Hastelloy C-4

Hastelloy C-4 is a corrosion-resistant nickel-molybdenum alloy with excellent performance in high-temperature environments and chemical processing industries.

About Hastelloy C-4

Name and Equivalent Name: Hastelloy C-4, or UNS N06455 or Alloy C-4, is a versatile superalloy with outstanding corrosion resistance. It complies with ASTM B575, B622, B619, DIN/EN 2.4610, GB/T 14992: NS142, AMS 5543, and ASME SB-575. Recognized under NACE MR0175, it offers reliability in aggressive chemical and high-temperature environments.

Hastelloy C-4 Basic Introduction

Hastelloy C-4 is a high-performance nickel-molybdenum alloy developed in demanding chemical and industrial environments. It provides excellent corrosion resistance, particularly in highly oxidizing and reducing conditions, including hydrochloric acid and ferric ions. This makes it a preferred material for chemical reactors, heat exchangers, and gas scrubbers.

The alloy maintains mechanical integrity and resists thermal fatigue even at elevated temperatures, making it practical for long-term operations. Hastelloy C-4 exhibits enhanced weldability and reduced carbide precipitation, extending its lifespan and ensuring reliable performance in harsh environments.

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Alternative Superalloys of Hastelloy C-4

Alternatives to Hastelloy C-4 include Hastelloy C-276, Inconel 625, Alloy 20, and Monel 400. Hastelloy C-276 offers better performance in broader chemical environments. Inconel 625 provides superior mechanical strength at elevated temperatures. Alloy 20 is more suitable for sulfuric acid environments, while Monel 400 excels in marine and seawater applications. Each alternative provides a unique advantage depending on the specific conditions.


Hastelloy C-4 Design Intention

Hastelloy C-4 was engineered to handle highly corrosive environments and resist thermal instability over long periods. The addition of titanium enhances resistance to intergranular attack, preventing structural degradation.

The alloy offers superior resistance to oxidation and localized corrosion, making it ideal for chemical reactors, heat exchangers, and other industrial equipment exposed to fluctuating temperatures. Its thermal stability ensures mechanical strength between 500°C and 900°C, reducing maintenance and extending the operational life of critical components.


Hastelloy C-4 Chemical Composition

Hastelloy C-4’s composition is optimized for exceptional resistance to oxidizing and reducing agents. Molybdenum ensures corrosion resistance, while titanium improves mechanical stability.

Element

Content (wt%)

Nickel (Ni)

Balance

Chromium (Cr)

14.0 - 17.0

Molybdenum (Mo)

15.0 - 17.0

Iron (Fe)

2.0 max

Carbon (C)

Max 0.01

Titanium (Ti)

Max 0.7


Hastelloy C-4 Physical Properties

Hastelloy C-4 offers excellent thermal conductivity, high density, and stability under elevated temperatures, making it suitable for harsh environments.

Property

Value

Density (g/cm³)

8.64

Melting Point (°C)

1335

Thermal Conductivity (W/(m·K))

11.2

Modulus of Elasticity (GPa)

205


Metallographic Structure of Hastelloy C-4 Superalloy

Hastelloy C-4 exhibits a face-centered cubic (FCC) structure, enhancing ductility and corrosion resistance. The alloy’s design ensures minimal carbide precipitation during welding and heat treatment, preventing intergranular attack and preserving mechanical integrity.

The addition of titanium enhances the stability of the microstructure, even at high temperatures, reducing the formation of unwanted phases. This ensures that Hastelloy C-4 components retain their mechanical properties and resist degradation under continuous exposure to heat and chemicals.


Hastelloy C-4 Mechanical Properties

Hastelloy C-4 offers a combination of mechanical strength and corrosion resistance, making it suitable for harsh environments with high temperatures and chemical exposure.

Mechanical Property

Value

Tensile Strength (MPa)

780 - 890

Yield Strength (MPa)

310 - 400

Creep Strength

Strong at 500-900°C

Fracture Toughness

High

Fatigue Strength

Strong at 1000°C

Creep Rupture Life

Long-term durability at elevated temperatures

Hardness (HRC)

Rockwell C20 - 30

Elongation (%)

~50

Elastic Modulus (GPa)

~210


Key Features of Hastelloy C-4 Superalloy

1. Exceptional Corrosion Resistance

Hastelloy C-4 offers outstanding resistance to oxidizing and reducing chemicals, including hydrochloric acid. It minimizes the risk of localized corrosion, pitting, and stress corrosion cracking, ensuring long-term reliability.

2. Thermal Stability at Elevated Temperatures

The alloy performs well between 500°C and 900°C, making it suitable for equipment exposed to high thermal stress. It resists thermal fatigue, ensuring stable performance over extended periods.

3. Long-Term Mechanical Strength

With a tensile strength of up to 890 MPa and excellent fracture toughness, Hastelloy C-4 maintains mechanical integrity even under harsh environmental conditions, reducing the need for frequent maintenance.

4. Enhanced Weldability and Structural Stability

The low carbon content and addition of titanium ensure minimal carbide precipitation during welding, preventing intergranular corrosion and ensuring reliable welds.

5. Versatile Applications in Critical Industries

Hastelloy C-4 is widely used in chemical processing, energy, and aerospace industries. Its resistance to high temperatures and corrosive agents makes it ideal for heat exchangers, reactors, and gas scrubbers.

Hastelloy C-4 Superalloy’s Machinability

Vacuum Investment Casting: Hastelloy C-4 is not commonly used in Vacuum Investment Casting due to its limited flowability and high susceptibility to cracking during solidification. Alloys with better casting behavior are preferred for precision applications.

Single Crystal Casting: Hastelloy C-4 is unsuitable for Single Crystal Casting because its composition does not allow the formation of single-crystal structures needed for turbine components requiring exceptional creep resistance.

Equiaxed Crystal Casting: Hastelloy C-4 can be applied in Equiaxed Crystal casting. However, it is not a primary choice due to its focus on corrosion resistance over mechanical properties required in turbine blade production.

Directional Casting: Hastelloy C-4 is not ideal for Superalloy Directional Casting due to the absence of required creep strength for high-temperature aerospace components made through this method.

Powder Metallurgy Turbine Disc: Hastelloy C-4 is not widely used in Powder Metallurgy Turbine Disc applications since the focus of turbine discs is on mechanical strength, while C-4 prioritizes corrosion resistance.

Precision Forging: Hastelloy C-4 is suitable for Superalloy Precision Forging, producing components with enhanced corrosion resistance for chemical reactors and industrial equipment.

Superalloy 3D Printing: Superalloy 3D Printing with Hastelloy C-4 is feasible for manufacturing complex, corrosion-resistant components required in chemical and pharmaceutical industries.

CNC Machining: Hastelloy C-4 performs well in CNC Machining with proper tools and cooling systems, ensuring precision in manufacturing high-performance chemical processing equipment.

Superalloy Welding: Superalloy Welding with Hastelloy C-4 is adequate, thanks to its low carbon content, which minimizes carbide precipitation, ensuring strong and reliable welds in chemical applications.

Hot Isostatic Pressing (HIP): Hot Isostatic Pressing (HIP) enhances Hastelloy C-4’s structural properties by eliminating porosity, making it suitable for critical chemical and industrial environments.


Hastelloy C-4 Superalloy Applications

Aerospace and Aviation: Hastelloy C-4 is used in Aerospace and Aviation for auxiliary components exposed to corrosive environments, such as gas scrubbers and exhaust systems.

Power Generation: In Power Generation, the alloy is used in heat exchangers and gas scrubbers that operate under corrosive conditions, ensuring efficient energy production.

Oil and Gas: Hastelloy C-4 plays a vital role in Oil and Gas applications, such as pipelines and valves, due to its superior resistance to hydrogen sulfide and aggressive chemicals.

Energy: Hastelloy C-4 is valuable in Energy systems for handling chemical storage and reactors, maintaining reliability under extreme conditions and temperature fluctuations.

Marine: In Marine environments, the alloy resists seawater corrosion, making it suitable for desalination equipment and marine chemical handling systems.

Mining: Hastelloy C-4 is employed in Mining to manufacture chemical extraction equipment, ensuring performance in highly corrosive environments.

Automotive: In Automotive applications, Hastelloy C-4 can be used in specialized exhaust systems and chemical handling components for electric vehicles.

Chemical Processing: Hastelloy C-4 is widely used in chemical processing industries, particularly in reactors and heat exchangers encountering highly corrosive chemicals like hydrochloric acid.

Pharmaceutical and Food: In the Pharmaceutical and Food industries, Hastelloy C-4 ensures equipment safety by resisting aggressive cleaning agents and maintaining hygiene standards.

Military and Defense: Hastelloy C-4 finds applications in Military and Defense systems requiring chemical protection, such as specialized storage tanks and equipment handling corrosive substances.

Nuclear: The alloy is used in Nuclear facilities for critical components, such as cooling systems and reactors, ensuring long-term reliability under extreme temperatures and chemical exposure.


When to Choose Hastelloy C-4 Superalloy

Custom superalloy parts made from Hastelloy C-4 are essential when operations involve harsh chemical environments, such as hydrochloric acid or other oxidizing agents. Its corrosion resistance and mechanical strength are ideal for equipment like heat exchangers, chemical reactors, and gas scrubbers.

Hastelloy C-4 should be selected for applications that experience fluctuating temperatures between 500°C and 900°C. Its ability to maintain performance under high thermal stress reduces downtime and maintenance costs, making it particularly useful in chemical processing, energy, and power generation industries. The alloy’s weldability and compatibility with HIP enhance its reliability for long-term industrial operations. Choose Hastelloy C-4 for custom components requiring durability, thermal stability, and resistance to aggressive chemical environments.

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