Inconel
Inconel is a registered trademark that refers to nickel-chromium
superalloys with common characteristics. As austenitic nickel alloys,
the Inconel family is also at times referred to as Chronin, Altemp,
Haynes, Nickelvac and Nicrofer. While Inconel alloys can differ widely
in terms of composition, all feature nickel as the highest percentage
element used, with chromium as the second highest percentage.
Some common characteristics of Inconel alloys include corrosion-resistance, oxidation-resistance, the ability to work well in extreme environments and to retain strength at high temperatures. As a result, Inconel alloys are often used for high temperature applications in industries such as:
- nuclear, in which Inconel 718 is often used in nuclear reactors, rocket motors and spacecraft
- chemical for processing equipment
- industrial manufacturing, for all Inconel alloys for use in heat treating equipment such as furnaces and various machines and components such as gas turbine
- marine, for salt corrosion-resistant piping, springs and fastener
- aerospace, where Inconel is used for piping, safety wire, shims and other structural metal on aircrafts
Since Inconel alloys rapidly harden under machining, they can be difficult to shape. Often, the Inconel alloy must be in a solutionized form for machining to occur. However, machining must be done aggressively and using hard tools, such as in welding or brazing stainless steel threaded inserts are commonly used. In addition, the most common welding technique that is used on Inconel alloys is gas tungsten arc welding (GTAW), which is more generally known as tungsten inert gas (TIG) welding. However, recent developments in pulsed micro laser welding are becoming an increasing popular technique for welding Inconel alloys as well.
Each Inconel alloy has its own unique characteristics. As examples, the most commonly used Inconel alloys are:
Inconel 718
It is a nickel-chromium-cobalt alloy that's widely known for its superior metallurgical stability. Inconel 718 alloy is widely used chemical production, power generating plants, gas turbine, combustion cans and ducting. It has high resistance to corrosive aqueous environments and oxidation at high temperatures. The addition of molybdenum and cobalt imparts a solid-solution strengthening. It is easy to fabricate and makes it easy to join metals using conventional welding techniques.
Inconel 617
It is an alloy of Ni, cobalt, chromium, and molybdenum. This exceptional combination improves its strength, oxidation resistance, and metallurgical resistance. The addition of aluminum enhances its resistance to oxidation. It can also resist corrosion even when exposed to different corrosive environments. It is used in ducting, transition liners, petrochemical processing, heat-treating equipment, nitric acid production and gas turbines.
Inconel 601
It is an alloy of Ni, iron, and chromium. It is a versatile engineering material for various applications that require high levels of resistance to corrosion and heat. It has high strength; high resistance to aqueous corrosion and it is readily machined and welded. It has high levels of metallurgical stability and a high-temperature resistance of about 1250°F. It has an adherent layer that is resistant to spalling. Inconel 601 is widely used in fabricated combustion chambers, thermal reactors, insulting cans, and refractory cans.
Inconel 625
58% nickel, 20-23% chromium, 5% iron, 8-10% molybdenum, 3.15-4.15% niobium, 1% cobalt and trace amounts of manganese, aluminum, titanium, silicone, carbon, sulphur and phosphorus.
Inconel 600
72% nickel, 14-17% chromium, 6-10% iron, 1% manganese, and trace amounts of copper, silicone, sulphur and carbon
Inconel 718
50-55% nickel, 19% chromium, 17% iron, 3% molybdenum, 5% niobium, 1% cobalt, 1% aluminum and trace amounts of manganese, copper, titanium, silicone, carbon, sulphur, phosphorus and boron.
Other alloys include 601, 690, 751, 903 and 939.
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