Effect of Minor Alloying Elements on Hot-Workability of Ni-Cr-W Superalloys

概要

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Research and development have been carried out on new heavy duty Ni-Cr-W superalloys for application to the structural components of high-temperature gas-cooled reactors with coolant outlet temperatures of around 1, 000°C. In the first step of the program, the basic chemical composition, i.e. Cr/W contents in the alloy was determined to be Ni-18 to 19 mass% Cr-20 to 22 mass% W. In order to examents the effect of additional alloying elements, i.e. Si, Mn, Y, B, T etc.c. on the hot-workability, a series of high-strain-rate high-temperature tension tests, so-called Gleeble tests, was carried out on 21 heats of the alloys with the basic chemical com-position of Ni-18 to 19 mass% Cr-20 to 22 mass% W. The addition of Si and Mn is extremely harmful to the hot-workability. On the contrary, the addition of Y is very effective in improving the hot-workability. The addition of B and Ti is also beneficial. Neither enrichment of C nor addition of Nb or Fe is significantly beneficial to the hot-workability. The multiple regression analysis technique is applicable to the predic-tion of the hot-workability of Ni-Cr-W superalloys.