Gil-Su Kim

Effect of High Temperature Degradation on Microstructure and High Temperature Mechanical Properties of Inconel 617

Inconel 617 is a candidate tube material for high temperature gas-cooled reactors(HTGR). The microstructure and mechanical properties of Inconel 617 were studied after exposure at high temperature(). The dominant oxide layer was Cr-oxide. The internal oxide and Cr-depleted region were observed below the Cr-oxide layer. The depth of Cr-depleted zone and internal oxide increased with exposure time. The major phases of carbides are . The composition of were determined to be Cr-rich and Mo-rich, respectively. carbide is more stable than at high temperature. From the results of high temperature compression test, there were no significant changes in hardness and yield strength upon increasing exposure time.

Effect of the W—W contiguity on conductivity of W—Cu composite using the Voronoi diagram

Abstract W-15wt.% Cu nanocomposite powder samples were fabricated by ball-milling and subsequent hydrogen-reduction. The powder samples were heated to 1200 °C at 5 and 20 °C min−1 and sintered for 1 h to obtain different sintered microstructures. The homogeneity of the sintered microstructures was evaluated by the standard deviation of the Vickers hardness. The W—W contiguity was calculated by using Voronoi diagrams. The sintered microstructure in case of the 20 °C min−1 sample was more homogeneous and had lower W—W contiguity than the 5 °C min−1 sample. The microstructural homogeneity was directly related to the W—W contiguity. Thermal conductivity of the 20 °C min−1 sample was about 5 % higher than the thermal conductivity of the 5 °C min−1 sample. This indicates that the thermal conductivity is affected by the W—W contiguity resulting from the homogeneity of the sintered microstructure.