Preparation Of Ti（C,N）-TiB₂-HEA Composite Cermet Material And Microstructure And Properties Study

High-entropy alloy（HEA）has unique composition design and excellent performance.In recent years,it is a hotspot of material research and has broad application prospects.HEA is used as a binder for hard materials such as cermets and WC cemented carbides.It is expected that the characteristics will be used to improve the performance of hard materials,decrease the amount of Co,and reduce the cost of materials.In this study,Fe Co Ni Cr Al high entropy alloy is used as the binder,and Ti（C,N）-TiB₂-HEA composite cermet is prepared by vacuum hot pressing sintering method.Effects of TiB₂additive phase,HEA content,sintering temperature,and holding time on the microstructure and mechanical properties of Ti（C,N）-TiB₂-HEA composite cermet materials were studied.The influence of the HEA content on the high-temperature oxidation resistance,high-temperature hardness,and high-temperature friction and wear properties of composite cermets was investigated.The results show:When the HEA content is 10wt.%,with the increase of TiB₂content,the grain size of Ti（C,N）-TiB₂-HEA composite cermets decreases,and the density decreases.When the TiB₂content is 22.5 wt.%,with the increase of the binder content,the grain size of composite cermet first decreases and then increase,and the density increases.With the sintering temperature rising to 1500℃,the toughness of the composite material was the best,reaching 7.9 MPa·m^1/2.The hardness and strength were the best at 1550℃,which were 1977.3 HV₁₀and 768.6 MPa,respectively.When the sintering temperature is 1550℃,with the increase of the holding time,the properties of the material increase first and then decrease.The performance is optimal when the holding time is 30 minutes,and the hardness,strength and toughness are 1977.3 HV₁₀,768.6 MPa,and 7.2 MPa·m^1/2,respectively.The high thermal stability and oxidation resistance of HEA at high temperatures promote composite cermets to exhibit excellent oxidation resistance.At 1000℃,HEA binder composite cermets have significantly superior high-temperature oxidation resistance compared to Ni-Co.binder The former oxidation products are mainly metal oxides such as TiO₂,Al₂O₃and Al₂TiO₅,Al₂Ni O₄,Fe TiO₃,etc.And the oxide film is dense and the particles of the oxidation product are fine.The latter oxidation products are mainly TiO₂and a small amount of titanate.The oxidation product particles are coarse and cracks exist on the oxidation surface.HEA binder cermets have higher temperature hardness than Ni-Co binder composite cermets.When the temperature rises to 800℃,the high temperature hardness of the two is 1335.5 HV₂₀and 996 HV₂₀,respectively.HEA binder composite cermets have better high-temperature friction and wear performance than Ni-Co binder composite cermets.At 200℃,the wear mechanism of both is mainly abrasive wear.At 400℃,a small amount of oxidative wear gradually appeared.At 600℃,in addition to abrasive wear and oxidative wear,two binder composite cermets also showed a small amount of adhesive wear.With the temperature rising to 800℃,oxidative wear and adhesive wear are the main wear mechanism of the two composite cermets.