# Hastelloy C-276 Bolts

*UNS N10276 · 2.4819 · Alloy C-276*

**Category:** Nickel-Molybdenum-Chromium Alloy

Hastelloy C-276 (UNS N10276, 2.4819) is a nickel-molybdenum-chromium bolting grade with a 425°C service limit, supplied to ASTM B574 and B575 at 790 MPa tensile and 355 MPa yield in the solution-treated condition. The 15-17% molybdenum and 3-4.5% tungsten let hastelloy c276 bolts and hastelloy c276 fasteners resist both oxidising and reducing media: wet chlorine, hypochlorite, ferric and cupric chlorides, hot contaminated mineral acids and sour gas.

It is a solid-solution alloy: it is not age hardened, so strength is modest at 790 MPa and service is limited to about 425°C before intermetallic mu and P phases begin to precipitate.

Extremely low carbon (0.01% max) and silicon means UNS N10276 bolts can be welded and used as-welded without the sensitisation and knife-line attack that plague higher-carbon grades, a key advantage for hastelloy bolts in field-fabricated chemical installations.

## Standards

- ASTM B574
- ASTM B575
- UNS N10276
- 2.4819

## Chemical composition (wt%)

| Element | Min | Max |
|---|---|---|
| Ni | Balance | - |
| Mo | 15.0 | 17.0 |
| Cr | 14.5 | 16.5 |
| Fe | 4.0 | 7.0 |
| W | 3.0 | 4.5 |
| Co | - | 2.50 |
| Mn | - | 1.00 |
| V | - | 0.35 |
| Si | - | 0.08 |
| C | - | 0.010 |
| P | - | 0.040 |
| S | - | 0.030 |

## Mechanical properties

| Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| Solution Treated | 790 | 355 | 60 | ≤ 100 HRB |
| Cold Worked | 930 | 620 | 25 | ≤ 30 HRC |
| ASTM B574 Bar | 690 min | 283 min | 40 min | - |

## Applications

- **Chemical Processing**: Hastelloy c276 bolts for reactor and heat exchanger bolting in sulphuric, phosphoric and hydrochloric acid service.
- **Pollution Control**: FGD scrubber internals, duct flange bolting and stack liners exposed to wet chloride condensate.
- **Pulp & Paper**: Bleach plant and digester fasteners handling chlorine dioxide and hypochlorite.
- **Waste Treatment**: Incinerator scrubbers and effluent handling equipment with mixed contaminant streams.

## FAQ

### Which environments suit hastelloy c276 bolts and hastelloy c276 fasteners best?

Wet chlorine, hypochlorite, chlorine dioxide, ferric and cupric chlorides, hot contaminated sulphuric and phosphoric acids, seawater and sour gas with H₂S. Hastelloy bolts resist both pitting and crevice attack and are effectively immune to chloride stress corrosion cracking.

### Why is the temperature limit only 425°C for hastelloy bolts and UNS N10276 bolts?

Above roughly 425°C prolonged exposure precipitates mu and P intermetallic phases at grain boundaries, embrittling the alloy and reducing corrosion resistance. For higher temperatures with good corrosion resistance use Inconel 625.

### Can C-276 be age hardened for higher strength?

No. It is a solid-solution alloy. Higher strength is only achieved by cold work, which is limited for fasteners because it reduces corrosion performance and ductility.