Preparation And Properties Of TiCN Composite Ceramics

TiCN-based cermet cutting tool materials have many advantages,such as good chemical stability,low affinity with metals,strong resistance to bonding and diffusion,good surface quality,high red hardness,low friction coefficient,high corrosion resistance,high wear resistance,and good thermal conductivity.However,the additions of metal binding phases?nickel,molybdenum,and cobalt,etc.?in TiCN cermets makes them have poorer hardness,wear resistance,oxidation resistance and creep resistance compared to the ceramic cutting tools.In this project TiCN composite ceramics were prepared by the hot-press sintering technology using YAG,Al₂O₃,and a small amount of Ni as additives;the phase,microstructure and mechanical properties of the composite ceramic were investigated.Firstly,YAG-TiCN composite ceramics were prepared by the hot-pressing sintering process with YAG being additive.The phase,microstructure,density,and mechanical properties were characterized.The results showed that YAG as an additive significantly increased the density and mechanical properties of TiCN composite ceramics;YAG and TiCN did not react during the process of sintering;when the YAG content was 10%,the density of the composite ceramic material was up to 99.3%;furthermore,Vickers hardness,fracture toughness,and bending strength reached the maximum values of 20.48 GPa,7.27MPa·m^1/2,and 570.36 MPa,respectively.With YAG or YAG/Al₂O₃ as additive phase,YAG/Al₂O₃-TiCN composite ceramics were prepared at different temperatures?1 550?,1 600??by hot-press sintering.The results showed that YAG,Al₂O₃ and TiCN did not react during the sintering process.YAG/Al₂O₃ as an additive phase could increase the density of TiCN composite ceramics;the TiCN composite ceramic could reach nearly complete densification by adding 20%of YAG/Al₂O₃ at the sintering temperature of 1 550?;at 1600?,10%YAG/Al₂O₃ additives could achieve nearly complete densification of composite ceramics.Compared with YAG additive,at 1600?the YAG/Al₂O₃ additive have weaker effect on increasing the hardness,bending strength and fracture toughness of TiCN composite ceramics,but comparable effect on the promotion of the densification.The composite ceramics sintered at 1600?could obtain better mechanical properties,compared to that at 1 500?.With Ni and Ni/YAG as additive phase,Ni/YAG-TiCN composite ceramics were prepared at 1600?by the hot-press sintering.The results showed that YAG,Ni and TiCN did not react;With the increase of Ni content and the decrease of YAG content,the density and hardness of Ni/YAG-TiCN composite ceramics decreased,while the flexural strength increased.Moreover,the increased content of improved the Vickers hardness of composite ceramics and promoted the densification of composite ceramics.When the amount of Ni and of YAG was 7.5 and 2.5%,respectively,the composite ceramics had excellent mechanical properties;the flexural strength reached a maximum of 793.16 MPa,meanwhile,the density,fracture toughness,and Vickers hardness reached 98.65%and 6.70 MPa·m^1/2,18.57 GPa,respectively.