Study on Crack Repair Performance of Si3N4/TiC/ZrSi2 Ceramic Tool Materials.

To solve the problems that ceramic tools were sensitive to cracks, ZrSi₂ crack repairing agent was added into Si₃N₄/TiC ceramic tool material matrix, which made ceramic tools have crack repairing ability. When ZrS_i2 content was as 10% (volumn fraction), Si₃N₄TiC/ZrSi₂ ceramic tool materials had better comprehensive properties, with flexural strength of 815 MPa, fracture toughness of 8.06 MPa ⋅ m^1/2, Vickers hardness of 15.91 GPa and relative density of 99.72%). Cracks were introduced into the surface of ceramic tool materials by Vickers hardness tester, and the optimal repair parameters and repair mechanism of cracks in Si3N,/TiC-based ceramic materials with ZrSi₂ as repair agent, were studied. The research shows that the flexural strength of Si₃N₄TiC/ZrSi₂ prefabricated crack specimen with 10%) ZrSi₂ added may be restored to 92.02%) of that of smooth specimen after heat treatment at 800 °C for 60 min in air atmosphere, and the crack with the surface length of 300 ~ 350 µm is completely repaired, and an oxide layer mainly composed of ZrO₂ and SiO₂ is formed on the surface of the specimen. The mechanism of crack repair of ceramic cutting tool materials is analyzed as follows-, in the air heat treatment processes, ZrSi₂, a healing agent at the crack and the surface of the material, preferentially reacts with oxygen to generate ZrO₂ and SiO₂, which heal the crack on the surface of the material and restore the strength of the crack sample. At the same time, during cutting, ZrO₂ and SiO₂, oxidation products of ZrSi₂ at the cracks and material surfaces, may repair the crack in time and improve the wear resistance of the tool. [ABSTRACT FROM AUTHOR]