Investigation of Hardness, Morphology and Structural Analysis of NiCrBSi Composite Coating on Plain Carbon Steel

High velocity oxy-fuel (HVOF) is one of the emerging technologies among the thermal spraying techniques, for producing uniform and dense coatings, having high hardness and very low porosity. A NiCrBSi alloy coating was prepared with approximately 400µm thick, on the A516 steel by means of HVOF and was analyzed with regard to its detailed microstructures, phase formation, thickness, roughness and microhardness. The obtained coating was crack-free, mechanically bonded to the substrate and had very low porosity.  A microhardness tester was used so as to determine the mechanical properties of the coating. The microstructure of the coating and its phase transformations was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The major crystalline phases involve Cr3NiB6, Ni31Si12, Ni4B3, Ni3B compounds and Ni-γ solid solution. Also, amorphous phase was obtained in the coating. The results indicated that coating microhardness values were in the range of 700-800 Hv and a uniform distribution of different elements was observed.