Ni-Cr-W 系固溶強化型超耐熱合金の合金設計

概要

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For the purpose of developing cobalt-free tube materials for the heat-exchanger of nuclear steel-making process, an alloy design has been conducted with respect to the Ni-Cr-W system. Theoretically promising composition ranges in the Ni-Cr-W system are determined by the conditions that average electron vacancy number N_V is smaller than Barrows' critical electron vacancy number N^C and that lattice parameter a is greater than 3.580 A. Some compositions in the above mentioned range have been examined experimentally and 23% Cr-18%W has been determined as the best composition from the creep rupture strength point of view. Effects of carbon and magnesium on the creep rupture strength of 23%Cr-18%W-Ti-Zr-Bal. Ni alloy have been studied. The long-term creep rupture strength decreases with the increase of carbon content in the range from 0.03% to 0.14%. Up to 90 ppm magnesium does not significantly affect the creep rupture strength of the alloy at 1000℃, but about 160 ppm magnesium significantly reduces the creep rupture strength at that temperature. In conclusion, 23%Cr-18%W-(0.3%Ti)-(0.05%Zr)-0.03%C-Bal. Ni alloy has a high possibility of satisfying the creep rupture strength target, that is more than 1kg/mm^2 at 1000℃ and 10^5 hours.
社団法人日本鉄鋼協会の論文
1977-01-01