Papers by Keyword: Hard Particle

Abstract: Electrical discharge machining (EDM) is an excellent technology to machining die and mold, but it is uneasy to obtain mirror-like surface. Powder-Mixed dielectric electrical discharge machining (PMD-EDM) is the innovative technology of EDM process, which can improve the quality of machined surface and applied in EDM finish machining now. The powder is usually hard particles, such as Al, Cu, Cr and Si in PMD-EDM. This paper presents a new research of PMD-EDM with suspending soft particles and abrasive grits in the dielectric fluid, especially focus on surface roughness. Experimental result shows the EDM process with polymer particles and abrasive grits can be carried out in silicone oil and the surface roughness has the finer improvement when increasing the rotation speed. Also, the effect of hard particles suspending in dielectric fluid are also discussed and compared. The surface roughness using polymer particles and abrasive in specific condition was better than only hard particles in silicone oil. Moreover, mixing abrasive and polymer in EDM can perform the polishing process.

Abstract: A novel abrasion-assisted electroforming technique with the orbital motion of cathode is developed. The related theories are studied and experiments of nickel electroforming are carried out. It is confirmed that the hard particles can effectively remove the hydrogen bubbles and nodules by polishing the mandrel surface. A bright, smooth and compact deposit with the average surface roughness of about 0.12m is produced on a polyhedral mandrel.

Abstract: The paper reports on a study regarding the structure of composite layers obtained by electrochemical deposition. The depositions were achieved in a bath formed of a mixture of aqueous solutions of iron salts (iron chloride), cobalt (cobalt sulphate) and solid particles of silicon carbide (SiC) in suspension. Following the electrochemical deposition on composite structures are formed as a thin layer with a metallic matrix (FeCo alloy), reinforced with hard particles of SiC. The structure of the composite layer is uniform and very fine, with crystalline granules under 500 nm. The electrochemically deposited FeCo alloy representing the metallic matrix of the composite layer has a high micro-hardness (864 HV), superior to the same alloy obtained by casting.

Abstract: Austenitic stainless steel has been used as a corrosion resistance material in tough corrosive circumstance. However, austenitic stainless steel has poor wear resistance property due to its low hardness. Tungsten Carbide alloys (WC) are widely used as tooling materials, because of their high hardness and excellent wear resistance property. In this investigation, we apply powder composite process to obtain hard layer of Stainless steel. The composite material was fabricated from planetary ball milled WC powder and SUS316L stainless steel powder and sintered by Pulsed Current Sintering (PCS) method. We also added TiC powder as a hard particle in WC layer. Evaluations of wear properties were performed by pin-on-disk wear testing machine, and a remarkable improvement in wear resistance property was obtained. The weight loss rate of the composite was 1/10 of SUS316L. In addition, it was found that TiC hard particle addition has a positive effect on the wear resistance property. EPMA investigation showed good dispersion of WC hard phase and TiC hard particle with SUS316L matrix.

Abstract: Nickel deposits were electroformed by a novel technique, in which the mandrel rotated in hard particles (such as ceramic beads) filling between the electrodes. The microstructure and microhardness of the deposit were studied by means of SEM, XRD analysis in contrast with the traditional method. The effects of current densities on the surface morphology and microhardness of the deposit were also studied. The results showed that the polishing, impacting and disturbing of hard particles during electrodepositing could affect the microstructure and performance of the deposits. The grains were substantially refined, the preferred orientation of (200) face weakened and the microhardness significantly increased. Moreover, the presented technique could use higher current density and produce bright and smooth deposits.