In the present study, the chemical compositions of secondary phases and the behavior of each element by aging after solution-treatment with the LCN-155 type heat-resisting alloys were examined by chemical analyses of residues extracted electrolytically.
The results obtained were as follows:
(1) The metallic constituents in the secondary phases after aging consisted mainly of Cr, at a lower temperature and consisted of Cr and Mo, W, and Cb with a larger atom radius at a higher temperature. With the duration of aging, the ratio of concentrations of metallic elements to C and N in the precipitates increased.
(2) The C, N, Cr, Mo, W, and Cb in the alloys were concentrated into the precipitates with the duration of aging, e. g., in the state as aged at 900°C for 168 hours the most parts of Cb, about 50% of each C and N, about 10% of each Mo and W, and about 4% of Cr in the alloy.
(3) Additions of Cb or/and N induced the changes in the partial distributions of elements, especially C, Mo, and W, into the matrix and the precipitates.
(4) In the alloys containing Cb, the undissolved Cb compound after solution treatment consisted of (Cb, Cr, Mo, W) 4 (C, N) 3. The precipitates in the fully age-hardened alloys were presumed to be as follows:
C-Fe-Co-Cr-Ni-Mo-W alloy (Cr21Mo1.5W0.5) C6:[M23C6 carbide]
C-Fe-Co-Cr-Ni-Mo-W-Cb alloy (Cr18MO2W1Cb2) C6:[M23C6 carbide]
C-Fe-Co-Cr-Ni-Mo-W-N and C-Fe-Co-Cr-Ni-Mo-W-N-Cb alloys (Cr, Co, Fe, Ni) x (Mo, W, Cb) y (C, N), z:[X phase]