ThePipingMart Blog Grades Hastelloy® C-4 (UNS N06455) – Composition, Properties, and Uses

Hastelloy® C-4 (UNS N06455) – Composition, Properties, and Uses

Hastelloy C4

Regarding high-performance alloys, Hastelloy C4 has become a go-to choice in many industries. It is a versatile alloy that can withstand various corrosive environments, high temperatures, and mechanical stress. This alloy has earned its reputation for its exceptional corrosion resistance and unique combination of physical and mechanical properties. This blog post will discuss everything you need to know about Hastelloy C4, from its composition to its uses and applications.

What is Hastelloy C4?

Hastelloy C4 is a nickel-chromium-molybdenum alloy with excellent corrosion resistance in various industrial environments. It exhibits outstanding resistance to oxidizing acids such as nitric acid, hydrochloric acid, and sulfuric acids, as well as numerous reducing agents. Its highly alloyed chemistry provides exceptional resistance to stress corrosion cracking, pitting, and crevice corrosion.

Hastelloy C4 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.

Element Content (%)
Chromium, Cr 14-18
Molybdenum, Mo 14-17
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 Remainder

Hastelloy C4 Mechanical Properties

One of the significant advantages of Hastelloy C4 is its excellent mechanical properties, which make it ideal for high-stress applications. Its tensile strength is approximately 125 ksi, with a yield strength of 52 ksi and an elongation capacity of 58%. Hastelloy C4 also has a high fracture toughness value and excellent fatigue strength.

Properties Metric Imperial
Tensile strength 738 MPa 107000 psi
Yield strength ( @ 0.2% offset) 492 MPa 71400 psi
Elastic modulus 211 GPa 30600 ksi
Elongation at break (in 50.8 mm) 42% 42%

Hastelloy C4 Physical Properties

Apart from mechanical strength, Hastelloy C4 also boasts impressive physical properties, such as a high melting point, density, and thermal conductivity. Its melting point is 1370°C, with a thickness of 8.64 g/cm3. Its thermal conductivity ranges from 8.1-11.7 W/mK. Moreover, the alloy’s low thermal expansion coefficient is ideal for high-temperature applications.

Properties Metric Imperial
Density 8.64 g/cm³ 0.312 lb/in³
Melting point 1427°C 2600°F

Hastelloy C4 Thermal Properties

Properties Metric Imperial
Thermal expansion co-efficient (@ 20°C/68°F) 10.8 µm/m°C 6 µin/in°F
Thermal conductivity (@ 23°C/73°F) 10.1 W/mK 70.1 BTU in/hr.ft².°F

Hastelloy C4 Equivalents

  • ASTM B574
  • ASTM B575
  • ASTM B619
  • ASTM B622
  • ASTM B626
  • DIN 2.4610

Hastelloy C4 Uses

Hastelloy C4 is used in various industries, including chemical processing, aerospace, power generation, petrochemical, pharmaceuticals, and marine applications. This alloy suits sulfuric acid, hydrochloric acid, and acetic acid applications. It is commonly used in chemical reactors, heat exchangers, furnace components, and catalyst support grids.

Hastelloy C4 Corrosion Resistance

Hastelloy C4 is a highly corrosion-resistant material, standing up well to several corrosive environments, including oxidizing and reducing acid environments. It has superior resistance to pitting, crevice corrosion, and stress cracking. In addition to its resistance to acid and highly corrosive environments, Hastelloy C4 also resists intergranular cracking in welding.

Hastelloy C4 Heat Treatment:

Hastelloy C4 requires careful heat treatment to achieve optimal mechanical properties. The alloy is annealed at 1025°C-1125°C followed by rapid cooling through water or air quenching. The material is then age-hardened by heating to 870°C- 980°C for one hour, followed by water or air quenching.

Hastelloy C4 Machining

Hastelloy C4 is classified as a difficult-to-machine alloy due to its high elasticity modulus and work hardening. Therefore, special care must be taken when machining Hastelloy C4. Carbide-cutting tools are recommended to minimize tool wear and prolong tool life. High-speed steel tools are not recommended since they wear quickly.

Hastelloy C4 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.


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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