Alloy C276 Round Bar / Hastelloy C276 Plate / C276 Seamless Pipes / C276 Strips Custom Produce as Request

Hastelloy C-276 is a nickel-chromium-molybdenum alloy renowned for its exceptional corrosion resistance in a wide range of severe chemical environments. This versatile material maintains excellent resistance to oxidizing and reducing conditions, making it a premier choice for critical applications in chemical processing, pollution control, and other demanding industries where corrosion resistance is paramount.

Chemical Composition: The Foundation of Performance

The outstanding corrosion resistance of Hastelloy C-276 stems from its carefully balanced chemical composition. As a nickel-based alloy, it incorporates strategic additions of chromium, molybdenum, and tungsten to create a robust defense against various corrosive media.

*Table 1: Standard Chemical Composition of Hastelloy C-276*

The high nickel content provides inherent resistance to reducing environments, while chromium enhances resistance to oxidizing media by forming a protective oxide layer. Molybdenum and tungsten significantly contribute to resistance against localized corrosion such as pitting and crevice corrosion, particularly in chloride-containing environments. The extremely low carbon and silicon content is crucial for minimizing intergranular corrosion in welded structures .

Physical & Mechanical Properties: Strength in Adverse Conditions

Hastelloy C-276 exhibits a favorable combination of physical and mechanical properties that make it suitable for both corrosive and high-temperature applications.

*Table 2: Physical Properties of Hastelloy C-276*

Table 3: Typical Mechanical Properties at Room Temperature (Annealed Condition)

The alloy maintains good mechanical properties at elevated temperatures, with useful strength retention up to approximately 1040°C (1904°F) in oxidizing atmospheres . The combination of high strength and excellent ductility allows for good formability and fabrication characteristics.

Exceptional Corrosion Resistance: The Defining Feature

Hastelloy C-276 stands out for its exceptional performance across a broad spectrum of corrosive environments:

• Oxidizing and Reducing Media: Performs well in both chemical conditions, unlike many specialized alloys that excel in only one type

• Localized Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking, particularly in chloride-ion containing environments

• Acid Resistance: Effectively withstands sulfuric, hydrochloric, phosphoric, and organic acids, especially those containing impurities or aerated mixed acids

• Chlorine Compound Resistance: One of the few materials capable of resisting wet chlorine, hypochlorites, and chlorine dioxide solutions

• Salt Solutions: Demonstrates significant corrosion resistance to high-concentration chloride salt solutions such as ferric chloride and cupric chloride

This comprehensive corrosion resistance stems from the synergistic effect of its alloying elements, with molybdenum and chromium providing defense against reducing and oxidizing conditions respectively, while the low carbon content minimizes susceptibility to intergranular attack after welding or thermal processing.

Manufacturing and Heat Treatment: Ensuring Optimal Performance

The manufacturing of Hastelloy C-276 products follows precise thermomechanical processing to achieve the desired microstructure and properties:

Manufacturing Process:
The production typically involves vacuum induction melting (VIM) followed by vacuum arc remelting (VAR) to achieve high purity with controlled inclusion content . For seamless pipes, the process involves hot extrusion followed by multiple passes of cold rolling or drawing with intermediate solution annealing to achieve final dimensions and enhance mechanical properties .

Heat Treatment:
Solution annealing is critical for Hastelloy C-276 and is typically performed at 1120-1170°C (2048-2138°F) followed by rapid quenching . This process dissolves any secondary phases that may have formed during thermal processing and restores the alloy's optimum corrosion resistance. For heavy sections or after severe cold working, stress relief annealing at 870-980°C (1600-1796°F) may be applied to minimize residual stresses that could lead to stress corrosion cracking .

Product Forms and Custom Manufacturing

Hastelloy C-276 is available in various product forms to suit different application requirements:

• Round Bars: Available in various diameters for shafting, fasteners, and valve components

• Plates: Supplied in thicknesses ≥6.0mm for pressure vessels, tank construction, and structural applications

• Seamless Pipes: Manufactured to ASTM B622/ASME SB622 standards for process piping systems

• Strips and Sheets: Thin gauges for gaskets, liners, and specialized components

• Other Forms: Also available as wires, fittings, flanges, and custom forgings

Custom manufacturing allows for tailored solutions in terms of dimensions, surface finishes, and specific heat treatment conditions to meet unique application requirements.

Applications Across Industries

The unique properties of Hastelloy C-276 have led to its adoption in numerous demanding industries:

• Chemical Processing: Reactors, heat exchangers, and piping systems handling aggressive media including chlorinated organics

• Pollution Control: FGD system components including absorber towers, reheaters, and dampers

• Pulp and Paper Industry: Digester and bleaching equipment handling corrosive chemicals

• Pharmaceutical Industry: Critical reaction vessels and piping where purity and corrosion resistance are essential

• Waste Treatment: Incineration systems and wastewater treatment components

• Oil and Gas: Offshore platform equipment and sour gas handling systems containing H₂S/CO₂/Cl⁻ environments

• Nuclear Fuel Processing: Equipment for reprocessing spent nuclear fuel

Welding and Fabrication Considerations

Hastelloy C-276 exhibits good weldability using common techniques such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and shielded metal arc welding . For best results:

• Use matching filler metals such as ERNiCrMo-4

• Maintain a clean, contamination-free work environment

• Avoid sulfur-containing markers or tools to prevent embrittlement

• Control interpass temperatures and heat input to minimize microsegregation

• Post-weld heat treatment is generally not required due to the alloy's low carbon content

Standards and Specifications

Hastelloy C-276 products are manufactured to various international standards depending on the product form:

• Plates, Sheets, and Strips: ASTM B575/ASME SB575

• Seamless Pipes and Tubes: ASTM B622/ASME SB622

• Welded Pipes: ASTM B619/ASME SB619

• Fittings and Flanges: ASTM B366/ASME SB366

• Bars and Forgings: ASTM B564/ASME SB564

Other relevant specifications include AMS 5754 for aerospace applications and NACE MR0175/ISO 15156 for sour service environments .

Conclusion

Hastelloy C-276 represents a premium solution for extreme corrosion challenges across multiple industries. Its balanced composition, featuring nickel-chromium-molybdenum with controlled tungsten addition and minimal carbon content, delivers unmatched performance in both oxidizing and reducing environments. Available in various product forms including round bars, plates, seamless pipes, and strips, this versatile alloy can be custom-manufactured to meet specific application requirements. When properly processed and fabricated according to recommended guidelines, Hastelloy C-276 components provide reliable, long-term service in some of the most corrosive industrial environments, offering exceptional value despite higher initial costs through extended service life and reduced maintenance requirements.