Do you mean Inconel 718?  I am not familiar with Inconel 618.  Alloy 718 is used in both aerospace and oil & gas applications.  You can obtain more information on this grade from Special Metals:

http://www.specialmetals.com/products/publication/tech_bulletin_718.pdf

Also, Allvac and Carpenter produce this grade.  More information from these companies are available using the following links:

http://www.allvac.com/allvac/pages/PDF/tech/NI-105%20718.pdf

http://www.cartech.com
Click on Technical Information then Alloy Name then Pyromet Alloy 718

Hi sayeeprasadr,
Inconel 718 (In718) can be used for both applications, due to the characteristics of supperalloys : they are light and very resistant to high temperature environments and to creep. Basically used as turbine blades, but can be used in other parts of turbine too. In the case of blades, what will change are the dimensions for a gas turbine, for example and for a turbine used in a aerospace craft and also if they will be internally refrigerated or not. Also, depending on the environment, petrochemical applications will require those alloys to be coated, in order extend life. Turbines that are used for piping gas+fluid from off-shore rigs are the most common applications for those superalloys (so called due to the numerous elements preset in it).
A good reference book for you to start with is:
"Superalloys - Chester T. Sims" It gives all the information on this subject.
Also, you should check at the Metals Handbook for a general overview of superalloys, but the book above is by far the best reference.
In case of further questions, let me know.
acr2003

Sorry,
Typo mistake, inconel 718 is what I meant! Got the details from the link you provided TVP. Thanks a lot! But data sheets apart, do the conditions of the HT and hence the properties or even the microstructure vary for the material when used for aerospace viz a viz oil & Gas?

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
End of all knowledge is the attainment of immortality!

The chemistries for the alloy 718 materials used for gas turbine applications and down hole applications are the same.  Some end users may of course place tighter controls on various elements in some cases.  

You are correct that the heat treatments are different.  In the case of 718 going into aerospace applications.  Typically the material is heat treated by annealing at 1700-1850F air cool or faster, followed by a aging treatment at 1325F for 8 hours, furnace cool to 1150F, hold at 1150F for a total aging time of 18 hours.  Typically this produces a hardness of 42-44 Rc.  There is another heat treatment also used for some engine components involving higher temperatures.  

Aging treatments for downhole components are limited to a maximum hardness of I believe 40 Rc according to the NACE MR0175 specification to decrease risk of sulfide stress corrosion cracking.  As a result, the heat treatment used for this application is shorter in duration and the annealing and aging are done at slightly higher temperatures.  One I have seen is anneal at 1875F rapid cool and age at 1450F.  

The aerospace heat treatments can be found in the 718 data sheet at

http://www.rolledalloys.com/techcenter/hightemp/RA718pg6,7.pdf

AMS specification AMS 5562L and AMS 5664E also cover the heat treatments and properties of alloy 718 bar products.  I believe AMS specifications are available from the Society of Automotive Engineers at http://www.sae.org

NACE MR0175 is available at http://www.nace.org