Study On The Preparation And Properties Of Iron Matrix Composites Reinforced By B₄C Powders

Iron-based composites have a wide application background and application prospects.Boron carbide,as a modern material,has an excellent wear resistance,chemical resistance,and it has an excelllent potential application in space materials.Boron carbide was used to reinforce iron to get B₄C/Fe composites,which were well-performance.In this paper,B₄C/Fe composites were prepared by conventional sintering and hot pressing.DSC-TG was used to develop a reliable sintering process.X-ray diffraction（XRD）and scanning electron microscopy（SEM）were used to characterize the phase and microstructure of B₄C/Fe composites.The densification and mechanical properties of B₄C/Fe composites were obtained by high precision densimeter,Vickers hardometer and mechanical multimeter.The thermal diffusivity of the material was obtained by laser thermal conductivity detector and thermal dilatometer.The relationship between the composition,structure and properties of B₄C/Fe composites under different pressure and temperature were explored.The densification of B₄ C composites with conventional sintering is less than that with hot press sintering,and their mechanical properties and thermal properties are lower than those of hot pressing,too.At the sintering temperature of 900 ℃,the minimum porosity of B₄ C composites with conventional sintering was 16.45%.The hardness of B₄ C composites was correlated to B₄ C contents,the maximum hardness and flexural strength of B₄ C composites with conventional sintering was 1.09 GPa and 172.8 MPa,respective.The thermal diffusivity of the B₄ C composites had a downdraght with the increasing of B₄ C content,and it got its maximum value of 11.31 mm2 /s at the sintering temperature of 800 ℃.However,the sintering temperature and porosity of the hot press sintering showed a negative correlation with contrary to conventional sintering.The minimum porosity of the composite was only 0.53% while the sintering temperature at 1000 ℃.Hardness showed a positive correlation with B₄ C content under hot press.When the B₄ C content was 10 wt% and the sintering temperature was 1000 ℃,the hardness of the B₄C/Fe composites got its peak,and its value was 5.64 GPa.B₄ C composites got its optimum coefficient of thermal diffusion when the sintering temperature was 800 ℃ and its value was 12.38 mm2/s.B₄ C composites prepared by conventional sintering all had a high porosity,all of them is higher than 16%,and all of them didn’t complete the densification.What’s more,the B₄ C of composites prepared by conventional sintering broken down badly.Consideringly,B₄ C composites prepared by conventional sintering are inferior to the composites prepared by the hot press sintering under the same sintering condition.When the B₄ C content was 4 wt% and the sintering temperature was 1000 ℃,B₄C/Fe composite got a integrated performance,and its hardness,bending strength,porosity,coefficient of thermal diffusion and coefficient of thermal expansion（average of between 100 ℃ and 700℃）value was 3.61 GPa、328.3 MPa、4.63 %、9.80 mm2/s and 1.42*10-5 /K.Compared with conventional sintering,the hot-press sintering is more suitable for solid-phase sintering of B₄ C reinforced iron matrix composites.