Minoru Nobuki1 and Atsushi Oguchi1
1National Research Institute for Metals, Tokyo
In order to study the hot workability of heat resistant superalloys, compressive tests and forging tests have been conducted at high temperatures up to 1600 K for as-cast materials of Inconel 713C and More 2. Deformability, flow stress and microstructure of deformed material have been examined from the viewpoint of the behaviour of precipitates and inclusion particles. In 713C, a large ductility was obtained in a temperature range of about 50 K at low strain rates. This temperature range corresponded with that of solution of γ' phase and of recrystallization. At lower temperatures, the ductility was decreased by the fracture of carbides and at higher temperatures by the local grain boundary melting. In the case of More 2, no remarkable increase in ductility was seen. In both materials, the hard and brittle particles were seen to be the cause of decrease in ductility but the lamellar eutictic carbides did not act as the sites of crack initiation. The behaviour of solution and precipitation of γ' phase and carbides in reheating depended strongly upon the amount of plastic deformation. By forging with lateral compressive stress components, the forging ratio more than 7 was obtained for both materials without cracks.
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