Study On Modification Of Regenerated Cemented Carbide By Impurities And Rare Earth Elements

Cemented carbide has a series of excellent mechanical properties such as high strength,high hardness and high wear resistance,and is widely used in mining,oil field exploration and mechanical processing.As the application field of cemented carbide becomes more and more extensive,the consumption increases year by year,which makes the main raw materials of tungsten and cobalt for preparing cemented carbide increasingly depleted.Therefore,it is also more and more important to prepare regenerated cemented carbide by recycling waste cemented carbide.However,during the preparation of regenerated cemented carbide,other impurity elements are inevitably introduced,among which Fe element is the most impurity element introduced in the recycling process of waste cemented carbide.The introduction of impurity elements will inevitably affect the microstructure and mechanical properties of regenerated cemented carbide.In addition,adding a trace amount of rare earth elements to the regenerated cemented carbide can effectively improve the mechanical properties of the cemented carbide.In this paper,the WC-Co regenerated cemented carbide with 10%binder phase content is prepared by low-pressure sintering of waste cemented carbide after zinc melting treatment.The effects of the impurity element Fe and the addition of rare earth oxides on the microstructure,mechanical properties and wear resistance of regenerated cemented carbides were studied.Studies have shown that as the Fe content of regenerated cemented carbides increases from 0.2%to 1.5%,the density of the alloy decreases from 14.45 g/cm3to14.32 g/cm3;The bending strength and hardness of the alloy decrease from 1456.5HV20 and 2200 MPa to 1318.1 HV20 and 1682 MPa;Under the same friction and wear test conditions,the amount of alloy wear also increased by 5.94%.Therefore,the introduction of impurity Fe element has obvious adverse effects on the mechanical properties and wear resistance of the alloy.To ensure the excellent performance of the alloy,the Fe content of the mixed powder needs to be controlled within 0.5%.In order to optimize the mechanical properties of the regenerated cemented carbide,avoid the introduction of impurity elements,the discontinuous growth of the grains,and the high porosity of the regenerated cemented carbide during the preparation process.In this paper,the modification of regenerated cemented carbide by adding rare earth oxides?Y₂O₃,Ce₂O₃ and Nd₂O₃?has been studied.It is found that the addition of rare earth can effectively inhibit the growth of WC grains and the formation of pores,thus avoiding the abnormal growth of WC grains.With the increase of rare earth oxide content,the densification,hardness and bending strength of recycled hard alloy show a trend of increasing first and then decreasing.Among them,the addition of0.5%Y2O3 has the best effect on improving the mechanical properties of regenerated cemented carbides.The compactness,hardness and strength have been increased by1.24%,9.43%,and 11.37%,respectively.When the content of rare earth is more than0.7%,the comprehensive properties of regenerated hard alloy begin to decline,which is closely related to the negative effects of rare earth enrichment and decrease of compactness when rare earth is doped too much.Studies have shown that the addition of 0.5%Y₂O₃ has the best effect on improving the wear resistance of regenerated cemented carbides,the amount of wear is reduced from 1.41mg to 0.67mg,and the friction coefficient decreased from 0.6342 to 0.5803.The addition of rare earth elements improves the wear resistance of regenerated cemented carbide mainly due to uniform refinement of WC grain size and improvement of interfacial bonding steength.This study clarified the effect of impurity Fe on the mechanical properties of regenerated cemented carbide,and improved the mechanical properties of recycled cemented carbide by adding rare earth elements.It advances the theoretical research progress of high-performance recycled cemented carbide,which has important research value for further improving the quality of regenerated cemented carbide and optimizing the preparation process.