Study On Fabrication And Cutting Performance Of TiC Matrix Ceramic Tools Based On Multi-phase And Multi-scale

Aimed at improving the complex mechanical properties of ceramic tool,based on the new thought for designing multi-phase and multi-scale nanocomposites,a new kind of multi-phase and multi-scale TiC based nanocomposite ceramic tool materials were developed according to the design principle of the ceramic composite material and ceramic-metal composite material of The liquid-phase hot-pressed sintering technology was adopted.The micro-scale and nano-scale Al₂O₃ particles were added into TiC matrix with Ni,Co and Mo as sintering additives.The relationship among sintering process,mechanical properties and microstructure was investigated in this paper. Meanwhile the toughening and strengthening mechanisms as well as the cutting performance was studied systematically.The influence of the content of nano-scale Al₂O₃ on the microstructure and mechanical properties of the multi-phase and multi-scale TiC based nanocomposite ceramic tool materials under the same temperature was investigated.The influence of micron-scale Al₂O₃ content on the microstructure and mechanical properties under the same temperature was investigated.After that,the effect of temperature on the microstructure and mechanical properties of the TA10A5 nanocomposite ceramic tool materials was mainly developed.The new kind of multi-phase and multi-scale TiC based nanocomposite ceramic tool materials TA10A5(TiC matrix with 10 vol%micro-scale Al₂O₃ and 5 vol% nano-scale Al₂O₃)were fabricated successfully with the optimized sintering process of 1600℃under 25MPa and a holding time of 30 minutes.The flexural strength,fracture toughness and Vickers hardness of TA10A5 were 901MPa,8.46 MPa·m^1/2 and 20.43GPa.respectively.The grains were obviously refined by adding the micro-scale and nano-scale Al₂O₃ particles according to the microstructure observation.At the same time,there were more drawn grains and intragranular fracture but low porosity at the cross section.The plastic deformation of the metal phase and crack bridging has great contribution to the material's fracture toughness.The influences of multi-phase and multi-scale on strengthening and toughening mechanisms of the new multi-phase and multi-scale TiC based nanocomposite ceramic tool materials were studied.The binding metal phase Ni,Co and Mo can greatly improve the wettability to the matrix grain,improve combination strength of grain boundary and induce crack bridging,crack transgranulation and crack deflection.Al₂O₃ particles can inhibit the excessive matrix grain growth,enhance the material's mechanical properties and generate crack deflection,crack spinning and residual stress. Simultaneously,the particles can also easily cause dislocation to increase mechanical properties.Multi-scale Al₂O₃ particles can produce toughening mechanisms of both residual stress and crack deflection.Intragranular nano-scale Al₂O₃ particles can induce sub-boundary in the matrix grain,also the metal phase and the nano particle on the boundary can greatly enhance the grain boundary,which result in the intragranulare fracture mode.Compared to the commercial LT55 ceramic tool,the cutting performance and failure mechanism of TA10A5 in continuous machining quenched 40Cr alloy steel, nodular cast iron,quenched and tempered 45# steel and quenched 45# steel were studied.The results showed that TA10A5 was quite suitable to continuously machine quenched 40Cr alloy steel at the low speed,and quite suitable to continuously machine 45# steel at the high speed,the wear resistance and the quality of machining surface obtained with the TA10A5 cutter were much better than that of LT55.However, TA10A5 cutter was not suitabe to continuously machine nodular cast iron.The wearing loss of rake face and rear face was greatly increased with time increasing.In a word,the TA10A5 cutter was very suitable for finishing the above four workpiece materials due to the good quality of maching surface.