Microstructure and Corrosion Resistance of Ni-Based Laser-Cladded Coatings Reinforced with ZrC on Structural Steel

To mitigate the poor corrosion resistance of 45 steel components, ZrC-reinforced Ni-based composite coatings were fabricated on 45 steel substrates via laser cladding. The phase composition and microstructure were systematically characterized by XRD, FE-SEM, TEM, and EBSD, and the corrosion performance was evaluated by electrochemical measurements. The results show that the composite coatings consist of a dendritic γ-(Fe, Ni) matrix, interdendritic eutectics, and ZrC second-phase blocks or short dendrites. The volume fraction of ZrC increases with its addition content, while the ZrC grain size is first refined and then coarsened as the scanning velocity increases. IPF orientation analysis reveals that the γ-(Fe, Ni) phase exhibits a preferred <001> crystallographic orientation along the coating thickness direction. The coating with 30 wt% ZrC achieves the optimal corrosion resistance, with a corrosion current density of only 7.18% that of the substrate and a polarization resistance 13.34 times higher.