Alloy C276
Alloy C276 (UNS N10276) technical data — chemical composition, mechanical properties, ASTM B622 standards, and applications in highly corrosive environments.
1. Chemical Composition
The table below shows the elemental composition ranges for Alloy C276. The high molybdenum and tungsten content produces its resistance across a wide range of corrosive media.
| Grade | C | Mn | Si | S | Cr | Mo | Fe | W | Co | Other |
| N10276 (C-276) | ≤ 0.01 | ≤ 1.0 | ≤ 0.08 | ≤ 0.03 | 14.5–16.5 | 15.0–17.0 | 4.0–7.0 | 3.0–4.5 | 2.5 | V 0.35 |
2. Mechanical Properties
The following minimum mechanical properties apply to Alloy C276 in the solution-annealed condition for pipe and tube per ASTM B622 and associated product standards.
| Grade (UNS) | Alloy Family | Tensile Min, ksi (MPa) | Yield Min, ksi (MPa) | Elong. Min, % | Fiber Stress, psi |
| N10276 | Low C Ni-Mo-Cr (C-276) | ≥ 100 (690) | ≥ 41 (283) | ≥ 40 % | 25,000 |
3. Equivalent Grade
The table below maps Alloy C276 to equivalent designations in international material standards for procurement and engineering documentation across global projects.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| Alloy C276 | N10276 | H10276 | NS3304 | - | - | 2.4819 | - |
4. Key Technical Advantages
- Resistance to Both Oxidising and Reducing Media: The 14.5–16.5% Cr content handles oxidising acids and chlorine-bearing streams, while 15–17% Mo provides resistance in reducing acids. This dual capability makes C276 one of the few single-alloy solutions for mixed-duty chemical process service.
- Low Susceptibility to Localised Corrosion: C276's very low carbon (<=0.010%) and silicon (<=0.08%) contents minimise sensitisation in the heat-affected zone during welding. This reduces susceptibility to intergranular corrosion and crevice attack in the as-welded condition, a clear advantage over earlier Hastelloy C grades.
- Tungsten for Added Pitting Resistance: The 3–4.5% W addition improves pitting resistance in chloride environments and adds to overall corrosion performance in mixed acid streams, working together with molybdenum.
Technical Note: C276 is not suited for strongly oxidising acids at high concentrations (e.g., >70% nitric acid). It also has limited resistance to hot concentrated sulfuric acid. For strongly oxidising environments, Alloy C22 is preferred due to its higher Cr content.
5. Common Manufacturing Standards
ASTM B622: Standard specification for seamless nickel and nickel-cobalt alloy pipe and tube, covering UNS N10276 (Alloy C276) in seamless tubular form for corrosive service.
DIN EN ISO 6207 / DIN 17752: European standard for nickel alloy tubes and bars. C276 is designated 2.4819 under EN material numbering.
JIS H4552 / H4553: Japanese Industrial Standard for nickel and nickel alloy tubes, covering NW0276 designation for C276.
GB/T 15007: Chinese national standard for corrosion-resistant alloy plates. C276 tubular products are procured under ASTM B622 in most Chinese engineering specifications.
Manufacturing Standards Comparison Table:
| Standard | GB | EN/DIN | JIS | GOST |
| ASTM B622 (Seamless Pipe/Tube) | GB/T 15007 | DIN 2.4819 / EN | JIS H4552 (NW0276) | - |
| ASTM B619 (Welded Pipe) | GB/T 15007 | DIN 2.4819 | JIS H4553 | - |
6. Primary Applications
- Flue Gas Desulfurization: Absorber vessels, quench chambers, spray headers, and ductwork lining in coal and oil-fired power plant FGD systems handling hot acidic scrubber slurries with high chloride content.
- Pharmaceutical and Fine Chemical Reactors: Reactor vessels, heat exchanger tubes, and piping in multipurpose chemical and pharmaceutical plants where a single corrosion-resistant alloy must handle diverse process chemistries.
- Waste Incineration: Stack liners, quench chambers, and wet scrubber components in waste-to-energy and hazardous waste incineration facilities where HCl, SOx, and heavy metal chloride vapours concentrate.
- Acid Gas Injection (AGI): High-pressure injection tubing and downhole completion strings in acid gas (CO2 + H2S) injection wells. Partial pressures of corrosive gases combined with chloride-rich formation water create severe conditions.
- Pulp and Paper Bleaching: Chlorine dioxide stage piping, bleach washers, and chlorinator components where a hot chlorine dioxide solution at low pH demands the highest level of chloride pitting resistance.