Papers by Keyword: Electric Discharge Milling

Abstract: Engineering ceramics have been widely employed in the aerospace, automotive and tool field. However, they are difficult to machine due to their high hardness and brittleness. Circumferential electric discharge milling and mechanical grinding compound machining method is employed in this paper. The temperature distribution model for the compound machining of SiC ceramic is established, and the temperature distribution is calculated at different machining conditions. The results show that with the compound machining method, the higher material removal rate can be obtained at rough machining condition, and the better machined surface quality can be obtained at finish machining condition.

Abstract: Material removal mechanisms of Al2O3-based conductive ceramics machined by electric discharge milling in deionized water are investigated. The main components of conductive ceramic samples are Al2O3 (80%), TiC (11%) and WC (9%). The material removal mechanisms by low electric discharge energy are mainly spalling and melting. The material removal mechanisms by high electric discharge energy are mainly melting, evaporation and spalling. With high discharge energy and insufficient cooling conditions, chemical reactions will happen, where TiC and WC are oxidized to dielectric TiO2 and WO3, which will slow down the electric discharge milling processand finally make it stopped.

Abstract: In this paper both electric discharge assisted milling [1, 2] and conventional mechanosynthesis techniques were applied to investigate the effects of milling conditions on the fracture and agglomeration of amorphous CoSiB ribbons produced by planar flow casting. The effect of spark energy on particle shape and size produced by discharge milling was studied. Conventional milling in inert atmosphere for extended periods generally leads to the formation of porous powder particle aggregates, each particle comprised of small amorphous or, after extended milling times, nanocrystalline elements. The mechanism of agglomeration was believed to originate from repeated fracture, deformation and cold welding of individual ribbon elements. In contrast to conventional milling, spark discharge milling was found to induce the formation of predominantly sub-micron single particles of amorphous powder. The morphology of individual particles varied from sub-micron irregular shaped particles to remelted particles, depending on selection of vibrational amplitude during discharge. For high vibrational amplitudes and high energy input a wider range of particles as produced. These included sub-micron particles, remelted particles and welded agglomerates, and nano-sized particles produced as a fume and collected during discharge milling under flowing argon. These results combined with observations that most re-melted particles produced by discharge milling were also amorphous confirmed that extremely high heating and cooling rates are associated with discharge milling of metals. They also confirm the potential of electrical discharge milling as a new route for the synthesis of ultrafine and nanosized powder particles from amorphous ribbon, for possible processing into 3-D shapes.