| Graphene is selected as the reinforcement phase to fabricate the graphene toughened alumina and alumina/titanium carbonitride(GA and GATCN)based nanocomposites ceramic cutting tool material,which is based on the consideration that the modern ceramic cutting tool materials,especially the alumina based cutting tool materials,have good hardness and poor toughness and the running condition of cutting used ceramic cutting tools.It is investigated that the graphene related powder distribution characteristics,the influence of graphene content on the mechanical properties of graphene toughened alumina and alumina/titanium carbonitride based nanocomposites ceramic cutting materials and the cutting performance of GATCN cutting tool material.The dispersants of graphene,alumina and titanium carbonitride are selected by the measurement of precipitation volume,and the certain additive content of alumina and titanium carbonitride are determined.Uv-vis spectrophotometry is used to determine the certain addition of graphene on the basis of precipitation volume measurement.The compared dispersion effort is verified by transmission electron microscope.The results show that the dispersed efforts are obvious.Polyethylene glycol(PEG)is used as the dispersant of alumina and titanium carbonitride.The dispersant additions of alumina and titanium carbonitride are 2% and 1% mass of the dispersed powder,respectively.Polyvinylpyrrolidone,60% mass of graphene,is the optimized dispersant content.Vacuum hot-pressing sintering technology is used to fabricate the GA,alumina/ titanium carbonitride ceramic material(ATCN)and GATCN ceramic material.According to the influence of titanium carbonitride content on mechanical properties of ATCN,the addition of alumina titanium carbonitride content is optimized.Incorporating the two dimensional feature and hot-pressuring technology,the measurement of mechanical properties of GA and GATCN bulk materials are performed on two directions including vertical to hot-pressuring direction(VHPD)and parallel to hot-pressuring direction(PHPD).The results show that the comprehensive mechanical property of ATCN is obtained,while titanium carbonitride content is volume fraction of 15%.The hardness fracture toughness and flexural strength is 19GPa、5.6MPa·m1/2 and561 MPa,respectively.The reinforcement effort of graphene is obvious from the results of the mechanical properties,and the anisotropy of fracture toughness and flexural strength from VHPD and PHPD are prominent,the values measured from VHPD are higher than that of values from PHPD.For GA,the hardness fracture toughness and flexural strength is 16.8GPa 、 6.2MPa·m1/2and 461 MPa,respectively,while the addition of graphene is 15vol%,of which both the fracture toughness and flexural strength is improved 59% by the addition of graphene.For GATCN,the hardness,fracture toughness and flexural strength is 19.2GPa 、7.1MPa·m1/2and 663 MPa,respectively,while the addition of graphene is 0.75vol%,of which the fracture toughness and flexural strength is improved 31% and 15% respectively by the addition of graphene.The fracture toughness and flexural strength of GA measured from VHPD are improved 38% and 39% higher than the values from PHPD.The flexural strength of GATCN measured from VHPD is improved 15% higher than the value from PHPD.Scanning electron microscope(SEM)is carried out to obvious the morphology of the fracture and polished surface.Based on the calculation of energy release ratio,the different crack length of from VHPD and PHPD is interpreted for GA material.The results show that the paralleled orientation of graphene layers is obvious,which also vertical to hot-pressuring direction(HPD).From SEM observation,graphene is pulled out in the cracks propagation.GATCN of 0.75vol% graphene addition,optimized results,is sintered as the ceramic cutting tool to 45 cutting experiment.The influence of cutting speed,back cutting depth and feed rate on the tool life and surface roughness are investigated.The controlled trail between GATCN and ATCN with the optimized cutting process is performed,and the cutting force and cutting temperature is measured simultaneously.The results show that the optimized cutting process is obtained,when the cutting speed,back cutting depth and feed rate are 160m/min,0.1mm and 0.102mm/r respectively.GATCN has maximum cutting distance of 6500 m,machined surface roughness of 1.2μm.The major wears forming are adhesive wear,abrasive wear,slightly notch wear.The orientated graphene has antifriction effects during the cutting process. |
