Research On Carbon Nano-tubes Enhancing Ti(C,N)-based Cermets Cutting Tool Material

In this paper，Ti(C,N)-based cermets cutting tool materials were prepared by powdermetallurgy technology with Ti(C,N) as raw materials, Mo and Ni as binders, VC and Cr3C2ashard addition phases, C as removing oxygen additive. The effects of WC, Carbon Nano Tubes(CNTs) addition and sintering process on the microstructure and mechanical properties ofTi(C,N)-based cermets were investigated by scanning electron microscope(SEM),transmission electron microscope (TEM), X-ray diffraction (XRD).The development process, properties and applications, and the microstructure ofTi(C,N)-based cermets were outlined, and the development trends were pointed out;meanwhile, the development trend of CNTs and CNTs enhancing cermets were also briefed.Based on above work，the purpose, content and technical route of this dissertation werepointed out.The raw materials, manufacturing process and testing methods were brieflyintroduced.Above all, the effects of WC addition on the microstructure and mechanical properties ofTi(C,N)-based cermets were studied. Experiment results show that the microstructures ofWC/Ti(C,N)-based cermets exist black core-grey rim structure; the microstructure has a trendto become finer with the increase of WC content; the bending strength and the fracturetoughness were trended to increase and then decrease with increasing of WC content, whilethe hardness increases; By comparing the properties of the material is relatively good withWC10wt%, the bending strength, the hardness increases, and the fracture toughness wererespectively reached1150.91MPa,14.04GPa,8.04MPa·m1/2, and respectively51.00%,14.43%and19.47%improved comparing the mechanical properties of Ti(C,N)-based cermetwithout WC contented.Then the CNTs were dealt with acidification, sensitization, activation and nickel plating.From the TEM pictures, it can be seen that the better surface performance of CNTs wereobtained after acidification processing, and the Ni were plated relatively well-distributed onthe CNTs. The effect of CNTs addition acidulated on microstructure and mechanicalproperties of CNTs/Ti(C,N)-based cermets were studied. Experiment results show that theproperties of the material is relatively good with CNTs1.0wt%, the bending strength, thehardness increases, and the fracture toughness were respectively1295.91MPa,15.19GPa and9.27MPa·m1/2, respectively12.60%,6.15%and15.30%improved comparing the mechanicalproperties of Ti(C,N)-based cermets without CNTs contented. And then, the contents of CNTs deposited Ni was determined0.8wt%,1.0wt%and1.2wt%according to the the results of the research on different CNTs contents acidulated ofthe CNTs/Ti(C,N)-based cermets. The effect of CNTs contents deposited Ni and sinteringprocess on Ti(C,N)-based cermets were studied by orthogonal test, the best content andpreparation condition was adding1wt%CNTs deposited Ni, sintering in1460℃holding30min and the molding pressure is25MPa by the analysis of the orthogonal results, andsuccessfully verified the conclusion. All performance of prepared M10were improved, thebending strength, the hardness increases, and the fracture toughness were respectively1327.43MPa,15.11GPa and9.86MPa·m1/2, respectively15.33%,7.62%and22.64%improved comparing the mechanical properties of Ti(C,N)-based cermets without CNTscontented.Finally, mechanisms of CNTs enhancing Ti(C,N)-based cermets were studied. The mainfracture mechanisms of CNTs/Ti(C,N)-based cermets are transgranular fracture betweenceramic phase, intergranular fracture between small grain size ceramics and ceramic phaseand between ceramic phase and metal phase, and existing a lot of rip edges; The maintoughening mechanisms of CNTs reinforced Ti(C,N)-based cermets are bridging of CNTs,pulling of CNTs, crack bowing, crack deflection and crack branching, micro holes toughening,residual stress toughening and interface toughening and so on; The anti-friction wear-resistingmechanisms of CNTs is CNTs can form a layer thin film that easy to shear on the surface offriction in the process of friction and wear, that not only reduce the friction coefficient, butalso do a certain degree of filling and repair of friction surface, as a result the wear rate islower.