Microstructure and performances of graphite scattered Cr3C2-NiCr composites prepared by laser processing

A Cr3C2-NiCr composite scattered with graphite (several microns in size) has been produced by laser processing of powder mixture of Cr/graphite/Ni. The composite has been investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and transmission electron microscope (TEM), and is found to be consisted of Cr3C2, gamma-NiCr and graphite. The composite contains many different microstructures including planar, dendrite, feathery eutectic and re-melt zones sprinkled with graphite. The mechanism of the laser synthesis processing is based on the dissolving mechanism of graphite, and the solidification of the laser melt is deduced as: L -> L+(Ni)-> L+(Cr3C2)+(Ni)->(Ni)+(Cr3C2) (C). The wear resistance of the composite is greatly improved due to the presence of the graphite. Whereas the corrosion resistance of the composite in a 0.2 M H2SO4 aqueous solution became worse than the same Cr content nickel alloy. (C) 2012 Elsevier B.V. All rights reserved.