耐熱合金 NA22H の 1200℃クリープ破断強さにおよぼす合金元素の影響

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To investigate the effect of alloying elements on the creep rupture strength of NA22H, stress-rupture tests were carried out at stresses of 1 and 0.6 kg/mm^2 and a temperature of 1200℃ on the specimens of varying C, W, Si, Cr and Ni contents respectively. And also the microstructural changes associated with varying the contents of alloying elements were investigated by optical microscopy and X-ray phase identification. The following results were obtained : (1) i) Addition of 0.4 to 0.65% C improved effectively creep rupture strength. ii) The strength increased with an increased W content up to c.a. 3%, above which the strength remained nearly constant. iii) The maximum creep rupture strength was obtained by the addition of c.a. 1% Si. It is deduced that excellent creep properties are obtained in the practical working range of 0.8 to 1.5% Si. iv) The specimen containing 27% Cr and 48% Ni showed a higher creep rupture strength than the others of varying Cr and Ni contents. (2) Considerable amounts of massive- and dot-carbides which were identified as M_<23>C_6 were observed in the microstructures of all specimens. The amounts of these carbides increased with increasing C, W and Ni contents. Massive carbides showed marked agglomeration during the testing at 1200℃, on the other hand dot carbides disappeared. It seems that an excess amount of massive carbides lowers creep rupture strength. (3) The elongation after rupture, especially at less stress, decreased with a rise in the amount of massive carbides. It is considered that the elongation depends to a considerable degree on the amount of massive carbides.
社団法人日本鉄鋼協会の論文
1964-07-01

耐熱合金 NA22H の 1200℃クリープ破断強さにおよぼす合金元素の影響

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