Boron carbide (B 4 C) coating having potential in application of cermet , armor materials, and wear-resistant components have attracted considerable attention due to its excellent properties, such as high melting point, high hardness, high neutron absorption, low density, and good chemical stability. In this study, the nano-B 4 C coatings have been successfully fabricated by the electrophoretic deposition (EPD) method in a solvent of isopropyl alcohol containing Polyethyleneimine (PEI). The electrophoretic B 4 C coating was sintered at 1000 °C for 6 h under a constant flow of argon. The electrophoretic coating was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, and the result indicates that B 4 C coating is of good film characteristics after sintering. Furthermore, the influence of addition amount of PEI on the EPD kinetics of the nano-B 4 C was investigated in detail. The results show that the optimal addition of PEI would vary with the suspension concentration of nano-B 4 C. Generally speaking, the needed addition amount of PEI for sufficiently modifying the surface charging of nano-B 4 C would increase with the amount of nanoparticles in suspension. This work demonstrates that EPD method is a facile and effective approach in the preparation of B 4 C coatings for potential applications.
Diamond/WC-Fe-Ni composite is a potential composition for impregnated diamond drill bits. It is necessary to avoid the graphitization of the diamond from Fe and Ni under the powder metallurgy process. Boron carbide (B 4 C) was coated on diamond, and diamond/WC-Fe-Ni composites were consolidated by hot pressing at different temperatures. The influences of sintering temperature and interfacial structure on bending strength and wear behavior were investigated. The bending strength for diamond/WC-Fe-Ni composite was dependent on matrix densification and interfacial graphitization. Un-coated diamond was eroded by Fe-Ni matrix and partially converted to graphite during the sintering process at all sintering temperatures. In opposite, B 4 C coating was beneficial to matrix densification at a lower sintering temperature, and delayed the appearance of graphitization to around 1300 °C. Therefore, the diamond/WC-Fe-Ni composites with B 4 C coating exhibited larger bending strength and better wear behavior at a relative low sintering temperature.
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