Hastelloy C-276: A Comprehensive Analysis of a Versatile Corrosion-Resistant Alloy- Shanghai Toko Technology Co.,Ltd

1. Overview of Hastelloy C-276

Hastelloy C-276 (UNS N10276) is a nickel-based corrosion-resistant alloy developed by Haynes International Inc., renowned as the "universal corrosion-resistant alloy" for its exceptional performance in extreme environments.

Key characteristics include:

High Nickel Content (~57%): Ensures chemical stability.
Multi-Element Composition (16% Cr, 16% Mo, 4% W, 5% Fe): Synergistically enhances corrosion resistance and high-temperature strength.
Ultra-Low Carbon Design (≤0.01% C): Minimizes intergranular corrosion risks.

Widely used in chemical processing, oil and gas, flue gas desulfurization (FGD), and nuclear industries, it excels in environments containing chlorides, strong acids, and mixed corrosive media.

2. International Designations

Hastelloy C-276 is standardized globally under various designations:

Region	Designation	Standard
United States	UNS N10276	ASTM B575, ASME SB575
China	NS3304	GB/T 15007
Germany	W.Nr. 2.4819	DIN/EN 2.4819
Japan	NW276	JIS H4554
International	Hastelloy C-276	ISO 6207, NACE MR0175

3. Chemical Composition and Microstructure

3.1 Key Components (wt%)

Element	Range	Functional Role
Ni	Base (~57%)	Resistance to reducing media
Cr	14.5–16.5%	Oxidation resistance & passivation
Mo	15–17%	Pitting/crevice corrosion resistance
W	3–4.5%	High-temperature corrosion resistance
Fe	4–7%	Phase stabilization
C	≤0.01%	Minimizes carbide precipitation

3.2 Microstructure

C-276 exhibits a face-centered cubic (FCC) lattice structure, ensuring excellent ductility and workability. Its thermal expansion coefficient is 12.6 μm/m·°C (20–100°C), with a thermal conductivity of 10.1 W/m·K (100°C).

4. Corrosion Testing Standards and Performance

4.1 Key Testing Standards

ASTM G28: Evaluates intergranular corrosion susceptibility in boiling 50% H₂SO₄ + Fe₂(SO₄)₃ solution.
ASTM G48: Assesses pitting/crevice corrosion in FeCl₃ solutions.
NACE TM0177: Tests sulfide stress corrosion cracking (SSCC) resistance.
ISO 15156: Validates suitability for oil and gas corrosive environments.

4.2 Performance in Critical Environments

Medium	Test Conditions	Corrosion Rate (mm/year)	Rating
Boiling 98% H₂SO₄	100°C, 24h	0.18–0.35	Excellent
10% HCl (ambient)	Static immersion	<0.1	Good
Wet Cl₂ (saturated)	25–80°C	No localized corrosion	Outstanding
FeCl₃ (40°C)	72h immersion	<0.13	Superior

4.3 Key Corrosion Resistance Features

Dual Resistance: Stable in both oxidizing (e.g., nitric acid) and reducing (e.g., sulfuric acid) environments.
Stress Corrosion Cracking (SCC) Resistance: Complies with NACE MR0175 for H₂S-containing environments, with >20-year service life.
Limitation: Avoid use in hot concentrated HNO₃ due to insufficient Cr for protective oxide layer .

5. Applications and Advantages

5.1 Industrial Applications

Chemical Processing: Reactors, heat exchangers (handling H₂SO₄, HCl, organic acids).
Environmental Engineering: Scrubbers in FGD systems, wastewater treatment .
Marine Engineering: Seawater desalination plants, ship valves/pumps.
Nuclear Industry: Radioactive waste containers (radiation-induced corrosion resistance).

5.2 Technical Advantages

No post-weld heat treatment required (prevents sensitization).
Superior cold/hot workability (elongation ≥40%).
Low lifecycle cost (extends maintenance intervals by >50%)

6. Conclusion

Hastelloy C-276’s unique composition and FCC structure make it indispensable in harsh corrosive environments. Validated by ASTM, NACE, and ISO standards, it demonstrates industry-leading resistance to chlorides, acids, and mixed media. As industries demand higher material reliability, C-276 remains a cornerstone for corrosion-critical applications

For detailed specifications, refer to ASTM B574 or GB/T 15007 standards.

Data on composition, standards, and corrosion performance derived from search results