基于剪切增稠抛光( STP) 的加工原理分析Si₃N₄陶瓷超精密加工的控制策略，考察所制备的含有立方氮化硼( CBN) 磨粒的剪切增稠抛光液的流变行为，分析工件抛光前后表面形貌变化及表层应力状态，研究其抛光特性． 结果表明: 抛光液具有可逆的剪切增稠与稀化效应，可达到 STP 加工工艺用抛光液的要求; 改变磨粒粒径，可以控制 Si₃N₄加工效率与表面质量，且材料去除量和表面粗糙度的理论值能够反映试验值的变化; STP 加工Si₃N₄为持续微切削的“柔性抛光”，初期为脆性剪切、粘着磨损去除，后期为塑性去除; 当磨粒粒径达到纳米级时，表层应力状态由初始残余拉应力变为压应力，说明 STP 不仅能高效去除原有表面损伤层而且新引入的损伤小; 随着抛光时间的延长，去除量先快速增大而后趋缓; 抛光 90 min 后，去除率由初期的 5. 00 ～2. 40 μm/h 降至 3. 24 ～2. 04 μm/h，表面粗糙度 Ｒ a 由108.9 ～111.1nm 降至22.0 ～10.7nm;抛光150min 后，Ra 可降至 9. 6 ～7. 2nm,实现了Si₃N₄陶瓷粗抛后的精密抛光．

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 R_a reduces from 108． 9 ～111． 1 nm to 22． 0 ～10． 7nm; and (7) after polishing for 150min，R_a can be reduced to 9． 6 ～7． 2nm，which indicates that STP process achieves the precision polishing of Si 3 N 4 ceramics．