Friction And Wear Behaviors Of Unbonded Phase ?W,mo?c-al₂o₃ Tool Material

With the wide application of cutting technology,the machining efficiency,cutting precision and tool material hardness are higher in the machining process.Conventional cemented carbide tool materials are prone to dissolution,diffusion,bond wear and oxidative wear in difficult-to-machine materials with high processing temperatures and active chemical properties.In this paper,the unbonded phase?W,Mo?C-Al₂O₃ cemented carbide tool material was prepared by spark plasma sintering.The effect of sintering process on the mechanical properties and microstructure of the tool material is investigated.Sintering process of tool material.wear properties of room temperature,and wear properties of high temperature is optimized.The wear mechanisms at room temperature and high temperature are analyzed,which provide a theoretical basis for improving the material properties of the tool and developing new tool materials.The main research contents and conclusions of this paper are as follows.?1?The physical and mechanical properties of the unbonded phase?W,Mo?C-Al₂O₃cemented carbide tool material were analyzed by three-point bending and hardness test.The phase composition fracture morphology and cross section were observed and analyzed by XRD,SEM and EDS.In the range of 1400¹800?,with the increase of sintering temperature,the density of tool materials firstly increases and then slows down.The Vickers hardness,flexural strength and fracture toughness change trend firstly and then decrease.When the holding time is 10 min,the better mechanical properties are obtained at lower sintering temperature?1600??.The Vickers hardness,flexural strength and fracture toughness are 6.72MPa·m ^1/2,728 MPa and 1817 HV₃₀,respectively.?2?The effects of load and sliding speed on the room temperature friction coefficient,wear rate and wear mechanism of the tool materials were studied when the?W,Mo?C-Al₂O₃tool materials were matched with SiC and Si₃N₄ ceramic balls.?W,Mo?C/SiC friction pair under the condition of dry friction at room temperature,when the load is constant,the friction coefficient increases first and then decreases with the increase of sliding speed;When the sliding speed is constant,the friction coefficient shows a significant downward trend and the wear rate shows a gradual decline,with the increase of the load;The wear mechanism is dominated by fatigue wear and abrasive wear.The room temperature friction coefficient of?W,Mo?C/Si₃N₄ friction pair increases with the increase of sliding speed and load.The friction coefficient of room temperature is not obvious when the load is low,and the wear rate is 10^-7orders of magnitude;The friction coefficient at room temperature is more obvious when the load is high,and the wear rate is 10^-66 orders of magnitude;The wear mechanism is dominated by abrasive wear,adhesive wear and diffusion wear.?3?The high temperature friction and wear experiments of unbonded phase?W,Mo?C-Al₂O₃ cemented carbide tool materials were studied.The effects of load,friction speed and ambient temperature on high temperature friction and wear properties were investigated,and the mechanism of high temperature friction and wear was explored.The results show that the high temperature friction coefficient and wear rate of?W,Mo?C-Al₂O₃composite tool materials generally decrease with the increase of friction speed and load;Under the working conditions of the same friction speed and load,the high-temperature wear rate of?W,Mo?C-Al₂O₃ and YG10X composite tool materials increases with the increase of the ambient temperature and the higher the ambient temperature,the more severe the tool wear.When the ambient temperature is 200?and 400?,the wear rate of?W,Mo?C-Al₂O₃tool material is not much different from YG10X.The?W,Mo?C/Si₃N₄ friction pair and the YG10X/Si₃N₄ friction pair are mainly furrows and detachment pits caused by the detachment of the hard surface WC particles on the friction surface.The abrasive wear is the main form of wear at this time.When the ambient temperature is as high as 600?,due to the oxidation of WC and the softening of binder Co,the wear rate of YG10X tool material is 7.5×10-6mm³/Nm much larger than the wear rate 4.2×10-6mm³/Nm of?W,Mo?C-Al₂O₃.The oxidized friction film formed on the surface of the?W,Mo?C/Si₃N₄ friction pair has a certain anti-wear and wear-resisting effect.And the friction surface has a large number of grains after the detachment of the peeling pit wear morphology,abrasive wear,spalling separation,oxidative wear is the main form of wear at this time.The surface of YG10X/Si₃N₄ friction pair also has obvious adhesion and furrow phenomenon.Abrasive wear,oxidative wear and adhesive wear are the main forms of wear.Therefore,the?W,Mo?C-Al₂O₃ composite tool material has better wear resistance than the YG10X composite tool material.