Patriot Bolt machines Incoloy 825 hex nuts and heavy hex nuts from certified ASTM B425 round bar for bolting exposed to sour gas, acids and chlorides. Incoloy 825, often listed as Inconel 825 or Alloy 825 and designated UNS N08825, is a nickel-iron-chromium alloy with molybdenum and copper. It resists sulfuric and phosphoric acids, pitting, crevice corrosion and chloride stress-corrosion cracking.
We make Incoloy 825 nuts to ASME B18.2.2 dimensions or to your drawing, usually to match Incoloy 825 stud bolts in the same joint. Every order ships with mill test reports traceable to the heat.
Incoloy 825 Hex Nuts at a Glance
- Also called
- Inconel 825 · Alloy 825 · UNS N08825 · W.Nr. 2.4858
- Material specs
- ASTM B425 / ASME SB425 bar · ASTM B564 forgings · NACE MR0175 / ISO 15156-3
- Strength
- 85 ksi min tensile, 35 ksi min yield, annealed (ASTM B425)
- Service range
- Up to about 1000 °F
- Dimensions
- ASME B18.2.2 hex and heavy hex, ASME B1.1 Class 2B threads, or to your drawing
- Styles
- Heavy hex, finished hex, jam, hex flange, coupling and cap nuts
Why Engineers Specify Incoloy 825 Nuts
Nuts often fail first in corrosive service. They have crevices at the bearing face and threads, they sit in pooled fluids, and they get overlooked at inspection. Incoloy 825 was developed for exactly these conditions.
- Acid resistance. Its nickel, molybdenum and copper resist sulfuric and phosphoric acids in both oxidizing and reducing conditions.
- Resistance to chloride stress-corrosion cracking. With 38–46% nickel, 825 resists the chloride cracking that attacks 300-series stainless nuts.
- Sour service. Alloy 825 is listed in NACE MR0175 / ISO 15156-3 for use in hydrogen sulfide environments.
- Stabilized against sensitization. A titanium addition resists intergranular corrosion after exposure to heat.
Incoloy 825 Specifications
ASTM A194 does not cover Alloy 825. Incoloy 825 nuts are therefore ordered by material and dimensional standard, or to a customer drawing.
| Requirement | Standard |
|---|---|
| Bar material | ASTM B425 / ASME SB425 |
| Forgings (large nuts) | ASTM B564 / ASME SB564 |
| Sour service | NACE MR0175 / ISO 15156-3 |
| Nut dimensions | ASME B18.2.2 (hex, heavy hex, jam) |
| Threads | ASME B1.1 UNC / 8-UN, Class 2B |
| Mechanical properties (annealed) | 85 ksi min tensile, 35 ksi min yield, 30% min elongation |
Annealed 825 is not as strong as A194 Grade 2H steel. For high-preload joints, confirm your stud and nut combination with your engineer.
Incoloy 825 (UNS N08825) Chemical Composition
| Element | Weight % |
|---|---|
| Nickel | 38.0–46.0 |
| Iron | 22.0 min |
| Chromium | 19.5–23.5 |
| Molybdenum | 2.5–3.5 |
| Copper | 1.5–3.0 |
| Titanium | 0.6–1.2 |
| Aluminum | 0.2 max |
| Carbon | 0.05 max |
| Manganese | 1.0 max |
| Silicon | 0.5 max |
| Sulfur | 0.03 max |
These are the ASTM B425 limits. The mill test report for your heat is the controlling document.
Nut Styles and Threads
- Heavy hex nuts for stud bolts in ASME B16.5 and API flanges.
- Finished hex and jam nuts for equipment and lighter-duty bolting.
- Hex flange, coupling and cap nuts made to your drawing.
- Threads: UNC and 8-UN per ASME B1.1, Class 2B.
Like most nickel alloys, 825 can gall. Use a compatible thread lubricant or anti-seize, and avoid over-tightening during assembly.
Applications and Industries
- Sour gas and oil production: Wellhead, flowline and offshore bolting in hydrogen sulfide and chloride service. See Oil & Gas.
- Petrochemical and refining: Acid units, heat exchangers and process piping flanges. See Petrochemical & Refining.
- Chemical processing: Sulfuric and phosphoric acid plants, pickling lines and scrubbers.
- Power and pollution control: Flue-gas desulfurization and other wet, acidic environments. See Power Generation.
- Marine and offshore: Seawater-exposed equipment where stainless nuts are prone to pitting.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each Incoloy 825 order includes mill test reports traceable to the heat, along with a certificate of conformance to the specifications on your purchase order.
Compare Incoloy 825 with Inconel 625, Hastelloy C-276 and other nickel alloys in our Fastener Materials Matrix.
Incoloy 825 Hex Nut FAQ
Is Inconel 825 the same as Incoloy 825?
Yes. The alloy is trademarked as INCOLOY 825, but it is widely called Inconel 825 or Alloy 825. All three names refer to UNS N08825.
Is Incoloy 825 approved for sour service?
Alloy 825 is listed in NACE MR0175 / ISO 15156-3 for use in hydrogen sulfide environments, within the limits that standard sets.
What studs should I use with Incoloy 825 nuts?
Incoloy 825 nuts are usually paired with Incoloy 825 stud bolts so the whole joint has the same corrosion resistance. We machine both.
How is Incoloy 825 different from Inconel 625?
Alloy 625 is stronger and has higher molybdenum for severe pitting service. Alloy 825 is often chosen for sulfuric and phosphoric acid environments and is usually more economical.
Can you make Incoloy 825 nuts to my drawing?
Yes. We machine nuts from certified bar to ASME B18.2.2 dimensions or to your drawing.
Request a Quote
Send us the nut style, size, thread, quantity and any NACE or customer specification, or upload your drawing. Our team will confirm the material and lead time. Call (281) 581-0176 or request a quote.
Also in Incoloy 825: Stud bolts · Socket head cap screws · Hex head cap screws · All nuts