Patriot Bolt machines Incoloy 825 stud bolts from certified ASTM B425 round bar for flanges 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.
We make Incoloy 825 studs to the specification on your purchase order or to your drawing, usually paired with Incoloy 825 nuts in the same joint. Every order ships with mill test reports traceable to the heat.
Incoloy 825 Stud Bolts at a Glance
- Also called
- Inconel 825 · Alloy 825 · UNS N08825 · W.Nr. 2.4858
- Material specs
- ASTM B425 / ASME SB425 bar · NACE MR0175 / ISO 15156-3
- Strength
- 85 ksi min tensile, 35 ksi min yield, annealed (ASTM B425)
- Service range
- Up to about 1000 °F
- Configurations
- Fully threaded, double-end and tap-end
Why Engineers Specify Incoloy 825 Stud Bolts
Stud bolts sit in the crevice between two flanges, where trapped fluids and deposits concentrate corrosion. B7 studs corrode, and 316 stainless studs can crack in hot chloride service. Incoloy 825 is built for that environment.
- Acid resistance. Nickel, molybdenum and copper resist sulfuric and phosphoric acids.
- Chloride stress-corrosion cracking. With 38–46% nickel, 825 resists the cracking that attacks 300-series stainless.
- Sour service. Alloy 825 is listed in NACE MR0175 / ISO 15156-3 for hydrogen sulfide environments.
- Stabilized. A titanium addition resists intergranular corrosion after heat exposure.
Incoloy 825 Stud Bolt Specifications
ASTM A193 does not cover Alloy 825, so 825 studs are ordered by material specification and drawing.
| Requirement | Standard |
|---|---|
| Bar material | ASTM B425 / ASME SB425 |
| Sour service | NACE MR0175 / ISO 15156-3 |
| Mechanical properties (annealed) | 85 ksi min tensile, 35 ksi min yield, 30% min elongation |
Annealed 825 is much weaker than B7. For high-preload joints, confirm the stud size and torque with your engineer.
Incoloy 825 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.
Stud Configurations
- Fully threaded studs, threaded end to end, for flange bolting where grip length varies.
- Double-end studs, threaded on both ends with an unthreaded center.
- Tap-end studs, with one end made to thread into a tapped hole.
Like most nickel alloys, 825 can gall. Use a compatible thread lubricant or anti-seize.
Applications and Industries
- Sour gas production: Wellhead, flowline and offshore flange studs. See Oil & Gas.
- Refining and petrochemical: Acid units, heat exchangers and process flanges. See Petrochemical & Refining.
- Chemical processing: Pickling, acid handling and pollution-control equipment.
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 specification on your purchase order.
Matching nuts: Incoloy 825 hex nuts.
Compare Incoloy 825 with other bolting grades in our Fastener Materials Matrix.
Incoloy 825 Stud Bolt FAQ
Is Inconel 825 the same as Incoloy 825?
Yes. The alloy is trademarked INCOLOY 825 but 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 hydrogen sulfide environments, within the limits that standard sets.
How does 825 compare with Inconel 625 studs?
Alloy 625 is stronger and has more molybdenum for severe pitting service. Alloy 825 is often chosen for sulfuric and phosphoric acid service and is usually more economical.
Do you make the nuts too?
Yes. We machine Incoloy 825 hex nuts, so the whole joint can be ordered from one source.
Request a Quote
Send us the stud configuration, diameter, length, thread, specification and quantity, 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: Hex nuts · Socket head cap screws · Hex head cap screws · All stud bolts