The Study On Preparation And Properties Of Bi-continuous Network Cr₃C₂-Cu Composites

A great deal of attention has been given to the development of the new continuous network cermet composites, in which the reinforcement (ceramic) and binder (metal) are three-dimensional continuous and interpenetrated. In this study, bi-continuous Cr3C2-Cu composites with various chemical components and micro-structures were successfully fabricated by metal infiltration process under protective atmosphere of hydrogen, in which porous Cr3C2were used as the ceramic preforms. The preparation processes and mechanical properties of the bi-continuous Cr3C2-Cu composites were studied and characterized to understand the effects of chemical component and micro-structure on mechanical properties. In addition, particle reinforced Cr3C2-Cu composites were prepared by powder metallurgy process as comparison. The electrical conductivities, friction wear and corrosion behavior of the bi-continuous and particle reinforced Cr3C2-Cu composites was studied. This work was beneficial to develop new functional and structure materials and predict the service safety of materials and guide the materials selection for engineering application.The investigation on preparation processes of the porous Cr3C2preforms show that various porous Cr3C2ceramics can be prepared by reducing Cr2O3in methane. When the sintering temperature increases from1000℃to1300℃, porosities of the porous Cr3C2are in the range of50-80%and the average pore sizes are increasing from0.5μm to3.5μm. When the sintering temperature is1100℃, the ceramic product has the highest porosity and the average pore size is around1μm. Yong’modulus of the porous Cr3C2decreases rapidly with the increase of the porosity, which can be described by the semi-empirical model E=E0(1-P/Pc)1/J.Bi-continuous Cr3C2-Cu composites can be fabricated by metal infiltration process using the porous Cr3C2as preforms. The Cr3C2-Cu composites products exhibit high densities and homogeneous micro-structures. Mechanical properties of the bi-continuous Cr3C2-Cu composites are not only affected by the volume fractions of chemical components, but also affected by the micro-structure of each phase. In the bi-continuous Cr3C2-Cu composites, Yong’s modulus and Vickers hardness generally increase with the increase of volume fraction of Cr3C2ceramic; Fracture toughness increases with the increase of volume fraction of Cu metal. When the ceramic/metal ratios are similar in bi-continuous Cr3C2-Cu composites, flexural strength decreases with the increase of average size of metal binder phase; tensile strength decrease with the increase of the porosity. The failed strain generally decreases with the increase of volume fraction of Cr3C2ceramic.In bi-continuous Cr3C2-Cu composites, the electrical conductivity decreases with the decreasing volume fraction of the copper phase. Cr3C2-Cu composites with interpenetrating network structures generally exhibit higher electrical conductivity than the particle reinforced Cr3C2-Cu metal matrix composite containing the same chemical composition. In bi-continuous Cr3C2-Cu composites, wear resistance increases as the volume fraction of the Cr3C2phase increases. Bi-continuous Cr3C2-Cu composites exhibit better wear resistance than the particle reinforced composites which comprise of the same Cr3C2fractions. The corrosion resistance of bi-continuous Cr3C2-Cu composites in3.5mass%NaCl solutions is better than particle reinforced Cr3C2-Cu composites.