Electro-discharge machining performance of TiCN-based cermets

The present investigation aims at evaluating the die sinking electro-discharge machining (EDM) performance of TiCN–20 wt.% Ni cermets containing 10 wt.% of different secondary carbides: WC, NbC and TaC. Such performance is assessed in terms of making cavity of 1 mm depth on a commercial high speed tool steel (HSS). The material removal rate (MRR) is found to be higher for TiCN–20 wt.% Ni cermet; however tool wear ratio (TWR) is lower for TiCN–20Ni–10TaC cermet. The quality of cermet tool surface has been quantitatively assessed using surface roughness tester and it was observed that the roughness (Ra or Rz) of TiCN–20Ni–10TaC cermet tool surface is lower, when compared with that of other investigated cermets. SEM–EDAX analysis of EDM surfaces reveal melting and evaporation of the binder as well as pull-out and spalling of brittle carbonitride/carbide grains as the dominant wear mechanisms. The layer formation due to solidification of molten layer and/or transfer of material from workpiece is commonly observed for all the cermet tool surfaces.