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1
Content available High Temperature Oxidation Property of Ni Based Superalloy CM247LC Produced Via Selective Laser Melting Process
Lee Jung-Uk, Kim Young-Kyun, Seo Seong-Moon, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2023
|
Vol. 68, iss. 1
107--112
EN
CM247LC alloy was manufactured by using selective laser melting (SLM) process, one of the laser powder bed fusion (L-PBF) methods. The hot isostatic pressing (HIP) process was additionally conducted on the SLM-built CM247LC to control its microstructures and defects. The high temperature oxidation property was investigated, and it was compared with conventional DS247LC sample (reference) prepared via the directional solidification process. The L-PBF HIP sample showed blocky-type MC carbides generated along the grain boundary with average size of about 200 nm. A semi-spherical primary γ' phase of size 0.4-1.0 μm was also observed inside the grains. Moreover, the DS247LC sample displayed a coarse eutectic γ' phase and many script-type MC carbides. Furthermore, cuboidal-type γ' with an average size of about 0.5 μm was detected. High-temperature oxidation tests were conducted at 1000°C and 1100°C for 24 hours. The results at 1100°C oxidation temperature showed that the measured oxidation weight gains for HIP and DS247LC were 1.96 mg/cm2 and 2.26 mg/cm2, respectively, indicating the superior high-temperature oxidation resistance of the L-PBF HIP sample. Based on the above results, a high-temperature oxidation mechanism of the CM247LC alloys manufactured by the SLM process and the directional solidification process has been proposed.
2
Content available Effect of Post-Heat Treatment on the Impact Toughness and Crack Propagation Mechanism of AISI D2 Tool Steel Manufactured by Direct Energy Deposition
Park Jun-Hyung, Kim Kyu-Sik, Koo Yong-Mo, Kim Jin-Young, Kim Min-Chul, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2023
|
Vol. 68, iss. 1
119--122
EN
This study investigated the effect of heat treatment on the microstructure and impact toughness property of AISI D2 manufactured with direct energy deposition (DED) and compared the results with conventional wrought material. The fracture crack propagation behavior was examined in connection with microstructures through fracture surface analysis. AISI D2 manufactured with DED had a eutectic structure that turned into a net-type carbide after heat treatment, and Cr-rich needle-type secondary carbide was observed. Impact toughness of DED AISI D2 measured 2.0 J/cm2 in the as-built sample and 1.1 J/cm2 in the heat-treated sample. Compared to a wrought heat-treated AISI D2, DED AISI D2 had relatively low impact toughness. DED AISI D2 and wrought material had different crack propagation mechanisms. In DED AISI D2, the eutectic structure and net-type carbide boundary were identified as the major microstructural factor decreasing impact toughness.
3
Content available Manufacture of MoO3 Coating Layer Using Thermal Spray Process and Analysis of Microstructure and Properties
Hwang Yu-Jin, Kim Kyu-Sik, Park Jae-Sung, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2022
|
Vol. 67, iss. 4
1535--1538
EN
MoO3 thick film was manufactured by using a thermal spray process (Atmospheric Plasma Spray, or APS) and its micro-structure, phase composition and properties of the coating layer were investigated. Initial powder feedstock was composed of an orthorhombic α-MoO3 phase, and the average powder particle size was 6.7 μm. As a result of the APS coating process, a MoO3 coating layer with a thickness of about 90 μm was obtained. Phase transformation occurred during the process, and the coating layer consisted of not only α-MoO3 but also β-MoO3, MoO2. Phase transformation could be due to the rapid cooling that occurred during the process. The properties of the coating layer were evaluated using a nano indentation test. Hardness and reduced modulus were obtained as 0.47 GPa and 1.4 GPa, respectively. Based on the above results, the possibility of manufacturing a MoO3 thick coating layer using thermal spray is presented.
4
Content available Effect of Nb and Mo Addition on the Microstructure and Wear Behavior of Fe-Cr-B Based Metamorphic Alloy Coating Layer Manufactured by Plasma Spray Process
Cho Yong-Hoon, Ham Gi-Su, Park So-Yeon, Kim Choongnyun Paul, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2022
|
Vol. 67, iss. 4
1521--1524
EN
Fe-Cr-B-based metamorphic alloy coating layers were manufactured by plasma spray with a Fe-Cr-B-Mo-Nb composition (hereinafter, M+) powder. The microstructure and wear properties of the coating layers were investigated and compared with a metamorphic alloy coating layer fabricated with commercial m material. XRD analysis revealed that the M and M+ coating layers were composed of α-Fe, (Cr, Fe)2B, and some metallic glass phases. Wear test results showed that M+ coating layers had a superior wear resistance which had 1.48 times lower wear volume than M coating layers. Observations of the worn-out surfaces and cross-sections of the coating layers showed that M+ coating layer had relatively low oxides along the particle boundaries and it suppress a delamination behavior by the oxides.
5
Content available Effect of Microstructure and Unit Cell’s Geometry on the Compressive Mechanical Response of Additively Manufactured Co-Cr-Mo Sheet I-WP Lattice
Park So-Yeon, Kim Kyu-Sik, AlMangour Bandar, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2022
|
Vol. 67, iss. 4
1525--1529
EN
Co-Cr-Mo based sheet I-WP lattice was fabricated via laser powder bed fusion. The effect of microstructure and the I-WP shape on compressive mechanical response was investigated. Results of compression test showed that yield strength of the sheet I-WP was 176.3 MPa and that of bulk Co-Cr-Mo (reference material) was 810.4 MPa. By applying Gibson-Ashby analytical model, the yield strength of the lattice was reversely estimated from that of the bulk specimen. The calculated strength of the lattice obtained was 150.7 MPa. The shape of deformed lattice showed collective failure mode, and its microstructure showed that strain-induced martensitic transformation occurred in the overall lattice. The deformation behavior of additively manufactured sheet I-WP lattice was also discussed.
6
Content available Production of High-Purity Tantalum Metal Powder for Capacitors Using Self-Propagating High-Temperature Synthesis
Lee Yong-Kwan, Sim Jae-Jin, Byeon Jong-Soo, Lee Yong-Tak, Cho Yeong-Woo, Kim Hyun-Chul, Heo Sung-Gue, Lee Kee-Ahn, Seo Seok-Jun, Park Kyoung-Tae
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 4
935--939
EN
In this study, high-purity tantalum metal powder was manufactured via self-propagating high-temperature synthesis. During the process, Ta2O5 and Mg were used as the raw material powder and the reducing agent, respectively, and given that combustion rate and reaction temperature are important factors that influence the success of this process, these factors were controlled by adding an excessive mass of the reducing agent (Mg) i.e., above the chemical equivalent, rather than by using a separate diluent. It was confirmed that Ta metal powder manufactured after the process was ultimately manufactured 99.98% high purity Ta metal powder with 0.5 μm particle size. Thus, it was observed that adding the reducing reagent in excess favored the manufacture of high-purity Ta powder that can be applied in capacitors.
7
Content available Laser Cladding of WC/T-800 Cermet: Fabrication, Microstructure and Wear Properties
Kim Kyoung-Wook, Kim Young-Kyun, Park Sun-Hong, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 3
713--717
EN
This study fabricated a WC/T-800 cermet coating layer with Co-Mo-Cr (T-800) powder and WC powder using laser cladding, and analyzed its microstructure, hardness and wear properties. For comparison, casted bulk T-800 was used. Laser cladded WC/T-800 cermet coating layer showed circular WC phases in the Co matrix, and dendritic laves phases. The average laves phase size in the cermet coating layer and bulk T-800 measured as 7.9 µm and 60.6 µm, respectively, indicating that the cermet coating layer had a relatively finer laves phase. Upon conducting a wear test, the cermet coating layer added with WC showed better wear resistance. In the case of laser cladded WC/T-800 cermet coating layer, abrasion wear was observed; on the contrary, the bulk T-800 showed pulled out laves phases. Based on the above findings, the WC/T-800 cermet coating layer using laser cladding and the relationship between its microstructure and wear behavior were discussed.
8
Content available Effects of ZrO2 and Al2O3 Addition on the Physical Properties of Cu-Mo-Cr Alloy by Liquid Phase Sintering
Cho Yeong-Woo, Sim Jae-Jin, Heo Sung-Gue, Kim Hyun-Chul, Lee Yong-Kwan, Byeon Jong-Soo, Lee Yong-Tak, Lee Kee-Ahn, Seo Seok-Jun, Park Kyoung-Tae
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 3
683--687
EN
In this study, the effect of the addition of ZrO2 and Al2O3 ceramic powders to Cu-Mo-Cr alloy was studied by examining the physical properties of the composite material. The ceramic additives were selected based on the thermodynamic stability calculation of the Cu-Mo-Cr alloys. Elemental powders, in the ratio Cu:Mo:Cr = 60:30:10 (wt.%), and approximately 0-1.2 wt.% of ZrO2 and Al2O3 were mixed, and a green compact was formed by pressing the mixture under 186 MPa pressure and sintering at 1250°C for 5 h. The raw powders were evenly dispersed in the mixed powder, as observed by scanning electron microscopy. After sintering, the microstructures, densities, electrical conductivities, and hardness of the composites were evaluated. We found that the addition of ZrO2 and Al2O3 increased the hardness and decreased the electrical conductivity and density of the composites.
9
Content available Effect of Milling Duration on Oxide-Formation Behavior of Oxide-Dispersion-Strengthened High-Entropy Alloys
Song Yongwook, Kim Daeyoung, Nam Seungjin, Lee Kee-Ahn, Choi Hyunjoo
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 3
735--740
EN
Oxide-dispersion-strengthened high-entropy alloys were produced by hot-pressing a ball-milled mixture of Y2O3 and atomized CoCrFeMnNi powder. The effect of milling duration on grain size reduction, oxide formation behavior, and the resulting mechanical properties of the alloys was studied. Both the alloy powder size and Y2O3 particle size decreased with milling time. Moreover, the alloy powder experienced severe plastic deformation, dramatically generating crystalline defects. As a result, the grain size was reduced to ~16.746 nm and in-situ second phases (e.g., MnO2 and σ phase) were formed at the defects. This increased the hardness of the alloys up to a certain level, although excessive amounts of in-situ second phases had the reverse effect.
10
Content available A Study on the Durability of Dimensionally Stable Electrode in High-Rate Electroplating Process Condition Using Accelerated Life Test
Park Sung Cheol, Jung Yeon Jae, Koo Seokbon, Lee Kee-Ahn, Son Seong Ho
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 3
675--678
EN
In order to the long-term stability of DSE for electroplating process, the lifetime equations were calculated from the results of the accelerated life testing, and the lifetime of DSE was predicted. The nano-embossing pre-treatment led to 2.65 times in the lifetime of DSE. The degradation mechanism of DSE with a thick metal oxide layer for applied highly current density process condition was identified. The improvement of durability of DSE seems to be closely related to adhesion between titanium plate and mixed metal oxide layer.
11
Content available Fabrication and Compressive Properties of Open-Cell Ni-Mo-Cr (Hastelloy) Foams Manufactured by Electrostatic Powder Spraying
Kang Tae-Hoon, Kim Kyu-Sik, Lee Min-Jeong, Yun Jung-Yeul, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2020
|
Vol. 65, iss. 3
1081--1086
EN
An open-cell Ni-Mo-Cr foam was newly manufactured using electrostatic powder spraying process and its room-temperature compressive properties were investigated in this study. For manufacturing Ni-Mo-Cr foam, Ni-Mo-Cr powders were sprayed on the polyurethane pre-form by electrostatic powder spraying process. And then, Ni-Mo-Cr powder sprayed pre-forms were sintered at 1200°C, 1250°C, and 1300°C, respectively. The relative densities of Ni-Mo-Cr foams were measured at 4 ~ 5%. Room tempera-ture compressive curves of ESP Ni-Mo-Cr foams represented the typical compressive 3-stages (elastic, plateau, densification) of open-cell metallic foam. As a result of observation of deformed specimen, the fracture mode found to be changed from brittle to ductile as sintering temperature increased. Based on these findings, correlations between structural characteristics, microstructure, and compressive deformation behavior were also discussed.
12
Content available Effect of Post-Heat Treatment on the Wear Properties of AlSi10Mg Alloy Manufactured by Selective Laser Melting
Park Tae-Hyun, Baek Min-Seok, Sohn Yongho, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2020
|
Vol. 65, iss. 3
1073--1080
EN
Microstructure and wear property of AlSi10Mg alloy manufactured by selective laser melting (SLM) were investigated. Also, the effect of post heat treatment on the mechanical and wear properties was examined. Two kinds of heat treatments (direct aging (DA) and T6) were separately conducted to SLM AlSi10Mg alloy. As-built alloy had a cellular structure formed inside the moltenpool. Eutectic Si was also observed at the cellular boundary in as-built alloy. After DA heat treatment, the cellular structure still remained, and a large amount of nano-size Si particles were newly formed inside the cell structure. Both molten pool and cellular structure disappeared, and the size of Si increased in T6 alloy. The values of Vickers hardness measured as 139.4 HV (DA alloy), 128.0 HV (As-built alloy) and 85.1 HV (T6 alloy), respectively. However, concerning to wear property, T6 alloy showed better wear resistance than other alloys. The correlation between microstructure and wear mechanism of SLM AlSi10Mg alloy was also discussed.
13
Content available Effect of High Frequency Heat Treatment on the Microstructure and Macroscopic Properties of WC-50Ni+Stellite 1 Coating Layer Fabricated by HVOF Spray Process
Ham Gi-Su, Wi Dong-Yeol, Park Sun-Hong, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2020
|
Vol. 65, iss. 3
1087--1092
EN
The microstructure and macroscopic properties of WC-50Ni+stellite 1(Co-Cr-W, ST1) coating layer fabricated by HVOF spray have been investigated. WC-50Ni powder and ST1 powders were mixed in the ratio of 1:0 and 5:5 wt.%, respectively. Argon heat treatment (Ar) and high-frequency heat treatment (H.F.) were conducted on the coating materials. WC was decomposed in the Ar heat treatment specimen, but decomposition of WC was not observed in the H.F. heat treatment specimen. Hardness was measured for as-sprayed WC-50Ni (821.5Hv) and as-sprayed WC-50Ni+ST1 (668.1 Hv). Hardness of Ar heat treatment specimen was reduced by about 14~18% than that of the as-sprayed coating layers. However, when the H.F. heat treatment was performed, the hardness inversely increased by about 6~10% than the as-sprayed coating layer. Based on these results, the method to improve the mechanical property of HVOF sprayed WC-50Ni+ST1 coating layer has also been also discussed.
14
Content available Microstructure and High Temperature Oxidation Properties of Fe-Cr-Ni HK30 Alloy Manufactured by Metal Injection Molding
Wi Dong-Yeol, Kim Young-Kyun, Yoon Tae-Sik, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2019
|
Vol. 64, iss. 2
525--530
EN
This study investigated the microstructure and high temperature oxidation properties of Fe-25Cr-20Ni-1.5Nb, HK30 alloy manufactured by metal injection molding (MIM) process. The powder used in MIM had a bi-modal size distribution of 0.11 and 9.19 μm and had a spherical shape. The initial powder consisted of γ-Fe and Cr23C6 phases. Microstructural observation of the manufactured (MIMed) HK30 alloy confirmed Cr23C6 along the grain boundary of the γ-Fe matrix, and NbC was distributed evenly on the grain boundary and in the grain. After a 24-hour high temperature oxidation test at air atmospheres of 1000, 1100 and 1200°C, the oxidation weight measured 0.72, 1.11 and 2.29 mg/cm2, respectively. Cross-sectional observation of the oxidation specimen identified a dense Cr2O3 oxide layer at 1000°C condition, and the thickness of the oxide layer increased as the oxidation temperature increased. At 1100°C and 1200°C oxidation temperatures, Fe-rich oxide was also formed on the dense Cr2O3 oxide layer. Based on the above findings, this study identified the high-temperature oxidation mechanism of HK30 alloy manufactured by MIM.
15
Content available Manufacturing and Wear Properties of SiC Coating Layer on Zr alloy Fabricated by Vacuum Kinetic Spray Process
Ham Gi-Su, Kim Kyu-Sik, Lee Kee-Ahn
Archives of Metallurgy and Materials
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2019
|
Vol. 64, iss. 2
519--523
EN
This study manufactured a SiC coating layer using the vacuum kinetic spray process and investigated its microstructure and wear properties. SiC powder feedstock with a angular shape and average particle size of 37.4 μm was used to manufacture an SiC coating layer at room temperature in two different process conditions (with different degrees of vacuum). The thickness of the manufactured coating layers were approximately 82.4 μm and 129.4 μm, forming a very thick coating layers. The SiC coating layers consisted of α-SiC and β-SiC phases, which are identical to the feedstock. Cross-sectional observation confirmed that the SiC coating layer formed a dense structure. In order to investigate the wear properties, ball crater tests were performed. The wear test results confirmed that the SiC coating layer with the best wear resistance achieved approximately 4.16 times greater wear resistance compared to the Zr alloy. This study observed the wear surface of the vacuum kinetic sprayed SiC coating layer and identified its wear mechanism. In addition, the potential applications of the SiC coating layer manufactured using the new process were also discussed.
16
Content available High Temperature Random Stack Creep Property of Ni-Cr-Al based Powder Porous Metal Manufactured with Powder Sintering Process
Kang Tae-Hoon, Kim Kyu-Sik, Park Man-Ho, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2019
|
Vol. 64, iss. 2
513--518
EN
Recently, attempts have been made to use porous metal as catalysts in a reactor for the hydrogen manufacturing process using steam methane reforming (SMR). This study manufactured Ni-Cr-Al based powder porous metal, stacked cubic form porous blocks, and investigated high temperature random stack creep property. To establish an environment similar to the actual situation, a random stack jig with a 1-inch diameter and height of 75 mm was used. The porous metal used for this study had an average pore size of ~1161 μm by rolling direction. The relative density of the powder porous metal was measured as 6.72%. A compression test performed at 1073K identified that the powder porous metal had high temperature (800°C) compressive strength of 0.76 MPa. A 800°C random stack creep test at 0.38 MPa measured a steady-state creep rate of 8.58×10-10 s-1, confirming outstanding high temperature creep properties. Compared to a single cubic powder porous metal with an identical stress ratio, this is a 1,000-times lower (better) steady-state creep rate. Based on the findings above, the reason of difference in creep properties between a single creep test and random stack creep test was discussed.
17
Content available Fabrication and Macroscopic Properties of Filler Metal (BCuP-5) on Cu-plate using Laser Cladding Process
Lee Kee-Ahn, Park Joo Hyun, Joo Yeun Ah
Archives of Metallurgy and Materials
|
2019
|
Vol. 64, iss. 2
559--563
EN
This study stacked a thin, dense BCuP-5 (Cu-Ag-P based filler metal) on a Cu-plate using the laser cladding (L.C) process to develop a method to manufacture Ag reducing multilayer clad electrical contact material with an Ag-M(O)/Ag/Cu/BCuP-5 structure. Then, the microstructure and macroscopic properties of the manufactured BCuP-5 coating layer were analyzed. The thickness of the manufactured coating layer was approximately 1.7 mm (maximum). Microstructural observation of the coating layer identified Cu, Ag and Cu-Ag-Cu3P ternary eutectic phases like those in the initial BcuP-5 powder. To evaluate the properties of the manufactured coating layer, hardness and adhesion strength tests were performed. The average hardness of the laser cladded coating layer was 183.2 Hv, which is 2.6 times greater than conventional brazed BcuP-5. The average pull-off strength measured using the stud pull test was 341.6 kg/cm2. Cross-sectional observation of the pulled-off material confirmed that the coating layer and substrate maintained a firm adhesion after pull-off. Thus, the actual adhesion strength of Cu/BcuP-5 was inferred to be greater than 341.6 kg/cm2. Based on the above findings, it was confirmed that it is possible to manufacture a sound Ag reducing multilayer clad electrical contact material using the laser cladding process.
18
Content available Effect of T6 Heat Treatment on the Scratch Wear Behavior of Extruded Al-12wt.%Si Alloy
Kang Yeon-Ji, Kim Jong-Ho, Hwang Jong-Il, Lee Kee-Ahn
Archives of Metallurgy and Materials
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2019
|
Vol. 64, iss. 2
617--622
EN
This study investigated the effect of T6 heat treatment on the microstructure and scratch wear behavior of hypoeutectic Al-12wt.%Si alloy manufactured by extrusion. Microstructural observation identified spherical eutectic Si phases before and after the heat treatment of alloys (F, T6). Phase analysis confirmed Al matrix and Si phase as well as Al2Cu and Al3Ni, Mg2Si in both alloys. In particular, Al2Cu was finer and more evenly distributed in T6 alloy. This resulted in Vickers hardness of T6 alloy that was 2.3 times greater compared to F alloy. The scratch wear test was conducted using constant load scratch test (CLST) mode and multi-pass scratch test (MPST) mode. The scratch coefficient and worn out volume obtained by such were used to evaluate wear properties before and after heat treatment. In the case of T6 alloy, its scratch coefficient was lower than F alloy in all load ranges. After 15 repeated tests to measure worn out volume, F alloy and T6 alloy measured 1.2×10-1 mm3 and 7.8×10-2 mm3, respectively. In other words, the wear resistance of T6 alloy were confirmed to be better than those of F alloy. In addition, this study attempted to identify the microstructural factors that contribute to the better scratch wear resistance of T6 alloy and wear mechanism from surface and cross-section observations after the wear tests.
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