Effect Of Mo And Cu On The Microstructure And Properties Of WC-8Co Cemented Carbide

The development of cemented carbide needs to consume a lot of Co resources.However,our country is a country with a serious shortage of Co resources,and a large amount of Co raw materials need to be imported every year to maintain the development of my country’s Co products and Co-related fields.At the same time,as a strategic resource,Co is expensive and prone to large fluctuations,which increases the risk of the development of my country’s Co industry.Therefore,if it can reduce the use of Co in cemented carbide,which is of great significance to my country’s alleviation of dependence on Co resources and the development of the Co industry.In view of this,this article uses other elements to partially replace Co as the binder phase without reducing the overall performance of the cemented carbide.There are three reasons for choosing Cu instead of Co.First,Cu is the closest co-period element to Co in the periodic table,and its density is similar to Co;secondly,Cu can lower the liquid phase sintering temperature and inhibit the growth of crystal grains;finally,Cu has huge reserves and is cheap.However,due to the poor wettability between Cu and WC,and the direct addition of Cu will reduce the wear resistance and corrosion resistance of the cemented carbide.Therefore,before substituting part of Cu for Co,we first use the excellent properties of Mo to improve the properties of the cemented carbide,and then partially replace Co with Cu on the basis of optimizing the content of Mo,and find a more appropriate amount of Cu addition.Cemented carbide is prepared by low-pressure sintering,the microstructure,mechanical properties,wear resistance and corrosion resistance were analyzed.The result shows that Mo can improve the wettability between WC and the binder phase,reduce the precipitation of WC in the liquid phase,and weaken the dissolution-precipitation growth opportunity of WC grains.Thus it improves the compactness of the cemented carbide and refines the WC grain size.The density of the cemented carbide increases from 98.83% without Mo to 99.64% with the Mo content of 1.5 wt.%,and the average WC grain size decreases from 0.68 μm to 0.56 μm.In addition,the reduction of grain size increases the hardness from 1713 to 1898.When the Mo content is 1.5 wt.%,the transverse rupture strength of the cemented carbide is the maximum value of 2637 MPa,and the corrosion potential under acidic conditions and wear rate are reduced by 93.76 % and 70.61 % compared with the WC-8Co cemented carbide without Mo,respectively.After adding Cu to the WC-8Co-1.5Mo cemented carbide,the density of the cemented carbide decreases,which may be due to the poor wetting of Cu.In addition,Cu can reduce the liquid-phase sintering temperature and inhibit the growth of WC grains.When the amount of Cu is small,it can refine the WC grains slightly and improve the hardness and transverse rupture strength of cemented carbide.When the Cu content is 1.2 wt.%,the density,average size of WC,hardness and transverse rupture strength of WC-6.8Co-1.2Cu-1.5Mo cemented carbide are 99.31%,0.53 μm,1908 and 2617 MPa,respectively,which has a certain degree of improvement compared with WC-8Co cemented carbide.Although the addition of Cu will reduce the wear resistance and corrosion resistance of the cemented carbide,the corrosion current under acidic conditions and wear rate of the WC-6.8Co-1.2Cu-1.5Mo cemented carbide are reduced by 90.99 % and 14.69 % compared with WC-Co cemented carbide.It can be seen that it is feasible to use Cu to replace part of Co as the binder phase.