Effect of Cr_3C_2 Particles on Microstructure and Performance of Laser Cladding Ni-based Alloy Coating

Laser cladding Ni-based alloy coating(Ni50) and Ni-based composite coating with 30% Cr3C2 particles(Cr3C2/Ni) on low carbon steel substrate were obtained by laser cladding.Microstructures and the phase composition of the coatings were examined with optical microscope(OP),scanning electron microscope(SEM),energy dispersive X-ray analysis(EDS) and X-ray diffraction(XRD).Moreover,the microhardness and sliding wear resistance of the coatings were studied.It was found that the Ni50 coating is composed of many γ-Ni dendritic solid solution and eutectic structure(γ-Ni and Cr23C6) between the dendrites.The Cr3C2 addition can not only alter the solidification characteristic,but also refine microstructure of the Ni50 coating.Added Cr3C2 particles are mostly dissolved.The Cr3C2/Ni composite coating mainly consists of undissolved Cr3C2 particles,rich-chromium carbides with different shapes and fine dendrite and eutectic structure between the carbides.The main phases of the Ni50 coating are γ-Ni,Cr23C6 and Cr2B etc,the phases of Cr3C2/Ni composite coatings are γ-Ni,undissolved Cr3C2 and Cr7C3 etc.Microhardness and wear resistance of the Cr3C2/Ni composite coating are obviously improved compared with that of the Ni50 coating.