| Standard | ASTM B446 (Alloy 625) / ASTM B637 (Alloy 718) / ASTM F468 where applicable / ASME B18.31.2 or customer · OEM drawing |
|---|---|
| Material | Alloy 625 / UNS N06625 and Alloy 718 / UNS N07718 nickel alloys |
| Strength Grade | Alloy 625 / Alloy 718 |
| Size Range | M8-M48 / 3/8"-2" |
| Surface Treatment | Machined / Pickled / Passivated / Project Specified |
Product Description
This page combines Inconel 625 and Inconel 718 stud bolts under one procurement route. Alloy 625 / UNS N06625 is a nickel-chromium-molybdenum-niobium alloy commonly selected for chloride, seawater, offshore and aggressive chemical-process corrosion resistance.
Alloy 718 / UNS N07718 is a precipitation-hardening nickel-chromium alloy selected for high mechanical strength, fatigue resistance and strength retention at elevated temperature in turbines, power equipment, oilfield assemblies and qualified OEM systems. Its properties depend strongly on solution treatment, aging route, section size and the specified material condition.
Alloy 625 and Alloy 718 are not automatic substitutes. ASTM B446 and ASTM B637 primarily govern material, not the complete finished-stud geometry or aerospace qualification. The order must add ASTM F468 where applicable, ASME B18.31.2 or a customer/OEM drawing, thread and end requirements, inspection, NDT and any NACE or ISO sour-service route.
| Alloy options | Alloy 625 / UNS N06625; Alloy 718 / UNS N07718 |
|---|---|
| Alloy 625 material reference | ASTM B446; commonly selected where corrosion resistance governs |
| Alloy 718 material reference | ASTM B637 with condition and heat-treatment route stated; commonly selected where strength and temperature govern |
| Fastener reference | ASTM F468 where applicable; project, aerospace or OEM specification may supersede it |
| Dimensions | ASME B18.31.2 or customer/OEM drawing; UNC, UNJF, 8UN or metric as specified |
| Size range | M8-M48 / 3/8 in-2 in; other drawing sizes reviewed by project |
| Surface condition | Machined, pickled, passivated or project specified; coating and lubricant qualified for service |
| Inspection | MTC, PMI, heat treatment, mechanical tests, dimensions, specified NDT and heat/lot traceability |
| Parameter | M4 | M5 | M6 | M7 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 | M48 | M52 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P | 0.7 | 0.8 | 1 | 1 | 1|1.25 | 1.25|1.5 | 1.25|1.5|1.75 | 1.5|2 | 1.5|2 | 1.5|2.5 | 1.5|2.5 | 1.5|2.5 | 2|3 | 2|3 | 2|3.5 | 2|3.5 | 3|4 | 3|4 | 3|4.5 | 3|4.5 | 3|5 | 3|5 |
| b1 | 5 | 6.5 | 7.5 | 9 | 10 | 12 | 15 | 18 | 20 | 22 | 25 | 28 | 30 | 35 | 38 | 42 | 45 | 50 | 52 | 58 | 60 | 65 |
| ds/max | 4 | 5 | 6 | 7 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 | 48 | 52 |
Engineering references
Selection
Alloy 625 serves seawater and corrosive process joints; Alloy 718 may serve specialized high-load equipment. Corrosion and sour-service approval remain separate from tensile strength.
Oil and gas fastenersFor Alloy 625, review crevices, stagnant water, galvanic area ratio, cathodic protection and the mating flange or structure.
Marine fastenersAlloy 718 supports highly loaded and elevated-temperature assemblies when the equipment specification defines material condition and acceptance.
Power generation fastenersA generic Alloy 718 or ASTM F468 declaration is not equivalent to an aerospace-qualified drawing. Follow OEM material, process, thread, NDT and source-approval requirements.
Aerospace fastenersChoose Alloy 625 for a corrosion-led route or Alloy 718 for a strength-and-temperature-led route after reviewing medium, load, condition and qualification requirements.
Fastener material selection guideAssembly
Manufacturing
FAQ
Alloy 625 is commonly selected for chloride and chemical corrosion resistance. Alloy 718 is commonly selected for higher strength, fatigue resistance and elevated-temperature strength retention.
No. Their composition, strengthening route, heat treatment, mechanical properties, material specifications and qualification requirements differ. The purchase order must state the required alloy.
No. They principally govern Alloy 625 and Alloy 718 material. Add the applicable fastener specification, dimensional standard or customer/OEM drawing.
Not automatically. Aerospace hardware may require an OEM drawing, aerospace material specification, approved source, special manufacturing processes, NDT and lot qualification.
State alloy, UNS number, material condition and heat treatment, ASTM or OEM specification, diameter, length, thread, drawing, medium, load, temperature, companion hardware, PMI, NDT, certificates, quantity and traceability.
Send the alloy, material condition, specification, drawing, diameter, length, thread, service medium, load and temperature, companion hardware, inspection and traceability requirements.
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