| Waterjet nozzle is one of the important components of waterjet.Currently,WC cemented carbide is often used as the raw material of waterjet nozzle.However,the waterjet nozzles which are made of WC cemented carbides have the following two problems:?1?Most of WC cemented carbides contain a certain amount of Co binder phase.The price of Co is high,and the addition of Co affects the hardness and wear resistance of the material.?2?the grains of WC cemented carbide prepared by traditional sintering method is coarse,due to the heating speed is often slow and the holding time is long,which deteriorate the performance of the material.The existence of these two problems restricts the application of WC cemented carbide in the field of waterjet.In this work,the high-entropy alloy Al0.5Co Cr Cu Fe Ni prepared by mechanical alloying was used as binder phase,a new HPS vacuum hot pressing furnace was used to sinter quickly the composite powders,which will provide technological reference for the development of new WC cemented carbide for waterjets.The high-entropy alloy Al0.5Co Cr Cu Fe Ni was prepared by 32-hour ball milling,and different contents of high-entropy alloy powders were added to WC,and then the high-entropy alloy powders and the original WC powders were also mixed by 32-hour ball milling.HPS vacuum hot pressing was used to sinter WC-Al0.5Co Cr Cu Fe Ni powders and the effect of different high entropy alloy Al0.5Co Cr Cu Fe Fe Ni additions,different HPS vacuum hot pressing process parameters on microstructure and properties of the material were explored.The results show that after 32-hour of ball milling,the high-entropy alloy has a uniform composition.It is mainly composed of Fe-Ni,Cu-Ni,and Fe-Cr phase solid solutions.In the mixing process of WC-Al0.5Co Cr Cu Fe Ni composite powders by ball milling,the grains and powder particles were refined.When sintered at 1400?,the relative density of pure WC is low.After adding 0.5wt.%Al0.5Co Cr Cu Fe Ni,the relative density of the material increases rapidly and reaches 98.2%,the hardness also reaches the maximum value of 2483 HV30.Then,the increasing Al0.5Co Cr Cu Fe Ni amount will reduces the hardness of the material.So the optimal amount of Al0.5Co Cr Cu Fe Ni is 0.5wt.%.During sintering WC-0.5Al0.5Co Cr Cu Fe Ni at different temperatures,when the sintering temperature increases from 1300?to 1400?,the density of the material increases from 94.2%to 98.2%,but the average grain size of WC only increases from 235 nm to 259 nm,When the temperature reaches 1450?,the grains grow quickly,and the hardness decreases rapidly.Therefore,the optimal sintering temperature is 1400?.WC-0.5Al0.5Co Cr Cu Fe Ni was then sintered at 1400°C for different holding time.When the sintering time is extended from 5minutes to 10 minutes,the relative density increases from 95.4%to 98%,and the average grain size of WC increases from 206 nm to 223 nm.If the sintering time becomes longer,there is no obvious increase in density,but grains continue to grow.So the best sintering time is 10 minutes.By optimizing the addition amount of Al0.5Co Cr Cu Fe Ni and the sintering processing parameters,the best mechanical properties of WC obtained are as follows:hardness 2535 HV30,fracture toughness 7.1 MPa·m1/2 and bending strength 790 MPa.The friction and wear experiments under different loads were carried out for WC-0.5Al0.5Co Cr Cu Fe Ni prepared with best process parameters in air and water,and compared with WC-0.5Co.When the load in the air is 25 N and 50 N,the wear rate of the material is low.When the load reaches 75 N,the abrasive wear caused by the peeling of WC particles enhances the wear rate of the material rapidly,up to 1.12×10-5mm3?N·m?.In the water environment,due to the lubrication of water,the wear rate of the material at 75N is 1.47×10-7 mm3/?N·m?,which is much lower than that of dry grinding.On the other hand,under 75 N load,the wear rate of WC-0.5Al0.5Co Cr Cu Fe Ni is also lower than that of the comparative material WC-0.5Co with a value of 5.15×10-7 mm3/?N·m?. |
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