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What Is Hastelloy C4 Material Grade?

Views: 2     Author: Wang     Publish Time: 2024-05-14      Origin: Site

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Hastelloy C-4 is a grade of Hastelloy which is a nickel-molybdenum alloy. There are many different grades of Hastelloy, which includes C-4. Grades of Hastelloy have each been optimized for a specific purpose. Molybdenum makes Hastelloy harder and stronger at high temperatures. This alloying element and the characteristics it imbues into the material also makes it great for welding applications. These nickel alloys are easily fabricated and formed. They also exhibit good ductility and are able to be cold worked.

All grades of Hastelloy are considered to be a corrosion resistant alloy because each grade exhibits superior resistance to various corrosive environments. Hastelloy has outstanding resistance to highly oxidizing corrosives such as oxidizing salts and reducing agents, making it a great alloy to specify for applications used in moderate to severe corrosive environments. HASTELLOY C-4 alloy (UNS N06455) is the most (microstructurally) stable of the widely used nickel-chromium-molybdenum materials, which are well known for their resistance to many aggressive chemicals, in particular hydrochloric acid, sulfuric acid, and chlorides. This stability means that the alloy can be welded without fear of sensitization, i.e. the nucleation and growth of deleterious, second phase precipitates in the grain boundaries of the weld heat-affected zone (HAZ).

Hastelloy C4 is a nickel-chromium-molybdenum alloy which has improved thermal stability. In this alloy, the tungsten was totally omitted and the iron content was reduced to approximately 1%. The alloy also contains approximately 0.3% Ti. Outstanding high-temperature stability; exhibits good ductility and corrosion resistance after long-time aging at 650 to 1040 °C (1200–1900 °F). Resists formation of grain-boundary precipitates in weld heat-affected zones, and is suitable for most chemical process applications in the as-welded condition. Has excellent resistance to stress-corrosion cracking and to oxidizing atmospheres up to 1040 °C (1900 °F).

Hastelloy C4 has exceptional resistance to a variety of chemical process environments, including hot contaminated mineral acids, solvents, chlorine, and chlorine-contaminated media (organic and inorganic, dry chlorine, formic and acetic acids, acetic anhydride, seawater, and brine). The general corrosion resistance of Alloy C276 and Alloy C4 was essentially the same in many corrosive environments, except that in strongly reducing media like hydrochloric acid, Alloy C276 was better; but in highly oxidizing media, the opposite was true, that is, Alloy C4 was better. Alloy C4 offers good corrosion resistance to a wide variety of media including organic acids and acid chloride solutions.

Hastelloy C4 Chemical Composition

Hastelloy C4 is a member of the Hastelloy family of alloys, a group of nickel-based alloys that are highly corrosion-resistant in harsh chemical environments. It has a chemical composition of 64% nickel, 16% chromium, 16% molybdenum, and 2% iron. Adding small amounts of tungsten and copper provides stability, strength and improved corrosion resistance.The chemical composition of Hastelloy(r) C-4 is outlined in the following table.


Content (%)

Chromium, Cr


Molybdenum, Mo


Iron, Fe

3 max

Cobalt, Co

2 max

Manganese, Mn

1 max

Titanium, Ti

0.7 max

Silicon, Si

0.08 max

Phosphorus, P

0.04 max

Sulfur, S

0.03 max

Carbon, C

0.015 max

Nickel, Ni


Physical Properties of Hastelloy C4

Production standards: Production standards for Hastelloy C4 include ASTM B564, ASTM B574, ASTM B575 and other standards. These standards specify the chemical composition of the alloy, mechanical properties, heat treatment process and other requirements.

Forging: Hastelloy C4 can be processed by hot forging and cold forging. The temperature range of hot forging is 1150-950℃, and the temperature range of cold forging is 760-870℃.

Heat treatment: Hastelloy C4 can be heat treated by solution treatment and aging treatment. The solid solution treatment temperature is 1150-900℃ and the aging treatment temperature is 760℃.

Cold working: Hastelloy C4 in the work-hardened state of tensile strength and yield strength are high, so it is suitable for cold working, such as cold rolling, cold drawing and so on.

High temperature resistance: Hastelloy C-4 alloy has good mechanical properties and stable chemical properties in high temperature environments. It can maintain high strength in high temperature environments, has a low thermal expansion coefficient and good thermal conductivity. This makes C-4 alloy an ideal material for many high temperature applications.

Corrosion resistance: Hastelloy C4 has excellent corrosion resistance, especially in chloride environments. It performs well in many acidic environments such as sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid. The corrosion resistance of the alloy is mainly due to its high content of chromium, rhenium and nickel. In addition, C-4 alloy also has good oxidation resistance.

Mechanical properties: Hastelloy C4 has a high yield strength and tensile strength, other mechanical property indicators including elongation, impact toughness.

Welding: Careful attention needs to be given when welding Hastelloy C4. The alloy can be readily welded, but the filler material selection is crucial to obtain optimal mechanical properties. TIG welding is the most common method of fusing Hastelloy C4 due to its low-heat input, allowing for successful welding without cracking. Moreover, post-welding heat treatment is required for Hastelloy C4 to reduce residual welding stress and restore mechanical properties.

Applications of Hastelloy C4

Chemical Processing Equipment: Ideal for reactors, vessels, and columns that handle corrosive substances.

Petrochemical Industry: Used in piping systems, heat exchangers, and other components exposed to harsh chemicals.

Pharmaceutical Industry: Suitable for manufacturing equipment that requires cleanliness and resistance to acidic environments.

Oil and Gas Production: Applied in sour gas wells and equipment dealing with hydrogen sulfide, where corrosion resistance is critical.

Pollution Control Equipment: Utilized in scrubbers and waste incinerators to withstand corrosive gases and high temperatures.

Flue Gas Desulfurization Systems: Used in components that are exposed to sulfur compounds and require high corrosion resistance.

Nuclear Reactor Systems: Suitable for parts that must resist corrosion in aggressive environments, ensuring safety and longevity.

Hastelloy C4 has become a top choice among industries requiring high-performance alloys due to its unique mechanical and physical properties, exceptional corrosion resistance, and versatility. We have learned how Hastelloy C4 stands out in various applications, from its composition to its mechanical and physical properties. Whether operating in the chemical processing, aerospace, or pharmaceutical industry, Hastelloy C4 offers excellent corrosion resistance to help your equipment last longer and perform better.

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