Inconel 718 Tube Sheet
The highest-strength alloy in this range by a wide margin — aged tensile strength above 1200 MPa, roughly 1.5x Inconel 625, achieved through a niobium-driven precipitation-hardening mechanism. A genuine specialist grade, not a default upgrade.
Chemical Composition
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | 50.0 | 55.0 |
| Chromium (Cr) | 17.0 | 21.0 |
| Niobium + Tantalum (Nb+Ta) | 4.75 | 5.50 |
| Molybdenum (Mo) | 2.80 | 3.30 |
| Titanium (Ti) | 0.65 | 1.15 |
Mechanical Properties (Aged)
| Property | Typical Value |
|---|---|
| Tensile Strength | 1240 MPa min |
| Yield Strength (0.2% offset) | 1035 MPa min |
| Elongation | 12% min |
| Max. Continuous Service Temp. | ~650°C |
Equivalent Grades
| Standard | Designation |
|---|---|
| ASTM / UNS | N07718 |
| EN / DIN | 2.4668 |
| Trade Name | Inconel® 718 (Special Metals) |
A Genuine Specialist, Not a Default Upgrade
Purchasing Specifications by Form
For Inconel 718 / UNS N07718, plate/sheet/strip purchasing leads with ASTM B670. Bar and forging-related product forms are covered under ASTM B637. ASTM B564 is not claimed for N07718 on this page.
| Element | Reference |
|---|---|
| Common name | Inconel 718 |
| UNS | N07718 |
| Plate / sheet / strip | ASTM B670 (SB-670 where applicable) |
| Bar / forging path | ASTM B637 (SB-637 where applicable) |
| ASTM B564 | Not claimed for N07718 |
Do not merge B670 and B637 into one generic “ASTM specification” statement. Keep aging / heat-treat sequence notes on the manufacturing section for strength-critical service.
ASME SB-* may apply by form and Code context. Listing references is not a certification claim.
| Specification | Product form / role | How to read it for tube sheets |
|---|---|---|
| ASTM B670 / SB-670 | Plate, sheet and strip | Lead plate path when the blank is machined from flat product |
| ASTM B637 / SB-637 | Precipitation-hardenable bar / forging / forging-stock path | Use when bar or forging forms are specified — not the same scope as B670 plate |
| ASTM B564 | Not asserted for N07718 | Do not associate B564 with Inconel 718 / N07718 based on this page |
Useful information to include in an RFQ (not mandatory for every enquiry):
- Alloy / grade (Inconel 718) and UNS (N07718)
- Plate (B670) vs bar/forging (B637) — do not assume B564
- Aging / heat-treat sequence if strength-critical
- Tube-sheet OD / dimensions / thickness
- Tube OD, pitch, hole diameter and pattern
- Drawing + revision, quantity, machining tolerance, inspection / testing
Continue from grade identity into product form and machining:
Manufacturing Note
718 requires a post-machining precipitation-hardening heat treatment to reach its rated strength — machining is done in the solution-annealed (softer) condition, then aged afterward, which adds a manufacturing step and lead time not present with solid-solution alloys like 625.
Advantages & Limitations
Advantages
- Highest strength-to-weight of the alloys covered here
- Good high-temperature strength retention to ~650°C
- Reasonable general corrosion resistance alongside its strength
Limitations
- Highest cost and longest lead time in the nickel alloy range
- Requires post-machining age-hardening heat treatment
- Overkill unless the strength-to-weight requirement is genuine
FAQ
Generally no — if the requirement is corrosion resistance rather than exceptional strength, 625 is typically more cost-effective and easier to machine and weld, without a strength-driven need for age hardening.
718 develops its high strength through precipitation of niobium-rich phases during controlled aging. Machining in the solution-annealed condition (before aging) is far easier since the material is significantly softer; aging afterward locks in the final strength.
Longer than any other alloy in this range, given the specialist material sourcing plus the additional age-hardening heat treatment step — confirm timeline with our engineering team before committing to a project schedule.