Recently the growth of the renewable energy production has caused the flexible operation in LNG combined cycle power plant. Due to the rapid start and stop operations, large CrMoV castings used for turbine casings and valve bodies could be distorted and lead to replacement or welding repair. This study was performed to find out the characteristics of the repair welding for a damaged CrMoV casting steel. A typical field repair method (arc & TIG welding) was applied to making specimens. The degraded N2 packing head sample from the steam turbine was used. The evaluations of weldments were carried out in terms of microstructural characterization, microhardness measurements, tensile, creep-rupture and fatigue tests. Color etching was also applied for better understanding of welding microstructures. As the boundary between HAZ and base material was deteriorated by welding, it caused microstructural changes formed during PWHT and the shortening of the remaining residual life. By comparing the properties according to repair welding method, it was possible to derive what important welding factors were. As a result, arc welding method is more suitable for repair welding on CrMoV castings.

In this study, the characteristic of an amorphous fishing weight material according to controlling the alloy type and alloy composition of the glass forming agent added in PbO₂ oxide was investigated. According to the experimental, when the glass forming agent of 15wt%SiO₂-1wt%MgO content was added in β-PbO₂, an amorphous fishing weight substitute having the lowest friction coefficient, excellent corrosion resistance and durability was obtained. The cell number of PbO₂-15wt%SiO₂-1wt%MgO sample incubated in cell culture fluid tended to hardly decrease even after a lapse of 24 hours, It means that the fabricated PbO₂-15wt%SiO₂-1wt%MgO sample is significantly less-toxic and harmless to the human body, unlikely to metallic lead. It is considered that an fabricated amorphous fishing weight substitute proved to have a potential as an eco-friendly material with little marine pollution.

In the automobile and shipbuilding industries, various materials and components require superior surface strength, excellent wear resistance and good resistance to repeated loads. To improve the surface properties of the materials, various surface heat treatment methods are used, which include carburizing, nitriding, and so on. Among them, carburizing treatment is widely used for structural steels containing carbon. The effective carburizing thickness required for materials depends on the service environment and the size of the components. In general, however, there is a limit in evaluation of the surface properties with a standardized mechanical test method because the thickness or cross-sectional area of the carburized layer is limited. In this regard, the nanoindentation technique has lots of advantages, which can measure the mechanical properties of the material surface at the nano and micro scale. It is possible to understand the relationship between the microstructural change in the hardened layer by carburizing treatment and the mechanical properties. To be spread to practical applications at the industrial level, in this paper, the principle of the nanoindentation method is described with a representative application for analyzing the mechanical properties of the carburized material.

The effects of scandium addition on the Al-6Si-2Cu Alloy were investigated. The Al-6Si-2Cu-Sc alloy was prepared by gravity die casting process. In this study, scandium was added at 0.2 wt%, 0.4 wt%, 0.8 wt%, and 1.0 wt%. The microstructure of Al-6Si-2Cu-Sc alloy was investigated using Optical Microscope, Field Emission Scanning Electron Microscope, Electron Back Scatter Diffraction, and Transmission Electron microscope. The microstructure of Al-6Si-2Cu alloy with scandium added changed from dendrite structure to equiaxed crystal structure in specimens of 0.4 wt% Sc or more, and coarse needle-shape eutectic Si and β-Al₅FeSi phases were segmented and refined. The nanosized Al₃Sc intermetallic compound was observed to be uniformly distributed in the modified Al matrix.