梯度结构Al_2O_3-(W,Ti)C-TiN-Mo-Ni纳米金属陶瓷刀具材料的设计及制备

基于对高速硬切削时刀具应力和温度分布,以及刀具内部疲劳裂纹扩展仿真分析,提出一个组分含量分布和微观结构具有梯度特征的设计模型。通过韧性相的添加和梯度结构的引入,实现疲劳裂纹扩展速率的减缓,从而提高刀具寿命。采用二阶段热压烧结工艺制备出具有梯度结构的Al_2O_3-(W,Ti)C-TiN-Mo-Ni纳米复合刀具材料,并对其微观结构和力学性能进行研究。结果表明:所制备的梯度结构金属陶瓷材料表层硬度、内层的断裂韧度和抗弯强度分别达到19.258GPa,10.015MPa·m~(1/2)和1017.475MPa,满足高速硬切削刀具的性能要求。材料的断口出现韧窝和黏结相撕裂形成的断裂棱,有利于断裂韧度和抗弯强度的增强,从而提高刀具抗疲劳裂纹扩展能力。

Design and Fabrication of Al2O3-(W,Ti)C-TiN-Mo-Ni Nano-composite Cermet Tool Materials with Graded Structures

Based on the analysis on temperature and stress distributions ,as well as fatigue crack prop-agation in cutting tools ,a model for designing compositional distribution and microstructure with gra-ded characteristics was proposed .The addition of ductile phase and the introduction of the graded structure are beneficial to slow dow n the fatigue crack propagation rate and improve tool life .Al2 O3-(W ,Ti)C-TiN-Mo-Ni nano-composite tool material with graded structures was fabricated via two stage hot pressing sintering process ,and the microstructure and mechanical properties were studied . The results show that the surface hardness ,fracture toughness of inner layer and bending strength of the cermet with sintered gradient structure reach 19 .258GPa ,10 .015MPa · m1/2 and 1017 .475MPa , respectively .The performance requirements to cutting tools were met . The dimple cleavage and torn edge of the binding phase in the fracture surfaces can be beneficial to the improvement of the frac-ture toughness and bending strength ,so the resistance to fatigue crack propagation of tools is im-proved.