Microstructure and Property of Al₂O₃ and Al₂O₃/FeCrNi Coating Prepared on Ferritic/Martensitic Steel by Pulsed Laser Cladding

In order to improve the wear resistance of ferrite/Martensite steel in liquid lead bismuth environment, Al₂O₃ and Al₂O₃/FeCrNi coatings were successfully prepared on a typical ferritic/Martensitic steel by pulsed laser cladding, and the phase constitutions, compositions, microstructural characteristics and hardness of both the coatings were characterized and analyzed by jointly using X-ray diffraction, electron channeling contrast imaging, energy dispersive spectroscopy, electron backscatter diffraction and Vickers indenter. The results show that cladding zone (CZ) of the Al₂O₃ and the Al₂O₃/FeCrNi coatings are about 260 μm and 180 μm in depth, respectively. The part of the CZ near the Al₂O₃ coating surface is mainly consisting of bulk δ ferrite, while the part far away from the surface consists of martensitic plates. The CZ of Al₂O₃/FeCrNi coating has more uniform microstructures mainly comprised of martensitic plates. Hardnesses of the Al₂O₃ and the Al₂O₃/FeCrNi coatings are (363±75) HV and (467±17) HV, respectively, both of which are significantly higher than that of the substrate ((267±5) HV). Comprehensive analyses suggest that the higher hardness of Al₂O₃/FeCrNi coating can be attributed to grain refinement and second phase strengthening.