Alloy design is performed developing an intermediate heat exchanger alloy for atomic energy steelmaking, having good workability so as to be formed to tube and higher stress rupture strength than 1kg/mm² at 1000°C-10⁵ hours.
171 compositions are extracted theoretically from about 17000 compositions in Ni-Co-Cr-Mo-W austenitic system and seven of them are examined experimentally. As a result, 16Cr-20W-30Co-Bal. Ni is established as one of the best austenitic compositions. Examining the effect of the addition of B, Zr, Y, and Al on the properties of 16Cr-20W-30Co-Bal. Ni and 20Cr-16W-30Co-Bal. Ni, Zr is proved to improve stress rupture strength and Al to promote internal oxidation in He.
The finally developed alloy composed of (0.05C)-16Cr-20W-30Co-(0.5Ti)-0.05Zr-Bal. Ni seems to meet the target.