What is the Difference Between Inconel 625 and 825

Inconel 625 and Inconel 825 are both nickel-based superalloys known for their exceptional performance in high-temperature and corrosive environments. Despite their similar compositions and properties, they differ in their applications, performance, and suitability for specific industries. Understanding the difference between Inconel 625 and 825 is important for selecting the most appropriate alloy for different engineering and industrial uses.

What is the difference between Inconel 625 and 825? Inconel 625 contains nickel, chromium, and molybdenum as primary elements, with smaller amounts of niobium, iron, and other elements, while Inconel 825 contains nickel, iron, and chromium as primary elements, with additions of molybdenum, copper, and titanium.

Key Areas Covered

1. What is Inconel 625  
      – Definition, Features, Applications
2. What is Inconel 825
      – Definition, Features, Applications 
3. Similarities Between Inconel 625 and 825
      – Outline of Common Features
4. Difference Between Inconel 625 and 825
      – Comparison of Key Differences
5. FAQ: Inconel 625 and 825
      – Answers to Frequently Asked Questions

Key Terms

Inconel 625, Inconel 825

Difference Between Inconel 625 and 825 - Comparison Summary

What is Inconel 625

Inconel 625 is a nickel-based superalloy known for its exceptional resistance to corrosion and high temperatures. Developed by Special Metals Corporation, it has become a staple material in industries requiring robust performance in harsh environments, such as aerospace, chemical processing, marine engineering, and nuclear power generation.

At its core, Inconel 625 consists of nickel, chromium, and molybdenum, with additional elements like niobium and tantalum enhancing its mechanical properties. This alloy offers remarkable strength and toughness, even at elevated temperatures, making it ideal for applications exposed to extreme conditions.

One of the most notable features of Inconel 625 is its resistance to corrosion. It exhibits superb resistance to various corrosive elements, including acids, alkalis, and seawater. This makes it invaluable in marine and chemical processing industries where exposure to corrosive environments is commonplace.

Furthermore, its high-temperature resistance allows it to maintain its mechanical properties in environments with temperatures reaching up to 1800°F (982°C). This attribute is critical in applications like gas turbine engine components, where materials must withstand intense heat without compromising performance.

Inconel 625

Inconel 625 has excellent fatigue strength, which is essential for components subject to cyclic loading over extended periods. This makes it a preferred material for aerospace and nuclear applications where reliability is paramount.

In addition to its mechanical prowess, Inconel 625 is relatively easy to fabricate and weld compared to some other superalloys, adding to its appeal in manufacturing processes.

What is Inconel 825

Inconel 825 is a nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. It belongs to the family of superalloys renowned for their exceptional resistance to corrosion, high temperature, and pressure. Developed to withstand aggressive environments, particularly those containing sulfuric and phosphoric acids, Inconel 825 finds applications across various industries, including chemical processing, pollution control, marine engineering, and nuclear reactors.

One of the defining characteristics of Inconel 825 is its corrosion resistance, which extends across a broad spectrum of acidic and alkaline conditions. It is particularly well-suited for environments where sulfuric and phosphoric acids are present, making it indispensable in industries involved in the production of sulfuric acid, phosphoric acid, and other chemicals.

Moreover, the alloy exhibits impressive mechanical properties, including high tensile strength and excellent creep-rupture strength at elevated temperatures. This combination of strength and corrosion resistance makes it suitable for components subjected to high stress in aggressive environments, such as heat exchangers, chemical processing equipment, and piping systems.

Inconel 825 is also notable for its resistance to oxidation and carburization in high-temperature settings, further enhancing its reliability in demanding conditions. Its ability to maintain structural integrity and resist degradation over prolonged periods under extreme temperatures contributes to its popularity in applications involving elevated heat.

Additionally, the alloy offers good weldability and fabricability, allowing for the manufacture of complex components and structures tailored to specific industrial requirements.

Similarities Between Inconel 625 and 825

  1. Both alloys exhibit excellent resistance to corrosion, including oxidation and chloride stress-corrosion cracking.
  2. They maintain their strength at high temperatures, making them suitable for applications in high-temperature environments.

Difference Between Inconel 625 and 825


  • Inconel 625 is a nickel-based superalloy known for its exceptional resistance to corrosion and high temperatures, while Inconel 825 is a nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium.


  • Inconel 625 contains around 58% nickel, 20-23% chromium, 8-10% molybdenum, 3.15-4.15% niobium, and traces of other elements such as iron, manganese, silicon, and carbon, while Inconel 825 contains approximately 42% nickel, 20-23.5% chromium, 2.5-3.5% molybdenum, 1.5-3% iron, 1-2.5% copper, and smaller amounts of titanium and other elements.


  • Inconel 625 is commonly used in aerospace, marine, chemical processing, and oil and gas industries for applications such as turbine blades, exhaust systems, and seawater components. On the other hand, Inconel 825 is widely used in chemical processing, pollution control, and marine applications for equipment such as heat exchangers, tanks, and piping systems.


Inconel 625 and 825 are both highly versatile nickel-based superalloys with exceptional resistance to corrosion and high temperatures. While Inconel 625 is characterized by its nickel-chromium-molybdenum composition, favored in aerospace and marine applications, Inconel 825 stands out for its nickel-iron-chromium base with added molybdenum, copper, and titanium, ideal for chemical processing and pollution control. Despite the compositional difference between Inconel 625 and 825, both alloys offer remarkable mechanical strength, weldability, and fabricability, making them indispensable in industries where durability and reliability are paramount. Inconel 625 and Inconel 825 continue to play essential roles in shaping technological advancements across various sectors worldwide.

FAQ: Inconel 625 and 825

1. What is the strongest INCONEL alloy?

  • INCONEL alloy 725, evolved from INCONEL alloy 625, stands out as one of the strongest INCONEL alloys. It offers enhanced strength and corrosion resistance, making it ideal for demanding applications where durability and reliability are crucial.

2. What is INCONEL 825 used for?

  • INCONEL 825 is used across several industries for its excellent corrosion resistance. It is commonly found in chemical processing, pollution control, oil and gas recovery, acid production, pickling operations, and nuclear fuel reprocessing. This alloy’s ability to withstand harsh environments makes it valuable for applications requiring durability and reliability.

3. What is INCONEL alloy 625 used for?

  • Alloy 625 is extensively used in aircraft ducting and exhaust systems, engine thrust-reverser systems, turbine shroud rings, bellows, and expansion joints. Additionally, it serves in the manufacturing of gaskets, damper seals, and components for motorsport exhaust and clamps.

4. Is Inconel 625 and alloy 625 the same?

  • Yes, “Inconel 625” and “Alloy 625” are synonymous terms to describe the same material. They both refer to a nickel-based alloy with excellent corrosion resistance and high-temperature strength properties.

5. Why use Inconel 625?

  • Inconel 625 is selected for its high strength and excellent fabricability, which includes ease of joining and exceptional corrosion resistance. These qualities make it a versatile choice for various applications, especially in industries requiring durability, reliability, and resistance to corrosion in harsh environments like aerospace, marine, chemical processing, and nuclear industries.

1. “Inconel 625.” Wikipedia. Wikipedia Foundation.

Image Courtesy:

1. “Cladding-Auftragschweißung in einem Rohr mit Inconel 625” By JP1308 – Own work (CC BY-SA 4.0) via Commons Wikimedia

About the Author: Hasini A

Hasini is a graduate of Applied Science with a strong background in forestry, environmental science, chemistry, and management science. She is an amateur photographer with a keen interest in exploring the wonders of nature and science.

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