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HIP처리가 플라즈마 용사된 열차폐 코팅층의 접착강도와 고온특성에 미치는 영향
박영규,김성휘,김두수,이영찬,최철,정진성,김길무,김재철,Park, Young-Kyu,Kim, Sung-Hwi,Kim, Doo-Soo,Lee, Young-Chan,Choi, Cheol,Jung, Jin-Sung,Kim, Gil-Moo,Kim, Jae-Chul 한국재료학회 2000 한국재료학회지 Vol.10 No.4
HIP처리가 가스터빈 고정익 등 고온부품에 적용되는 열차폐 코팅층의 접착강도 및 고온특성에 미치는 영향을 조사하였다. 시편은 IN738LC 초합금 표면에 8wt%Y$_2$O$_3$-$ZrO_2$분말을 플라즈마 용사법으로 코팅한 후 $1200^{\circ}C$, 100MPa의 고온, 고압에서 4시간 동안 HIP 처리하여 준비하였다. 실험결과 HIP 처리된 코팅의 경우 미세균열과 기공이 상당량 감소하였으며 EDX분석을 통해 계면에서 원자간 상호확산이 발생한 것을 확인하였다. 이러한 코팅층의 치밀화 및 상호확산으로 인해 HIP처리된 코팅층의 접착강도는 48% 이상 크게 증가하였으며 조직 또한 균질화 되었다. 반면 가열과 냉각이 반복되는 환경에서 코팅층의 내구력은 HIP 처리된 경우가 다소 저하되었다. 이는 코팅과 모재와의 열팽창 차이로 인한 변형을 완화시켜주는 기공과 미세균열이 감소되었기 때문으로 판단된다. A study has been made to investigate the effects of hot isostatic pressing(HIP ping) on bond strength and elevated temperature characteristics of thermal barrier coating(TBC). The specimens were prepared by HIPping of TBC which is composed of the ceramic top coat(8wt%$Y_2$$O_3$-$ZrO_2$) and the metallic bond coat on the matrix of IN738LC superalloy. The results showed that the porosity and microcracks in the ceramic top coat of TBC were significantly decreased by HIP. As a result, the bond strength of the HIPped coating was increased above 48% compared to that of as-coated specimen and microstructure was homogenized. It was found that the thermal cycle resistance of HIPped coating was inferior to that of as-coated specimen. It was considered that this result was mainly caused by the reduction of internal defects in the top coat layer which could play a role in relaxing the thermal stress due to a large difference in thermal expansion between TBC and matrix.
슈퍼 2상 스테인리스강에서 χ와 σ상의 석출거동에 미치는 W치환의 영향
한현성,김성휘,강창룡,Han, Huyn-Sung,Kim, Seong-Hwi,Kang, Chang-Yong 한국재료학회 2016 한국재료학회지 Vol.26 No.4
This study was carried out to investigate the effect of W substitution on the precipitation behavior of ${\chi}$ and ${\sigma}$ phases in super duplex stainless steel. The ${\chi}$ phase was precipitated at the interface of ferrite / austenite phases and inside the ferrite phase at the initial stage of aging. With an increase in the aging time, the volume fraction of the ${\chi}$ phase increased, and then decreased with the transformation from the ${\chi}$ phase to the ${\sigma}$ phase. The ${\sigma}$ phase was precipitated later than the ${\chi}$ phase, and the volume fraction of x phase increased with the increase in the aging time. The ferrite phase was decomposed into the new austenite (${\gamma}2$) and ${\sigma}$ phases by aging treatment. The decomposition of the ferrite phase into the ${\gamma}2$ and ${\sigma}$ phases was retarded by W substitution for Mo. The volume fraction of the ${\chi}$ phase increased and that of the ${\sigma}$ phase decreased due to W substitution. The ${\chi}$ and ${\sigma}$ phases were intermetallic compounds, which had lower nickel concentration, and higher chromium, molybdenum, and tungsten concentrations. The ${\chi}$ phase has higher molybdenum and tungsten concentrations than those of the ${\sigma}$ phase. The amounts of chromium and nickel in the ${\chi}$ and ${\sigma}$ phases did not change, but these phases have higher concentrations of molybdenum and tungsten due to W substitution for Mo.
김영수(Youngsoo Kim),이덕규(Duck-Gyu Lee),정영도(Youngdo Jung),정연도(Yeon Do Jeong),이준희(Junhee Lee),이성휘(Sung Hwi Lee),김완두(Wan-Doo Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
We proposed a new expandable drilling tool that allows us to make a bottle-shape pressure well. The expansion of internal cavities has increased the area of air exposure in landfills, resulting in increased volume flow rates of airflow. Also, installation time could be significantly saved due to one step installation of air pipe.