Development Of TiB₂/Ti(C_0.5,N_0.5)/Al₂O₃ Composite Ceramic Tool Material And Research On Its Cutting Performance

In the existing research,it can be seen that adding Ti(C_0.5,N_0.5)cermets to TiB₂matrix alone can improve the bending strength,but the fracture toughness is low.However,only adding Al₂O₃ceramic can improve the fracture toughness,but the bending strength decreases.In view of the above research,this paper proposes the method of adding Al₂O₃,Ti(C_0.5,N_0.5)and binder[Ni,Mo]into TiB₂at the same time.The new TiB₂based composite ceramic tools TiB₂-Ti(C_0.5,N_0.5)（BTA0）and TiB₂-Ti(C_0.5,N_0.5)-Al₂O₃（BTA1-BTA10）are successfully developed by vacuum hot pressing sintering process.The mechanical properties at room temperature,microstructure and toughening mechanism,friction and wear properties and cutting properties are studied.（1）The addition of Al₂O₃,the content of binder[Ni,Mo],the sintering temperature and holding time of TiB₂/Ti(C_0.5,N_0.5)/Al₂O₃composite ceramic tool materials were optimized in the experiment,and their effects on mechanical properties,phase composition and microstructure were studied.Studies have shown that intermetallic compounds Ni₄Ti₃and NiTiare generated in the product,which significantly enhances the toughness of TiB₂/Ti(C_0.5,N_0.5)/Al₂O₃composite ceramic tool material.The bending strength and fracture toughness of TiB₂/Ti(C_0.5,N_0.5)/Al₂O₃composite ceramic tool materials increased first and then decreased with the increase of Al₂O₃,binder[Ni,Mo]content and sintering temperature.The bending strength and fracture toughness decreased with the increase of holding time.The best ratio and sintering process of TiB₂/Ti(C_0.5,N_0.5)/Al₂O₃composite ceramic tool materials were BTA1,BTA5,BTA65,BTA6,BTA10,the corresponding density were 98.6%,99.3%,99.5%,98.7%,the bending strength were779MPa,897MPa,806MPa,846MPa,the fracture toughness were 8.81MPa·m^1/2、9.71MPa·m^1/2、8.85MPa·m^1/2、9.20MPa·m^1/2,the Vickers hardness is 20.27 GPa,20.03 GPa,21.05 GPa and 20.85 GPa,respectively.（2）Al₂O₃particles in the sintering process can effectively inhibit the growth of matrix grains,reduce the generation of holes and micro cracks in the material,and play a role in grain refinement.Adhesive[Ni,Mo]content can significantly improve the density of composite ceramic materials and fully wetting the grain boundaries of the material,and enhance the bonding strength between grains.However,when the content is too much,the internal agglomeration occurs,resulting in a decrease in mechanical properties.With the increase of sintering temperature,the activity of adhesive[Ni,Mo]increases and the density increases.When the holding time is 60min,the compactness is good,the size of the hard phase is uniform and the distribution is uniform,but the agglomeration of the bonded phase grains occurs,resulting in the decrease of mechanical properties.（3）The BTA0 without Al₂O₃particles and the BTA1,BTA5 and BTA10composite ceramic materials with good mechanical properties were subjected to counter-grinding with GCr15 bearing steel ball under the same load and rotational speed under dry sliding friction conditions.The results show that the friction coefficient of the material is BTA1,BTA0,BTA10 and BTA5.Oxidation wear occurs on the friction surface of the composite material,and the lubricating film TiO₂and B₂O₃are produced,indicating that the composite ceramic material has self-lubricating effect under high speed friction conditions.（4）Continuous cutting experiments were carried out on 45#quenched steel with BTA5 and BTA10 blades with excellent mechanical properties and good wear resistance,and compared with YBC251 NC blade.The results show that when the cutting depth and feed rate are constant,the cutting speed of the three kinds of blades increases from 50 m/min to 90 m/min,and the flank wear and cutting force of the tool decrease under the same cutting path.Therefore,the service life of the tool becomes longer when the cutting speed is 90 m/min.The main reason is that when the cutting speed increases,the temperature of the machining area increases,and there are lubricating films TiO₂and B₂O₃in the tool material,so as to achieve the lubrication effect.The failure modes of the three tools are mainly diffusion wear,bond wear,micro-area brittle spalling and abrasive wear.The wear resistance of the tools from high to low is BTA5,BTA10 and YBC21.