Study On The Preparation And Properties Of B₄C/CaB₆ Ceramics

For the great properties such as low density, high hardness, well wear resistance and corrosion resistance, boron carbide is widely used in armor materials, cutting abrasive materials, acid erosion materials field. However, boron carbide is highly difficult to be sintered due to its strong covalent bond, resulting in its further limits of the application in industry.This paper doped 0～20wt.% CaB6 which has a lower density into B4C ceramics as an adding phase, and Al2O3 as a sintering aid,preparing B4C/CaB6 composite ceramics by hot pressed sintering. The density and hardness of B4C/CaB6 composite ceramics were studied to determine optimal content of CaB6. The seawater corrosion property and corrosion behavior of different B4C/CaB6 composite ceramics were researched by electrochemical analysis methods.The results showed that lightweight B4C/CaB6 composite ceramics could be prepared by hot pressed sintering at a temperature of 1900℃ and a pressure of 30MPa for 60 min.B4C/20wt.% CaB6 has the minimum density of composite ceramics, only 2.431g/cm3. Adding CaB6 can eliminate oxygen pollution of B4C powder, improve the B4C powder sintering activity, promote the densification of sintered B4C/CaB6 composite ceramics, The relative density of B4C/20wt.%CaB6 composite ceramic was the largest,up to 94.96%.With the addition of CaB6, the Vickers hardness of B4C/CaB6 composite ceramics decreased. The composite ceramic which didn’t add CaB6 obtained the hardness maximum for 38.65GPa; due to the hardness of the addition phase CaB6 lower than that of B4C,the more content of CaB6, the lower hardness of the composite was, resulting that the hardness of B4C/20wt% CaB6 composite ceramic reduced to. 36.01 GPa.B4C/CaB6 composite ceramics were mainly composed of B4C,CaB6, Al2O3 and AlB12C2 four phases. AlB12C2 was formed by the reaction between B4C and Al2O3 under the condition of high tempreture and high pressure. B4C/CaB6 composite ceramics achieved dense block.Fracture behavior belonged to brittle fracture, and the fracture mode was given priority to the intergranular fracture.In the process of the seawater immersion for 20 days,the mass losses of B4C/CaB6 composite ceramics and the falling range of their hardness were both rather little, showing that they had good resistance to seawater corrosion. When CaB6 contacted with seawater,faint electrochemical corrosion reaction would occurred. In addition, along with the increasing mass fraction of CaB6, the seawater corrosion resistance of B4C/CaB6 composite ceramics weakened gradually. But the corrosion precipitates would form a protective film on the surface,as a result, the corrosion rate would slow down,and the corrosion resistance of composite ceramics could be further improved.