Research On Spark Plasma Sintering Process Of WC-Co Hard Alloy Cutter

Galvanized steel plate is a welded steel plate with hot dipped or galvanized coating on the surface.It is widely used in construction,household appliances,car,vessel,container manufacturing,mechanical and electrical industry because of its good corrosion resistance.When galvanized steel plates are welded by resistance spot welding,zinc coating can penetrate into the copper electrode cap,which worsens welding quality and is the reason of failure of copper electrode.In industry,milling cutters are often used to grind copper electrodes.It will cost too much time and energy when cutters are made in traditional way.So,in this study,spark plasma sintering will be applied to produce WC-Co hard alloy cutters,which can reduce costs and improve efficiency.Firstly,the effects of sintering parameters on microstructure and mechanical properties of the materials were investigated,which includes sintering temperature and holding time.It was found that the density and hardness increased with rising of the sintering temperature in the same preservation time,and the better sintering temperature was determined.At that temperature,it was studied that how the holding time influenced the microstructure and mechanical properties of hard alloy.The results showed that the relative density and hardness of the material increased first and then decreased,and the superior holding time is determined.The best sintering parameters were obtained.When samples were sintered at 1350? for 6min,its relative density was 99.3%,and the value of hardness was 2212 HV,which were the best comprehensive performance.Secondly,the effects of heat treatment on microstructure and mechanical properties of the composites were studied.The samples prepared by the best sintering process were quenched at different temperatures.It was found that with the increase of temperature,the density of the samples decreased gradually,while the hardness,compressive strength and compression rate were all rising first and then decreasing.And the superior quenching temperature was determined.The sample after quenching was tempered at different temperatures.The microstructure and mechanical properties of different samples were studied.With the increase of temperature,the value of hardness first rose and then dropped,while the compressive strength and compression rate decreased.And the better tempering temperature was obtained.The samples prepared by quenching at 1050? was tempered at 500? for 4h,and they would get the best quality.Their value of hardness was 1760 HV,compressive strength reached 4378 MPa and compression ratio was 11.17%.Finally,milling cutter was made by sintering process and heat treatment system determined.The shape of the cutter was preliminarily formed with that of the designed forming die.The size accuracy met the requirements,and 40.6 percent of material was saved comparing with being produced by cylinder directly.The hardness index was in agreement with the previous experimental results,which met the demand.