Study On Ti(C,N) Cermets Reinforced By Carbon Fiber Or Nano-particles Through Hot-press Sintering

Mechanical performance of Ti(C,N)-based cermet is deeply influenced by its microstructure. In order to improve the strength and toughness of Ti(C,N)-based cermet without significantly reducing its hardness, the relation between microstructure and mechanical properties of Ti(C,N)-based cermets composited with carbon fiber or nanoparticles was investigated.In this dissertation, Ti(C,N)-based ceramics were fabricated through hot-press sintering on the basis of fiber toughening ceramic materials theory and nanometer compound phase toughening ceramic materials theory, by using pre-oxidized polyacrylonitrile(PAN) fibers and nano-powders(nano AlN, nano ZrC) as the additives. The results show that:(1) Ti(C,N)-NbC-Mo2C-Ni cermets with different amounts(0-25 vol.%) of PAN fibers were fabricated by hot-press sintering under N2. XRD and EDX analyses confir m the transformation of the PAN fibers into carbon fibers during the designed sintering process. With increasing addition fraction of PAN, the flexural strength and fracture toughness of the cermets first increased and then decreased. Both the hardness and relative density of the cermets decreased with increasing added fraction of PAN.(2) Ti(C,N)-based cermets were prepared by hot-press sintering through adding various amounts of AlN nano-powder(0-20 wt.%) into Ti(C,N)-WC-Mo-Ni-Co system. The microstructure and mechanical properties of the prepared cermets were investigated. For the prepared cermets, as the the added fraction of ZrC nano powders increased, the relative density first increased then decreased, and the hardness and fracture toughness first increased then decreased. The flexural strength decreased with increasing added fraction of AlN nano powders.(3) Ti(C,N)-based cermets were prepared by hot-press sintering through add ing various amounts of ZrC nano powders(0-25 wt.%) into Ti(C,N)-WC-Mo-Ni-Co system. The microstructure and mechanical properties of the prepared cermets were investigated. For the prepared cermets, as the the added fraction of ZrC nano powders increased, the relative density first increased then decreased and the comprehens ive mechanical properties(including Vickers hardness, bending strengthas as well as the fracture toughness) decreased.