Electrical discharge machining of B4C–TiB2 composites

The interrelationships between the microstructure and electrical discharge machining (EDM) behaviour of B4C–TiB2 composites with respectively 30, 40 and 60 vol.% TiB2 are investigated. Special attention was given to the influence of the grain size on the EDM behaviour by producing composites with an ultrafine TiB2 phase using in situ synthesis during PECS. The experimental work revealed that 40 vol.% of TiB2 results in an optimal material removal rate while the surface roughness for rough cut EDM decreases with increasing TiB2 content. The finer microstructure of the ultrafine composite shows higher MRR's and lower Ra values than the commercial powder based composites. The major material removal mechanism for the PECS based composites was melting. The 3 point bending strength of all composites after grinding, EDM rough cut and EDM finish cut was not statistically different and about 800 MPa. The EDM recast layer was analysed by X-ray photoelectron spectroscopy.