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Microstructure and Compression Properties of Fe-Cr-B Alloy Manufactured using Laser Metal Deposition

Joo Y.-A., Yoon T.-S., Park S.-H., Lee K.-A.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1459--1462

EN

Fe-Cr-B alloy is a material with precipitation of boride inside Fe matrix, and it features outstanding hardness and wear resistance properties. However, Fe-Cr-B alloy is a difficult material to process, making it difficult to use as a bulk type structure material which requires delicate shapes. This study attempted to manufacture Fe-Cr-B alloy using a 3D printing process, laser metal deposition. This study also investigated the microstructure, hardness and compression properties of the manufactured alloy. Phase analysis results is confirmed that α-Fe phase as matrix and (Cr, Fe)2B phase as reinforcement phase. In the case of (Cr, Fe)2B phase, differences were observed according to the sample location. While long, coarse, unidirectional needle-type boride phases (~11 μm thickness) were observed in the center area of the sample, relatively finer boride phases (~6 μm thickness) in random directions were observed in other areas. At room temperature compression test results confirmed that the sample had a compression strength is approximately 2.1 GPa, proving that the sample is a material with extremely high strength. Observation of the compression fracture surface identified intergranular fractures in areas with needle-type boride, and transgranular fractures in areas with random borides. Based on this results, this study also reviewed the deformation behavior of LMD Fe-Cr-B alloy in relation to its microstructures.

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Manufacturing and Macroscopic Properties of Y2O3 Coating Layer on Ceramic (AlN) Substrate Fabricated by Aerosol Deposition

Wi D.-Y., Ham G.-S., Kim S.-H., Lee K.-A.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1463--1466

EN

This study attempted to manufacture an Y2O3 ceramic coating layer on a ceramic (AlN) substrate using aerosol deposition (AD) and investigated its macroscopic properties. Pure Y2O3 powder with a polygonal shape and average size of 5.0 μm was used as initial feedstock. Using aerosol deposition with suitable process conditions, an Y2O3 coating layer was successfully fabricated on aluminum nitride (AIN). The thickness of the manufactured coating layer was approximately 10 mm. The coating layer consisted of Y2O3 phase identical to that in the initial powder, and no additional oxides were identified. In regard to the roughness of the Y2O3 coating layer, the average roughness (Ra) measured 1.32 μm, indicating that the surface roughness was relatively even compared to the initial powder size (5 μm). Mechanical properties of the Y2O3 coating layer were measured using nano indentation equipment, and the indentation modulus of the Y2O3 coating layer fabricated by aerosol deposition measured 136.5 GPa. The interface of the coating layer was observed using TEM, and the deposition mechanism of the Y2O3 coating layer manufactured by aerosol deposition was also discussed.

3

High Temperature Oxidation Property of SiC Coating Layer Fabricated by Aerosol Deposition Process

Ham G.-S., Kim S.-H., Park J.-Y., Lee K.-A.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1347--1351

EN

This study investigated the high temperature oxidation property of SiC coated layer fabricated by aerosol deposition process. SiC coated layer could be successfully manufactured by using pure SiC powders and aerosol deposition on the Zr based alloy in an optimal process condition. The thickness of manufactured SiC coated layer was measured about 5 μm, and coating layer represented high density structure. SiC coated layer consisted of α-SiC and β-SiC phases, the same as the initial powder. The initial powder was shown to have been crushed to the extent and was deposited in the form of extremely fine particles. To examine the high temperature oxidation properties, oxidized weight gain was obtained for one hour at 1000°C by using TGA. The SiC coated layer showed superior oxidation resistance property than that of Zr alloy (substrate). The high temperature oxidation mechanism of SiC coated layer on Zr alloy was suggested. And then, the application of aerosol deposited SiC coated layer was also discussed.

4

Effect of Strut Thickness on Room and High Temperature Compressive Properties of Block-Type Ni-Cr-Al Powder Porous Metals

Kang B.-H., Park M.-H., Lee K.-A.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1329--1334

EN

This study investigated the effect of strut thickness on the room and high temperature compressive properties of block-type Ni-Cr-Al powder porous metals with ~3000 μm pore size manufactured using a new powder process. Two block-type Ni-Cr-Al porous metals with different strut thicknesses were manufactured. The strut thicknesses of two block foams were 340 μm (A) and 383 μm (B), respectively. Room temperature, 500°C, 650°C and 800°C compressive tests were performed. The compressive results identified typical elastic, plateau and densification regions of foam material in all temperature conditions. Regardless of the strut thickness, compressive strength (maximum peak stress) decreased as deformation temperature increased. In all deformation temperature ranges, the compressive strength measured higher in the porous metal with greater strut thickness (B). The high temperature deformation behavior of powder porous metal was confirmed to be affected by the structural factor and microstructural factor of the porous metal. With the findings described above, this study also discussed the high temperature deformation mechanism of the Ni-Cr-Al metal foam based on fracture surfaces after the high temperature compressions.

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Effect of Heat Treatment on the Microstructure and Tensile Deformation Behavior of Oxide Dispersion Strengthened Alloys Manufactured by Complex Milling Process

Kim Y.-K., Kim J.-H., Gwon J.-H., Lee K.-A.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1335--1340

EN

This study attempted to manufacture an ODS alloy by combining multiple milling processes in mechanical alloying stage to achieve high strength and fracture elongation. The complex milling process of this study conducted planetary ball milling, cryogenic ball milling and drum ball milling in sequential order, and then the microstructure and tensile deformation behavior were investigated after additional heat treatment. The oxide particles distributed within the microstructure were fine oxide particles of 5~20 nm and coarse oxide particles of 100~200 nm, and the oxide particles were confirmed to be composed of Cr, Ti, Y and O. Results of tensile tests at room temperature measured yield strength, tensile strength and elongation as 1320 MPa, 2245 MPa and 4.2%, respectively, before heat treatment, and 1161 MPa, 2020 MPa and 5.5% after heat treatment. This results indicate that the ODS alloy of this study gained very high strengths compared to other known ODS alloys, allowing greater plastic zones.

6

Effect of Heat Treatment on Microstructure and Impact Toughness of Ti-6Al-4V Manufactured by Selective Laser Melting Process

Lee K.-A., Kim Y.-K., Yu J.-H., Park S.-H., Kim M.-C.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1341--1346

EN

This study manufactured Ti-6Al-4V alloy using one of the powder bed fusion 3D-printing processes, selective laser melting, and investigated the effect of heat treatment (650°C/3hrs) on microstructure and impact toughness of the material. Initial microstructural observation identified prior-β grain along the building direction before and after heat treatment. In addition, the material formed a fully martensite structure before heat treatment, and after heat treatment, α and β phase were formed simultaneously. Charpy impact tests were conducted. The average impact energy measured as 6.0 J before heat treatment, and after heat treatment, the average impact energy increased by approximately 20% to 7.3 J. Fracture surface observation after the impact test showed that both alloys had brittle characteristics on macro levels, but showed ductile fracture characteristics and dimples at micro levels.