Kickel base alloq 706 has estensi~e application historq for rotating parts in land based gas turbines combining high strength and toughness o\ er the \\hole range of the s e n ice temperatures. Thls material is tqpicallj finish forged in a closed die press. The size of parts needed for the land-based gas turbines is Lrerq large requiring the use of the largest forging presses in the norld. Finish forging of alloq 706 and other nickel-based alloj s for rotating parts in gas turbines require homogenous structure and properties throughout the forging. Manj evperts considered that open die forging process u ould not be able to achieve such uniformlt>. ,411 experiment mas done to determine if a \\ell-controlled open die forging process could achie\ e the necessarj uniformit! in microstructure and properties for a large gas turbine part made of a l l o~ 706 I'his paper mill describe the details of the forging and heat treatment process. Results of mechanical tests and metallographic examination \+ill be also discussed. Issues with process control and repeatability for open die forging are also discussed.

This paper focuses on metallurgical issues and manufacturing of impellers for an integrally geared 2-stage expander for a corrosive hot-gas application. The design employs the largest single piece forging in Alloy 718 material for use in the low pressure stage impeller. Alloy 718 was chosen due to the combination of best corrosion resistance and mechanical properties. With this single piece forging it is possible to manufacture very large impellers in a "non-welddesign". Information about development of the disc production, the manufacturing process and mechanical properties are presented.