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- 저자 : 함기수(Gi Su Ham) (검색결과 6 건)
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레이저 클래딩 공정을 이용한 Ni-Cr-B-Si + WC/12Co 복합 코팅층의 제조 및 기계적 특성
함기수,김철오,박순홍,이기안,Ham, Gi-Su,Kim, Chul-O,Park, Soon-Hong,Lee, Kee-Ahn 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.5
In this study we manufacture a Ni-Cr-B-Si +WC/12Co composite coating layer on a Cu base material using a laser cladding (LC) process, and investigate the microstructural and mechanical properties of the LC coating and Ni electroplating layers (reference material). The initial powder used for the LC coating layer is a powder feedstock with an average particle size of $125{\mu}m$. To identify the microstructural and mechanical properties, OM, SEM, XRD, room and high temperature hardness, and wear tests are implemented. Microstructural observation of the initial powder and LC coating layer confirm the layer is composed mainly of ${\gamma}-Ni$ phases and WC and $Cr_{23}C_6$ carbides. The measured hardness of the LC coating and Ni electroplating layers are 653 and 154 Hv, respectively. The hardness measurement from room up to high temperatures of $700^{\circ}C$ result in a hardness decrease as the temperature increases, but the hardness of the LC coating layer is higher for all temperature conditions. Room temperature wear results show that the wear loss of the LC coating layer is 1/12 of the wear level of the Ni electroplating layer. The measured bond strength is also greater in the LC coating than the Ni electroplating.
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고속 화염 용사 공정으로 제조된 WC계 및 Cr<sub>3</sub>C<sub>2</sub>계 Cermet 코팅 소재의 미세조직 및 마모 특성
강연지,함기수,김형준,윤상훈,이기안,Kang, Yeon-Ji,Ham, Gi-Su,Kim, Hyung-Jun,Yoon, Sang-Hoon,Lee, Kee-Ahn 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.5
This study investigates the microstructure and wear properties of cermet (ceramic + metal) coating materials manufactured using high velocity oxygen fuel (HVOF) process. Three types of HVOF coating layers are formed by depositing WC-12Co, WC-20Cr-7Ni, and Cr3C2-20NiCr (wt.%) powders on S45C steel substrate. The porosities of the coating layers are $1{\pm}0.5%$ for all three specimens. Microstructural analysis confirms the formation of second carbide phases of $W_2C$, $Co_6W_6C$, and $Cr_7C_3$ owing to decarburizing of WC phases on WC-based coating layers. In the case of WC-12Co coating, which has a high ratio of $W_2C$ phase with high brittleness, the interface property between the carbide and the metal binder slightly decreases. In the $Cr_3C_2-20CrNi$ coating layer, decarburizing almost does not occur, but fine cavities exist between the splats. The wear loss occurs in the descending order of $Cr_3C_2-20NiCr$, WC-12Co, and WC-20Cr-7Ni, where WC-20Cr-7Ni achieves the highest wear resistance property. It can be inferred that the ratio of the carbide and the binding properties between carbide-binder and binder-binder in a cermet coating material manufactured with HVOF as the primary factors determine the wear properties of the cermet coating material.
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High Velocity Oxygen Fuel 공정으로 제조된 Ni 계 자용성 복합 코팅 소재의 미세조직과 마모 특성에 미치는 고주파 열처리의 영향
위동열,함기수,박순홍,이기안,Wi, Dong-Yeol,Ham, Gi-Su,Park, Sun-Hong,Lee, Kee-Ahn 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5
In this study, the formation, microstructure, and wear properties of Colmonoy 88 (Ni-17W-15Cr-3B-4Si wt.%) + Stellite 1 (Co-32Cr-17W wt.%) coating layers fabricated by high-velocity oxygen fuel (HVOF) spraying are investigated. Colmonoy 88 and Stellite 1 powders were mixed at a ratio of 1:0 and 5:5 vol.%. HVOF sprayed self-fluxing composite coating layers were fabricated using the mixed powder feedstocks. The microstructures and wear properties of the composite coating layers are controlled via a high-frequency heat treatment. The two coating layers are composed of ${\gamma}-Ni$, $Ni_3B$, $W_2B$, and $Cr_{23}C_6$ phases. Co peaks are detected after the addition of Stellite 1 powder. Moreover, the WCrB2 hard phase is detected in all coating layers after the high-frequency heat treatment. Porosities were changed from 0.44% (Colmonoy 88) to 3.89% (Colmonoy 88 + ST#1) as the content of Stellite 1 powder increased. And porosity is denoted as 0.3% or less by inducing high-frequency heat treatment. The wear results confirm that the wear property significantly improves after the high-frequency heat treatment, because of the presence of well-controlled defects in the coating layers. The wear surfaces of the coated layers are observed and a wear mechanism for the Ni-based self-fluxing composite coating layers is proposed.
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선택적 레이저 용융 공정으로 제조된 AISI 316L 합금의 인장 및 충격 인성 특성에 미치는 응력 완화 열처리의 영향
양동훈,함기수,박순홍,이기안,Yang, Dong-Hoon,Ham, Gi-Su,Park, Sun-Hong,Lee, Kee-Ahn 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.4
In this study, an AISI 316 L alloy was manufactured using a selective laser melting (SLM) process. The tensile and impact toughness properties of the SLM AISI 316 L alloy were examined. In addition, stress relieving heat treatment (650℃ / 2 h) was performed on the as-built SLM alloy to investigate the effects of heat treatment on the mechanical properties. In the as-built SLM AISI 316 L alloy, cellular dendrite and molten pool structures were observed. Although the molten pool did not disappear following heat treatment, EBSD KAM analytical results confirmed that the fractions of the low- and high-angle boundaries decreased and increased, respectively. As the heat treatment was performed, the yield strength decreased, but the tensile strength and elongation increased only slightly. Impact toughness results revealed that the impact energy increased by 33.5% when heat treatment was applied. The deformation behavior of the SLM AISI 316 L alloy was also examined in relation to the microstructure through analyses of the tensile and impact fracture surfaces.
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Laser Cladding 공정으로 제조된 Tribaloy T-800 코팅 소재의 미세조직 및 용융 Al 침식 특성
김경욱,함기수,박순홍,이기안,Kim, Kyoung-Wook,Ham, Gi-Su,Park, Sun-Hong,Lee, Kee-Ahn 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.3
A T-800 (Co-Mo-Cr) coating material is fabricated using Co-Mo-Cr powder feedstock and laser cladding. The microstructure and melted Al erosion properties of the laser-cladded T-800 coating material are investigated. The Al erosion properties of the HVOF-sprayed MoB-CoCr and bulk T-800 material are also examined and compared with the laser-cladded T-800 coating material. Co and lave phases (Co<sub>2</sub>MoCr and Co<sub>3</sub>Mo<sub>2</sub>Si) are detected in both the laser-cladded T-800 coating and the bulk T-800 materials. However, the sizes of the lave phases are measured as 7.9 ㎛ and 60.6 ㎛ for the laser-cladded and bulk T-800 materials, respectively. After the Al erosion tests, the erosion layer thicknesses of the three materials are measured as 91.50 ㎛ (HVOF MoB-CoCr coating), 204.83 ㎛ (laser cladded T-800), and 226.33 ㎛ (bulk T-800). In the HVOF MoB-CoCr coating material, coarse cracks and delamination of the coating layer are observed. On the other hand, no cracks or local delamination of the coating layer are detected in the laser T-800 material even after the Al erosion test. Based on the above results, the authors discuss the appropriate material and process that could replace conventional bulk T-800 materials used as molten Al pots.
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