ULTRAFINE CERMETS FOR IMPROVED WEAR RESISTANCE

Abstract

In the present work two cermets were prepared with composition TiCN 10wt%-WC10wt%-Ni 10wt%- Co 10wt%-WC (Ta0) and TiCN 10wt%-TaC 10wt%-WC 10wt%-Ni 10wt%-Co (Ta10). The optimized sintering cycle is a three step process with 5mins holding at 8000C and 10000C and a 3min holding at 13000C. The load applied was 40MPa and heating rate was kept constant at 1000C/min. SEM images of microstructure reveals the formation of core-rim structure for both cermets. Core consists of undissolved WC and TiCN whereas the rim is a solid solution of type (Ti,Ta,W)CN. Fracture toughness and hardness obtained for Ta0 sample are 6.34MPa m1/2, 9.94GPa and 7.8MPa m1/2, 10.98GPa for Ta10. Increase in mechanical properties resulted in an increase of 10% erosive wear resistance for Ta10 over Ta0. SEM image of eroded surface in both cermets show two prominent material removal processes i.e. ductile cutting of metallic phase and brittle fracture of ceramic phase