Synthesis Of (Ti,Nb,Mo,Me)(C,N) High-entropy Ceramic Powder And Its Ceramic Microstructure And Mechanical Properties

Ti(C,N)-based cermet,as an ideal substitute material for cemented carbide in the field of cutting tools,has the advantages of high red hardness and low cost.In order to improve the mechanical properties of cermet,the hard phase of cermet adopts Ti(C,N)-based solid solution.At present,there are few studies on high-entropy ceramics and high-entropy ceramic powders with multi-anion components.This paper preparedsingle-phase(Ti_0.2V_0.2Nb_0.2Mo_0.2W_0.2)(C_0.9N_0.1)and(Ti_0.2V_0.2Nb_0.2Ta_0.2Mo_0.2)(C_0.9N_0.1)high-entropy carbonitride powder.To explore the influence of the calcination process on the phase and morphology of the powder,and use the powder to prepare high-entropy ceramics and cermets,and explore the relationship between its structure and mechanical properties.Transition metal oxides can react with carbon to form transition metal carbides and nitrides in a nitrogen atmosphere.The thermodynamic calculation results show that Ti O₂,V₂O₅,Nb₂O₅,Ta₂O₅,Mo O₃,WO₃ can all react to form transition metal carbides and nitrogen at temperatures above 1400?.Nitrides can react with carbon to form carbides.The mixed raw material powder is calcined to obtain a solid solution through reaction and solid solution diffusion.Increasing the calcining temperature and holding time can promote the solid solution of the system.When the molar ratio of carbon powder to oxide powder in the raw material powder is reduced from 33:8and 32:7 to 30:8 and 30:7,the system configurational entropy increases,and(Ti_0.2V_0.2Nb_0.2Mo_0.2W_0.2)(C_0.9N_0.1)and(Ti_0.2V_0.2Nb_0.2Ta_0.2Mo_0.2)(C_0.9N_0.1)high-entropy carbonitride powders can be prepared at 1600?for 4h.(Ti,V,Nb,Ta,Mo)(C,N)and(Ti,V,Nb,Mo,W)(C,N)ceramics prepared by hot pressing and sintering can be densified at 1532?and 1700?respectively.The(Ti,V,Nb,Ta,Mo)(C,N)ceramics prepared at 1600°C and 1700°C have enriched areas of Nb,Ta,Mo,and(Ti,V,Nb,Ta,Mo)prepared at 1900°C have no obvious element segregation,and the density first increases and then decreases with the i ncrease of sintering temperature.(Ti,V,Nb,Mo,W)(C,N)ceramics with uniform distribution of transition metal elements can be prepared at 1700?,with a density of 98.01%.The hardness and fracture toughness of(Ti,V,Nb,Ta,Mo)(C,N)ceramics prepared at 1600?are the highest,and the measured values under 10kg are 20.7GPa and 4.87MPa·m^1/2.The(Ti,V,Nb,Mo,W)(C,N)-x Co cermet prepared by vacuum sintering at 1470?contains(Mo,W)_xC precipitated phase,and the(Mo,W)_xC phase decreases with the increase of the metal phase content.The density of the cermet prepared at 1370?is obviously improved.The content of(Mo,W)_xC precipitated phase in the(Ti,V,Nb,Mo,W)(C,N)-x Co system is more than that at 1470?,and also with the increase of metal phase content(Mo,W)_xC precipitation phase is reduced.There is element segregation in the ceramic phase of cermets prepared at two temperatures.The cermet prepared at 1370?has better performance,(Ti,V,Nb,Mo,W)(C,N)-25Co hardness and fracture toughness are 1401.4HV30 and 10.17MPa·m^1/2;(Ti,V,Nb,Ta,Mo)(C,N)-10Co is 1731.7HV30 and 7.32MPa·m^1/2.