Development And Application Of Cermet Tool Based On Multilayer Core-shell Microstructure

In this paper,aiming at the difficult processing problems of hard-to-machine materials,facing the requirements of strengthening and toughening and reducing friction of Ti?C,N?-based cermet tools,the core-shell nano solid lubricant was introduced into cermet tool system,and the design idea of cermet tools with multilayer core-shell microstructure was proposed.The Ti?C,N?-based self-lubricating cermet tools with multilayer core-shell microstructure with excellent performance were successfully prepared,so that the mechanical properties and self-lubricating properties were unified.The effects of multilayer core-shell microstructure on the mechanical properties,friction and wear properties and cutting properties of cermet tools were studied.A new type of self-lubricating cermet tool with multilayer core-shell microstructure was successfully prepared by vacuum hot pressing sintering process andcoated Ca F2?Ca?nano-composite powder as the additive phase of Ti?C,N?-based self-lubricating cermet material.The experimental results showed that by coating a layer ofon the surface of Ca F2 powder and introducing it into Ti?C,N?-Mo-Co-Ni?TM?material system,a multilayer core-shell microstructure of Cacould be formed inside the material by utilizing the high temperature liquid phase diffusion mechanism of metal Mo-Co-Ni phase during sintering.Compared with the traditional Ti?C,N?-Mo-Co-Ni cermet materials,the fracture toughness and hardness of the Ti?C,N?/Mo-Co-Ni/10vol%Cacermet materials were improved respectively 31.83%,24.25%;Compared with cermets that directly added Ca F2 andand did not form a multilayer core-shell microstructure,the hardness and fracture toughness of TMC@10 cermet tools increased by 24.31%and 22.56%,respectively,reaching 23.93 GPa,9.94 MPa·m^1/2;during the hot-pressing sintering process,the intermediate layercovers the core nano-Ca F2 particles,which effectively prevents Ca F2 from growing abnormally and prevented excessive residual stress in the crystal;the Mo-Co-Ni metal phase of the shell could effectively prevent the dislocation expansion within the crystal;the formation of multilayer core-shell microstructure was the main reason for the improvement of the mechanical properties of the material.The frictional wear properties of multilayer core-shell microstructure Ti?C,N?-based self-lubricating cermet tool materials were investigated using a spherical disc with substrates.The coefficient of friction and wear rate of the tool material decreases with the increase of Cacoating powder content,the optimum value of Capowder was 10%,at this time the solid lubricant precipitates to form a lubricating film,the self-lubricating effect was better.Both the coefficient of friction and the wear rate increase when the cladding powder content was high.The coefficient of friction of the tool material decreased with increasing load;the wear rate increased with increasing load;on the other hand,with increasing load,the cermet tool wear rate rose faster when the critical load of 25 N was exceeded.The friction coefficient of the multi-layered core-shell microstructure Ti?C,N?-based cermet tools increased slightly and then decreases,and then tended to continue to increase when the speed reaches 180 m/min;the wear rate decreases and then increases with increasing speed.The cutting performance of the multilayer core-shell microstructure Ti?C,N?-based cermet cutting 300M high-strength steel was investigated.The experimental results show that the optimal cutting amount for TMC@10 cermet cutting 300M high-strength steel was?_c=200 m/min,?=0.102 mm/r,(6(6=0.2 mm,the flank wear and workpiece surface roughness show a trend of decreasing first and then increasing under different cutting speed and cutting amounts of backlash.By testing different components of cermet tools to process 300M high-strength steel at the same cutting amount,adding Cacoating powder to form a cermet tool with a multi-layer core-shell structure,significantly reducing cutting force and cutting temperature,increasing tool life improves the surface machining quality of the workpiece,among which TMC@10 cermet tool had better cutting performance.By testing TM cermet tools and TMC@10 cermet tools for processing 300M high-strength steel under different lubrication conditions,TM tools had reduced tool wear under trace lubrication conditions,and TMC@10 tools were coated with Capowder under the condition of dual lubrication of body and micro lubrication,the cutting performance was significantly improved.By observing the wear morphology of the TMC@10 cermet tool before and after the cutting surface,the rake surface of the TMC@10 tool mainly had micro chipping,crater wear and bonding wear,and the flank surface mainly had bonding wear and diffusion wear.