Preparation Process And Performance Characterization Of ZrO₂-Al₂O₃ Ceramics On Stereolithography

With the rapid development of industrial production,people's demand for high performance machining tool material and technology is increasing.At present,high speed and high precision machining has become the development trend of cutting technology.However,excessive cutting force and excessive cutting heat hinder the improvement of cutting speed and reduce cutting performance.The requirements of high speed cutting are that the tool material can still maintain good mechanical properties,chemical stability and anti-bonding performance at high temperature.Ceramic material has stable mechanical properties at high temperature and can meet the requirement of high speed cutting.Among them,ZTA ceramics with high hardness,high wear resistance and other characteristics can be produced in the cutting of high temperature to maintain good chemical stability and it can be used as a ceramic tool.In this paper,the high-purity zirconia powder and high-purity aluminum oxide powder were used as the research objects.The body of zirconia toughened alumina ceramic?ZTA?was prepared by DLP molding technology that belongs to additive manufacturing,and the ZTA ceramic tool was obtained by pressureless sintering.The effects of ZrO₂ content,sintering temperature,sintering additives and the addition of sintering additives on the particle size,density,mechanical properties and microstructure of Al₂O₃ were studied,and the cutting performance and damage mechanism of the ZTA ceramic tool formed by DLP were compared.The research results show that:?1?By comparing the densification of ceramic samples formed by DLP with solid content of 70 wt%and 78 wt%,it was found that the increase of solid content was beneficial to reduce the defects of monolayer forming and to improve the relative density of sintered samples.But too high solid content will also lead to single-layer film defects,and there are more holes.The ceramic slurry with a content of 78 wt%was selected as the experimental premise.With the increase of ZrO₂ content?14 wt%-20 wt%?at the same sintering temperature,the hardness of ZTA ceramic sample decreased and the fracture toughness remained basically unchanged.The ceramic sample in the same proportion of sintering temperature above 1550?,the sample density of 98%,hardness and fracture toughness will be significantly improved were18.53±0.14GPa and 5.63±0.39MPa·m^1/2.Preferred to choose the best sintering temperature is1600?,the best proportion of Al₂O₃ and ZrO₂ is 84:16.?2?Based on the above conclusions,the impact of the density,particle size,distribution,mechanical properties and the microstructure of three kinds of sintering aids and sintering aids of CaO,Cr₂O₃ and MgO at 1600°C sintering temperature for ZTA ceramics with 16wt%ZrO₂were studied..All the three sintering aids promote growth of the average size of Al₂O₃.The addition of CaO causes the Al₂O₃ grains to grow abnormally and grow columnar.Cr₂O₃ and MgO can promote the uniform growth of Al₂O₃ grains,but the average grain size is larger than pure ZTA,resulting in mechanics performance is declining.When 0.5 wt%Cr₂O₃ is added,the mechanical properties of ZTA ceramics are greatly improved,and the hardness and fracture toughness are up to 17.74±0.18 GPa and 6.15±0.47 MPa·m^1/2.?3?ZTA ceramics with a ratio of 84:16 at 1600°C were subjected to subsequent hot isostatic pressing,and the hardness,fracture toughness and flexural strength of ZTA ceramics were greatly improved.The cutting experiment of gray cast iron was compared with SZ200,DLP-ZTA and YG8 tools and the result shows that ZTA ceramic tools have the cutting advantage formed by stereolithography at high speed cutting.Compared the density,mechanical properties and cutting performance with ZTA ceramic tools by pressureless sintering and hot isostatic pressing.Conduct the reliability analysis of DLP-formed ceramic tools,and the influence of cutting parameters on the cutting performance of DLP-ZTA ceramic tools and the service life of ceramic tools.After 10 minutes of continuous dry cutting,it is finally determined that the cutting performance of DLP-ZTA ceramic tool after pressureless+hot isostatic pressing is best when the cutting parameters are S=300 m/min,f=0.1 mm/rev,ap=0.1 mm.