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Surface Modification of Self-Consolidated Microporous Ti Implant Compacts Fabricated by Electro-Discharge-Sintering in Air

Jo Y. J., Yoon Y. H., Kim Y. H., Chang S. Y., Kim J. Y., Lee Y. K., Van Tyne C. J., Lee W. H.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1287--1291

EN

A single pulse of 0.75-2.0 kJ/0.7g of atomized spherical Ti powders from 300 mF capacitor was applied to produce a microporous Ti implant compact by electro-discharge-sintering (EDS). A solid core in the middle of the compact surrounded by a microporous layer was found. X-ray photoelectron spectroscopy was employed to study the surface characteristics of the EDS Ti compact and it revealed that Ti, C and O were the main constituents on the surface with a smaller amount of N. The surface was lightly oxidized and was primarily in the form of TiO2 resulting from the air oxidation during EDS processing. The lightly oxidized surface of the EDS compact also exhibited Ti nitrides such as TiN and TiON, which revealed that the reaction between air constituents and the Ti powders even in times as short as 128 msec.

2

Spontaneous Formation of Titanium Nitride on the Surface of a Ti Rod Induced by Electro-Discharge-Heat-Treatment in an N2 Atmosphere

Lee W. H., Yoon Y. H., Kim Y. H., Lee Y. K., Kim J. Y., Chang S. Y.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1281--1285

EN

A single pulse of 2.0 to 3.5 kJ of input energy from a 450 mF capacitor was applied to a commercially pure Ti rod in a N2 atmosphere. The surface of the Ti rod transformed from TiO2 into titanium nitride in times as short as 159 msec, providing a bimodal morphology of the cross-section. A much higher value of hardness that was observed at the edge of the cross-section was attributed to nitrogen-induced solid-solution hardening that occurred during the electrical discharge process. The activation energy (Ea) for the diffusion process was estimated to be approximately 86.9 kJ/mol. Results show that the electrical discharge process is a possible potential method for the nitriding of Ti; advantages include a short processing time and control of the nitrided layer without dimensional changes.

3

Self-Consolidation Mechanism of Ti5Si3 Compact Obtained by Electro-Discharge-Sintering Directly from Physically Blended Ti-37.5 At.% Si Powder Mixture

Chang S. Y., Cheon Y. W., Yoon Y. H., Kim Y. H., Kim J. Y., Lee Y. K., Lee W. H.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1299--1302

EN

Characteristics of electro-discharge-sintering of the Ti-37.5at.% Si powder mixture was investigated as a function of the input energy, capacitance, and discharge time without applying any external pressure. A solid bulk of Ti5Si3 was obtained only after in less than 129 μsec by the EDS process. During a discharge, the heat is generated to liquefy and alloy the particles, and which enhances the pinch pressure can condensate them without allowing a formation of pores. Three step processes for the self-consolidation mechanism during EDS are proposed; (a) a physical breakdown of oxide film on elemental as-received powder particles, (b) alloying and densifying the consolidation of powder particles by the pinch pressure, and (c) diffusion of impurities into the consolidated surface.

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Self-Consolidation and Surface Modification of Mechanical Alloyed Ti-25.0 at.% Al Powder Mixture by Using an Electro-Discharge Technique

Chang S. Y., Jang H. S., Yoon Y. H., Kim Y. H., Kim J. Y., Lee Y. K., Lee W. H.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1293--1297

EN

Electrical discharges using a capacitance of 450 μF at 0.5, 1.0, and 1.5 kJ input energies were applied in a N2 atmosphere to obtain the mechanical alloyed Ti3Al powder without applying any external pressure. A solid bulk of nanostructured Ti3Al was obtained as short as 160 μsec by the Electrical discharge. At the same time, the surface has been modified into the form of Ti and Al nitrides due to the diffusion process of nitrogen to the surface. The input energy was found to be the most important parameter to affect the formation of a solid core and surface chemistry of the compact.