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수퍼 2상 스테인리스강의 열처리 조건변화에 따른 첨가원소 질소의 거동
김형석,전채홍,송권,권숙인 ( Hyung Seok Kim,C . H . Jeon,Gun Song,S . I . Kwun ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.1
After changing the heat treating atmosphere of nitrogen gas, argon gas and vacuum, the nitrogen contents, microstructural changes, hardness and corrosion resistance of 0.25wt.%N alloyed super duplex stainless steel have been investigated in the temperature range from 1050℃ to 1350℃. The nitrogen content showed to be increased up to 0.36wt.% after heat treating the specimen in nitrogen gas at 1200℃, while the decrement of nitrogen content in vacuum atmosphere was shown down to 0.03wt.% at 1350℃. After heat treating in the mixed gas atmosphere of argon and nitrogen at 1250℃, the surface γ phase existed as α+γ phase increased with increasing nitrogen gas content. The γ single phase appeared at the surface above 80%N₂gas, while the surface α single phase was shown below 20%N₂gas. When heat treating the specimen in nitrogen gas at 1050℃, the hardness of austenite phases increased above Hv 40 at the surface layer compared to the hardness of the core parts, while decrement of denitriding effect caused to the hardness nearly unchanged between surface and the core parts after heat treating in vacuum atmosphere. The surface γ single phase specimen showed superior corrosion resistance than the surface α single phase specimen. The surface α phase existed in the α+γ microstructure showed higher corrosion resistance after heat treating in the nitrogen gas atmosphere than the a phase heat treated in the argon gas and vacuum atmosphere.
안재우,전채홍,안종관 대진대학교 1997 大眞論叢 Vol.5 No.-
In the fracture of materials, the art of fractography is well established. However there are few quantitative rules that related the morphology of the fracture surface to the properties of the material, particularly its resistance to fracture, or to the circumstances of the fracture, sudden and catastrophic, or gradual by fatigue, etc. Fractal geometry is used in order to these quantitative relation. Fracture surface is expressed by the fractal. The fractal dimension is related to the special feature of microstructure. And fracture profiles that are generated by midpoint displacement method are in aggrement with the measured profiles.
김승태,전채홍,박기성 한국부식학회 1998 Corrosion Science and Technology Vol.27 No.3
Turbine blade has been in service under severe condition such as high temperature, high pressure, corrosive and vibratory environment. Recently its frequent failure occurred and sometimes leaded to unexpected outage which is estimated to cost to several million dollars. In order to prevent blade failure, life assessment technology should be developed and a criteria for replacement of used blade be established. A lot of effort has been made to quantify the damage by using NDE technique and analytical evaluation. In turbine blade, life assessment technology is now well-established in the laboratory but it application to the field is not successful yet due to a lack of accuracy and a difficulty in the field application. Damage type and mechanism of gas turbine blade can be much different depending on operating condition and therefore considering each plant characteristic sufficiently, life assessment method and preventive measure can be properly applied.