Fabrication and mechanical properties evaluation of NbC-Ni cermets reinforced with B4C and ZrB2

Abstract

NbC-Ni cermet are a possible candidate for replacing WC-Co cermet cutting tools. It also overcomes the shortcomings of WC-Co tools. To study the fabricability of NbC-Ni cermets, firstly cermets with 8, 10 and 12 wt. % of Ni were fabricated and analyzed. Among these 12wt % Ni (NbC12Ni) cermet demonstrated an ideal combination of properties with the hardness of 1028 Hv, a flexural strength of 547.140 N/mm2, a fracture toughness of 11.28 MPa m1/2 and 99.5% densification. Further to have a better combination of hardness and strength addition of 2 wt. % B4C (>5 um), 2 wt. % B4C (3 um), and 5 wt. % ZrB2 reinforcements in NbC12Ni system were studied. 2 wt. % B4C (3 um) reinforced NbC12Ni (NbC12Ni2B4C) exhibited the maximum hardness of 1235 Hv and a flexural strength of 506.217 N/mm2 with 93.2% densification. Moreover, to improve the sinterability Ti was added and holding time was varied. Increase in holding time improved the densification in both B4C and ZrB2 system, whereas Ti added only in B4C system (NbC12Ni1.2Ti2B4C) resulted in drastic improvement in the densification and demonstrated the maximum hardness of 1390.6 Hv and a flexural strength of 506.138 N/mm2 with 96.8% densification.