Development Of Alumina Based Nanocomposite And The Application In Tool And Die

The alumina ceramic has excellent hardness, wear resistance, high-temperature wear resistance, corrosion resistance, low density and wide raw materials, but the low fracture toughness and low strength limit its wide application.Exploiting an effective approach to improve the mechanical properties of the alumina ceramic, especially its fracture toughness and flexural strength, will be significant for widening the actual application, as well as for the theoretical value.Nano-ZrO₂ and Ti(C,N) have been added in the study. Nanocomposite ceramic tool and die material of Al₂O₃/Ti(C,N)/ZrO₂ was fabricated successfully, its flexural strength, fracture toughness and Vickers hardness are 796 Mpa, 8.92 MPa-m^1/2 and 15.4 GPa respectively.The effects of constituent content and sintering technology on the microstructure and mechanical properties of nanocomposite ceramic tool and die materials were discussed. The flexural strength and fracture toughness are much higher than that of pure Al₂O₃ ceramic material. The nano-scale ZrO₂ and Ti(C,N) particles are located between or within Al₂O₃ matrix. Thus the typical mixture crystal microstructure is formed in the dense compacts, which resulted in the mixture granular fracture modes. The zigzag crack path, which is from the grain boundary into the grain and then turning to the boundary, can result in higher consumption of fracture energy and the increase of fracture toughness. Crack deflection, crack bridging, crack branching and grain pull-out reveals the improvement of the fracture toughness of the composites.The wear mechanism of nanocomposite ceramic tool and die materials were discussed by analyzing SEM micrographs of wear tracks on typical specimens. The friction coefficient and wear rate of Al₂O₃/Ti(C,N)/ZrO₂ nanocomposite ceramic tool and die materials are obviously lower than that of the monolithic Al₂O₃. The dominant wear mechanisms of pure Al₂O₃ may be brittle fracture and abrasive wear. While the dominant wear mechanisms of Al₂O₃/Ti(C,N)/ZrO₂ nanocomposite ceramic tool and die materials may be mechanical interlocking and abrasive wear. The wear pattern and mechanisms of Al₂O₃/Ti(C,N)/ZrO₂ nanocomposite ceramic tool and die materials were analyzed. The main wear mechanisms are abrasive and adhesion.