Preparation And Cutting Performance Of Al₂O₃/La₂O₃/WC Binderless Cemented Carbide Tool Material

Titanium alloy is widely used in aerospace,automotive and biomedical fields due to its high specific strength,good corrosion resistance and high temperature resistance.However,titanium alloy is a kind of difficult-to-machine material.The problems of high cutting temperature,high cutting force per unit area,severe tool adhesion,and poor surface quality during cutting process restrict the development of titanium alloy.In actual production,cemented carbide tools are often used to process titanium alloys.Traditional WC-based cemented carbides are also the most widely used tools today,but binder phase Co is chemically active,easily corroded and oxidized,and not resistant to high temperatures.This article will prepare a new type of Al₂O₃/La₂O₃/WC binderless cemented carbide tool material,study its sintering performance,friction and wear performance and dry cutting performance on titanium alloys,and compare with YG8 tool.The main research contents are as follows:Al₂O₃/La₂O₃/WC precursor composite powder was prepared by low-temperature self-ignition method according to five groups of different combustion improver addition ratios.The results show that when the molar ratio of fuel urea and glucose was 15:1,the precursor particles were fine and dispersed evenly.The precursor powder with a molar ratio of 15:1was used to reduced and carbonized to prepare Al₂O₃/La₂O₃/WC composite powder.Binderless phase Al₂O₃/La₂O₃/WC composites were prepared by plasma sintering at different sintering temperatures to study the effect of sintering temperature on material properties.The results show that as the sintering temperature increases,the grains of WC matrix tend to grow;the density of Al₂O₃/La₂O₃/WC composites continues to increase;hardness,the flexural strength,and rupture toughness are all first increased and then reduced.When the sintering temperature is 1600?,binderless phase Al₂O₃/La₂O₃/WC composite density reached98.8%;The grain size in the microstructure is fine,and Al₂O₃is evenly distributed with good mechanical properties.The bending strength is 792.0 MPa,hv hardness is 1771.3HV₃₀,and rupture toughness is 5.37MPa·m^1/2.Through the wear experiment of the new Al₂O₃/La₂O₃/WC binderless cemented carbide material,YG8 material and titanium alloy on the abrasive parts,the friction performance and wear mechanism of Al₂O₃/La₂O₃/WC binderless cemented carbide material were analyzed.The results show that compared with YG8,the friction coefficient of Al₂O₃/La₂O₃/WC samples is relatively stable.Under the same conditions,the friction coefficient and wear rate of Al₂O₃/La₂O₃/WC samples are always lower than YG8,the wear mechanism of sample is mainly bond wear;YG8 wear mechanism is bond wear,precipitation of Co bonding phase,and WC grain loss.The prepared Al₂O₃/La₂O₃/WC binderless carbide tool and YG8 tool were used for dry cutting comparative experiment on titanium alloy TC4,and the dry cutting performance of Al₂O₃/La₂O₃/WC binderless cemented carbide tool on TC4 was studied.The results show that with fixed feed and back cutting depth,three direction cutting force and surface roughness of Al₂O₃/La₂O₃/WC binderless carbide tool increases first and then decreases with increasing speed;The cutting force of YG8 tool decreases,while surface roughness decrease first and then increase with increasing speed;The cutting force and surface roughness of both tools increase with the increase of feed rate and back cutting depth.Under the same cutting conditions,the cutting force and surface roughness of binderless cemented carbide tool are significantly smaller than those of YG8 tool.Al₂O₃/La₂O₃/WC binderless cemented carbide tool has better wear resistance and comprehensive cutting performance than YG8 tool.