Journal of South China University of Technology (Natural Science Edition) ›› 2015, Vol. 43 ›› Issue (9): 113-120.doi: 10.3969/j.issn.1000-565X.2015.09.018

• Mechanical Engineering • Previous Articles     Next Articles

Experimental Investigation into Si3N4 Ceramics Machined via Shear-Thickening Polishing Method

Li Min1 Yuan Ju-long1,2 Lü Bing-hai2 Yao Wei-feng2 Dai Wei-tao2   

  1. 1． National Engineering Research Center for High Efficiency Grinding，Hunan University，Changsha 410082，Hunan，China;2． Key Laboratory of Special Purpose Equipment and Advanced Processing Technology of Ministry of Education，Zhejiang University of Technology，Hangzhou 310014，Zhejiang，China
  • Received:2014-12-08 Revised:2015-04-21 Online:2015-09-25 Published:2015-09-07
  • Contact: 吕冰海(1978-)，男，博士，研究员，主要从事精密与超精密加工技术及装备研究． E-mail: icewater7812@126.com
  • About author:李敏(1983-)，男，博士生，讲师，主要从事精密与超精密加工技术及装备研究． E-mail: li-min-wax@163.com
  • Supported by:
    Supported by the National Natural Science Foundation of China(51175166，51175468，50975085)，the Joint Research Fund for Overseas Chinese，Hong Kong and Macao Scholars(51228501)，the Natural Science Foundation of Zhejiang Province(LZ12E05001) and the Science and Technology Plan of Zhejiang Province(2013C31014)

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Abstract: In the investigation，the control strategy of ultra-precision machining of Si3N4 ceramics is analyzed on the
basis of the principle of shear thickening polishing (STP)，and the rheological behaviors of the prepared STP slurry with cubic boron nitride (CBN) abrasives are discussed． Then，the variations of the surface morphology and surface residual stress state of Si3N4 ceramics before and after the polishing are analyzed to reveal the polishing characteristics of STP． The results show that (1) the slurry displays a reversible shear thinning and shear thickening behavior，which meets the requirement of the slurry for processing STP; (2) the machining efficiency and surface quality of Si3N4 ceramics can be controlled by changing the grain size of CBN abrasives，and the theoretical values of the material removal and the surface roughness can reflect the change of experimental values; (3) the STP removal of Si3N4 is a continuous micro cutting process named "flexible polishing"，in which the brittle shear or the adhesive wear is employed in the initial stage of machining and the ductile removal of the microscopic plastic flow is used in the later stage; (4)when the grain size reaches nanoscale，the surface stress state of Si 3 N 4 will change from the initial residual tensile stress to the compressive stress，which means that the STP can efficiently remove the damage layer of the original surface and produce merely new small damage; (5) with the extension of the polishing time，the material removal amount of Si3N4 first increases quickly and then tend to increase slowly; (6) after polishing for 90 min，the material removal rate decreases from 5． 00 ～ 2． 40μm/h to 3． 24 ～ 2． 04μm/h and the surface roughness Ra reduces from 108． 9 ～111． 1 nm to 22． 0 ～10． 7nm; and (7) after polishing for 150min，Ra can be reduced to 9． 6 ～7． 2nm，which indicates that STP process achieves the precision polishing of Si 3 N 4 ceramics．

Key words: shear-thickening polishing, silicon nitride, rheological behavior, stress condition, material removal, precision polishing

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