Inconel 625 is a nickel-chromium alloy that offers superior strength, excellent fabrication characteristics, and remarkable corrosion resistance. It has a wide range of applications due to its high-temperature performance capabilities. This alloy is composed of 58% nickel, 20-23% chromium, molybdenum, niobium, and trace amounts of iron, manganese, and silicon.
Table of Contents
- Inconel 625 Chemical Composition
- Properties of Inconel 625
- Heat Treatment of Inconel 625
- Corrosion Resistance of Inconel 625
- Applications of Inconel 625
- Welding and Fabrication of Alloy 625
Inconel 625 Chemical Composition
Chemical composition of Inconel 625
Inconel 625 is a nickel-chromium-molybdenum alloy with excellent resistance to a variety of corrosive media and high-temperature environments. It has a low carbon content, which provides superior resistivity to carburisation and oxidation. The composition of Inconel 625 typically consists of 58% nickel, 20–23% chromium, 9–11% molybdenum, 3.15–4.15% niobium, 0.40 max% manganese, 0.50 max% iron, 0.10 max% carbon, and traces of other elements as sulfuric and silicon. This alloy has good weldability with strong joints due to its low carbon content.
Alloying Elements and their effects
Nickel is the primary element in INCONEL® 625 alloy which gives it superior corrosion resistance against many acids and other corrosive media. Nickel also increases the strength and toughness of the alloy making it ideal for demanding applications like gas turbines, rocket engines and other aerospace components. Chromium gives the alloy oxidation resistance at higher temperatures while molybdenum adds resistance to pitting from chloride ions. Niobium improves creep strength while iron helps maintain ductility at elevated temperatures. Finally, manganese is added to increase hardenability which helps prevent embrittlement when welding or forming complex shapes.
Properties of Inconel 625
INCONEL® alloy 625 is a non-magnetic, nickel-chromium superalloy with excellent strength and high corrosion resistance. With its superior oxidation and scaling resistance at higher temperatures, Inconel 625 can withstand extreme temperatures up to 1800°F (982°C). Its excellent fabricability makes it an ideal choice for welding and brazing applications.
Physical Properties: Alloy 625 has a density of 8.4 g/cm3, with an electrical resistivity of 1.7 μΩ-m at 20 °C. It also has a melting point range of 2450–2625 °F (1340–1440°C). The thermal conductivity of Inconel 625 is 11.2 W/m-K.
Mechanical properties (tensile strength, yield strength, elongation)
Inconel 625 is a nickel-chromium alloy with high strength, excellent Fabrication, and outstanding corrosion resistance. It has superior properties thus tensile strength of up to 895 MPa (130 ksi), yield strength of up to 550 MPa (80 ksi) and elongation of up to 34%.
High-temperature properties of Inconel 625
The alloy also provides superior corrosion resistance in many media, as sea water and hydrofluoric acid. UNS N06625 has a service temperature range from cryogenic to 1800°F (982°C), making it a highly durable material suitable for use in extreme environments. With its unique combination of properties, INCONEL® alloy 625 is the perfect material for long Heat Treatment of Inconel 625.
Heat Treatment of Inconel 625
Annealing and Solutionizing processes
Annealing is a process by which Inconel 625 is heated in the range of 1700-1850°F (927-1010°C) and cooled slowly to soften it for further processing or formability. It also removes internal stresses caused by prior machining, welding or cold working processes. The part should then be rapidly cooled, usually by water quenching or oil quenching. This process increases toughness and reduces hardness while preserving corrosion resistance.
Solutionizing is another heat treatment process for Inconel 625 that improves the material’s structural integrity while increasing its strength and improving fatigue performance. It involves heating the material to 1850-2000°F (1010-1093°C), depending on specific alloy requirements, followed by rapid cooling with water or air. This creates a homogenous structure throughout the alloy where all atoms are in their correct atomic positions. This helps to improve its mechanical properties without reducing its corrosion resistance or other desirable qualities as fabrication and weldability.
Precipitation hardening of Inconel 625
It also has excellent weldability properties that make it suitable for welding operations. Inconel 625 is an ideal material choice for industries that require reliable performance and high-temperature resistance. With its superior mechanical and corrosion-resistant properties, Inconel 625 is an excellent all-around solution for many challenging projects.
Corrosion Resistance of Inconel 625
Due to high chromium content provides exceptional resistance to oxidation, while its molybdenum content enhances its ability to resist pitting and crevice corrosion. The alloy also contains niobium which further improves its resistance to stress-corrosion cracking.
Additionally, UNS N06625 has superb weldability characteristics due to its low carbon content which suppresses carbide precipitation during welding. The inconel alloys has an impressive strength-to-weight ratio and its ultimate tensile strength makes it suitable for many high-temperature applications, with service temperatures ranging from cryogenic to 1800°F (982°C).
Applications of Inconel 625
Industrial Applications of Inconel 625
INCONEL® 625 is a highly versatile nickel-chromium alloy that has many industrial applications. It is renowned for its high strength, & outstanding corrosive environments. Nickel 625 is often used in aerospace, marine, and chemical processing industries due to its ability to maintain its strength and properties even at high temperatures.
Use in high-temperature environments (e.g., aerospace, power generation)
In aerospace engineering, INCONEL® 625 is used in aircraft components such as exhaust systems and structural supports due to its strength and ability to withstand high temperatures. It also finds uses in fuel systems where it prevents corrosion from chemicals or water vapour condensation.
Marine and offshore applications
In marine applications, INCONEL® 625 can be used to manufacture fasteners such as bolts and nuts that are resistant to corrosion from saltwater exposure. It is also commonly employed in the production of valves, pumps, dampers, and other components that require long-term protection against corrosion.
The chemical processing industry also makes extensive use of INCONEL® 625 for valve bodies and flanges because it resists aggressive acids such as sulfuric acid and hydrochloric acid. It can also be used in heat exchangers that are exposed to steam or hot water with corrosive properties.
Welding and Fabrication of Inconel 625
Inconel 625 can be welded using conventional welding methods such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), shielded metal arc welding (SMAW), and electron beam welding (EBW). However, certain steps need to be taken before any of these processes can take place. Proper cleaning of the surface is essential; any dirt or debris needs to be removed for the welds to hold properly. Additionally, preheating the material before welding helps reduce stress concentrations on the weld sites while eliminating hydrogen embrittlement.
Fabrication techniques such as cutting, bending, forming, machining, and stamping can all be used with Inconel 625. High-speed tools are recommended at speeds up to 500 m/min when machining this alloy since its tough nature can produce wear on cutting edges quickly. Specialised tool coatings may also be needed to reduce this wear even further. Overall UNS N06625 is a great choice for those who need strong parts that are resistant to corrosion and oxidation in extreme temperatures. With proper preparation and care during the fabrication process, this nickel-chromium alloy will provide reliable performance for many years.
Welding processes and techniques of Alloy 625
Welding of Inconel® alloy 625 has proven difficult due to its high nickel content because it tends to harden quickly when exposed to heat. However, by taking the appropriate steps during welding preparation and maintaining the proper welding conditions, welders can successfully join this material with a sound welded joint that meets specific requirements.
Precautions and Challenges in Welding Alloy 625
The alloy is nonmagnetic and offers a low coefficient of thermal expansion. It has excellent fatigue strength and stress-corrosion cracking resistance to chloride ions. Additionally, UNS N06625 provides outstanding formability and weldability, making it the material of choice for many applications in various industries including aerospace, oil drilling, nuclear energy production, marine engineering and chemical processing
