The Enigmatic Alloy Hastelloy C276

┃ Overview

Hastelloy C-276 (UNS N10276, Alloy C-276, W.Nr. 2.4819) is a nickel-molybdenum-chromium alloy that is strengthened by solid solution, with a small proportion of tungsten. It demonstrates exceptional resistance to corrosion in various challenging environments. Its high molybdenum content provides protection against localized corrosion, including pitting. Moreover, the low carbon content prevents the formation of carbides during welding, thereby preserving its resistance to intergranular attack in the heat-affected zones of welded joints. Additionally, Hastelloy C-276 possesses good ductility, making it easily formable and weldable.

┃ Application

Chemical Processing: Pipes, valves, pumps, heat exchangers, and vessels where resistance to corrosive chemicals is crucial

Oil and Gas: Valves, piping systems, pump shafts, and downhole equipment

Desalination Plants: Evaporators, heat exchangers, and piping systems

Pollution Control: Scrubbers, flue gas desulfurization systems, and exhaust ducts

Pharmaceutical Industry: Reactors, storage vessels, and equipment that handle corrosive chemicals and pharmaceutical intermediates

Aerospace: Aircraft exhaust systems, gas turbine components, and missile and rocket motors

Waste Treatment: Tanks, scrubbers, and pumpsries

┃ Chemical Composition (%)

┃ Mechanical Property

┃Corrosion Resistance

Hastelloy C-276 is widely recognized as the most corrosion-resistant material available today. It offers unparalleled resistance to various forms of corrosion, including general corrosion, stress corrosion cracking, pitting, and crevice corrosion, in a wide range of harsh environments. Its ability to resist carbide precipitation during welding ensures that its corrosion resistance is maintained in the heat-affected zones of welded joints.

Hastelloy C-276 excels in its resistance to sulfuric acid, hydrochloric acid, acid chlorides, solvents, formic and acetic acids, acetic anhydride, wet chloride gas, hypochlorites, and chlorine solutions. Furthermore, it exhibits exceptional resistance to phosphoric acid at temperatures below the boiling point and at concentrations below 65 wt%. Notably, Alloy C-276 demonstrates excellent resistance to corrosion by seawater, particularly in crevice conditions that would normally cause damage to other commonly used materials.

┃Heat Treatment

Heat treatment of Hastelloy C-276 is commonly performed to enhance its mechanical properties, reduce residual stresses, and optimize its corrosion resistance. Stress relieving, solution annealing, and aging are some common heat treatment processes. The desired outcomes and the specific application requirement of Alloy C-276 vary, the specific heat treatment process may vary.

┃ Heating and Pickling

Heat treatment is a commonly employed method to improve the mechanical properties, alleviate residual stresses, and optimize the corrosion resistance of Hastelloy C-276. Depending on the desired outcomes and the specific application requirements of Alloy C-276, various heat treatment processes such as stress relieving, solution annealing, and aging can be utilized. The selection of the specific heat treatment process may vary accordingly.

Pickling is a chemical procedure commonly employed on Hastelloy C-276 to eliminate surface contaminants, scale, and oxide layers. This process is typically carried out after welding, hot forming, or when the material's surface has been contaminated. It involves immersing the material in an acid solution to dissolve the undesired layers. The acids commonly used for pickling Hastelloy C-276 include mixtures of nitric and hydrofluoric acids, or mixtures of nitric and hydrochloric acids. The duration of immersion varies depending on the extent of surface contaminants and the desired level of cleaning.

┃ Hot and Cold Forming

For hot forming of Hastelloy C-276, it is recommended to maintain temperatures within the range of 1600 to 2250°F (870 to 1230°C), with heavy forming operations preferably conducted above 2000°F (1090°C). The alloy is typically annealed at temperatures ranging from 2100 to 2150°F (1150 to 1175°C), followed by rapid cooling, often achieved through water quenching.

Hastelloy C-276 is also suitable for cold forming processes, including bending, drawing, deep drawing, and cold rolling. However, it should be noted that the alloy exhibits high work hardening rates, which means it becomes increasingly harder and more resistant to deformation as it undergoes cold working. To maintain ductility and minimize the risk of cracking, frequent annealing or intermediate heat treatments may be necessary during the cold working process. These treatments help restore ductility and alleviate the effects of work hardening.

┃ Machining

Hastelloy C-276 is a collection of nickel-based superalloys renowned for their outstanding corrosion resistance, high-temperature strength, and favorable fabricability. However, machining Hastelloy alloys can present challenges due to their toughness and tendency to work harden. Nevertheless, by employing appropriate techniques, it is feasible to achieve satisfactory outcomes in machining operations.

┃Welding

Hastelloy C-276 possesses favorable weldability and can often be utilized in its as-welded condition for various applications. In cases where enhanced corrosion resistance is necessary, INCOWELD® filler metal and welding electrode 686CPT® can be employed to "overmatch" the properties of Alloy C-276, providing superior corrosion resistance.

┃ Product Forms 

Ø Bar & Rod

Ø Plate & Sheet

Ø Coil & Strip

Ø Pipe & Tube

Ø Fitting: Flange, Tee, Elbow, Reducer etc.

Ø Forging: Ring, Shaft, Circle, Block etc.

┃ Note

Ronsco is a supplier with more than 27 years of experience in the special metal field, we always adheres to the business phiosophy of "customer-centered", tries its best to meet the requirements of customers and pursues win-win cooperation with customers. Are you looking for special metal products one-stop supplier! Contact Us Now! Email: marketing@ronsteel.com