Inconel® X-750 (UNS N07750)
The spring and fastener superalloy: age hardened to 170 ksi, holds its strength to 1300 °F and stays tough at cryogenic temperature — for turbine bolting, springs and nuclear and rocket hardware.
What Inconel X-750 is.
Inconel X-750 is a nickel-chromium alloy hardened by gamma-prime precipitates of titanium, aluminium and niobium. It keeps useful strength to about 1300 °F, resists oxidation and relaxation, and is non-magnetic, which made it the standard material for high-temperature springs, turbine and nuclear fasteners and rocket-engine hardware. ASTM B637 defines three heat-treatment types with different strength and creep balances.
We machine X-750 studs, bolts, nuts and components from certified B637 bar, supplied solution treated for machining and aged to the type ordered, with PMI on every lot.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.08 |
| Manganese | Mn | — | 1.00 |
| Silicon | Si | — | 0.50 |
| Sulfur | S | — | 0.01 |
| Chromium | Cr | 14.00 | 17.00 |
| Cobalt | Co | — | 1.00 |
| Niobium + tantalum | Nb+Ta | 0.70 | 1.20 |
| Titanium | Ti | 2.25 | 2.75 |
| Aluminium | Al | 0.40 | 1.00 |
| Iron | Fe | 5.00 | 9.00 |
| Copper | Cu | — | 0.50 |
| Nickel | Ni | 70.00 | — |
Values per ASTM B637-16 Tables 1 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Condition and nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| Type 1 — solution 2100 °F + stabilize + age | 140 | 90 | 8 | — | 262 HBW min |
| Type 2 — solution 1800 °F + age, under 2½ in. | 170 | 115 | 18 | 18 | 302–363 HBW |
| Type 2 — 2½ to 4 in. | 170 | 115 | 15 | 15 | 302–363 HBW |
| Type 3 — anneal 2000 °F + age | 160 (185 max) | 100 (130 max) | 20 | 20 | 267–363 HBW / 27–40 HRC |
Values per ASTM B637-16 Tables 1 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Specifications that apply.
How Inconel X-750 ships from Houston.
- Studs and stud bolts
- Hex and heavy hex bolts
- Nuts and washers
- Socket head cap screws
- Machined components from certified bar
Inconel X-750 fasteners we make.
Every item is manufactured to your drawing or standard in Inconel X-750, imperial or metric, with an EN 10204 3.1 certificate.
What is Inconel X-750?
X-750 was the first widely used age-hardenable nickel superalloy. Titanium and aluminium form gamma-prime particles on ageing that block dislocation movement, so the alloy is strong and creep resistant to about 1300 °F, and its nickel-chromium matrix resists oxidation and corrosion in steam, water and combustion gas. It is non-magnetic and remains ductile at liquid-hydrogen temperature, which is why it appears in both reactors and rockets.
X-750 or 718?
718 is stronger to about 1200 °F, easier to weld and less prone to strain-age cracking, and has largely replaced X-750 in new turbine designs. X-750 keeps its place for springs, for relaxation-resistant bolting to 1300 °F, and wherever an existing drawing or reactor specification names it.
Testing, certification and marking
- Tensile and hardness tested per heat-treat lot
- Type 1: ASTM B637 Table 4 requires a stress-rupture test per lot (1350 °F, 45 ksi, 100 h minimum)
- Grade or alloy symbol and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- PMI verification standard on nickel alloys
Inconel 718 (UNS N07718)
The premier high-strength nickel superalloy — 185 ksi tensile and 150 ksi yield from cryogenic temperatures to 1200 °F, with corrosion and sour-gas resistance to match.
ASTM B166 barInconel 600 (UNS N06600)
The general-purpose nickel-chromium alloy — oxidation resistant to 2000 °F, immune to chloride stress-corrosion cracking, for furnace, heat-treat and nuclear hardware.
ASTM A453 / ASME SA-453ASTM A453 Grade 660 (A-286)
A-286 bolting for the hottest joints — 130 ksi at room temperature and rated by stress-rupture at 1200 °F, for gas and steam turbines, exhaust and high-temperature process equipment.