloy RFQs

Three omissions cause most alloy fastener order delays:

Condition not stated — "Inconel 718" alone does not define annealed versus aged condition. State the ASTM standard and condition (e.g. ASTM B637, Grade 2, solution treated and aged).
Hardness limit not defined — for sour service, state the hardness limit and the sour service standard (NACE MR0175 / ISO 15156) so the heat treatment is set correctly.
Certificate scope not defined — state whether 3.1 certificates, PMI reports and third-party inspection are required, and the acceptance criteria.

Providing these items at RFQ stage reduces clarification cycles during technical review.

FAQ

Q: What is the difference between Inconel 625 and 718 fasteners?

A: Inconel 625 is solid-solution strengthened with excellent corrosion resistance, the default for corrosive high-temperature bolting. Inconel 718 is precipitation hardened for higher strength and is used where clamp load at temperature is critical. The service condition decides.

Q: Are nickel alloy fasteners suitable for sour service?

A: Yes, several grades are used in sour service, subject to NACE MR0175 / ISO 15156 material and hardness requirements. The grade, hardness and heat treatment must be verified against the project specification.

Q: What certificates do you provide?

A: EN 10204 3.1 material certificates, PMI reports, hardness and tensile reports, and dimensional inspection reports per lot. Third-party inspection with witness is available where the project requires.

Q: What is the minimum order quantity?

A: Common sizes start from about 500 pieces depending on grade and size, with project-specific quantities quoted by requirement. Send the BOM and our team will confirm the MOQ and lead time within one working day.

Get your nickel alloy fastener quote within one working day — simply reply with:

Grade & condition (e.g. Inconel 625, ASTM B446, solution annealed)
Size & type (e.g. M24 x 150 double end stud, Inconel 625 with matching 625 nuts)
Quantity & certificate scope (e.g. 2,000 sets with 3.1 + PMI)

Download the alloy fastener specification checklist — grade, condition, hardness limit and certificate requirements.

Request sample kits — evaluate material identity, thread finish and certificate documentation before ordering.

Direct WhatsApp engineering support: [+1 XXX XXX XXXX] — send the BOM or project inquiry directly to our engineering team.