The enamel powders used traditionally in Korea are produced by a ball-milling process. Because of their irregular shapes, enamel powders exhibit poor flowability. Therefore, polygonal enamel powders are only used for handmade cloisonné crafts. In order to industrialize or automate the process of cloisonné crafts, it is essential to control the size and shape of the powder. In this study, the flowability of the enamel powders was improved using the spheroidization process, which employs the RF plasma treatment. In addition, a simple grid structure and logo were successfully produced using the additive manufacturing process (powder bed fusion), which utilizes spherical enamel powders. The additive manufacturing technology of spherical enamel powders is expected to be widely used in the field of cloisonné crafting in the future.

In this study, two types of SKD61 tool-steel samples are built by a selective laser melting (SLM) process using the different laser scan speeds. The characteristics of two kinds of SKD61 tool-steel powders used in the SLM process are evaluated. Commercial SKD61 tool-steel power has a flowability of 16.68 sec/50 g and its Hausner ratio is calculated to be 1.25 by apparent and tapped density. Also, the fabricated SKD61 tool steel powder fabricated by a gas atomization process has a flowability of 21.3 sec/50 g and its Hausner ratio is calculated to be 1.18. Therefore, we confirmed that the two powders used in this study have excellent flowability. Samples are fabricated to measure mechanical properties. The highest densities of the SKD61 tool-steel samples, fabricated under the same conditions, are 7.734 g/cm³ (using commercial SKD61 powder) and 7.652 g/cm³ (using fabricated SKD61 powder), measured with Archimedes method. Hardness is measured by Rockwell hardness testing equipment 5 times and the highest hardnesses of the samples are 54.56 HRC (commercial powder) and 52.62 HRC (fabricated powder). Also, the measured tensile strengths are approximately 1,721 MPa (commercial SKD61 powder) and 1,552 MPa (fabricated SKD61 powder), respectively.

Citations

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• Microstructural effects on the tensile and fracture behavior of selective laser melted H13 tool steel under varying conditions
  Jungsub Lee, Jungho Choe, Junhyeok Park, Ji-Hun Yu, Sangshik Kim, Im Doo Jung, Hyokyung Sung
  Materials Characterization.2019; 155: 109817.     CrossRef

The friction characteristics of Al-Fe alloy powders are investigated in order to develop an eco-friendly friction material to replace Cu fiber, a constituent of brake-pad friction materials. Irregularly shaped Al-Fe alloy powders, prepared by gas atomization, are more uniformly dispersed than conventional Cu fiber on the brake pad matrix. The wear rate of the friction material using Al-8Fe alloy powder is lower than that of the Cu fiber material. The change in friction coefficient according to the friction lap times is 7.2% for the Cu fiber, but within 3.8% for the Al-Fe alloy material, which also shows excellent judder characteristics. The Al-Fe alloy powders are uniformly distributed in the brake pad matrix and oxide films of Al and Fe are homogeneously formed at the friction interface between the disc and pad, thus exhibiting excellent friction and lubrication characteristics. The brake pad containing Al-Fe powders avoids contamination by Cu dust, which is generated during braking, by replacing the Cu fiber while maintaining the friction and lubrication performance.

In this study, H13 tool steel sculptures are built by a metal 3D printing process at various laser scan speeds. The properties of commercial H13 tool steel powders are confirmed for the metal 3D printing process used: powder bed fusion (PBF), which is a selective laser melting (SLM) process. Commercial H13 powder has an excellent flowability of 16.68 s/50 g with a Hausner ratio of 1.25 and a density of 7.68 g/cm³. The sculptures are built with dimensions of 10 × 10 × 10 mm3 in size using commercial H13 tool steel powder. The density measured by the Archimedes method is 7.64 g/cm³, similar to the powder density of 7.68 g/cm³. The hardness is measured by Rockwell hardness equipment 5 times to obtain a mean value of 54.28 HRC. The optimum process conditions in order to build the sculptures are a laser power of 90 W, a layer thickness of 25 μm, an overlap of 30%, and a laser scan speed of 200 mm/s.

Citations

Citations to this article as recorded by  

• Spheroidization of Enamel Powders by Radio Frequency Plasma Treatment and Application to Additive Manufacturing
  Ki-Bong Kim, Dong-Yeol Yang, Yong-Jin Kim, Jungho Choe, Ji-Na Kwak, Woo-Hyung Jung
  Journal of Korean Powder Metallurgy Institute.2020; 27(5): 388.     CrossRef
• Microstructural effects on the tensile and fracture behavior of selective laser melted H13 tool steel under varying conditions
  Jungsub Lee, Jungho Choe, Junhyeok Park, Ji-Hun Yu, Sangshik Kim, Im Doo Jung, Hyokyung Sung
  Materials Characterization.2019; 155: 109817.     CrossRef
• Nano-mechanical Behavior of H13 Tool Steel Fabricated by a Selective Laser Melting Method
  Van Luong Nguyen, Eun-ah Kim, Jaecheol Yun, Jungho Choe, Dong-yeol Yang, Hak-sung Lee, Chang-woo Lee, Ji-Hun Yu
  Metallurgical and Materials Transactions A.2019; 50(2): 523.     CrossRef
• Correlation between Microstructure and Mechanical Properties of the Additive Manufactured H13 Tool Steel
  Woojin An, Junhyeok Park, Jungsub Lee, Jungho Choe, Im Doo Jung, Ji-Hun Yu, Sangshik Kim, Hyokyung Sung
  Korean Journal of Materials Research.2018; 28(11): 663.     CrossRef
• Evaluation of Strain-Rate Sensitivity of Selective Laser Melted H13 Tool Steel Using Nanoindentation Tests
  Van Nguyen, Eun-ah Kim, Seok-Rok Lee, Jaecheol Yun, Jungho Choe, Dong-yeol Yang, Hak-sung Lee, Chang-woo Lee, Ji-Hun Yu
  Metals.2018; 8(8): 589.     CrossRef
• Comparison of Nano-Mechanical Behavior between Selective Laser Melted SKD61 and H13 Tool Steels
  Jaecheol Yun, Van Nguyen, Jungho Choe, Dong-Yeol Yang, Hak-Sung Lee, Sangsun Yang, Ji-Hun Yu
  Metals.2018; 8(12): 1032.     CrossRef
• A study about sculpture characteristic of SKD61 tool steel fabricated by selective laser melting(SLM) process
  Jaecheol Yun, Jungho Choe, Ki-Bong Kim, Sangsun Yang, Dong-Yeol Yang, Yong-Jin Kim, Chang-Woo Lee, Chang-Woo Lee
  Journal of Korean Powder Metallurgy Institute.2018; 25(2): 137.     CrossRef