Incoloy bolts are premium nickel-iron-chromium fasteners engineered for demanding chemical and high-temperature environments; they combine exceptional corrosion resistance, useful high-temperature strength, and reliable dimensional stability, making them the preferred choice for petrochemical, marine, and power-generation assemblies where ordinary stainless steels fail.

What are Incoloy bolts?

“Incoloy” is a family name for nickel-iron-chromium alloys engineered for elevated-temperature strength and resistance to corrosive media (notably reducing acids, chloride environments, and many chemical process streams). Bolts and fasteners produced in Incoloy grades use the alloy’s balance of nickel and chromium to deliver both mechanical load capacity and corrosion resistance where conventional carbon or stainless steels are inadequate.

Key Incoloy grades used for fasteners

Common Incoloy alloys specified for fasteners include:

• Incoloy 800 / 800H / 800HT (UNS N08800 / N08810 / N08811): excellent scale and oxidation resistance plus good creep resistance at moderate elevated temperatures; often used where stability in the 600–1100°F (315–593°C) range is required.

• Incoloy 825 (UNS N08825): notable for outstanding resistance to many reducing environments, including sulfuric acid and chloride-bearing media; widely specified in chemical processing piping and fasteners.

• Newer or niche Incoloy/INCOLOY® variants (e.g., 945 / 925): used where age-hardening or higher strength/corrosion packages are required in oil & gas or subsea service.

Propiedades de los materiales

Citation note: datasheets and manufacturer technical bulletins summarize mechanical and thermal performance for each INCOLOY® grade; engineers should always use manufacturer tables for design limits.

Composición química

Below are simplified composition windows for the two most commmonly used Incoloy fastener alloys. These are representative ranges — always verify exact composition on mill test certificates (MTC) for specific fastener lots.

Incoloy 800 (UNS N08800) — typical composition (wt%)

Incoloy 825 (UNS N08825) — typical composition (wt%)

(Source: manufacturer technical bulletins and metallurgical references — these ranges are typical for engineering selection and procurement).)

Machinability, forming and recommended practices

• Maquinabilidad: Incoloy alloys are generally more difficult to machine than austenitic stainless steels. Grade 800 shows moderate machinability when correct tooling and feeds are applied; grade 825 is slightly more gummy because of higher nickel and copper, which can cause work-hardening. Use carbide tooling, modest depths of cut, steady coolant, and slow feed rates for consistent results.

• Threading & cold forming: Many Incoloy fasteners are manufactured from bar stock by cold heading where feasible, but some heavier sections and high-strength conditions require hot forming and finishing. Thread rolling (preferred) or cutting (for small runs) are both used — specify the manufacturing method if thread fit/strength is critical.

• Soldadura y unión: Incoloy 800 family welds readily with matching filler metals; 825 also welds well but post-weld heat treatment considerations and filler selection should follow manufacturer practice. For fasteners, welding is uncommon except in sub-assemblies.

Practical recommendation: Ask your vendor for recommended tooling parameters and request sample production runs to validate thread form and torque-tightening behaviour under service conditions.

Typical applications and where Incoloy bolts outperform alternatives

• Petrochemical & chemical process equipment: bolts in heat exchangers, pressure vessels, and piping systems where sulfide/chloride attack or reducing acids occur.

• Power generation & boilers: components exposed to high temperatures and cyclic stresses (800/800H/HT are common here).

• Marine / desalination: where seawater or brackish environments demand better performance than standard stainless steels.

• Oil & gas (downhole & topside): for sour or chloride-bearing service some Incoloy variants (and related nickel alloys) offer lifecycle advantages.

• Flue gas, furnace hardware: where oxidation resistance at elevated temperatures is required.

Why choose Incoloy instead of stainless? The alloying balance provides higher stability under chloride stress and elevated temperatures; while more costly up front, Incoloy often reduces life-cycle costs in aggressive service.

Sizes, standards and weight

Incoloy bolts are available to common fastener standards (ISO, DIN, ASTM) and in metric and imperial sizes. Supplier inventories typically stock M3 to M56 / 3/16" to 2" and custom larger studs. Below is a compact reference for typical hex-bolt weights (approximate mass per 100 pieces) used for logistic and shipping estimation — weights are representative for hex bolts with corresponding nut and plain washers where applicable (source: industry fastener weight charts scaled for alloy density equivalence). Always request supplier weight sheets for final shipping quotes.

Imperial equivalents and heavy hex / stud weights are available from supplier weight tables (weights above are aggregated from standard ISO/DIN bolt weight charts; Incoloy density differences vs. carbon steel are small but should be used to adjust shipping mass for large orders).

Supplier inventories commonly list sizes M3–M56 (metric) and 3/16"–2" (imperial) for Incoloy 825 and 800 fasteners.

Surface finishes, passivation and coatings

• Standard finishes: plain mill, passivated, bright (for special appearance). Passivation improves resistance to some corrosive environments and is recommended for critical process installations.

• Plating options: plating is unusual on Incoloy (the base alloy provides corrosion protection); where required, specialized coatings must be compatible with the substrate and service temperature.

• Marking & traceability: fasteners for critical service should be MTC traced to UNS number, heat number, and hardness and must conform to the relevant ASTM/EN specs.

Global 2025 price comparison: US / Europe / China

Prices for Incoloy (alloyed nickel products) are strongly influenced by nickel, molybdenum and copper commodity costs, alloy surcharges, order quantity, and finishing/heat-treatment. Below are indicative 2025 market ranges for procurement budgeting; treat them as starting points — request firm quotations for procurement.

What drives the spread? Small batch, certified fasteners (traceability, hardness tests, 3.1/3.2 MTCs) add cost. Western sources often include higher processing and labor costs; Chinese factory prices for raw material and finished parts can be substantially lower for bulk orders but confirm factory inspection and third-party test options.

Consejo práctico sobre contratación: For projects sensitive to lead time and certification, compare total landed cost (price + inspection + lead time + logistics) rather than raw per-kg quotes.

Manufacturing, heat treatment and standards

• Standards & UNS numbers: Incoloy 800 (UNS N08800), 800H/HT (N08810 / N08811), 825 (N08825). Common ASTM specifications for bars/fasteners and forgings vary; vendors typically supply material to ASTM/ASME or EN equivalents on request.

• Tratamiento térmico: For 800H/HT, solution annealing and controlled cooling deliver creep resistance; 825 is normally delivered solution annealed. For high-duty fasteners, the manufacturer will specify any post-form heat treatment.

• Pruebas: hardness, tensile, chemical analysis, and MTCs are routine for critical orders. Third-party inspection (TPI) is common for oil & gas or nuclear service.

Por qué elegir MWAlloys

MWAlloys is a specialist supplier of nickel-alloy fasteners and precision components. Our offering for Incoloy bolts includes:

• Factory direct (China) — 100% factory pricing on standard stock items and competitive quotations for OEM volumes.

• Disponibilidad de existencias — popular sizes in Incoloy 800 and 825 held in inventory for fast turnaround; expedited shipments for urgent projects.

• Control de calidad — material certificates (MTC), batch chemical analysis, and mechanical testing available on request; third-party inspection arranged for critical orders.

• Personalización — custom lengths, special head-forms, and matched nuts/washers produced to specification.

• Logística — experience exporting to the US, Europe, Middle East and Southeast Asia; assistance with packaging, export documentation, and trade compliance.

If you require sample evaluation or a formal quotation, MWAlloys can supply quantity-based pricing and lead-time commitments with photographic inspection reports and MTCs before shipment.

Preguntas frecuentes

1. Are Incoloy bolts magnetic?
   Typically Incoloy alloys (800/825 family) are essentially non-magnetic in the annealed condition because they are austenitic; some magnetic response can appear after cold work.

2. Can Incoloy bolts be used in seawater?
   Yes, Incoloy improves on many stainless steels in chloride environments, but selection must consider flow, oxygenation and temperature. For prolonged seawater exposure consult corrosion data for the specific grade.

3. How do Incoloy bolts compare in cost to 316L or duplex stainless?
   Incoloy is more expensive on a per-kg basis but may provide superior life-cycle value where chloride stress or elevated temperatures would degrade stainless steels.

4. Can I thread-roll Incoloy bolts?
   Yes; thread rolling is preferred where possible because it improves fatigue strength — but tooling and process parameters must be optimized for nickel alloys.

5. What torque values should I use for Incoloy bolts?
   Use torque tables derived from measured proof load and thread geometry; because Incoloy alloys can be softer than high-strength carbon steels, use manufacturer torque guidance and lubricants where necessary.

6. Are Incoloy bolts weldable?
   The alloys are weldable using appropriate filler metals and procedures, though weld repair of threaded fasteners is not recommended for load-bearing applications.

7. Do Incoloy fasteners require passivation?
   Passivation can improve resistance for some chemical services; consult process and supplier recommendations.

8. What certificates should I request?
   Request mill test certificates (EN10204 3.1 or 3.2), chemical and mechanical test reports, and any required NDT results for critical service.

9. How long is delivery from MWAlloys?
   For stocked sizes typical lead times are short (days to a few weeks); for larger or customized orders lead time depends on order size, heat treatment and inspection requirements — MWAlloys provides firm lead times with every quotation.

10. Can MWAlloys support large OEM volumes?
    Yes, we have factory capacity and QC procedures to serve large production runs with full traceability and inspection options.