Microwave Sintered Three-dimensional Geometry Ceramic Tool And Its Cutting Performance

In this paper,in case of the disadvantages that the current ceramic tool has simple structure and narrow application range,the microwave sintering technology was applied to the field of three dimension groove Ti(C,N)-based cermet tool preparation.After the research of pressing technique,microwave sintering technique and Ti(C,N)-based cermet material system optimization,three-dimensional groove Ti(C,N)-based cermet tool with good mechanical propertiesand and good cutting performance was developed.On this basis,by continuous dry cutting of austenitic stainless steel 1Cr18N i9Ti and quench die steel 40C r,the cutting performance of three-dimensional groove and flat surface cutting tool was compared,on the other side,the wear and breakage mechanism of the tool were analyzed.The effects of pressing pressure on density,shrinkage,mechanical properties and microstructure uniformity of sintered compact were studied by numerical simulation and experiment.The results showed that the relative density of the green compact was stratified with the increase of pressing pressure.Higher pressure could increase the relative density of the green compact,but when the relative density changed greatly,the stress distribution was also very uneven,which would easily produce cracks and other internal defects between layers.The radial shrinkage of the sintered body was larger than the transverse shrinkage,and both the radial shrinkage and the transverse shrinkage would decrease with the increase of pressure,but when the pressure exceeded 300MPa,the change range became smaller.Based on the characteristics of microwave sintering,the influe nce of microwave sintering technology(sintering temperature and holding time)on mechanical properties and microstructure of Ti(C,N)-based cermet materials was studied.The results showed that the rising sintering temperature could promote the uniformit y of microstructure and significantly improve the density and hardness of Ti(C,N)-based cermet,however,the fracture toughness of cermet decreased.The TN6C6M6 sintered at 1600?for 20min had the highest fracture toughness of 12.41±0.33MPa·m^1/2,relative density of 98.40%and Vickers hardness of16.25±0.09 GPa.The effects of different metal phase content ratios on mechanical properties and microstructure of Ti(C,N)-based cermet were studied,and the toughening mechanism of cermet was revealed.The results showed that Co was more significant in improving relative density and fracture toughness than N i,while N i and Co had similar effects in increasing hardness of Ti(C,N)-based cermet.Mo could improve fracture toughness but decrease hardness of Ti(C,N)-based cermet.When the content of metal phase was increased from 3 wt.%to 6 wt.%,relative density and mechanical properties were significantly improved,but as the content of metal phase was higher than 6 wt.%,the improvement was slight.The Ti(C,N)-based cermet with 6 wt.%N i,6 wt.%Co and 6 wt.%Mo had the optimal relative density of 98.37%,Vickers hardness of 16.43±0.65GPa and fracture toughness of 7.61±0.94MPa·m^1/2.Ni and Co formed in the liquid phase could improve the densification of the material and make the microstructure more uniform,and the high content of N i and Co promoted the formation of dimples.The proper proportion of N i and Mo could obviously refine the grains.The effects of pressing pressure on the density,mechanical properties and microstructure of cutting edge and non-cutting edge parts of three-dimensional groove tool were studied.Numerical simulation showed that the relative density gradient on the upper surface of the green compact was large,and it was obviously related to the shape of the groove.The density of the cutting edge area was smaller than that of the non-cutting edge area,and the difference first increased and then decreased with the increase of the pressing pressure.The results showed that the relative density and mechanical properties of the cutting edge and the non-cutting edge were not different under different pressure.Under high pressing pressure,the relative density and mechanical properties of the non-cutting edge were better than that of the cutting edge,but too high pressing pressure would cause defects in the tool,which was not conducive to the use of the tool.The microstructure of the cutting edge and the non-cutting edge of the three-dimensional groove cutting tool were compared under different pressing pressures,the microstructure uniformity and density of the non-cutting edge were better than that of the cutting edge.The metal phase content of cutting edge increased with the increase of pressing pressure.It is the best choice to determine the pressing pressure of 400MPa based on the density,mechanical properties and metal phase content of the cutting edge.In this paper,the cutting properties of the self-developed flat cutting surface and three-dimensional groove Ti(C,N)-based cermet cutting tools for hard working materials such as austenitic stainless steel 1Cr18N i9Ti and quench die steel 40Cr were studied.When austenitic stainless steel was dry-cutted continuously,the cutting performance of three-dimensional groove tool was significantly better than that of flat surface tool.Under the premise of cutting speed V=160m/min,feed rate f=0.1mm/r,back cutting depth a_p=0.1mm,three-dimensional groove tool had the longest cutting distance and the optimal machining surface roughness,and bond wear was the main cause of tool failure.Continuous dry cutting quenched die steel 40C r,the cutting performance of three-dimensional groove tool was significantly superior to the flat surface tool,the cutting speed V=90m/min,feed rate f=0.1mm/r,back cutting depth a_p=0.1mm under the premise of three-dimensional groove cutting tool wear resistance performance was best.When cutting speed V=210m/min,feed rate f=0.1mm/r,back cutting depth a_p=0.1mm,the three-dimensional groove tool had the best machining surface roughness.Groove wear and bond wear were the main causes of tool failure when cutting quencheddie steel 40Cr with a three-dimensional groove tool.When cutting hardened die steel 40Cr with flat surface,groove wear was the main wear on the back surface and crater wear was the main wear on the front surface.