Preliminary Study On Fabrication And Mechanical Properties Of Low Expansion Quasi Ceramic Cutting Tool Material

According to thermal expansion properties of ceramic tool materials and the requirements of the modern science for mechanical materials, the composition contents and fabrication technologies of the low expansion quasi ceramic cutting tool materials were designed and optimized. And three kinds of low expansion quasi ceramic cutting tool materials were fabricated. Thermal expansion coefficient was simulated by the computer finite element method.The system of the low expansion quasi ceramic cutting tool materials were designed, and the Al2O3 phase was set as the matrix phase, and the cordierite and Ti(C,N) phases were set as the adding phase, and the fabrication technologies and sintering technologies of cutting tool materials were worked out.The contents of cordierite in the low expansion quasi ceramic cutting tool materials Al2O3-cordierite (A-MAS) were optimized. The research results showed that the A-MAS70 material had relatively high mechanical properties, fine microstructures and low thermal expansion coefficient. It’s flexural strength was 563.0±92.6MPa, the Vickers hardness was 11.34±0.61GPa, the fracture toughness was 4.11 ±0.23MPa·m1/2, and the average thermal expansion coefficient was 2.80×10(?)m/℃ (RT～900℃). The contents of Ti(C,N) of the low expansion quasi ceramic cutting tool materials Al2O3-cordierite-Ti(C,N)(AT-MAS) were optimized. The results indicated that AT-MAS60 material had good mechanical properties, microstructure and thermal expansion coefficient. The flexural strength was 598.03±64.11 MPa, the Vickers hardness was 14.61±0.80GPa, the fracture toughness was 4.93±0.52MPa·m1/2, and the thermal expansion coefficient was 3.42×10-6 m/℃(RT～900℃).The sintering technologies of the low expansion quasi ceramic cutting tool materials, such as the MAS, A-MAS and the AT-MAS, were optimized. The results indicated that the MAS material had the best mechanical properties when sintered at a temperature of 1300℃ and a holding time of 40min as well as a heating rate of 30℃ /min, the flexural strength was 495.98MPa, the Vickers hardness was 9.08 GPa, the fracture toughness was 3.53MPa-m1/2, and when the MAS material was sintered at a heating rate of 50℃/min, it got the lowest average thermal expansion coefficient of 1.55×10-6 m/℃(RT～900℃). The low expansion quasi ceramic cutting tool materials A-MAS70 had the best mechanical properties when sintered at a temperature of 1300 ℃ and a holding time of 60 min as well as a heating rate of 30℃/min, the flexural strength was 319.5±39.6MPa, the Vickers hardness was 13.97±2.92GPa, the fracture toughness was 4.09±0.73MPa-m1/2. And the low expansion quasi ceramic cutting tool materials A-MAS70 material got the lowest average thermal expansion coefficient of 2.80×10-6m/℃(RT～900℃) when sintered at a temperature of 1250℃ and a holding time of 40 min as well as a heating rate of 30℃/min. The low expansion quasi ceramic cutting tool materials AT-MAS60 had the best mechanical properties when sintered at a temperature of 1400℃ and a holding time of 30min as well as a heating rate of 50℃/min, the flexural strength was 598.03±64.11MPa, the Vickers hardness was 14.61℃0.80GPa, the fracture toughness was 4.93℃ 0.52MPam1/2. The low expansion quasi ceramic cutting tool materials AT-MAS80 got the lowest average thermal expansion coefficient of 3.01×10-6m/℃(RT～900℃) when sintered at a temperature of 1450℃ and a holding time of 15min as well as a heating rate of 50℃/min.Using the monte carlo algorithm, the ceramic material microstructure model of three-dimensional was established and applied to simulate and compute the thermal expansion coefficient. The effect trend of temperature on the simulation results of the thermal expansion coefficient is nearly in agreement with the actual measured results.