# Nimonic 80A Bolts

*UNS N07080 · 2.4952 · GH4080A*

**Category:** Nickel-Based Superalloy

Nimonic 80A (UNS N07080, GH4080A, 2.4952) is the highest-temperature grade in our standard fastener range, rated to 815°C and supplied to BS HR 401 and AMS 5828 at 1100 MPa tensile and 620 MPa yield in the solution-plus-aged condition. Strengthening comes from a fine, thermally stable gamma-prime Ni₃(Al,Ti) dispersion that does not over-age the way Inconel 718's γ″ does, so nimonic 80a bolts hold useful load capacity to 815°C.

It is the classic material for large-bore diesel exhaust valves, gas turbine blade fixings and steam generator bolting, and nimonic 80a fasteners are proven anywhere a joint must stay tight through thousands of thermal cycles above 700°C.

Because titanium and aluminium are highly reactive, nimonic bolts must be vacuum melted. Our VIM + VAR route for UNS N07080 bolts keeps oxygen below 10 ppm so the gamma-prime forms cleanly and the alloy retains its stress-rupture life.

## Standards

- BS HR 401
- AMS 5828
- UNS N07080
- GH4080A
- 2.4952

## Chemical composition (wt%)

| Element | Min | Max |
|---|---|---|
| Ni | Balance | - |
| Cr | 18.0 | 21.0 |
| Ti | 1.80 | 2.70 |
| Al | 1.00 | 1.80 |
| Fe | - | 3.00 |
| Co | - | 2.00 |
| Mn | - | 1.00 |
| Si | - | 1.00 |
| C | - | 0.10 |
| Cu | - | 0.20 |
| S | - | 0.015 |
| B | - | 0.008 |

## Mechanical properties

| Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| Solution + Aged | 1100 | 620 | 20 | 30-38 HRC |
| Hot-Finished + Aged | 1000 | 550 | 22 | 28-35 HRC |
| Solution Treated | 780 | 350 | 40 | ≤ 25 HRC |

## Applications

- **Power Generation**: Nimonic 80A bolts for gas turbine blade fixings, hot gas path bolting and steam generator studs at 700-815°C.
- **Marine & Diesel**: Two-stroke and four-stroke exhaust valve spindles, valve seat bolting and turbocharger hardware.
- **Nuclear**: Steam generator internals and bolting where thermal stability over decades outweighs peak strength.
- **Industrial Furnaces**: Radiant tube supports, retort bolting and fixtures in continuous high-temperature operation.

## FAQ

### Why do nimonic 80a bolts outperform Inconel 718 above 700°C?

Inconel 718 relies on the metastable γ″ phase, which coarsens and transforms to delta above roughly 650°C. Nimonic 80A fasteners use gamma-prime Ni₃(Al,Ti), which stays coherent and finely dispersed to 815°C, so stress-rupture life is far longer at temperature.

### Nimonic 80A or Inconel 718 for my application?

Below 650°C choose Inconel 718 for its 1275 MPa tensile. Above 700°C choose Nimonic 80A: its room-temperature strength is lower but it retains far more of it where the joint actually operates.

### Can Nimonic 80A be used for exhaust valves?

Yes. It is the industry standard spindle material for medium and large bore diesel engines, combining hot hardness, sulphidation resistance and resistance to valve seat pounding.

### What certification do you supply for nimonic 80a bolts and nimonic 80a fasteners?

EN 10204 3.1 as standard, 3.2 with SGS, TÜV or BV witness on request. Every lot of nimonic bolts includes chemistry, mechanicals, grain size to ASTM E112 and stress-rupture data on request.