Preparation Of (W,Mo)C/Al₂O₃/La₂O₃ Materials Without Bonding Phase And Its Microtexture Friction And Wear Properties

In order to improve the cutting performance of cemented carbide and improve the susceptibility of traditional cemented carbide phase to oxidation and corrosion,(W,Mo)C/Al₂O₃/La₂O₃cemented carbide materials were prepared by low-temperature combustion,carbon reduction and SPS sintering process.The effect of sintering temperature on mechanical properties and microstructure of materials was investigated and the sintering process was optimized.The effect of micro-texture parameters,load and rate on friction and wear properties of(W,Mo)C based materials was studied and wear mechanism was analyzed.The main research contents and conclusions of the article are as followings:(1)Precursor powder was prepared by low-temperature combustion using ammonium tungsten,ammonium molybdate,aluminum nitrate and lanthanum nitrate as raw materials.(W,Mo)C/Al₂O₃/La₂O₃composite powder was prepared by carbon reduction of precursor powder.(W,Mo)C/Al₂O₃/La₂O₃materials were fabricated by SPS process.The effect of the ratios of salt nitrate,urea and glucose on properties and morphology of powder was investigated and the optimal ratio was obtained to produce(W,Mo)C/Al₂O₃/La₂O₃powder.The materials were sintered at 1500?1800?.The influence of sintering temperature on microstructure and mechanical properties were studied and the mechanism of strengthening and toughening was analyzed.The results showed that the optimal molar ratio of nitrate and urea was 1:2,and the optimal molar ratio of nitrate and glucose was 1:0.5.After adding glucose,the particle size was reduced by 0.28?m,and the specific surface area was increased by 75.64%.The maximum density,Vickers hardness and flexural strength at 1600?reached 98.45%,2202HV₃₀and 1203MPa respectively,and fracture toughness at1500?reached 7.52MPa·m^1/2.The microstructure was even and the crystal size was about 1-2?m.(2)Using Si₃N₄ceramic balls as counter-abrasives,the effect of micro-texture parameters,load and rate on friction and wear properties of(W,Mo)C/Al₂O₃/La₂O₃materials was investigated.After optimizing the micro-texture parameters,the effect of load and sliding rate on friction coefficient and wear rate of(W,Mo)C/Al₂O₃/La₂O₃tool materials with different micro-texture shapes at room temperature was investigated,and the wear mechanism was explored.The role of micro-texture is mainly reflected to store abrasive debris,while delaying the wear of the substrate surface.The wear mechanism of(W,Mo)C based materials at room temperature is mainly abrasive wear,bond wear and diffusion wear.(3)High-temperature friction and wear properties of(W,Mo)C/Al₂O₃/La₂O₃tool materials with surface micro-texture were studied,and the mechanism of high-temperature friction and wear was explored.The results showed that high-temperature friction coefficient and wear rate of(W,Mo)C based materials generally decreased with the increase of friction rate.The oxidized friction film that was generated on the secondary surface had a certain effect of reducing wear and abrasion and the friction surface had a lot of peeling pit wear morphology after detachment of grains.Abrasive wear,fatigue wear,bonding wear and oxidative wear are the main forms of wear at this time.(W,Mo)C/Al₂O₃/La₂O₃materials without microtexture were mainly abrasive wear,oxidative wear and plastic deformation.The friction coefficient and wear rate of(W,Mo)C/Al₂O₃/La₂O₃without microtexture are higher than that of(W,Mo)C/Al₂O₃/La₂O₃with circular microtexture.The role of micro-texture at high temperature is due to reduce the shear stress caused by friction and store some abrasive debris,so as to reduce the wear rate.High-temperature friction and wear experiments were conducted at 200?-600?for(W,Mo)C/Al₂O₃/La₂O₃with circular microtexture and WC-10Co with circular microtexture.Compared with WC-10Co,it was found that friction coefficient and wear rate of(W,Mo)C based materials were lower than that of WC-10Co.It is related to the fact that the hardness of WC-10Co is lower than(W,Mo)C/Al₂O₃/La₂O₃and the surface oxidation of the matrix materials and bonding phase are existed.The precipitation and softening of Co phase reduce wear resistance of WC-10Co.