Research On Preparation Of Regenerated Coarse Grained Cemented Carbide And Wear And Corrosion Resistance

With the continuous expansion of cemented carbide applications,the consumption of cemented carbide materials is increasing year by year,which leads to the depletion of raw materials for cemented carbide production.Therefore,it is particularly important to make full use of recycled cemented carbide materials to prepare regenerated cemented carbide.Besides,with the rapid development of modern industry and the continuous emergence of difficult-to-process materials,the performance requirements for cemented carbide are increasing.The coarse grained cemented carbide has the advantages of high strength,high toughness,high red hardness,high wear resistance,corrosion resistance,et al,which can meet the increasingly stringent high performance requirements,so it has been widely concerned.Therefore,this thesis will use recycled cemented carbide materials to prepare regenerated coarse grained cemented carbide.But it is difficult to prepare regenerated coarse grained cemented carbides that meet the performance requirements with the traditional wed grinding process.Because the ball milling time is too long,the WC grain size decreases and the WC grains are unevenly distributed,the ball milling time is too short to cause the Co phase distribution,and all of them are easy to form Co pools,which seriously affect the performance of cemented carbide after sintering.Hence,it is necessary to improve the conventional preparation process and find a new process for preparing regenerated coarse grained cemented carbide.The mechanism of WC grain growth is that the dissolution of small WC particles promotes the growth of large WC particles in the process of liquid phase sintering.According to the growth mechanism of WC grains,it is a feasible method to prepare regenerated coarse grained cemented carbides by adding a certain amount of fine WC grains into the recycled coarse WC grains and using conventional technology.Therefore,based on the WC grain growth mechanism,this thesis described the preparation of regenerated coarse grained cemented carbides with recycled coarse WC particles,fine WC particles and Co powder as raw materials,and systematically studied the influence of fine WC particles on the microstructure and properties of the regenerated coarse grained cemented carbides.Choosing three different particle sizes of fine WC particles prepared the regenerated coarse-grained cemented carbide.The research found that the regenerated coarse grained cemented carbides with uniform grain size distribution,the largest average grain size and the best comprehensive mechanical properties can be prepared when the particle size of the fine WC particles is 0.2μm.The average grain size,relative density,transverse rupture strength,fracture toughness,and Vickers hardness of the prepared regenerated coarse grained cemented carbide can reach 4.06μm,99.84%,2520MPa,20.28MPa·m^1/2,1190HV,respectively.With the increase of 0.2μm fine WC particles in the material,the WC grain size,relative density,fracture toughness and transverse rupture strength all increase first and then decrease.When the content of fine WC is 10%,the WC grain size,fracture toughness,and transverse rupture strength of the regenerated coarse grained cemented carbide are the highest,which are increased by 72%,25.3%,and 11.4%,respectively compared with the alloy without fine WC particles.Finally,the effect of fine WC particle content on the wear resistance and corrosion resistance of regenerated coarse grained cemented carbide is studied.The results show when the fine WC particle content is 15%,the friction coefficient and wear rate of regenerated coarse grained cemented carbide are the lowest,the width and depth of wear marks are the smallest,and the wear resistance of alloy is the best.Through observing and analyzing wear morphology,the wear mechanism of the regenerated coarse grained cemented carbide is mainly abrasive wear,oxidative wear and adhesive wear.Through electrochemical corrosion experiments,the corrosion resistance of alloy increases with the increase of the WC grain size in the HCl solution.When the content of fine WC particles is 10%,the corrosion resistance of alloy is the best.However,the opposite result is shown in Na OH solution.As the WC grain size increases,the corrosion resistance of alloy becomes worse,but the resistance value of alloy in Na OH solution is larger than that in HCl solution,and the self-corrosion current density is lower,which indicating the corrosion rate of alloy in Na OH solution is slower.In this study,by adding fine WC particles to the recycled coarse WC powder,a regenerated coarse grain cemented carbide with superior comprehensive performance can be prepared,which solves the shortage of W,Co resources,provides a theoretical basis for the preparation of regenerated coarse grain cemented carbide and has important research value for improving the service life of recycled cemented carbide and expanding its application range.