It is possible to measure strength by tensile strength, corrosion resistance, and melt resistance. While stainless steel has a tensile strength of 73.2 ksi, Inconel 625® can maintain that strength at higher operating temperatures with a tensile strength range of 103 - 160 ksi. 

Although exact measurements vary, reported statistics state that Inconel melts between 2,350°F and 2,460°F (1,290°C and 1,350°C). Inconel 625® has a lower melting point than stainless steel, but it is stronger than stainless steel at high temperatures as well as more resistant to scaling and oxidation.

The high strength rating, resistance to temperature and corrosion of Inconel 625, a nickel-chromium-molybdenum alloy, makes it a high-performance alloy. Nickel makes up the majority of this superalloy, followed by chromium, molybdenum, niobium, iron, tantalum, and cobalt, as well as manganese, silicon, aluminium, and titanium (58% minimum).

Due to its high resistance to corrosion and extreme pressures, Inconel is considered a superalloy. In sterile manufacturing or medical applications, Inconel uses, stainless steel alloys are often more appropriate. Inconel® is a superalloy that is better suited to heat treatment and other high-temperature processes. 

As a nickel-based superalloy, Inconel Alloy 625 (UNS designation N06625) exhibits excellent strength and resistance to elevated temperatures as well as exceptional corrosion and oxidation resistance. Its ability to withstand high stress and a wide range of temperatures, both inside and outside of water, as well as resist corrosion when exposed to highly acidic environments, makes it an ideal choice for nuclear and marine applications.

A material called Inconel 625 bar was developed in the 1960s in order to create a material that could be used for steam pipes. As a result, some modifications have been made to its original composition, making it even more creep-resistant and weldable than it was originally. As a result, Inconel 625 bar has been used in a wide variety of industrial applications, such as the chemical processing industry, as well as for marine and nuclear applications to produce pumps, valves, and other equipment under high pressure.

Because Inconel 625 bar contains high levels of Niobium (Nb) and is exposed to harsh environments and high temperatures, its weldability has been questioned. Inconel 625 was tested for its weldability, tensile strength, and creep resistance, and was found to be an ideal welding material. Also known as Haynes 625, Nickelvac 625, Nicrofer 6020, Altemp 625, and Chronic, Inconel 625 bar has many other names.

The high strength rating, resistance to temperature, and corrosion of Inconel 625, a nickel-chromium-molybdenum alloy, make it a high-performance alloy. Nickel makes up the majority of this superalloy, followed by chromium, molybdenum, niobium, iron, tantalum, and cobalt, as well as manganese, silicon, aluminum, and titanium (58% minimum).

In this second product focus feature, we’ll continue to explore how INCONEL 625’s unique characteristics are being employed to generate power and energy, as well as its surprising applications in the marine and aerospace industries - and even how it may be used in the future.

The waste-to-energy process

The combustion of refuse to generate steam for heat or power generation applications is a key part of environmentally sound refuse disposal programs. Municipal waste contains a high level of halides, which can be highly corrosive at high temperatures (up to 0.5% in some cases).

Since nickel-based alloys have been proven to be remarkably resistant to halogen attacks, INCONEL 625 pipe contains a minimum nickel content of 58%. Because of this, alloy 625 has long been the most commonly used alloy in refuse boilers. INCONEL 625 alloy is generally considered to outperform steel tubing in these kinds of environments by at least a factor of 10, as its corrosion rate is less than 0.25mm/y (10 mpy).

The Sea Water to the Aerospace

Seawater is another climate where INCONEL 625 seamless pipes excel. As a result of its high nickel content, it is highly resistant to chloride ion stress corrosion, and combined with its high tensile strength and freedom from local attacks (pitting and crevice corrosion), it is the perfect material for many marine applications. INCONEL 625 is commonly used in steam liner bellows, undersea communication cables, auxiliary propulsion motors, and quick-disconnect fittings for submarines.

As well as displaying high tensile strength, INCONEL 625 also has high creep strength, high rupture strength, and excellent weldability. These features make it equally suited to aerospace applications, which include ducting and exhaust systems, turbine shroud rings and seals, and thrust reverser systems.

The Future of INCONEL 625

INCONEL 625 alloy is likely to play a significant role in the future growth of municipal waste-to-energy systems and refuse-derived fuel plants as we strive to reduce the environmental impact of energy generation and waste disposal.

What’s more, as solar energy becomes increasingly popular, INCONEL 625 pipe may see the further application in solar power plants. Many use hot salt, which is heated to between 621 and 635°C (1150-1175°F) by the sun, to operate electric generators at night. The eutectic mixture of potassium and sodium nitrate used in this process makes for a corrosive environment that requires tubing made from the extremely durable INCONEL 625.

Nuclear technology

Nuclear reactors require Inconel 625 for their strength, corrosion resistance, and stress resistance, especially in the control rod and reactor core.

Industrial processing

Due to its easy manufacturing capabilities and resistance to heat and corrosion, this alloy is a valuable component in manufacturing equipment such as vessels, heat exchangers, valves, and fluid delivery systems.

In addition to its resistance to potable and salted water, Inconel alloy 625 can also be used in pipelines for collecting sour gas due to its high resistance to salt. For a more economical option, pipelines can be designed with Inconel alloy 625, or clad in the alloy.

In addition to heat exchangers for seawater, power plants, and offshore services, the alloy is also useful in the production of mooring cables, boat propeller blades, propulsion engines, control and fittings for submarine transducers, and exhaust ducts for utility boats. Additionally, it can be used in submerged control components, electrical cable connectors, and oceanographic instrument components.