| WCoB-TiC ceramic composites have the advantages of high hardness,wear resistance,high temperature resistance and fatigue resistance.It is a new type of hard material with low preparation cost and wide application prospect.However,the application of WCoB-TiC ceramic composites is limited for its low transverse rupture.Therefore,it is of great significance to enhance the strength and toughness of WCoB-TiC ceramic composites.This pape has reserched the influence of preparation process,composition design and the amount of silicon nitride whiskers on the microstructure and mechanical properties of WCoB-TiC composite ceramics.Firstly,the phase transformation and microstructure evolution of WCoB-TiC composite ceramics,and the effect of sintering temperature and holding time on microstructure and mechanical properties of WCoB-TiC composite ceramics were studied.The results show that: the liquid phase point of WCoB-TiC composite ceramic is 1208.2 °C.The microstructure is refined with the increase of sintering temperature.When the sintering temperature is 1400 °C and the holding time is 30 min,the WCoB-TiC composite ceramic has uniformly distributed small hard particles and has high densityas well as excellent overall performance.Secondly,the effects of Co content and W/B atomic ratio on the microstructure and mechanical properties of WCoB-TiC composite ceramics were studied.The results show that when the Co content is 19.6 wt% and the W/B atomic ratio is 0.5,the microstructure of WCoB-TiC composite ceramic samples is uniform and small,with high density and excellent overall performance.The hardness of the WCoB-TiC composite ceramic sample is HRA 91.8,bending strength is 851.3MPa,and fracture toughness K1C is 7.85MPa·m1/2.Finally,the effect of Si3N4 whiskers addition on the microstructure and mechanical properties of WCoB-TiC composite ceramics was studied.The resultsshow that the addition of a certain amount of Si3N4 whiskers can refine the microstructure of WCoB-TiC composite ceramics significantly increasing the bending strength and fracture toughness of WCoB-TiC composites.When the addition amount of Si3N4 whiskers is 0.6 wt%,the increase in bending strength and fracture toughness reach the maximum,i.e.1080.2 MPa and 9.86 MPa·m1/2,respectively;the fracture crack morphology analysis of the sample demonstrates that the toughening mechanism of Si3N4 whiskers is mainly crack deflection and whisker bridging. |
