Abstract:Nickel-plated graphite particles and unmodified graphite particles with different contents were added to the Fe-based diamond composites. The basic properties of those specimens were measured, including relative density, hardness, bending strength, abrasion ratio and holding force coefficient. And also, SEM, XRD and EDS were used to carry out microstructure characterization, phase analysis and element distribution of these specimens. The results show that nickel plating effectively improves the surface wettability of graphite particles. And it is determined that an element diffusion zone is formed on the transition interface between the nickel-plated graphite and the matrix materials, effectively enhancing the interfacial bonding strength. Also, the pores and cracks in the matrix generated by adding the graphite particles are reduced after nickel plating. Thus, the loss of basic properties of the specimens is restrained. But it is found the higher the graphite content is, the weaker the positive effect of nickel plating is. In addition, it is revealed that nickel plating plays a conducive part in the formation of graphite lubricants on the working surface, and nickel-plated graphites can slow down the thermal corrosion of the diamond particles inside the high-temperature sintered specimens.

Key words: diamond composites; nickel-plated graphite; microstructure; mechanical properties; lubrication mechanism