In the previous report, ("Hitachi Hyoron" No. 11, 1955) the authors described the effects of Nb, V, Ti and N on the properties of Ni-Cr (20-15%) series heat-resisting steel for gas turbines. In this report, the authors examined the effects of Nb, V, Ti and N on the forgeability, solution-treatment, hardness, aging hardness, microstructure, mechapical properties at high temperaturb, oxidatkon, resistnce and creep limits of Ni-Cr-Co (20-15-15%) series heatresisting steel for gas turbineis.
The results obtained were summarized as follows:
1) In respect to forgeability, Nb was superior, while the specimen A (which contained no special element) Ti and V were comparatively good next to Nb, and then N had worse effect on it.
2) When the solution temperature was 1200°C, the specimen. "A" showed highest aging hardness. Next to the specimen "A", those with N, V, Ti and Nb were good in the term.
3) N conferred the best Property in the tensile strength at high temperature, however when the temperature rose above 700°C, the differences. between the properties pf steels with different elements became very small.
4) In respect to oxidation resistance, Nb was most effective and v had worse effect on it.
5) As for the creep limit, the specimen "A" Was superior, and then, next to "A". speci mens containing Ti, N, V and Nb were good in the term.