Introduction:
Inconel is a
family of austenite nickel-chromium-based superalloys.Inconel alloys are
oxidation and corrosion resistant materials well suited for service in extreme
environments subjected to pressure and heat. When heated, Inconel forms a thick,
stable, passivating oxide layer protecting the surface from further attack.
Inconel retains strength over a wide temperature range, attractive for high
temperature applications where aluminum and steel would succumb to creep as a
result of thermally induced crystal vacancies. Inconel’s high temperature
strength is developed by solid solution strengthening or precipitation
strengthening, depending on the alloy.
Inconel alloys are
typically used in high temperature applications. It is sometimes referred to in
English as "Inco" (or occasionally "Iconel"). Common trade
names for Inconel Alloy 625 include: Inconel 625, Chronin 625, Altemp 625,
Haynes 625, Nickelvac 625 and Nicrofer 6020.
Usage:
Inconel is often
encountered in extreme environments. It is common in gas turbine blades, seals,
and combustors, as well as turbocharger rotors and seals, electric submersible
well pump motor shafts, high temperature fasteners, chemical processing and
pressure vessels, heat exchanger tubing, steam generators and core components
in nuclear pressurized water reactors,natural gas processing with contaminants
such as H2S and CO2, firearm sound suppressor blast baffles, and Formula One.It
is also used in the turbo system and the exhaust systems of high powered rotary
engined Norton motorcycles where exhaust temperatures reach more than 1,000
degrees C.Inconel is increasingly used in the boilers of waste incinerators.
Alloys of inconel
include:
· Inconel 600:
Solid solution strengthened
· Inconel 625:
Acid resistant, good weldability. The LCF version is typically used in bellows.
· Inconel 690: Low
cobalt content for nuclear applications, and low resistivity
· Inconel 713:
Newly developed alloy
· Inconel 718:
Gamma double prime strengthened with good weldability
· Inconel 751:
Increased aluminium content for improved rupture strength in the 1600 °F range
· Inconel 792:
Increased aluminium content for improved high temperature corrosion properties,
used especially in gas turbines.
In age hardening
or precipitation strengthening varieties, alloying additions of aluminum and
titanium combine with nickel to form the intermetallic compound Ni3(Ti,Al) or
gamma prime (γ’). Gamma prime forms small cubic crystals that inhibit slip and
creep effectively at elevated temperatures.
