Unifit Fastener is an ISO 9001:2013, 14001:2015 and 22000:2018 certified manufacturer and global exporter of Incoloy 825 Fasteners that are designed to operate in the most severe corrosive and high temperature applications. Industries using our ASTM B425 / ASME SB425 compliant fasteners include oil & gas, chemical processing, marine engineering and power generation.
Austenitic nickel-iron-chromium alloy with unique stabilizing elements of titanium, copper and molybdenum, which ensures high corrosion resistance in reducing and oxidizing acids, especially sulfuric acid and phosphoric acid. Engineers and procurement staff in environments where corrosion and chemical exposure are a concern need to make a decision regarding the proper fastener material that will provide them safety and performance.
Incoloy 825 fasteners are produced in metric (m3 to m100) and imperial (3/8" to 4") sizes, and can be hex bolts, stud bolts, threaded rod, hex nuts, flat washers, socket cap screws and more. All the raw material is certified mill, prime grade and is heat treated to solution-annealed condition, with full MTC EN 10204/3.1 testing of each batch. Nickel alloy fastening components supplier Unifit Fastener provides competitive price, fast delivery, and export to 40+ countries, so it is a reliable supplier for you in the long run.
Request a QuoteTable of Content
- Incoloy 825 Fasteners Specification
- Chemical Composition
- Mechanical Properties
- Equivalent Grades
- Bolts Torque Chart
- Size & Dimensional Guide
- Corrosive Environments
- Applications & Industries
- Surface Finish Options
- Quality Assurance & Testing
- Comparable Alloys
- Fastener Size Chart
- Price List
- Related Products
- Frequently Asked Questions
Incoloy 825 Fasteners Specification
All Unifit Fastener Incoloy 825 fasteners are manufactured and tested in strict compliance with the following technical specifications:
| Parameter | Details |
| Material Grade | Incoloy 825 / Alloy 825 |
| UNS Designation | UNS N08825 |
| Werkstoff Nr. | DIN 2.4858 (Incoloy 825 — NiCr21Mo) |
| Primary Standard | ASTM B425 / ASME SB425 |
| Other Standards | IS, ANSI, DIN, ISO, JIS, GB, BS, UNI and all International Standards |
| Bolt / Screw Size | M3 to M100 | 3/16" to 4" | Custom Sizes Available |
| Nut Size | M3 to M56 | 3/16" to 2" | Custom Sizes Available |
| Washer Size | M3 to M56 | 3/16" to 2" | Custom Sizes Available |
| Length | 3 mm to 200 mm | Custom lengths on request |
| Threads | UNF, BSW, BSF, METRIC (UNC, UNEF, NPT, NPTF, UNS) |
| Head Type (Bolts) | Hex, Pan, Flat, Round, Oval, Truss, Square, Flange |
| Head Drive (Screws) | Phillips, Slotted, Phillips/Slot, Six-Lobe, Allen |
| Manufacturing Method | Cold Forging (M2–M24), Hot Forging (M24–M100), CNC Machining for custom |
| Manufacturing Standard | USA: ISO 4033, ISO 4032 | American: ASME B18.2.2, ASME B18.2.1 | Australia: NPT, UNS, UNC, UNEF, UNF | Germany: DIN 931, DIN 933, DIN 970 |
| Test Certificate | As per EN 10204 / 3.1 Manufacturer Test Certificate | PED 97/23/EC Certified |
| Packaging | Carton Box, Wooden Cases, Wooden Pallet, Bulk as per customer request |
| Place of Origin | India (Mumbai) |
| Delivery Time | Standard: 7–15 days | Custom: 2–4 weeks |
Chemical Composition of Incoloy 825 Fasteners
The precise chemical composition of Alloy 825 makes it one of the most versatile corrosion-resistant alloys available for fastener applications:
| Ni (%) | Cr (%) | Fe (%) | Mo (%) | Cu (%) | Ti (%) | C (%) | Mn (%) | Si (%) |
| 38.0 – 46.0 | 19.5 – 23.5 | 22.0 min | 2.50 – 3.50 | 1.50 – 3.00 | 0.60 – 1.20 | 0.05 max | 1.00 max | 0.50 max |
Additional elements: Sulfur (S) max 0.03%, Aluminum (Al) max 0.20%
Mechanical Properties of Incoloy 825 Fasteners
| Property | Tensile Strength | Yield Strength (0.2% offset) | Elongation (%) | Density |
| Incoloy 825 | 586 MPa (85,000 psi) min | 241 MPa (35,000 psi) min | 30% min (in 50 mm) | 8.14 g/cm³ |
| Melting Point | Temperature Range | Specific Heat (0–100°C) | Heat Treatment |
| 1400°C (2550°F) | Cryogenic to 982°C (2200°F) | 444 J/kg·K | Solution Annealed at 940°C, Water Quenched |
Incoloy 825 Equivalent Grades — International Standards
| Grade | UNS (USA) | WNR (EU) | JIS (Japan) | BS (UK) | AFNOR (France) | GOST (Russia) |
| Incoloy 825 | N08825 | 2.4858 | NCF 825 | NA 16 | NFE30C20DUM | ЭП703 / XH38BT |
Incoloy 825 Bolts Torque Chart
Proper torque values are essential for joint integrity. The following are recommended torque values for Incoloy 825 hex bolts:
| Nominal Diameter (in) | Thread Count | Torque (ft-lb) Lubricated | Torque (ft-lb) Dry |
| 1/4" | 20–28 | 5.8 – 6.6 | 7.8 – 8.9 |
| 3/8" | 16–24 | 21.2 – 23.9 | 28.2 – 32.0 |
| 1/2" | 13–20 | 51.6 – 58.2 | 68.8 – 77.6 |
| 5/8" | 11–18 | 102.8 – 116.4 | 137.0 – 155.2 |
| 3/4" | 10–16 | 183 – 204 | 244 – 271 |
| 1" | 8–14 | 441 – 495 | 588 – 659 |
| 1-1/4" | 7–12 | 767 – 849 | 1024 – 1133 |
Incoloy 825 Fasteners Size & Dimensional Reference Guide
Incoloy 825 Hex Bolt Dimensions
| Bolt Size (Inch) | Nominal Diameter | Across Flats (F) | Head Height (H) | Fillet Radius (R) | Thread Length ≤ 6 in | Thread Length > 6 in |
| 1/4" | 0.25 | 7/16" | 11/64" | 0.03–0.01 | 0.75 | 1.00 |
| 5/16" | 0.3125 | 1/2" | 7/32" | 0.03–0.01 | 0.875 | 1.125 |
| 3/8" | 0.375 | 9/16" | 1/4" | 0.03–0.01 | 1.00 | 1.25 |
| 1/2" | 0.50 | 3/4" | 11/32" | 0.03–0.01 | 1.25 | 1.50 |
| 5/8" | 0.625 | 15/16" | 27/64" | 0.06–0.02 | 1.50 | 1.75 |
| 3/4" | 0.75 | 1-1/8" | 1/2" | 0.06–0.02 | 1.75 | 2.00 |
| 1" | 1.00 | 1-1/2" | 43/64" | 0.09–0.03 | 2.25 | 2.50 |
| 1-1/4" | 1.25 | 1-7/8" | 27/32" | 0.09–0.03 | 2.75 | 3.00 |
| 1-1/2" | 1.50 | 2-1/4" | 1" | 0.09–0.03 | 3.25 | 3.50 |
| 2" | 2.00 | 3" | 1-11/32" | 0.12–0.04 | 4.25 | 4.50 |
Available sizes extend up to 4 inches in diameter.
Incoloy 825 Stud Bolt Dimensions
| Stud Size | Diameter D (Nominal) | Diameter Min. | Diameter Max. | Tap End Thread Length | Nut End (L≤10) | Nut End (10<L≤16) | Nut End (L>16) |
| 1/4" | 0.375 | 0.350 | 0.400 | 0.100 | 0.750 | 1.000 | 1.500 |
| 3/8" | 0.563 | 0.532 | 0.594 | 0.125 | 1.000 | 1.250 | 1.750 |
| 1/2" | 0.750 | 0.708 | 0.792 | 0.154 | 1.250 | 1.500 | 2.000 |
| 5/8" | 0.938 | 0.892 | 0.983 | 0.182 | 1.500 | 1.750 | 2.250 |
| 3/4" | 1.125 | 1.075 | 1.175 | 0.200 | 1.750 | 2.000 | 2.500 |
| 1" | 1.500 | 1.438 | 1.562 | 0.250 | 2.250 | 2.500 | 3.000 |
| 1-1/4" | 1.875 | 1.813 | 1.938 | 0.286 | 2.750 | 3.000 | 3.500 |
| 1-1/2" | 2.250 | 2.188 | 2.313 | 0.333 | 3.250 | 3.500 | 4.000 |
| 2" | 3.000 | 2.925 | 3.075 | 0.444 | 4.250 | 4.500 | 5.000 |
| 3" | 4.500 | 4.425 | 4.575 | 0.500 | — | 6.500 | 7.000 |
Incoloy 825 Heavy Hex Nut Dimensions
| Nominal Size | Thread Diameter | Width Across Flats | Width Across Corners | Nut Thickness | Jam Nut Thickness |
| 1/4" | 0.250 | 1/2" | 0.556–0.577 | 15/64" | 11/64" |
| 3/8" | 0.375 | 11/16" | 0.763–0.794 | 23/64" | 15/64" |
| 1/2" | 0.500 | 7/8" | 0.969–1.010 | 31/64" | 19/64" |
| 5/8" | 0.625 | 1-1/16" | 1.175–1.227 | 39/64" | 23/64" |
| 3/4" | 0.750 | 1-1/4" | 1.382–1.443 | 47/64" | 27/64" |
| 1" | 1.000 | 1-5/8" | 1.796–1.876 | 63/64" | 35/64" |
| 1-1/4" | 1.250 | 2" | 2.209–2.309 | 1-7/32" | 23/32" |
| 1-1/2" | 1.500 | 2-3/8" | 2.622–2.742 | 1-15/32" | 27/32" |
| 2" | 2.000 | 3-1/8" | 3.449–3.608 | 1-31/32" | 1-3/32" |
| 3" | 3.000 | 4-5/8" | 5.102–5.340 | 2-61/64" | 1-45/64" |
Incoloy 825 Washer Dimensions
| Nominal ID (mm) | Actual ID Range (mm) | Outside Diameter (mm) | Standard Thickness (mm) | Extra Thick Washer (mm) | Minimum Clipped Width (mm) |
| 12 | 14.0 – 14.4 | 25.7 – 27 | 3.1 – 4.6 | 8 – 10 | 10.5 |
| 16 | 18.0 – 18.4 | 32.4 – 34 | 3.1 – 4.6 | 8 – 10 | 14 |
| 20 | 22.0 – 22.5 | 40.4 – 42 | 3.1 – 4.6 | 8 – 10 | 17.5 |
| 24 | 26.0 – 26.5 | 48.4 – 50 | 3.4 – 4.6 | 8 – 10 | 21 |
| 30 | 33.0 – 33.6 | 58.1 – 60 | 3.4 – 4.6 | 8 – 10 | 26.2 |
| 42 | 45.0 – 45.6 | 81.8 – 84 | 4.6 – 7.2 | 8 – 10 | 36.7 |
| 56 | 62.0 – 62.7 | 104.8 – 107 | 6.1 – 8.7 | 8 – 10 | 49 |
| 72 | 78.0 – 78.7 | 127.5 – 130 | 6.1 – 8.7 | 8 – 10 | 63 |
| 90 | 96.0 – 96.9 | 156.5 – 159 | 6.1 – 8.7 | 8 – 10 | 78.7 |
| 100 | 107.0 – 107.9 | 173.5 – 176 | 6.1 – 8.7 | 8 – 10 | 87.5 |
Corrosive Environments Where Incoloy 825 Fasteners Excel
One of the defining characteristics of Alloy 825 is its exceptional resistance to a wide range of corrosive media. Unifit Fastener's Incoloy 825 fasteners are the go-to choice for:
| Corrosive Medium | Performance | Corrosive Medium | Performance |
| Sulfuric Acid (H2SO4) | Excellent resistance | Sea Water / Brine | Excellent resistance |
| Phosphoric Acid (H3PO4) | Outstanding performance | Sulfur-containing Flue Gases | Good resistance |
| Sour Gas / H2S Wells | Excellent NACE compliance | Stress Corrosion Cracking | Highly resistant |
| Hydrochloric Acid | Moderate resistance | Intergranular Corrosion | Resistant (Ti stabilized) |
Applications & Industries Served
Incoloy 825 fasteners from Unifit Fastener are engineered for critical service in:
| Upstream / Midstream | Chemical & Process | Marine & Power |
| Oil & Gas Exploration Sour Gas Processing Subsea Pipelines & Manifolds | Chemical Reactors & Vessels Phosphoric Acid Plants Sulfuric Acid Production | Marine Engineering Offshore Platforms Seawater Desalination |
| Petrochemical Refineries Nuclear Fuel Reprocessing Acid Production Plants | Pollution Control Equipment Pulp & Paper Industry Pharmaceutical Equipment | Power Generation Heat Exchangers Condensers |
All Incoloy 825 fasteners supplied by Unifit Fastener comply with NACE MR0175 / ISO 15156 requirements for sour-service environments containing H2S.
Surface Finish Options for Incoloy 825 Fasteners
| Mill Finish | Polished Finish | Passivated Finish | Brushed Finish | Electroless Nickel |
| As-manufactured surface – industry standard for most applications | Bright surface for food-grade, pharmaceutical, and cosmetic applications | Chemically treated oxide layer for enhanced corrosion protection | Satin/matte texture for reduced reflectivity & improved aesthetics | Zinc-nickel coated or electro-cadmium plated for additional protection |
Quality Assurance & Testing at Unifit Fastener
Every Incoloy 825 fastener manufactured at Unifit undergoes a rigorous multi-stage quality protocol before shipment:
- Chemical Analysis: Spectrographic (OES) verification of all alloying elements against ASTM B425 requirements
- Mechanical Testing: Tensile strength, yield strength, elongation, and hardness (Rockwell B / Brinell) per ASTM standards
- Dimensional Inspection: Full dimensional check against DIN, ASME B18.2.1, ASME B18.2.2, and customer drawings
- 100% Radiography Test Report (RTR) available for critical applications
- Hydrostatic / Impact Testing available on request
- Third-Party Inspection (SGS, BV, TUV, Lloyds, DNV) coordinated on request
- MTC EN 10204/3.1 issued for all orders; 2.2 certificates also available
Incoloy 825 vs Comparable Alloys Performance Comparison
| Property | Incoloy 825 | Inconel 625 | Hastelloy C276 | SS 316L |
| UNS No. | N08825 | N06625 | N10276 | S31603 |
| Tensile Strength (MPa) | 586 | 860 | 790 | 485 |
| H2SO4 Resistance | Excellent | Good | Outstanding | Poor |
| H3PO4 Resistance | Outstanding | Good | Good | Moderate |
| Seawater Resistance | Excellent | Excellent | Excellent | Moderate |
| Max. Service Temp. | 982°C | 980°C | 816°C | 870°C |
| Relative Cost | Medium | High | Very High | Low |
| Best for | Acid processing, marine, oil & gas | Aerospace, extreme conditions | Chloride/reducing acids | General purpose |
Incoloy 825 max. service temp. 982C refers to the oxidation resistance limit in air. For aqueous corrosion service, the practical maximum is approximately 550C.
Incoloy 825 Fastener Size Chart
Ready Stock Sizes — Metric (MM Threads as per IS 1363/67)
Approximate weight in KG per 100 nos — Hex Bolts (selected sizes):
| Length (mm) | M5 | M6 | M8 | M10 | M12 | M16 | M20 | M24 |
| 20 | 0.598 | 0.812 | 1.711 | 3.411 | 4.892 | – | – | – |
| 30 | 0.737 | 1.010 | 2.070 | 3.912 | 5.574 | 10.707 | – | – |
| 50 | 1.030 | 1.450 | 2.870 | 5.155 | 7.299 | 13.624 | 22.72 | – |
| 75 | – | 2.000 | 3.873 | 6.702 | 9.506 | 17.606 | 29.0 | – |
| 100 | – | – | 4.873 | 8.251 | 11.820 | 21.459 | 35.71 | – |
Incoloy 825 Fasteners Price List
| Fastener Type | Size Range | Approx. Price (USD) | Approx. Price (INR) |
| Incoloy 825 Hex Bolts | M6 to M24 | $1.50 – $45 per piece | ₹125 – ₹3,800 per piece |
| Incoloy 825 Stud Bolts | M8 to M64 | $5 – $250 per piece | ₹420 – ₹21,000 per piece |
| Incoloy 825 Hex Nuts | M6 to M64 | $0.50 – $40 per piece | ₹40 – ₹3,350 per piece |
| Incoloy 825 Washers | M6 to M100 | $0.20 – $15 per piece | ₹15 – ₹1,250 per piece |
| Incoloy 825 Threaded Rods | M6 to M100 | $20 – $500 per meter | ₹1,700 – ₹42,000 per meter |
| Incoloy 825 U-Bolts | Custom Sizes | $10 – $150 per piece | ₹850 – ₹12,500 per piece |
| Incoloy 825 Anchor Bolts | M12 to M72 | $15 – $300 per piece | ₹1,250 – ₹25,000 per piece |
Note: Incoloy 825 fastener prices depend on diameter, length, thread type, manufacturing method, quantity ordered, raw material costs, and project specifications. Contact us for the latest Incoloy 825 fasteners price per kg, bulk order pricing, and export quotations.
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Frequently Asked Questions (FAQs)
Incoloy 825 (UNS N08825) is an austenitic nickel-iron-chromium alloy containing molybdenum, copper, and titanium. It offers outstanding resistance to corrosion — especially in sulfuric acid, phosphoric acid, seawater, and sour gas environments — along with high tensile strength and good creep resistance up to 982°C. These properties make it ideal for critical fastener applications in chemical processing, oil & gas, and marine industries.
The minimum tensile strength of ASTM B425 UNS N08825 Incoloy 825 hex bolts is 586 MPa (approximately 85,000 psi). The yield strength (0.2% offset) is a minimum of 241 MPa (35,000 psi), with a minimum elongation of 30%.
The melting point of Incoloy 825 (UNS N08825) fasteners is approximately 1400°C (2550°F). The alloy has a continuous service temperature range from cryogenic up to 982°C (2200°F).
The density of Incoloy 825 (Alloy 825) is 8.14 g/cm³ (0.294 lbs/in³). This is consistent across bolts, nuts, washers, and threaded rods manufactured from this alloy.
The DIN/European Werkstoff equivalent of Incoloy 825 is WNR 2.4858. It is also listed as EURONORM NiCr21Mo, JIS NCF 825, AFNOR NFE30C20DUM, and GOST ЭП703 in respective national standards.
While both are nickel-iron-chromium alloys, Incoloy 825 contains additional molybdenum (2.5–3.5%), copper (1.5–3%), and titanium, which gives it significantly superior resistance to reducing acid environments (e.g., sulfuric and phosphoric acids) compared to Incoloy 800. Incoloy 800 is better suited for high-temperature oxidizing environments (up to 1100°C), whereas 825 excels in aqueous corrosion service.