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An effort to study the heat treatment methods and resultant mechanical properties of Russian powder metallurgy (P/M) alloy EP741NP has been undertaken. This effort has involved the detailed assessment of microstructures and mechanical properties from a sample of a production turbine engine disc as well as the manufacture, processing and characterization of two developmental lots of P/M EP741NP material processed by atomization, extrusion, isothermal forging and heat treating. The effects of processing and composition on the structure and properties of powder metallurgy superalloys have been studied as part of an ongoing effort to compare and contrast the physical metallurgy and mechanical property capabilities of EP741NP and similar alloys, such as AF115, AF21DA6, Alloy-10 and LSHR. From detailed characterization of developmental EP741NP heats, it has been determined that the published Russian heat treatment for EP741NP was not the thermal cycle used to produce the EP741NP material extracted from a production disc. The identified heat treatment route was subsequently utilized to process additional developmental material. The microstructure and mechanical properties from resultant material matched well with the previously evaluated production material. The thermal process for this alloy is aimed at very high temperature applications where notched stress-rupture and long-life stability are critical.

Users of 71 8 for oil field applications generally require a minimum 0.2% R.T. tensile strength of 120 ksi. and hardness in the range of Rc 30-40.

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