Development Of Zirconia Matrix Nano-micro Composite Ceramic Die Material And Its Friction And Wear Behaviors

From the requirement for die materials, nano-micro composite ceramic die materials with high mechanical properties were fabricated successfully with nano-micro composite method. The correlations among the material composition, the hot pressing process, the microstructures and mechanical properties were investigated. The strengthening and toughening mechanisms of the nano-micro composite ceramic die materials were studied systematically, also the friction and wear behaviors which were very important to die materials were studied experimentally.The effects of TiC, Y₂O₃, Al₂O₃, metallic element Mo+Ni and rare earth element CeO₂ on the microstructure and mechanical properties of nano-micro composite ceramic die materials were discussed. The hot press sintering parameters were optimized. ZrO₂ based nano-micro composite ceramic die material was fabricated successfully, its flexural strength, fracture toughness and Vickers hardness are 866 MPa, 8.4MPa·m^1/2 and 13.05GPa respectively. Compared with single phase ZrO₂ ceramic material, the flexural strength, fracture toughness and hardness were increased by 49.8%, 17.3% and 16.5% respectively. In the prepared ZrO₂ based nano-micro composite ceramic die materials, the addition of nano-scale TiC particles which are located between or within ZrO₂ matrix refines the grains and makes the inter/trans mixed granular fracture mode happen. Besides, ZrO₂ phase transformation toughening, crack deflection, crack bridging, crack branching and particle pull-out are all kinds of strengthening and toughening mechanisms, as a result, the comprehensive mechanical properties of ZrO₂ based nano-micro composite ceramic die materials have been greatly enhanced.The friction and wear mechanisms of nano-micro composite ceramic die materials were discussed by analyzing SEM micrographs and composition on typical specimens. It is indicated that in unlubricated conditions of normal load of 140N and rotational speed of 200r/min, the friction coefficient of ZrO₂ based nano-micro composite ceramic die materials is 0.65 and the wear rate is 2.88×10^-7mm³/N·m; while the friction coefficient of single phase ZrO₂ ceramic material is 0.73 and the wear rate is 5.32×10^-6mm³/N·m. The dominant wear mechanisms of single phase ZrO₂ ceramic material are brittle fracture and grain stripping. While the dominant wear mechanisms of ZrO₂ based nano-micro composite ceramic die materials are mechanical interlocking and adhesive wear.