長時間時効に伴う改良型HP系耐熱鋳鋼の組織変化 : 改良型HP系耐熱鋳鋼の経年使用材の補修溶接割れ(第2報)

概要

論文の詳細を見る
Changes in microstructures of modified HP-type heat-resistant cast alloys with long term aging were investigated using the as cast, artificially aged and practically used alloys at the elevated temperature. The microscopic observation and the X-ray diffraction analysis for microconstituents in heat-treated alloys were conducted in order to clarify the changes in morphologies and phases of microconstituents with heat treatment. In the niobium containing alloys, chromium-rich carbide of M_7C_3 and niobium carbide (NbC) changed to M_<23>C_6 and nickel-niobium silicide (7 phase) with long term aging, respectively. On the other hand, only chromium-rich carbide (M_7C_3 or M_<23>C_6) precipitated in as cast condition in the niobium-free alloys and the transformation of M_7C_3→M_<23>C_6 or M_<23>C_6+nickel-rich silicide (G phase) occurred in the long term aging situation. The lamellar structure of eutectic microconstituents in the as cast alloy tended to agglomerate and coarsen with aging, and finally linked forming a continuous network surrounding the cellular dendrite boundaries. Zr addition to the HP cast alloy made it possible to reduce the microconstituents on the dendrite boundary due to the refinement of dendritic cell.
社団法人溶接学会の論文
2000-08-05