• 자원리싸이클링
• /
• 제4권1호
• /
• pp.52-59
• /
• 1995

Co의 리싸이클링을 원활히 하기 위하여 괴상 superalloy 스크랩을 용융Zn으로 분해할 때의 최적처리조건을 조사하였다. 조사한 superalloy는 Co-기 Mar-M-509와 X-45 그리고 Ni-기 Rene 80이었다. Zn/스크랩 비율이 1.5~6.5인 장입물을 질소 분위기에서 $750~900^{\circ}C$에서 1~7.5시간 동안 가열하였다. 용융된 Zn은 스크랩을 용해하였고, Zn은 $850~900^{\circ}C$에서 4~6시간 동안 진공증류하여 제거되었다. Mar-M-509와 Rene 80의 최적 처리조건은 용해온도 약 $^850{\circ}C$, Zn/스크랩 비율 약 5, 그리고 용해시간 약 5.5시간이었다. Zn처리 superalloy 생성물은 쉽게 부스러졌으며, 산 용액에 의해 빠르게 침출되었다. Mar-M-509 또는 Rene 80의 경우, 미처리 스크랩(9mm 조각)을 화학양론양 5배의 6N HCl으로 $90^{\circ}C$에서 3시간 동안 처리하면 침출도는 약 1.5~7.2%에 지나지 않았으나, Zn처리 생성물(-20 메쉬의 것)의 침출도는 약 89.0~93.0%나 되었다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2009년도 추계학술대회 논문집
• /
• pp.89-92
• /
• 2009

As a class of materials, Ni-base superalloys are among the most difficult metal alloys to forge together with refractory metals and cobalt-base superalloys. The mechanical properties of Ni-base superalloys depend very much on grain size and the strengthening phases, $\gamma$' ($Ni_3$(Al,Ti)-type) and $\gamma$".($Ni_3$Nb-type). Especially, the control of grain size remains as a sole means for the control of mechanical properties. The grain size and distribution changes of the wrought superalloys during hot working and heat treatment are mainly controlled by the recrystallization and grain growth behaviors. In this presentation, prediction technology of grain size through the computer-aided process design, and numerical modeling for predicting the microstructure evolution of Ni-base superalloy during hot working were introduced. Also, some case studies were dealt with actual forming processes of Ni-base superalloys.

• 한국재료학회지
• /
• 제13권6호
• /
• pp.381-388
• /
• 2003

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.

• 한국안전학회지
• /
• 제28권3호
• /
• pp.18-22
• /
• 2013

The Co-base super heat resisting alloy ECY768 is employed in gas turbine because of its high temperature strength and oxidation resistance. The prediction of fatigue life for superalloy is important for improving the efficiency. In this paper, low cycle fatigue tests are performed as variables of total strain range and temperature. The relations between strain energy density and number of cycle to failure are examined in order to predict the low cycle fatigue life of ECY768 super alloy. The lives predicted by strain energy methods are found to coincide with experimental data and results obtained from the Coffin-Manson method. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

• 한국결정성장학회지
• /
• 제27권6호
• /
• pp.313-318
• /
• 2017

본 연구에서는 가스터빈용 Co계 합금인 ECY768 as-cast 합금 시편의 melt/mold 온도에 따른 결정구조 및 미세조직 및 변화를 고찰하였다. As-cast ECY768 샘플들은 전반적으로 amorphous 특성을 보여주고 있으며 기지인 Co상과 금속탄화물상으로 구성되어 있음을 확인하였으며, mold의 온도에 따른 XRD 패턴에서의 결정성 변화를 고찰하였다. 광학현미경(OM)을 이용하여 as-cast 샘플들의 결정립계에 석출물을 관찰하였다. 또한 FE-SEM에 의한 미세구조 분석시 Co기지상과 금속 탄화물의 석출물이 발견되는 영역이 관찰하였으며 EDS 분석에 의해 금속과 탄소의 화학양론이 확연히 다른 $M_{23}C_6$ 및 MC-type 조직으로 확인할 수 있었다. 여기서 $M_{23}C_6-type$의 탄화물은 Cr 원소를 주성분으로 하는 것을 확인할 수 있었으며, MC-type 탄화물은 Ta 원소가 주성분임을 확인할 수 있었다.