Effects Of Post-treatment For Coarse-grained Wc-10co Alloy

With the rapid development of oil and gas exploitation,infrastructure construction,and mine exploitation,the demand of a new-generation coarse-grained and ultracoarse-grained cemented carbides for mining with high efficiency and long service time is expanding.In the modern mining industry,cemented carbide inserts for mining face severe working condition,such as high impact load,thermal shock and abrasive wear.Therefore,the cemented carbides for mining require excellent properties and abrasive performance to ensure their operation.In order to improve the microstructure and properties,Cryogenic treatment and aging treatment can be used as the post-treatment methods for coarse-grained cemented carbide.In this paper,coarse-grained WC-10Co cemented carbide samples with four different carbon contents were prepared.The effects of cryogenic treatment and aging treatment on the mechanical properties,saturation magnetization,cobalt phase structure,microstructure and impact abrasive wear rate of the specimen were investigated and the mechanism was also explored.The following conclusions can be drawn in compare to relevant research works at home and abroad:(1)For WC-6Co?WC-14Co coarse-grained cemented carbide,the corrosion rate of WC hard phase is closely related to the corrosion time,WC particles size and Co content.The WC particles on the surface of alloy can be completely dissolved,after 9 hours'electrolytic corrosion;(2)The impact abrasive resistance of the cemented carbide is closely linked to the carbon content of the cemented carbide and the post-treatment process.The impact abrasive wear rate of the sintered alloy decrease more than 60%by reducing the carbon content.The wear rate of sintered alloy can be further decreased at least 20%after aging treatment and cryogenic treatment;(3)After cryogenic treatment and aging treatment,the microstructure of cemented carbides stay the same,but tiny WxCoyCz particles,with diameter about 3-5nm,dispersed inside Co binder phase were found by HRTEM.The boundary between the nanoscaled precipitated particles and the Co matrix is perfect coherent.After tempering and cryogenic treatment,the number of nano WxCoyCz particles increased significantiy,the Vickers hardness(HV30)increased slightly,as a hitch-hiking effect of in-situ precipitation inside Co binder.(4)The highest impact abrasive wear resistance of the coarse-grained WC-10Co cemented carbide can be achived by low carbon content and aging-cryogenic treatment process,without the formation of ?-phase.The precipitation of nano WxCoyCz dispersion phase inside Co binder plays an important role in improving the impact abrasive wear resistance of coarse-grained cemented carbide.The reduction of cemented carbide contiguity plays an important role in avoiding internal stress concentration.After cryogenic treatment,the macro compressive stresses on the surface of alloys increase.It is beneficial to avoid the early failure of the alloy caused by the formation and expansion of the micro cracks on the surface of the alloy so as to improve the wear resistance of the coarse-grained WC-Co cemented carbide.