Application and development trend of nickel-based alloy Inconel 600

Inconel 600 is a nickel-based alloy known for high-temperature strength and resistance to oxidation and corrosion. Its nickel-chromium-iron base limits chloride stress corrosion cracking, so the alloy holds up in aggressive industrial media. Where the alloy meets a bolted joint, the sealing element has to match it: the flange gaskets used with this material cover corrosive, high-temperature service.

Composition, Structure and Physical Properties

Inconel 600 is primarily nickel, chromium and iron. High nickel content gives resistance to chloride ion stress corrosion cracking, while chromium provides oxidation resistance. The alloy has a face-centered cubic lattice structure. The table below lists the chemical composition limits.

Values in percent: Ni is specified as a 72 % minimum, Cr and Fe as ranges, and the remaining elements as maximum limits.

• Density: 8.4 g/cm³.
• Melting range: 1370–1425 °C.
• Annealed condition: tensile strength Rm 550 N/mm², yield strength Rp0.2 240 N/mm², elongation A5 30 %, hardness ≤195 HB.
• Solution-treated condition: Rm 500 N/mm², Rp0.2 180 N/mm², elongation A5 35 %, hardness ≤185 HB.

Corrosion Resistance and Service Limits

Alloy 600 resists a wide range of corrosive media. Its chromium content makes it more corrosion resistant than Nickel 99.2 (Alloy 200) and low-carbon Nickel 99.2 (Alloy 201) under oxidizing conditions, while the higher nickel content keeps it resistant in reducing conditions and alkaline solutions and helps prevent chloride stress corrosion cracking. In organic acids such as acetic, formic and stearic acid the resistance is very good; in inorganic acids it is moderate. In the high-purity water of primary and secondary nuclear reactor circuits the alloy shows excellent resistance. Its most outstanding property is resistance to dry chlorine and hydrogen chloride at service temperatures up to 650 °C.

• Good resistance to reducing, oxidizing and nitriding media.
• Resistance to stress corrosion cracking at room and elevated temperature.
• Excellent resistance to dry chlorine and hydrogen chloride gas.
• Good mechanical properties at sub-zero, room and high temperature.
• Good creep rupture strength; recommended for service environments above 700 °C.

At high temperature, annealed and solution-treated material resists oxidation scaling and keeps high strength in air. It also withstands ammonia and nitriding or carburizing atmospheres, but when oxidizing and reducing conditions alternate, some oxidizing media can still corrode the alloy.

Applications and Development Trends

Inconel 600 is used wherever hot, corrosive media meet plant equipment. The main application areas are:

• Thermocouple sheaths in corrosive atmospheres.
• Vinyl chloride monomer production, resisting chlorine, hydrogen chloride, oxidation and carburization.
• Uranium conversion to hexafluoride, resisting hydrogen fluoride corrosion.
• Production and use of corrosive alkali metals, especially sulfide-bearing environments.
• Titanium dioxide production by the chloride process.
• Organic and inorganic chlorides and fluorides, resisting chlorine and fluorine corrosion.
• Nuclear reactors and their high-purity water circuits.
• Retorts and parts in heat treatment furnaces, especially in carburizing and nitriding atmospheres.
• Catalytic regenerators in petrochemical plants above 700 °C, for longer service life.

In the fastener field, Inconel 600 screws and bolts are used in aerospace, nuclear energy, chemical processing and heat treatment equipment. On high-temperature lines they are mounted on pipe flanges and other bolted joints handling corrosive media: engine and hot gas-path components, reactor bolting, petrochemical service with chloride media, and furnace fasteners exposed to oxidation at temperature.

Demand for Inconel 600 keeps rising as service conditions get hotter and more corrosive. The main development trends are:

• Higher-performance alloy grades for more demanding service conditions.
• Additive manufacturing and other advanced processes, raising efficiency and lowering production cost.
• Cleaner production and better recyclability as environmental rules tighten.
• Wider use in new sectors such as aerospace and new energy vehicles.

FAQ

What is Inconel 600?

Inconel 600 is a nickel-based alloy of nickel, chromium and iron with a face-centered cubic lattice structure. It combines high-temperature strength with resistance to oxidation and corrosion.

What is the service temperature range of Inconel 600?

It resists dry chlorine and hydrogen chloride up to 650 °C, and its good creep rupture strength makes it recommended for working environments above 700 °C.

Which acids does Inconel 600 resist?

Resistance is very good in organic acids such as acetic, formic and stearic acid, moderate in inorganic acids, and excellent in the high-purity water of nuclear reactor circuits.

How do annealed and solution-treated Inconel 600 differ?

Annealed material gives Rm 550 N/mm², Rp0.2 240 N/mm², elongation A5 30 % and ≤195 HB. Solution treatment lowers strength to Rm 500 N/mm² and Rp0.2 180 N/mm² but raises elongation to 35 % with ≤185 HB.