INCONEL "QUEEN ALLOY"

Saturday, 25 May 2013 | Por Muelles Crom |

INCONEL is a registered trademark of Special Metals Corporation covering base alloys, nickel-chromium, covering a wide range of compositions and properties.

The combination of nickel and chromium in the alloys provides resistance to both reducing and oxidizing corrosive solutions. Nickel and chromium also act together to resist oxidation, carburization, and other forms of deterioration at high temperatures. These alloys do not become brittle at cryogenic temperatures, have good tensile strength and fatigue at moderate temperatures, and exhibit excellent flow properties and fracture resistance at high temperatures. The technical level necessary to work Inconel is not available to smaller manufacturers or low professional level..

The applications of these alloys are very broad : heat treatment vessels , turbines , springs Hi -tea, aviation, nuclear power generation , etc. .

COMPOSITION

The various Inconel alloys have a wide variety of compositions, but in all the predominant nickel, chromium as a second element . Most of them in the basic features of the system nickel - chrome are increased by the addition of other elements. Some of the alloys increase the tensile strength by the addition of aluminum, titanium and niobium. Others contain cobalt, copper, molybdenum or tungsten to improve mechanical strength specific attributes or corrosion . Alloys also contain iron in amounts ranging from 1% to over 20% . In most cases the dominant effects in the properties due to the alloying , except iron.

PROPERTIES

Inconel alloys are materials resistant to corrosion and oxidation suitable for service in extreme environments. When heated , Inconel forms a thin and stable passive oxide layer that protects the surface from further attacks . Inconel maintains its strength over a wide temperature range , which is attractive for high-temperature applications in which the aluminum and steel succumb to creep as a result of thermally induced crystalline vacancies . The high temperature resistance of Inconel develops through precipitation hardening and solid solution hardening , depending upon the alloy . In varieties precipitation hardening or aging , small amounts of Nb are combined with Ni to form the intermetallic compound Ni3Nb or double gamma prime ( γ '') . This compound forms small cubic crystals which inhibit slippage and effectively creep at elevated temperatures.

MACHINING

Inconel is a hard metal mold and machined using traditional techniques due to rapid cold hardening . After the first machining pass , the cold hardening tends to elastically deform the workpiece or tool in the following passes. For this reason, the age hardened as Inconel 718 are machined using an aggressive but slow cut with a hard tool , minimizing the number of passes required .

UNIONS

Inconel welding is difficult due to microstructural segregation of alloying elements in the HAZ ( heat affected zone ) . However, various alloys have been designed to overcome these problems . The most common form Inconel welding is TIG welding with filler metal fitting .

APPLICATIONS

The Inconel could be often found in extreme environments. It is common in blades , seals , springs and gas turbine burners , as well as turbocharger rotors and seals , high temperature fasteners , pressure vessels , heat exchanger tubing , steam generators in pressurized water nuclear reactors and exhaust systems of Formula One and jet propulsion. North American Aviation built aircraft fuselage X -15 rocket with Inconel alloy known as " Inconel X " .

A bad job by inexperienced Inconel can be catastrophic for the application where it was intended and the consequences can be fatal .

INCONEL ALLOYS

Some Inconel alloys are:

Inconel 600 : Hardened solid solution . Inconel 625 : Acid resistant , good weldability. Inconel 690: Low cobalt content for nuclear applications . Inconel 718 : Good weldability , hardened by intermetallic compound . Inconel 751: aluminum content increased for an improvement in the tear strength in the range of 1600 F. Inconel 939 : hardened by intermetallic compound , good weldability.