Effects of sintering processes on mechanical properties and microstructure of TiB_2-TiC + 8 wt% nano-Ni composite ceramic cutting tool material

摘要

TiB_2-TiC composite powder was prepared by ball-milled with ethanol and vacuum dry, and TiB_2-TiC+8 wt% nano-Ni composite ceramic cutting tool material was sintered using vacuum hot-pressed sintering technique by six processes which included the different holding stages and times. The effects of sintering processes on the mechanical properties and microstructure were investigated. The polished surface and fracture surface of TiB2-TiC+8wt% nano-Ni ceramics sintered by the different sintering processes were observed by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy-dispersive spectrometry (EDS), and the relationships between mechanical properties and microstructure were discussed. The mechanical properties and microstructure depended mainly on the total holding time and the different holding stages. The longer holding time and multiple holding stages led to coarsening of TiB_2 and TiC grains, formation of pores and the brittle rupture of grains, which deteriorated the mechanical properties of TiB_2-TiC + 8 wt% nano-Ni ceramic. TiB_2-TiC + 8 wt% nano-Ni composite ceramic cutting tool material sintered by SP6 process exhibited the optimum resultant mechanical properties because of its finer microstructure and higher relative density, and its flexural strength, fracture toughness and hardness were 916.8 MPa, 7.80 MPa m~(1/2) and 22.54 GPa, respectively.