• Journal of Welding and Joining
• /
• v.5 no.2
• /
• pp.27-34
• /
• 1987

The characteristics of arc sprayed layer were studied with hardness test and microstructural observation. The erosion resistance of arc sprayed layer was also evaluated using a method of steel ball blasting test which was proposed in this study as a test method for measuring the erosion properties in the impact wear condition. By an impact of the molten droplets on the redeposited substrate, lamella structure was formed which contains laminated oxide layers, fissures, and porosities. As a result of mechanical tests, it was shown that the sprayed specimen showed higher hardness than the substrate, but it resulted in higher erosion rate than the substrate. The poor erosion property obtained with a sprayed coating was considered to be attributable to easy flaking off the the layers laminated with brittle oxide layers.

• Proceedings of the KWS Conference
• /
• 2006.10a
• /
• pp.128-129
• /
• 2006

To investigate impact property characteristics on the low temperature plate weld metal, the two different plates of the same steel grade were welded and evaluated by Mo bearing and no Mo containing welding consumables. The results are summarized as follows; 1) Multi pass welded Mo bearing weldment was not satisfied with the requirement of tensile strength, while no Mo containing one was satisfied with it 2) In the plate butt weldment, the impact property of weld metal was highly affected by both the welding consumable and plate.

• Journal of Environmental Impact Assessment
• /
• v.5 no.2
• /
• pp.49-57
• /
• 1996

On the basis of sustainable long-term water resources planning, the development of ground water resources should be interlocked with the surface water development In considering the intertemporal equity, overpumping of groundwater may diminish or eliminate the groundwater resources stock of post-generations. Regulatory landuse zoning for groundwater resources recharge area is indispensable measures to prevent groundwater pollution. Adequate treatment of polluted water from various sources such as municipal sewage, industrial wastewater, landfill site leachate, and abandoned boring wells, is also necessary for groundwater protection. To preserve groundwater resources as common property goods, groundwater use tax should be imposed upon the large scale groundwater use. Finally, the establishment of groundwater development license system is recommended to achieve the social optimal production and to avoid external diseconomy.

• Journal of the Korean Ceramic Society
• /
• v.43 no.10 s.293
• /
• pp.653-659
• /
• 2006

The glass-SiC composites have been manufactured via viscous flow of glass for investigating their sinterability and various properties. The relative density of 99.6% could be achieved when 5 wt% SiC was mixed with glass powder, glass-rearranged at 460$^{\circ}C$ for 3 h and then sintered at 665$^{\circ}C$ for 1 h. The sintered density was decreased as adding more than 5 wt% SiC to glass powder. The resistance properties against hyper velocity copper jet formed by explosion of K215 warhead were compared with other ceramics such as $Al_2O_3$ and pyrex, resulting in lower values than that of $Al_2O_3$.

• Journal of the Korean Society for Heat Treatment
• /
• v.29 no.6
• /
• pp.277-283
• /
• 2016

The influences of cooling pressure of quenching process on the mechanical properties such as hardness, impact endurance and anti-thermal fatigue behaviour of STD61 steel were investigated. The specimens were heat-treated using a vacuum furnace in which they were austenitized at $1,030^{\circ}C$ for 1hour under the pressure of $10^{-3}$ torr and cooled with quenching gas of various pressure, i.e. 1, 2 and 6 bar. According to the observation on the specimens prepared with quenching from austenizing temperature, the mechanical properties of the samples with higher quenching pressure were better than those of prepared at lower quenching pressure. The samples prepared with high quenching pressure showed the more homogeneous microstructure with finer carbides. The size of carbides such as VC and (Fe, Cr)C in quenched specimens decreased with increasing gas quenching pressure. It is considered that the rapid cooling with pressure may restrict the formation and growth of carbide.

• Journal of the Korean Society for Heat Treatment
• /
• v.10 no.3
• /
• pp.172-180
• /
• 1997

The microstructure, tensile and impact properties of forgings of 7175 aluminium alloy have been studied as a function of intermediate thermo-mechanical treatment(ITMT) process. The ITMT process is consisted of warm working and recrystallization. In the case that the billet was warm-worked above 60% below $250^{\circ}C$ and recrystallized at $475^{\circ}C$, the grain size revealed about $17{\mu}m$ which corresponds to one third of that of conventional process. The refinement of grain size leaded to the improved ductility and impact energy without sacrifice of tensile strength. It was found that the ITMT processed specimen behaved isotropically due to the near equiaxed grains. It was observed that the ITMT processed specimen showed the mixed fracture mode of transgranular and intergranular, instead of intergranular mode. This change of fracture mode contributed to the improved ductility and impact property.

• Corrosion Science and Technology
• /
• v.7 no.3
• /
• pp.145-151
• /
• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• Korean Journal of Materials Research
• /
• v.29 no.3
• /
• pp.189-195
• /
• 2019

The effect of C, Mn, and Al additions on the tensile and Charpy impact properties of austenitic high-manganese steels for cryogenic applications is investigated in terms of the deformation mechanism dependent on stacking fault energy and austenite stability. The addition of the alloying elements usually increases the stacking fault energy, which is calculated using a modified thermodynamic model. Although the yield strength of austenitic high-manganese steels is increased by the addition of the alloying elements, the tensile strength is significantly affected by the deformation mechanism associated with stacking fault energy because of grain size refinement caused by deformation twinning and mobile dislocations generated during deformation-induced martensite transformation. None of the austenitic high-manganese steels exhibit clear ductile-brittle transition behavior, but their absorbed energy gradually decreases with lowering test temperature, regardless of the alloying elements. However, the combined addition of Mn and Al to the austenitic high-manganese steels suppresses the decrease in absorbed energy with a decreasing temperature by enhancing austenite stability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.252-253
• /
• 2010

• Proceedings of the KWS Conference
• /
• 1995.10a
• /
• pp.154-156
• /
• 1995