Study On Arc Erosion Behaviour Of Cu-Ti₃SiC₂Composite

The ternary compound Ti3SiC2is the most studied member of the MAX phasefamily. In the recent years, it has triggered intense research efforts due to its uniqueproperties. It has higher electrical and thermal conductivity than those of titaniummetal, and has high-temperature-oxidation resistance. Ti3SiC2also exhibits excellentproperties such as high strength at high temperatures, high thermal stability,high-thermal shock resistance, good machinability, etc. Its overall properties satisfy thebasic requirements of electrical contact materials. It has been declared that Ti3SiC2film has the possibility to be used as an electrical contact for silicon carbide devices. Inthis paper, the vacuum arc erosion characteristics of Ti3SiC2particles reinforcedCu-matrix composites were investigated.The arc erosion behavior of high-purity Ti3SiC2in vacuum was investigated byX-ray diffraction (XRD), scanning electron microscope (SEM), Energy DispersiveX-Ray Spectroscopy (EDX), and micro-Raman Spectroscopy. From the resultsobtained, Ti3SiC2is unstable due to the high energy intensity and high temperature ofthe vacuum arc. The dissociation of Ti3SiC2takes place at the sample surface, resultingin the formation of solid TiCxand gaseous Si. TiCxis ejected from cathode to thesurface of anode while Si is evaporated to the vacuum chamber. The micro-Ramanresults reveal that, small amounts of carbon appeared as a by-product of thedissociation. The decomposition of Ti3SiC2into non-stoichiometric TiCx, amorphouscarbon and other by-products was detected on the anode surface. The surfacemorphology was revealed by scanning electron microscope and3D super depth digitalmicroscope. Different kinds of anode craters with diameters varying from a fewmicrons to a few hundred microns were observed on the anode surface. The smallercraters are flower-like shaped with a sphoiroidal protrusion pointing out from thecenter of the crater bottom. The larger craters have a diameters greater than onehundred microns but without the central protrusion and the crater is surrounded bycollapse-fissure.The Ti3SiC2particles on the Cu-Ti3SiC2cathode surface are also proved to produce TiCxunder the impact of the vacuum arc. Ti3SiC2is more prone to be erodedthan Cu matrix in the vacuum breakdown process. Different reaction phases will beformed on the the cross section of Cu-Ti3SiC2cathode, due to the extreme temperatureof the vacuum arc. It seems that Ti element and Si element have the tendency to bedepleted after long period of vacuum breakdown test. The reactions between Cu andTi3SiC2could be detected on the surface of a Cu-Ti3SiC2cathode after the vacuumbreakdown. Even on the inert Cu-Ti3SiC2anode, the temperature is so high thatmaking the reaction between Cu and Ti3SiC2possible. It is also found that, after thefirst vacuum breakdown, the Cu-Ti3SiC2sample with a higher content of Ti3SiC2obtained a rougher surface. At the meantime, the cathode erosion rate of Cu-Ti3SiC2composites is found increasing with the increase of Ti3SiC2content. The cathodeerosion rate of sample CuTSC25is twice that of pure Cu.The arc erosion behavior of WC and TiC in vacuum were investigated forcomparison. Cracks were found on the surface of a TiC cathode after the firstbreakdown. The TiC cathode is crushed after exposed to50arcings. Inspection of themicrograph reveals that brittle intergranular fracture is the dominant mode of failure.The deposition of amorphous carbon on the Mo anode indicated that the decompositionof TiC on its counterpart TiC cathode. Some microcracks were also found on thesurface of WC cathode after the first breakdown. Bigger cracks appear on the surfaceof WC cathode under100arcings, indicating that it is ceramic in nature. Amorphouscarbon is also proven to be one of the decomposition products of WC. However, WC isproven to be much stable than TiC under the impact of the vacuum arc.The arc erosion characteristics of WC and TiC particles reinforced Cu-matrixcomposites were investigated. TiC is more prone to be eroded than Cu matrix duringthe vacuum breakdown process. After the first vacuum breakdown, the Cu-TiC samplewith a higher content of TiC obtained a rougher surface. Due to the addition of brittleTiC, Cu-TiC composite may exhibit good anti-welding capability. The melting of WCin Cu-WC composite can absorb a great deal of energy due to its high melts point. Theunmelted WC particles can alleviate sputtering on the cathode surface, and restrain theerosion pools from further expansion. WC is much stable than Ti3SiC2and TiC under influence of the vacuum arc.Anode craters were observed on the surface of TiC and WC anode, respectively.The anode crater on TiC anode is surrounding by Cu particles and the anode crater onWC is covered by Cu depositions. These differences in appearance maybe come fromthe different characters of TiC and WC.