NANO STRUCTURED TI (CN) BASED CERMETS

Abstract

The present work deals with the samples prepared with composition TiCN-10wt%WC-10wt%TaC-10wt%Co-10wt%Ni at different sintering parameters to check the change in microstructure and the resulting changes that accompanies with the hardness and fracture toughness. The sintering parameters were changed to achieve a high dense material. The final temperature was kept at 1200℃, 1300℃, 1350℃ and 1500℃. In all cases the holding time was kept at 3 min at the final temperature. The heating rate was kept at 100℃/min for initial samples and 600℃/min for the last three samples. Load applied was 40MPa. SEM images reveals the formation of core-rim structure for the samples. Core consists of undissolved TiCN whereas the rim consist of a solid solution of (Ti,Ta,W)CN. The microstructure was of spheroidal shape due to grain shape accommodation. The Carbide (core+rim) size was the main factor the changes in the mechanical properties of the sintered samples. Hardness and fracture toughness of the samples sintered at 1350℃ and 1500℃ were 10.79GPa, 6.51 MPa√m and 16.11GPa, 7.70 MPa√m. There was a decrease in the carbide (core+rim) size which led to an increase in the mechanical properties and decrease in the wear volume of the sample. The fracture morphology of the sample revealed the presence of mix of two fracture mechanism that is trans-granular fracture and intra-granular grain fracture. The worn out region showed the presence of oxides which was confirmed from FESEM-EDS analysis