Microwave Two-step Sintering Of Fine-grained Alumina-based Ceramic Tools And Their Cutting Performance

Based on the unique sintering advantages of microwave sintering,the submicrocrystal Al₂O₃ composite ceramic cutting tools were prepared in this paper.The material system of the Al₂O₃ composite ceramic cutting tools was designed,and the sintering aids?MgO?Y₂O₃??the degumming parameters and the content of enhanced phase SiC were optimized;Through the research of microwave sintering Al₂O₃ grain growth kinetics and densification mechanism to ascertain the two-step sintering process,the fine crustal Al₂O₃/SiC composite ceramic cutting tools of excellent performance were successfully prepared by the microwave two-step sintering;Through the cutting experiments to study the cutting performance and wear mechanism of the tools,which developed by this paper and contrasted with the SW500ceramic cutting tools and YG8 cemented carbide cutting tools.The sintering aids and degumming process of Al₂O₃ composite ceramic cutting tools were optimized.The optimum sintering aids content was 0.7wt.%,the optimum degumming process was 350?/30min,the density?fracture toughness and Vickers hardness were 99.1%?4.9 MPa·m^1/2 and 17.0Gpa of the ceramic material after the degumming process,compared to the non-degumming,the sintering performance of the biscuit was more stable,its fracture toughness increased by 6.5%,and the grain of sintered body combined more closely and the interfacial bonding strength was improved obviously.The grain growth kinetics and densification mechanism of the Al₂O₃ composite ceramic cutting tools were studied in this paper.When the sintering temperature was below 1100?,the main densification mechanism of the Al₂O₃ composite ceramic was grain boundary diffusion,when the sintering temperature was in the range of 1200¹300?,the main densification mechanism of the Al₂O₃ composite ceramic was volume diffusion,when the holding time was 10min,the minimum grain growth activation energy was 48.32 KJ/mol,it indicated that the grain growth rate begin to accelerate dramatically when the holding time reached 10min,the average growth activation energy was 52.36 KJ/mol in the process of microwave sintering Al₂O₃ ceramics,it was far less than the traditional sintering;The microwave two-step sintering process?T₁=1300??T₂=1100??t=5min?was confirmed based on the study of the sintering kinetics of Al₂O₃ based ceramics,the density and the grain size of the sintering ceramics was 98.23%and 0.64±0.16?m,compared to the microwave single step sintering?2.1±0.49?m?and traditional two-step sintering?0.94±0.15?m?,the grain size decreased by 69.52%and 31.91%.The particle size and content of SiC and sintering process was optimized in this paper.When the particle size and content of SiC was 100nm and 3wt.%,the macroscopic mechanical properties were great,the microstructure was meticulous and uniform of the sintering ceramic,through the microwave two-step sintering?1600?/5min/1100?/5min?,the density?grain size?Vickers hardness and fracture toughness was 98.37%?0.96±0.23?m?18.40±0.24GPaand4.97±0.30 MPa·m^1/2,compared to the microwave single-step sintering,the grain size reduced by 46.96%,and the Vickers hardness and fracture toughness improved 2.79%and 12.70%.The cutting performance of the Al₂O₃/SiC ceramic tools cut hardened 40Cr alloy steel by continuous dry cutting method were studied in this paper.The results showed that the tool life was three times than the SW500 ceramic tool,and the surface roughness was 1.330?m when V=90m/min,f=0.1mm/r,a_p=0.1mm,and when V=270m/min,f=0.1mm/r,a_p=0.4mm,the maximum metal removal was 97161.92mm³,the surface roughness Ra of the workpiece was2.666?m.The cutting experiments show that the cutting performance of microwave two-step sintering Al₂O₃/SiC composite ceramic tool,which is better than that of the SW500 ceramic tool sold in the market.In the cutting process,the Al₂O₃/SiC composite ceramic tool did not appear the phenomenon of edge collapse.The failure type was wear failure.The main wear forms were crescent depression wear on the front face and groove wear on the back face.The mainly wear mechanism was abrasive wear and bond wear.