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In this study, Mo2NiB2 coatings were prepared by the laser cladding technique and the relationship between coating microstructure and corrosion resistance with cladding power was analyzed. The results showed that Mo2NiB2 was reactively generated in all coatings while Mo2FeB2 and (Fe, Ni) were also present in the coatings due to dilution of the substrate. There was a good metallurgical bond between the coating and the substrate. The white cermet phase and black Fe-rich phase alternated within the coatings. As observed from the surface, the ceramic phase spreads out in a flattened shape and the black Fe-rich phase was present in a large number of pores. Due to the overdilution of the substrate, the volume of the ceramic phase decreased at a power of 800 W and the Fe content within the coating increased. The corrosion resistance of the coatings increased as the laser power increased from 500 to 700 W. Then the corrosion resistance of the coatings decreased at 800 W due to the excess Fe content and the decrease in the relative content of Mo2NiB2 and (Fe, Ni). Mo2NiB2 coating prepared at 700 W has the best corrosion resistance. [ABSTRACT FROM AUTHOR]

Ni–Al–Ti nanocomposite coatings were synthesized by electrodeposition. The tailoring role of Al and Ti particles in the co-deposition behaviors of nanocomposite coatings was comprehensively investigated by analyzing the time-dependent current density and electric field near the co-deposited particles. The results showed that the Al and Ti particles caused different co-deposition behaviors of Ni deposits, consequently bringing in the gradual increase in the surface dendritic structure, the refinement of grain sizes, and the decrease in the [200] fiber texture of the nanocomposite coatings with the decrease in the Al/Ti weight ratio. COMSOL simulations verified the different co-deposition mechanisms of Ni grains near the two kinds of particles, which was vitally determined by the different conditions of current density and electric field near the particles. The micro-hardness results revealed that the decreased Al/Ti weight ratio led to enhanced micro-hardness of the nanocomposite coating; in addition, the maximum hardness of the nanocomposite coating was 604.3 HV0.2 for an Al/Ti weight ratio of 1:4. Thus, the time-dependent current density and electric field near co-deposited Al and Ti particles determined the microstructure and property of the Ni–Al–Ti nanocomposite coatings. [ABSTRACT FROM AUTHOR]

In this work, FeCoCrNiMo0.2 high-entropy alloy coatings were fabricated using the atmospheric plasma spraying technique. The dependence of the microstructure and wear property of the coatings on spraying power was explored. The results showed that with increasing spraying power, the streamlined structure of the coating was gradually disturbed, the content of the oxides in the coating was enhanced, and the distribution of oxides became relatively uniform. Meanwhile, the porosity in the coating was reduced due to the increased melting degree of feeding particles. As the spraying power increased from 25.5 to 45 kW, the micro-hardness of the coating was improved from 438 ± 15.27 to 558.73 ± 7.23 HV0.2 and the wear loss of the coating decreased from 2.05 × 10−4 to 1.18 × 10−4 mm3/nm. The synergistic effect of the dispersive oxides and the reduced porosity could account for the enhanced micro-hardness by the second phase strengthening mechanisms. Subsequently, the wear resistance of the coating prepared at a high spraying power was improved due to the increased micro-hardness and the reduced crack behaviors. In addition, the broken oxides of metal elements, especially Cr oxides, during wearing led to the abrasive wear behavior, and the broken oxides could work as a lubricant to decrease the wear coefficient of the coating. Finally, the FeCoCrNiMo0.2 coating prepared at a power of 45 kW had the best wear resistance. [ABSTRACT FROM AUTHOR]