PHYSICAL METALLURGY OF ALLOY 718

Abstract : This report deals with the physical metallurgy of Alloy 718. Since Alloy 718 was first introduced, it has broadened its areas of application. Primarily, it was intended for use at medium temperatures, 1300 F at most, its main applications being in lightweight welded frames and other assemblies in aircraft turbojet engines. Its good properties in the range of temperatures from -423 to 1300 F make it especially suitable for use in the LOX-LH4 rocket engines. In these applications, Alloy 718 is used for the fuel/oxidizer injector plates, forged rings, thrust chamber jackets, turbine wheels, bellows, and tubing. This report presents information on the effect of composition and heat treatment on mechanical properties; trends in specifications for Alloy 718; microstructure and microconstituents of the alloy and the strengthening mechanism. No attempt has been made to present a complete compilation of design properties in this report.