Microwave Sintered Al₂O₃/SiC Three-dimensional Geometry Ceramic Tool And Its Cutting Performance

In this paper,based on the characteristics of microwave sintering with rapid densification and no external pressure during the sintering process,a fine-grained Al₂O₃/SiC_p/SiC_w three-dimensional grooved ceramic tool was prepared.In this paper,the molding process of the ceramic tool green body was optimized;the effect of the content of SiC particles and whiskers on the mechanical properties and microstructure of Al₂O₃/SiC_p/SiC_w ceramic tools was studied;according to the distribution law of microwave electromagnetic field and temperature field in the sintered sample,the sample loading method was optimized.Finally,the cutting performance of the prepared fine-grained Al₂O₃/SiC_p/SiC_w three-dimensional grooved ceramic tool was tested and the failure mechanism of the tool was analyzed.The molding process of the green body of the Al₂O₃-based ceramic tool was optimized.The optimal content of binder polyvinyl alcohol PVA and the most suitable molding pressure were determined,which were 1.5wt.%and 150MPa,respectively.At this time,the relative density and hardness of the composite ceramic tool material by microwave sintering（1600℃/5min）were the highest,respectively,99.6±0.2%and 17.5±0.2GPa,and the fracture toughness was 3.1MPa·m^1/2.Compared with the same type of microwave sintering research,the content of PVA was reduced by 50%,which avoided the large amount of volatilization of PVA that would cause the insulation device to absorb microwaves and melt by heat.The effects of the content of SiC particles and whiskers on the mechanical properties and microstructure of Al₂O₃-based composite ceramic tool materials prepared by two-step microwave sintering（TSMS,1650℃/5min,1100℃/5min）were studied.The optimal content of SiC particles and whiskers was determined,which were 3wt.%and 1wt.%,respectively.At this time,the comprehensive mechanical properties of composite ceramic tool materials were the best with the relative density,hardness and fracture toughness of 99.8±0.1%,18.8±0.3GPa and 4.8±0.3MPa·m^1/2,respectively.Compared with single-step microwave sintering（SSMS,1650℃/5min）,the grain size was reduced by 35%,and the relative density,hardness and fracture toughness were increased by 0.8%,9.3%and 29.7%,respectively.The influence of sample loading method on the distribution of electric field and temperature field of microwave sintered Al₂O₃/SiC_p/SiC_w ceramic cutting tool,as well as its mechanical properties and microstructure were studied.When the height of the sample in the sintering cavity was H=200mm,the electric field had the largest field strength and the best uniformity,and the mechanical properties and microstructure of the sample after sintering were good.When the two samples were placed horizontally,the difference between the electric field and the temperature field of the two were the smallest,which were 320.1V/m and 12.8℃,respectively.Their mechanical properties were close,and the microstructure were fine and uniform.When three samples were placed in parallel,the temperature difference among the samples was relatively minimal.The cutting performance,failure mode and failure mechanism of three-dimensional grooved and flat-faced Al₂O₃/SiC_p/SiC_w ceramic tools for high-speed rough machining of martensitic stainless steel 1Cr13 were studied.The best cutting parameters of three-dimensional grooved ceramic tools were v=200m/min,a_p=0.2mm,f=0.1mm/r.Compared with traditional flat-faced ceramic tools,the metal removal rate has increased by nearly 2times,and the surface roughness of the machined surface was reduced by 32.5%.The failure modes of Al₂O₃/SiC_p/SiC_w three-dimensional grooved ceramic tools included adhesion wear,groove wear,abrasive wear,crater wear and brittle damage,but adhesion wear was the main cause of tool failure.