The Experimental Research And Numerical Simulation Of Electro-spark Surface Strengthening

Electro-spark surface strengthening is a technology, which makes use of thehigh-energy local pulse discharge between tool electrode material and workpiecematerial when strengthening and the tool electrode material melts into the substratesurface quickly, alloys the two materials at the surface of substrate through physicaland chemical metallurgy process at the local high temperature and strengthening layeris formed. The technology has advantages, for example strengthening equipment aresimple and flexible and easy to use. The strengthening layer, which has excellentperformance, is got.Firstly, variable surface strengthening technology are introduced and electro-sparksurface strengthening is compared with other surface strengthening technology;Secondly, principle, realization conditions and so on of electro-spark surfacestrengthening are introduced; Thirdly, the temperature and stress fields are simulatedon ANSYS by building finite element model. The results show that the temperatureand stress fields in work-piece move with the strengthening point, the shape of thetemperature field is cometic; there are highest temperature and temperature gradient atthe strengthening point; the temperature field concentrates on the surface ofwork-piece; the temperature has superposition effect in the process of electro-sparksurface strengthening, the boundary of work-piece has great influence on distributionof temperature field; the node temperature of work-piece surface has feature that thetemperature rises quickly and declines slowly; the deformed displacement is obviousin the process of electro-spark surface strengthening; the stress field in work-piece gradually tends to stabilize as the strengthening point moves and stress concentrates onstrengthening region; the substrate material expands and has plastic deformation due tolots of heat in the region of strengthening point, which is shackled by surroundingcooler area and horizontal compression stress is generated，the region gradually coolsand has elastic contraction with the strengthening point moves and the compressionstress gradually changes into tensile stress; the stress field got by strengthening theedge is different from stress field got by strengthening the non-edge region, which iscaused by the heat can’t spread in fringe areas, so edge conditions should be paidattention in the actual production; The deformed displacement caused by heat has greatinfluence on thermal spread, which leads to change of stress field in work-piece;Finally, some experiments are done， the relations between strengthening time,capacitance and surface roughness of strengthening layer, are researched andmicro-hardness of strengthening layer is measured, the results show that the surfaceroughness becomes big as strengthening time increases, it becomes big as capacitanceincreases within a certain range and then becomes small as capacitance increases, themicro-hardness of strengthening layer is HV1843,which is much higher thansubstrate’s micro-hardness that is HV146,so electro-spark surface strengthening greatlyimproves surface micro-hardness of the substrate.The electrode material used in the experiment is SiC rod that is new, whichenlarges available electrode materials.