Nickel Based Alloys: Everything you need to know - BorTec

About Nickel-based Alloys

Nickel-based alloys are also referred to as ni-based superalloys due to their outstanding strength, heat resistance and corrosion resistance. The face-centered crystal structure is a distinctive feature of ni-based alloys, since nickel operates as a stabilizer for the austenite.

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Common additional chemical elements to nickel-based alloys are chromium, cobalt, molybdenum, iron and tungsten.

Inconel® and Hastelloy® Nickel-based Alloys

Two of the most established nickel-based alloys families are Inconel® and Hastelloy®. Other notable manufacturers are Waspaloy®, Allvac® and General Electric®.

The most common Inconel® nickel-based alloys are:

• Inconel® 600, 2.4816 (72% Ni, 14-17% Cr, 6-10% Fe, 1% Mn, 0.5%Cu): A nickel-chrome-iron alloy that displays excellent stability on a broad temperature scale. Stable against chlorine and chlorine water.
• Inconel® 617, 2.4663 (Nickel balance, 20-23% Cr, 2% Fe, 10-13%Co, 8-10% Mo, 1.5% Al, 0.7% Mn, 0.7 % Si): This alloy made largely of nickel, chrome, cobalt and molybdenum displays high strength and heat resistance.
• Inconel® 718 2.4668 (50-55% Ni, 17-21% Cr, iron balance, 4.75-5.5% Nb, 2.8-3.3% Mo, 1%Co, ): A hardenable nickel-chrome-iron-molybdenum alloy that is known for its good workability and excellent mechanical properties at low temperatures.

Hastelloy® nickel-based alloys are known for their resistance against acids. The most common ones are:

• Hastelloy® C-4, 2.4610 (Nickel balance, 14.5 – 17.5% Cr, 0 – 2% Co, 14 – 17% Mo, 0 – 3% Fe, 0 – 1% Mn): C-4 is a nickel-chrome-molybdenum alloy that is applied in environments with inorganic acids.
• Hastelloy® C-22, 2.4602 (Nickel balance, 20 -22.5% Cr, 0 – 2.5% Co, 12.5 – 14.5% Mo, 0 – 3% Fe, 0-0.5% Mn, 2.5 -3.5 W): C-22 is a corrosion-resistant nickel-chrome-molybdenum-tungsten alloy that displays good persistence against acids.
• Hastelloy® C-2000, 2.4675 (Nickel balance, 23% Cr, 2% Co, 16% Mo, 3% Fe): C-2000 is used in environments with aggressive oxidants, such as sulfuric acid and ferric chloride.

Improving durability of nickel-based work pieces

Nickel-based alloys are known for their excellent mechanical properties, such as corrosion resistance and high temperature stability. However, almost no work piece can last forever, no matter how splendid the material. To prolong lifespan of parts, nickel based alloys can be treated with BoroCoat®, our diffusion treatment to significantly improve corrosion and wear resistance as well as provide stability against oxidants.

The diffusion layers of BoroCoat® improve surface hardness to up to 2600 HV while maintaining a diffusion layer of 60 µm. The wear resistance is considerably improved, as is proven by the pin on disc test. While the wear depth of untreated nickel-based alloys increases the longer the pin rotates, ni-based alloys with BoroCoat® display consistent low wear depth throughout the test.

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Areas of Application

Alloys with a nickel basis are often used in challenging environments that demand good resistance against high and low temperatures, oxidation/corrosion and high strength. This is why applications include but are not limited to: turbine engineering, power plant technology, chemical industry, aerospace engineering and valves/fittings.

About 60% of the nickel in the world ends up as a component of stainless steel. It is selected because of its strength, toughness, and resistance to corrosion.  Duplex stainless steels typically contain about 5% nickel, austenitics around 10% nickel, and the super austenitics over 20%. Heat resistant grades often contain over 35% nickel.  Nickel-based alloys generally contain 50% nickel or more.

Nickel Alloy Material Properties

In addition to a majority nickel content, these materials and may contain significant amounts of chromium and molybdenum. Nickel-based metals were developed to provide greater strength at high temperatures, and greater corrosion resistance than could be obtained from iron and steel. They are significantly more expensive than ferrous metals; but because of their long life, nickel alloys may be the most cost-effective long term material selection.

Special nickel based-alloys are widely used for their corrosion resistance and properties at dramatically elevated temperature. Whenever unusually severe conditions are expected one could consider these alloys because of their unique resistance properties. Each of these alloys is balanced with nickel, chromium, molybdenum, and other elements.

There are thousands of applications for nickel as a material and nickel-based alloys. A small sampling of those uses would include:

• Defense, especially marine applications
• Energy generation
• Gas turbines, both flight, and land-based, especially for high-temperature exhaust
• Industrial furnaces and heat exchangers
• Food preparation equipment
• Medical equipment
• In nickel plating, for corrosion resistance
• As a catalyst for chemical reactions

It is worth understanding how nickel-based materials may be an effective solution for those applications requiring high temperature corrosion resistance.

For guidance in selecting the appropriate nickel-based alloy in your application, contact us.

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