Hastelloy C-276 (UNS N10276) Alloy Properties and Applications

# Hastelloy C-276 (UNS N10276) Alloy Properties and Applications

## Introduction to Hastelloy C-276

Hastelloy C-276, also known as UNS N10276, is a nickel-molybdenum-chromium superalloy with tungsten added to improve its corrosion resistance. This alloy is part of the Hastelloy family of materials developed by Haynes International and is renowned for its exceptional performance in highly corrosive environments.

## Chemical Composition

The chemical composition of Hastelloy C-276 plays a crucial role in its outstanding properties:

Nickel (Ni): 52-62% (provides excellent corrosion resistance and high-temperature strength)

Molybdenum (Mo): 15-17% (enhances resistance to pitting and crevice corrosion)

Chromium (Cr): 14.5-16.5% (improves oxidation resistance)

Tungsten (W): 3-4.5% (increases overall corrosion resistance)

Iron (Fe): 4-7% (balance element)

Cobalt (Co): ≤2.5%

## Physical Properties

Mechanical Properties

Tensile Strength: 690 MPa (100 ksi) min

Yield Strength: 283 MPa (41 ksi) min

Elongation: 40% min

Thermal Properties

Melting Range: 1325-1370°C (2420-2500°F)

Thermal Conductivity: 10.1 W/m·K (70 Btu·in/hr·ft²·°F) at 100°C

Specific Heat: 427 J/kg·K (0.102 Btu/lb·°F) at 25°C

## Corrosion Resistance

Hastelloy C-276 exhibits outstanding resistance to a wide range of corrosive media:

– Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking

– Superior performance in both oxidizing and reducing environments

– Resistant to sulfuric, hydrochloric, phosphoric, and acetic acids

– Maintains corrosion resistance in chloride-containing solutions

## Applications of Hastelloy C-276

Chemical Processing Industry

– Reactors, vessels, and heat exchangers

– Flue gas desulfurization systems

– Acid production equipment

Pollution Control

– Scrubbers and stack liners

– Waste treatment systems

Oil and Gas Industry

– Downhole components

– Offshore platform equipment

– Gas processing units

Pharmaceutical Industry

– Process equipment requiring high purity

– Reaction vessels

## Fabrication and Welding

Hastelloy C-276 can be readily fabricated using standard techniques:

– Welding: Can be welded using GTAW, GMAW, and SMAW processes

– Forming: Can be cold worked and hot formed

– Machining: Requires slower speeds and heavier feeds than carbon steel

## Comparison with Other Alloys

While Hastelloy C-276 shares some characteristics with Hastelloy X (UNS N06002), there are significant differences:

– Hastelloy X is primarily an oxidation-resistant, high-temperature alloy

– Hastelloy C-276 offers superior corrosion resistance in harsh chemical environments

– C-276 contains higher molybdenum