Study On Sintering Process And Fabrication Mechanism Of The Green Body Of The Laminated Al₂O₃/WC Ceramic Cutting Tool Materials

In order to overcome the defect of low efficiency and control layer thickness in fabricating green body of laminated ceramic cutting tool materials, the atomized-sprayed coated liquid film-dried method was putted forward to fabricate the green body of the laminated Al₂O₃/WC ceramic cutting tool materials, and studied the fabrication mechanism of the green body of the laminated Al₂O₃/WC ceramic cutting tool materials. The new type of the laminated Al₂O₃/WC ceramic cutting tool materials was successfully fabricated by the hot-pressing sintering technology, and the related performance and microstructure were investigated.According to the design principles of ceramic cutting tool material, ceramic phases such as Al₂O₃ and WC, and the metal phase were selected. The wettability and chemical physical compatibility of the ceramic phases and the metal phase were analyzed. The green bodies of laminated Al₂O₃/WC ceramic cutting tool materials were fabricated by the atomized-sprayed coated liquid film-dried method. The influence of the ratio of nanopowder and anhydrous ethanol on atomization and drying time, the effect of drying temperature on the drying time, and the surface morphology at different drying temperatures were investigated. The higher quality and higher efficiency of fabricating the green body of laminated ceramic cutting tool materials can be obtained when the ratio was 1:25 and the drying temperature was 90.℃In order to improve the density of the sintered ceramic materials, the green bodies were sintered by vacuum hot press sintering technology. According to the sintering densification mechanism and the properties of the material, the sintering pressure, the range of sintering temperature and holding time were determined. The test methods of the mechanical properties of the materials were presented according to the relevant national standards, and the microstructure of the materials was analyzed. The relative density, flexural strength, Vickers hardness, fracture toughness, tribological properties and the microstructure of the laminated Al₂O₃/WC ceramic cutting tool materials were studied. The green bodies were sintered respectively at different sintering temperatures of 1600℃, 1650℃, 1700℃ and 1750℃, and at the same sintering pressure of 30 MPa and the same holding time of 20 min. The results showed that the relative density of the laminated Al₂O₃/WC ceramic tool materials was increased with the increase of sintering temperature. The maximum relative density was 97.22% when the sintering temperature was 1750℃, and the effect of the sintering temperature on the relative density of the materials was no significant. With the increase of sintering temperature, the flexure strength increased first and then decreased, and the flexure strength was best at 1650℃, which can reach 469.46 MPa. With the increase of sintering temperature, Vickers hardness increased. Vickers hardness was the best at 1750℃, which can reach 17.02 GPa. With the increase of sintering temperature, the fracture toughness increased. The optimal fracture toughness of 4.13MPa/m1/2 can be obtained at 1750℃. With the increase of sintering temperature, the friction coefficient of the materials increased first and then decreased. When the load was 60 N and the sintering temperature was 1600℃, the average value of friction coefficient was the smallest, which was 0.19. The effect of the sintering temperature on the wear rate had the same change rule as the effect of the sintering temperature on friction coefficient. When the load was 60 N and the sintering temperature was 1600℃, the average value of the wear was the smallest, which was 0.9×103mm3. By observing the layer morphology of the laminated Al₂O₃/WC ceramic tool materials, the better the densification can be obtained, the more the temperature increased.