Sialon-Si3N4系梯度纳米复合陶瓷刀具材料的设计及制备

Design and Fabrication of Sialon-Si_3N_4 Gradient Nano-Composite Ceramic Tool Materials

根据对切削过程中陶瓷刀具温度及应力分布规律的研究,提出对陶瓷刀具材料的组成分布和微观结构进行设计以形成梯度的模型。通过调节TiC0.7N0.3含量,使材料在制备的冷却过程中在材料表层形成残余压应力。纳米Si3N4颗粒的加入可提高材料的微观性能;而合理的梯度结构设计提高了材料的宏观性能。采用粉末铺填热压烧结工艺制备出sialon–Si3N4系梯度纳米复合陶瓷刀具材料。结果表明:所制备的材料表层形成了残余压应力,有利于切削性能的提高;不同粒径的Si3N4晶粒形成双峰结构,有利于材料强度和韧性的提高;设计梯度陶瓷刀具材料时,应以热膨胀系数由表及里增大为原则。

Based on the analyses of temperature and stress distributions in ceramic tools,a model for designing graded compositional distribution and microstructure of ceramic tool materials was proposed.The residual compressive stress in the material surface layer in the fabrication during the cooling process was formed by adjusting the content of TiC0.7N0.3.In a micro scale,the material proper-ties could be improved by adding Si3N4 nano-particles.In a macro scale,the material properties could be improved by constructing a gradient structural model.A sialon–Si3N4 gradient ceramic nano-composite tool material was fabricated via the hot-pressing sintering.The results show that a typical duplex distribution due to the difference of Si3N4 grain sizes can give the higher bending strength/fracture toughness of the material and a residual compressive stress formed in the material surface layer.For the design of gradient ceramic tool materials,the thermal expansion coefficient could be increased gradually from the surface layer to the inner layer.