Isothermal forging of Waspaloy in air with a new die material.

概要

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Isothermal forging of Waspaloy disk was successfully carried out in air by using a new die material, "Nimowal". The forging was done at 1070-1000°C at a strain rate of 10-3s-1 and the solution treatment at 1010-1038°C. Any damage or significant oxidation of the die was not observed. This shows that Nimowal can be practically used as a die material for isothermal forging in air. The weight of the forging stock was reduced and the microstructure of the disks was homogeneous as a whole. The microstructures and the mechanical properties of isothermally forged Waspaloy showed the characteristics compared with the conventionally forged Waspaloy;(1) grain size depended primarily on forging temperature but was not affected by solution treatment temperature, (2) yield strength increased as solution treatment temperature was raised, and(3) creep rupture strength was high.These characteristics were related to the dislocation structure and the volume fraction of coarse γ' particles in the microstructure of isothermally forged Waspaloy. The strengthening mechanism of isothermally forged Waspaloy was studied. The contributions of grain size effect according to the Hall-fetch relationship, the Orowan mechanism of bypassing of coarse γ' particles, the antiphase boundary strengthening due to cutting of fine γ' precipitates and the frictional force of matrix γ phase were analyzed.
The Iron and Steel Institute of Japanの論文