Grade |
Density (g/cm3) |
Thermal Conductivity (W.m -1.°K-1) |
Elastic Modulus (GPa) |
Specific Heat (J.kg-1.°K-1) |
Electrical Resistivity (μΩ.cm) |
Inconel 625 |
8.42 |
1354-1413 |
207 |
(0-100°C) |
10.3 |
460 |
No, Inconel 625 is not a stainless steel. It is a high-performance nickel-chromium alloy with properties that surpass stainless steel in several key areas. Nickel Alloy 625 exhibits superior corrosion resistance, greater tensile strength, and remarkable performance at elevated temperatures, making it ideal for extreme environments where stainless steel may fail.
Nickel Alloy 625 is renowned for its exceptional resistance to oxidation and scaling, even at temperatures as high as 1800°F (982°C). This scaling resistance becomes especially crucial in applications involving cyclic heating and cooling, where other materials might degrade over time. The unique combination of elements in Alloy 625, including molybdenum, niobium, and chromium, allows it to withstand severe corrosive environments, such as those found in marine, chemical processing, and aerospace industries.
When comparing Inconel 625 vs. 718, one of the key distinctions is that Nickel Alloy 625 is non-magnetic and has superior oxidation resistance. In contrast, Inconel 718 is an austenitic super-alloy that offers excellent strength and creep resistance under prolonged high-stress conditions. However, for applications requiring non-magnetic properties and resistance to high-temperature oxidation, Nickel Alloy 625 is the preferred choice.
Nickel Alloy 625’s versatility and exceptional performance make it indispensable in a range of industries, including aerospace, marine, and power generation. Its ability to resist corrosion and withstand extreme temperatures ensures its continued use in environments where reliability and durability are critical. This makes Nickel Alloy 625 a superior alternative to stainless steel in specialized applications.
[#corrosion-resistance]Inconel 625 Corrosion Resistance[#corrosion-resistance]
The alloy Nickel Alloy 625 is exceptionally resistant to a broad spectrum of corrosive environments, ranging from highly oxidizing to moderately reducing conditions. This advanced resistance is due to its high alloy content, which enables it to endure the effects of severe corrosive media. In milder environments, such as freshwater, seawater, atmospheric conditions, neutral salts, and alkaline media, or in harsher environments, the carefully balanced composition of Nickel Alloy 625 provides robust protection.
The combination of nickel and chromium in Nickel Alloy 625 enhances its resistance to oxidizing chemicals, while the additional nickel and molybdenum content provide superior performance in non-oxidizing environments. This unique blend ensures its suitability for applications in marine, chemical processing, and power generation industries.
The high molybdenum content of the alloy also offers excellent resistance to pitting and crevice corrosion, making it ideal for environments with localized corrosion risks. Furthermore, niobium stabilizes the alloy during welding, effectively preventing sensitization and protecting it against intergranular cracking.
Another standout property of Nickel Alloy 625 is its immunity to chloride-ion stress corrosion cracking, which makes it highly reliable for use in marine and other chloride-rich environments. This unique feature, combined with its mechanical strength and versatility, makes Nickel Alloy 625 a preferred material for demanding industrial applications.
Inconel 625 Specifications
GRADE |
UNS |
OLD BRITISH |
G0ST |
OR |
AFNOR |
JIS |
INCONEL 625 |
N06625 |
BS |
EN |
XH60BT |
ЭИ602 |
NC22DNB4M |
NCF 625 |
NA 21 |
2.4856 |
[#fabrication-and-heat-treatment]Inconel 625 Fabrication and Heat Treatment[#fabrication-and-heat-treatment]
Alloy 625 can be manufactured through various cold and hot working processes. It resists deformation at hot working temperatures; therefore higher loads are required to form the material. Hot forming should be performed within a temperature range of 1700° to 2150°F. During cold working, the material of Inconel 625 hardens faster than traditional austenitic stainless steel.
The alloy has three heat treatments: 1) solution annealing at about 2200°F and air quench or quicker, 2) annealing at about 1900°F and air quenching or quicker and 3) stress-relieving at up to 1500°F and air quenching. Solution annealed (grade 2) material is commonly used for applications above 1500°F where resistance to creep is important. The soft annealed material is mainly used for low temperatures and has the ideal combination of tensile and rupture properties.
[#weldability]Inconel 625 Weldability[#weldability]
Alloy Inconel 625 is ductile and strong at lower temperatures, it has high strength, fatigue and thermal-fatigue strength, better resistance to oxidation, and excellent weldability and brazeability, thus Inconel 625 is used in a wide variety of industries. Inconel 625 tubing is popularly used in the aerospace industry due to its high tensile strength and weldability.
Welding can be done by gas-shielded processes using tungsten electrodes or consumable electrodes. Post Weld heat treatments of the weld are not necessary to maintain corrosion resistance. Heavy restrained sections can be seamlessly welded and it’s mechanical properties follow the same trends as any base metal properties.
[#applications]Inconel 625 Application[#applications]
Inconel 625 was developed in the 1960s with the sole purpose of crafting a material that can be used to manufacture steam-line piping. Further changes to the Inconel 625 composition have made it to be even more creep-resistant alloy. The application of Inconel 625 has grown in a variety of industries like chemical processing industry, and for marine and nuclear applications to manufacturing pumps, and valves and other high-pressure equipment. Other areas where the alloy is used are:
- Aircraft ducting systems
- Jet engine exhaust systems
- Engine thrust-reverser systems
- Specialized seawater equipment
- Chemical process equipment
NOTE: Inconel 625 is a registered trademark of Special Metals Corporation.