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Microstructural features, mechanical properties, and corrosion properties of a SAF2205 duplex stainless steel (DSS) were systematically investigated as functions of cooling rate during casting and heat treatment conditions. The choice of a duplex stainless steel was a SAF2205 alloy, of which composition is 0.03C, 21~23Cr, 4.5~6.5Ni, 2.5~3.5Mo, 0.08~0.2N, 1.0Si, and 2.0Mn with remaining Fe. A 5-stepped sand mold and the permanent Y-block mold were used to check the effect of cooling rate during solidification. The microstructural characteristics, such as grain size, the d/γ ratio, the existence of the carbides and σ phase has been noticed to greatly change with the variation of cooling rate during the casting procedure. Various heat treatment conditions were also examined to achieve the optimized mechanical properties of DSS. Based on the preliminary examination, the feasibility study of utilization of centrifugal casting has been carried out for the production of better quality DSS pipe components. Melting and casting practices of DSS during centrifugal casting in an air atmosphere were systematically investigated in order to obtain the optimized process parameters.

Numerous techniques have been applied to fabricate three-dimensional scaffolds of high porosity and surface area. In this study, we fabricated three-dimensional macroporous scaffold by polymeric sponge method using calcium phosphate glass in CaO-CaF 2 -P 2 O 5 -MgO-ZnO. Calcium phosphate glass slurry was prepared by suspending the glass powder in water, polyvinyl alcohol, polyethylene glycol and dimethyl formamide. Reticulated polyurethane sponges were used as a template and were coated with the prepared slurry by infiltration technique several times. Calcium phosphate glass slurry was homogenously thick coated when the amounts of calcium phosphate glass powder and polyvinyl alcohol were 67 and 8 wt%, respectively. Addition of 10 wt% dimethyl formamide as a drying control chemical additive into a slurry successively prevented microcrack formation. Sintering at 850 o C exhibited dense microstructures as well as entire elimination of organic additives. When the macroporous scaffolds were transplanted subcutaneously in the dorsal surface of mice, the vascularized mesenchymal stem cells were formed in the transplanted scaffolds and the regenerated connective tissue was also formed after 4 weeks. These results of the present study suggested that the fabricated macroporous scaffold is expected to be useful scaffold material for osteogenic tissue development.

In general, thermal treatment at 500oC ~ 900oC ranges depending upon alloy composition of stainless steels can sensitize the steels and promote the intergranular cracking, and their intergranular corrosion resistance is decreased. These behaviors seem to be related to the change of microstructures. So, heat treatment at that temperature range should be avoided in fabrication, especially welding of stainless steels. In this work, it is focused on the effect of thermal treatment on caustic stress corrosion cracking of super austenitic stainless steel - S32050 The low temperature thermal treatment increased greatly the resistance to caustic SCC than those of annealed specimen. This enhancement might be closely related to the reduction of residual stress and slightly large grain, but its resistance was not affected by the anodic polarization behavior.