Inconel is Special Metals Corporation registered trademark which refers to an extensive product line of superalloys made from nickel, chromium and austenite. Inconel alloys are usually utilized in high temperature applications. In English, these alloys are sometimes called ìnconel or simply inconel. The common trade names of these super alloys include Nicrofer 6020, Nickelvac 625, Haynes 625, Altemp 625, Chronin 625 and Inconel 625.
Inconel superalloys are known for their outstanding resistance against corrosion and oxidation. They are frequently used in applications that run in harsh environments, especially those who work in high temperatures.
When heated, this highly specialized alloy forms a thick and passivating oxide layer that protects its surface from extreme heat. Regardless of the temperature, Inconel can still retain its strength. This capability allows it to be used in high temperature applications where steel and aluminum canít withstand. It’s remarkable high temperature strength is due to precipitation strengthening or solid solution strengthening. In precipitation hardening and age hardening, nickel and niobium are combined to form Ni3Nb or gamma prime, an intermetallic compound. Gamma prime is responsible for forming small crystals that prevent the alloy from slipping at high temperatures.
Shaping and Machining
Inconel is difficult to shape and machine because of rapid work hardening. After it underwent the first machining process, work hardening plastically deforms either the tool or workpiece on the next processes. As a result, age-hardened Inconels are machined with the use of a hard tool. Using this kind of tool eliminates the need for the Inconels to undergo several processes.
On the other hand, most of the machining may be performed after age-hardening. The external threads are machined using a lathe or by using a screw machine to roll the threads. The holes that have external threads are made by means of brazing or welding stainless steel threaded inserts. Cutting of plate is usually done by using a water jet cutter. Also, internal threads may also be cut by threadmilling. Ceramic cutters are also used to machine Inconel alloys. These tools remove material faster than the carbide cutters.
Due to the microstructural segregation and cracking of alloying components in the heat-affected area, welding Inconel alloys is not an easy task. However, some alloys have been purposely designed to address this problem. The most common welding technique used is gas tungsten arc welding. Moreover, new methods such as the pulsed micro laser welding were used to join alloys.
Inconel alloys are widely used in applications that work in high temperature environment. They are primarily used in gas seals, turbine blades and combustors, as well as turbocharger seals and rotors, high temperature fasteners, motor shafts, pressure and chemical processing vessels, steam generators heat exchanger tubing, and exhaust systems. These alloys are also used in boilers found in waste incinerators.
The Joint European Torus (JET) vessel also makes use of Inconel alloys. Inside this vessel, plasma is heated to a temperature much higher than the heat generated by the sun. A very strong magnetic field protects the vessel from the extreme heat of the plasma.
In aviation, the X-15 rocket aircraft was designed using an Inconel alloy; the X-15 is an experimental aircraft made for the USN, NASA and USAF.