Inconel 625, also known as Alloy 625, is a remarkable nickel-chromium-molybdenum alloy that offers exceptional corrosion resistance, superior strength, and excellent weldability.
With its wide range of applications in various industries, including aerospace, chemical processing, oil and gas, and nuclear power generation, this alloy has become a go-to choice for many critical applications.
In this blog post, we will delve into the characteristics, properties, and applications of Inconel 625, shedding light on its remarkable versatility.
Inconel 625 Material Specification
Material Specification:
- Material: Inconel 625
- UNS Number: N06625
- Standard: ASTM B443
- Other Specifications: AMS 5599, AMS 5666, NACE MR0175/ISO 15156
Equivalent Grades:
- UNS N06625
- Werkstoff Nr. 2.4856
- AFNOR NC22DNB4M
- JIS NCF 625
- GOST ХН75МБТЮ
- BS NA21
- EN NiCr22Mo9Nb
Inconel 625 chemical Properties
The chemical properties of Inconel 625 alloy are:
| Chemical Element | Composition (mass %) |
|---|---|
| Carbon (C) | ≤ 0.12 |
| Chromium (Cr) | 20 – 23 |
| Nickel (Ni) | ≥ 58 |
| Iron (Fe) | 5 % max. |
| Manganese (Mn) | ≤ 0.5 |
| Silicon (Si) | ≤ 0.5 |
| Molybdenum (Mo) | 8 – 10 |
| Phosphorus (P) | ≤ 0.015 |
| Sulfur (S) | ≤ 0.015 |
| Titanium (Ti) | ≤ 0.40 |
| Niobium (Nb) + Tantalum (Ta) | 3.15 – 4.15 |
| Aluminum (Al) | ≤ 0.4 |
Inconel 625 Alloy Mechanical Properties
The mechanical properties of Inconel 625 alloy:
| Mechanical Property | Typical Value |
|---|---|
| Tensile Strength | 120 – 160 ksi |
| Yield Strength | 60 – 120 ksi |
| Elongation | 30% – 40% |
| Hardness (Rockwell C) | 30 – 35 HRC |
| Impact Toughness | Retains good toughness down to -320°F (-196°C) |
- Tensile Strength: The typical tensile strength of Inconel 625 alloy ranges from 120 ksi (827 MPa) to 160 ksi (1103 MPa).
- Yield Strength: The typical yield strength of Inconel 625 alloy is approximately 60 ksi (414 MPa) to 120 ksi (827 MPa).
- Elongation: The typical elongation of Inconel 625 alloy is around 30% to 40%. This means that the material can undergo significant deformation before breaking.
- Hardness: The typical hardness of Inconel 625 alloy, measured using the Rockwell C scale (HRC), is in the range of 30 to 35 HRC.
- Impact Toughness: Inconel 625 alloy exhibits excellent impact toughness, even at low temperatures. It retains good toughness down to temperatures as low as -320°F (-196°C).
Corrosion Resistance
One of the standout features of Inconel 625 is its outstanding corrosion resistance in diverse environments. It exhibits remarkable resistance to reducing and oxidizing acids, salts, alkalis, organic acids, and even seawater.
The high molybdenum content in this alloy provides protection against localized corrosion, including pitting. This property makes it highly suitable for applications where corrosion resistance is of paramount importance.
Elevated Temperature Resistance
Inconel 625 showcases excellent oxidation and scaling resistance at elevated temperatures up to 1800°F (982°C). Furthermore, it demonstrates superior resistance to recurrent heating and cooling cycles, making it an ideal choice for high-temperature applications that involve extreme thermal conditions.
Mechanical Properties
The addition of molybdenum and niobium enhances the mechanical properties of Inconel 625. It can be supplied in different conditions, including annealed (Grade 1), solution annealed (Grade 2), or strengthened through the pilger process.
The alloy exhibits excellent impact toughness, even at extremely low temperatures as low as -320°F. This attribute ensures its reliability and performance in demanding environments.
Heat Treatment of Inconel 625
Inconel 625 typically does not require heat treatment for strengthening. However, solution annealing is commonly performed at temperatures ranging from 2000°F to 2200°F (1093°C to 1204°C) to achieve optimal creep resistance in applications above 1100°F.
Annealing at temperatures between 1600°F and 1900°F (871°C and 1037°C) is recommended for applications below 1100°F or to prevent sensitization during welding. Stress relieving is also performed to reduce residual stresses from fabrication.
Workability
In its annealed condition, Inconel 625 demonstrates good hot and cold workability. Hot working is typically conducted above 1600°F (871°C) to ensure sufficient ductility, while cold work is performed below 1200°F (649°C). This versatility in workability allows for easier shaping and fabrication of components.
Applications
The versatility of Inconel 625 makes it suitable for a wide range of applications across various industries. In the chemical process industry, it is extensively used for wetted surfaces of oil and gas equipment to protect against corrosion from aggressive media such as H2S, CO2, and chlorides.
Its excellent oxidation resistance makes it a preferred choice for heat-treating fixtures, furnaces, and incinerators. Additionally, Inconel 625 finds applications in aerospace, electronics, food processing, and nuclear power generation.