Microstructure and property of Ni-P-nano Al2O3 electroless plating layer produced on medium carbon steel treated by laser technology

Abstract

Uniform Ni-P-nano Al2O3 eletroless plating layer was produced on medium carbon steel, and scanned by high power continuous wave (CW) CO2 laser beam. Optical microscope (OM) and scanning electron microscopy (SEM) were used to observe the morphologies of the coating. X-ray diffraction (XRD) and X-ray energy dispersive spectroscopy (EDS) were employed to analyze the phase transformation and element compositions of the coating. The microhardness and abrasive resistance before and after laser processing were checked respectively. The whole coating was divided into four regions from surface to inner as laser strengthened region, transition zone, heat affected zone (HAZ) and substrate. The strengthened coating had good performances such as smooth surface, uniform components and refined microstructures. The phases in strengthened layer obviously changed from amorphous to crystalline and the main phase was Ni3P with some non-equilibrium phases. The reinforced particles, Al2O3, were homogeneously dispersed in grain boundary, which could improve the properties. The microhardness of strengthened region was about 3 times of substrate, and the abrasive resistance of which was also increased owing to the Al2O3 particles.Uniform Ni-P-nano Al2O3 eletroless plating layer was produced on medium carbon steel, and scanned by high power continuous wave (CW) CO2 laser beam. Optical microscope (OM) and scanning electron microscopy (SEM) were used to observe the morphologies of the coating. X-ray diffraction (XRD) and X-ray energy dispersive spectroscopy (EDS) were employed to analyze the phase transformation and element compositions of the coating. The microhardness and abrasive resistance before and after laser processing were checked respectively. The whole coating was divided into four regions from surface to inner as laser strengthened region, transition zone, heat affected zone (HAZ) and substrate. The strengthened coating had good performances such as smooth surface, uniform components and refined microstructures. The phases in strengthened layer obviously changed from amorphous to crystalline and the main phase was Ni3P with some non-equilibrium phases. The reinforced particles, Al2O3, were homogeneously dispersed in grain...