Study On Roll-forming Technology And Performance Of ZrO₂ Ceramic Microbeads

Zirconia ceramics are widely used in the field of grinding due to their excellent mechanical properties and wear resistance.Grinding media balls made of zirconia ceramics have gradually replaced alumina ceramic balls due to their large specific gravity,low wear and no pollution,become the only product available in efficient grinding machinery.As a structural ceramic,zirconia ceramic balls have properties determined by their microstructure to some extent,and the quality of ceramic microstructure depends on the preparation process.In terms of molding,the roll-forming method overcomes the limitation of the mold required by the isostatic pressing method,and can easily and efficiently produce small-sized ceramic balls.However,the roll-forming method requires high powder performance,and requires not only the raw material powder is good,the powder also requires a certain degree of granularity and good fluidity.The zirconia ceramic grinding medium is prepared by using 3 mol% of yttria partially stabilized zirconia powder,and zirconia powder belongs to an desert sex powder.Therefore,the selection of 3YSZ powder which is easy to form and has good sintering activity is the key to roll-forming zirconia ceramic microbeads.At present,the preparation methods of 3YSZ powder mainly include solid phase,liquid phase and gas phase.The powder produced by the liquid phase method has a small original crystal size and more agglomerates,and it is difficult to roll into a ball during the roll-forming process.Solid phase method for preparing powder from solid raw materials is the mainstream method in the preparation of zirconia powder.The poor quality solid phase powder is not uniformly mixed and the sintering activity is not good.The electric explosion method belongs to a plasma gas phase method.The ultra-high temperature excitation gas reaction is generated by the plasma,and the powder particles are prepared by quenching using a large temperature gradient,and have good sintering properties.In this experiment,two YSZ powders produced by the solid phase method and the electric explosion method were used to produce sub-millimeter zirconia ceramic microspheres by controlling the molding parameters.The phase structure,micro-morphology and performance are characterized,and combined with the surface wear theory,the influencing factors of the wear resistance of ceramic microbeads are discussed.In the experiment,the two powders,with a ratio of powder to binder of 5: 1 and a rotating speed of the rolling pan of 40r/min,were rolled under pressure while using a reasonable pre-polishing and drying system.A spherical ball with a good roundness and a certain strength and a size of 0.4 to 0.6 mm can be obtained.The spherical ball sintered at high temperature wad obtained a ceramic bead with a diameter of 0.3 to 0.5 mm.The ceramic microspheres made of solid powder have the best wear resistance at a firing temperature of 1500?,and the self-wear rate is 3.142 ppm/h.The ceramic microspheres made of explosive powder have a uniform grain size and a dense structure.The ceramic beads made of solid phase powder and explosive powder have the best wear resistance at a firing temperature of 1500°C,and the self-wear rates are 3.142 ppm/h and 2.959 ppm/h respectively;both microbeads can be densified at the firing temperature of 1500? and the relative density is above 97%.The essence of microbeads wear is the shedding of surface grains.The uniform and dense microstructure can reduce the chance of grain shedding.When the polishing system is reasonable,the bead can obtain a smooth surface,which can further improve the wear resistance of the beads.