Preparation And Performance Analysis Of SPS For Highly Densified Ultrafine-grained Carbide Cutting Tools

In order to improve the comprehensive mechanical properties of cemented carbide,a kind of ultrafine grained cemented carbide with high hardness,high toughness and high bending strength is produced.By combining the advantages of spark plasma sintering process,WC Co cemented carbide was prepared by two-step sintering and gradient cemented carbide was successfully prepared.Finally,its microstructure,mechanical properties,high temperature properties and cutting properties were analyzed.The two-step sintering process was explored and the improvement of mechanical properties of cemented carbides by two-step sintering process is compared with that by onestep sintering process.The results show that the mechanical properties of cemented carbides are the best when the sintering process is that hold at 1300? for 3 minutes,then hold at 1200?for 5 minutes.Compared with the ultrafine cemented carbide prepared by one-step sintering,the average WC grain size of the two-step sintered ultrafine cemented carbide decrease from362 nm to 271 nm,the density increase from 98.6% to 99.5%,the hardness,toughness and bending strength is 1834 HV₃₀,12.246 MPa · M^{1 / 2} and 1819.5 MPa respectively.The preparation of gradient cemented carbide was studied.The experimental results show that the ultrasonic vibration method is better than the ball milling method in dissipating the agglomeration phenomenon,which makes the density of the samples increase from 13.24 g /cm³ to 14.08 g / cm³.Compared with homogeneous cemented carbide sintering,WC grains of gradient cemented carbide are easier to grow,but there is no abnormal growth of grains.The distribution of grain size is more concentrated,mostly between 200 and 300 nm.Compared with WC-4Co,the bending strength of gradient cemented carbide increased by 13.25% and hardness decreased by 8.44%.The high temperature properties and bending properties of cemented carbide was studied by muffle furnace and universal testing machine.It is found that the bending properties of cemented carbide decrease gradually with the increase of ambient temperature.When the temperature rises to 800?,the bending properties of cemented carbide decrease rapidly,and the bonding phase and the hard phase are oxidized to WO₃ and CoWO₄.Through the actual cutting experiments to compare the cutting performance of various materials.It is found that the carbide tool prepared by two-step method has better wear resistance than that prepared by one-step method,but it is more prone to the phenomenon of edge collapse.Gradient cemented carbide has more excellent wear resistance than homogeneous cemented carbide.The depth and length of crater wear are 30% and 21.15% less than homogeneous cemented carbide respectively.