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Co기 초합금 ECY768에서 응고 조직 및 탄화물 형성 거동
이정석,김현철,이재현,서성문,조창용,Lee, J.S.,Kim, H.C.,Lee, J.H.,Seo, S.M.,Jo, C.Y. 한국재료학회 2003 한국재료학회지 Vol.13 No.6
Directional solidification experiments were carried out at 0.5-150 $\mu\textrm{m}$/s in the Co-base superalloy ECY 768. As increasing solidification rate, the dendrite length increased and it reached the maximum at 150 $\mu\textrm{m}$/s, where the tip temperature is close to the liquidus. The liquidus and eutectic temperatures could be estimated by comparing the dendrite lengths and the temperature gradients at the solid/liquid interface and those were estimated as $1424.6^{\circ}C$ and $1343^{\circ}C$ respectively. Between the dendrites just below final freezing temperature, MC carbide and $M_{23}$$C_{6}$ carbide were found. It was confirmed that the script or blocky shape was Ta or W-rich MC carbide, and the lamellar shape was Cr-rich eutectic carbide. The solid/liquid interface morphology clearly showed that the Cr-rich eutectic carbide formed just after the script type MC carbide.
INCONEL 718 초내열 합금의 열처리에 따른 미세조직 변화
최중환,이기룡,조창용,김인배 ( J . H . Choi,K . R . Lee,C . Y . Jo,I . B . Kim ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.2
Microstructural evolution of wrought Inconel 718 superalloy with different heat treatment conditions was studied. Heat treatment was performed via conventional(CHT), modified(MHT), Merrick(MeHT) and modified Merrick(MMeHT) methods. The size of γ` and γ precipitates which are principal strengthening phases in Inconel 718 superalloy increase in order of CHT, MHT, MeHT. For the case of MMeHT, a coexistence of fine γ` precipitate and very coarse particles due to exess growth of γ which is called bimodal distribution, was observed. CHT gave the finest grain size. (Ti, Nb)C carbide and needle-like δ phase were formed together at grain boundaries for CHT, and were formed both inside and at boundaries of grains for MHT, MeHT and MMeHT. Morphology of partially serrated grain boundaries was developed in all heat treatment conditions except CHT.
SCM440(H) 및 SNCM439 강의 열처리 특성에 미치는 질량효과
남기석 ( K. S. Nam ),현양기 ( Y. K. Hyun ),조창용 ( C. Y. Jo ),조유종 ( Y. H. Cho ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.1
Recently, renewable energy sources such as wind turbine, solar cell are interested in preventing global warming which is caused by the consumption of fossil fuel. SCM440H and SNCM439 have been used in the major components of the wind turbine gear because of excellent mechanical properties. In the present study, the heat treated mechanical properties of SCM440H and SNCM439 with 150mm diameter were compared with those with 25 mm diameter which is generally accepted material for structural application. Heat treated SCM440H showed better mechanical properties such as tensile strength, hardness and impact absorbed energy compared with those in SNCM439. Hardenss value between as-quenched and as-quenched followed by tempering showed big difference in SNCM439, however the difference in SCM440H was relatively small. Heat treated mechanical properties of the alloys with 25mm diameter were more uniform value than those with 150mm diameter. (Received November 3, 2010; Accepted November 29, 2010)