Patriot Bolt machines Inconel heavy hex nuts in Alloy 625 and Alloy 718 from certified round bar, to match Inconel stud bolts in seawater, sour and high-temperature service. Alloy 625 (UNS N06625) is chosen for pitting and crevice corrosion resistance. Alloy 718 (UNS N07718) is age hardened for very high strength.
We make Inconel heavy hex nuts to ASME B18.2.2 dimensions or your drawing, in the alloy and specification on your purchase order. Every order ships with mill test reports traceable to the heat.
Inconel Heavy Hex Nuts at a Glance
- Alloys
- Inconel 625 (UNS N06625) · Inconel 718 (UNS N07718)
- 625 specs
- ASTM B446 bar · ASTM F467 (Ni 625)
- 718 specs
- ASTM B637 · AMS 5662 / 5663 · API 6A718
- Sour service
- NACE MR0175 / ISO 15156-3, within its limits
- Dimensions
- ASME B18.2.2 heavy hex, or to your drawing
Why Engineers Specify Inconel Heavy Hex Nuts
A corrosion-resistant stud is only as good as the nut on it. Nuts sit in the crevice at the flange face and hold pooled fluids, so a carbon steel or stainless nut on an Inconel stud can corrode first or set up galvanic attack. Matching the nut alloy to the stud avoids both problems.
- Inconel 625 nuts pair with 625 studs in seawater, subsea and acid service, where pitting and crevice resistance come first.
- Inconel 718 nuts pair with 718 studs where high preload, high temperature or oilfield sour service is the main concern.
- Heavy hex nuts are the standard style for flange stud bolting and give a larger bearing face than standard hex nuts.
Inconel Nut Specifications
ASTM A194 does not cover nickel alloys, so Inconel nuts are ordered by material specification and dimensional standard. ASTM F467 covers nonferrous nuts in Alloy 625. Alloy 718 nuts are ordered to the bar specification used for the matching stud.
| Alloy and specification | Condition | Strength |
|---|---|---|
| 625, ASTM F467 Ni 625 Grade 1 | Annealed | 65 ksi proof stress (heavy hex), 85 HRB min |
| 625, ASTM B446 Grade 1 bar | Annealed, to 4 in. | 120 ksi min tensile, 60 ksi min yield |
| 718, ASTM B637 / AMS 5663 bar | Solution treated and aged | 185 ksi min tensile, 150 ksi min yield |
| 718, API 6A718 (120K) | Solution treated and aged | 150 ksi min tensile, 120 ksi min yield, 32–40 HRC |
Order the nut in the same alloy and condition as the stud unless your design calls for something else. Put the specification on your purchase order.
Inconel 625 and 718 Chemical Composition
| Element | 625, weight % | 718, weight % |
|---|---|---|
| Nickel | 58.0 min | 50.0–55.0 |
| Chromium | 20.0–23.0 | 17.0–21.0 |
| Molybdenum | 8.0–10.0 | 2.80–3.30 |
| Niobium + tantalum | 3.15–4.15 | 4.75–5.50 |
| Titanium | 0.40 max | 0.65–1.15 |
| Aluminum | 0.40 max | 0.20–0.80 |
| Cobalt | 1.0 max | 1.00 max |
| Carbon | 0.10 max | 0.08 max |
| Iron | 5.0 max | Balance |
Typical limits for UNS N06625 and N07718. API 6A718 sets tighter limits on some elements. The mill test report for your heat is the controlling document.
Nut Styles
- Heavy hex nuts for flange stud bolting, per ASME B18.2.2.
- Other nut styles in Inconel to your drawing. See our Nuts page for the styles we make.
Nickel alloys can gall, especially nut against stud in the same alloy. Use a compatible thread lubricant or anti-seize.
Applications and Industries
- Subsea and offshore: Manifold, riser and seawater flange nuts. See Oil & Gas.
- Wellhead and high pressure: 718 nuts for high-preload valve and wellhead bolting.
- Chemical and power: Acid service and gas turbine bolting. See Petrochemical & Refining and Power Generation.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each Inconel order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification on your purchase order.
Matching studs: Inconel 625 stud bolts and Inconel 718 stud bolts.
Compare Inconel with other bolting grades in our Fastener Materials Matrix.
Inconel Heavy Hex Nuts FAQ
Should the nut be the same alloy as the stud?
Usually, yes. Matching the alloy avoids galvanic corrosion and keeps the joint corrosion resistant throughout. Follow your design or code if it specifies otherwise.
Is ASTM A194 used for Inconel nuts?
No. ASTM A194 covers carbon, alloy and stainless steel nuts. Inconel nuts are ordered to the alloy bar specification, ASTM F467 for Alloy 625, and a dimensional standard such as ASME B18.2.2.
Which is better for nuts, Inconel 625 or 718?
Choose the alloy that matches the stud. 718 is much stronger and suits high-preload and high-temperature joints. 625 is chosen for pitting and crevice corrosion resistance.
Do you make the matching studs?
Yes. We machine Inconel 625 and 718 stud bolts, so the whole joint can come from one source.
Request a Quote
Send us the alloy, nut style, thread size, 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 Inconel: Inconel 625 stud bolts · Inconel 718 stud bolts · Socket head cap screws · All nuts